marine engines application and installation guide...power is based on a 35 api [16 c (60 f)] fuel...

Marine Engines Applicationand Installation Guide

LEKM7142 Engine Performance & Boat Performance

LEKM7143 Driveline/Mounting/Alignment/Auxiliary

LEKM7144 Control Systems/Instrumentation andMonitoring Systems/Starting Systems/Start-up Systems/Serviceability

LEKM7145 Cooling Systems

LEKM7146 Ventilation & Exhaust System

LEKM7147 Lubrication Systems & Fuel Systems

LEKM7148 Dredge Engines

Materials and specifications are subject to change without notice. © 2000 Caterpillar Inc. Printed in U.S.A.

Marine EnginesApplication andInstallationGuide

● Engine Performance

● Boat Performance

LEKM7142-01 (Supersedes LEKM7142) (05-00)

Engine PerformanceApplication GuidelinesRatesPerformance Curve FormatEngine Configuration Effects on RatingsAuxiliary Engine Ratings

Application GuidelinesKnowledge of the engine’s operatingrequirements is essential to establish a propermatch of engine rating to boat operatingrequirements. To help determine theacceptability of a rating for a particular boat’sapplication, the following parameters shouldbe considered:

1. Time at full throttle 2. Annual operating hours 3. Propeller match

Time at Full ThrottleTime at full throttle is the amount of time theengine is operated at rated rpm without loadcycling during a normal duty cycle. This isnormally specified in terms of percent of totalcycle time or in minutes per hour.

Annual Operating Hours The annual operation hours are based on theaccumulated service meter units* during a 12-month period.

Propeller Match The propeller must be sized to allow theengine to operate slightly above rated rpmunder the boat’s most severe load conditions:full fuel and water tanks, stores aboard forextended voyaging, and adverse seaconditions.

RatingsRatings are statements of the engines’ powerand speed capability under specified loadconditions. The Caterpillar rating systemsimply matches engines to particularapplications. It consists of the followingstandard ratings.

Continuous A RatingFor heavy-duty service in ocean-goingdisplacement hulls such as freighters,tugboats, bottom-drag trawlers, and deep rivertowboats when the engine is operated at ratedload and speed up to 100% of the time withoutinterruption or load cycling. Expected usageshould be from 5000 to 8000 hours per year.

Medium Duty B RatingFor use in midwater and shrimp trawlers,purse seiners, crew and supply boats, ferryboats with trips longer than one hour, andtowboats in rivers where locks, sandbars,curves, or traffic dictate frequent slowing andengine load is constant with some cycling.Full power operation to be limited to 80% ofoperation time. Expected usage should befrom 3000 to 5000 hours per year.

Intermittent C RatingFor use in yachts with displacement hulls aswell as ferries with trips of less than one hour,fishing boats moving at higher speed out andback (e.g. lobster, crayfish, and tuna), andshort trip coastal freighters where engineload and speed are cyclical. Full poweroperation to be limited to 50% of operationtime. Expected usage should be from 2000 to4000 hours per year.

Patrol Craft D RatingContinuous power for use in patrol, customs,police, and some fire boats. Full power limitedto 16% of operation. Expected usage shouldbe from 1000 to 3000 hours per year.

High Performance E RatingFor use in pleasure craft with planing hulls aswell as for pilot, harbor patrol, andharbormaster boats. Full power operation to belimited to 8% of operation time. Expected usageshould be from 200 to 1000 hours per year.

Rating Conditions Ratings are based on SAE J1128/ISO 8665standard ambient conditions of 100 kPa (29.61 in. of Hg) and 25°C (77°F). Ratingsalso apply at AS1501, BS5514, DIN6271 andISO 3046/1 standard conditions of 100 kPa(29.61 in. of Hg), 27°C (81°F) and 60%relative humidity.

*Clock hours are the same as Service Meter Units on allCaterpillar Engines using electric service meters.Some Caterpillar Engines (D399, D398, D379 andearlier engines) used service meters which “counted”engine revolutions. One service meter unit on thoseengines, corresponds to a clock hour only when theengine is operating at rated speed (rpm). The ratiobetween clock hours and service meter units isproportional to engine speed.

1

Power is based on a 35° API [16°C (60°F)]fuel having a LHV of 42,780 kJ/kg (18,390 B/lb) used at 29°C (85°F) with adensity of 838.9 g/L (7.001 lb/U.S. gal).

Ratings are gross output ratings: i.e., totaloutput capability of the engine equipped withstandard accessories: lube oil, fuel oil andjacket water pumps. Power to drive auxiliariesmust be deducted from the gross output toarrive at the net power available for theexternal (flywheel) load. Typical auxiliariesinclude cooling fans, air compressors,charging alternators, marine gears, and seawater pumps.

Marine Engine Ratings to DIN Standards The DIN (Deutsche Industrie Norme) 6270Standard covers rated output data for internalcombustion engines in general applications.When required, DIN 6270 main propulsionratings can be quoted according to thefollowing stipulations.

Continuous Output A This is the published Caterpillar “Continuous‘A’ Rating” rating in kW units. No additionalreference is necessary*.

Output B Output B is defined as the maximum usefuloutput that the engine can deliver for adefinite time limit corresponding to theengine application. The fuel setting is pre-setsuch that output B cannot be exceeded, so nooverload capability need be demonstrated.

On the basis of this definition, we can offertwo output B ratings with kW valuescorresponding to Caterpillar’s Medium Duty BRating or Caterpillar’s Intermittent C Rating.

In each case, it is mandatory that reference bemade to the applicable rating definitions.

General Comments DIN 6270 conditions are slightly differentfrom the SAE conditions used in the U.S. Webelieve that they are virtually equivalent for allpractical purposes. No correction to ratingsshould be made to account for the slightlydifferent reference conditions.

Useful output as described under DIN 6270 isdefined as the output available to drive theload after suitable deductions are made forengine driven accessories. This is equivalentto the net rating. Caterpillar ratings indicategross output. At the kW requirement to drivesuch accessories as charging alternator andsea water pump are low and well within ourrating tolerance, no deductions for mainpropulsion engine driven accessory loadsneed to be made.

* A condition in the “Continuous Output A” definition isthat the output limiting device must be set to provide amargin of extra capacity. This overload capability canbe demonstrated, if required, by increasing the fuelsetting from the factory-set continuous output value tothe value corresponding to our “B” rating level. With afew exceptions, this increased fuel setting willcorrespond to an overload capability of approximately10%. The propeller should be sized for the continuousrating with the appropriate safety margins theTechnical Marketing Information File (TMI). The fuelsetting must be readjusted to the name-plate valueupon completion of the demonstration test.

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3

Engine Performance - MAR - C Rating 3406 DITA DM6120-00

En

gin

e P

ower

- b

kW

Fu

el R

ate

- L

/hr

Engine Speed - rpmE

ng

ine

Pow

er -

bh

p

Fu

el R

ate

- g

al/h

r

Engine Speed - rpm

ZONE LIMIT DATA ZONE LIMIT DATA

EngineSpeedrpm

PowerbkW

FuelConsg /

kW-hr

FuelRateL/hr

BoostPresskPa

Gauge

AirFlowcu m/min

ExhTempC

ExhFlowcu m/min

EngineSpeedrpm

Powerbhp

FuelConslb/

hp-hr

FuelRategal/hr

BoostPressin. Hg-Gauge

AirFlowcfm

ExhTempF

ExhFlowcfm

Curve 1 Curve 1 1800 1800 298 398 203 .33471.9 19.0934.8 276.722.9 809390 73553.6 1894 1600 1600 200 267 211 .34750.5 13.4453.9 134.415.4 544403 75936.8 1301 1400 1400 158 211 215 .35440.4 10.7264.2 78.211.8 417404 76128.3 1000 1200 1200 132 177 215 .35433.9 9.0179.6 53.29.4 332402 75722.3 788 1000 1000 110 147 218 .35928.6 7.6129.9 38.47.5 265405 76317.9 633

Curve 2 Curve 2 1800 1800 354 473 200 .32984.3 22.3122.3 36.226.5 937396 74662.3 2202 1600 1600 224 300 209 .34455.7 14.754.0 16.016.3 576420 79140.0 1414 1400 1400 171 229 214 .35243.6 11.530.5 9.012.2 431422 79530.0 1060 1200 1200 141 189 215 .35436.1 9.520.4 6.09.6 339421 79323.4 827 1000 1000 116 155 218 .35930.2 8.014.7 4.47.6 269424 79918.7 661

Curve 3 Curve 3 2100 2100 448 599 208 .342111.1 29.4201.3 59.640.9 1446344 64888.3 3121 1900 1900 447 598 206 .339109.7 29.0189.7 56.235.7 1262376 70882.2 2905 1700 1700 341 456 203 .33482.5 21.8111.0 32.923.9 845427 80458.6 2071 1500 1500 215 287 210 .34653.7 14.247.5 14.114.8 523445 83837.5 1325 1300 1300 169 226 214 .35243.0 11.429.0 8.611.1 392443 83528.4 1004 1100 1100 137 183 216 .35535.4 9.420.0 5.98.7 307444 83622.2 785

Curve 4 Curve 4 2100 2100 448 599 208 .342111.1 29.4201.3 59.640.9 1446344 64888.3 3121 1900 1900 447 598 206 .339109.7 29.0189.7 56.235.7 1262376 70882.2 2905 1700 1700 341 456 203 .33482.5 21.8111.0 32.923.9 845427 80458.6 2071 1500 1500 215 287 210 .34653.7 14.247.5 14.114.8 523445 83837.5 1325 1300 1300 169 226 214 .35243.0 11.429.0 8.611.1 392443 83528.4 1004 1100 1100 137 183 216 .35535.4 9.420.0 5.98.7 307444 83622.2 785

MAXIMUM POWER DATA MAXIMUM POWER DATA

EngineSpeedrpm

PowerbkW

FuelConsg /

kW-hr

FuelRateL/hr

BoostPresskPa

Gauge

AirFlowcu m/min

ExhTempC

ExhFlowcu m/min

EngineSpeedrpm

Powerbhp

FuelConslb/

hp-hr

FuelRategal/hr


AirFlowcfm

ExhTempF

ExhFlowcfm

2100 2100 448 599 208 .342111.1 29.4201.3 59.640.9 1446344 64888.3 3121 1900 1900 448 599 206 .339109.8 29.0189.7 56.235.7 1262376 70882.3 2909 1700 1700 448 599 203 .334108.3 28.6182.2 53.931.8 1124424 79977.6 2743 1500 1500 447 598 204 .336108.7 28.7162.7 48.226.3 930513 96673.4 2594 1300 1300 330 441 214 .35284.3 22.3105.2 31.118.0 636641 120856.9 2011 1100 1100 218 292 231 .38060.1 15.955.1 16.311.4 403627 118136.8 1301

PROPELLER DEMAND DATA PROPELLER DEMAND DATA

EngineSpeedrpm

PowerbkW

FuelConsg /

kW-hr

FuelRateL/hr

BoostPresskPa

Gauge

AirFlowcu m/min

ExhTempC

ExhFlowcu m/min

EngineSpeedrpm

Powerbhp

FuelConslb/

hp-hr

FuelRategal/hr


AirFlowcfm

ExhTempF

ExhFlowcfm

2100 2100 448 599 208 .342111.1 29.4201.3 59.640.9 1446344 64888.3 3121 1900 1900 331 443 203 .33480.1 21.2115.7 34.226.9 951370 69760.9 2152 1700 1700 237 317 208 .34258.7 15.563.3 18.718.3 647399 75243.4 1534 1500 1500 163 218 215 .35441.9 11.129.8 8.813.0 459397 74830.5 1078 1300 1300 106 142 221 .36427.9 7.412.0 3.69.7 343332 62520.5 725 1100 1100 64 86 228 .37517.5 4.63.3 1.07.5 265258 48613.8 488

Brake Mean Effective Pressure 239 kPa............................................................. Brake Mean Effective Pressure 35 kPa...............................................................Heat Rejection to Coolant (total) 1746 kW.......................................................... Heat Rejection to Coolant (total) 99293 kW........................................................

1

23,4

12

3,4

P P

MM

20

40

80

90

100

5

8

11

18

21

26

29

900 1100 1300 1500 1700 1900 2100 2300 2500

500

450

400

350

300

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200

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100

50

900 1100 1300 1500 1700 1900 2100 2300 2500

600

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24

Performance Curve FormatCaterpillar Performance Curves follow the following format:

Features of the Performance Curve:

Vertical Axis [left side] . . . Graduated inunits of Power [Brake kW or BrakeHorsepower]

Horizontal Axis . . . Graduated in units ofEngine Speed [Revolutions per Minute]

Curve P . . . Propeller Demand Curve,describes the power demanded by a fixedpitch propeller used in a displacement hull.Semi-displacement and planing hulls will havehigher load demand than shown in the "P"curve. Each semi-displacement and planinghull has different demand, which makes itimpossible to show the load demand for eachhull. Semi-displacement and planing hulls willneed to be sea trialed with fuel measurementstaken at different engine speeds to determineactual fuel and load demand.

Curve 1 . . . Continuous Limit Line, describesthe upper limit of continuous operation,without interruption or load cycling.

Zone 1-2 . . . Zone 1-2 is located between Curve1 and Curve 2. It is the zone within whichoperation is permitted for periods up to 4 hours,followed by a one hour period at combination ofpower and speed on or under Line 1.

Zone 2-3 . . . Zone 2-3 is located betweenCurve 2 and Curve 3. It is the zone withinwhich operation is permitted for periods up to1 hour, followed by a one hour period atcombinations of power and speed on or underLine 1.

Zone 3-4 . . . Zone 3-4 is located betweenCurve 3 and Curve 4. It is the zone withinwhich operation is permitted for periods up tofive (5) minutes, followed by a one hourperiod at combinations of power and speed onor under Line 1.

Curve 4…Maximum Limit Curve, themaximum power available within the ratingdevelopment limits (cylinder pressure, turbospeed, exhaust temperature).

Curve M…Maximum Power Data, themaximum power capability of the enginewithout regard to the rating development limits.

Fuel Rate Lines . . . Parallel, slightlycurving, dotted lines, with graduations ontheir right ends, are lines of constant fuel rate.[L/hr or gal/hr]

The most efficient engine rpm to generate anygiven amount of power will be found directlyunder the high point of the fuel rate linenearest the required power. This will be mostuseful in those applications which can varythe engine speed at which power is extracted,such as controllable pitch propellers.

The graphical representation of the engineperformance is accompanied by a full set oftabular information. Included is intakemanifold pressure, exhaust stack temperature,combustion air flow, exhaust gas flow, fuelrate, engine power and engine speed, and fuelefficiency for all the curves shown.

Each standard rating of the engines will haveits performance documented as shown above.There can be a delay of the formal version ofthe data in the case of new ratings or engineconfigurations.

Engine ConfigurationEffects on RatingsEngine configurations can be altered to allowefficient use of larger amounts of fuel. This isdone by increasing the amount of air whichcan be utilized in an engine. Air flow throughan engine is called aspiration. Caterpillarengines have one of the following methods ofaspiration:

Naturally Aspirated In a naturally aspirated engine, the volume ofair drawn into each cylinder is moderate,since only atmospheric pressure is forcing airthrough the cylinder’s intake valve. There isno pressurization of the engine’s intakemanifold by an external device and engineintake manifold pressure is always a partialvacuum.

4

Turbocharged Greater amounts of air can be forced into anengine’s cylinders by installing aturbocharger. Turbochargers are turbine-likedevices which use exhaust energy (whichnaturally aspirated engines waste) tocompress outside air and force it into theintake manifold. The increased amount of airflowing through turbocharged engines doestwo good things:

1. The greater flow of air cools the valves,piston crowns and cylinder walls, makingthem better able to resist the firing forces.

2. Fuel can be burned more efficiently, due tothe increased amount of air for combustion.

This makes the engine more powerful.Compression does increase the temperatureof the intake air, however. It is very useful toremove the heat-of-compression from theintake air, upstream of the combustionchambers. Cooling the air before it enters thecombustion chambers makes the air moredense and increases cooling of thecombustion chamber components.

Turbocharged/Aftercooled An air-cooling heat exchanger (aftercooler) isinstalled between the turbocharger and thecombustion chamber on Turbocharged/Aftercooled engines. The aftercooler cools theincoming air, carrying the heat away with aflow of water. The water can come from twosources. If jacket water (the same water that

cools the cylinder head and block) is used inthe aftercooler, then the air can only becooled to approximately 93°C (200°F). Jacketwater temperature is thermostaticallycontrolled at approximately 82°C (180°F).Even cooler air can be obtained by cooling theaftercooler with water from a separate circuit,such as sea water or some other circuit, withcolder water than the engine jacket water.Lower aftercooler water temperatures permithigher engine ratings because cooler, denserair permits burning more fuel.

Extended Periods of Low LoadProlonged low load operation should befollowed by periodic operation at higher loadto consume exhaust deposits. Low loadoperation is defined as below approximately20% load. The engine should be operatedabove 40% load periodically to consume theexhaust deposits. Caterpillar engines can berun well over 24 hours before exhaust slobberbecomes significant. The amount of additionaltime depends upon the engine configuration,water temperature to the aftercooler, inlet airtemperature to the engine and type of fuel.

Auxiliary Engine RatingsMarine engines used for auxiliary power areof the same general configuration aspropulsion engines. Their power output islimited by the same design factors.Horsepower ratings are also determined bythe type of aspiration, the aftercooling systemand by engine application.

Caterpillar prime power ratings are used formarine generator sets when applied as ship-board power and as emergency power at both60 Hz and 50 Hz. The engine is set at thefactory to provide 110% of rated output asrequired by Marine Classification Societies(MCS).

Normally, other auxiliary powerrequirements, such as hydraulic pumps,winches, fire and cargo pumps, andcompressors, are applied at a rating based ontheir duty cycle and load factor.

5

Boat PerformanceTolerances on Hull, Propeller and EnginePropeller SizingDucted Propellers (Kort Nozzles)Hull TypesRules of Thumb

The performance of the boat is the result of acomplex interaction of all three aspects of theinstallation; the engine, the hull, and thepropeller.

Tolerances on Hull,Propeller and EngineProper component sizing is very important tothe life and performance of the entirepropulsion system. There are tolerances inseveral aspects of the propulsion system. Inworst-case conditions, the result can be shortlife and/or unsatisfactory performance. Forexample: the effect of these tolerances isshown below in Figure 2.1:

The engine power may be expected to varydue to manufacturing tolerance by as much as3% on either side of its rated or 100% power.

The propeller power absorption may be asmuch as 5% higher, or lower, than originallyexpected. This could result frommanufacturing tolerance in pitch, surfacefinish, and blade profile.

The hull resistance may vary as much as 20%from calculated values or previous experiencedue to inevitable differences in weight andshape.

Propeller SizingThe propeller is as important as the hull orthe engine to the performance of the boat.

The propeller directly influences: top speed,fuel efficiency, and engine life.

General Information While many operators will choose to operateat reduced throttle settings while cruising, theengine must be able to reach its rated speed(rpm) when the boat is ready for sea; fullyloaded with fuel, water, and stores. For theultimate in engine life and economy, expectedengine operating speeds during sea trialsshould be approximately 1-3% over full loadrated engine speed (rpm).

Eliminating Engine Overloadingon Overwheeled Vessels When the engine speed (rpm) measuredduring the sea trial of a vessel fails to attainthe required sea trial speed, the reasongenerally is one of the following:

Excessive hull fouling — Solvable bycleaning the hull and re-running the sea trial.

Low engine power — Resolved bymeasuring and recording engine performanceparameters such as inlet, exhaust and fuelrate.

Incorrect transmission or propeller —A detailed discussion of the resolution of thiscondition follows: Simply, this discussion willbe restricted to fixed pitch propellers.

RatedSpeed(rpm)

Expected EngineSpeed During

Sea Trials(rpm)

280028002400240023002100192518001800

2830-28902830-28902425-24702425-24702320-23602120-21601945-19801820-18501820-1850

Table of Engine rpm at Sea Trials160Hull – Propeller – Engine

1501401301201101009080706050403020100

0 20 40 60 80 100 120Percent Design Hull Speed

Tolerances on Power

Per

cen

t E

ng

ine

Po

wer

(+20%)Hull

Demand(-10%)

PropellerMatchLine

Engine Power (53%)

Figure 2.1

(53%

)

9

Engine fuel setting adjustment — Manyvessel operators and shipyards want toincrease the engine fuel (rack) setting whentheir engine does not reach rated speedduring sea trials. At first glance, this seems tobe the easiest and least costly remedy.

However, in such a situation, this solution isincorrect, even if the engine speed (rpm) doesincrease to the expected rated rpm.Increasing the fuel (rack) setting will result inreduced engine life, increased wear, or inworst case, early engine failure. The vesseloperators engine repair and maintenancecosts will likely far exceed the cost ofreplacing or modifying the existingtransmission or propeller.

High idle adjustment — Another oftenconsidered alternative is increasing high idleengine speed to the specified free runningspeed. This will not provide the desiredresults since the fuel stop is already at themaximum fuel position, and an increase inhigh idle will not result in any appreciablespeed change.

Properly sized propeller and/orreduction ratio — The correct, but morecostly, remedy is to install a properly matchedpropeller and/or transmission ratio to allowthe engine to operate within it’s ratingguidelines.

Avoiding driveline component changes —There is another alternative which we willconsider in cases where driveline componentchanges cannot or will not be considered.This method consists of a reduction of boththe engine fuel setting and the high idlespeed. Of course, the engine power and ratedspeed are reduced in the process; however,we are taking advantage of the fact that thepropellers power demand drops off muchfaster than the engine power capability whenengine and propeller speed is reduced(referto Figure 2.2).

The net result is that the engine will performwithin its application limits and theengine/propeller match have been optimized.The following formula generally applies for astandard fixed pitch propeller:

or by rewriting the equation

Where: hp1 = Engine power produced at the fullthrottle speed recorded during the sea trial.This power level is determined by referring tothe appropriate marine engine performancecurve corresponding to the original enginerating sold by the dealer and reading thepower on the curve at the recorded speed.

hp2 = Calculated propeller power demand atthe new reduced engine speed (rpm)proposed for this application.

N1 = Engine speed (rpm) observed andrecorded during the original sea trial — priorto fuel setting and high idle modifications.(This speed should always be measured witha precision tachometer.)

N2 = New, reduced engine speed (rpm) whichmust be determined in order to provide anacceptable engine, transmission, and propellermatch.

hp2 = hp1 x3N2

N1

hp1=

3

hp2

N1

N2

300

2001300

Propeller hpDemand

hp Capability

1400 1500Engine Speed (rpm)

1600 1700 1800 1900

400

500

Marine Engine Performance Curve3412 TA (388 kw (520 hp) at 1800 rpm)

Figure 2.2

10

For example: Consider a 3408B DITA engine,sold at a continuous rating of 365 hp at 1800 rpm; During the sea trial, the maximumattainable engine speed was only 1620 rpm.This engine was operating in an unacceptableoverload (or lug) condition. The MarineEngine Performance Curve (for a continuousrating of 272 kw (365 hp) at 1800 rpm)indicates that the engine was producing (andthe propeller was demanding) 344 hp at thelimited speed of 1620 rpm. This powerrequirement exceeds the approved continuousrating of 330 hp at 1620 rpm. The solution isto further reduce the rpm until the approvedengine rating, as shown on the 3408B marineengine rating curve, exceeds the propellerdemand.

For this example we will calculate the powerrequired if the rated engine rpm was reducedto 1550.

Reducing the engine speed by 70 rpm hasresulted in a decrease in propeller demand of43 hp. The approved engine continuous ratingat 1550 rpm is 314 hp and the propellerdemand has been reduced to 301 hp.

At the initial trials, the recorded vessel speedwas 10.2 knots for this 21 m long seiner.Resetting the engine from 344 hp @ 1620 rpmto 314 hp @ 1550 rpm would decrease thevessel speed to 9.7 knots, a relativelyinsignificant difference, especially consideringthe gain in engine life.

Propeller Pitch Correction An overpitched propeller must have its pitchreduced to allow the engine to reach ratedrpm. The pitch must be reduced by anamount proportional to the engine rpm ratio.The following formula defines thisrelationship:

Where:P required = pitch the propeller must have toallow the engine to run at rated rpm

P present = pitch of the propeller which ispreventing the engine from reaching its ratedrpm

Engine rpm while overloaded = engine rpmunder normal working conditions whenequipped with the propeller whose pitch is toogreat

Rated Engine rpm = appropriate engine rpmfound on applicable engine specification sheet

Propeller Errors and PropellerMeasurement Fast boats need more precise propellers thanslow speed workboats.

Propeller pitch errors which would beinsignificant on a 10 knot river towboat, willcost a high speed patrolboat or yacht 2 or 3knots of its top speed.

Propellers on fast boats must be preciselymanufactured if design performance is to beattained and they must remain within nearlynew specifications to prevent severeperformance deterioration. This is particularlytrue of propellers’ leading and trailing edges.Tiny errors in profile, almost too small to bedetected by feel, can constitute sites forinitiation of cavitation. In severe cases, thiscan result in blade failure or loss after as littleas 24 hours of high speed running.

Most industry professionals can relateinstances where new propellers have beenfound to be several inches out of the specifiedpitch. When propellers are repaired orrepitched, it is even more difficult to restorethe necessary precision for highestperformance vessels.

The problem usually is the tooling. Mostpropeller pitch measurement machines cannot resolve or detect the small errors whichprevent a boat from attaining first-classperformance. All other things being equal, theskill of the propeller finishing machinist willmake the difference between barely-adequateand first-class boat performance.

P required = P present xEngine rpm while over loaded

Rated Engine rpm

hp2 = 334 x = 301 hp31550

1620

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Propeller Measurement Tools There are several basic types of toolscommonly used for propeller pitchmeasurement:

Swing Arm Type This machine generally consists of: a standwhich supports the propeller in a horizontalposition, a vertical column which passesthrough the center of the propeller’s hub, aswing arm which rotates around the verticalcolumn, and a vertical measuring rod whichcan slide in and out on the swing arm.

This machine reaches down from ahorizontally mounted swing arm and“touches” the blade at several radial locations,at some standard increments of angle. Thedifference in elevation, the radial position, andthe angular increment between readings allowpitch to be calculated between any twolocations. The accuracy of this device isrelated to the rigidity of the swing arm andthe degree of looseness in the requiredbearings. The potential accuracy of thepropellers measured will be directlyproportional to the number of measurementson each blade (places at which it toucheseach blade). For commercial (workboat)propellers, it is common to examine the bladeat six (6) to nine (9) places per blade. Onhigh-performance civilian propellers, it iscommon to examine each blade at twenty-five(25) to fifty (50) places while militarypropellers may be examined at severalhundred places per blade. The skill of the

machinist is applied in smoothing or “fairing”the areas between the measurements.

Pitch Blocks Pitch blocks are precisely shaped anvils,against which individual propeller blades arehammered to repair or correct their shape.

They can be used to measure propellers bycomparing the shape of an unknown propellerto a set of incremental pitch blocks until amatch is found.

Angle-Measuring Type Angle-Measuring Devices relate the angle of acircumferential line on the blade to ahorizontal reference plane and calculate thepitch from the angle and the radial position.

Caterpillar markets an angle-measuring pitchmeasuring tool—Part Number 8T5322.

Ducted Propellers(Kort Nozzles)The Propeller Duct, sometimes called a Kortnozzle is a ring, wrapped around a generallysquare-tipped, propeller. The ring has anairfoil-shaped cross section.

The ducted propeller is best used on vesselssuch as trawlers, tugs, and towboats withtowing speeds of 3-10 knots. Ductedpropellers should not be used on relativelyfast vessels.

To aid in selection, perform the followingcalculation. If the result is less than 30, theuse of the ducted propeller should not beconsidered as it may result in a net loss ofvessel performance.

Where: Bp = Basic Propeller Design Variable srpm = Propeller Shaft Speed (rpm) shp = Shaft Horsepower (shp) Va = Velocity of Advance of the Propeller

(knots) generally equals 0.7 to 0.9times boat speed

Bp = (srpm) ( shp )(Va)2.5

Figure 2.3

12

The nozzle configuration or profile most oftenused is a No. 19A nozzle although a No. 37specifically designed for backing isobtainable. Nozzles are made of mild steelwith a stainless steel liner to stand up toerosion. They may be mounted to steel, woodor fiberglass hulls.

A comparison of bollard pull ahead and asternfor the open water propeller versus the No. 19A (taken as 100% in ahead) and the No. 37 nozzle follows.

These are actual figures for a 1491 kW (2000 hp) installation with 2007 mm (79 inch)diameter propellers. A larger diameter openpropeller would show up somewhat better,though not as good as the nozzles.

More specific information on ducted propellersystems generally can be obtained frompropeller manufacturers, many of which alsomanufacture propeller ducts.

Hull TypesAll hull types discussed here refer only to theportion of the hull below the waterline. Whatis above the waterline concernsseaworthiness, seakindliness, stability,

comfort, and eye appeal, but has little impacton the propulsion machinery.

There are two basic types of hulls:Displacement Hulls and Planing Hulls. Thereare also some special types of hulls. Theseinclude the Semi-Displacement Hull,Catamaran, Wave-Piercing Catamaran,Hydrofoil, Surface Effects Ship (with bothflexible skirts and rigid sidewalls), and theSmall-Waterplane-Area-Twin-Hull (SWATH)Ship.

Displacement Hull A displacement hull can be described in mostbasic terms as a block, with tapered ends.

Displacement Hull’s Most Basic Form To illustrate the basic shapes this allows, fiveblocks in what are rearranged to form foursimple, but fundamental forms which covermost all displacement hull forms.

Keep in mind that this discussion concernsonly the portion of the hull below thewaterline and that the blocks represent onlythe submerged part of the hull.

When any one of the hulls shown abovemoves through the water, waves are formed.The bow pushes the water aside, forming abow wave. The momentum imparted to thewater carries it beyond the boundaries of the

1

1

2

2

3

3

45

12

34 5

12

34 5

12

34

4

5

5

Figure 2.5

Ahead Astern

Nozzle No. 19ANozzle No. 37Open Propeller(B4.70 Type)

59%82%55%

100%99%69%

Figure 2.4

13

hull, leaving a hollow behind it. The wavesurges back, into the hollow. At slow speeds,this causes the return surge to bounce off thehull, starting the familiar diverging pattern oftroughs and crests originating with the bowwave.

Relation of Hull Length to Boat Speed The length of a displacement hull determinesits eventual top speed. It is literally possible tomeasure the length of a displacement hull andcalculate its highest practical top speed basedon this measurement.

This is due to the relationship of boat speed,boat length and wave length.

Boat Length and Wave Length Wave length and wave speed are directlyproportional: the faster a wave, the longer itslength.

Since the movement of the hull causes thebow wave, the faster the hull moves, the fasterthe speed of the bow wave . . . and the longerits length.

As the boat increases its speed, the length ofthe bow wave will eventually approach thelength of the hull.

The speed at which the length of the bowwave equals the hull length is called the HullSpeed Limit.

Further increases in hull speed, beyond theHull Speed Limit will cause the stern of thehull to drop into the trough of the bow wave.

This has the following bad effects:

• air can enter the displacement hull’spropeller/s (reducing propeller thrust)

• the belly of the hull is exposed to theoncoming waves (increasing hullresistance)

• the increased incline of the propellershaft/s reduces the amount of shaft thrustfor forward motion (part of the forwardcomponent of propeller thrust is wasted inholding up the stern of the boat).

This greatly increases the hull’s resistance-to-further-speed-increase. To go faster, thedisplacement hull must climb the crest of its

own bow wave. For example, the last 10% of adisplacement hull’s top speed costs 27% of itsengine power (and fuel consumption).

Mathematical Representation of HullSpeed Ratio This relationship can be describedmathematically. It is called the Hull SpeedRatio.

When the bow wave length is equal to the hulllength, the speed length ratio formula can beexpressed as follows:

Planing Hull The planing hull skims over the surface of thewater with relatively little disturbance of thewater. The main resistance to planing hullspeed is the skin friction. Hulls of this typeare very sensitive to the smoothness of thehull, making good hull maintenance essentialfor top performance. Planing hulls are verysensitive to boat weight.

Semi-Displacement Hull The semi-displacement hull looks very muchlike the planing hull and is easily mistaken forthe planing hull. Semi-displacement hulls canbe described as having characteristics of bothplaning and displacement hulls, but are notone or the other.

Displacement hulls have trouble with speedlength ratios above 4.5 (1.34) due to their hullshape. The planing hulls have difficultiesbelow speed length ratios of approximately8.4 (2.5) because of their straight fore-and-aftlines.

Figure 2.6

4.5 (Hull Length meters) = (Boat Speed km/hr)

1.34 (Hull Length feet) = (Boat Speed knots)or

Hull Speed Ratio (SLR) = Boat SpeedHull Length

14

Semi-displacement hulls are designed tooperate well in this speed range.

Semi-displacement hulls are characterized bythe angle of the quarter-beam afterbodybuttock line. Visualize a pair of vertical,parallel planes intersecting the hull — midwayfrom the longitudinal center of the hull — tothe waterline at the side of the boat. Theintersection of the planes — with the bottomof the hull near the stern — form the quarter-beam afterbody buttock line (there are two,one on each side, but they have the sameshape). The angle of the quarter-beambuttock line is formed between it and a lineparallel to the at-rest waterline, fig. 2.8.

If the angle of the quarter-beam buttock lineis very small (less than 2 degrees), the hull iscapable of planing performance. At an angle of4 degrees, the limiting speed length ratio willbe around 2.0. An angle of 7 degrees will limitthe speed to speed length ratios of 1.5, or justabove displacement hull speeds. These anglesshould be measured relative to the hull’swaterline at rest.

Rules of ThumbPower to Reach Hull Speed A useful rule of thumb for vessels below100 tons displacement is:

Power to Reach Hull Speed horsepower = 5 x [Displacement long tons]

Fuel Consumption A useful rule of thumb for basic budgetarypurposes is:

Fuel Consumption = 1 Liter per hour per5 horsepower.

1/4 Beam Buttock

1/4 W.L. Beam

1/2 W.L. Beam

Measure This Angle

WL

CL

Figure 2.8

Figure 2.7

15


● Driveline

● Mounting and Alignment

● Auxiliary


DrivelineScrew Propeller DrivelinesJet DriveTorsional VibrationDriveline Couplings

Drivelines can be subdivided into two groups,depending on how the thrust forces drivingthe hull are created.

Screw propeller drivelines have a propellerconverting engine power to thrust outside thehull. The thrust forces are generated on thepropeller and transmitted to the hull throughthe propeller shafting and marinetransmission. *

Jet drives have engine driven water pumps,either within the hull or bolted rigidly to it,which accelerate large flows of water. Thethrust of the water leaving the pump propelsthe hull. The thrust forces are applied to thehull through the pump housing.

Screw PropellerDrivelinesThere are several ways screw propellerdrivelines connect the engine to the propeller.

Conventional In-Line PropellerSystemsIn conventional in-line propeller systems, thepropeller shafting is straight, rigid andtransmits the propeller thrust in a direct linefrom the marine gear output flange to thepropeller. The engine(s) is/are located low,near the longitudinal center of the hull, andthe marine gear(s) generally accepts the fullpropeller thrust.

Shaft Diameter and Bearing SpacingSelectionTo prevent premature damage to shaftbearings, the shaft bearings should be closeenough to prevent shaft whip, but far enough

*Boats with ducted propellers (Kort nozzles) receive aportion of their thrust directly from the hydrodynamicforces on the ducts. Ducted propellers are notcommon on fast boats due to the high drag ofpropeller ducts at high boat speeds.

1

DRIVELINE COMPONENTS – CENTERLINE MOUNTED THROUGH STERN POST

1. Shaft companion flange2. Intermediate shaft3. Shaft bearing – pillow block, expansion type4. Flange type shaft coupling5. Tail shaft

6. Stuffing box – may or may not contain bearing7. Stern tube – one end threaded, the other slip fit8. Stern bearing9. Propeller 10. Retaining nut

9

10 8 7 65

4 32 1

Figure 1.1

apart to permit the shaft to conform to thehull’s flexing. For this reason, shafting shouldbe designed for the thrust and torque forcesapplied. Since the tail shaft is more subject todamage from a propeller’s contact withsubmerged objects, it should

be strengthened for this purpose. Thefollowing nomograms will serve as a guide forshaft sizes and bearing spacing for commonlyused shaft materials consistent with goodmarine practice.

2

2

5

10

20

50

100

200

500

1000

1

1.5

2

2.5

3

4

5

6

7

8

910

Shaft Diameter(inches)

Tailshafts for heavy duty serviceshould be increased by adding 1%of the propeller diameter to thebasic shaft diameter.

Intermediate shafts may be reduced to.95 of the resultant shaft sizes.

Mild steel, read directly.Tobin bronze, multiply by 1.05.Monel, multiply by 0.88.

Example 2

ConditionSelect steel intermediate shaft and bronzetailshaft for heavy duty service. Enginedevelops 300 continuous hp@ 1800 rpm.Reduction ratio, 4.5:1. Propeller diameter,54 inches.

SolutionContinuous hp = 300

Propeller rpm = 1800 = 400

hp per 100 rpm = 300 = 75

Basic shaft diameter = 3.64 in.Steel intermediate shaft = 3.64 x 0.95 = 3.46 in.Bronze tailshaft = (3.64 x 1.05) + (54 x .01) = 3.82 + 0.54 = 4.36 in.

Horsepower per 100 rpm Propeller Speed

Example 1

ConditionSelect bronze propeller shaft for engine withIntermittent rating of 315 hp @ 2000. Reductionratio, 2:1. Propeller diameter, 32 inches. Lightduty operation.

SolutionIntermittent hp = 315

Propeller rpm = 2000 = 1000

hp per 100 rpm = 315 = 31.5

Basic shaft diameter = 2.75 in.Bronze shaft diameter = 2.75 x 1.05 = 2.88 in.

NOTE: Round off shaft diameter to nearest larger standard size.

————

———— 4.5

4.0010.00

2

SHAFT DIAMETER SELECTION NOMOGRAPHFigure 1.2

Location of first shaft bearing aft ofthe marine transmissionThe location of the first line shaft bearingfrom the marine transmission flange isextremely important.

To avoid inducing unwanted forces on themarine transmission thrust bearing, the lineshaft bearing should be located at least 12,and preferably 20, or more shaft diametersfrom the marine transmission output flange. Ifthe bearing must be located closer than 12 diameters, the alignment tolerances mustbe reduced substantially and the use of aflexible coupling considered.

Vee DrivesIn Vee Drives, the propeller shafting is in twosections. The first section of shafting is fromthe propeller to a Vee drive unit.

The Vee drive unit is a bevel-gear box whichallows the shafting to change directions. TheVee drive unit accepts full propeller thrust,transmitting the thrust to the hull through itsmounting feet.

The second section of shafting turns sharplybackward from the Vee drive unit to theengine. The engine is generally mounted asfar to the rear of the boat as possible, with itsflywheel end facing toward the bow of theboat.

3

5000

4000

3000

2000

1000

0 1

2

3

4

5

10

BEARING SPACING

20

30

40

20

15

10

9

8

7

6

5Phos. Bz

Steel

Monel400

Max

imu

m S

pac

ing

of

Bea

rin

gs

in F

eet

Mo

du

lus

of

Ela

stic

ity

Sh

aft

Dia

met

er in

Inch

es

Pro

pel

ler

Rev

olu

tio

ns

Per

Min

ute

Space bearings — rule a line from shaft insecond line scale to modulus in fourth scale(26 for Monel). Then rule a line from point of

intersection on center scale to connectpropeller rpm on left scale and extend the lineto right scale.

"Monel" is a registered trademark ofInternational Nickel Corp.

Chart published courtesy of Paul G. Tomalin

Figure 1.3

There are a number of advantages of the Veedrive layout:The engine is located at the extreme rear ofthe boat, taking minimal usable space withinthe hull.

Because the shafting between the engine andthe Vee drive unit is not loaded with propellerthrust forces, that section of shaft can includeuniversal joints or other soft couplings. Thedriveline softness allows use of soft enginemounts, resulting in a very quiet installation.

Disadvantage of the Vee drive arrangement:The engine center of gravity is relatively high.It is further aft than conventional inlinedrivelines. This reduces stability andadversely affects hull balance.

Z DriveThe Z drive is a drive arrangement where theengine is connected to a right angle gear unit.A vertical drive shaft leads down through thehull to a submerged, second right angle gearunit. The lower right angle gear drives thepropeller through a short length of horizontaldrive shaft. The engine may face either foreor aft. Transverse engine orientations are notrecommended.*

*The rolling of the boat can shorten the life of thecrankshaft thrust bearings. When the boat rolls, thecrankshaft will slide back and forth, hammering on itsthrust bearings. If the engine is running, the motionwill be dampened by the engine’s oil film. If the engineis not running, the oil film is not present to protect thethrust bearing.

4

Figure 1.4 Vee Drive

Stern DrivesThe stern drive is a drive arrangementwherein the engine is connected to areverse-reduction unit (to provide the

reversing capability) which drives two rightangle gear sets (through a double universaljoining shaft) and a propeller. The engineflywheel faces aft.

5

Figure 1.5 Stern Drive

Figure 1.6

Jet DriveDefinition of Jet DriveThe boat is propelled by the acceleration of aflow of water, picked up from the bottom ofthe hull through an inlet grill and forced outthrough a nozzle mounted in the stern of theboat. The water flow is powered by an enginedriven pump. The pump impeller is driventhrough a clutched reduction unit or directfrom the engine flywheel to a universal jointshaft.

Advantages of Jet Drive• There is no need for a reverse gear.

Reverse mode of operation can beaccomplished by means of buckets orvanes on the discharge nozzle, whichredirect the jet’s discharge stream forwardinstead of aft.

• Operation in water too shallow forconventional propeller systems is possible.

Engine load with jet drives normally follow acubic demand. Jet drive systems aresignificantly less prone to overload, since jetpower demand is not very sensitive to vesselspeed. Jet Drive units are less prone todamage from floating debris.

Disadvantages of Jet DrivesDisadvantages of the Jet Drive arrangementinclude:

• Block loading of the engine if the boatcomes off the water ingesting air and lossof load. When the boat comes back in thewater, block loading can occur if theengine speed is not matched to the load.

• A tendency to plug the inlet grill withdebris. Some jet propulsion units areequipped with built-in cleaningmechanisms.

Torsional VibrationDefinitionTorsional vibration is cyclic irregularity ofrotation in a shafting system. It is caused byengine combustion pulses, reciprocatingmotion and the propeller. As shafts in thesystem rotate, both the input torque (as eachcylinder fires) and the resistance to rotation(caused by the propeller) varies. The torquevariation is natural and unavoidable. It is onlydangerous when uncontrolled.

Any shaft rotating with a mass attached toeach end is capable of torsional vibration ifthere is any irregularity in the rotation ofeither mass. Rotation originates with thepower stroke of the piston.

Figure 1.7 Jet Drive

6

The simplified drivetrain below illustrates therelationship of shaft diameter, length andinertia of the natural frequency of the system.

Sources of Torsional VibrationMany components in the driveline can causeor contribute to torsional vibration:

• Irregularity in the flow of water to apropeller caused by struts, appendages,hull clearance

• Propeller blade-to-blade pitch inaccuracies• The intermeshing of gear teeth in the

marine transmission• Misaligned flexible couplings• Universal joints (except for constant

velocity types)• Firing of individual cylinders of the engine• Auxiliary loads driven from any of the

engine’s power takeoffs

Mathematical TorsionalVibration AnalysisTo ensure the compatibility of an engine andthe drive equipment, a theoretical TorsionalVibration Analysis (TVA) is necessary.Disregarding the torsional compatibility of theengine and driven equipment, can result inextensive and costly damage to componentsin the drive train or engine failure. Thetorsional report will show the naturalfrequencies, the significant resonant speeds,and either the relative amplitudes or atheoretical determination of whether themaximum permissible stress level isexceeded. Also shown are the approximatenodal locations in the shafting system for eachsignificant natural frequency.

Conducted at the design stage of a project,the mathematical torsional analysis mayreveal torsional vibration problems which canbe avoided by modification of drivenequipment, shafts, masses or couplings.

Data Required to PerformMathematical Torsional AnalysisThe following technical data is required toperform a torsional analysis:

1. Operating speed ranges—lowest speed tohighest speed, and whether it is variableor constant speed operation.

2. Load curve on some types of installationsfor application with a load dependentvariable stiffness coupling.

3. With driven equipment on both ends ofthe engine, the horsepower requirementof each set of equipment is required andwhether operation at the same time willoccur.

4. A general sketch of the complete systemshowing the relative location of each pieceof equipment and type of connection.

5. Identification of all couplings by make andmodel, along with WR2* and torsionalrigidity.

6. WR2 or principal dimensions of eachrotating mass and location of mass onattached shaft.

7. Torsional rigidity and minimum shaftdiameter, or detailed dimensions of allshafting in the driven system, whetherseparately mounted or installed in ahousing.

*WR2 is a Polar Moment of inertia. It is the way wequantify the tendency of an object to resist changingits rotational speed. A flywheel is an object specificallydesigned to have a high polar moment of inertia. If itsmetal were concentrated near its hub, it would have amuch lower polar moment of inertia, yet would havethe same weight.

7

Figure 1.8

8

8. If a reciprocating compressor is utilized, aharmonic analysis of the compressortorque curve under various loadconditions is required. If this is notavailable, then a torque curve of thecompressor under each load condition isrequired. The WR2 of the availableflywheels for the compressor should besubmitted

9. The ratio of the speed reducer orincreaser is required. The WR2 andrigidity that is submitted for a speedreducer or increaser should state whetheror not they have been adjusted by thespeed ratio squared

10. The WR2 and number of blades on thepropeller.

Availability of Torsion Characteristicsof Caterpillar-Furnished EquipmentUpon request, mass elastic systems of itemsfurnished by Caterpillar will be supplied to thecustomer without charge so that he cancalculate the theoretical Torsional VibrationAnalysis.

Mass elastic data for Caterpillar DieselEngines, marine gears and generators iscovered in the Technical Information System(TIS) and in Technical Marketing Information(TMI). If desired, Caterpillar will performtorsional vibration analyses. The data requiredprior to the analysis is described above. Thereis a nominal charge when this service isprovided by Caterpillar.

Timing of Mathematical TorsionalVibration AnalysisThe best time to perform a MathematicalTorsional Vibration Analysis is during thedesign phase of a project; before the drivelinecomponents are purchased and while thedesign can be easily changed if the TVAshows problems are likely to exist.

Responsibility for TorsionalCompatibilitySince compatibility of the installation is thesystem designer’s responsibility; it is also hisresponsibility to obtain the torsional vibrationanalysis.

Driveline CouplingsThere are two types of driveline couplings:Rigid and soft couplings.

Rigid CouplingsRigid shaft couplings may be classified by themethod of attaching the shaft to the coupling.

Society of Automotive Engineers(SAE) Standards—SAE J755Use of SAE standard shaft ends and couplingsis recommended. They represent the higheststandards of rigidity and reliability.

Other Rigid CouplingsThe couplings using SAE standard shaft endsand hubs are cumbersome to remove andmust be machined very carefully, to ensureconcentricity and perpendicularity tolerancesare met. The following couplings are easier toinstall and remove. They are also simpler tomanufacture.

Q-Cotter Pin

L J

E

X MIN

A

T

N

W

F-Thd

igure 1.9

1 32/ "x45

PDrill

H

G

M K B D Y

CY

A

R rad

Sec Y-Y

Figure 1.10

Figure 1.9

Figure 1.10

9

Dimensions for Shafts 3/4 to 6 inch in Diameter

Non ShaftDiameter

"A"

.75

.88

1.00

1.13

1.25

1.38

1.50

1.75

2.00

2.25

2.50

2.75

3.00

3.25

3.50

3.75

4.00

4.50

5.00

5.50

*6.00

*6.50

*7.00

*7.50

*8.00

.624

.726

.827

.929

1.030

1.132

1.233

1.437

1.640

1.843

2.046

2.257

2.460

2.663

2.866

3.069

3.272

3.827

4.249

4.671

4.791

5.187

5.582

5.978

6.374

.626

.728

.829

.931

1.032

1.134

1.235

1.439

1.642

1.845

2.048

2.259

2.462

2.665

2.868

3.071

3.274

3.829

4.251

4.673

4.793

5.189

5.584

5.980

6.376

2.00

2.38

3.75

3.13

3.50

3.88

4.25

5.00

5.75

6.50

7.25

7.88

8.63

9.38

10.25

10.88

11.63

10.75

12.00

13.25

14.50

15.75

17.00

18.25

19.50

.19

.25

.25

.25

.31

.31

.38

.44

.50

.56

.63

.63

.75

.75

.88

.88

1.00

1.13

1.25

1.25

1.38

1.38

1.50

1.50

1.75

.1865

.249

.249

.249

.3115

.3115

.374

.4365

.499

.561

.6235

.6235

.7485

.7485

.8735

.8735

.9985

1.123

1.248

1.248

1.373

1.373

1.498

1.498

1.748

.1875

.250

.250

.250

.3125

.3125

.375

.4375

.500

.5625

.625

.625

.750

.750

.875

.875

1.000

1.125

1.250

1.250

1.375

1.375

0.500

1.500

1.750

Small EndDiameter

"B"

Taper LengthDiameter

"C"

Keyway WidthDiameter

"D"

1.063

1.250

1.438

1.438

1.625

1.813

2.000

2.250

2.625

3.000

3.000

3.500

3.875

4.375

4.375

4.750

5.125

5.625

6.375

6.750

7.500

8.250

9.000

9.375

9.750

Taper Endto Thread"G" End

.031

.031

.031

.031

.063

.063

.063

.063

.063

.094

.094

.094

.094

.125

.125

.125

.125

.156

.188

.188

.219

.219

.250

.250

.250

KeywayFillet Radius

"R"

Min Max

.50

.63

.75

.75

.88

1.00

1.13

1.25

1.50

1.75

1.75

2.00

2.33

2.50

2.50

2.75

3.00

3.25

3.75

4.00

4.25

4.50

5.00

5.25

5.75

13.0

11.0

10.0

10.0

9.0

8.0

7.0

7.0

6.0

5.0

5.0

4.5

4.5

4.0

4.0

4.0

4.0

4.0

4.0

4.0

4.0

4.0

4.0

4.0

4.0

Thread"F"

Dia TPINom Min Max

.10

.13

.13

.13

.16

.16

.19

.22

.25

.28

.31

.31

.31

.31

.31

.31

.31

.38

.44

.44

.50

.50

.56

.56

.56

.095

.125

.125

.125

.157

.157

.189

.219

.251

.281

.312

.313

.311

.311

.310

.310

.309

.373

.434

.435

.493

.494

.555

.556

.553

.097

.127

.127

.127

.160

.160

.192

.222

.254

.284

.315

.316

.314

.314

.313

.313

.312

.376

.437

.438

.496

.497

.558

.559

.556

Keyway SideDiameter

"E"

Nom Min Max

*6 in. through 8 in. bore uses 1 in./ft taper. 1/12 in. per taper. Angle with centerline 2° 23 ft 9 in.

10

Dimensions for Shafts 3/4 to 6 inch in Diameter

Non ShaftDiameter

"A"

.75

.88

1.00

1.13

1.25

1.38

1.50

1.75

2.00

2.25

2.50

2.75

3.00

3.25

3.50

3.75

4.00

4.50

5.00

5.50

*6.00

*6.50

*7.00

*7.50

*8.00

.500 - 13

.625 - 11

.750 - 10

.750 - 10

.875 - 9

1.000 - 8

1.125 - 7

1.250 - 7

1.500 - 6

1.750 - 5

1.750 - 5

2.000 - 4.5

2.250 - 4.5

2.500 - 4

2.500 - 4

2.750 - 4

3.000 - 4

3.250 - 4

3.750 - 4

4.000 - 4

4.250 - 4

4.500 - 4

5.000 - 4

5.500 - 4

5.750 - 4

.500

.625

.750

.750

.875

1.000

1.125

1.250

1.500

1.750

1.750

2.000

2.250

2.500

2.500

2.750

3.000

3.250

3.750

4.000

4.250

9.500

5.000

5.500

5.750

.313

.375

.438

.438

.500

.563

.625

.750

.875

1.000

1.000

1.125

1.250

1.500

1.500

1.625

1.750

1.875

2.125

2.250

2.250

2.500

2.750

3.000

3.125

Size

*6 in. through 8 in. bore uses 1 in./ft taper. 1/12 in. per taper. Angle with centerline 2° 23 ft 9 in.

1.313

1.500

1.750

1.750

2.719

2.250

2.438

2.750

3.125

3.500

3.500

4.000

4.375

5.125

5.125

5.500

5.875

6.375

7.125

7.750

8.500

9.250

10.000

10.375

10.750

ExtensionBeyond

Taper "H"

.375

.438

.500

.500

.375

.750

.875

1.000

1.250

1.375

1.438

1.688

1.938

2.125

2.125

2.375

2.500

2.750

3.250

3.500

3.875

4.375

4.375

5.125

5.375

Diameterof Pin

End "L"

.250

.250

.313

.313

1.000

.875

.875

.500

.500

.500

.500

.500

.500

.750

.750

.750

.750

.750

.750

1.000

1.000

1.000

1.000

1.000

1.000

Lengthof Pin

End "M"

1.500

1.781

2.125

2.125

2.813

3.188

3.500

4.219

4.938

5.625

6.094

6.656

7.344

8.500

9.250

10.000

10.500

9.625

10.875

12.125

13.250

14.375

15.625

16.875

18.125

KeywayLength

"X"

.391

.484

.594

.594

.125

.813

.906

1.031

1.250

1.375

1.438

1.688

1.938

2.125

2.125

2.375

2.500

2.750

3.250

3.500

3.875

4.375

4.875

5.125

5.375

.125

.125

.125

.125

.625

.125

.188

.188

.188

.188

.188

.250

.250

.375

.375

.375

.375

.375

.375

.500

.500

.500

.500

.500

.500

Undercut

"J" "K"

1.141

1.328

1.516

1.516

.719

1.906

2.094

2.359

2.734

3.141

3.141

3.641

4.016

4.578

4.578

4.953

5.328

—

—

—

—

—

—

—

—

.141

.141

.141

.141

.172

.172

.172

.203

.203

.266

.266

.266

.266

.375

.375

.375

.375

—

—

—

—

—

—

—

—

CotterPin

Hole

"N""P"

Drill

.125

.125

.125

.125

.156

.156

.156

.188

.188

.250

.250

.250

.250

.375

.375

.375

.375

—

—

—

—

—

—

—

—

.75

.75

1.00

1.00

1.25

1.50

1.50

1.75

2.00

2.25

2.25

2.50

3.00

3.00

3.00

3.50

3.50

—

—

—

—

—

—

—

—

CotterPin"Q"

LengthNomDia

PlainThick "T"

JambThick "W"

Nuts

11

Marine Propeller Hub Bore Dimensions

Nom BoreDiameter

.75

.88

1.00

1.13

1.25

1.38

1.50

1.75

2.00

2.25

2.50

2.75

3.00

3.25

3.50

3.75

4.00

4.50

5.00

5.50

6.00

6.50

7.00

7.50

8.00

Nom Min Max

2.250

2.625

3.000

3.375

3.750

4.125

4.500

5.250

6.000

6.750

7.500

8.250

9.000

9.750

10.500

11.250

12.000

11.250

12.500

13.750

15.000

16.250

17.500

18.750

20.000

.188

.250

.250

.250

.313

.313

.375

.438

.500

.563

.625

.625

.750

.750

.875

.875

1.000

1.125

1.250

1.250

1.375

1.375

1.500

1.500

1.750

.1865

.249

.249

.249

.3115

.3115

.374

.4365

.499

.561

.6235

.6235

.7485

.7485

.8735

.8735

.9985

1.123

1.248

1.248

1.373

1.373

1.498

1.498

1.748

.1875

.250

.250

.250

.3125

.3125

.375

.4375

.500

.5625

.625

.625

.750

.750

.875

.875

1.000

1.125

1.250

1.250

1.375

1.375

1.500

1.500

1.750

MaximumLength

"B"

.608

.710

.811

.913

1.015

1.116

1.218

1.421

1.624

1.827

2.030

2.233

2.437

2.640

2.843

3.046

3.249

3.796

4.218

4.640

4.749

5.145

5.541

5.937

6.332

.610

.712

.813

.915

1.017

1.118

1.220

1.423

1.626

1.829

2.032

2.235

2.439

2.642

2.845

3.048

3.251

3.798

4.220

4.642

4.751

5.147

5.543

5.939

6.334

DiameterSmall End

"A"

Min Max

Keyway Width"C"

Nom Min Max

.094

.125

.125

.125

.156

.156

.188

.219

.250

.281

.313

.313

.313

.313

.313

.313

.313

.375

.438

.438

.500

.500

.563

.563

.563

.098

.129

.129

.129

.162

.161

.195

.226

.259

.291

.322

.322

.323

.323

.324

.324

.326

.388

.450

.450

.517

.516

.579

.579

.582

.100

.131

.131

.131

.165

.164

.198

.229

.262

.294

.325

.325

.326

.326

.327

.327

.329

.391

.453

.453

.520

.519

.582

.582

.585

Keyway Side Depth"D"

Figure 1.11

R C D

A

B MAX

Advantages of the Split CouplingSplit couplings can use shaft ends whichrequire no additional machining after receiptfrom the shafting supplier. Good qualityshafting is generally received with a groundor ground/polished finish. The shaft cangenerally be removed from a split couplingwithout use of heat or a press.

The ability to retain the shaft is excellent in awell machined split coupling.

Disadvantages of the Split CouplingSplit couplings use only friction to keep theshaft in the coupling. There is no positivemechanical stop preventing the shaft frompulling out of the coupling.

The inside diameter of the coupling boreshould be within 0.025-0.050 mm(0.001-0.002 in.) of the outside diameter of theshaft end to prevent vibration fromconcentricity error unbalance.

Advantages of the Set Screw CouplingThe set screw coupling allows very easy shaftremoval and reinstallation.

Set screw couplings can use shaft ends whichrequire no additional machining after receiptfrom the shafting supplier; good qualityshafting is generally received with aground/polished finish.

The set screw coupling requires the leastwork to manufacture. It is the least expensiveof all the rigid couplings.

Disadvantages of the Set ScrewCouplingIf the fit between the coupling bore and shaftis loose enough to permit convenientinstallation/removal, it is generally looseenough to allow at least some vibration due toconcentricity error.

Set screws in set screw couplings will causesome marring of the propeller shaft.

The heads of the set screws protrude fromthe outside surface of the set screw coupling.Good safety practice dictates usingguards/shields for personnel protectionagainst accidentally contacting the rotating setscrew heads.

Figure 1.13Set Screw Coupling

Figure 1.12Split Coupling

12

Soft CouplingsSoft couplings will accept relative motionsbetween their driving and driven sideswithout damage. These relative motions cantake the following forms.

Types of SoftnessRotating shafts which will move relative toeach other need couplings which permitmisalignment without damage. The ability toaccept misalignment without damage is oftencalled softness.

Radial SoftnessCouplings which are radially soft will allowthe driving or driven shafts some freedom ofmotion, so long as their centerlines remainparallel.

Axial SoftnessCouplings which are axially soft will allow thedriving or driven shafts to vary in theirend-to-end spacing. The sliding spline joints inthe middle of an automotive universal jointshaft, to allow the effective shaft length tovary are shaft couplings with axial softness.

Angular SoftnessAngularly soft couplings allow shaft angle tovary. Universal Joints are examples ofangularly soft couplings.

Combinations of SoftnessMost commercially available shaft couplingsare able to accommodate combinations of theabove types of relative motion ormisalignment. They vary in their tolerance fordifferent types of motion. Good designpractice will investigate the potential for thevarious types of shaft motion/misalignmentand confirm the shaft couplings are capable ofaccommodating the expected shaft motion.

Torsional Vibration IsolationTorsional vibration is cyclic irregularity ofrotation in a shafting system. It is caused byengine combustion pulses, reciprocatingmotion, and the propeller. As shafts in thesystem rotate, both the input torque (as eachcylinder fires) and the resistance to rotation(caused by irregularities in the velocity ofwater entering the propeller) vary. The torquevariation is natural and unavoidable. It is onlydangerous when uncontrolled. Torsionallysoft couplings are a way to control torsionalvibration.

Protection from MisalignmentPropeller shafts, marine transmissions andengines are mounted to the hull. The hull isnot perfectly rigid. Storm waves, temperaturechanges, propeller thrust, engine torquereaction, vessel loading and other factorsresult in forces which deform the hull causingmisalignment in the shafting. Themisalignment is unavoidable. Soft couplingsallow the system to accept the misalignmentwithout damage.

13

Angular Shaft Motion

Axial Shaft Motion

Radial Shaft Motion

Figure 1.14

Sound IsolationThe driveline of the vessel is a source ofnoise. One of the methods of reducingshipboard noise is to interrupt the noise path.One path for noise is from the engine downthe propeller shaft to the hull via the stuffingbox*. A soft coupling in the propeller shaft isan excellent means of introducing resilienceinto the path between the source of the noise(the engine and transmission) and thereceiver of the noise (the ears of thepersonnel on board).

*There are other equally important noise paths. Anotheris from the engine to the hull via the exhaust piping.See the Exhaust Section for guidance on use ofresilience in supporting exhaust piping.

Another noise path from the engine to the hull is viathe engine mounting feet. See the Mounting Sectionfor guidance on use of resilient engine mounts.Cooling lines can transmit engine vibration to the hullwhere it will be perceived as noise by the crews.Cooling water connections must include flexibility.

14

Mounting and AlignmentMarine Gear Installation – Propeller Shaft DroopMarine Gear Installation – AlignmentInstallation/Alignment InstructionsMarine and Engine Gear Mounting

Marine Gear Installation–Propeller Shaft DroopIntroductionThis procedure outlines the first of three basicsteps involved in the installation, alignment,and mounting of marine gears. It applies toboth free standing gears and gears that arefixed directly to the engine. It has limitedapplication to units which are soft mounted ordo not have a shaft support bearing betweenthe gear and stern bushing.

The second and third basic steps concerning:

• Marine gear to propeller shaft alignment.

• Marine gear (and engine) mounting, willbe covered in later sections of theapplication and installation procedures.

Propeller Shaft DroopBefore commencing alignment of the marinegear to the propeller shaft, the shaft droop, ordeflection due to the unsupported shaft andcompanion flange weight must becompensated for (Figure 2.1). This is animportant part of the installation andalignment procedure for marine gears.Otherwise, exceptional loading to the marinegear lower shaft bearings or the first propellershaft line bearing may result with consequent

increased noise or vibration and decreasedservice life of affected bearings.

Two methods are presented here foreliminating shaft droop as part of thealignment process:

• The estimated droop method, wherebydroop at the companion flange isestimated from droop tables and directlycompensated for.

• The scaled hoist method, wherebyunsupported shaft weight is directlycompensated for.

Both methods give reasonably closeapproximations of the shafts true center ifdone correctly.

Note: For both procedures prior connectionand alignment of propeller shafting from thefirst line bearing aft is required. Also, theshaft should be positioned about 13 mm (0.5 in.) aft of its final position when attachedto the marine gear.

Estimated Droop MethodThis method involves the use of tables whichcontain calculated deflection or droop valuesfor overhung steel shafting with small,medium, or large flanges mounted on the freeend (Figures 2.6, 2.7, 2.8; appendix A). Refer to Figure 2.1 for illustration of this

17

L shaft length (in.)D shaft diameter (in.)

=

1st Shaft Brg.

SHAFT DROOP DIAGRAM

Dial Indicator & Base

Companion Flange

(hub)

Dh

Length "L"

(flange)

deflection

Propeller Shaft

Figure 2.1

deflection or droop and the dimensions thatapply in using the droop tables.

Three sets of values, as illustrated in Figure2.1, are used in determining droop(deflection) at the shaft free end (flange end).They are:

1. Flange hub dia. “Dh”;2. Propeller shaft dia. “D”, and;3. Shaft overhang length “L”.

Dh/D determines which set of droop tablesapply (see Appendix A).

Dh/D = 1.40 to 1.74 use Figure 2.6.Dh/D = 1.75 to 1.99 use Figure 2.7.Dh/D = 2.00 to 2.25 use Figure 2.8.

The “D” and “L/D” intersection in theappropriate table determines the estimateddroop value.

To obtain shaft droop, first determine thevalues “L/D”, and “Dh/D”.

Then, go to the proper droop table for the“Dh/D” value and at the intersection of “D”and “L/D” read droop directly in inches.

For example: If Dh = 9.0 in. and D = 6.0 in.then Dh/D = 1.5 and Figure 2.6 should bereferred to. If overhung length is 120 in. thenL/D = 120/6 = 20.0. The droop is read directlyfrom Figure 2.6 at the intersection of D = 6.0,and L/D = 20 as droop = 0.148 in.

In many cases the actual D and L/D valueswill fall between those listed in the tables. Inthose cases droop can be found byinterpolation of the data in the tables. Anexample of this follows:

D = 6.3 in.L/D = 20.4Dh/D = 1.5

Since Dh/D is between 1.4 and 1.74 we willuse Figure 2.6.

The actual droop is shown as Ya, see Figure 2.2.

To obtain Ya proceed as follows:

Let Da = Actual diameter of the shaftD1 = Next lower diameter on droop

tableL/Da = Actual length to Diameter ratioL/D1 = Next lower L/D ratio on droop

tableL/D2 = Next higher L/D ratio on droop

table

Then Y1 = Droop at L/D1 and D1

Y2 = Droop at L/D2 and D2

Ya = Actual DroopYa = R (b – a) + a

Where R = (L/Da – L/D1) / (L/D2 – L/D1)a = (Da/D1)2 x Y1

b = (Da/D1)2 x Y2

In this exampleR = (20.4 – 20)/(21 – 20) = 0.4a = (6.3/6.0)2 x 0.148 = 0.163b = (6.3/6.0)2 x 0.178 = 0.196

Ya = 0.4 (0.196 – 0.163) + 0.176= 0.189 in.

Shaft Shaft Diameter

L/D 6.0 6.3 6.5

20.0 0.148 (a) 0.174

22.0 0.211 0.248

21.0 0.178 (b) 0.208

20.4 Ya

Figure 2.2

18

Scaled Hoist MethodThis method involves lifting, with the use of ascale, a weight equal to one half the overhungshaft weight, plus all the companion flangeweight with the lifting applied to thecompanion flange as shown in the illustration(Figure 2.3).

Weights for steel shafts or circular sectionscan be calculated using the following formula:

WEIGHT (lb) = 0.22 x D2 x L

Where:

D = diameter of shaft or circular section ininches

L = length of shaft or circular section ininches

Alternatively, the weights of the shaft andflange sections can be determined by use ofFigure 2.4 by simply multiplying the length, ininches, of any cylindrical section by the lb/in.value listed for the diameter of that section.

19

Scale Wt. #(lb) = sum of:0.11 x D2 x L = lb0.22 x Dh2 x h = lb0.22 x Df2 x f = lbWt.# = lb

(all dimensions in inches)

Dh

DfD

L h f

SCALED CORRECTION FOR SHAFT DROOP

Figure 2.3

Weights of Circular Steel Sections Per Inch of Length

Section Diameter 2.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75lb/in. Length 0.88 1.11 1.38 1.66 1.98 2.32 2.70 3.09

4.00 4.25 4.50 4.75 5.00 5.25 5.50 5.75 6.00 6.25 6.503.52 3.97 4.46 4.96 5.50 6.06 6.66 7.27 7.92 8.59 9.30

6.75 7.00 7.25 7.50 7.75 8.00 8.25 8.50 8.75 9.00 9.2510.0 10.8 11.6 12.4 13.2 14.1 15.0 15.9 16.8 17.8 18.8

9.50 9.75 10.0 10.5 11.0 11.5 12.0 12.5 13.0 13.5 14.019.9 20.9 22.0 24.3 26.6 29.1 31.7 34.4 37.2 40.1 43.1

14.5 15.0 15.5 16.0 16.5 17.0 17.5 18.0 18.5 19.0 19.546.3 49.5 52.9 56.3 59.9 63.6 67.4 71.3 75.3 79.4 83.7

Figure 2.4

Since half the shaft weight plus all of thecompanion flange weight is to becompensated for at the scale, total scaleweight can be calculated by the work sheetincluded in Figure 2.3 (example Figure 2.5).

Example Problem:(ref. Figures 2.3 & 2.5) If in our illustrationFigure 2.3, the following dimensions apply:

Shaft diameter D = 4.0 in.; and, shaft lengthL = 60.0 in.;

Companion flange hub diameter Dh = 6.0 in;hub length h = 6.5in.;

Flange section diameter Df = 9.0 in.; flangethickness f = 0.75 in.

Proceed in calculating hoist pull “P” (lb) asfollows: Note: In this example both methodsof obtaining weights will be shown.

First, overhung shaft weight is calculated as:(per formula-1)Wt. = 0.22 x (4.0)2 x 60 = 211.2 lb

(per Figure 2.4)Wt. = 60 in x 3.52 lb/in = 211.2 lb

Half of overhung shaft wt. = 105.6 lb

Then, companion flange weight, includingshaft material inserted into the flange, iscalculated:

(per formula-1):Hub section wt. = 0.22 x (6.0)2 x 6.5 = 51.5 lb

Flange section wt. = 0.22 x (9.0)2 x 0.75 = 13.4 lb

(per Figure 2.4)Hub section wt. = 6.5 in x 7.92 lb/in = 51.5 lb

Flange section wt. = 0.75 in x 17.8 lb/in = 13.4 lb

Total companion flange wt. = 64.9 lb

Finally, the scale reading at the hoist shouldbe the sum of the total companion flange wt.and half the overhung shaft wt.:“P” = 105.6 + 64.9 = 170.5 lb

Caution: The hoisting mechanism must beset up in such a manner that the direction ofpull or lift is straight up, i.e., no force is to beexerted sideways in order to avoid side to sidemisalignment of the marine gear to thepropeller shaft. This can be checked with aplumb line suspended from the overheadconnection for the hoisting mechanism.

Also, if the hoist is to be removed and theshaft supported by other means prior to finalconnection to the marine gear, dial indicatorsat vertical and side locations should beemployed to insure the shaft remains at itsproper position.

20

Scale Wt. #(lb) = sum of:0.11 x D2 x L = 105.6 lb0.22 x Dh2 x h = 51.5 lb0.22 x Df2 x f = 13.4 lbWt.# = 170.5 lb

(all dimensions in inches)

SCALED CORRECTION FOR SHAFT DROOP

Dh = 6.0

Df = 9.0 D = 4.0

L = 60.0h = 6.5

f = 0.75

Figure 2.5

21

Shaft Diameter (inches) for Hub Diameter = 1.40 to 1.74 times Shaft Diameter

ShaftL/d 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0

8 .001 .001 .001 .002 .002 .003 .004 .004 .005 .006 .007 .008 .0099 .001 .001 .002 .003 .004 .005 .006 .007 .008 .009 .011 .013 .014

10 .001 .002 .003 .004 .005 .007 .008 .010 .012 .014 .016 .018 .02111 .002 .003 .004 .006 .007 .009 .012 .014 .017 .019 .023 .026 .02912 .003 .004 .006 .008 .010 .013 .016 .019 .023 .027 .031 .035 .04013 .003 .005 .008 .010 .013 .017 .021 .025 .030 .036 .041 .047 .05414 .004 .007 .010 .014 .018 .022 .028 .033 .040 .047 .054 .062 .07115 .006 .009 .013 .017 .023 .029 .035 .043 .051 .060 .070 .080 .09116 .007 .011 .016 .022 .029 .036 .045 .054 .065 .076 .088 .101 .11517 .009 .014 .020 .028 .036 .046 .056 .068 .081 .095 .110 .127 .14418 .011 .017 .025 .034 .044 .056 .069 .084 .100 .117 .136 .156 .17819 .014 .021 .031 .042 .054 .069 .085 .103 .122 .144 .166 .191 .21720 .016 .026 .037 .050 .066 .083 .103 .124 .148 .174 .201 .231 .26321 .020 .031 .044 .060 .079 .100 .123 .149 .178 .208 .242 .278 .31622 .023 .037 .053 .072 .094 .119 .147 .178 .211 .248 .288 .330 .37623 .028 .043 .062 .085 .111 .140 .173 .210 .250 .293 .340 .390 .44424 .033 .051 .073 .100 .130 .165 .203 .246 .293 .344 .399 .458 .52125 .038 .059 .085 .116 .152 .192 .237 .287 .342 .401 .465 .534 .60826 .044 .069 .099 .135 .176 .223 .275 .333 .396 .465 .539 .619 .70427 .051 .079 .114 .155 .203 .257 .317 .384 .457 .536 .622 .714 .81228 .058 .091 .131 .178 .233 .295 .364 .441 .524 .615 .714 .819 .93229 .067 .104 .150 .204 .266 .337 .416 .503 .599 .703 .815 .936 1.06530 .076 .118 .170 .232 .303 .383 .473 .573 .681 .800 .927 1.065 1.211

Figure 2.6


ShaftL/d 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0

8 .001 .001 .002 .003 .004 .005 .006 .007 .008 .009 .011 .013 .0149 .001 .002 .003 .004 .005 .007 .008 .010 .012 .014 .016 .019 .021

10 .002 .003 .004 .006 .008 .010 .012 .014 .017 .020 .023 .027 .03011 .003 .004 .006 .008 .010 .013 .016 .020 .024 .028 .032 .037 .04212 .004 .006 .008 .011 .014 .018 .022 .027 .032 .037 .043 .050 .05613 .005 .007 .010 .014 .019 .024 .029 .035 .042 .049 .057 .065 .07414 .006 .009 .014 .018 .024 .030 .038 .045 .054 .064 .074 .085 .09615 .008 .012 .017 .023 .031 .039 .048 .058 .069 .081 .094 .108 .12216 .010 .015 .022 .029 .038 .049 .060 .073 .086 .101 .117 .135 .15317 .012 .019 .027 .036 .047 .060 .074 .090 .107 .125 .145 .167 .19018 .015 .023 .033 .044 .058 .074 .091 .110 .131 .153 .178 .204 .23219 .018 .027 .040 .054 .070 .089 .110 .133 .158 .186 .216 .247 .28220 .021 .033 .048 .065 .084 .107 .132 .160 .190 .223 .259 .297 .33821 .025 .039 .057 .077 .101 .127 .157 .190 .226 .266 .308 .354 .40222 .030 .046 .067 .091 .119 .150 .186 .225 .267 .314 .364 .418 .47523 .035 .054 .078 .107 .139 .176 .218 .264 .314 .368 .427 .490 .55824 .041 .063 .091 .124 .163 .206 .254 .307 .366 .429 .498 .571 .65025 .047 .074 .106 .144 .188 .238 .294 .356 .424 .497 .577 .662 .75426 .054 .085 .122 .166 .217 .275 .339 .411 .489 .573 .665 .763 .86927 .062 .097 .140 .191 .249 .315 .389 .471 .560 .658 .763 .876 .99628 .071 .111 .160 .218 .284 .360 .444 .538 .640 .751 .871 1.000 1.13729 .081 .126 .182 .247 .323 .409 .505 .611 .727 .854 .990 1.136 1.29330 .091 .143 .206 .280 .366 .463 .572 .692 .823 .966 1.121 1.286 1.464

Figure 2.7

22


ShaftL/d 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0

8 .001 .002 .003 .004 .005 .006 .008 .009 .011 .013 .015 .018 .0209 .002 .003 .004 .006 .007 .009 .011 .014 .016 .019 .022 .026 .029

10 .003 .004 .006 .008 .010 .013 .016 .020 .023 .027 .032 .036 .04111 .004 .006 .008 .011 .014 .018 .022 .027 .032 .037 .043 .050 .05712 .005 .007 .011 .014 .019 .024 .030 .036 .043 .050 .058 .067 .07613 .006 .010 .014 .019 .025 .031 .039 .047 .056 .065 .076 .087 .09914 .008 .012 .018 .024 .032 .040 .050 .060 .071 .084 .097 .111 .12715 .010 .016 .022 .031 .040 .051 .062 .076 .090 .106 .122 .141 .16016 .012 .019 .028 .038 .050 .063 .078 .094 .112 .131 .152 .175 .19917 .015 .024 .034 .047 .061 .077 .096 .116 .138 .161 .187 .215 .24518 .019 .029 .042 .057 .074 .094 .116 .141 .167 .196 .228 .261 .29719 .022 .035 .050 .069 .089 .113 .140 .169 .201 .236 .274 .315 .35820 .027 .042 .060 .082 .107 .135 .167 .202 .240 .282 .327 .375 .42721 .032 .049 .071 .097 .126 .160 .197 .239 .284 .334 .387 .444 .50522 .037 .058 .084 .114 .148 .188 .232 .281 .334 .392 .455 .522 .59423 .043 .068 .097 .133 .173 .219 .271 .328 .390 .458 .531 .609 .69324 .050 .079 .113 .154 .201 .254 .314 .380 .452 .531 .616 .707 .80425 .058 .091 .130 .178 .232 .293 .362 .438 .522 .612 .710 .815 .92826 .067 .104 .150 .204 .266 .337 .416 .503 .599 .703 .815 .935 1.06427 .076 .119 .171 .233 .304 .385 .475 .575 .684 .802 .931 1.068 1.21528 .086 .135 .194 .265 .345 .437 .540 .653 .777 .912 1.058 1.215 1.38229 .098 .153 .220 .299 .391 .495 .611 .739 .880 1.033 1.198 1.375 1.56430 .110 .172 .248 .338 .441 .558 .689 .834 .992 1.165 1.351 1.551 1.764

Figure 2.8

Marine Gear InstallationGeneral InformationAlignment of the marine gear to propellershafting in the vessel warrants close attention.The alignment must be within specifiedtolerances for satisfactory transmissionservice life. This discussion outlines the stepsin accomplishing such alignment. It applies toboth free standing (island mounted) marinegears and those bolted directly to thepropulsion engine at the flywheel.

Alignment must be accomplished while theshafting is at, or very near, its true centerlineposition (ref. discussion in preceding sectionregarding shaft droop).

After the propeller shaft droop has beencompensated for, and the shaft properlysupported at the free end as shown in Figure 2.9, the marine gear or gear andengine combination may then be aligned tothe propeller shaft.

Alignment Terms andParametersThe objective of the alignment processoutlined herein is good axial alignment of themarine gear to the shafting. Axial alignment isthe relationship of the axis of rotation of themembers to be coupled, in this case, thepropeller shaft and gear output flanges.

There are two basic alignment parametersinvolved in this process. They are:

1. Parallel or bore alignment.2. Angular or face alignment.

23

d

e

T.I.R. =2emarine

gearengine

"d" = gap between matingflange faces.

"e" = offset dimension ofmating flange/shaftaxis

"T.I.R" = Total Dial Indicator R eadings

Support forzeroing deflection

PROPULSION INSTALLATION SCHEMATIC

Figure 2.9

Angular misalignment occurs when thecenterlines (axis) of the marine gear outputshaft and the propeller shaft are not parallel.The limits for parallel and angularmisalignment are given in the AlignmentProcedure section.

Parallel misalignment occurs when thecenterlines, or axis, of the marine gear outputshaft and propeller shaft are parallel but not inline.

Conditions Required forAlignmentPrecision machinery deserves every effort toassure its proper alignment, but it cannot beassumed the machinery bed is a level,stationary, non-deflecting surface. The hull isconstantly deflecting, due to daily andseasonal temperature variation, various loadand ballast conditions, and sea conditions.

Do not attempt final alignment of propulsionmachinery unless the following conditions aremet:

• The vessel is in the water.

• All permanent ballast is in place.

• Fuel, Water, and Temporary Ballast Tanksare filled to normal, average, operatinglevels, generally 1/2 to 3/4 filled. It is notnecessary to fill fuel tanks with fuel, sinceit is only the weight of the fluid in thetanks that is important to load the hull torepresentative displacement. Water is asuitable alternative to fuel for thispurpose.

• All major machinery—weighing over 225 kg (500 lb)—is either installed orsimulated by equivalent weightsappropriately located.

Note: Where prior experience has showngood results, the alignment process can besubstantially completed prior to launch. Makefinal alignment check immediately prior to seatrials.

24

angular misalignment

parallel misalignment

Figure 2.10

Alignment ProcedureMarine gears and engines with flywheelhousing mounted marine gears:

1. With the propeller shaft set on roller blockor oiled “V” block sweep the flange facewith a dial indicator (Figure 2.11). Whilewatching the indicator, rotate the shaftand note the point of minimum indicatorreading. Make a reference mark (withpaint, center punch, . . .) on the flange rimat the bolt hole nearest the point ofminimum indicator reading. For all futurereadings on this flange this will be the“ZERO” reference location “A”.

2. With the dial indicator set at the “A” zeroreference location, set the dial to zero.Rotate the shaft and measure and recordindicator readings at the 3:00, 6:00, and9:00 positions (facing the flange). Thesepositions correspond to positions “B”, “C”,and “D” respectively. Continue therotation to one complete turn, recheckingat the “A”, or 12:00 position for zeroindicator reading.

3. Using the same zero “A” reference pointset the dial indicator to measure andrunout of the flange rim (periphery).Repeat the procedure outlined in step 2 toaccomplish this.

4. Repeat steps 1 to 3 to measure and recordmarine gear output flange face andperipheral runout with the followingexception: Use bolt hole location nearestpoint of “maximum” indicator reading forzero “A” reference.

Any runout errors must be accounted for inthe alignment process. The maximumallowable runout, for most Twin Disc marinegears offered by Caterpillar, is:

Maximum Face Runout = 0.10 mm (0.004 in.)Maximum Bore Runout = 0.10 mm (0.004 in.)Runouts shown are total dial indicatorreadings (T.I.R.).

Note: If face (or bore) runout is excessive onthe marine gear flange, some correction maybe obtained by removing and reinstalling theflange at a different position (if the type ofconnection permits).

Compensation may also be obtained byselective match of the mating flangesproviding flanges have not already beenreamed and matched for fitted boltsconnection. For example, if the “A” referencepoints of both flanges, as determined in steps1 and 4 are mated then face runoutcompensation will be realized (Figure 2.12).

25

METHOD AND TERMINOLOGY FORMEASURING OUTPUT FLANGE ORCOUNTER FLANGE RUNOUT

F

P dial indicators(periphery & face)

"D"

"C"

"B"

"A"(zero)

Figure 2.11

Carrying this example further, if maximumT.I.R. of the shaft flange is +0.008 in. and thatof the marine gear flange is –0.005 in. they areindividually out of tolerance, however, theireffective runout is their sum which is 0.008 +(–0.005) = 0.003 in.. This would be acceptablesince it is within the 0.004 in. limit.

5. Position the propeller shaft about 8 mm (0.3 inches) aft of its planned finalposition.

Note: At this point scantlings or supports forthe gear engine mounting should be in placewith sufficient gap for poured or metal shims.If not, install these supports now.

6. Now move the marine gear (or gearengine package) to its approximate finalposition so that mating flange gap is about8 mm (0.3 in.), per step 5, withoutengaging the flange pilot.

7. Bore alignment: Take measurements ofthe diameter gap at four equally spacedpoints on the flanges’ diameters. Astraight edge with a feeler gauge, or a dialindicator may be used as shown in Figure 2.13 to accomplish this. If the dialindicator is used, mount it on the gearoutput flange as shown and sweep thecompanion flange for T.I.R. Makeappropriate position adjustments withwedges or jacking screws to locate themarine gear output flange within 0.127 mm (0.005 in.) of bore alignment(dimension e, Figure 2.13). MaximumT.I.R. would be 0.254 mm (0.010 in.). Aslip fit of mating flange pilots ontransmissions so equipped—ensuresadequate bore alignment.

26

"A" reference points

maximum effective runout minimum effective runout

COMPENSATION FOR MATING FLANGE FACE RUNOUT

Figure 2.12

d

e

T.I.R. = 2e

ALIGNMENT METHODS(flange to flange)

feelergauge

straight edge

feelergauge

Figure 2.13

8. When this condition is met, engage theflanges’ pilot surfaces by bringing thepropeller shaft and companion flangeforward to within 4.5 mm (0.180 in.) at allpoints about the diameter of the flanges.

9. Angular Alignment: Positionadjustments of the engine andtransmission may now be made to alignthe marine transmission output flange to aproper angular or face alignment position.Using a feeler gauge, or small hole gauge,take measurements of face gap at fourequally spaced positions; A, B, C, and D.(Figure 2.13) Then, proceed as follows:

a. Tabulate the readings of face gap.b. Compare diametrically opposite face

gap readings (compare readings at A toreadings at C; and readings at B toreadings at D).

c. Subtract the smaller of diametricallyopposite readings from the larger forboth A to C, and B to D.

Example: if the reading at A is0.175 in. and the reading at C is 0.165 in., then subtract 0.165 from0.175 giving a result of 0.010 in.

d. The resulting differences areproportional to the amount of angularor face misalignment. The face gapdifference reading must not exceed0.005 in. (A to C, or B to D). If the gapdifference reading exceeds this value,the engine and marine gear must bemoved until the required tolerance isreached.

e. As the engine is moved for angularalignment, ensure the bore alignmentis not altered.

10. Recheck all alignment readings, insert thebolts into the flanges, and prepare themarine gear/engine supports for finalsecuring to the boat’s engine foundation.

Except for final alignment checks, aftersecuring the unit to the foundation and priorto sea trial of the vessel, this completes thealignment process.

Installation/AlignmentInstructionsCaterpillar Engines and otherFree Standing Marine Gears andVulkan Rato Flexible Couplings

IntroductionThe purpose of this instruction sheet is tooutline a proven and effective procedure foraccurate alignment of Caterpillar MarineEngines to free standing reduction gears,most specifically, where Vulkan Rato flexiblecouplings are used. The procedure can beadapted to most other coupling types if care istaken to allow relative radial and angularmovement between engine and marine gearcoupling interface during the alignmentprocess.

PreliminaryThe following preliminary steps shouldalready have been done or in place beforestarting engine to gear alignment:

1. Propeller shafting in place. Marine gearaligned to shaft and secured to foundationwith fitted bolts and thrust stops asrequired.

2. Flexible coupling inner member mountedto marine gear and outer membermounted to engine flywheel perFigure 2.14.

3. Engine positioned in close proximity (bysight) to the final alignment, but withcoupling outer and inner members nottouching.

4. Jacking screws are for engine side to sideand fore and aft positioning movement inplace (provided and installed by shipyardor installer). Jacking screws provided withengine for vertical positioning should beclean and well oiled.

5. Necessary tools and instrumentation athand, such as: dial indicators withbracketry; yoke for mounting instrumentsto marine gear hub (ref part numbers6V2042 & 6V2043); pry bar for moving

27

crankshaft fore/aft and flywheel up/down;turning tool for rotating engine atflywheel; and miscellaneous hand tools.

Step 1a. Clean periphery of flywheel and face of

coupling/flywheel adapter plate so dialindicators can sweep face and circularrunout at flywheel through one completerotation. Remove any nicks or burrs thatinterfere with dial indicator readings. Alight cleaning with oil may also bebeneficial.

b. Mount dial indicators from flywheelhousing as shown in Figure 2.14.

c. Rotate engine through one completerevolution and note total dial indicatorreadings for both face and periphery offlywheel. Record these readings. (Omitthis step if coupling has torsional stop.)

d. Remove an engine block side cover and,with the pry bar between the crankshaftweb and the main bearing saddle, movethe crankshaft fore and aft. Record totalindicator movement on data sheet. Leavecrankshaft in full forward position.

e. With pry bar, move flywheel up (fulltravel) and record half of the totalmovement. This is the flywheel droop.

f. Determine offset dimension “Y”. This isthe amount the marine gear should be sethigher than the engine and is equal toflywheel droop, (as found in step “e”), plusthe difference in thermal growth of theengine and gear input centers “Xt”.

“Y” = [F. W. droop + Xt]“Xt” is approximated by the formula:Xt = [0.009 – (0.0004 x d)] in.(Where d = gear input to mounting ledgedistance in inches.)

Note: For WAF gear models 540 & 560; Xt = + 0.003 in. may be used. For WAF models860 & 1160; use Xt = – .002 (negative). Xt forWAF models 640, 660, 740, 760, 840, and 1140is small and can be ignored.

g. Compute “Y” = F.W. droop + Xt = ______ + ______ = ______ Record “Y” on data sheet, see Figure 2.15.

FlywheelHousing

Flywheel

Figure 2.14

28

Step 2a. Remove dial indicators from flywheel

housing.

b. With the crankshaft still fully forward,position the engine to the marine gear sothat the flexible coupling outer member isaligned with the inner member (by sight)and the gap between the inner and outermembers, measured with a feeler gauge,is equal to half the total fore/aftcrankshaft movement, measured in step1d, ±0.002 in. The gap should bemeasured at the connection points for thebolts marked “X” in Figure 2.16.

Note: Do not install these bolts at this time.

c. Turn the marine gear input shaft andcheck for freedom of movement. It shouldturn without much difficulty but may havea slight drag against the coupling outer orengine side member. If it turns withdifficulty, or not at all, repeat part “a” ofthis step.

Step 3a. Install necessary yoke, brackets, etc., and

mount dial indicators as shown in Figure 2.16.

Note: For the procedure outlined here it willbe assumed that movement of the indicatortip into the dial case results in a positivereading. Also, all dimensions are in inchesunless indicated.

Note: If coupling is equipped with torsionalstops (come home feature) proceed directly tosub step “e”; If coupling is not equipped withtorsional stops (come home feature) proceedas follows:

b. Swing marine gear input shaft throughone revolution while making sure noobstructions or protrusions hinder smoothmovement of the indicator tips over thesurfaces.

c. Set dial indicators at “A” position and setdials to zero readings. Rotate the marinegear input member (or engine and geartogether if equipped with torsional stops)and record T.I.R. readings, for both faceand periphery, at locations B, C, and Dper diagram in Figure 2.15. Recheck forzero at location A.

29

Face Periphery(zero) (zero)

A A

D B D B

C C

Limits:B,C,D = ±0.010 in.max indicator reading

Max. indicator differenceof B to D is 0.010 in.

Limits:C = 2Y±0.005 in. (Y = in.)D + B = C± 0.005 in.Max. indicator differenceof B to D is 0.010 in.

Figure 2.15

30

d. Using the limits outlined in Figure 2.15,for face and peripheral dial indicatorreadings, adjust engine position asrequired to obtain readings within thoselimits. This will probably require severalattempts to achieve the desired readings.For couplings without torsional stopfeature, refer back to runout readingsrecorded at step 1c. If those readings arenot more than 0.127 mm (0.005 in). faceand 0.203 mm (0.008 in.) peripheralproceed directly to step 4, otherwise,continue at “e”.

e. Install several clearance bolts at location“X” so that engine and gear can be rotatedtogether without unduly constrainingrelative radial movement of the matingcoupling members.

f. Repeat sub steps “c” and “d” except rotateengine and gear together by barring orturning the engine flywheel. Whenreadings within the desired range, perFigure 2.15, are obtained remove theclearance bolts at “X” and proceed to step 4.

Step 4Check axial clearance between couplingmembers. With crankshaft full forward thereshould be some clearance between membersor, if they are touching, inner member shouldbe rotatable against outer member withoutexcessive drag. (One man should be able toturn gear input shaft by hand or with a .610 mm (2 ft) long bar.) With crankshaft allthe way to the rear, coupling members shouldbe touching or gap should not exceed 0.508 mm (0.020 in.). Make sure theseconditions are met before proceeding to step 5.

"P""F"

D

C

B

EngineFlywheel

CouplingInner

Member

CouplingOuter

Member

Figure 2.16

Step 5a. Pour engine chocks or install solid steel

shims and secure engine to foundation byappropriate procedures. Do Not installfitted foundation bolt at this time.

Note: Loose metal shims are notrecommended for heavy engine mountings.

b. When part “a” is complete (be suresufficient cure time has been allowed forpoured chocks) recheck face andperipheral alignment readings per step 3.If readings have changed, which is oftenthe case, do not re-align if limits outlinedin Figure 2.15 have not been exceeded bymore than 0.127 mm (0.005 in.) face and0.254 mm (0.010 in.) periphery.

c. With condition “b” met install fitted bolt atrear engine mount on either left or rightside. Install collision chocks if required.

d. Using bore aligning tools (tapered pins)align mating coupling members and installsnug fit bolts at locations “X”. Do nothammer bolts in. Press them in orsqueeze them in with pliers. They shouldbe installed with the heads to the engineside.

e. Remove instrumentation, reinstall blockside cover, etc.

f. This completes the alignment process. Ifthe alignment has been done in dry dockor on a new build in the yard, thenalignment should be rechecked whenvessel is floated and contains partialstores. This step is critical for vessels withless rigid foundation systems or thosemore sensitive to float conditions such asflat bottom types.

Record Final ReadingsFrom steps 1 “d” & “e”:

Total flywheel vertical movement . . ___ in.Total crankshaft movement fore/aft . . ___in.

FACE PERIPHERY0.000 0.000

A A___D B___ ___D B___

C C

31

Marine and Engine GearMountingGeneral InformationPreliminaryProper mounting of the marine gear andpropulsion engine in the vessel, once theyhave been aligned, is critical to maintaininggood alignment and consequent smooth, quietoperation and so warrants close attention.This discussion describes the requirementsand procedures for mounting marine gearsand Caterpillar Engines to the shipsfoundation and propulsion driveline.

As an engine manufacturer, we can identifythe requirements for proper mounting andalignment of the Caterpillar product, however,the responsibility for proper total mountingand alignment always rests with theequipment installer. Primary objectives are:

Mount the marine gear so that–

Full propeller thrust can be transmitted toship structure (except where thrustbearing is separate from marine gear).

Transmitted thrust or other externalforces do not adversely affect gearalignment to either the propeller shaftingor the engine.

The forces it exerts on its foundationcause no damage.

The engine must be mounted so that it isnot prestressed.

Movements of the hull cannot reach theengine cylinder block and crankshaft.

Driveline thrust forces are not allowed toreach the crankshaft.

Its natural thermal growth and shrinkageis not restrained.

The forces it exerts on its foundationcause no damage.

Rigid Mounting or Resilient Mounting maybe used.

FoundationsThe marine gear/engine foundation is thatportion of the boat’s structure which supportsthe propulsion machinery and holds it inproper relationship to the drivelinecomponents. It generally consists of twolongitudinal rails–with liberal transversebracing–which carry the weight, thrust,torque reaction and inertial loads of thegear/engine. It is good design practice tomake the foundation members as long aspossible. This helps to limit hull deflection bydistributing the loads over more of the hulllength.

The entire foundation must be strong enoughto withstand continued operational forces dueto torque, thrust, pitching, rolling, andoccasional grounding. Since no structure isabsolutely rigid, it is essential that thefoundation have greater rigidity than thedriveline, so that none of the components ofthe driveline are stressed beyond their limitswhen flexing of the hull occurs. Foundationstructures may be of metal (steel oraluminum), wood, or fiberglass dependingusually on the vessels hull composition. Infiberglass vessel’s, foundations will generallybe of the foam filled type, or wood:

Foam filled foundations require a metal raftbetween the machinery and the fiberglassfoundation to distribute machinery loads moreevenly.

Wood foundations allow for relatively simplemounting, using lag screws, and does notnormally require special load distributingtechniques.

Mounting TypesEngine and marine gear mounting generallyfalls into one of two categories, i.e. rigid orresilient.

Rigid Mounting. The engine supports andnecessary shims are fastened directly to theboat’s structure. The shims, used forpositioning the engine or gear in properalignment, are either steel or poured plastic(refer to the section on shims presented laterin this document). With no vibration mountsbetween the engine supports and the boats

32

structure, flexibility must be built into theengine supports to prevent the engine blockfrom becoming stressed by motions of thehull. It is the simplest and least costly way tomount an engine.

Rigid mounted machinery is generally boltedto the engine foundation.

Resilient Mounting of machinery is usuallydone for isolation of noise and vibration fromthe ship structures. It is more expensive andrequires more attention to detail than rigidmounting. Flexible fittings must be used forall connections (combustion air, coolant, fuel,exhaust gas, controls, etc.) when resilientmounts are used. A section on resilientmounts is presented later in this document.

Mounting ProceduresNote: In the procedures that follow, it isassumed the alignment processes, i.e., marinegear to shafting and engine to marine gearhave been accomplished per proceduresoutlined in previous sections.

Marine Gear MountingFor rigid mounting of free standing(separate from engine) marine gearsproceed as follows:1. Make a final check of the marine gear

support structures for adequate size,strength, shim space, and sufficientclearances for mounting bolts. If themarine gear mounting brackets are of thebolt on type, make sure they are properlysecured against further movement relativeto the gear case (dowels in place, etc.).

2. If metal shims (chocks) will be used,machine and fit the shims to each side ofthe marine gear. Refer to the procedureoutlined in the appendix for shim fittingand mounting.

Note: In exception to the caution listed inappendix, it is permissible to use peel typeshim packs, or a few loose shims inconjunction with a thick steel chock. Inboth cases, stainless steel is preferred.This exception is due to the relative lowerlinear vibration and greater stability of themarine gear as compared to the engine.

3. Taking care not to move or disturb thegear to shaft alignment, drill and ream theholes for the fitted foundation bolts. Aminimum of two fitted bolts should beused. They should be installed on eachside and directly (not diagonally) oppositeeach other. For some marine gears it ispermissible, but seldom necessary, to usefitted bolts in the remaining bolt holelocations. The thrust capacity of the boltedmarine gear foundation results from: (a)the fitted bolts shear strength and, (b) theclamping force of all the foundation boltstogether.

4. Install all fitted and clearance foundationbolts loosely with the threaded ends up. Itis best to have sufficient thread showingfor installation of double nuts.

5. If poured resin shims are to be used, referto procedures outlined in the appendix,and to the resin manufacturer’sinstructions. The basic steps are: (a) Prepare for the pour, i.e. dams aroundpads, spacers around clearance bolts, etc.(b) Recheck the gear to shaft alignmentand reposition the gear as required toassure proper alignment. (c) Make thepour. Allow the poured shims to cure permanufacturers instructions and tightenthe hold down nuts to the torquecalculated per appendix, so that therecommended pressure on each chockwill not be exceeded. (The pressureapplied is the sum of the gear weight andbolt loads.)

6. If metal shims are being used, tighten thehold down bolt nuts per Figure 2.24 in theappendix.

7. Make a final alignment check and, ifsatisfactory, install the double nuts. Markthe nuts at the thread with a daub of paintfor easier periodic visual checks of thebolt connections.

33

8. Draw the marine gear output flange andpropeller companion flange connectiontight with the connecting bolts. Theconnecting bolts are either fitted orclearance type. The fitted bolt connectionscarry the transmitted torque primarily bybolt shear strength, and by some degreeof clamping force. As a rule of thumb,fitted bolts are usually required onpropeller flange connections transmittingtorque of 0.75 kW/rpm (1 hp/rpm) orgreater. Below that torque level bolt loadclamping force is often adequate to carrythe transmitted torque with a high degreeof safety, especially if grade 8 bolts at hightightening torque are used.

If non fitted bolts are used, grade 8 boltstorqued to the standard high torque valuesshould be used since full output torquewill be carried by the bolt clamping force.The nominal standard torque and hightorque values for 3/8 in. to 1-1/2 in. bolts,along with the resulting bolt load aregiven in Figure 2.18, (high torque valuesin bold print). Using these loads and theformula given in Figure 2.17, the torquethat can be safely transmitted through theflange connection can be calculated. If fitted bolts are used, drill and ream the

mating bolt holes (if this has not alreadybeen done) and install the fitted bolts.Torque the fitted bolts to the standardtorque values for the bolt size or to thesuppliers’ recommended torque ifspecified.

9. Install thrust or collision blocks ifrequired. Install the blocks on both sidesof the marine gear with sufficientclearance for thermal expansion of thegear case. The expansion that needs to beallowed for occurs over the distance fromthe collision block to the first fitted boltconnection. A clearance of 0.0008 in./in. ofthat distance should be provided forengine jacket water cooled gears. Provideclearance of 0.0006 in./in. of that distancefor sea water or keel cooled gears.

Bolt Size Torque (lb/ft)Bolt Load

"Bp" lb

.375 - 16 & 24 3240

5,2008,200

.738 - 14 & 20 5065

7,10011,400

.500 - 13 & 20 75100

9,20015,400

.563 - 12 & 18 110145

12,00020,000

.625 - 11 & 18 150200

14,80025,000

.750 - 10 & 16 265350

22,00037,000

.875 - 9 & 14 420550

30,00049,500

1.000 - 8 & 14 640825

40,00065,000

1.125 - 7 & 12 8001,000

44,40071,000

1.250 - 7 & 12 1,0001,350

50,00087,000

1.375 - 6 & 12 1,2001,700

55,000100,000

1.500 - 6 & 12 1,5002,000

63,500108,000

Figure 2.18

Dp

Db

N = no. of boltsDp = Bolt Circle dia. (in.)Db = Bolt shank dia. (in.)To = Torque (hp/rpm)Bp = Bolt load (lb)

Allowable TransmittedTorque (non fitted bolts):

To = Dp x N x Bp (hp/rpm)2,800,000

Figure 2.17

34

Soft Resilient Mounting of freestanding marine gearsSoft mounting of free standing marine gears isinfrequent and done only in very special casesas a rule. Due to the various cautions andcomplexities involved in such installations, theprocedure will not be addressed here in detailbut the following features are common inthese installations:

Remote mounted thrust bearing to isolate themarine gear from the thrust force component.

When the above is used, relative motionbetween the gear and thrust bearing have tobe accommodated which, in turn, may requireone or more of the following: a cardan shaft(with slip connection); a flexible drivecoupling; or a sufficient length of unsupportedshaft between the gear and thrust bearing toaccommodate the movement.

Since the engine would also be soft mountedin these installations, special provision isrequired in the engine to marine gearconnection to accommodate the relativemovement between the engine and gear,which may be substantial.

One advantage to this type of installation isthat resilient mounts may be selectedspecifically for either the engine or marinegear to tune out their particularsound/vibration frequencies. Due to thehigher frequencies of the noise or vibrationbeing isolated, the resilient mounts used forthe marine gear will most likely beconsiderably more stiff than those used for

the engine. The mounts will normally havestops incorporated in them to limit motion.

Combined Engine/Marine GearMountingRigid Mounting of pre-assembledmarine gear/engine unitsThese units, already coupled, have either: (a) continuous rail type supports incorporatedon either side (Figure 2.19a), or (b) a threepoint mounting support system (Figure 2.19b)incorporating a single point front trunnionmount.

When the marine gear and engine areconnected at the bell and flywheel housingsand mounted on rails, (Figure 2.19a), thepackage is very strong and can be consideredas one unit. Its longitudinal stiffness andlength make it very practical for soft mountingif the propeller shaft connection and relativemovement are properly accommodated. Afitted bolt, or bolts, is used only at the rearlocation as indicated in the sketch below.

Further installation procedures for thisarrangement are as outlined in the enginemounting section which follows this section.

Marine gear and propeller companion flangeconnections in both of the abovearrangements are as covered previously.

If the marine gear and engine are connectedbut not on common rails, as shown inFigure 2.19b, the marine gear is mounted aspreviously outlined. The front mount, in thiscase, is usually a trunnion type. The trunnion

35

Fitted Bolt Locations

engine enginegear gear

(a) (b)

Figure 2.19

mount is attached to both ship rails but has asingle swivel connection at the front of theengine with the swivel center on thecrankshaft centerline. It often has somedegree of fore/aft flexibility as well as a fairamount of rotational freedom. Clearance boltsare normally used for the front mounts. Thisis especially so if the front mount is rigid (nottrunnion). In either case, clearance orflexibility of about 0.0008 in./in. of distance,from the fitted bolt or dowel at the marinegear mount, must be provided for thermalexpansion of the engine and gear.

Resilient Mounting of pre-assembledmarine gear/engine unitsA common method of sound/vibrationisolation is to have the gear and enginecombined by flywheel housing connectionand/or common rails (Figure 2.19) and thewhole system then isolation mounted.

Resilient mounts under relatively small, closecoupled engine/marine gear packages, suchas pictured in Figure 2.19b, are commonlyused on planing hull type vessels andperformance craft.

However, as the size and power of enginesincreases, it becomes impractical to use verysoft resilient mounts directly under themarine gear. This is because the flexibility ofmore than 50 mm (2 in.) propeller shafts isnot adequate to accept large engine/marinegear motions [6 to 24 mm (1/4 to 1 in.)]without significant likelihood of damage to thestuffing box or the shaft bearings. It ispreferable to mount large engines on resilientmounts and mount the marine gear rigidly tothe structure of the boat. (This is a rule ofthumb. Special shafting arrangements, suchas cardan shaft with axial spline, or flexibilitymounted stuffing boxes will allow temperingof this guideline.)

When making this type of installation finalpositioning of the gear and engine is oftendone by adjustments of the resilient mountsthemselves. In any case, follow instructionsprovided by the mount manufacturer .

In resilient mount installations of gear andengine combined on common rails (Figure 2.19a), the following basic proceduresapply:

• The marine gear must be doweled orattached with body fitted bolts to thecommon rails.

• The engine, if not directly connected to themarine gear at the flywheel housing, mustbe aligned to the marine gear anddoweled, or fitted with a body fit bolt, atthe left or right rear of the engine.Note: This step may be done toward theend of the installation process.

• The common rails are then positioned onthe resilient mounts to be used and thepackage is aligned to the propeller shaftcompanion flange per previously outlinedprocedures. Appropriate shims or chocksare installed as required.

• Make sure propeller thrust or otherexternally applied forces areaccommodated in the mounting systemand limited by stops or other devices.(Refer to later sections in this documentregarding resilient mounts and shimtypes.)

Engine MountingThree Point Mounting of EnginesThree point mounting systems are normallyassociated with combined engine/marinegear units. There are, however, someinstances in which separately mountedengines will require the three point systemsuch as in high performance patrol craftwhere weight reduction and system flexibilityare premium factors.

The three point system for the enginenormally involves mounts on both sides at therear of the engine at the flywheel housingplus the trunnion mount at the front. Thisarrangement is very tolerant of flexing of theships mounting rails which may beencountered in light high speed craft. Hardmounts are used most often but resilientmounts are not uncommon with thisarrangement.

36

Mounting 3500 Family Enginesequipped with Mounting RailsWhen mounting engines in a vessel theeffects of external and thermally inducedstresses to the engine must be considered.This is a most important step in any qualityinstallation.

Ships hulls will flex under the internalstresses of varying displacement and theexternal stresses of wind, water, andtemperature. If the engine is too rigidlymounted to the ship’s structure, or if it isrestrained from its natural thermal growth,excessive stress may reach the blocks’internal support structure. This could in turnresult in distortion of main bearing bores,bore alignment, etc. Severe engine damage orsignificant reduction of engine life couldresult.

On the 3500 family of engines, as with otherCaterpillar engines, the main structuralstrength is the cast iron block. The plate steeloil pan which supports the engine is a deep,heavy weldment. Lugs or brackets are weldedto the sides of the oil pan for attaching thestandard mounting rails to the engine. Theserails, when properly mounted to the ship rails,provide the flexibility required to isolate theengine from the hull. The holes in themounting rails are located so that the rails areallowed to flex, isolating the ship’s deflectionfrom the engine.

These rails are also flexible enough toaccommodate thermal growth from side toside in most cases but provision for thermalgrowth front to rear must be allowed for.Under no circumstances should ground bodyanchor bolts be used forward of the engine’sflywheel housing.

Note: The steel oil pan to which themounting rails are attached expands at therate of about 0.0000063 in./in. for eachFahrenheit degree temperature change (or0.0000113 mm per Celsius degree).

Example: A 3516 oil pan experiences a rise intemperature from 65°F to 205°F, or 140 F degrees The distance from the fittedbolt at the rear of the rail to the forward mostclearance bolt is 80 inches. The expansion, orthermal shift at the forward clearance bolt, isthen:80 x 140 x 0.0000063 = 0.071 in.

The following basic steps may be followed inmounting 3500 family engines with factorysupplied mounting rails:

1. Preliminary . . . Marine gear in place,aligned to propeller shaft, and secured tofoundation. (Reference gear alignmentprocedure document and gear mountingprocedure in previous section of thisdocument.)

2. Prepare engine bed (foundations) forpoured or metal chocks. Foundation padsfor metal chocks should be flat, preferablyto within plus or minus 0.005 inchesflatness tolerance. Foundation pads forpoured chocks are less critical for flatnessbut should be placed for best chockthickness, i.e. 12.7 mm to 44.4 mm (.5 to 1.75 in.)

3. Place the engine on the foundation,supported by the jacking screws in therails, and at final aligned position by sight.Install side to side and fore to aftpositioning screws or devices per Figure 2.20. Align the engine to the gearper instructions in the previous document,Installation/Alignment Instructions.

37

4. If steel chocks are used, a solid chock isrecommended. Fit and install the metalshims at each of the four rail mountingpads according to the steel shim fittingand installation procedures outlined in theappendix.

It is not necessary to run the steel shimthe full length and width of the machinedpads incorporated with the 3500 familyengine rails. Smaller steel chocks areeasier to machine and fit. The shim’s areacan be considerably less as shown in theexample of Figure 2.21, but, they shouldencompass the two retaining bolts, whichare 152 mm (6 in.) apart, and cover at

least 19 of the 101 mm (.75 of the 4 in.)pad width. It is also a good rule of thumbto keep the applied unit pressure on softsteel shims under 34,475 kPa (5000 psi).

5. If poured chocks are used refer to theappendix for recommended installationprocedures for poured chocks.

Each machined mounting pad on the 3500family engine rails is about 589 cm2 (91.4 in2)in area, minus bolt and jacking screw area,and it is important to utilize all of the pad areawhen mounting on epoxy resin shims. This isespecially so for 3516 engines.

38

Mounting Bolt Locations (clearance)Fitted Bolt LocationsJacking ScrewsPositioning Screws

3500 Engine

Foundation Rail

Machined Mounting Pads (two per side)

MarineGear

TYPICAL SEPARATE MOUNTED ENGINE/GEARFOUNDATION PLAN

Figure 2.20

Jacking Screw

Machined Pad

Ship's Rail Retaining Bolts

Steel ShimMounting Rail

Mounting Rail

Machined Pad

SteelShim

Ship's Rail

3500

En

gin

e O

il P

an

Figure 2.21

The shim material can be poured at themounting pad locations only (an interruptedpour), or it can be used under the full lengthof the engine rail, except for immediately foreand aft of the machined mounting pads.

This is referred to as a continuous pourCaution: (Figure 2.22). In either case, do notpour shim material inboard of the machinedpad on the bottom of the mounting rail. Foamrubber strips must be installed on sides andboth ends of each pad to provide forexpansion. (Figures. 2.22 and 2.23).

Mounting Bolt Torques for use withPoured ShimsAfter the shim material has sufficientlyhardened according to the manufacturer’sspecification, tighten 22.2, 25.4, and 28.6 mm(7/8, 1 and 1-1/8 in.) mounting bolts to atorque of 490 N•m (360 lb ft). This bolttorque is specified to prevent excessive unitpressure on the poured shims.

Use two nuts on each mounting bolt. Tightenthe innermost nut to 490 N•m (360 lb ft.) UseFigure 2.24. in the appendix for torques of theoutermost nut.

Resilient mounting of 3500 FamilyEngines equipped with MountingRailsThis procedure will be addressed here only ingeneral terms due to the wide variation ofresilient mounting systems available. It is veryimportant that the resilient mountmanufacturer’s directions for installation andoperational limits be adhered to. Additionalgeneral information regarding soft mounts isincluded in the appendix.

The following factors are common to most orall resilient engine mount installations, and,should be carefully considered along with themanufacturer’s recommendations.

The resilient mounts are to be installedbetween the mounting pads of the rails andthe ship’s foundation. (Engine and gear oncommon rails was covered in an earliersection).

One or both of the rear mounts, nearest theflywheel housing, should be positively locatedto fix the engine relative to the marine gear.Positive location (doweling) of the enginemounting rail to these mounts will depend onmanufacturer’s instructions.

Positive stops for excessive vertical orhorizontal movement must be provided withor incorporated in the resilient mounts. Theseare required to limit relative engine motion

Foam Dams(for pour) Machine Pad

Mounting Rail

3500

En

gin

e O

il P

an

Ship's Rail

OuterDam

PouredChock

Figure 2.23

39

Machine pad

Ship's Rail

Jacking Screw

Retaining Bolts

Poured ChockFoam Dams (2)

3500 EngineMounting Rail

EXAMPLE OF CONTINUOUS POUR

Figure 2.22

due to inherent engine motion, misfiring, orvessel pitching and rolling.

Collision blocks or stops will be required, incase of collisions or grounding.

The flywheel mounted flexible coupling mustbe selected with care. It must routinelytolerate the ranges of side to side and fore/aft motions predicted for the given set of softmounts.

Similarly, all water, air, exhaust, hydraulic,control, and fuel system connections must beflexible enough to accommodate repeated,day to day movement without failure.

The foregoing applies to all soft mountedengine systems. If the marine gear, which isseparately mounted, is also on soft mounts,the prior section on soft mounted gearsshould also be reviewed for additional factorsof concern.

AppendixShims, Spacers, Chocks:GeneralShims, spacers, or chocks must be providedto fit the individual locations between the topsurface of the supporting members and thebottom surface of the mounting pads ofmarine engines and gears. MarineClassification Society (MCS) rules oftendictate the type of shim to be used. The twomost common and effective types will beaddressed here. They are: (1) poured epoxy(plastic) shims, and (2) solid steel shims.

Mounting With Poured Shims:Poured shims, or chocks, have become theshim of choice today in most mountingsystems for marine propulsion equipment.The advantages of poured shims over metalare several:

• The time consuming (and costly) processof selective machining and hand fitting ofsolid steel shims is avoided.

• The surface condition or flatness ofmating foundation and support planes isless critical, eliminating further machiningoperations in many cases.

• The plastic chocking material offers somedegree of noise damping between theengine or gear and the foundationmember.

• Zero shrinkage of the poured shimmaterial, when mixed and appliedproperly, allows the most preciseretention of position and alignment whenthe mounting procedure has beenproperly completed and the retaining boltssecured.

Before installing poured shims, consult themanufacturer’s instructions for using the shimmaterial. Strictly adhere to such critical itemsas mixing ratios, cure times, temperatureeffects, allowable thickness, and maximumunit loading. The basic steps in installingpoured epoxy shims are as follows:

1. Machine to be mounted is in final alignedposition with mating mounting structuresin proper place and condition. Thesemating pads should be of sufficientstrength and area, reasonably flat andparallel.

2. Liquid shim materials, dammingmaterials, blowers, grease) releasingagents, tools, etc. at hand permanufacturers recommendation.

3. Drill clearance holes through at allclearance bolt locations.

Note: It is recommended that holes forthe fitted bolts be drilled and reamedafter: the chocks have cured; theclearance bolts have been torqued; andalignment rechecked (in case the pourand alignment might have to be repeated).

4. Install the foundation hold-down boltsthreaded end up and with nuts hand tight.Sleeve or foam wrap the bolt shanks toprovide clearance for thermal expansionof the machinery. An optional method isto grease the bolt shanks with hightemperature (non melt) grease, then,remove the bolts and redrill the bolt holesfor adequate clearance after the chock hascured.

40

5. Spray all chock contact surfaces with asuitable releasing agent to preventadhesion of the chock to those surfaces.

6. Install damming material in preparationfor the pour. In this operation, considerthe following:

a. Ship’s trim . . . pour from the high endor from the side.

b. On non pour sides of the chock, damsof non porous foam material isrecommended. Use foam tape aroundedges of mounting pads to provide forpad movement during thermalexpansion of the machine or flexing ofthe foundation members.

c. Use rigid or semi rigid dammingmaterial around the pour area. Width ofthe pour area generally should notexceed 20 mm (.75 in.), and shouldprovide a riser of at least 12 mm (.5 in.).

7. Mix the resin and hardener for the chocksand make the pour per the resinmanufacturers instructions. Be sure toallow sufficient time for the chockingmaterial to cure.

8. After making sure of sufficient clearancearound clearance bolt shanks, torque allthe clearance bolt nuts to obtain total boltloading on the chocks equal to 2-1/2 timesthe weight of the mounted machinery butwithin the unit pressure limits for theindividual chocks as set by the resinmanufacturer. Unit pressure limits on thepoured chock are usually 3447 kPa(500 psi) when maintenance of machineryalignment is required, (as in the case ofpropulsion engines and gears). To aid indetermining the proper torque range the

following formulas may be used incalculating bolt loads:

Unit load on a given chock is obtained byfirst summing the weight from themachine plus any machine torque loadcomponent plus the total bolt load, all ofwhich is then divided by the chock area.

9. After the clearance bolts have beentightened, recheck for proper alignmentor position of the machine. (Keep in mindthat some slight shift is normal due tothermal effects on the ship’s hull,instrument variations and so on.)

10. If positioning is still satisfactory, install thefitted bolt or bolts.

11. Install the second set of nuts and torquethese against the first nuts per Figure 2.24. Be careful that the first, orprimary, nut is not torqued to a higherlevel than that determined in step 8. Markthe nuts with a paint spot to aid in futurepass by inspections for loose nuts.

12. Remove damming materials. Clean, dress,or chip away excess chock, wherenecessary, for appearance and to relieveany unintended restraint of the mountingpad.

Bolt Load (lb) = 60 3 Bolt Torque (lb ft)Bolt Dia. (in.)

Bolt Load (kg) = 500 3 Bolt Torque (kg m)Bolt Dia. (mm)

41

Full Torque Values

Dia (in.) .500 .563 .625 .750 .875 1.000 1.125 1.250 1.375 1.500

Torque(lb ft)

75± 10

110±15

150± 20

265± 35

420± 60

640± 80

800± 100

1000± 120

1200± 150

1500± 200

Figure 2.24

Mounting With Steel ShimsIdeally, steel shims, or chocks, are one pieceand are made to fit between the top of theship’s rail or machinery foundation and thebottom of the corresponding mounting pad ofthe engine or marine gear mounting rail orbracket. Mild steel plates are normally usedand are surface-machined to specificdimensions at each corner of the plate asdetermined when the engine or gear has beenplaced in the final aligned position. The shimscan be numbered to avoid confusion duringinstallation. The machining of these shimsmust provide a uniform fit between therespective machine rails or brackets and thefoundation pads.

To fit and install steel chocks the followingprocedures are suggested:

1. Foundation pads for metal chocks shouldbe flat, preferably to within 0.005 inchflatness tolerance.

2. With the machinery to be mounted in itsproper aligned position, measure thevertical gap between the pad andfoundation at each corner of the shimarea. If both the mounting pad andfoundation pad are flat, the four cornergap dimensions will dictate the cornerdimensions of the surface machined,finished shim.

3. To facilitate ease of fitting, the chock canbe slotted to fit around jacking screws.

4. Check the proper fit of each chock by useof blueing dye, carbon paper, strip gauge(plastigage), or feeler gauges. This is ajudgment operation by the fitter/installer.The objective is good even contact, (40%or more), over the major length and widthof the mounting faces. Do selectivegrinding or machining as required toobtain the proper fit.

5. When all of the chocks have been fitted,drill clearance holes for the retainingbolts, making sure of sufficient clearancefor thermal growth at all but the fitted boltlocations.

6. Install the bolts from the bottom up anddraw the nuts down moderately tight.

7. Recheck alignment of the machine. If thealignment is still satisfactory, torque thenuts on all clearance bolts per torquevalues as listed in Figure 2.24. Drill andream for the fitted bolt, or bolts, andinstall. Torque the nut on the fitted boltalso per Figure 2.24.

8. Install lock nuts on all bolts, torque, andmark with a spot of paint for future visualchecks.

MiscellanyWarning Against Lead Shims — Do notuse lead metal. Lead is easily deformed underweight and vibration and has poor supportingcharacteristics.

Warning Against Multiple Piece, SheetMetal Shims — Using hand cut, sheet metalshims, is discouraged. The edge deformationof the sheet metal shims, caused by the use ofhand sheet metal cutters (tin snips) willprevent a stack of such shims from lying flatand will eventually allow an engine, thusshimmed, to drop out of alignment, as itsshims relax. Also repeated, small, relativemovement between shims, along withinherent engine vibration may cause theshims to beat out, especially with 3500 familyengines and larger.

Mounting Bolts — There are two types ofmounting bolts:

Clearance bolts are nominally 1.5 mm (0.06 in.) diameter smaller than the holes inwhich they are installed. Clearance bolts areused to insure the engine does not movevertically on its foundation.

Fitted bolts have a tight fit in the holes inwhich they are installed. Fitted bolts,sometimes called ground body bolts, are usedto insure the engine does not move aroundhorizontally on its foundation.

Install both types of mounting bolts with thehead down and the threaded end up for ease

42

of routine periodic inspection of the boltedjoints.

One fitted bolt must be used at the rear of theengine to maintain position and alignment.Never use fitted bolts forward of theengines flywheel housing. Use clearancebolts in all locations forward of the flywheelhousing.

Resilient (Soft) MountsGeneralResilient mounts are used to reduce thetransmission of noise and/or vibration to thehull and various compartments of the vessel.This can have considerable effect on crew andpassenger comfort, reduced crew fatigue, andconsequent increased efficiency. It can evenaffect, to some extent, increased life ofequipment and machinery sensitive to hullborne vibration. However, in installingresilient mounting systems, the followingfactors must be considered:

Motion Limit DevicesAny resilient mounting system must includesome means of limiting the engine motion.Regardless of the type of mount, some meansof limiting the overall motion of the enginemust be present to prevent breaking theengines cooling and exhaust pipingconnections during bad weather or aftercollision/grounding accidents (when theengine might be subject togreater-than-normal inertia forces andmotions).

Softness Versus FrequencyAll noise/vibration has a frequency.

High frequencies*, such as those produced byturbochargers, gearing, and some hydraulicsystems, can be isolated by small amounts ofresilience.**

Lower frequencies, such as those producedby the firing of individual cylinders of theengine or driveline unbalance, require muchhigher amounts of resilience to achieve thebest reduction in transmitted engine vibration.

Types of Vibration MountsVibration mounts can be subdivided by thematerial of the resilient component. Spring

mounts which use helical metal springs,rubber mounts which use rubber, either inshear or compression, and Combined Springand Rubber Mounts-which use both methodsof achieving resilience. Some characteristicsof these mounts are:

Spring Mounts generally, will achieve thehighest amount of resilience. They are alsogenerally more costly. Even with springmounts, it is good practice to put some rubberin the mounting system. Mounts which useonly metal components can still transmitsignificant vibration/noise in the highfrequencies.

Rubber Mounts are excellent at isolating thehigher frequencies of enginevibration/noise—often better than the springtype. Rubber mounts are generally costeffective, as well. Rubber mounts requireperiodic inspection for hardening/cracking ofthe rubber elements.

Combined Spring and Rubber TypeVibration mounts combine the best of bothtypes.

Effects of Propeller Thrust onResilient MountsMost inexpensive vibration mounts aredesigned to accept forces in only onedirection, up-and-down. Propeller thrustforces are generally from the side. Make surethe vibration mounts chosen are suitable forthe forces to which they will be subjected.Install vibration mounts so the fore-and-aftthrust forces acting on the mount are resistedwith the least possible extension of themount.

Need for Periodic RealignmentVibration mounts can also settle or take aset—which can necessitate occasionalrealignment of the driveline. Annually checkalignment of engines mounted on vibrationmounts for misalignment.

* In the audible range of human hearing ** Amount of Resilience can be described in terms of the

motions of the engine. Engines whose mountingsystems permit only small motions—on the order of.5 mm. (0.020 in.) or less can be said to have only asmall amount of resilience.

43

Miscellaneous ConsiderationsCollision BlocksWhen marine classification societies or localmarine practice requires the use of collisionblocks, they should be located with sufficientclearance to allow for thermal growth of theengine. Prefabricate the collision blocks andinstall them while the engine is at operatingtemperature with approximately 0.12 mm(0.005 in.) hot clearance. Collision blocks arerecommended to resist the shock loadsencountered in hard docking collisions andgroundings.

Caution: Any electric arc welding ofscantlings (ships structural components) orengine support structures for engine ormarine gear requires precaution againstelectrical grounding through engine ormarine gear housings. Under no circumstancesis any welding of an engine or marine gear toits foundation to be done, otherwise, failurewithin the first few hours of operation is likelyto occur.

Crankshaft Deflection TestGeneral ProcedureTo assure the engine block is not undulystressed during mounting, a crankshaftdeflection test is recommended. This testshould be performed on 3500 family engines.Marine applications require this test beconducted under hot conditions. Toaccomplish this test, proceed as follows:

1. Remove an inspection door from the blockto expose the center crankshaft throw.

Rotate the crankshaft in the normalrotation direction. When the cheeks of thecenter throw just pass the connectingrods, install a Starrett No. 696 distortiondial indicator or similar tool. As aprecaution, tie a string to the gauge andsecure it outside the engine to facilitateretrieval should the assembly fall into theoil pan.

Zero the dial indicator’s rotating bezel.Properly seat the indicator by rotating iton its own axis until it will hold a zeroreading.

44

CRANKSHAFT DEFLECTION TESTFig 2.25

2. With the indicator still set at zero, rotatethe crankshaft in the normal direction untilthe indicator nearly touches theconnecting rods on the other side of thecrankshaft. (Do not allow the indicator totouch the connecting rod.)The dial indicator reading must not varymore than 0.3 mm (0.001 in.) throughoutthe approximately 300 degrees ofcrankshaft rotation.

Rotate the crankshaft back to its originalposition in the opposite rotation direction.The indicator must return to its originalreading of zero to make a valid test. If not,the indicator shaft points were not properlyseated and the test procedure must berepeated.

3. If the gauge reads more than 0.03 mm(0.001 in.), cylinder block distortion hasoccurred due to improper mounting.

Loosen the hold-down bolts between theengine rails and mounting blocks. Checkcarefully for loose shims, improperlocations of fitted bolts, interference fromclearance bolts, or any other constraints toproper engine block movement.

Make any needed adjustments and securethe hold-down bolts, making surealignment of the engine has not beendisturbed.

4. Repeat the distortion check procedure.Consult your Caterpillar dealer if theengine block is still bent.

45

AuxiliaryBasesAlignmentMounting Auxiliary Engines

This section is concerned with the mountingand alignment of auxiliary engines.

Auxiliary engines are power packages used toprovide onboard power to drive generators,pumps, compressors, winches, etc. Theengine driven equipment (load) is eitherdirectly mounted to the engine (closecoupled) or is remote mounted from theengine and driven through a shaft andcoupling. The major application of auxiliaryengines is to provide shipboard electricalpower. The following discussions, which referprimarily to engines driving generators, alsoapply to other types of auxiliary powerpackages.

The Caterpillar diesel auxiliary engine is builtas a rigid, self-supporting structure withinitself. If the engine is mounted on afoundation which is true (flat) or on a pair oflongitudinal beams, the tops of which are inthe same plane, the engine will hold its ownalignment. If subjected to external forces orrestrained from its thermal growth by themounting, affected tolerances may result inbearing or crankshaft failure.

The power module must maintain the originalalignment under all operational andenvironmental conditions. Misalignmentbetween an engine and driven equipment cancause vibration and shorten the life ofcoupling and bearings.

The major cause of misalignment is flexing ofthe mounting structure due to weakness.Other causes are poor installation methodsand incorrect alignment procedures.

BasesBase DesignThe most important function of an enginebase is rigidity. It must maintain alignmentbetween the auxiliary engine and its drivenequipment.

An engine base must:

• Protect the engine block, drive traincouplings, and load (generator gearreducer, or pump) from bending forcesduring shipment.

• Limit torsional and bending momentforces caused by torque reaction andsubbase flexing.

• Have a natural frequency such thatresonance does not occur during themachinery’s normal work.

• Make proper alignment easy. Allowsufficient space for shimming in thealignment process.

Ease of initial installation, vibration isolation,or need of isolating from a flexing mountingsurface are major reasons for use of fabricatedbases. No base of any type should be rigidlyconnected to a flexing surface.

The type of load will determine the designfeatures required in an engine base:

• If the load is close coupled—such as asingle bearing generator, the base issubjected to relatively light twisting loads.Its rigidity need only be moderate.

• But if the load is remote-mounted—suchas a two bearing generator, the base issubjected to far greater twisting loads andits rigidity must be very great.

Single Bearing LoadsWhen single-bearing generators or closecoupled loads are used, the base does nothave to withstand torque reaction. Bolting thegenerator housing to the flywheel housingeliminates the need for the base to absorb thedriving torque of the engine.

SingleBearing Generator(Close-Coupled Load)

Flywheel Housing toGenerator AbsorbsTorque Reaction

Figure 3.1

49

Two Bearing LoadsWith the load remote-mounted, a more rigidstructural base is required. The full loadtorque between the engine and load has to beabsorbed by the base without causingexcessive deflection in the coupling.

The stationary frame of the remote-mounteddriven equipment tries to rotate in the samedirection as the engine crankshaft. If the basewere not rigid enough, engine torque wouldcause the base to flex excessively. The resultis misalignment, proportional to the amount ofload, which will not show up during aconventional static alignment check.

Severe cases of this problem result in bearingand coupling failures.

Bases for Engines with Close-CoupledLoadsCaterpillar does not recommend a specificsection modulus for the longitudinal girdersor cross members. Usually “I” beams orchannel section steel beams in a ladder-typearrangement are acceptable.

Foot-Mounted EnginesBase cross members must be as substantialas the longitudinal beams.

Place the cross members beneath eachengine and generator support location.

Use drilled and threaded steel mountingblocks between the engine/driven equipmentand the base. Bolt these blocks to theengine/driven equipment first and then weldto the base providing a flat surface forshimming and mounting. Mounting holesdrilled into the structural members of thebase are not recommended.

There should be sufficient space forshimming between the mounting blocks andthe engine/driven equipment mountingsurfaces.

Flexible mounts are not allowed between themounting blocks and the engine/loadmounting foot surfaces.

TwoBearing Generator(Remote-Mounted Load)

EngineMovement

Crank Rotation

GeneratorMovement

Base Must MaintainAlignment AgainstTorque Reaction

Figure 3.2

50

Drilled and Tapped BlockEngine Supports

Drilled and Tapped BlockDriven Equipment Supports

BASE FOR FOOT-MOUNTED ENGINE WITH CLOSE-COUPLED LOAD

Figure 3.3

Rail-Mounted EnginesIn addition to the requirements for footmounted engines, the following applies forrail-mounted engines:

• The standard engine-mounted supportrails (engine length) must be usedbetween the engine and the structuralbase.

• Locate cross members directly beneaththe front and rear engine-to-rail mountinglocations.

• Place threaded mounting blocks at thefront and rear of the engine-mounted railswith space available for shimming. Boltthese blocks to the engine/drivenequipment first and then weld to the baseto provide a flat surface for shimming andmounting.

• Do not weld the engine-mounted rail tothe structural base.

• Bolt the engine-mounted rails to thethreaded mounting blocks throughclearance holes to provide for thermalgrowth.

51

Industrial-Type SupportRails

Driven EquipmentSupports

BASE FOR RAIL MOUNTED ENGINE WITH CLOSE COUPLED LOAD

Drilled and Taped Mounting Blockswith Shims

Figure 3.4

Bases for Engines withRemote-Mounted LoadsThe requirements for close-coupled loads alsoapply to remote-mounted loads. With the loadremote-mounted, a more rigid structural baseis required. The full load torque between theengine and load has to be absorbed by thebase without causing excessive deflection inthe coupling.

The base shown above is a boxed beamdesign which provides a torsionally rigid base.

Boxing consists of welding steel plates on topand bottom surfaces of machinery basegirders. The plates should be 5 to 7 mm (3/16 to 1/4 in.) thick. Skip-weld the plates toprevent excessive base distortion duringwelding. Boxing is done to make the basestructure stiffer.

The additional stiffness is necessary to resisttorque loads between the engine andremote-mounted driven equipment and toresist possible vibration loads. Vibration-induced base loads are difficult to predict.

Experience has shown boxing is effective inpreventing base cracking and misalignment.

Recommended Beam HeightThe recommended heights of the longitudinalbeams for the various engine generator setsare:

AlignmentIn high speed applications, at normaloperating temperatures and load,misalignment between the diesel engine andall mechanically driven equipment must bekept to a minimum. Many crankshaft andbearing failures can be traced to incorrect

EngineModel

Metricmm

Beam Height

Englishin.

3304, 3306 200 8

3406, 3408 260 10

3412 300 12

3508 400 16

3512 450 18

3516 500 20

52

Drilled and Tapped BlockDriven Equipment Supports

Drilled and Tapped BlockEngine Supports

Skip Welded Boxing Plateson Top and Bottomof Base

BASE FOR ENGINES WITH REMOTE MOUNTEDDRIVEN EQUIPMENT

Figure 3.5

alignment of the drive systems. Misalignmentat operating temperatures and under load willalways result in vibration and/or stressloading.

Since there is no accurate and practicalmethod for measuring alignment with theengine running at operating temperature andunder load, all Caterpillar alignmentprocedures must be performed with theengine stopped and the engine and all drivenequipment at ambient temperature.

For information on alignment principles andthe use of dial indicators, please refer to theMounting and Alignment section underpropulsion engines in this manual.

Refer to the following Caterpillar SpecialInstruction for more detailed information andspecific instructions on mounting andalignment procedures.

Alignment of Remote-Mounted DrivenEquipmentIn order to achieve correct operatingalignment, certain factors must be taken intoconsideration in determining cold alignmentspecifications.

Factors Affecting AlignmentThe input shaft of remote-mounted equipmentis always positioned higher than the enginecrankshaft. This compensates for verticalthermal growth, flywheel sag, and mainbearing oil film lift on crankshaft. Thesefactors cause the relative positions of thecrankshaft and load input shaft to shiftbetween static and running conditions.

Bearing ClearancesThe generator rotor shaft and enginecrankshaft rotate in the center of theirrespective bearings, so their centerlinesshould coincide. Alignment is made understatic conditions while the crankshaft is in thebottom of its bearings. This is not its positionduring operation. Firing pressures, centrifugalforces, and engine oil pressure all tend to liftthe crankshaft and cause the flywheel to orbitaround its true center. Generally, the drivenequipment will have ball or roller bearingswhich do not change their rotational axisbetween static and running conditions.

Form No. Title

SEHS7654 Alignment - General Instructions

SEHS7259 Alignment of Single BearingGenerators

SEHS7073 Alignment of Two-BearingGenerators

53

Position of CrankshaftDuring Cold Alignment

Position of CrankshaftDuring Operation

BearingBore

CrankshaftStatic

ClearanceRunning

Clearance

Figure 3.6

Flywheel SagWith the engine not running, the weight ofthe overhanging flywheel and coupling causesthe crankshaft to bend. This effect must becompensated for during alignment since itresults in the pilot bore and outside diameterof the flywheel rotating lower than the truecrankshaft bearing centerline duringalignment. Caterpillar recommends alignmentchecks be performed with the coupling inplace.

Torque ReactionThe tendency of the engine to twist in theopposite direction of shaft rotation and thetendency of the driven machine to turn in thedirection of shaft rotation is torque reaction. Itnaturally increases with load and may cause atorque vibration. This type of vibration willnot be noticeable at idle but will be felt withload. This usually is caused by a change in

alignment due to insufficient base strengthallowing excessive base deflection undertorque reaction load. This has the effect ofintroducing a side to side centerline offsetwhich disappears when the engine is idled(unloaded) or stopped.

Thermal GrowthAs the engine and generator reach operatingtemperatures, expansion or thermal growthwill occur. This growth is both vertical andhorizontal. The vertical growth increases thevertical elevation between the componentmounting feet and the respective centerlinesof rotation. This thermal growth depends onthe type of metals used, the temperature risethat occurs, and the vertical distance from thecenter of rotation to the mounting feet.

Crankshaft horizontal growth occurs at theopposite end of the engine from the thrustbearing. The location of thrust bearings onCaterpillar Engines is at the rear of thecrankshaft. This growth has to be planned forwhen driven equipment is connected to thefront end of the engine. The growth is slight ifthe driven equipment is bolted to the engineblock, since the block and crankshaft grow atapproximately the same rate. An example ofthis would be a front power takeoff clutch.

End ClearanceHorizontal compensation consists of using acoupling with sufficient end clearance thatallows relative movement between the drivingand driven members. The equipment must bepositioned so the horizontal growth movesinto the coupling operating zone, not awayfrom it. Failure to do so will result inexcessive crankshaft thrust bearing loadingand/or coupling failure. Sufficient clearancehas been allowed if it is determined duringhot alignment check that the crankshaft stillhas end clearance.

Cat Viscous Damped CouplingCaterpillar couplings use an internal geardesign with a rubber element between thegears. Silicone grease aids in the dampeningcharacteristics.

The clearances involved in internal geardesign allow accurate alignment measurement

(Exaggerated)

CouplingFlywheel

Crankshaft

Figure 3.7

54

to be made without removing the rubberelement.

The coupling for front-driven equipment issimilar to the rear-drive coupling illustratedbelow. On front drives, the driven elementshown in Figure 3.8 is to be supported on theengine crankshaft as it does not weigh asmuch as the driving element.

Other CouplingsThe flexible element of other couplings mustbe removed during alignment checks.Element stiffness can prevent accuratealignment readings.

With the coupling element removed, thedriving and driven members of the couplingshould be rotated together during alignmentchecks. This prevents face or bore runout ofthe piece parts from affecting the dialindicator readings. When both members arerotated together, only equipmentmisalignment will register on the dialindicator readings.

55

ThrustBearing

RearDrivenUnit

Driven UnitSupports

FlywheelHousing

Driveshaft FlexibleCoupling

Engine

Engine

HorizontalThermal growth

HorizontalThermal growth

EngineMounting Rail

Coupling Clearance

FrontDrivenUnit

Driven UnitSupports

Flexible Coupling

ThrustBearing

EngineMounting Rail

Figure 3.8

Fig. 3.9

Mounting AuxiliaryEnginesThe proper engine mounting system willensure the dependable performance and longlife for which the engine was designed andmanufactured if all equipment is properlyaligned.

The engine should be mounted on a pair oflongitudinal beams, the tops of which are inthe same plane. If the tops of the beams arenot fiat, add sufficient shims between theengine mounting surface and the mountingbeams. Bolting the engines to an unevensurface can cause harmful distortions in theengine block, springing of the mountingbeams, and high stress in welds or basemetal.

If the engine is subjected to external forces,or if restrained from its natural thermalgrowth, tolerances are greatly affected andcould easily result in bearing or crankshaftdamage.

Three-Point MountingThe three-point suspension system should beused when there is a possibility that thesubstructure supporting the base can deflectdue to external forces or settling. Suspendingthe power unit on three points isolates theunit from deflection of the substructure, thusmaintaining proper relationship and alignmentof all equipment and preventing distortion ofthe engine block. More than three mountingpoints can cause base distortion (Figure 3.10.)

Objectionable vibration can occur if the powermodule is not mounted on well supportedstructures or is not anchored securely. Inaddition to the three-point mounting, vibrationisolators may be required to isolateobjectionable vibrations.

Anti-Vibration MountingCaterpillar Engines are capable ofwithstanding all self-induced vibrations and noisolation is required merely to prolong theirservice life. However, vibrations fromsurrounding equipment, if severe, can harm agenerator set which is inoperative for longperiods of time. Bearings and shafts can beatout and ultimately fail if these vibrations arenot isolated. A running generator set willrarely be harmed by exterior vibrations. Themethod of isolating the unit is the same forexterior vibrations as it is for self-inducedones.

Caterpillar recommends the use of flexiblemounts on all auxiliary engine installations.Refer to Vibration and Isolation section forinformation on types of vibration and isolationprinciples.

Some new generator packages have factoryinstalled vibration isolators. refer to the PriceList to determine if they are standard oroptional.

Sources of Disturbing VibrationsVibrations affecting auxiliary engines may beclassified into four groups:

• Propulsion engines.

BaseDistorts

Base Rotates

DistortingForce

Figure 3.10

56

• Propeller-induced vibration caused by thepropeller blades passing the hull, strut, orskeg.

• Twin or multiple screw propulsioninstallations running out of phase wherevibrations will occur at frequenciesdepending on the differences in enginerpm.

• All first order vibrations caused by otherengines and installed pumping equipment.

Vibration Limit (No Load)The acceptable no load vibration limit forCaterpillar Engines is 0.1 mm (4 mils) peak topeak displacement for the engine only and0.13 mm (5 mils) for engine and drivenequipment.

ProtectionIn order to protect marine auxiliary engines,flexible spring-type mounts should beinstalled between the base and the ship’sstructure. Caterpillar and others can supplyflexible mounts. To obtain the correct flexiblemount, the supplier must know whatprotection is required.

Selecting Flexible Mounts• Contact a suitable supplier and provide

him with:

– Equipment configuration and basedrawing.

– Expected frequency of the forcingvibrations.

– Weight and center of gravity of theauxiliary unit to be isolated.

• To be effective, static conditions must loadisolators close to the center of theiroptimum deflection range. Therefore, theweight that will rest on each isolator mustbe known and the isolators properlymatched to the load.

• When using resilient materials in additionto spring-type mounts, select the lowestpsi loading which gives the highestpercentage reduction in transmittedvibration.

• Several types of resilient pads isolatenoise but not vibration. Some may evenamplify first order vibrations. As a generalrule, resilient mounting pads should haveat least 6 mm (15/64 in.) static deflection;less than this results in reduced noise, butlittle or no vibration isolation. Consult thesupplier for specific information.

Very Low Frequency VibrationVibrations at frequencies of 5 Hz and beloware difficult to isolate.

The supplier of the flexible mounts is anexcellent source for specificrecommendations for very low frequencyvibration mounting.

Installation of Flexible MountsFlexible mounts must be placed between thestructural base of the auxiliary unit and theship’s structure. It is important that the basebe of substantial design. When the shipstructure is not sufficiently rigid, reinforcingsupports should be added. When placingflexible mounts, the directions of the suppliershould be followed.

The location of isolation mounts is important.On larger engines requiring three pairs ofmounts, install one pair of isolators under thecenter of gravity and the other two setsequidistant from them at each end ofstructural base (Figure 3.11).

X X

CG

Figure 3.11

57

On smaller engines requiring only two pairsof mounts, locate one pair under front enginesupports and the other pair under loadsupports.

For three-point mounting of the engine base,arrange the isolators to obtain three pointcontact with the load equally distributed.

Determination of Center of Gravity ofCombined Engine and GeneratorThe location of the center of gravity of theassembled unit can be determined after thetotal weight of the unit is established.

Assuming an engine and generator isassembled to a base, the assembled center ofgravity (CG) can be calculated. A commonreference point is needed. In this case, usethe rear face of the flywheel housing. Becausemeasurements are to both sides of thereference, one direction can be considerednegative. Therefore:

If additional equipment is added, such as frontpower take-off, the process is repeated todetermine a new center of gravity.

Having established the center of gravity forthe total unit, the loading on each pair ofisolators can be determined (Figure 3.15).

The location of the center of gravity of theassembled unit can be determined after thetotal weight of the unit is established.

S1 = WT ( )bc

S2 = WT ( )ac

WT (D) = WG (– d1) + WE (d2)

D = (WE(d2) – WG(d1))WT

Figure 3.14

d1 d2D

CG

WTWG

WE

Figure 3.13

Figure 3.12

58

Commercial IsolatorsSeveral commercial isolators are availablewhich will provide varying degrees ofisolation. Care must be taken to select thebest isolator for the application. Generally thelower the natural frequency of the isolator(softer), the greater the deflection and themore effective the isolation. However, theloading limit of the isolator must not beexceeded.

Rubber IsolatorsRubber-type isolators are adequate forapplications where vibration control is notsevere. By careful selection, isolation of 90% ispossible. They will isolate most noise createdby transmission of vibratory forces. Care mustbe exercised to avoid using rubber isolatorswhich have the same natural frequency as theengine-exciting frequencies in both thevertical and horizontal planes.

Fiberglass, Felt, Composition and FlatRubber (Waffle) IsolatorsFiberglass, felt, composition and flat rubber ofa waffle design do little to isolate majorvibration forces, but do isolate much of thehigh frequency noise. The fabric materialstend to compress with age and becomeineffective. Because deflection of these typesof isolators is small, their natural frequency isrelatively high compared to the engines.Attempting to stack these isolators or applythem indiscriminantly could force the totalsystem into resonance. Pad-type isolators areeffective for frequencies above 2,000 Hz.

Spring IsolatorsThe most effective isolators of low frequencyvibration are the steel spring type. These canisolate approximately 96% of all vibrations.They also provide overall economy and allowmounting, of all but propulsion machinery, onsurfaces that need only support the staticweight. No allowance for torque or vibratoryloads is required on nonpropulsionmachinery. Steel spring-type isolators areeffective in the vibration frequency rangefrom 5 to 1,000 Hz.

Marine-type spring isolators should be usedfor auxiliary engine mounting. This type ofisolator is equipped with all directional limitstops designed to restrict excessivemovement of the engine and to withstandforces due to roll, pitch and slamming ofsea-going vessels.

By the addition of a rubber pad beneath thespring isolator, the high frequency vibrationswhich are transmitted through the spring arealso blocked. These high frequency vibrationsare not harmful but result in annoying noise(Figure 3.17).

Follow the installation and adjustmentinstructions provided by the isolator supplier.

Many spring type isolators are equipped withhorizontal limit stops (snubbers) but do notinclude built in vertical limit stops. If this typeof isolator is used, external vertical limit stopsshould be added between the engine rail, orsupport, and the ship’s engine bed.

Isolator snubbers and limit stops should beadjusted to permit only the amount of motionnecessary for isolation purposes.

No matter what type of isolation is used, itshould be sized to have its natural frequencyas far removed from the exciting frequenciesof the engine as possible. If these twofrequencies were similar, the entire unitwould be in resonance.

Flexible ConnectionsWhen using the marine spring isolator,ensure that each pipe, control system,electrical, and driveline connection is properlydesigned to allow for maximum engine

S1 S2

CG

WT

Figure 3.15

a bc

59

motion without overstressing any of theconnecting components.

Collision BlocksAll spring-mounted equipment should havestops to restrict vertical and side movementwithin reasonable limits. Collision blocks maybe provided for all auxiliary engineinstallations if they do not restrict thermalgrowth.

ShimmingUse shims as necessary between thegenerator mounting feet and the generatorsupports to maintain correct verticalalignment with the engine. All generator

mounting feet must be in solid contact withthe supports before installation of the anchorbolts. If the mounting feet are not in solidcontact, distortion of the generator housingcan result.

Shim packs under all equipment should be 5 mm (0.2000 in.) minimum thickness toprevent later corrections requiring theremoval of shims when there are too few orzero shims remaining.

Shim packs should be of nonrusting material.Handle shims carefully.

60

Engine Rail

Rubber Pad

EngineBed

HorizontalSnubber

VerticalLimit Stop

MARINE-TYPE ISOLATOR

Figure 3.16

VibrationIsolator

Rubber Pad

SPRING ISOLATOR WITH EXTERNAL LIMIT STOP

Internal AdjustingScrew

EngineRail

VerticalLimitStop

EngineBed

HorizontalSnubber

Figure 3.17

Mounting BoltsThe diameter of the clearance-type bolts usedto hold the engine rails or feet to the basemust be 1.6 mm (0.06 in.) less than thediameter of the holes in the engine rails. Thisclearance is to allow the engine mountingrails or feet to grow without confinement.Refer to the section on thermal growth.

Mounting Bolt LocationEach engine or generator mounting bolt must bolt through solid material (refer toFigure 3.18).

Procedure for Tightening EquipmentMounting Bolts1. Torque mounting bolts in sequence shown

in Figure 3.19 to 1/2 torque values listed.

2. Install a dial indicator on support bracketas if bore alignment were to be checked.Rotate driving and driven shafts togetheruntil dial indicator is at top position.

3. Loosen bolts at mounting surface 1 andretorque bolts at mounting surface 3 to1/2 torque value as listed in Figure 3.19.

4. If indicator moves 0.05 mm (0.002 in.) orless, retorque bolts at mounting surface 1and follow steps 6 and 7 below. If indicatormoves more than 0.05 mm (0.002 in.), addshims under bolts at mounting surface 1or 3. Loosen all bolts and repeat steps 1through 5.

5. Loosen bolts at mounting surface 2 andretorque bolts at mounting surface 4 to1/2 torque value listed.

6. If indicator moves 0.05 mm (0.002 in.), orless, retorque bolts at mounting surface 2.If indicator moves more than 0.05 mm(0.002 in.), add shims under bolts atmounting surface 2 or 4. Repeat steps 1thru 6.

7. With indicator and support bracket still attop position, retorque all bolts to fullvalues. Reading should not change morethan 0.05 mm (0.002 in.).

Bolt TorqueA bolt is properly torqued when it is stretcheda calculated amount. The proper stretchclamps the machinery to the base securely.The clamping force is then maintained duringmovement caused by vibration(refer to Figure3.20). A bolt that is undertorqued cannotmaintain the clamping force while vibrationsare present. It will gradually work loose andallow misalignment to occur.

Bolts of the size used on Caterpillar basesrequire very high torque values. As anexample, a 25.4 mm (1 in.) bolt has a torqueof 868±108 N•m (640±80 ft lb).

A torque wrench, extension and torquemultiplier are required to obtain this highvalue. Do not use special bolt lubricants as theeffective bolt clamping force can be excessive.

61

Proper Practice

Improper Practice

Figure 3.18

Caterpillar nuts and bolts are made of Grade 8steel, one of the strongest available. They areidentified by six raised or depressed lines onthe nut or bolt head. Make sure mountingbolts are not bottomed out in hole, resultingin low effective bolt clamping force.

After completion of the final shimming andbolting operation, recheck the alignment.

Crankshaft DeflectionCrankshaft deflection must be measured bothcold and hot on certain specified engines. Theallowable deflection must not exceed0.025 mm (0.001 in.). Deflection must bemeasured at the center crankshaft throw. SeeMounting and Alignment section for detailson crankshaft deflection.

Bolt Stretch(Exaggerated)

ClampingForce

Figure 3.20

62

2

3

4

MountingSurface

1

Full Torque ValueTorqueBolt Diameter

mm3/4 Inch 197/8 221 Inch 25

lb-ft265 ± 35420 ± 60640 ± 80

N m360 ± 50570 ± 80875 ± 100

Note: *Number near each mounting surface represent proper bolt tightening sequence.

*Procedure described is valid for all independently mounted equipment. i.e., engine, two bearing generator, remote mounted marine transmission, etc.

Figure 3.19


● Control Systems

● Instrumentation and MonitoringSystems

● Starting Systems

● Start-up Systems

● Serviceability


Control SystemsGeneral InformationEngine Stall and Reversal

General InformationThe use of a reliable control system isessential. The controls must be precise,dependable, and easy to operate.

The control system, in its most basic form, isthe equipment which allows the pilot to adjustthe propulsion engine/s throttle (speed) andthe marine gear’s clutches—from neutral toahead or astern.

To control throttle setting, a control systemmust rotate and hold the angular position ofthe governor control throttle.

To effectively control the marine gear withmechanically actuated hydraulic controlvalves, a control system must move a shortlever on the hydraulic control valve to any ofthree positions (forward, neutral, reverse) andmaintain the selected position without placingundue stress on the linkage or allowing thelever position to creep.

To effectively control the marine gear withsolenoid-actuated hydraulic control valves, anelectrical signal energizes one of twosolenoids to pressurize either the forward orastern clutch. If neither solenoid is energized,the gear remains in neutral and neither clutchis pressurized.

Basic System FeaturesTwo Lever ControlTwo lever control systems use two levers forthe pilot’s control of the engine and themarine gear, hence the name.

The position of one of the levers determinesthe engine throttle setting.

The position of the other lever determines thetransmission direction—neutral, astern, orahead.

Two lever control systems are mostsimplified, and most economical, but have thepossibility of changing the transmissiondirection while the engine is at a high throttlesetting. Transmission clutch damage is likelyif this occurs.

Single Lever ControlSingle lever control systems provideautomatic sequencing of the control functions,preventing the transmission from changingdirection until the throttle lever is moved tothe neutral position (refer to Figure 1.1).

Neutral ThrottleNeutral throttle allows independent speedcontrol when the marine gear is in neutral.This feature is useful when controlling thespeed of engine-driven accessories such asgenerators, pumps or winches.

Multiple Control StationsAll vessels require one control station wherethe pilot controls engine and transmission. Itis convenient to have other control stationswhen specific activities, such as docking andfishing, demand the pilot’s close attention.

The simplest and, in most cases, mostefficient multiple (dual) station systemconsists of two lever controls installed in aparallel system. Cables are run from thecontrols at each station directly to the clutchand throttle levers at the engine, andconnected there with the appropriate paralleldual station kits.

A second type of multiple (dual) stationsystem consists of two lever controls in series.Cables are run from the upper control stationto the lower control station. A cableattachment kit is required to connect thesecables to the lower station controls. Cablesare then run from the lower station controls tothe clutch and throttle levers at the engineand connected there with the appropriate

Figure 1.1

NeutralIdle

Full Reverse Full Forward

SINGLE LEVER CONTROL

Reverse

Idle

ForwardIdle

Incr

ease

Thro

ttle

Increase

Throttle

ShiftReverseShift

Forward

1

engine connections kits. Series installationsare less precise than parallel systems andshould be used only when a parallelinstallation would be impractical due to longcable runs and excessive or sharp bends inthe cable. The system selected is determinedby the cable length and total degrees of cablebend required.

Engine/Gear Mounted BracketDesignBrackets supporting the control systemscables/actuators at the engine/marine gearmust be rigid. Good alignment of the cable-ends with the engine’s throttle lever andgear’s clutch control lever is necessary toavoid binding. Control system manufacturerscan provide suitable brackets to theuser/installer.

TypePush-Pull Cable SystemPush-pull cable control systems are reliableand economical. The distance between thecontrol head at the pilot station and theengine is limited by friction in the cables.

For best results, keep cable length under 30 ft.

The number and included angle of bends inthe control cables add significantly to theirinternal friction. Avoid all unnecessary bends.Keep all bends in the cables as gradual aspossible (minimum 200 mm [8 in.] bendradius).

Stiffness or binding in the operation of thehand lever can usually be traced to:

• Excessive number of bends in cable runs• Sharp bend in the cables too close to the

control head• Bends smaller than the recommended

minimum radius of 200 mm (8 in.)• Tight or misaligned engine linkage• Cable compressed too tightly by cable

support• Engine clutch lever hitting its limit stops at

forward and/or reverse

Figure 1.3

MT CONTROL SYSTEM

ClutchConnection Kit(to suit gear)

ThrottleConnection Kit(to suit engine)

Figure 1.2

TWIN S CONTROL SYSTEM

ClutchConnection Kit(to suit gear)


2

The installation of push-pull cable controlsystems is fairly simple.

Manufacturers’ installation bulletins for bothtwo-lever (Figure 1.2) and single-lever lever(Figures 1.3 and 1.4) systems illustrate thesystems.

Cable-in-Tension SystemWhere a cable control system is preferred andlong runs and numerous bends may beencountered, a system is used utilizing twocables in tension, running over pulleysmounted on antifriction bearings (refer toFigure 1.5). To reduce the number of cablesand to maintain precision in the response ofthe system, a single lever type of controlsystem is used. A control gearbox to thegovernor and reverse gear is installed on theengine.

Hydraulic Control SystemHydraulic controls offer smooth, precisecontrol of engine/marine gear withoutsignificant limitation on number of controlstations or distance between control stationsand the engines. The cost of hydrauliccontrols and the number of installationmanhours are slightly higher than either ofthe mechanical cable controls.

Electronic Control SystemElectronic control systems should beconsidered when the following controlrequirements are encountered.

• Electronically controlled engines• Limiting the engine power during

acceleration• Engine overload protection• Integration with controllable pitch propeller

control systems• Sharing of load between multiple engines,

driving a single load• Very long distances between the control

station and the engine• Integration with telemetry systems• Adding additional control stations after

vessel completion

Control Head Neutral Throttle

Shut-Off

3"—4

1"—8

E.M.T. Conduit

Adjustable Elbow

StrutFixed Elbow

43C CableGear Kit

Throttle Rod

Spring Link

Control Unit

Roller Chain

Turnbuckle

Cable Clamp

Wire Rope

Terminal Block

Neutral ThrottleCable

Shut-Off Cable

MD 24 CONTROL SYSTEM

Figure 1.5

MK ControlHead

Turnbuckle

Chain, ConnectorsCable Clamps & Strut

To RemoteStation


Connection Kit(to suit transmission) Push-Pull Cables

MK CONTROL SYSTEM

Figure 1.4

3

Electronic Control SystemComponents Control StationThe control station is generally simpler than asimilarly functioned mechanical or hydraulicversion. The forces involved in drivingrheostats and switches are much less thanthose to operate push-pull cables or hydrauliccylinders. Electric control stations are veryeasy to install.

Most electric control systems will install anelectric-to-mechanical converter box in theengine room/compartment. Theelectric-to-mechanical converter box acceptselectrical signals from the various controlstations and converts them to mechanicalforces (generally via push-pull cables),suitable to operate the engine throttle andmarine gear shifting valve. On newermechanically controlled engines, controlsystems are capable of using electronicengine governors and electric marine gearcontrol valves which eliminate the need forthe electric-to-mechanical converter box.

Engine Throttle and Marine GearActuatorSee electronic installation guide for electroniccontrolled engine.

3126B RENR22333176B SENR64893176C SENR11873196 SENR11873406E SENR11873408 SENR6446 (PEEC)3412 SENR6446 (PEEC)3412E SENR5014

Mather’s, ED Electric, Sturdy, Twin Disc andKobelt are control manufacturers that canprovide fully electronic control packages withour electronically controlled engines. Theyhave electronic controls that areprogrammable for shifting and provide anelectronic signal compatible with Caterpillarelectronic engines.

Control LogicGenerally, the control logic is contained in theelectric-to-mechanical converter box in theengine room/compartment. Larger systemswill combine the logic circuitry with apropulsion system monitoring system in acabinet in the engine room.

System ConnectorsElectric control systems are generallyinterconnected by multiconductor electricalcable. This is much less expensive thanmechanical cable or hydraulic tubing.

Pneumatic Control SystemPneumatic controls offer several advantagesover other control systems:

• Ability to control engines at long distances.90 m (300 ft) is a realistic distance to runair lines for pneumatic control. The onlyreal limitation is the speed of response–inthe case of very long lines.

• Ability to control from an unlimited numberof control stations.

• Ability to add logic to the system, to protectagainst abuse of the driveline components.

• There are some disadvantages topneumatic control systems:

• A relatively heavy and expensivecompressor with air storage tank isrequired.

• The tank and lines require regularmaintenance (draining of condensation).

Engine Stall and ReversalWhen a marine reduction transmission isshifted from forward to reverse or vice versa,sufficient engine torque must be available atidle speed to overcome propeller and drivelineinertia, marine transmission inertia, and slipstream torque*.

If sufficient torque is not available or ifsufficient engine safeguards are not installed,the engine will stall or reverse itself.

In vessels where rotating masses aremoderate to small, clutch modulation andengine torque can control the reversing cycle.Heat buildup caused by the clutch slipping isnormally well within the clutch capacity. Heatgenerated through increased modulationnecessary to control large inertia forces candamage clutches. To prevent this buildup ofheat, auxiliary devices may be necessary.

* Slip stream torque is the torque generated in afree-wheeling propeller, being turned by the waterflowing past the hull. Slip stream torque can be as highas 75% of the engine’s rated torque.

4

Also, under crash reversal conditions, it isconceivable that unless some device is usedto counteract the inertia of large masses, theengine could stall or actually be motorized torun in reverse rotation.

Avoiding engine stalling and/or reversal withmechanical controls is difficult. One methodis by careful clutch engagement and byallowing the boat to slow down before theshift is made. The adept operator canrepeatedly engage and disengage thereversing clutch, until the vessel’s speed ischecked sufficiently, and then complete themaneuver. Where large, heavy vessels, orthose attached to a tow are concerned, thismethod may cause overheating of the reverseclutch. When this danger exists, other meansmust be employed.

Engine stalling and reversal problems can beavoided if close attention is paid to the engineand transmission control system.

Pneumatic and electronic controls whichprovide sequencing and timing of speed anddirectional signals offer optimummaneuvering as well as protection for theengine and transmission.

When Engine Stall and ReversalCould Be a ProblemThe likelihood of this being a problem issignificantly increased for vessels equippedwith:

• Propulsion engines producing over 500 hp• Fixed pitch propellers• Deep ratio reduction gears, usually 4:1 and

deeper

What the Operator Can DoLoss of acceptable engine speed can beprevented by prudent use of the controls bythe operator during maneuvering.

Engine Speed Limits DuringEmergency ManeuversIt is imperative that engine speed does notdrop below 300 rpm for slow speed engines(rated at nominally 1200 rpm) or 400 rpm forhigh speed engines (rated at nominally 1800 to 2300 rpm) in order to assure adequate

lubrication and to prevent the possibility ofstalling.

Need for Sequencing ControlSystemsSequencing and timing of the controls whenusing air control systems is necessary to:

• Reduce vessel maneuvering time• Prevent excessively low engine speed• Prevent excessive loading of driveline

components• Reduce the possibility of engine stalling

The possibility of engine speed reduction tothe point of stalling due to sudden vesselmaneuvering demands will be dependentupon the speed of the vessel when themaneuver is undertaken. During low vesselspeed maneuvers, the engine torquecapabilities are usually sufficient to respondadequately. However, if a sudden maneuver,such as a crash stop of the vessel, isdemanded at full vessel speed, auxiliarydriveline devices may be required to preventstalling and loss of vessel control.

Sequencing Control SystemFeaturesTo forestall the possibility of engine stallduring high speed maneuvers in emergencysituations, one or more of the following maybe required:

• Raised low idle speed setting• Throttle boost control• Shaft brake• Control system timing

3500 Family Engines equipped with 3161governors will shut off their fuel if subjectedto engine reversal.

Raised Low Idle Fuel System SettingTo increase the engine's low speed torque,the low idle setting may be increased if thevessel's low speed maneuvering is notjeopardized. This will help prevent the enginefrom stalling or reversing during maneuver.The setting should be accomplished by anauthorized Caterpillar Dealer. Excessiveshock loading and transmission clutch wear

5

can occur if the engine low idle speed is toohigh.

Throttle BoostThrottle boost momentarily raises the idlingspeed setting of the engine. The engine speedincrease comes just before engagement of themarine gear clutch. This momentary speedincrease occurs only during maneuvering, notat steady boat speed conditions.

Throttle boost is kept as low as possiblebecause it tends to increase the load on theclutches during maneuvering. The controlsystem should permit adjustment of both theamount and duration of throttle boost. Thethrottle boost for most Marine Gears shouldbe set no higher than 750 rpm for 1800 rpmengines and 600 rpm for 1200 rpm engines atno load. Sea trials should determine the levelof throttle boost necessary to ensure a safeshaft reversal and maintain engine speedabove the minimum limits. Consult themarine transmission manufacturer forboosted-shift clutch capability.

Although reversing problems seldom occurwith marine transmissions ratios moreshallow than those previously mentioned, it isrecommended that a throttle boost system beincorporated with more shallow ratioedtransmissions as an additional safety feature.

Shaft BrakeIn vessel applications where heavymaneuvering is required or if full speedreversals may be encountered, the use of apropeller shaft brake is recommended. Aproperly controlled shaft brake will stop therotation of the propeller whenever thetransmission clutches are disengaged and theengine is at low idle speed. This actionreduces the amount of torque required fromthe engine in order to complete a shaftdirectional change. Several advantages aregained with the use of shaft brakes.

1. A propeller shaft brake can safely reducevessel maneuvering time. A vessel willslow in half the time with a stoppedpropeller as compared to a windmillingpropeller. The propeller slip streamtorque, therefore, falls to a level lowerthan the slow speed torque of the enginein half the time.

2. The propeller shaft brake accepts half thespeed reversal loads when maneuvering.The brake brings the propeller to a stop.This load is transmitted directly to thehull. The clutch and propulsion systemare only asked to pick up a stoppedpropeller shaft rather than a windmillingpropeller. Because load on the engagingclutch is greatly reduced, clutch life isextended. Transmission gears, engine andother major components of the propulsionsystem are subject to less shock.

3. The propeller shaft brake will preventengine stall when attempting crash stopsor when high vessel speed shaft reversalsare attempted during maneuvers.

A propeller shaft brake should be consideredon any marine propulsion system usingengines over 500 hp where the reduction ratiois 4:1 or deeper and where high speedmaneuvering is a requirement.

Disc brakes and drum-type brakes areavailable. The brake should be sized to handleat least 75% of the full rated shaft torque andshould stop the shaft within three secondsduring a crash reversal. Brake sizerequirements will vary with type of propeller,vessel speed, and vessel application.

Proper control and sequencing of a propellershaft brake is very important. Overlap canoccur if the clutch engages before the brakeis released. This would show as an extra loadon the engine, slowing it and even stalling theengine. Underlap is releasing the brake wellahead of the clutch making contact. Thepropeller will quickly begin to windmill in thewrong direction and much of the advantage ofthe brake is lost.

6

Event Sequence TimingSequencing and timing of engine governor,marine transmission clutch, and shaft brakeaction are critical and only systems of thefollowing characteristics should be used:

Pilot House Control MovementFull Ahead to Astern and Full Astern to FullAhead

Event Sequence

1. Governor to Low Idle2. Clutch to Neutral3. Shaft Brake Applied Propeller Shaft

Stops4. Shaft Brake Released

5a. Throttle Boost Applied5b. Clutch Engaged*

6. Throttle Boost Off, Governor to FullOpen

With the above sequencing and timing, theshaft brake will engage any time the pilothouse control lever is in the neutral position.Throttle boost will activate each time the pilothouse control lever is shifted from neutral to aclutch-engaged position.

A proportional pause-type control system willallow for a variable time between Steps 3 and4 in the event sequence when the shaft brakeis applied. The pause is in proportion to thelast-called-for speed. A crash reversal from fullspeed will leave the brake applied for a longerperiod than when slow speed maneuvering.This full speed reversal pause in neutral ismade just long enough for the vessel speed toslow to a point that the propeller slip streamtorque will not stall the engine when thereverse clutch is engaged.

* Timing sequence from brake release to clutchengagement should result in from one quarter to onerevolution of the propeller shaft in the wrong directionto ensure there is no overlap between brake releaseand clutch engagement.

Properly adjusted air controls should provideevent sequence time in the area of 5 to 7seconds for slow speed maneuvering and inthe area of 7 to 12 seconds or more for fullspeed crash reversals. The timing is set asfast as the propulsion system can safely beoperated. The timing should be setpermanently at the time of sea trials.

Without a propeller shaft brake, a longerpause in neutral in place of Steps 3 and 4 inthe event sequence will normally be requiredto allow reduced vessel speed.

The control system must be carefullymaintained. Follow the manufacturer’smaintenance recommendations explicitly.

Recommended SystemsConsult with the manufacturers of controlsystems to determine their availability toprovide event sequence systems as describedpreviously.

The shipyard should furnish a low airpressure alarm located at the supply air to thepneumatic control system. The alarm shouldbe audible and visual and should be actuatedif the air pressure should fall below apredetermined level–generally 90 psi(620.5 kPa).

MathersThe Mathers control system offers singlelever pneumatic control of speed, clutch, andbrake (if required). The system uses fixedorifice timing with option for as many controlstations as required. They also offer electroniccontrols with the same sequence timingadjustments.

7

8

CH5 Control Head

Port Numbers:1 Supply6 Speed7 Direction8 Direction

Station TransferPanel

6 17 8

6 17 8

Forward

3 2 45

8 1 7

6

AD12 Air Drive

Port Numbers:1 Supply2 Ahead3 Astern4 Boost5 Speed-Out6 Speed-In7 Astern8 Ahead

MathersControl

GovernorPositioner Clutch

Actuator

AirSupply

Air Treatment Panel

Test GaugePanel

Resevoir

Booster

DiscBrake

Secondary Station

Control AirGauge

TransferButton

Mathers Controls Inc.AD12 Propulsion Control System

ForHydraulic Clutches

Figure 1.6

WABCOWABCO, a division of American Standard,also provide complete sequencing controlsystems. The following is an example.

LMAC-3C Logicmaster Air Clutch-ControlSystems for 3600 Family of CaterpillarEngines

This control system provides interlocked andsequenced operation of proportional timing inahead and astern clutch engagement andengine speed control to ensure properoperation of the propulsion machinery as theoperator manipulates the remotely mountedcontrol lever. The control system incorporatesthe following interlocks and the optionalfeatures.

1. Positive cross engagement interlocksensure that one clutch is vented below 15 psi before the opposite clutch can beinflated.

2. The clutch engagement systemincorporates a three-stage clutch fill. First,an initial quick fill to bring the clutchshoes into contact with the drum. Second,a controlled rate of fill. Third, a full flowhard fill inflation at maximum rate up tosupply pressure.

3. A governor power boost is applied duringinitial clutch engagement to preventengine stalling. This boost is adjustable inmagnitude and duration. Adjustment of

timer unit controls rate of boostapplication and regulator controls themagnitude of boost delivered to thegovernor.

4. A clutch pressure-engine speed interlockto ensure that the clutch is inflated tolock-up pressure before engine speed canbe increased from the remote operatingstation.

5. Proportional reversing interlock occurs inboth directions. This time is adjustableand provides a neutral hold timeproportion to the vessel speed. Normalmaneuvers are accomplished with theminimum reversing time increasing inproportion.

6. The ahead clutch hold-in function toshorten the reversing time by holding inthe ahead clutch which uses the engine’scompression to slow down the propellerduring high speed and crash reversals.

7. A shaft brake signal (optional) is providedto actuate a shaft brake in synchronizationwith the clutch engage/disengage controlsystem. The brake is released whenclutch engagement is initiated and isapplied when both clutches are fullyreleased. When a brake is used, the“interlocks” provide a neutral hold topermit the brake to be applied and theshaft stopped before reversal is initiated.

2 4 6 8 1000

1009080706050

40302010

Figure 1.8

Th

rott

le P

ress

ure

(psi

)

Time (seconds)

throttleboost

high command

low command

Pneumatic Throttle Air Pressure Vs Time

Figure 1.7

Time (seconds)2 4 6 8 100

0

1009080706050

40302010

Clu

tch

Pre

ssu

re(p

si)

Clutch Fill Modulation

HardfillPressure

SupplyPressure

FillModulation

9

Other manufacturers may also be able toprovide suitable systems.

Controllable Pitch Propeller toAvoid Engine Stall and ReversalThe controllable pitch propeller allowssmooth, well-controlled vessel reversals whilethe engine rpm and horsepower are kept atoptimum levels. This is most desirable onvessels equipped with deep ratio marinetransmissions that must be reversed whilemoving at full vessel speed. To reverse avessel equipped with a controllable pitchpropeller, reduce propeller pitch to the“neutral pitch” position, then increase pitch inthe “astern” or reverse direction slowlyenough to allow the engine to maintain its fullload rpm and horsepower.

Determining Likelihood ofStalling During Sea TrialInitial sea trials should determine thelikelihood of the control system/enginecombination stalling during a crash reversalmaneuver. Adjustment and timing of aircontrols can be determined and properly setduring sea trials. Suggested procedure is tostart with a low forward vessel speed andmake crash shifts into reverse at smallincrements of increased forward vessel speeduntil it is determined that the system willallow a crash reversal at the most severecondition the vessel will encounter.

10

Instrumentation and Monitoring SystemsInstrumentsAlarm/Shutdown ContractorsInstrumentation Problems

Instrumentation is a valuable component of awell designed installation.

InstrumentsThe functions below are listed in their orderof desirability for Helmsmans stationinstrument panel placement.

A = Must Have InstrumentationB = Highly Desirable InstrumentationC = Useful InstrumentationD = Questionable, Without Special

Requirements

A Engine Lubrication Oil PressureLoss of lube oil pressure while operatingat full power is likely to result in severeengine damage. Quick action by the pilotin reducing stopping the engine can savean engine. To protect the engine, the pilotmust be able to see the status of engineoil pressure continuously.

A Jacket Water TemperatureIncrease of jacket water temperature isalmost as serious as loss of lube oilpressure and somewhat more likely.Similar quick action by the pilot canminimize engine damage resulting from ahigh temperature condition.

A Engine Speed (rpm)Rather than a safety-oriented enginefunction, engine speed is an operationrelated measurement. Observing therelationship between engine speed, vesselload, and throttle position will allow thepilot to make informed judgments aboutengine load and need for maintenance.

B Transmission Oil PressureTransmission oil pressure measurementshows the pilot when the transmissionclutches have engaged and usefulinformation concerning the condition ofthe pump, filters, or clutches. Excessivepressure can damage components in thehydraulic circuit.

B VoltmeterVoltage of the starter/alternator circuitgive the pilot useful information regardingbattery condition, alternator condition,

state of charge of the batteries, andcondition of the battery cables.

C Transmission Oil TemperatureMany transmission problems, such asclutch slippage, insufficient clutchpressure, bearing wear, cooler blockageor loss of cooling water flow will bemanifested as an increase in transmissionoil temperature.

C Exhaust Stack TemperatureChanges from normal exhaust stacktemperatures will give useful informationconcerning air filter restriction, aftercoolerrestriction, injector condition, valveproblems, and engine load.

D Individual Cylinder ExhaustTemperatureWhile these instruments will giveimmediate warning of individual injectorfailure, the inevitable wide tolerance onthe standard temperature (±42 C degrees)(75 F degrees) often causes undueoperator concern. In general, advantagesgained by this instrumentation areovershadowed by high cost(thermocouples need annual replacement)and need for special operator training.

Alarm/ShutdownContactorsThese are preset contactors (switches) thatwill activate a customer-supplied alarm, light,or engine shutdown solenoid, when certainlimits are exceeded.

Alarm switches available from Caterpillar willoperate on AC or DC, from 6 volts to240 volts. These switches are of the singlepoledouble-throw type.

With the exception of the overspeed function,propulsion engines should not beautomatically shutdown. The pilot should bewarned of impending failure but should retainthe authority to decide whether to shut downthe engine or to continue to operate.Overspeed failures will result in loss of enginepower. If the engine is equipped with anoverspeed protection device, the engine will

15

not be harmed as much as if the overspeedfailure had proceeded unimpeded.

A = Must Have InstrumentationB = Highly Desirable InstrumentationC = Useful InstrumentationD = Questionable, Without Special

Requirements

A Low Lube Oil PressureThere are two conditions that need to bealarmed: low lube oil pressure at lowengine load (idle conditions) and low lubeoil pressure at high engine speed and/orload. An oil pressure that would beperfectly safe while operating at very lowloads and/or speeds would be too low atfull load/speed conditions. A suitablesystem will include two pressure-sensitivecontactors and a speed (rpm) switch todecide which pressure switch should havethe authority to warn the operator.

A High Coolant TemperatureHigh coolant temperature contactorsshould be set to actuate within 2.8°C (5°F) of the highest normal temperatureof the engine at the point of installation.

A. OverspeedOverspeed faults occur when some part ofthe engine fails, causing the fuel controlmechanism to be locked in a high fuelflow condition. When the engine load goesto a low level, the engine will continue toreceive a high fuel flow. Without the load,the engine speed increases to adangerously high level. Generally, theengine’s air supply must be cut off to savethe engine.

Overspeed contactors need to be set12-15% over rated engine speed to avoidnuisance engine shutdowns duringsudden reductions in engine load.

B Water Level AlarmWarning of coolant loss could allow theoperator to save an engine which wouldotherwise be lost to overheat failure.

Install level sensors in the highest part ofthe cooling system–generally in theauxiliary expansion tank. This will give

warning of coolant loss at the earliestpossible time, before the coolant level hasfallen to a dangerous level.

C Low Sea Water Pump DifferentialPressureThe sea water flow to a heat exchangercooled engine is very important. It is agood idea to install a differential pressurecontactor across the sea water pump towarn of any discontinuity in sea waterflow.

C Intake Manifold Temperature AlarmSwitchesIntake manifold temperature alarmswitches are available for use on someengines. High intake manifoldtemperature will warn of sea water pumpfailure, sea strainer plugging, or any othercondition which reduces or stopsaftercooler water flow.

Alarm PanelCaterpillar recommends the following featuresin alarm panels:

• Fault light lock-in circuitry keeps the faultlight on when intermittent faults occur.

• Lockout of additional alarm lights preventssubsequent alarm lights from going onafter the activated engine shutoff stops theengine. This aids in troubleshooting.

• Alarm silence allows the operator toacknowledge the alarm without having tocontinually listen to the alarm horn. Thealarm light is left on.

• If more than one engine is connected to analarm panel, a fault in a second engineshould activate the alarm even though thealarm horn may have been silenced after afault on another engine.

• Circuit test provides for periodic checkingof alarm panel functions.

16

InstrumentationProblemsWithout highly trained personnel andrigorous discipline, too much instrumentationcan be detrimental.

The weak link in any instrumentation systemis the sensor unit (transducer). Too often, anotherwise fine system is sabotaged because offrequent false alarms. Plan annualreplacement of the sensor units unlessunusually high quality sensors are used.

High water temperature sensors will not warnof overheat conditions unless their sensingbulbs are submerged in water. High watertemperature sensors will not warn of coolantloss.

Electronically controlled enginesThe engines have sensors needed to controlthe engines standard and there are panelsavailable which monitor and display thevalues these sensors put out. Consult pricelist for optional pilot house panels for use withthese engines.

17

Starting SystemsGeneral InformationStarting AidsStarting Smoke

General InformationStartability of a diesel engine is affectedprimarily by ambient temperature, enginejacket water temperature, and lubricating oilviscosity. Any parasitic loads (usuallyassociated with the driven equipment) cangreatly influence the startability, as well.

The diesel engine relies on heat ofcompression to ignite fuel. When the engineis cold, longer cranking periods or highercranking speeds are necessary to developadequate ignition temperatures. The drag dueto the cold lube oil imposes a great load onthe cranking motor. Oil type and temperaturedrastically alter viscosity. SAE 30 oilapproaches the consistency of grease below 0°C (32°F).

Starter TypesThere are three different types of startingsystems normally used for Caterpillar dieselengines. They differ in the method of storingand recharging the energy required forrestarting the engine.

Electric Starting SystemsUse chemical energy stored in batteries,automatically recharged by an engine-drivenalternator or by an external source.

Air or Pneumatic Starting SystemsUse compressed air in pressure tanks,automatically recharged by an electricmotor-driven air compressor.

Hydraulic Starting SystemsUse hydraulic oil stored in steel pressurevessels under high pressure automaticallyrecharged by a small engine-driven hydraulicpump with integral pressure relief valve.

The technology of the systems are welldeveloped. Any of the systems are easilycontrolled and applied either manually orautomatically. Several of the factors whichinfluence the choice of systems have beentabulated below.

ElectricBattery-powered, electric motors utilize lowvoltage direct current and provide fast,convenient, pushbutton starting withlightweight, compact engine-mountedcomponents. A motor contactor relievescontrol logic circuits of high crankingcurrents.

Storage MethodLead/Acid storage batteries.

Relative CostLowest.

Maintenance RequirementsHighest, the batteries require considerablemaintenance.

Reliability of StartingGood.

Special ConcernsHydrogen gas, released from the batteriesduring charging, is very explosive, andcompartments containing lead acidbatteries must be properly vented.

FLYWHEEL

STARTINGMOTOR

BATTERIES

MAGNETICSWITCH

Figure 3.2

BATTERYCHARGER

STARTER MOTOR

BATTERIES

TO POWERINPUT

Figure 3.1

21

BatteriesBatteries provide power for engine cranking.Lead-acid types are readily available, havehigh output capabilities, and are relativelyinexpensive. Nickel-cadmium batteries arecostly, but have long shelf life and requireminimum maintenance. Nickel-cadmium typesare designed for long life and may incorporatethick plates which decrease high dischargecapability. Consult the battery supplier forspecific recommendations.

Ambient temperatures drastically affectbattery performance and chargingefficiencies. When operating in cold climates,the use of battery heaters are recommended.The heaters should be set to maintain batterytemperature in the range of 32° to 52°C (90°to 125°F) for maximum effectiveness. Thesignificance of colder battery temperatures isdescribed below.

All battery connections must be kept tight andcoated with grease to prevent corrosion.

Battery Location and HydrogenVentingInstall batteries only in well ventilatedcompartments. Visual inspection for terminalcorrosion and damage should be easy.Batteries emit hydrogen gas during therecharging cycle. Hydrogen gas is highlyexplosive and very dangerous in even smallconcentrations. Hydrogen gas is lighter thanair and will escape harmlessly to atmosphere,if not trapped by rising into a chamber fromwhich there is no upward path to atmosphere.Devices which can discharge electrical sparksor cause open flames must not be allowed inthe same compartment or in the vent path forthe escaping hydrogen gas.

Battery Disconnect Switches (Battery Isolating Devices)Solid state electrical devices will suffer wheninstalled in vessels whose electrical systemincludes battery disconnect switches whichcan interrupt loadbearing circuits. At theinstant of a circuit disconnect, transientcurrents and voltages will often cause failurein any component whose transistors are nototherwise protected.

Use Battery Disconnect Switches (BatteryIsolating Devices) which do not cause voltagetransients (spikes).

Battery ChargersVarious chargers are available to replenish abattery. Trickle chargers are designed forcontinuous service on unloaded batteries andautomatically shut down to milliamperecurrent when batteries are fully charged.Overcharging shortens battery life and isrecognized by excessive water losses.

Conventional lead-acid batteries require lessthan 59.2 mL (2 oz) of make-up water during30 hours of operation.

Float-equalize chargers are more expensivethan trickle chargers and are used inapplications demanding maximum battery life.These chargers include line and loadregulation, and current limiting devices whichpermit continuous loads at rated output.

Chargers must be capable of limiting peakcurrents during cranking cycles or have arelay to disconnect during cranking cycles.Where engine-driven alternators and batterychargers are both used, the disconnect relayis usually controlled to disconnect the batterycharger during engine cranking and running.

Engine-driven generators or alternators canbe used but have the disadvantage ofcharging batteries only while the engine runs.Where generator sets are subject to long idleperiods or many short stop-start cycles,insufficient battery capacity could threatendependability.

Temperature vs Battery Output

°C

Percent of27°C (80°F)

Ampere HoursOutput Rating

°F

270

-18

1006540

80320

22

Continuous Cranking Time Limit withElectric Starter MotorsAn engine should not be crankedcontinuously for more than 30 seconds toavoid overheating of the starter motors.

Starter Motor Cooling Period BetweenCranking PeriodsAllow the starter motor to cool for twominutes before resuming cranking.

Battery Cable Sizing (Maximum Allowable Resistance)The start circuit between battery and startingmotor, and control circuit between battery,switch, and motor solenoid must be withinmaximum resistance limits shown.

Not all this resistance is allowed for cables.Connections and contactors, except the motorsolenoid contactor, are included in the totalallowable resistance. Additional fixedresistance allowances are:

ContactorsRelays, Solenoid, Switches0.0002 Ohm each

Connections(series connector)0.00001 Ohm each

The fixed resistance of connections andcontactors is determined by the cable routing.Fixed resistance (Rf) subtracted from totalresistance (Rt) equals allowable cableresistance (Rc): Rt - Rf = Rc.

With cable length and fixed resistancedetermined, select cable size using thefollowing chart. Only full-stranded copper wireshould be used. Arc welding cable is muchmore flexible and easier to install than fullstranded copper wire cable, but welding cableis not so durable and will be damaged fromcorrosion in a much shorter time.

RESISTANCEIN

OHMSAT

800F(270C)

INCHES

METERS

#4 #000#2 #0 #00#1

2-#0000 INPARALLEL

2-#00

0 IN P

ARALLEL

2-#0

0 IN

PARALL

EL

OR

2-#0

IN P

ARAL

LEL

0

0 2.54 5.08 7.62 10.16 12.70 15.24

100 200 300 400 500 600

.00300

.00280

.00260

.00240

.00220

.00200

.00180

.00160

.00140

.00120

.00100

.00080

.00060

.00040

.00020

.00000

Figure 3.4

Example:

56 in.6"

6"

76 in.

THIS CIRCUIT USES FOUR12-VOLT BATTERIES IN A24-VOLT SYSTEM.

SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24-voltSTARTING MOTOR TYPE . . . . . . . . . . . . . . . . . . . . . HEAVY DUTYMAXIMUM ALLOWABLE RESISTANCE . . . . . . . . . . .00200MINUS FIXED RESISTANCE— 6 CONNECTIONS @ .00001 . . . . . . . . . . . . . . . . . .00006 OHMRESISTANCE REMAINING FOR CABLE . . . . . . . . . .00194 BATTERY CABLE LENGTH . . . . . . . . . . . . . . . . . . . 144 in.

Figure 3.3SolenoidSwitchCircuit

StartingMotorCircuit

Magnetic Switch andSeries-Parallel

Circuit

.0067 Ohm

.030 Ohm

.070 Ohm

.0012 Ohm

.002 Ohm

.002 Ohm

12 Volt System.048 Ohm



23

To meet cable length and resistancerequirements, cable size must be No. 1. Todetermine fixed resistance in a parallel circuit,only series connections in one leg of theparallel circuit are counted.

Connections/Proper PracticesElectrical connections are often a source ofproblems for shipboard electrical systems.

Salt air and water are highly corrosive.Electrical connections are almost alwaysmade of dissimilar metals. Corrosion is moredestructive between dissimilar metals.

The following table lists good practices formarine electrical systems.

When making electrical connections betweenwires, connect wires mechanically so tuggingor pulling can be withstood without any othertreatment of the joint. Then, coat the joint andthe nearest portions of each wire withelectrical solder. Do not expect solder toincrease joint strength. The solder is forcorrosion protection.

Do not use crimp-type connectors for marineservice—The plastic sleeve tends to hide thecorrosion from view rather than protectingthe joint.

Pneumatic

Air starting, either manual or automatic, ishighly reliable. Torque available from air

motors accelerate the engine to twice thecranking speed in about half the timerequired by electric starters.

Air is usually compressed to 758 to 1723 kPa(110 to 250 psi) and is stored in storage tanks.Stored air is regulated to 759 kPa (110 psi)and piped to the air motor. A check valvebetween the compressor and the air receiveris good practice, to protect against a failure ofplant air which might deplete the air receiverssupply. The air compressors are driven byexternal power sources.

Air starter air supply piping should be shortand direct and at least equal in size to themotor intake opening. Black iron pipe ispreferred. The piping requires flexibleconnections at the starter. Deposits of oil andwater will accumulate in the air receiver andat low spots in the piping. The accumulationof oil and water must be removed daily toprevent damage to the starting motors.Manual or automatic traps should be installedat the lowest parts of the piping and all pipingshould slope toward these traps.

Air tanks are required to meet specificcharacteristics, such as the specifications ofthe American Society of MechanicalEngineers (ASME). Compressed air storagetanks must be equipped with a maximumpressure valve and a pressure gauge. Checkthe maximum pressure valve and pressuregauge often to confirm proper operation.

Figure 3.5

24

Air Storage Tank Sizing(except 3600 Engines)Many applications require sizing air storagetanks to provide a specified number of startswithout recharging. This is accomplished asfollows:

Where:Vt = Air Storage Tank Capacity (cubic

feet or cubic meters)Vs = Air consumption of the starter

motor (m3/sec or ft3/sec)–See AirStarting Requirements Chart.

T = Total Cranking Time Required(seconds) if six (6) consecutivestarts are required, use seven (7)seconds for first start (whileengine is cold), and two (2)seconds each for remaining five(5) starts, or a total cranking timeof seventeen (17) seconds.

Pa = Atmospheric Pressure (psia orkPaa) normally, atmosphericpressure is 14.7 psia or 101 kPaa.

Pt = Air Storage Tank Pressure (psia orkPaa). This is the storage tankpressure at the start of cranking.

Pmin = Minimum Air Storage TankPressure Required to SustainCranking at 100 rpm (psia orkPaa)–See Air StartingRequirements Chart.

Cranking Time RequiredThe cranking time depends on the enginemodel, engine condition, ambient airtemperature, oil viscosity, fuel type, anddesign cranking speed. Five to seven secondsis typical for an engine at 26.7°C (80°F).Restarting hot engines usually take less thantwo seconds.

Air Consumption of the Starter MotorThe starter motor air consumption dependson these same variables and also on pressureregulator setting. Normal pressure regulatorsetting is 690 kPa (100 psi). Higher pressurecan be used to improve starting under

Vt = Vs 3 T 3 Pa

Pt – Pmin

25

Air Starting Requirements

Air Consumption of the Air Start MotorVersus

m3/sec (ft3/sec) of Free AirAir Storage Tank Pressure

-Pt-

EngineModel

3304

793 kPaa (115 psia) 965 kPaa (140 psia) 1137 kPaa (165 psia) -Pmin-

690 kPag (100 psig) 862 kPag (125 psig) 1034 kPag (150 psig) kPaa (psia)

MinimumTank Pressure

.16 (5.8) .20 (6.8) .21 (7.7) 345 (50)3306 .17 (5.9) .20 (6.8) .22 (7.8) 352 (51)

3406 .17 (6.2) .21 (7.3) .23 (8.3) 379 (55)3176/96 .17 (6.2) .21 (7.3) .23 (8.3) 379 (55)

3408 .18 (6.4) .21 (7.3) .24 (8.6) 372 (54)3412 .25 (9.0) .29 (10.3) .33 (11.8) 310 (45)3508 .26 (9.3) .30 (10.8) .36 (12.6) 310 (45)3512 .28 (9.8) .32 (11.4) .38 (13.3) 345 (50)3516 .30 (10.5) .34 (12.1) .40 (14.1) 448 (65)

Note: For engines equipped with pneumatic prelube: add .03 m3/sec (1 ft3/sec) air consumption.

adverse conditions up to a maximum of 1034 kPa (150 psi) to the starting motor. Thevalues shown on the air requirements chartassume a bare engine (no parasitic load) at10°C (50°F).

OperationThe supply of compressed air to the startingmotor must be shut off as soon as the enginestarts to prevent wasting starting air pressureand prevent damage to starter motor byoverspeeding.

Air Storage Tank Sizing(3600 Engines)The 3600 Air Start Sizing Curve showsrequired tank volume (for inline or veeengines) versus desired number of starts fordifferent initial tank pressures. The curves for1600 kPa (230 psi) and less allow for 6%pressure drop between tank and starter. Forpressures greater than 1600 kPa (230 psi), thecurves assume regulation to 860 kPa (125 psi)pressure at the starter. The pressureregulator should have capacity to flow 280 liters/second (600 scfm) per starter atregulator inlet pressures above 415 kPa (60 psi).

Air starters for 3600 Engines are designed tooperate at a maximum air pressure of 1550 kPa (225 psi) at the starter. Minimum airpressure to provide adequate cranking speedfor engine starting at 25°C (77°F) ambienttemperature is 415 kPa (60 psi) at the starter.

The air pressure to the starter must beregulated when tank pressures greater than1550 kPa (225 psi) are used.

These curves do not include air for a prelubepump.

The Caterpillar air prelube pump consumptionrate is 28.2 L/s (60 scfm).

If the engine will be started at ambienttemperatures lower than 25°C (77°F),additional storage tank volume will berequired.

Prevention of Frost at the StarterMotor Air DischargeWater vapor in the compressed air supplymay freeze as the air is expanded below 32°F(0°C). A dryer at the compressor outlet or asmall quantity of alcohol in the starter tank issuggested.

HydraulicHydraulic starting provides high crankingspeeds and fast starts. It is relatively compact.Recharging time, using the smallengine-driven recharging pump, is fast. Thesystem can be recharged by a hand pumpprovided for this purpose, although handrecharging is very laborious. The highpressure of the system requires special pipesand fittings and extremely tight connections.Oil lost through leakage can easily bereplaced, but because of high pressures in theaccumulators (usually 20,700 kPa [3000 psi]when fully charged) recharging theaccumulator/s requires special equipment.

Repair to the system usually requires specialtools.

Hydraulic starting is most often used wherethe use of electrical connections could pose asafety hazard.

Hydraulic starting systems are not availablefrom Caterpillar. Contact your local Caterpillardealer for the nearest available supplier.

The Hydraulic Accumulators, if used, containlarge amounts of stored mechanical energy.They must be very carefully protected fromperforation or breakage.

3600 Air Start Tank Sizing

Number of Available Starts

InL

ine

En

gin

e A

ir S

tora

ge

Tan

k V

olu

me

(m3 )

Vee

En

gin

e A

ir S

tora

ge

Tan

k V

olu

me

(m3 )Initial Tank

Pressures (kPa)

1.4

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.0

2.8

2.6

2.4

2.2

2.0

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0.0

0 1 2 3 4 4 6 7 8 9 10

4000 kPa3000 kPa

2000 kPa

1600 kPa14

00 kP

a

1000

kPa

700

kPa

Time/Start = 3 secRegulator Pressure = 860 kPaFinal Tank Pressure = 415 kPa

Figure 3.6

26

Starting AidsThe diesel engine depends on the heat ofcompression of the air in a cylinder to ignitethe fuel. Below some specified temperature,the cranking system will not crank the enginefast enough or long enough to ignite the fuel.One or more commonly used starting aids,such as jacket water heaters and/or ethermay be required.

Jacket Water HeatersJacket water heaters are electrical heaterswhich maintain the jacket water at atemperature high enough to allow easystarting of the engine. More heaters of higherratings may be required in areas of extremelycold temperature.

EtherEther is a volatile and highly combustibleagent. Small quantities of ether fumes addedto the engines intake air during crankingreduce the compression temperature requiredfor engine starting. Caution is required whenusing ether to prevent spread of fumes toatmosphere. A proper ether system will meterthe rate of ether consumption. Not more than1 cm3 (0.033 oz) of ether should be releasedper 100 rated hp for each 10 seconds ofcranking. Very low ambient temperatures mayrequire increasing the ether consumptionrate. Under no circumstances should ether bereleased into an engine while running.

The 3126 Marine Engine is equipped with anair inlet heater. Under no circumstancesshould ether be used on this engine.

Manifold HeatersHeat added to the intake manifold of anengine during cranking will significantlyimprove startability and reduce any whitestart-up smoke. Manifold heaters are notavailable from Caterpillar.

Starting SmokeHigh performance engines are prone to havesome white start-up smoke. The white smokeis composed of unburned fuel*. CaterpillarEngines have been designed to minimize thisproblem.

Operators can do several things to improvethe situation:

• Use of jacket water heaters to raise theengine water temperature to 32-49°C (90 to 120°F) prior to starting.

• Keep warm-up idle speeds (rpm) low.• Warm the air to the air cleaners and intake

manifold.• Increase the exhaust pipe restriction-flow

(exhaust back pressure) during thewarm-up period.

*Diesel engines which are designed to have high outputpower, yet still be relatively light weight, generallyhave low compression ratios; i.e., in the range of 12.5to 16:1. This design factor makes them prone tomisfire and run rough until the engine reaches normaloperating jacket water temperatures: 80 to 93°C (175 to 200°F).

27

Start-up SystemsGeneral InformationTesting/Instruments and Accessories

General InformationStart-up is the final examination at the end ofthe engine installation process.

The start-up is:

• To confirm the engine is operatingproperly.

• To confirm the boat’s systems associatedwith the engine (exhaust, cooling,ventilation, fuel, starting, etc.) are adequateto allow the engine to operate up to its fullpotential.

• To determine the causes of performancedeficiencies in the engine or boat.

Testing/lnstruments andAccessoriesThe following tools are recommended formeasurement of the data for start-up andassociated performance testing.

TachometerUsed to measure the speed (rpm) of theengine.

Caterpillar Part Number—6V3121 MultitachGroup, See Special Instruction, SEHS7807

Pressure Measuring DeviceUsed to measure the pressure of the fluids(air, oil, water, and fuel) in many enginesystems. There are both high and low limitson the pressure of all the fluids.

Caterpillar Part Number—6V9450 PressureGroup, six vacuum/pressure gauges permit acheck of air cleaner restriction, oil pressure,manifold pressure, and fuel pressure.Provides readings in psi and kPa. Pressurerange—100 kPa to 1000 kPa (15 psi to 150 psi), See Special Instruction SEHS8524.

Temperature Measuring DeviceUsed to measure the temperature of the fluids(air, oil, water, and fuel) in many enginesystems.

Caterpillar Part Number–9S9102/8T0470Thermistor Groups, Temperature Range—

30°C to 1370°C (–20°F to 2500°F), SeeSpecial Instruction SMHS7140 and SEHS8446.

Fuel Density Measuring DeviceUsed to measure the relative amount ofenergy in the fuel. The heavier a quantity offuel is, the more energy it contains and themore power it will generate in an engine.

Caterpillar Part Number—lP7408Thermohydrometer and 1P7438 Beaker areused to measure the API gravity andtemperature of diesel fuel, so correctedhorsepower can be calculated.

PyrometerUsed to measure the engine’s exhausttemperature.

Caterpillar Part Number–lP3060 PyrometerGroup, Temperature Range = 18°C to 870°C(0°F to 1600°F), See Special InstructionSEHS7807.

PitchometerUsed to measure the propeller’s pitch;confirming their accuracy.

Caterpillar Part Number—8T5322Pitchometer accurately measures propellerblade pitch either on or off the propeller shaft.Pitch can be measured at any shaft angle andat any point along the length of the blade,even under water. See Special InstructionSEHS8643.

Probe Seal AdaptersUsed to allow measurement of the variouspressures and temperatures of the engine’ssystems without need to shut down and drainthe fluids therein. Works like the valve in asoccer ball. The adapters can be permanentlyinstalled and are equipped with a hex headplug to eliminate leakage and debrisaccumulation.

Caterpillar Part No. 5P2720 1/8 in.-27 NPTThread

5P2725 1/4 in.-18 NPTThread

See Special Instruction SMHS7140.

31

Water ManometerMeasures the exhaust backpressure andintake duct or air cleaner restriction to flow.

Caterpillar Part Number—8T0452 WaterManometer Can be locally made from 1550 mm (5 ft) length of flexible clear plastic3/8 in I.D. tubing. See Special InstructionSEHS8524.

Fuel Flow Measuring DeviceUsed in conjunction with the tachometer(engine speed), pressure measuring device(intake manifold pressure), and pyrometer(exhaust temperature) to determine thepower demanded of the engine.

Caterpillar Part No. lU5430 Fuel MonitorArrangement for use with 3100, 3208, 3300,and 3400 Engine Families. Fuel flow range11.4 L/h to 264 L/h (3 U.S. gal/h to 70 U.S.gal/h). lU5440 Fuel Monitor Arrangement foruse with 3500, 3606, and 3608 Engines fuelflow range 151.4 L/h to 3785 L/h(40 U.S. gal/h to 1,000 U.S. gal/h).

Boat Speed Measuring DeviceHand-held radar (like that used by traffic lawenforcement officers to check vehicle speed)is effective for this purpose.

32

ServiceabilityOverhead Clearance for Connecting Rod and PistonRemoval

General InformationWell-designed engine compartments willinclude features which contribute to theserviceability of the machinery. For example,overhead lifting equipment, some enginesubassemblies may be heavier than one mancan safely lift by hand, particularly in the oftenclose quarters of the machinery space.

Hatches located directly above engines, forsimplified removal and reinstallation duringoverhaul.

Outlets of electricity and compressed air todrive high production mechanic’s tools.

Access to those points on the engine whichrequire periodic preventive maintenance suchas:

• lube oil filters and drain plug—engine andtransmission

• fuel and air filters• sea water and jacket water pump• turbochargers• zinc plugs• heat exchanger—for core cleaning

Overhead Clearance forConnecting Rods andPiston RemovalThe following table gives the height above thecrankshaft centerline requirements to allowremoval of a connecting rod and piston fromthe engines. This information is offered toassist designers who wish to provide adequateoverhead clearance for piston/connecting rodremoval.

Vee Engines

Height AboveCrankshaft CenterEngine

693 mm (27.28 in.)913 mm (35.94 in.)

1234 mm (48.58 in.)969 mm (38.15 in.)

1891 mm (74.49 in.)*

3408B&C, 3412C&ED346, D348, D349D379, D398, D3993508, 3512, 35163612, 3616

* Distance to remove cylinder liner

In-Line Engines

Height AboveCrankshaft CenterEngine

626 mm (24.6 in.)711 mm (28 in.)635 mm (25 in.)

786 mm (30.9 in.)1127 mm (44.37 in.)2087 mm (82.16 in.)*

3116, 3126, 3126B3304B, 3306B3176, 31963406B, C&ED3533606, 3608

* Distance to remove cylinder liner

35

Marine EnginesApplication andInstallation Guide

● Cooling Systems


Cooling SystemsGeneral InformationEngine Cooling CircuitsSystem CoolersExpansion TanksCooling System Protective DevicesEmergency SystemsCentral Cooling SystemsSystem Pressure DropCorrosionUseful Tables to Designers of Cooling Systems

General InformationA properly controlled cooling system isessential to satisfactory engine life andperformance. Defective cooling systems andcareless maintenance are the direct cause ofmost engine failures. The factory-suppliedcooling system should not be modified sincethe various circuits of the engine-mountedcooling system have been sized to provide theproper flows to its components. Changes tothese circuits can cause flow balance to bedisrupted to the point that various enginecomponents may fail.

Need for CleanlinessAll pipe and water passages external to theengine must be cleaned before initial engineoperation to ensure there will be flow and thatforeign materials will not be lodged in theengine or cooler.

Flexible ConnectorsCustomer supplied coolant piping must beattached to the engine with flexibleconnectors. The positions of flexibleconnections and shut-off valves are importantconsiderations. The shut-off valve should belocated so that a broken flexible connectioncan be isolated without having to shut downthe whole system.

Engine Cooling CircuitsCaterpillar marine engines generally use oneor two cooling water circuits. A closed treatedwater cooling circuit is always used forcooling the engine jacket. A second circuit isused on turbocharged aftercooled enginearrangements when colder than jacket wateraftercooling is required. Cooling of the marinetransmission oil is accomplished using eitherengine jacket water, aftercooler water, or aseparate water cooling circuit depending onthe model of marine transmission and/or theengine cooling arrangement.

Jacket Water SystemDefinitionCaterpillar Marine Engines are designed tooperate with a jacket water temperaturedifferential of approximately 8°C (15°F)measured across the engine under full load.Minimum jacket water temperatures arecontrolled by water temperature regulators(thermostats) to provide efficient engineoperation. Maximum jacket watertemperature limits are controlled by the sizeof the coolers and flow of coolant. The closedjacket water system consists of engine waterjacket (engine block and cylinder heads), thecirculating pump, water temperatureregulator, oil cooler, engine-mountedexpansion tank and heat exchanger.

1

Water Temperature RegulatorsThe water temperature regulator (thermostat)and cooler bypass are used to regulateoperating temperature. The regulator directsall or part of the water discharged from theengine jacket to the cooler. The remainder isbypassed to the expansion tank on heatexchanger/keel cooled engines or to thewater pump inlet on radiator cooled engineswhere it mixes with cooled water beforereturning to the engine jacket.

Depending on the engine and configuration,the thermostats may be in a controlled inlet orcontrolled outlet configuration. The operatingtemperature of the jacket water will be aboutthe same for either system if the thermostatsettings are the same or similar. In either theoutlet or inlet control system, thermostatplacement and sensing of jacket watertemperature (and therefore bypass control) isalways at the jacket water outlet.

2

ExpansionTank

Return

C B

AEngineThermostat

Outlet

B-A: Cold Bypass FlowC-A: Full External Flow

Engine*

*3406, 3408, 3412 D348, D349 3512, 3508, 3516 D379, D398, D399

Engine DrivenJacket water Pump

Heat Exchangeror Keel Cooler

Piping:

Part of Engine

Supplied by Installer

— EXPANSION TANK —CONTROLLED INLET THERMOSTATS

Figure 1.1

The expansion tank and cooler perform thesame function as the radiator. A radiator fanprovides air flow through the cooling fins ofthe radiator to transfer coolant heat to the air.An external water supply is used toaccomplish heat transfer when using a heatexchanger or keel cooler.

The inlet temperature controlled systemprovides less cycle temperature variationbecause mixing of the by pass jacket waterand the cooled water takes place in theexpansion tank before passing to the jacket

water pump. The volume of water already inthe expansion tank dilutes and smooths thetemperature change rate.

With the simpler outlet control system,mixing occurs at the water pump inlet andtemperature change (or cycles) may be moresudden and drastic. This can pose seriousproblems where the sea water is very coldand may require some special trimming ormodification of the vessels cooling circuit.

3

Outlet

Engine Thermostat

C

B

A

Return

BypassLineR

adia

tor

Engine DrivenJacket water Pump

A-B: Cold Bypass FlowA-C: Full External Flow

AllEngineModels

Piping:

Part of EngineSupplied by Installer

— RADIATOR —CONTROLLED OUTLET THERMOSTATS

Figure 1.2

Heat Exchanger Cooling forJacket WaterHeat exchangers can be mounted either onthe engine or remote from the engine.Engine-mounted heat exchangers require theleast amount of pipe fitting since the jacketwater connections to the heat exchanger areprovided by the factory.

Remote-mounted heat exchangers requireconnecting the jacket water inlet and outlet atthe engine to the shell side of the exchanger.As shown below, an engine driven seawaterpump is used to circulate the cooling waterthrough the tubes of the heat exchanger.

4

11 13

1313

1412

6

5

10

34

1

2

9

87

JACKET WATER AFTERCOOLEDHeat Exchanger

1. Turbocharger2. Aftercooler, jacket water cooled3. Jacket water outlet connection4. Jacket water inlet connection5. Expansion tank6. Jacket water pump7. Auxiliary pump, seawater

8. Seawater inlet connection 9. Seawater outlet connection10. Pressure cap11. Duplex full-flow strainer12. Heat exchanger13. Shut-off valve14. Seawater intake

Figure 1.3

Keel Cooling for Jacket WaterA keel or skin cooler is an outboard heatexchanger which is either attached to thesubmerged part of a vessel’s hull or built as apart of it. Jacket water is generally circulatedthrough the cooler by the engine’s waterpump.

Water SpecificationsCaterpillar used two water classifications:fresh water and seawater.

Fresh WaterFresh water refers to drinkable water. Prior tochemical water treatment for engine corrosioninhibiting, it must be in a pH range of 5.5 to9.0, containing no more than 40 ppmchlorides. Total dissolved solids must be lessthan 340 ppm. Total sulfates must be no morethan 100 ppm. Total hardness must be lessthan 170 ppm. This is the cooling water that isused within the engine’s jacket water system.

SeawaterSeawater refers to salt water, river water, lakewater and all waters that do not meet thefresh-water requirement. Heat exchangercomponents in contact with this water shouldbe copper-nickel construction, or equivalent,highly corrosion resistant material. This is notthe water retained within the engine’s jacketwater system.

5

11

12

6

2

9

7

10

10

1

3

10

10

JACKET WATER AFTERCOOLEDKeel Cooler

1. Turbocharger2. Aftercooler, jacket water cooled3. Jacket water outlet connection4. Jacket water inlet connection5. Expansion tank6. Jacket water pump

7. Keel cooler 8. Bypass filter 9. Duplex full-flow strainer10. Shut-off valve11. Auxiliary expansion tank12. Flexible connection

Figure 1.4

4

8

5

Chemical Water Treatment forEngine Corrosion InhibitingAll jacket water must be treated withchemicals for satisfactory engine life. Evenpotable water is not suitable for use by itself,except for short periods of time (during seatrials or during an emergency). It is goodpractice to chemically protect or drain enginejacket water before storage or extendedtransportation of the engine. This is necessaryto avoid corrosion and scale from forming inthe system. The resulting cooling solution(mixture of proper pH water and corrosioninhibitors) should have a pH in the range of5.5 to 9.

Water Softener-Treated WaterWater that has been softened (chemicallytreated to lower the mineral content) by theaddition of chlorides cannot be used in thecooling system. Water that is softened by theremoval of calcium and magnesium can beused.

Chromate Corrosion InhibitorsInhibitors containing chromate compoundsshould not be used in Caterpillar Enginecooling systems. The concentration ofchromate solutions is difficult to control andthese solutions are extremely toxic. Beforedilution, they can damage human skin. Stateand local regulations severely limit dischargeof chromate solutions into inland and coastalwaters.

Soluble OilSoluble oil is not recommended for coolingsystem protection.

AntifreezeThe climate where the engine will be usedwill determine the need for antifreeze. Ifantifreeze is needed, Caterpillar dealers canrecommend specific types. Corrosioninhibitors are required. Some antifreezeproducts do not contain corrosion inhibitors.If the antifreeze chosen does not containcorrosion inhibitors, corrosion inhibitors mustbe added separately. Some antifreezesolutions, because of their higher viscosity(thicker than plain water), will reduce thecooling systems heat transfer capacity. Do notuse higher than required concentrations of

antifreeze. This practice can cause engineoverheating. Antifreeze does not lose itsability to give freeze protection, but theadditives in the antifreeze wear out with timeand the antifreeze will not give certain otherprotection to the cooling system. Replaceantifreeze periodically or add maintenancequantities of the additives, as directed by theantifreeze manufacturer.

Watermakers, Domestic WaterHeaters, Cabin HeatersWatermakers, domestic water heaters andcabin heaters can put normally-wasted jacketwater heat to work. This has the potential forrecovery of approximately 15% of the fuelinput energy.

Certain aspects of the engine cooling systemmust be thoroughly understood to avoidmisapplication. For example, an engine willonly produce significant amounts of wasteheat if there is a significant load on theengine. Many engines in marine service arelightly loaded for large parts of their life andare poor choices for installation ofwatermakers, domestic water heaters, andcabin heaters. When an engine is lightlyloaded, almost all of the engine’s jacket waterflow goes through a bypass line, from thethermostat housing to the jacket water pumpinlet, to maintain a constant high flow throughthe engine’s cooling passages.

Watermakers, domestic water heaters andcabin heaters can overcool an engine.

If the watermaker, domestic water heater, orcabin heater extracts too much heat from theflow of jacket water, the engine’s watertemperature sensors/thermostats will sensethe engine cooling jacket is operating at adangerously low temperature. It will attemptto correct the condition by reducing theexternal flow of cooling water. If there areautomatic controls on the watermaker,domestic water heater, or cabin heater, it mayshut off having sensed insufficient flow forcontinued operation. This leads to atroublesome condition of repetitive startingand stopping of the watermaker, domesticwater heater, or cabin heater. Automaticcontrol of these devices has proven

6

troublesome and is not recommended.Consider the use of auxiliary jacket waterheaters so during periods of light engine load,adequate amounts of heat can be sent to thewatermaker, domestic water heater, or cabinheater.

Cooling water piping to and from thewatermakers, domestic water heaters, andcabin heaters must not allow entrainedair/gases to collect. Trapped air/gases willdisplace the water required to carry engineheat to the watermakers, domestic waterheaters, and cabin heaters and interfere withproper operation. Trapped air/gases can bevented by installing small, approximately 3 mm (0.125 in.), inside diameter-vent lines.The vent lines should carry air/gases fromthe high points in the domestic water heaterand its associated piping to a higher point inthe engine jacket water cooling circuit—normally an installer-supplied auxiliaryexpansion tank.

See the engine general dimension drawing forthe connection locations of points on theengine where water for this purpose shouldbe extracted and returned.

Watermaker ControlsThe watermaker controls may be eithermanually operated valves or thermostaticallycontrolled valves.

Any failure of the water maker control system(electrical, air, etc.) must shut off jacket waterflow to the watermaker and return the flow tothe engine heat exchanger.

The thermostat valve, shown in the figuredescribing automatic control watermakercircuit, would have a temperature setting thatwill not interfere with the engine thermostats.This valve should begin to divert water flow tothe engine heat exchanger at no more than88°C (190°F) and be fully diverting at 96°C(205°F). For safety, the bypass valve(s) in theengine heat exchanger circuit should contain6.35 mm (0.25 in.) orifices so there will be aslight water flow in case all valves areinadvertently left closed. This orifice is thenrequired to assure water flow to actuate analarm system. If the watermaker cannothandle the full heat rejection of the engineand/or cannot handle the full water flow ofthe engine, the automatic system must beused.

7

8

MANUAL CONTROL WATERMAKER CIRCUIT

Water-Maker

Flexible Connectors

Engine Jacketwater

Return Outlet

ShutoffValves

Engine Cooler

BypassValve6.35 mm (.25 in.)Orifice

Figure 1.5

AUTOMATIC CONTROL WATERMAKER CIRCUIT

Water-Maker

Engine Jacketwater

Return Outlet

Engine Cooler

Flexible Connectors

ShutoffValves

BypassValve6.35 mm (.25 in.) Orifice

ThermostaticallyControlled Valve

B-A: Normal FlowC-A: Bypass Flow

A

B C

Figure 1.6

Interconnecting EnginesSeveral problems arise from interconnectionof several engines: unequal water flow, onefailure shuts down all engines, excessiveexternal head pressures, etc. For thesereasons, separate connection of one engineper watermaker is recommended. It is thecustomer’s responsibility to provide a systemthat is compatible with the engine coolingsystem in all modes of operation.

When the Watermaker is Far from theEngineWhen the watermaker is a long distance fromthe engine or where the watermaker requiresa constant water flow, a mixing tank andcirculating pump is required. Do not use acirculating pump by itself, because thecirculating pump head pressure will damagethe engine thermostats in the event they areclosed. Although the mixing tank is notCaterpillar supplied, it can be used with eitherof the suggested circuits. An auxiliaryelectrical heater may be installed as shown.

Aftercooler SystemsCaterpillar uses two types of cooling circuitsfor the aftercooler. One type provides enginejacket water for cooling the air in theaftercooler. The other type provides aseparate cooling circuit for the aftercooler. Allaftercooled Caterpillar Engines applied in amarine environment should be equipped with aseawater-type aftercooler core to assuresatisfactory core life.

Jacket Water AftercoolingJacket water aftercooling uses engine jacketwater in the tube side of the aftercooler andresults in inlet manifold temperatures lowerthan those obtained in nonaftercooledturbocharged engines. The lower inletmanifold air temperature allows a jacket wateraftercooled engine to achieve a rating higherthan either a naturally aspirated orturbocharged-only engine. Jacket wateraftercooled circuits are completely installed atthe factory.

9

AuxiliaryHeater

CirculatingPump

C

C

D

D

A

A

B

B

MixingTank

Watermaker

To Watermaker ShutoffValves

Figures 1.5 and 1.6

250 to 300 mm (10 in. or 12 in.)Schedule 40 Pipe600 mm (24 in.) Long

1/2 CircleSegment

Figure 1.7

Separate Circuit AftercoolingAs the name implies, the separate circuitaftercooler circuit, SCAC, provides water tothe aftercooler from a source other thanengine jacket water. It is used to providecolder water to further reduce inlet manifoldair temperatures.

The two arrangements of the separate circuitaftercooled engine configuration provideeither an open seawater circuit or a closedfresh-water circuit for the aftercooler water.

10

7 2

93

4

5

6

1110

8

1

SEPARATE CIRCUIT AFTERCOOLED

1. Turbocharger2. Aftercooler, auxiliary water cooled3. Jacket water outlet connection4. Jacket water inlet connection5. Expansion tank6. Jacket water pump

7. Auxiliary water pump 8. Auxiliary water inlet connection 9. Auxiliary water outlet connection10. Lines to aftercooler cooler11. Lines to jacket watercooler

Figure 1.8

Seawater AftercoolingEngines equipped with seawater aftercoolersuse untreated water in the tube side of theaftercooler. Seawater refers not only to saltwater but also includes river water, lake wateror any source of untreated water. Use ofseawater for aftercooling

achieves inlet manifold air temperatures lowerthan those resulting from jacket water orseparate circuit fresh water aftercooling. Thislower inlet manifold air temperature permitsratings of seawater aftercooled engines toexceed those for jacket water aftercooledengines.

11

15

12

14

13

1313

11

43

98

7 2

1

10


1. Turbocharger2. Aftercooler, seawater cooled3. Jacket water outlet connection4. Jacket water inlet connection5. Expansion tank6. Jacket water pump7. Auxiliary seawater pump8. Auxiliary seawater inlet connection

9. Aftercooler outlet connection 10. Pressure cap 11. Duplex full-flow strainer 12. Heat Exchanger 13. Shut-off valves 14. Seawater intake 15. Seawater discharge

Seawater Aftercooled

Figure 1.9

6

5

Separate Keel Cooler for AftercoolerThe use of keel or skin coolers in theaftercooler circuit allows a low temperature,fresh water closed circulating system to beused. All closed fresh water aftercoolercircuits require the installation of anexpansion tank. Refer to the section ofauxiliary expansion tanks. The use of an inletmanifold air temperature gauge, or alarm, canprovide guidance for required cleaning of thesystem in order to maintain the desiredengine performance. The use of an inletmanifold air temperature sensing device isstrongly recommended.

Caution must be used when using theaftercooler keel cooler water circuit to cool anauxiliary piece of equipment (i.e. marinetransmission). The auxiliary equipment coolershould be connected to the water circuit afterit leaves the engine aftercooler to avoidadding any heat to the water before it entersthe aftercooler. The additional resistance ofthe auxiliary equipment cooling circuit mustbe held to a minimum to avoid reducing theflow of water to the aftercooler.

12

1516

17

18

5

2

1

8

9 34

6

111211

11 11

111211

11 11

13

1010

14

SEPARATE CIRCUIT AFTERCOOLEDKeel Coolers

1. Turbocharger2. Aftercooler, keel cooled3. Jacket water outlet connection4. Jacket water inlet connection5. Expansion tank6. Jacket water pump7. Auxiliary fresh water pump8. Auxiliary fresh water inlet connection9. Aftercooler outlet connection

10. Bypass filter11. Shut-off valve12. Duplex full-flow strainer13. Keel cooler for aftercooler14. Keel cooler for jacket water15. Expansion tank for aftercooler circuit16. Vent line for aftercooler circuit17. Auxiliary expansion tank18. Flexible connection

Figure 1.10

7

Heat Exchanger for AftercoolerA shell and tube type heat exchanger will alsoprovide cooling for fresh aftercooler water ifthe seawater temperatures are cold enough toprovide adequate cooling. The use of aninboard shell and tube type heat exchangerfor the aftercooler circuit requires the use of aseawater pump in addition to the freshwaterpump used to circulate water through theaftercooler. An expansion tank is alsorequired for the aftercooler circuit.

Overcooling of Aftercooler AirThe separate circuit aftercooler coolingsystem must be designed with sufficientcapacity for the hottest water and the higher

ambient air conditions for operation inclimates where both air and seawatertemperatures run to extremes. This results ina cooler with excess capacity in cold seawaterand warm air conditions. This will result incondensation in the engine’s intake system,especially during prolonged light engine load.Extremely cold seawater in the aftercoolercan also cause condensation when engineinlet air temperatures are relatively warm withhigh moisture content. To minimizecondensation during light engine load inseparate circuit aftercooled systems, it isdesirable to maintain the inlet manifoldtemperature between 38°C and 52°C (100°Fand 125°F). This may be achieved by

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15

10

13

12

16

14

17

18 1

2

6

5437

89

19

11 11 11

11

SEPARATE CIRCUIT AFTERCOOLERHeat Exchangers

1. Turbocharger 2. Aftercooler, heat exchanger cooler 3. Jacket water outlet connection 4. Jacket water inlet connection 5. Expansion tank 6. Jacket water pump 7. Auxiliary fresh water pump 8. Auxiliary fresh water inlet connection 9. Aftercooler outlet connection10. Pressure cap

11. Shut-off valve 12. Duplex full-flow strainer 13. Heat exchanger for aftercooler 14. Heat exchanger for jacket water 15. Customer provided seawater pump 16. Seawater intake 17. Seawater discharge 18. Expansion tank for aftercooler circuit 19. Vent line for aftercooler circuit

Figure 1.11

recirculating the aftercooler cooling waterback to the auxiliary water pump inlet untilthe desired temperature is reached. Coolwater should then be mixed with therecirculated water to maintain thetemperature. The temperature of the water tothe aftercooler can be controlled by using athermostatically controlled three-way valve.

On closed circuit keel cooled or heatexchanger systems, the aftercooler water isbypassed around the cooler until it reachesthe desired aftercooler inlet temperature. Onseawater aftercooled engines, the warmedwater from the heat exchanger is recirculatedto the aftercooler until the desired aftercoolerinlet water temperature is obtained. Thethermostat valve used must be capable ofbeing used continuously in seawater and beequipped with electrolytically compatiblecomponents.

14

1516

17

11

11 11

1111 11

1413

12 12

10 10

11 11

1

27

8

43

5

6

9

1. Turbocharger 2. Aftercooler, keel cooled 3. Jacket water outlet connection 4. Jacket water inlet connection 5. Expansion tank 6. Jacket water pump 7. Auxiliary fresh water pump 8. Auxiliary fresh water inlet connection 9. Aftercooler outlet connection

10. Bypass filter 11. Shut-off valve 12. Duplex full-flow strainer 13. Keel cooler for aftercooler 14. Keel cooler for jacket water 15. Expansion tank for aftercooler circuit 16. Vent line for aftercooler circuit 17. Bypass valve thermostatically controlled 18. Auxiliary expansion tank 19. Flexible connection

SEPARATE CIRCUIT AFTERCOOLEDAftercooler Keel Cooler Bypass

Figure 1.12

18

19

The thermostatic valve used should not allowthe temperature of the water to the aftercoolerto exceed 30°C (85°F). The keel cooler, heatexchanger and marine transmission oil coolerused must be sized for this maximumtemperature. A thermostatically controlled3-way valve that is equipped with a remotesensor to monitor the inlet manifold airtemperature can be used. Adjust the remotesensor to insure that the thermostatic valvedoes not permit recirculation when the inletmanifold temperature reaches 49°C (120°F).

It is important that water be recirculatedrather than be throttled to reduce flow. It isessential that unrestricted water flow throughthe aftercooler be maintained regardless oftemperature conditions. Size thermostaticvalve plumbing to have internal diameters aslarge or larger than the inlet connection of theauxiliary pump. Use an air intake manifoldtemperature alarm set for 52 to 57°C (125 to135°F) maximum to warn of systemmalfunction.

15

10

5

6

4

93

1

27

8

11 13

14

15

1612

1313


1. Turbocharger2. Aftercooler, seawater cooled3. Jacket water outlet connection4. Jacket water inlet connection5. Expansion tank6. Jacket water pump7. Auxiliary seawater pump8. Auxiliary seawater inlet connection

9. Aftercooler outlet connection 10. Pressure cap 11. Duplex full-flow strainer 12. Heat Exchanger 13. Shut-off valves 14. Seawater intake 15. Seawater discharge 16. Bypass Valve-themostatically controlled

Aftercooler Seawater Recirculation

Figure 1.13

In situations where condensation can be aproblem, a corrosion-resistant water trap canbe attached to the intake manifold(s) of theengine.

Seawater SystemGeneralThe installation, size and material of theseawater suction lines is extremely important.

SizeFlow restriction in the sea water suctionpiping will result in abnormally high enginetemperatures which can lead to unscheduledshutdowns and, in severe cases, reducedengine life. To minimize flow restriction, pipesand hoses should be at least as large as thesea water pump suction opening.

If the distance to the thru-hull fitting or seachest is large or if many pipe elbows or bendsin the hose are used, the pipe or hose sizeshould be one size larger than the sea waterpump opening (suction connection). In nocase should the sea water pressure, measuredat the sea water pump suction, be less than 24 kPa (3.5 psi) vacuum.

Suction Line Design ConsiderationsOn the inlet side of the pump, as much aspossible of the seawater piping, should bebelow the vessel water line without air traps.

16

CONDENSATE VALVE GROUP

IntakeManifoldElbow

Nipple

Bushing

Valve Outlet

ManifoldDrain Valve

Figure 1.14

Install a water pressure actuated check valvedownstream of the strainer and as close to itas possible. The function of the check valve isto prevent water from draining out of thepump inlet while the pump is not operatingand during cleaning of the strainer. Install avent valve between the strainer and the checkvalve to allow venting of trapped air aftercleaning the strainer and opening the seacock. If the pump is above the vessel waterline, install a piping loop above the pump inletelbow to trap enough water to keep the pumpand priming chamber filled.

Sea Water Inlet DesignConsiderationsThe Sea water inlet serves the followingfunctions:

• Provides a low restriction connection forthe seawater inlet plumbing.

• Provides a connection point for the SeaCock (seawater shutoff valve—installedbetween the sea water inlet and theseawater inlet plumbing).

• Provides a way to separate air from the seawater required for cooling. Sea chests musthave vent connections to allow air, forcedunder the hull during maneuvering, to bepurged before it is able to reach thecentrifugal seawater pump.

17

CENTRIFUGAL SEAWATER PUMP INLET PLUMBING

Priming Chamber

Pump

Loop

Check ValveVent Valve

Strainer

Sea Cock

Sea Chest

Figure 1.15

Seawater PumpsCaterpillar offers three types of seawaterpumps:

• Rubber Impeller• Water Ring• Centrifugal

Rubber Impeller Seawater PumpsRubber impeller seawater pumps arecharacterized by excellent primingcharacteristics, though they often sufferrelatively short life in abrasive waters.

Water Ring Seawater PumpsTheir priming characteristics are less thanrubber impellers, but can lift up to 1.5 m (5 ft)Caution: A goose neck may be necessarywith these pumps to keep water in the pumpfor priming. They are made entirely ofcorrosion resistant metals, with noelastomeric components.

Centrifugal Seawater PumpsCentrifugal Seawater Pumps must be installedwith their inlet below the boats light waterline.Air allowed to enter centrifugal seawaterpumps will likely result in loss of prime andprobable engine damage due to loss of

cooling. Do not start an engine equipped witha centrifugal pump unless the pump andpriming chamber are full of water.

MaterialAn excellent material for piping carryingseawater is of the copper- nickel alloys. Thecost of such piping makes its use unusual forall but the most critical systems.

The material of all the seawater piping shouldbe the same, whenever practical. If parts ofthe seawater piping, made of different metals,make contact with each other, one of themetals will corrode, sometimes very rapidly.

The materials will corrode according to theirposition in the electromotive series. Seeelectromotive series chart in section of UsefulTables to Designers of Cooling Systems.

Black iron pipe is often used in seawaterservice (replacement should be planned everytwo or three years). If it is necessary to usepipe or other cooling system components ofmore than one material, avoid letting thedissimilar metals touch, even by mutualcontact with an electrically-conductive thirdmaterial.

18

Hull

Strainer

Main Deck

Air Vent(Used On VesselsOver 25 m (75 ft) Only)

1/4 TurnSea

Cocks

SeaWaterPump

Figure 1.16

Corrosion will be much more severe if a flowof electrons is able to pass freely from one ofthe metals to the other.

Seawater StrainerPurposeStrainers protect the seawater pump, heatexchanger and other cooling systemcomponents from foreign material in theseawater. The foreign material can plug orcoat heat transfer surfaces, causingoverheating of the engine. If abrasive, foreignmaterial will erode pump impellers and softmetal parts, reducing their effectiveness.

LocationInstall strainers below the boat’s water lineand as close to the sea water intake or seachest as possible (adjacent to the sea cock).The strainer must be installed so it can beeasily cleaned, even in the worst weatherconditions.

TypeWhile simplex strainers, which require shutoffof the sea water flow, are adequate to protectthe engine, greater safety will result fromusing duplex strainers, which can be cleanedwithout interrupting sea water flow or enginepower.

SizeWell sized strainers will impose no more than9 kPa (3 ft of water) restriction to flow at fullseawater flow conditions. Suppliers can helpin the proper selection of strainer size byproviding the flow restriction of each size ofstrainer at varying water flow conditions.

Mesh DimensionsRecommended strainer media (screens)should not pass solid objects larger than1.6 mm (1/16 in.) in diameter.Plate type heatexchangers require a mess less than 3 mm,while the tube type heat exchangers requiresa mess less than 5 mm.

Strainer Differential Pressure SensorsSchools of small fish, floating debris (plasticbags, plant material, etc.) or ice chips canplug a clean strainer in a few seconds. Whenthe differential pressure across theconnections of a strainer goes too high, thestrainer needs to be cleaned. A differential

pressure switch, will provide early warning ofstrainer plugging and resultant loss of enginecooling. In time, high engine watertemperature alarms will also warn of a loss ofsea water flow, but the differential pressuresensor will give early warning and the preciselocation of the problem.

Zinc PlugsGeneral InformationZinc plugs are installed in portions of theengine where dissimilar metals must be usedin the presence of seawater. Their sacrificialaction protects critical cooling systemcomponents from corrosion.

Inspection ScheduleInspect the zinc plugs within 24 hours offilling the piping with sea water. If nosignificant corrosion is noted, inspect themagain after 7 days of sea water submersion. Ifno significant deterioration is noted, reinspectin 60-90 days. Thereafter, inspect annually andreplace if necessary.

Thread Sealant on Zinc Plug ThreadsInstall zinc plugs with clean threads. Neverinstall zinc plugs using teflon tape ornonelectrically- conductive pipe sealers. Theinsulating properties of such sealers will stopthe protective action of the zinc plugs.

Marine GrowthMarine plants and animals will enter seawaterpiping and take up residence there. Manyforms of sea life are very comfortable withinengine cooling system piping and will grow toa size which will threaten adequate flow. Thelack of predators, darkness and abundance ofsuspended food particles combine to createprime growth conditions for sponges,barnacles and like creatures. Strainers are noprotection against creatures which aremicroscopic in size during their infant stagesof life. Periodic operation in fresh water willrid boats of salt water life infestation and viceversa. In any case, it will be necessary toremove and clean piping and heat exchangerpassages of the corpses. Use of high watertemperature alarms, seawater pump pressureswitches, and other instrumentation can warnof gradual loss of seawater flow and arerecommended. Periodic chemical treatmentcombats marine growth. Chemical type and

19

concentration must be controlled to preventdeterioration of the seawater cooling systemcomponents. Contact a knowledgeablechemical supplier. Continuouslow-concentration chemical treatment viaeither bulk chemical or self- generatingelectrical processes are offered by variousmanufacturers.

Seawater Pump MaintenanceFlexible impeller seawater pumps requireperiodic service. The impellers must bereplaced when worn to maintain adequateseawater flow and avoid engine overheating. Itis a good idea to put a little soft soap, like thatused by mechanics for hand cleaning, on thenew impeller just prior to installing it. Thesoap will lubricate the new impeller longenough for it to fully achieve prime,protecting it from overheating. A spareimpeller, for flexible impeller seawater pumps,should be carried on board at all times.

Stern Tube Lubrication/CoolingIt is good practice to divert a small portion ofthe engine’s seawater, before discharging itoverboard, to lubricate/cool the stern tubeand stuffing box (sometimes called thepacking gland). The engine’s seawater hasbeen strained and the flow of water from thestuffing box end of the stern tube will tend tokeep sand or other abrasive material out ofthe stern tube. Avoid using excessivequantities of the engine’s flow of seawater, asthis practice tends to increase the seawatersystem restriction, making the engine morelikely to overheat. Generally 4-12 L/min (1-3 gal/min) are adequate.

Potential ProblemsNonreinforced Seawater PumpSuction HoseThe vacuum inside the Seawater PumpSuction Hose can become quite high. If thehose is not internally reinforced, atmosphericpressure will collapse it. That will severelyimpede the flow of seawater with potentiallydangerous results. Use hose which issufficiently strong to resist collapse due tohigh suction vacuum.

Internal Hose DeteriorationSome hose will shred internally, releasing bitsof rubber which can plug cooling passages. It

is good practice to use good quality hoses. Ifusers are unsure of their hoses’ quality, it isgood practice to examine hoses internally atleast once during their life. Replace them withgood quality hose every three years.

Achieving and Maintaining SeawaterPump PrimePump speeds and suction pressures must fallwithin certain limits for sea water pumps toachieve prime (start pumping water). Thepriming characteristics of Caterpillar seawater pumps are available from the factory.

Sea Water Discharge throughExhaust SystemWet exhaust systems use sea water, after ithas passed through the various heatexchangers and coolers, to cool the hotexhaust gases. After sea water is injected intothe hot exhaust gas (generally immediatelydownstream of the engine’s turbocharger),the temperature of the gas is reduced enoughto allow use of sections of rubber hose,fiberglass-reinforced plastic pipe or othersimilar materials to be used as exhaust pipe.It is critical that nothing interfere withthe flow of sea water which cools theexhaust gas. Anytime the engine isoperating, the flow of seawater must bepresent.

System CoolersThere are two types of heat exchangingsystems recommended for use with theCaterpillar Diesel Marine Engines. Theseinvolve the use of either inboard mountedheat exchangers or outboard mounted keelcoolers.

Heat Exchanger CoolingCaterpillar inboard heat exchangers areshell-and-tube type or plate type. Heat istransferred from the hot, fresh water flowingthrough the engine to the cold sea water.

Heat exchanger cooled systems require a seawater pump to circulate sea water through theheat exchanger tubes or plates. It is gooddesign practice to “always put the seawaterthrough the tubes”. The tubes can be cleanedby pushing a metal rod through them; the

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21

shell side requires chemical cleaning which isonly available at shore-side facilities.

The fresh water is circulated through the heatexchanger shell, across the tubes, by theengine-driven water pump.

Most shell and tube heat exchangers are ofeither the single-pass or the two-pass type.This designation refers to the flow in the coldwater circuit of the exchanger. In the two-passtype, the cold water flows twice through thecompartment where jacket water is circulated;in the single-pass type only once. When usinga single-pass exchanger, the cold watershould flow through the exchanger in adirection opposite to the flow of jacket coolantto provide maximum differential temperatureand heat transfer. This results in improvedheat exchanger performance. In a two-passexchanger, cooling will be equally effectiveusing either of the jacket water connectionpoints for the input and the other for return.

Heat exchangers should always be located ata lower level (elevation) than the coolant levelin the expansion tank.

Heat Exchanger SizingOccasionally, special applications exist whichrequire an inboard heat exchanger size notavailable as a Caterpillar unit. When theseconditions exist, it is necessary to obtain aheat exchanger from a supplier other thanCaterpillar. In order to expedite the selectionof a nonstandard heat exchanger, a HeatExchanger Selection Worksheet is included.Heat exchanger suppliers will provideinformation and aid in selecting the propersize and material for the application.

For a given jacket water flow rate, theperformance of a heat exchanger depends onboth the cold water flow rate and differentialtemperature. To reduce tube erosion, the flowvelocity of the cold water through the tubesshould not exceed 183 cm/s (6 fps).

At the same seater flow rate, the flowresistance and the flow velocity will be greaterthrough a two-pass heat exchanger thanthrough a single-pass heat exchanger. Theheat exchanger should be selected toaccommodate the cold water temperature andflow rate needed to keep the temperaturedifferential of the jacket water below about8.3°C (15°F) at maximum engine heatrejection. Thermostats must be retained in thejacket system to assure that the temperatureof the jacket water coolant returned to theengine is approximately 79°C (175°F).

Size heat exchangers to accommodate a heatrejection rate approximately 10% greater thanthe tabulated engine heat rejection. Theadditional capacity is intended to compensatefor possible variations from published orcalculated heat rejection rates, overloads orengine malfunctions which might increase theheat rejection rate momentarily. It is notintended to replace all factors which affectheat transfer, such as fouling factor, shellvelocity, etc.

Pay particular attention to the shell sidepressure drop to ensure that the entirecooling system flow resistance does notexceed the limitations on the enginefreshwater pump.

Jacket Water

Jacket Water

Single Pass

Two Pass

CoolingWater

HEAT EXCHANGER TYPES

Figure 1.17

22

Heat Exchanger Sizing WorksheetHeat Exchanger Sizing DataRequired by Heat Exchanger Supplier

Engine Jacket Water Circuit:1. Jacket water heat rejection* _________________ kW (Btu/min)

2. Jacket water flow* _________________ L/sec (Gpm)

3. Anticipated seawater maximum temperature _________________ C° (F°)

4. Seawater flow _________________ L/sec (Gpm)

5. Allowable jacket water pressure drop _________________ m (ft) water

6. Allowable seawater pressure drop _________________ m (ft) water

Drop7. Auxiliary water source □ seawater

(sea water or fresh water) □ fresh water

8. Heat exchanger material □ adm. metal(admiralty or copper-nickel) □ cu-ni

9. Shell connection size** _________________

10. Tube side fouling factor*** _________________

Aftercooler Water Circuit:1. Aftercooler circuit water heat rejection* _________________ kW (Btu/min)

2. Aftercooler circuit water flow* _________________ L/s (Gpm)

3. Anticipated seawater maximum temperature _________________ C° (F°)

4. Seawater flow* _________________ L/s (Gpm)

5. Allowable Aftercooler Circuit _________________ m (ft) waterWater Pressure Drop*

6. Allowable seawater pressure drop* _________________ m (ft) water

7. Auxiliary water source □ seawater(sea water or fresh water)* □ fresh water

8. Heat exchanger material □ adm. metal(admiralty or copper-nickel) □ cu- ni

9. Shell connection size** _________________

10. Tube side fouling factor*** _________________

* Refer to TMI (Technical Marketing Information)** Refer to engine general dimension drawing*** Fouling Factor, a descriptive quantity often found on heat exchanger specifications, refers to the heat exchangers

ability to resist fouling. As defined in Caterpillar literature, fouling factor is the percentage of the heat transfersurface which can be fouled without losing the heat exchanger’s ability to dissipate the engine’s full heat load.

Maximum Seawater TemperatureSize heat exchangers such that the seawateris not heated above approximately 54°C(130°F). Higher seawater temperatures willresult in fouling of the heat transfer surfaceswith chalk-like compounds.

Keel CoolersA keel cooler is an outboard heat exchangerwhich is either attached to, or built as part of,the submerged part of a ship’s hull. Theheated water from the engine(s) circuit(s) iscirculated through the cooler by theenginedriven water pump(s).

Keel Cooler TypesFabricated Keel CoolersFabricated keel coolers may be made of pipe,tubing, channel, I-beams, angle or otheravailable shapes. The choice of materials usedis dependent on the waters in which thevessel will operate. These materials must becompatible with materials used in the vessel’shull in order to prevent galvanic corrosion.

Sizing of Fabricated Keel CoolersEngine water temperature maximum limitsare controlled by size of the keel cooler. Heattransfer rates through any cooler dependmainly on cooling water temperature, coolingwater flow and heat transfer surface area. Acooler may have to operate at its maximumcapacity at zero hull speed, as in the case ofan auxiliary generating set, operating whilethe vessel is in port. The minimum areacalculated includes a fouling factor. Materialsused in cooler construction, condition ofwaters in which the vessel will operate andservice life expectancy will influence the sizeselection of a new cooler.

Keel cooler area recommendations containedin the graphs below apply only to keel coolersmade of structural steel (channel, angle, halfpipe, etc.) welded to the ship’s shell plating.These recommendations take into account thethermal resistance to heat transfer of the steelplate, the internal and external water films,and the internal and external surfacecorrosion factors. The coefficient of heattransfer of the fresh water film flowing insidethe cooler is based upon a flow velocity of 0.9 m/sec (3 ft/sec). The coefficient of heattransfer for the raw water film varies with thevelocity of water flow past the cooler due tovessel speed. Surface corrosion factors arebased on treated fresh water and pollutedriver water. Miscellaneous factors become sopredominant in the resultant heat transfer ratethat the type of material used and thickness ofmetal become minor considerations .

Normal deterioration of the cooler’s inner andouter surfaces in the form of rust, scale andpitting progressively reduce a keel cooler’seffectiveness over a period of years. Protectivecoatings and marine growths will also reducethe rate of heat transfer. It can take 4-5 yearsbefore deterioration stabilizes in keel coolers.It must be designed considerably oversize whennew.

Because of the severe deterioration of heattransfer characteristics associated withstructural steel coolers, adequate cooler sizesometimes becomes impractical. This isparticularly true in regions of high seawatertemperature (over 30°C [85°F]). In theseregions, the use of “packaged” keel coolers, orbox coolers, made of corrosion-resistantmaterials is suggested. These coolers canprovide more heat exchange surface area in agiven volume on, or within the hull, than thecoolers made of structural steel.

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Keel Cooler Sizing WorksheetKeel Cooler Sizing WorksheetEngine Jacket Water Circuit:1. Jacket water heat rejection* ______________ kW (Btu/min)

2. Jacket water flow* ______________ L/sec (Gpm)

3. Vessel speed classification □ 8 knots &above

□ 3 knots□ 1 knot□ still water

4. Anticipated seawater maximum temperature ______________ C° (F°)

5. Minimum cooler area required (per unit) ______________ m2/kW

______________ (ft2/Btu/min)

6. Minimum area required (Line 1 times Line 5) ______________ m2 (ft2)

Aftercooler Water Circuit:1. Aftercooler circuit heat rejection* ______________ kW (Btu/min)

2. Aftercooler circuit water flow* ______________ L/sec (Gpm)





______________ (ft2/Btu/min)

6. Minimum area required (Line 1 times Line 5) ______________ m2 (ft2)

Marine Gear Oil Cooling Circuit:1. Marine gear heat rejection** ______________ kW (Btu/min)





______________ (ft2/Btu/min

5. Minimum Area Required (Line 1 times Line 5) ______________ m2 (ft2)* Refer to TMI (Technical Marketing Information)

** See section on Marine Gear Heat Rejection

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Marine Gear Heat RejectionThe Twin Disc marine gears offered byCaterpillar are 95% to 97% efficient, dependingon the service factor.

Maximum heat rejection to the marine gearcooling system is equal to the transmittedpower from the engine multiplied by thepower loss factor.

H (marine gear) = P (engine) x F (power loss)

Where: H marine gear = Heat rejection of themarine gear oil

P engine = Power generated inthe engine andtransmitted throughthe marine gear

F power loss = A factor relating theheat generated in themarine gear oil to the marine gearefficiency

The following conversion factors are tabulatedbelow.

31.63 x kW = Btu/min42.41 x hp = Btu/min

Marine GearEfficiency

MarineGear PowerLoss Factor

ServiceFactor

97%97%96%95%

3%3%4%5%

IIIIIIIV

Aftercooler Circuit Keel Cooler Area Graph

AFTERCOOLER WATER KEEL COOLER AREA REQUIREMENTS

8K

nots

and

Above

1 Knot

StillWater

3 Knots

300C (850F)Rating0C

23.9

21.1

18.3

15.6

12.8

10.0

7.2

4.4

1.7

0F75

70

65

60

55

50

45

40

35

430C (1100F)Rating

0C 0F100

95

90

85

80

75

70

65

60

37.8

35.0

32.3

29.4

12.8

23.9

21.1

18.3

15.6

An

tici

pat

ed M

axim

um

Sea

Wat

er T

emp

erat

ure

These Requirements Apply To KeelCoolers Made Of Structural Steel OnlyConsider Use of "Packaged" KeelCoolers Made Of Corrosion-ResistantMaterials Where Sea Water TemperatureMay Exceed 650F

.01 .03 .05 .07 .09 .11 .13 .15 sq. ft per Btu/min

.05 .16 .26 .37 .48 .58 .69 .79 sq. m per kW

Cooler Area Required

Figure 1.18

26

JACKET WATER KEEL COOLER AREA REQUIREMENTS


An

tici

pat

ed M

axim

um

Sea

Wat

er T

emp

erat

ure

8 K

nots

and

Abo

ve3

Kno

ts

1 Kno

ts

Still

Wat

er

(Per Revision of 8/11/90)

Thermostats start open 790C (1750F) or above

0F85

80

75

70

65

60

55

50

45

40

35

0C29.4

26.7

23.9

21.1

18.3

15.6

12.8

10.0

7.2

4.4

1.7

.006

.032

.007

.037

.008

.042

.009

.048

.010

.053

.011

.058

.012

.063

.013

.069

.014

.074

.015

.079

sq ft per Btu/minsq mper kW

These Requirements Apply To KeelCoolers Made of Structural Steel Only.

Consider Use of Packaged KeelCoolers Made of Corrosion-ResistantMaterials Where Sea Water TemperatureMay Exceed 180C (650F)

Figure 1.19

Jacket Water Circuit Keel Cooler Area Graph

27

Design/InstallationConsiderationsWater Velocity Inside the CoolerIf the water flows through the keel coolerspassages too fast (more then 2.5 m/sec [8 ft/sec]), the internal components willdeteriorate (be eroded away), particularlynear manifold entrances and exits, elbows andother discontinuities in the water flow. If thewater flows through the keel coolers’passages too slowly (less than 0.6 m/sec [2ft/sec]) rust particles, sand, or otherparticulate matter in the water will settle out,tend to choke off the flow, and degrade thetransfer of heat. Use the following procedureto determine the proper flow pattern throughthe keel cooler:

• Determine the maximum and minimumexpected water flow through the keelcooler. This can be determined from theengines water pump performance data.

• Subtract the minimum expected water flowfrom the maximum expected water flow.

• Multiply the resultant difference (betweenthe min and max flow) by 2/3. Add 2/3 theresultant difference (from the prior step) tothe minimum flow*. This is the most likelywater flow. Use this figure to determinehow to distribute the water flow throughthe keel cooler passages.

• Determine the cross-sectional area of onekeel cooler passage. This is best done byconsulting the manufacturer or anengineering reference on shapes ofstructural channel, pipes, angles, etc.

• Use a good conversion factor table toconvert: the most likely water flow to unitsof m3/min (ft3/min), and cross-sectionalarea of one keel cooler passage to units ofm2 (ft2).

*For design purposes, this is the most likely water flowthrough the keel cooler. This is dependent on the useof good practice in sizing the connecting piping.

Marine Gear Oil Cooling Circuit Keel Cooler Area Graph

Transmission Keel Cooler Area Requirements350C (950F) Max Water to Transmission Heat Exchanger


An

tici

pat

ed M

axim

um

Sea

Wat

er T

emp

erat

ure

These Requirements Apply To KeelCoolers Made Of Structural Steel Only.

Consider Use Of Packaged KeelCoolers Made Of Corrosion-ResistantMaterials Where Sea Water TemperatureMay Exceed 650F

.01

.05

.03

.16

.05

.26

.07

.37

.09

.48

.11

.58

.13

.69

.15

.79

85

80

75

70

65

60

55

50

45

0F30

26.7

23.9

21.1

18.3

15.6

12.8

12.0

7.2

0C

sq ft per Btu/min

m per kW

8 Kno

ts a

nd A

bove

1 Knot

Still W

ater

3 Knots

Figure 1.20

• Divide the most likely water flow by thecross-sectional area of one keel coolerpassage.

• The result will be the average velocitythrough the keel cooler flow passages. Ifthe average velocity through the keelcooler flow passages is greater than 2.5 m/sec (8 ft/sec), arrange the water flowin parallel, so it passes through two ormore of the keel cooler passages per passthrough the keel cooler. If the averagevelocity through the keel cooler flowpassages is less than 0.6 m/sec (2 ft./sec),use a keel cooler passage with a smallercross section.

Use of Keel Inserts to Improve LocalFlow VelocityIt is economically desirable to use steelchannels for keel cooler passages which areso large in the cross-sectional area that waterflow is too slow for effective heat transfer. It isuseful in this situation to install keel coolerInserts. Keel cooler Inserts are devices whichcause localized high water velocity orturbulence within the keel cooler passage. Aneffective design for keel cooler inserts is aladder-like device, inserted into the full lengthof the keel cooler passages.

Using the same metal alloy as the hull andkeel cooler*, fabricate a crude ladder of rod**and flat bar***.

The flat bar cross pieces must not restrictflow through the keel cooler flow passages,but simply redirect the flow to avoid laminarflow due to too slow an average velocity.

Insert the ladder into the keel cooler flowpassages and weld on the end fittings (inletand outlet manifolds).

Direction of Flow Through KeelCoolersEngine coolant should flow through the keelcooler from the rear to the fore end. This iscounter-flow to the seawater and willsignificantly increase the effectiveness of theheat transfer. This is rarely practical toimplement completely since the flow must bedivided through the various flow passages inthe keel cooler. If the flow is divided through

too many passages, the velocity becomes tooslow to maintain turbulent flow conditions.

This will reduce heat transfer. The bestcompromise is to manifold the coolant in sucha way that the flow, in the largest practicalnumber of flow passages, is from rear to thefore end of the vessel.

Bypass FiltersWelded structural steel keel or skin coolersystems require the installation of strainersbetween the cooler and the pump inlet.Material, such as weld slag and corrosionproducts, must be removed from the systemto prevent wear and plugging of coolingsystem components. Use a continuous bypassfilter to remove smaller particles andsediment. The element size of the continuousbypass filter should be 20 to 50 microns(0.000787 to 0.000197 inches). Do not exceed19 L/min (5 gal/min) water flow through thebypass and filter.

StrainersFull-flow strainers are desirable. The strainerscreens should be sized no larger than1.6 mm (.063 in) mesh for use in closedfreshwater circuits. The strainer connectionsshould be no smaller than the recommendedline size. The use of a differential pressuregauge across the duplex strainers will indicatethe pressure drop, and enables the operator todetermine when the strainers need servicing.

The pressure drop across a strainer at themaximum water flow must be considered partof the system’s external resistance. Supplierscan help in the proper selection of strainersand furnish the values of pressure drop versusflow rate. The strainer should be selected toimpose no more than 3 ft (1 m) waterrestriction to flow under clean strainerconditions.

Packaged Keel CoolersPackaged keel coolers are purchased andbolted to the outside of a ship’s hull.

* For protection against galvanic corrosion.** Approximately 6 mm (1/4 in) Diameter.

*** Approximately same shape, but 70% of, the crosssectional area of the keel cooler flow passages.

Manufacturers offer keel coolers in manyconfigurations. They are generally made of

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coppernickel alloys and are initially toxic tomarine growth. This is one of their moreimportant advantages. Another importantadvantage of packaged keel coolers is theircompactness and light weight when comparedto fabricated keel coolers. It is not uncommonto find packaged keel coolers that are able tocool an engine with less than 20% of the heattransfer surface of an analogous fabricatedkeel cooler.

Sizing of Packaged Keel CoolersManufacturers of packaged keel coolerspublish sizing guides which will allow theuser to determine the proper size of unit forspecific conditions. Caterpillar does not offerguidance outside of manufacturers guidelines.

Packaged Keel Cooler SizingWorksheetCollect the information described on thefollowing worksheet. The information thereonis required to accurately size a packaged keelcooler.

Packaged Keel Cooler Sizing Worksheet

Engine Jacket Water Circuit:1. Jacket water heat rejection* _______________ kW (Btu/min)

2. Jacket water flow* _______________ L/s (Gpm)

3. Vessel speed classification □ 8 knots & above□ 3 knots□ 1 knot□ still water

4. Anticipated seawater maximum temperature _______________ °C (°F)

Aftercooler Water Circuit:1. Aftercooler circuit heat rejection* _______________ kW (Btu/min)

2. Aftercooler circuit water flow* _______________ L/s (Gpm)

3. Vessel speed classification □ 8 knots & above□ 3 knots□ 1 knot□ still water

4. Anticipated seawater maximum temperature _______________ °C (°F)

*Refer to TMI (Technical Marketing Information)

Restoration of Toxicity-to-MarineGrowth of Copper Nickel KeelCoolersThe toxicity will decline in time. It can be atleast partially restored by a thorough cleaningof the cooler and wiping its heat transfersurfaces with a solution of vinegar saturatedwith salt (sodium chloride).

Paint and Packaged Keel CoolersPaint will greatly reduce the heat transfercapability of packaged keel coolers. Neverpaint them.

Packaged Keel Coolers and GalvanicCorrosionPackaged keel coolers are almost never madeof the same metal alloy as the rest of thehull*. If the piping is not the same metal alloyas the keel cooler, it is necessary toelectronically isolate the packaged keel coolerfrom the hull metal and the ship’s piping.

*There is a manufacturer making packaged keel coolersof aluminum alloy. This will significantly reduce thegalvanic corrosion problems associated with suchdissimilar metals as aluminum and copper nickelsubmerged in salt water.

See the installation instructions of thepackaged keel cooler manufacturer.

Location of Keel Coolers on the HullLocate the keel cooler in a well protected areaon the hull. This is particularly true ofpackaged keel coolers which aremanufactured of lighter gauge material thanfabricated keel coolers.

To achieve the greatest possible heat transfer,locate the separate keel cooler for theaftercooler low on the hull, forward of the keelcoolers, for the main and electric set enginejacket water. Heated water from theaftercooler should enter the keel cooler at therear-most end and be discharged from thecooler for return to the engine at the cooler’sforward end. This arrangement assuresmaximum heat transfer with the vessel eitherdead in the water or moving ahead.

While the area immediately forward of thepropeller(s) is a region of high water velocityand high enough on the hull to be protectedfrom grounding damage, one must considerthe effects on the keel cooler fromsandblasting (from the propeller(s) duringbacking maneuvers).

Pumps for Keel Cooler CircuitsOrdinarily, the engine water pump willsatisfactorily circulate the engine jacket waterthrough the keel cooler, if the water lines toand from the cooler are relatively short, ofadequate size, with minimum bends and if thekeel cooler restriction is low. If the totalexternal flow resistance cannot be held withinthe jacket water pump’s capacity, an auxiliaryboost pump will be required.

Need for Corrosion InhibitorA suitable corrosion inhibitor, carefullymaintained, will minimize internal corrosiveeffects. See the section on cooling systemprotection.

30

Light Waterline

Box Coolers

Hull

VentMin. Inside Dia. 70 mm

Cooling WaterInlet or Out

AnodeCathodic Protection

Cooling WaterInlet or Out

Figure 1.21

Venting and Piping of Keel CoolersLocate the cooler and its through-hullconnections so the length of water piping willbe kept to a minimum and the cooler will bewell vented. Extend water piping downwardfrom the engine to the keel cooler, withouthigh points.

It is very difficult to purge trapped air fromthe high points of some keel coolers. The airmust be bled off during initial fill andwhenever the system is completely drained.Vent plugs must be designed into the keelcoolers where they rise toward the bow andstern, and any other high points where airmay be trapped.

Radiator CoolingWith radiator cooling, the hot water from theengine jacket flows to the radiator core whereit is cooled by air being pushed or pulled overthe core fins by a fan. The cooled water isthen pumped back through the engine;circulation is maintained by a gear- orbelt-driven jacket water pump.

When UsedRadiator cooling is used to cool engines thatmust be located well above the vessel waterline or for emergency generator sets thatrequire completely independent supportsystems.

Radiator SizingAs with all cooling systems, radiators areusually sized for a heat rejection load aminimum of 10% greater than the maximumfull load heat rejection rate of the engine. Thisallows for overload conditions and systemdeterioration. This 10% should be added aftera careful calculation has been made of theradiator size required to accommodate themaximum heat rejection rate (under normalfull load operating conditions) at maximumambient air temperature.

Keep in mind that radiators lose capacitywhen operated at altitude or when filled withantifreeze. These conditions should becompensated for and added to the 10%compensation discussed above.

Radiators With Engine-Driven FansSome Caterpillar Engines may be orderedwith engine-driven fans and close-coupledradiators. They are generally available in twosizes for each engine. The smaller designedfor 43°C (110°F) maximum ambient and thelarger for 52°C (125°F) maximum ambienttemperature.

Caterpillar fan drives are designed to preventexcessive crankshaft loading and to resistvibrations.

Fan Drive Outboard BearingsFan drives sometimes require an outboardbearing on the crankshaft pulley. Thesedrives must have a flexible coupling betweenthe pulley and the engine crankshaft. Thiscoupling must not interfere with thelongitudinal thermal growth of the crankshaft.

Fan Power DemandThe fan included in Caterpillar radiatorsystems represents a parasitic load of about4-8% of the gross power output of the engine.

Radiator System PressureCaterpillar radiator cooling systems aredesigned to work under a pressure of27.6-48.3 kPa (4-7 psi) to avoid boiling ofcoolant and allow for best heat transfer.

Remote-Mounted RadiatorsOn installations where it is desirable to locatethe radiator at some distance from theengine—on an upper deck, outdoors or inanother room, a remote radiator can be used.Remote-mounted radiator systems requirespecial attention due to the added restrictionimposed on the cooling water flow byadditional piping. Careful calculations shouldbe made to determine whether a higheroutput pump is necessary.

Height of Remote Radiators AboveEngineNever remote-mount radiators more than10 m (33 ft) above the engine. At greaterheights, the static head may cause leakage atthe engine water pump seals. Consider use ofHotwells in case of need for mountingradiators higher than these guidelines.

31

Radiators Mounted Below EnginesThe radiator top tank loses its air ventingcapability if it’s located below the level of theengine regulator (thermostat) housing.

When a radiator must be mounted lower thanthe engine, the factory-supplied expansiontank must be used.

Connection SizeCoolant connections must be as large as (orlarger than) the applicable engine coolantconnections.

Fan NoiseWhen selecting radiator location, consider fannoise. Noise may be transmitted through theair inlet as well as outlet. As furtherprecaution against noise and vibration, do notrigidly attach ducting to the radiator.

Direction of Prevailing WindsAlso consider the direction of the prevailingwinds so the wind does not act against thefan. Another method is to install an air ductoutside the wall to direct the air outlet (orinlet). Use a large radius bend and turningvanes to prevent turbulence and air flowrestriction.

HotwellHotwell systems are used when static headexceeds 10 m (33 ft) or a boost pump imposesexcessive dynamic head.

A mixing tank accommodates total drainbackof the remote cooling device and connectingpiping. A baffle divides the tank into a hot andcold side but is open sufficiently to assure fullengine flow. Baffles are also used where waterenters the tank to minimize aeration.

If the Hotwell does not have sufficient volume,the pumps will draw in air during operation.The Hotwell tank must be large enough toaccept the full volume of the remote radiatorand the interconnecting piping, plus somereasonable amount to prevent air ingestion bythe pumps. Generally, 110% of the radiatorand piping volume is adequate.

32

Pump

Note: Bottom of tank mustbe more than 0.6m (2 ft)engine water outlet

Sight Glass

ColdSide

Cool WaterFrom Remote

Radiator

Mixing Passage

Hot Waterto Remote RadiatorHot

Side

Figure 1.22

Piping Slope for Effective VentingPiping carrying coolant from the engine to theradiator must have a continual upward slope.This is to allow any gases in the coolant to beseparated from the coolant and vented in theradiator top tank.

RecirculationCare must be taken to ensure engine exhaustgases are not drawing into the radiator.Additionally, the radiators must be arrangedso the hot air discharge of one radiator doesnot recirculate to the inlet of another radiator.Also, for maximum efficiency, the direction ofradiator air flow should not be against thedirection of strong prevailing winds.

When an engine-mounted radiator is used andthe generator set is installed in the center ofthe room, a blower fan can be used and a ductprovided to the outside.

This prevents recirculation and highequipment room temperatures. Some radiatorpackages have, as standard, a radiator ductflange for ease of installation. The duct is asshort and direct as possible; its cross-sectionarea should be as large or larger than theradiator core to minimize backpressure. Theanticipated backpressure for a proposed ductdesign should be less than 12.7 mm (0.5 in) ofwater.

Duct WorkDuct work and adjustable shutters can beused to direct some or all of the warmedradiator air for heating purposes. Support ductwork independently of the engine or radiator.

Static pressure imposed by the duct workmust be determined for each installation.Consult the radiator manufacturer todetermine the permissible static pressure.

The fan shroud must be properly positionedfor optimum air flow. With a blower fan,two-thirds of the fan width should be outsidethe shroud. With a suction fan, two-thirds ofthe fan width should be inside the shroud.

Radiator Air FlowBackpressure or air flow restriction reducesradiator performance. If radiator air flow is tobe ducted, consult the radiator manufacturerregarding the allowable backpressure. Anengine installation in an enclosed spacerequires that the inlet air volume includes thecombustion air requirements of the engineunless the air for the engine is ducted directlyto the engine from the outside.

Expansion TanksFunctionsExpansion tanks perform the followingfunctions:

• Vent gases in the coolant—to reduce corrosion.—to prevent loss of coolant due to

displacement by gases.• Provide a positive head on the system

pump.—to prevent cavitation.

• Provide expansion volume.—to prevent coolant loss when the

coolant expands due to temperaturechange.

• Provide a place to fill the system, monitorits level, and maintain its corrosioninhibiting chemical additives.

33

BlowerFan

Air Duct(To Outside)

Flexible Joint

Figure 1.23

• Provide a place to monitor the systemcoolant level.

—an alarm switch located in theexpansion tank will give early warningof coolant loss.*

Fill RateThe Caterpillar engine-mounted coolingcircuits are designed to completely ventduring the initial fill for fill rates up to 5 gpm(19.0 L/min). Vent lines are located such thatthe external cooling circuit will also be ventedif the customer piping is installed level with,or below, the proper engine connectingpoints, and if no air traps are designed in thepiping.

Type of Expansion TankEngine-Mounted Expansion Tank(Manufactured by Caterpillar)The engine-mounted expansion tank providesall of the above functions for the engine’sjacket water circuit. Caterpillar does notprovide expansion tanks for the enginesauxiliary water circuit (the aftercooler circuit).It can provide adequate expansion volume foronly a modest amount of jacket water. Table1.1 describes the allowable external volumeusing only the engine-mounted expansiontank. Consult TMI for engine coolant capacity.

*In case of a system leak, the water in the auxiliaryexpansion tank must be completely drained before theengine is in danger from coolant loss. Therefore, awater level switch and sight glass will give earlywarning of coolant loss and significantly protect anengine from this problem.

34

Cooling System Volumetric Data

EngineModel

Allowable External Volume With Engine Mounted Tank

Liters U.S. Gal

31163126

3208NA3208T&TA

3304B3306B

3176/963406C3406E3408C3412C3412E35083512351636063608361236163606360836123616

Table 1.1

0.00.07.57.57.57.50.0

38.00.0

53.053.00.0

243.0182.0122.0365.0210.0550.0260.0

4710.04550.04890.04600.0

0.00.02.0

2.02.02.00.0

10.00.0

14.014.00.0

64.048.032.095.055.0

145.065.0

1245.01200.01290.01210.0

Table of Cooling System Volumetric Data

DeaeratorAll the functions of engine mountedexpansion tanks may be fulfilled by a simplevolume chamber, a few feet higher than, andconnected to the jacket water pump, by acontinuously upward-sloping standpipe—allexcept for the need to continuously ventcombustion gas bubbles.

A deaerator is a device to separate gasbubbles from engine coolant in the absence ofa factory-designed, engine-mounted expansiontank.

It is mounted, in series, in the main flow ofjacket water between the engine and its heatexchanger.

A simple volume chamber is still required tohandle coolant expansion and for venting theseparated bubbles to atmosphere.

Engines installed with a simple, volume tankand a deaerator can avoid the use of theengine-mounted expansion tank.

Jacket Water Circuit AuxiliaryExpansion Tank (Fabricated by theEngine Installer)An auxiliary expansion tank is needed whenadditional expansion volume is required in thecooling system. This generally occurs whenkeel coolers are used and may occur whenremote-mounted heat exchangers are used.

35

Figure 1.24

The auxiliary tank can consist of a simpletank. Internal baffles are not required.

The engine-mounted components of thecooling system will adequately separate gasesfrom the coolant. However, the gases, onceseparated, must by allowed to rise by a

continuous upward sloped standpipe to theauxiliary expansion tank. Additional air ventpiping may be required if the auxiliaryexpansion tank is not located directly abovethe engine-mounted expansion tank.

36

6

5

47

8

93

2 10

1

AUXILIARY EXPANSION TANKEngine Jacket Water

1. Engine mounted expansion tank2. Flexible connection3. Connecting pipe4. Auxiliary expansion tank5. Tank vent6. Level gauge

Note: Do not drill engine mounted expansion tank

7. Engine mounted expansion tank 8. Flexible connection 9. Connecting pipe10. Connect lower end of fill vent to vent piping entering rear side of engine mounted expansion tank

Figure 1.25

Aftercooler Circuit AuxiliaryExpansion Tank (Fabricated by theEngine Installer)All closed fresh water aftercooler circuitsrequire an expansion tank. The tank providescoolant expansion volume, allows systemventing and provides a positive pressure onthe inlet side of the circulating pump. Theexpansion tank must be the highest point inthe aftercooler water circuit.

This tank is a simple reservoir with theconnecting pipe placed as close to the pumpinlet as possible. See Auxiliary ExpansionTank Sizing Worksheet to determine theminimum volume required.

Separately support and isolate the auxiliarytank from the pump inlet and cooler byflexible connections. Install a vent line fromthe high point on the engine aftercoolercircuit to a point in the tank below the tank’slow water level. This line must be slopedupwards from the engine to the tank.

All closed separate circuit aftercooler circuitsrequire installation of a vent line. A tappedhole is provided at the high point in theengine-mounted aftercooler circuit. Install avent line from that point to the aftercoolercircuit expansion tank. Vent line size of6.3 mm (0.25 in.) is adequate. The vent lineshould enter the tank below the low waterlevel. If possible, water lines connecting to theaftercooler circuit should be level with orbelow the connecting points on the engine. Ifthe water lines must run above the connectionpoints on the engine, it will be necessary tovent the high points in the external system.Air traps in the external system piping shouldbe avoided.

Sizing the Volume of AuxiliaryExpansion TanksThe minimum volume of the auxiliary tankshould include the total jacket water systemexpansion volume required, plus the volumefor the water to the low water level in thetank. The worksheet on page 38, AuxiliaryExpansion Tank Sizing, can be used todetermine the minimum volume required.

37

5

7

86

4

3

2

9

110 11

1. Return line from cooler 2. Flexible connection 3. Connecting pipe 4. Auxiliary expansion tank 5. Tank vent 6. Level gauge 7. Operating level 8. Cold fill level 9. Vent line from aftercooler10. Connecting line to auxiliary pump inlet11. Auxiliary fresh water pump

AUXILIARY EXPANSION TANKSeparate Circuit Aftercooler—Fresh Water

Figure 1.26

38

Auxiliary Expansion Tank SizingEngine Model __________________________ Rating __________ hp at _______________ rpm

For Engine Jacket Water, Figure 1.25:

Auxiliary jacket water expansion tanks are not always required.

1. Allowable external volume __________ L/gal, with engine mounted tank. (This value shownin Table 1.1, Column A, on page 37.)

2. Total volume of jacket water contained in external cooling circuit (not furnished as part ofengine) __________ L/gal. See Table 1.2, page 47, for volume per length of standard ironpipe.

3. Line 2 minus Line 1 __________ L/gal.If this value is zero or less, additional tank is not required.If this value is greater than zero, an auxiliary tank is required.

4. If required, the minimum volume of the auxiliary expansion tank can be determined by:

a. Engine volume, Table 1.1, Column B ________________________________________b. External volume Line 2 ____________________________________________________c. Total volume—

sum of line a and line b ____________________________________________________d. Multiply line a by 0.06 ____________________________________________________e. Multiply line b by 0.04 ____________________________________________________f. Multiply line c by 0.01 ____________________________________________________g. Total of lines d, e and f ____________________________________________________

(This is the minimum volume of the jacket water auxiliary expansion tank.)

For Separate Circuit Aftercooler, Figure 1.26:

1. Total volume of aftercooler external water __________ L/gal.

2. Multiply Line 1 by 0.02 __________ L/gal.

3. Add the cold fill volume desired in auxiliary expansion tank to Line 2.Total of Line 2 and cold fill volume __________ L/gal.(This is the minimum volume of the aftercooler circuit auxiliary expansion tank.)

Mounting of Auxiliary ExpansionTankSeparately support and isolate the auxiliarytank against vibration from theengine-mounted tank with a flexibleconnector.

Pressurization of SystemsContaining Auxiliary ExpansionTanks—AfterboilGenerally, pressure caps are not required ordesirable on auxiliary expansion tanks. This is

to allow free venting and refilling, whenrequired.

An exception exists in the situation of highperformance craft, such as fast ferrys, yachtsand patrol craft: vessels of this type are proneto have their engines stopped immediatelyafter periods of hard use. In thiscircumstance, a phenomenon known asafterboil can occur.

Afterboil is the boiling (change of liquid tovapor) of the coolant, caused by hot enginecomponents which have lost coolant flow and

pressure when the engine is hastily shut off.This can result in sudden loss of coolant outthe vents and fill openings of the expansiontank. This can be dangerous to personnel inthe area if they are not expecting it.

Afterboil Hazard—How to Avoid ItSystem pressurization with pressure caps onthe auxiliary expansion tanks will minimizeafterboil but cannot completely avoid it. It isstrongly recommended that auxiliaryexpansion tank vents and fill openings bearranged so any hot coolant being dischargedduring afterboil will not present danger topersonnel. Vents should carry the vented hotwater directly into the bilge.

Use of the Burp BottleThis is just like the overflow bottle systemfound on most modern automobiles and forthe same reasons.

After each occurrence of afterboil, the systemwill need to be refilled. This can be avoidedby using a burp bottle. The burp bottle is areservoir for temporary storage of thedischarged coolant. The jacket water circuitauxiliary expansion tank vent leads to thebottom of the burp bottle. As soon as thesteam bubbles condense within the engine,the displaced coolant will be drawn back intothe system by the resultant vacuum. Use ofthe burp bottle requires the jacket watercircuit auxiliary expansion tank be fitted witha double-acting pressure cap*.

Filling of Auxiliary ExpansionTanksAuxiliary expansion tanks in vessels operatedso their engines are not subjected to afterboilshould have permanently installed provisionsto add water from the ship’s portable watersupply plumbing. It should be possible for theoperator to add water to the system byopening and shutting a valve. This is tominimize danger to the operator when addingsystem water during severe sea conditions.

Care should be taken to ensure that thecoolant full level in the tank is above all pipingin order to fill the system.

If it is necessary to design a cooling systemthat will not purge itself of air when beingfilled, provide vent lines from high points tothe expansion tank. These vents should enterthe tank below the normal low water level toprevent aeration of the water which willcirculate through these lines when the engineis running. Slope the vent line upwards withno air traps. The vent line should be 6.3 mm (0.25 in.) tubing. Use of a smaller size willclog and may not provide adequate ventingability. Too large a vent tube may introduce acircuit that could contribute either tosubcooling or overheating, depending on thelocation.

If at all possible, avoid external piping designsthat require additional vent lines.

Cooling SystemProtective DevicesA most common problem associated withproperly installed cooling systems is loss ofcoolant, generally due to breaking a waterhose and overheating, which can have manycauses. As with many engine safety devices,the decision to automatically shut down theengine without warning, or to continueoperation risking total engine destruction, isfor the careful consideration of the owner. Inconditions where the entire boat and the livesof those on board are at stake, it may beappropriate to use a safety system which doesnot have automatic shutdown capability. Theboat’s pilot has the option to continueoperation of a distressed engine to provide afew more minutes of engine power to escape amore present danger.

* A double-acting pressure cap is one which will hold acertain pressure or vacuum.

39

Coolant Level SwitchesCoolant level switches are devices which cangive early warning of coolant loss. Theygenerally consist of a sealed single pole-double throw switch, actuated by a float whichrides on the surface of the coolant in theexpansion tank. It is good design practice tolocate the coolant level switch in the highestpart of the cooling system—to give earliestwarning of a drop in coolant level. High watertemperature switches will not give warning ofcoolant loss; their temperature sensingportion works best when surrounded by liquidwater rather than steam.

High Water TemperatureSwitchesHigh water temperature switches are deviceswhich continuously monitor the temperatureof some fluid, generally coolant, and actuateswitch contacts when the fluid temperaturegoes above some preset limit. In the case ofjacket water coolant, the set point is usuallybetween 96° and 102°C (205° and 215°F),depending on the engine, cooling systemtype, and whether alarm of impendingproblems or actuation of engine shutdownsystems is desired. Switches can be set foreither condition.

Emergency SystemsThe worldwide marine classification societiesrequire in certain applications that, forunrestricted seagoing service, engines beequipped with a separate emergency supply ofcooling water flow. The requirement appliesto both the engine jacket water and auxiliary(sea or fresh) water systems. The purpose ofthe emergency systems is to ensure cooling ifeither the jacket water or auxiliary (sea orfresh) water pump should fail. Thecustomer-supplied emergency pumps shouldprovide flow equal to the failed pump topermit operation at full, continuous powerwith the emergency systems. For pump flowrequirements of engine-mounted pumps, referto Technical Marketing Information (TMI) orconsult the Caterpillar Dealer. If reducedpower operation is acceptable, reduced flowscan be utilized. Use flexible connectors at theengine to protect the piping and engine.

Jacket Water Pump ConnectionsThe optional Caterpillar emergency jacketwater connections (available for the large Veeengines) meet the requirements of the engineand the marine classification societies. Use ofthese connections permits the emergencysystem to utilize the normal jacket water asthe coolant and to bypass the engine-mountedjacket water pump. The system includes ablanking plate or valve to direct jacket waterto the emergency system and flangedconnection points on the engine for theemergency system piping. Figure 1.27 is aschematic diagram of the system properlyconnected. The customer-supplied emergencywater pump should provide flow equal to thefailed pump.

The use of seawater in the engine jacket watersystem is not recommended. If seawater mustbe used in the jacket water system to ensurethe safety of the ship in an emergencysituation, use the lowest engine power levelcommensurate with the sea state. Onreaching port, the jacket water system mustbe thoroughly flushed and cleaned.

Auxiliary Seawater PumpConnectionsAll emergency seawater cooling connectionsare to be provided by the installer andconnected as indicated in the figureillustrating emergency auxiliary pumpconnections. The emergency seawater pumpshould provide flow equal to the failed pump.

Auxiliary Freshwater PumpConnectionsAll emergency connections for separate keelcooled aftercooler circuits are to be providedby the installer, and connected as indicated inthe figure illustrating emergency auxiliarypump connections. The flow required for theemergency separate keel cooled aftercoolerpump should equal the failed pump. The useof seawater in the separate keel cooledaftercooler circuit is not recommended. Theengine- mounted pump and lines are offerrous material and have low corrosionresistance in seawater. If seawater must beused in an emergency to ensure the safety ofthe ship, thoroughly flush the system as

40

41

2

3

1

4

5

6

EMERGENCY AUXILIARY PUMP CONNECTIONS

1. Engine mounted auxiliary pump 4. Customer provided valve2. Customer provided emergency (normally open)

auxiliary pump 5. Auxiliary cooling circuit3. Customer provided valve 6. Flexible connection

(normally closed)

Figure 1.28

1

6

623

4

5

EMERGENCY JACKET WATER PUMP CONNECTIONS(Location of Jacket Water Pump May Vary)

1. Flanged tee connection — to emergency pump2. Blanking plate — closed for emergency pump operation3. Flanged tee connection — from emergency pump

4. Valve — customer supplied (open for emergency pump operation)5. Emergency pump — customer supplied 6. Flexible connector — customer supplied

Figure 1.27

mentioned in the jacket water section, andinspect the parts for corrosion damage anddeposits.

Central Cooling SystemsA central cooling system is defined as onewhich cools multiple engines and whichcombines many individual systemcomponents (heat exchangers and pumps)into large central ones. There are economicadvantages to such systems.

Advantages of a Central CoolingSystemThere are fewer lines to install, significantlyreducing the amount of shipyard laborrequired to install such a system.

The smaller number of components cost lessto procure, inventory, and support with repairunits.

Larger components are generally more robustand can be expected to last longer.

Disadvantages of a CentralCooling SystemIt is very difficult to diagnose problems insuch a system because there are so manymodes of operation possible:

For example: with a system containing threeengines, one heat exchanger, and two pumps,there will be 162 possible combinations ormodes of operation.

Following is a list of common errors indesigning such systems:

Flow ControlThere are upper and lower limits to theallowable flow through an engine. The systemmust be able to throttle the flow through eachengine independently.

Temperature ControlThe heat exchanger must be capable ofdelivering the proper amount of cooling,proportional to engine load.

Load ControlThe amount of external water flow through aCaterpillar Engine is directly proportional tothe engine’s load. The greater the load, thegreater the amount of cooling required andthe more water the engine’s internal coolingcircuitry will discharge for cooling. At lightloads, the engine’s temperature controls willbypass the external portion of the enginecooling system, recirculating virtually all ofthe coolant. If the water pressure presented toan engine by a central cooling system is toohigh, the proper operation of the engine’stemperature controls may be overridden, andthe engine will suffer over or under coolingproblems. It is very difficult to adequatelybalance and control the flow through severalengines, all of which might be operating atwidely varying loads.

The water pressure on an engine jacket waterinlet cannot be allowed to exceed 172 kPa (25 psi). Economic factors encourage manydesigners to use higher pressures. Do not usehigher pressures. Higher pressures willsignificantly reduce water pump seal life.

42

Running Engine Load Maintenance Condition Redundancy Required for Reliability

Yes High Operational shutdown for maintenance but still connectedto the system

In the heat exchanger

No Intermediate In the interconnecting plumbing*

Overhaul in process, disconnectedfrom the system

Low In the pump(s) and their controls/switchgear

* In areas of severe marine growth problems, it is a good idea to have two parallel sets of plumbing so that one set can be in process of being cleaned at any given time.

Suggestions for Design of aSuccessful Central CoolingSystemKeep each engine’s jacket water systemindependent of all others. The load controlproblems are not economically solvable.

Use a separate heat exchanger at each enginefor cooling of the engine jacket water.

Provide a ring main of freshwater, circulatedby at least two, parallel water pumps. A thirdwater pump should be kept in reserve tomaintain operation when either of the otherpumps require maintenance. Each pumpshould be identical for ease of parts inventoryand maintenance. The ring main is the watersource for each engine’s independent coolingsystem. The temperature and pressure of thewater in the ring main do not need precisecontrol. Each engine should have anengine-driven, auxiliary (not jacket water)water pump. This pump will draw water fromthe ring main and return it back to the ringmain, downstream.

System Pressure DropThe total external system resistance to flowmust be limited in order to ensure adequateflow. The resistance to flow is determined bythe size and quantity of pipe, fittings andother components in the portion of thecooling system which is external to theengine. As the resistance (pressure drop)increases, the engine-driven water pump flowdecreases.

The external resistance imposed on the pump(also called external head) includes both theresistance ahead of the pump inlet and theresistance downstream of the engine. Theresistance to flow in the external circuit of aclosed circulating system consists only of thefrictional pressure drop. The resistance toflow in an external open cooling circuitconsists of not only the frictional pressuredrop but also the height of suction lift on thepump inlet and the heights of the lift on theengine outlet.

Curves showing water flow versus totalexternal system head for engine-driven pumpsare available. The value for the maximumexternal resistance must not be exceeded inthe cooling circuit added by the customer inorder to maintain minimum water flow. Flowslower than the minimums will certainlyshorten the life of the engine.

When designing the engine cooling systems,pressure drop (resistance) in the externalcooling system can be calculated by totalingthe pressure drop in each of the system’scomponents. The section of useful tables todesigners of cooling systems can be used todetermine the pressure drop through pipe,fittings and valves. Suppliers of othercomponents, such as strainers and sea cocks,can provide the data required for theirproduct.

It is always necessary to evaluate the designand installation of the cooling circuits bytesting the operation and effectiveness of thecompleted system to ensure properperformance and life.

CorrosionGalvanic Corrosion in SeawaterWhen two dissimilar metals are electricallyconnected and both submerged in saltwater,they form a battery and an electrochemicalreaction takes place. In this process, onemetal is eaten away. The rate of deteriorationis proportional to a number of factors:

• The differential potential between the twometals on the electrochemical series (seeUseful Tables to Designers of CoolingSystems).

• The relative areas of the two metals: Ifthere is a small area of the more noblemetal relative to the less noble metal, thedeterioration will be slow and relativelyminor. If there is a large area of the morenoble metal such as copper sheathing on awooden hull, and a much smaller area ofthe less noble metal, such as iron nailsholding the copper sheathing to the wood,the wasting away of the iron nails will beviolent and rapid.

43

Dissimilar Metal Combinations toAvoid• Bronze Propeller on Steel Shaft• Mill Scale on Hull Plate (Internal or

External)• Aluminum Fairwaters Fastened to a Steel

Hull• Steel Bolts in Bronze Plates• Bronze Unions and Elbows Used With

Galvanized Pipe• Bronze Sea Cocks on Iron Drain Pipes• Brass Bilge Pumps on Boats With Steel

Frames• Brass, Bronze, or Copper Fasteners in Steel

Frames • Stainless Steel Pennants on Steel Mooring

Chains • Bronze or Brass Rudder Posts With Steel

Rudders• Bronze Rudders With Steel Stopper-Chains• Steel Skegs (Rudder Shoes) Fastened With

Bronze or Brass Leg Screws• Steel and Brass Parts in the Same Pump

Rule of Thumb:Do not put iron or steel close to or connectedwith alloys of copper under salt water.

The Protective Role of ZincIf alloys of copper (bronze, brass), iron(steel), and zinc are all connected togetherand submerged in salt water, the zinc will beeaten away, protecting the iron (steel). It isnecessary to have a metallic electricalconnection to the metals to be protected. Thisis usually easy to accomplish on a steel hull. Itis more difficult on a fiberglass hull, sincespecial electrical connection may be requiredunless the zincs are connected directly to oneof the metals, preferably the copper alloy.

The Zinc Must Never Be Painted! Whenelectrical contact is made through thefastening studs, it’s desirable to putgalvanized or brass bushings in the holes inthe zincs so that contact will be maintained asthe zincs corrode.

Zincs should be periodically inspected. Asthey work, a white, crust-like deposit of zincoxides and salts form on the surface. This isnormal. If it does not form and the zincsremain clean and like new, they are notprotecting the structure.

44

Nominal Size Actual I.D. Actual O.D.

in. mm in. mm in. mm ft/gal m/L ft/cu ft m/cu m

.125 3.18 .270 6.86 .405 10.29 336.000 27.000 2513.000 27.049

.250 6.35 .364 9.25 .540 13.72 185.000 16.100 1383.000 14.886

.375 9.53 .494 12.55 .675 17.15 100.400 8.300 751.000 8.083

.500 12.70 .623 15.82 .840 21.34 63.100 5.000 472.000 5.080

.750 19.05 .824 20.93 1.050 26.68 36.100 2.900 271.000 2.9171.000 25.40 1.048 26.62 1.315 33.40 22.300 1.900 166.800 1.7951.250 31.75 1.380 35.05 1.660 42.16 12.850 1.030 96.100 1.0341.500 38.10 1.610 40.89 1.900 48.26 9.440 .760 70.600 760.0002.000 50.80 2.067 52.25 2.375 60.33 5.730 .460 42.900 462.0002.500 63.50 2.468 62.69 2.875 73.02 4.020 .320 30.100 324.0003.000 76.20 3.067 77.90 3.500 88.90 2.600 .210 19.500 210.0003.500 88.90 3.548 90.12 4.000 101.60 1.940 .160 14.510 156.0004.000 101.60 4.026 102.26 4.500 114.30 1.510 .120 11.300 122.0004.500 114.30 4.508 114.50 5.000 127.00 1.205 .097 9.010 97.0005.000 127.00 5.045 128.14 5.563 141.30 .961 .077 7.190 77.0006.000 152.40 6.065 154.00 6.625 168.28 .666 .054 4.980 54.0007.000 177.80 7.023 178.38 7.625 193.66 .496 .040 3.710 40.0008.000 203.20 7.982 202.74 8.625 219.08 .384 .031 2.870 31.0009.000 228.60 8.937 227.00 9.625 244.48 .307 .025 2.300 25.000

10.000 254.00 10.019 254.50 10.750 273.05 .244 .020 1.825 19.60012.000 304.80 12.000 304.80 12.750 323.85 .204 .160 1.526 16.400

Table 1.2

Useful Tables to Designers of Cooling SystemsPipe Dimensions — Standard Iron Pipe

If the zincs are not working, look for thefollowing conditions:

• The anode is not electrically bonded to thestructure.

• The paint on the structure is still in nearperfect condition.

45

VELOCITY vs FLOWStandard Pipe Sizes 1.5 to 5 in.

(38.1 to 127mm)

2 4 6 8 10 12 14 16 18 20 22 24 26 28 L/s

Flow

m/s fps

3.5

2.5

1.5

3

2

1

.5

Vel

oci

ty

(89 mm)3.50 in.

(76.2 mm)3.00 in.

(63.5 mm)2.50 in.

(50.8 mm)2.00 in.

(38.1 mm)1.50 in.

4.00 in. (102 mm)

4.50 in. (114 mm)

5.00 in. (127 mm)

0 50 100 150 200 250 300 350 400 450 gpm

12

10

8

6

4

2

Figure 1.29

Velocity Versus Flow (Standard Pipe Sizes)

VELOCITY vs FLOWTube Sizes From 1 in. to 5 in. O.D. (25.4 mm to 127 mm)

(Common Usage Wall Thickness)

Flow

Vel

oci

ty

(31.8 mm)1.25

(41.8 mm)1.75

(53.3 mm)2.12

(60 mm)2.38

m/s fps

.5

1

2

3

1.5

2.5

3.5

282624222018161412108642

0 50 100 150 200 250 300 350 400 450

L/s

gpm

Nom. Tube Size .065 in. (1.65 mm) Wall

V = =.321 QA

———.408 Q

ID2——— For Other WallThicknesses

V = Vel (fps)Q = Flow (gpm)A = In2 (ID)ID = Inside Dia.

5.00 in. (127 mm)

4.75 in. (121 mm)

4.75 in. (121 mm)

4.00 in. (102 mm)12

10

8

6

4

2

(25.4 mm) 1.00

(38.1 mm) 1.50

(50.5 mm) 2.00

(57 mm)2.25

(63.5 mm) 2.50

(70 mm)2.75

(83 mm) 3.25

(89 mm) 3.50

(95.3 mm) 2.75

Figure 1.30

46

gpm (L/s) .75 in. (19.05 mm) 1 in. (25.4 mm) 1.25 in. (31.75 mm) 1.5 in. (38.1 mm) 2 in. (50.8 mm) 2.5 in. (63.5 mm) gpm (L/s)5 .34 10.50 3.25 .84 .40 .16 .05 5 .34

10 .63 38.00 11.70 3.05 1.43 .50 .17 .07 10 .6315 .95 80.00 25.00 6.50 3.05 1.07 .37 .15 15 .9520 1.26 136.00 42.00 11.10 5.20 1.82 .61 .25 20 1.2625 1.58 4 in. (101.6 mm) 64.00 16.60 7.85 2.73 .92 .38 25 1.5830 1.9 .13 89.00 23.00 11.00 3.84 1.29 .54 30 1.9035 2.21 .17 119.00 31.20 14.70 5.10 1.72 .71 35 2.2140 2.52 .22 152.00 40.00 18.80 6.60 2.20 .91 40 2.5245 2.84 .28 5 in. (127 mm) 50.00 23.20 8.20 2.76 1.16 45 2.8450 3.15 .34 .11 60.00 28.40 9.90 3.32 1.38 50 3.1560 3.79 .47 .16 85.00 39.60 13.90 4.65 1.92 60 3.7970 4.42 .63 .21 113.00 53.00 18.40 6.20 2.57 70 4.4275 4.73 .72 .24 129.00 60.00 20.90 7.05 2.93 75 4.7380 5.05 .81 .27 145.00 68.00 23.70 7.90 3.28 80 5.0590 5.68 1.00 .34 6 in. (152.4 mm) 84.00 29.40 9.80 4.08 90 5.68

100 6.31 1.22 .41 .17 102.00 35.80 12.00 4.96 100 6.31125 7.89 1.85 .63 .26 7 in. (177.8 mm) 54.00 17.60 7.55 125 7.89150 9.46 2.60 .87 .36 .17 76.00 25.70 10.50 150 9.46175 11.05 3.44 1.16 .48 .22 8 in. (203.2 mm) 34.00 14.10 175 11.05200 12.62 4.40 1.48 .61 .28 .15 43.10 17.80 200 12.62225 14.20 5.45 1.85 .77 .35 .19 54.30 22.30 225 14.20250 15.77 6.70 2.25 .94 .43 .24 65.50 27.10 250 15.77275 17.35 7.95 2.70 1.10 .51 .27 9 in. (228.6 mm) 32.30 275 17.35300 18.93 9.30 3.14 1.30 .60 .32 .18 38.00 300 18.93325 20.50 10.80 3.65 1.51 .68 .37 .21 44.10 325 20.50350 22.08 12.40 4.19 1.70 .77 .43 .24 50.50 350 22.08375 23.66 14.20 4.80 1.95 .89 .48 .28 10 in. (254 mm) 375 23.66400 25.24 16.00 5.40 2.20 1.01 .55 .31 .19 400 25.24425 26.81 17.90 6.10 2.47 1.14 .61 .35 .21 425 26.81450 28.39 19.80 6.70 2.74 1.26 .68 .38 .23 450 28.39475 29.97 7.40 2.82 1.46 .75 .42 .26 475 29.97500 31.55 8.10 2.90 1.54 .82 .46 .28 500 31.55750 47.32 7.09 3.23 1.76 .98 .59 750 47.32

1000 63.09 12.00 5.59 2.97 1.67 1.23 1000 63.091250 78.86 8.39 4.48 2.55 1.51 1250 78.861500 94.64 11.70 6.24 3.52 2.13 1500 94.641750 110.41 7.45 4.70 2.80 1750 110.412000 126.18 10.71 6.02 3.59 2000 126.18

Table 1.3

Flow Head Loss in ft/100ft (m/100m) Flow

3 in. (76.2 mm)

Typical Friction Losses of Water in Pipe — (Old Pipe)

47

Resistance of Valves andFittings to Flow of FluidsExample: The dotted line shows thatthe resistance of a 6-inch Standard Elbowis equivalent to approximately 16 feet of6-inch Standard Pipe.

Note: For sudden enlargements orsudden contractions, use the smallerdiameter, d, on the pipe size scale.

Conversion Chart

Long Sweep Elbow orrun of Standard Tee

Medium Sweep Elbow orrun of Tee reduced 1/4

Standard Elbow or run ofTee reduced 1/2

Standard TeeThrough Side Outlet

Close Return Bend

450 Elbow

Angle Valve, Open

Globe Valve, OpenGate Valve

3/4 Closed

1/2 Closed

1/4 Closed

Fully Open

Standard Tee

Square Elbow

Borda Entrance

d

d

D

D

Sudden Enlargement

Sudden Contraction

d/D-1/4d/D-1/2d/D-3/4

d/D-1/4d/D-1/2d/D-3/4

Ordinary Entrance &Swing Check Valves

Insi

de

Dia

met

er, I

nch

es

0 100 200 300 400 500 ft

0 20 40 60 80 100 120 140 160 180 200 220 240

1 2 3 4 5 6 7 8 9 10 in

mm

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150m

50

30

20

10

5

3

2

1

0.5

1/2

3/4

1-1/4

1-1/2

2-1/2

3-1/2

4-1/2

1

2

4

3

5

7

9

12

16

20

24

36

48

10

8

18

22

30

42

0.1

0.2

0.3

0.5

1

1

2

3

5

10

20

30

50

100

200

300

500

1000

2000

3000

6

Eq

uiv

alen

t L

eng

th o

f S

trai

gh

t P

ipe,

Fee

t

No

min

al D

iam

eter

of

Sta

nd

ard

Pip

e, In

ches

Electrochemical SeriesCorroded End — Least Noble

MagnesiumMagnesium AlloysZincBeryllimAluminum AlloysCadmiumMild Steel or IronCast IronLow Alloy SteelAustanitic Cast IronAluminum BronzeNaval BrassYellow BrassRed Brass18-8 Stainless Steel (Active)18-8-3 Stainless Steel (Active)Lead-Tin SoldersLead70-30 Copper NickelTinBrassesCopperBronzesCopper-Nickel AlloysMonelAdmiralty Brass, Aluminum BrassManganese BronzeSilicon BronzeTin BronzeSilver SolderNickel (Passive)Chromium-Iron (Passive)18-8 Stainless Steel (Passive)18-8-3 Stainless Steel (Passive)SilverNi-Cr-Mo Alloy 8TitaniumNi-Cr-Mo Alloy CGoldPlatinumGraphite

Protected End — Most Noble

Corrosion Rates of VariousMetals in SeawaterRepresentative Corrosion Rates inSeawater

48

Corrosion Ratein Quiet Seawater*

mm/yrMetal

.02 to 1.20 .02 to .25> .02 to .38 .10 to .25 0.00 to .07 0.00 to .12 .01 to .38 0.00 to .02

NilNilNil

AluminumZincLeadIron (Steel)Silicon IronStainless Steel**Copper AlloysNickel AlloysTitaniumSilverPlatinum

* Rates are ranges for general loss in seawater at ambient temperatures and velocities no greater than 1 m (3 ft) per second. Pitting penetration is not considered.

** Many stainless steels exhibit high rates of pitting in stagnant seawater.


● Ventilation

● Exhaust System


VentilationGeneral InformationVentilation AirCombustion AirSizing of Combined Combustion and Ventilation AirDucts — Rule of ThumbCrankcase Fumes DisposalSpecial Ventilation Considerations

General InformationThere are three aspects to ventilation:

Ventilation AirThe flow of air required to carry away theradiated heat of the engine(s) and otherengine room machinery.

Combustion AirThe flow of air required to burn the fuel in theengine (propulsion and auxiliaries).

Crankcase Fumes DisposalThe crankcase fumes of the engine must beeither ingested by the engine or piped out ofthe engine room.

Ventilation AirEngine room ventilation has two basicpurposes:

• To provide an environment which permitsthe machinery and equipment to functiondependably.

• To provide a comfortable environment forpersonnel.

Radiated heat from the engines and othermachinery in the engine room is absorbed byengine room surfaces. Some of the heat istransferred to atmosphere or the sea throughthe hull. The remaining radiated heat must becarried away by the ventilating system.

A system for discharging ventilation airfrom the engine room must be includedin the construction of the vessel. Do notexpect the engine(s) to carry all theheated ventilation air from the engineroom by way of the exhaust piping.

RoutingCorrect Ventilation Air Routing isVitalComfortable air temperatures in the engineroom are impossible without proper routing ofthe ventilation air.

Fresh air should enter the engine room as farfrom the sources of heat as practical and aslow as possible. Since heat causes air to rise, itshould be discharged from the highest pointin the engine room, preferably directly overthe engine. Avoid incoming ventilation airducts which blow cool air toward hot enginecomponents. This mixes the hottest air in theengine room with incoming cool air, raisingthe temperature of all the air in the engineroom.

Relative Efficiency of Various Routingof Ventilation AirThe sketches on page 2 illustrate the relativeefficiency of various ventilation routing:

1

Where: Frouting is a factor which relates therelative efficiency of various ventilation airrouting.

Example:If the routing in Figure A (upper left) is usedas a base to which the others are compared:

• 1.4 times more air is required (duct cross-sectional area and fan capacity) toadequately ventilate the machinery spaceillustrated in Figure B (upper right).

• It takes twice as much air (duct cross-sectional area and fan capacity) toadequately ventilate the machinery spaceillustrated in Figure C (lower right).

• 3.3 times more air is required (duct cross-sectional area and fan capacity) toadequately ventilate the machinery spaceillustrated in Figure D (lower left).

Engine Room TemperatureA properly designed engine room ventilationsystem will maintain engine room airtemperatures within 9°C (15°F) above theambient air temperature (ambient airtemperature refers to the air temperaturesurrounding the vessel). Maximum engineroom temperature should not exceed 49°C(120°F).

Quantity RequiredIn general, changing the air in the engineroom every one or two minutes will beadequate, if flow routing is proper.

Provisions should be made by the installer toprovide incoming ventilation air of0.1 – 0.2 m3/min (4-8 cfm) per installedhorsepower (both propulsion and auxiliaryengines). This does not include combustionair for the engines. (See following remarks onengine combustion air, page 7.)

Engine exhaust ventilation air should be 110to 120% of the incoming ventilation air. Theexcess exhaust ventilation air accomplishestwo things:

• It compensates for the thermal expansionof incoming air.

• It creates an in draft to confine heat andodor to the engine room.

Operation in extreme cold weather mayrequire reducing ventilation air flow to avoiduncomfortably cold working conditions in theengine room. This is easily done by providingventilation fans with two speed motors (100%and 50 or 67% speeds).

2

Figure D (Good) Frouting = 2.0

Figure A (Superior)

Figure C (Poor) Frouting = 3.33

Figure B (Better) Frouting = 1.4

Figure 1.1

Frouting = 1.0

3

Through-Hull Opening DesignThere must be openings for air to enter theengine room and openings for air to leave theengine room.

There should be an inlet for cool air to enter,and a discharge for hot air to leave, on eachside of the hull. If it is impractical to have twoseparate openings per side, then avoid havinghot discharged air mix with cool air enteringthe engine room.

Design FeaturesSizeSize the openings (A) to keep the air velocity (in the openings) below 610 m/min (2,000 ft/min).

Air Entering the Engine RoomThe engine room must have openings for airto enter. The air may also enter from theaccommodation spaces (staterooms, galley,salon, companionways, pilot house, etc.)* ordirectly through the hull or deck. Engineroom air inlets through accommodationspaces can be troublesome.

If air is to enter the engine room from theaccommodation spaces (staterooms, galley,salon, companionways, pilot house, etc.),good design practice will include sounddeadening treatments for the opening(s)which conduct air from the accommodationspaces to the engine room.

*Heating and/or air conditioning of accommodationspacecs will be made much more complicated if theengines must rely on that heated/cooled air forcombustion. Engine room air inlets throughaccommodation spaces simplify the task of ensuring theengine room inlet air is kept clean and free from rain orspray.

Deck

A Minimum

InvertedTroughon 3 sides

Lift300 mm Min. A

A

Features of Through-Hull Ventilation Openings

Wir

e M

esh

Lo

w R

estr

icti

on

Dec

ora

tive

Gri

ll

Figure 1.2

Air Leaving the Engine RoomThe through-hull or through-deck openingsfor discharge of heated ventilation air shouldbe located aft of and higher than all intakeopenings to minimize recirculation.

• The intake air opening should be locatedforward of — and, if convenient — at alower elevation, than . . .

• The ventilation air opening, dischargingheated ventilation air, which should belocated aft of — and at a higher elevationthan the intake air opening — to minimizerecirculation. Cross- and following-windsmake total elimination of ventilation airrecirculation impossible.

FansIn modern installations, natural draftventilation is too bulky for practicalconsideration. Adequate quantities of fresh airare best supplied by powered (fan-assisted)systems.

LocationFans are most effective when they withdrawventilation air from the engine room (suctionfans) and discharge the hot air to theatmosphere.

TypeVentilating air fans may be of the axial flowtype (propeller fans) or the centrifugal type(squirrel cage blowers). When mounting fansin ventilating air discharge ducts (mosteffective location), the fan motors should beoutside the direct flow of hot ventilating airfor longest motor life. The design ofcentrifugal fans (squirrel cage blowers) isideal.

SizingThe name plate ratings of fans do notnecessarily reflect their as-installedconditions. Just because a fan’s name platesays it will move 1000 cfm of air does notmean it will move 1000 cfm through an engineroom which has severely restricted inletand/or outlet openings. Fans are often ratedunder conditions which do not reflectas-installed flow restrictions. In general, theas-installed conditions will be more severethan the fans name plate rating conditions.

Combustion AirQuantity RequiredA diesel engine requires approximately0.1 m3 of air/min/brake kW(2.5 ft3 of air/min/bhp) produced.

Combustion Air DuctsDesign combustion air ducts to have aminimum flow restriction.

Very large amounts of air flow through thecombustion air ducts.

Air CleanersEngines must be protected from ingestingforeign material. The engine-mounted air filterelements must never be remote-mounted,without factory approval.

If large amounts of sea spray, dust, or insectsare expected, external, remote-mounted,precleaners may be installed at the inlet to aduct system to extend the life of theengine-mounted filter elements.

Air Cleaner Service IndicatorsAir cleaner service indicators signal the needto change air filter elements when arestriction of 7.47 kPa (30 in.) of water —measured while the engine is producing fullrated-power — develops. This allows anacceptable operating period before air filterservice or replacement is required.

Duct RestrictionTotal duct air flow restriction, including aircleaners, should not exceed 2.49 kPa (10 in.)of water measured while the engine isproducing full rated power. It is good designpractice to design combustion air ducts togive the lowest practical restriction to air flow,since this will result in longer times betweenfilter element service or replacement.

Velocity of Air in Combustion AirDuctsCombustion air duct velocity should notexceed 610 m/min (2,000 ft/min). Highervelocities will cause unacceptable noise levelsand excessive flow restriction.

4

Water TrapsTraps should be included to eliminate anyrain or spray from the combustion air. Rainand spray can cause very rapid plugging ofthe paper air filter elements on someCaterpillar Engines. This will reduce the flowof air through the engine, raising the exhausttemperature with potentially damaging effects.

TemperatureA well designed engine room ventilationsystem will provide engines with air whosetemperature is not higher than 8.5°C (15°F)above the ambient temperature though

derating of Caterpillar Marine engines is notrequired so long as combustion airtemperatures remain below 49°C (120°F).

Rain and SprayThe combustion air should be free of liquidwater, though water vapor — humidity — isacceptable.

5

Forward

3D

2D

D

D

2 D/3

D/3

Equip combustion air inlet with a cap toprevent drawing in rain or spray.

Avoid crankcase fumes, exhaust gases, rain,or sea spray entering the engines combustionair inlet. Air cleaner service life will be greatlyshortened. In severe cases, engine failuremay result.

Discharge crankcase fumes and exhaust gaseshigher than combustion air inlet.

Figure 1.3

Sizing of CombinedCombustion andVentilation Air Ducts— Rule of ThumbAir Must Be Allowed to Enterthe Engine Room Freely.A useful rule of thumb is:

• Use 4-6 sq cm of duct cross-section areaper engine kW and no more than three (3)right angle bends. A larger area allowsmore air flow into the engine room.

• Use 0.5-0.75 sq in. of duct cross-sectionarea per engine horsepower and no morethan three (3) right angle bends. A largerarea allows more air flow into the engineroom.

If more right angle bends are required,increase the pipe diameter by one pipe size.

Crankcase FumesDisposal

Normal combustion pressures of an internalcombustion engine cause a certain amount ofblowby past the piston rings into the

crankcase. To prevent pressure buildupwithin the crankcase, vent tubes are providedto allow the gas to escape. 3100 and 3208 andhigh performance 3176, 3406, 3408, and 3412marine engines consume their crankcasefumes, by drawing the fumes into the engine’sair intake system. Larger Caterpillar marineengines must have their crankcase fumespiped away from the engine to prevent thefumes from plugging their high-efficiencypaper air filter elements.

Pipe SizingGenerally use pipe of the same size as thecrankcase fumes vent on the engine. If thepipe run is longer than approximately 3 m(10 ft) or if there are more than three (3)90° elbows, increase the pipe inside diameterby one pipe size.

Common Crankcase Vent PipingSystemsA separate vent line for each engine isrequired. Do not combine the piping formultiple engines.

Location of Crankcase VentTerminationCrankcase fumes must not be discharged intoair ventilating ducts or exhaust pipes. Theywill become coated with oily deposits.

6

40 mm/m (.5 in./ft)Downward SlopeFrom Engine

25 mm (1in.) Maximum

Vent to Atmosphere(Locate Higher Than Engine

Combustion or VentilationAir Inlet)

Engine Mounted CrankcaseBreather

Rubber Hose FlexibleFitting

Condensed Combustion Products(May Be Initially Filled With Oil or Water)

Figure 1.4

The crankcase vent pipe may be directed intothe exhaust gas flow at the termination of theexhaust pipe.

Preferably, the crankcase vent pipe will ventdirectly to the atmosphere. The vent pipetermination should be directed to preventrain/spray entering the engine.

Condensation/Rainwater inCrankcase Fumes PipingLoops or low spots in a crankcase vent pipecan collect rainwater and/or condensedcombustion products. These liquids may betrapped in a drip collector and drained tominimize the amount of oily dischargethrough the vent pipe and prevent restrictionof normal discharge of fumes.

Required Slope of CrankcaseFumes Disposal PipingAvoid horizontal runs in crankcase ventpiping. Install the vent pipe with a minimumslope of 40 mm/m (.5 in./ft).

Maximum Pressure in theEngine Oil SumpUnder no circumstances should crankcasepressure vary more than 25.4 mm (1 in.) ofwater from ambient barometric pressurewhen the engine is new*. Higher crankcasepressures will cause oil leaks. A poweredcrankcase fumes disposal system shouldcreate no more than 25.4 mm (1 in.) of watervacuum in the crankcase.

Crankcase VolumesThe volume of an engine’s crankcase isrequired for the sizing of crankcase pressurerelief valves. See the following table.

Many marine classification societies (MCS)expect crankcase pressure relief valves to beinstalled on engines with crankcase volumesmore than 0.61 m3 (21.5 ft3) or cylinder boresover 200 mm (7.89 in.) in diameter. Caterpillaroffers crankcase pressure relief valves onengines larger than the 3408.

* As the engine approaches its overhaul interval, blowby(one of the causes of crankcase pressure) will tend toincrease. Careful monitoring of crankcase pressure willprovide valuable guidance on the condition of anengine’s valve guides and piston rings.

7

Crankcase VolumeModelCrankcase Volumes

3116 .045 m3 (1.59 ft3)3126 .045 m3 (1.59 ft3)3176 .14 m3 (4.9 ft3)3304B .05 m3 (1.76 ft3)3306B .063 m3 (2.22 ft3)3208 .0011 m3 (.039 ft3)3406B .25 m3 (8.8 ft3)3408B .3 m3 (10.5 ft3)3412 .4 m3 (14.1 ft3)D399 1.28 m3 (45.2 ft3)D398 .96 m3 (33.9 ft3)D379 .64 m3 (22.6 ft3)3508 .65 m3 (22.9 ft3)3512 .98 m3 (34.6 ft3)3516 1.41 m3 (49.8 ft3)3606 2.3 m3 (81.2 ft3)3608 3.06 m3 (108 ft3)3612 3.12 m3 (110.2 ft3)3616 4.08 m3 (144 ft3)

Special VentilationConsiderationsRefrigeration EquipmentPrevent refrigerant leakage into theengine’s air intake system. Freon orammonia will cause severe enginedamage if drawn into the engine’scombustion chambers. The chemicals inrefrigerants become highly corrosiveacids in the engine’s combustionchambers.

If refrigeration equipment is installed withinthe same compartment as a diesel engine, thediesel engine must take its combustion airfrom a shipyard-supplied ductwork systemwhich carries air to the engine from an areafree of refrigerant fumes.

Exhaust Pipe InsulationRecommendedLong runs of hot, uninsulated exhaust pipingwill dissipate more heat into the engine roomthan all the machinery surfaces combined.Completely insulate all exhaust piping withinthe engine room area. All hot surfaces withinthe engine room should be insulated if highair temperatures are to be avoided.

Test With Doors and HatchesClosedVentilating systems must be designed toprovide safe working temperatures andadequate air flow when hatches and doors aresecured for bad weather conditions. Test theventilation system with the vessel fullysecured for bad weather. This condition willreflect the most severe test of the ventilationsystem.

Air Velocity for PersonnelComfortMaintain air velocity of at least 1.5 m/s (5 ft/s) in working areas adjacent to sourcesof heat, or where air temperatures exceed100°F (35°C). This does not mean that all theair in the engine room should be agitated soviolently. High air velocity around enginesand other heat sources is not good ventilationpractice. High velocity air aimed at engineswill hasten transfer of heat to the air, raisingaverage engine room air temperature.

8

Exhaust SystemGeneral InformationWet Exhaust SystemDry Exhaust SystemExhaust Backpressure LimitsMeasuring BackpressureWarning Against “Common” Exhaust SystemsSlobber (extended periods of insufficient load)

General InformationThe exhaust system carries the engine’sexhaust gases out of the engine room,through piping, to the atmosphere.

A good exhaust system will have minimumback pressure.

Exhaust back pressure is generallydetrimental as it tends to reduce the air flowthrough the engine. Indirectly, exhaust backpressure tends to raise exhaust temperaturewhich will reduce exhaust valve andturbocharger life. There are two general typesof exhaust systems seen on boats, wetexhaust systems and dry exhaust systems.

Wet Exhaust SystemWet exhaust systems are characterized by thefollowing:

• Generally the exhaust gases are mixed withthe sea water which is discharged from thesea water side of the engine’s jacket waterheat exchanger.

• Particulate and condensable/solublegaseous emissions from the exhaustsystem are effectively scrubbed from theexhaust gases, reducing the possibility ofatmospheric pollution. Exhaust pipingwhich is cool enough to be made ofuninsulated, fiberglass reinforced plastic(FRP) or rubber.

• The moisture of exhaust gases and seawater is discharged from the boat at orslightly below the vessels waterline.

• With the relatively small elevationdifference between the engine’s exhaustdischarge elbow and the vessels waterline,it is difficult to design a system which willalways prevent water from entering theengine through the exhaust system. Whilea number of proprietary exhaust componentsare available to help avoid this problem, themost common generic methods areexhaust risers and water lift mufflers.

Exhaust RisersOne way to minimize the possibility of waterentering the engine from backflow in the wetexhaust system is to have a steep downward

slope on the exhaust piping, downstream ofthe engine.

Exhaust risers are pipes which elevate theexhaust gases, allowing a steeper slope in thedownstream piping.

The risers must be insulated or water-jacketedto protect persons in the engine compartmentfrom the high temperatures of the exhaustgas in the riser. The sea water is not injectedinto the exhaust gases until downstream ofthe top of the riser, so the upward-slopingportion of the riser is dangerously hot if notinsulated or water-jacketed.

The weight of locally fabricated risers (notprovided by Caterpillar) must be supportedfrom the engine and marine transmission. Donot attempt to carry the weight of the risersfrom the boat’s overhead or deck structure.The risers will vibrate with theengine-transmission. The risers must besupported independently from the hull toavoid transmitting those vibrations into theboat’s structure and passenger compartments.

Exhaust risers (for other than the smallestCaterpillar Engines) are not available fromCaterpillar; the diversity of the various boatbuilders engine compartments preventsdesigning a riser with wide usability. Seefabricators of custom exhaust components forexhaust risers.

11

Figure 2.1

Water Lift MufflersAnother way to minimize the possibility ofwater entering the engine from backflow inthe wet exhaust system is by using a water liftmuffler.

Water lift mufflers are small, sealed tanks,mounted to the deck in the enginecompartment. The tanks have two (2)connections, an inlet connection and an outletconnection. An additional small drainconnection in the bottom is often provided.The inlet enters the tank through the top orside.

The tubing of the inlet connection does notextend past the tank walls. The tubing of

the outlet connection enters the tank walls,through the top, and extends to the bottom ofthe tank, where it terminates on an angle.

As the mixture of seawater and exhaust gasenters the tank from the inlet connection, thewater level rises in the tank. As the waterlevel rises, the water surface graduallyreduces the gas flow area entering thedischarge pipe. The reduced area for gas flowcauses a great increase in gas velocity. Thehigh speed of the gases, entering the outletpipe, finely divides the water. The finelydivided water is transported to the highestelevation of the exhaust piping as a mist ofwater droplets.

12

10

11

4

235

1

6

89

7

WET EXHAUST SYSTEM USING DRY EXHAUST ELBOWSAT ENGINE EXHAUST DISCHARGE

≥ diameter of pipe

1. turbocharger heat shield2. flexible pipe connection3. elbow— bend radius4. insulation, must not restrict flexibility of 25. elbow (min 150 ) with water discharge ring

CL

6. exhaust hose 7. connecting exhaust pipe 8. surge pipe 9. discharge pipe10. raw water discharge connection11. support from overhead structure

Figure 2.2

If good design practice is not followed, theengines exhaust back pressure limit is easilyexceeded. The vertical (upward sloping)portion of piping immediately downstream ofa water lift muffler must be designed as apneumatic conveyer, using high exhaust gasvelocities to lift finely divided droplets of thesea water to a point from which the gas/watermixture can be safely allowed to drain to thethru-hull fitting.

The designer should size the diameter of theupward sloping portion of the exhaustpiping—between the water lift muffler and thehighest system elevation—such that thevelocity of the exhaust-gas-and-water dropletmixture is not below 25.4 m/sec(5000 ft/min), with the engine running atrated load and speed.

If this velocity is not maintained, the waterdroplets will not remain in suspension. Thewater will be forced out of the reservoir of thewater lift muffler as a solid slug of water. Thiswill cause the exhaust back pressure to be thesame as a column of water the height of theupward sloping muffler discharge piping.

If the velocity in the upward sloping mufflerdischarge piping is kept above 25.4 m/sec(5000 ft/min), then the exhaust back pressurewill be much lower.

Hose vs Rigid Exhaust PipeThe weight and heat of the water and exhaustgases can cause nonrigid exhaust piping tosag or deform, leaving low spots between pipesupports.

If the slope of the piping is too shallow, waterwill collect in the low spots and choke off theflow of exhaust gas. This will lead toexcessive exhaust back pressure, smoke, highexhaust temperatures and, in severe cases,premature engine failures.

Hose and other nonrigid piping must beevenly supported over its entire length.

13

Figure 2.3

Preventing Wave Action FromForcing Water Into Wet ExhaustSystemsWaves, striking the hull’s exhaust opening,can force water up into the exhaust system. Ifthe waves are severe, or if the exhaust systemdesign allows, the water can reach the engine.Early turbocharger failure or piston seizuremay result.

There are a number of ways the kineticenergy of waves entering the engine’s exhaustsystem can be harmlessly dissipated.

The traditional method of preventing waterfrom entering an idle engine is to locate theengine far enough above the water line thatbreaking waves do not reach the height of theexhaust elbow. While the relative elevation ofthe engine to the water line is fixed andunchangeable, it is possible to design anexhaust system which protects the enginefrom ingesting water.

Features of such an exhaust system willinclude the following:

• Sufficient elevation difference between thewater line and the highest point in theexhaust piping to prevent even smallamounts of water from reaching the engine.

• Some method of dissipating the kineticenergy of the waves as they enter theexhaust piping. The more effective themethod of wave energy dissipation, thelower the elevation difference required.

In no case should the elevation differencebetween the water line and the highest pointin the exhaust piping be less than 560 mm(22 in.).

Surge ChamberA surge chamber is a branch of the exhaustpiping, near the engine, which has one endclosed off. When a wave of water enters theexhaust pipe and moves toward the engine,the air trapped in front of the wave will becompressed into the surge chamber. Thecushion of compressed air in the surgechamber will force almost all waves back out.

14

Exhaust discharging pipe musthave adequate slope toavoid water entering engine

24

2

2

2

2

5

1

3

WET EXHAUST SYSTEM(Engine Mounted Above Water Line)

Figure 2.4

1. water cooled exhaust elbow on engine - sea water cools elbow, then discharges through peripheral slot at discharge end of elbow into exhaust pipe2. rubber exhaust hose flexible connection - must be oil and heat resistant

3. backwater surge chamber - prevents sea water surging into engine exhaust when vessel at rest with stern exposed to oncoming waves4. exhaust pipe - should have slight downward gradient toward discharge end5. end cover plate - removable for inspection and cleanout purposes

Slope

Valve in Exhaust DischargeA valve located where the exhaust pipingpenetrates the hull can keep waves fromentering the exhaust piping when the engineis not running. The valve mechanism shouldnot include any components which rely onsliding contact to maintain flexibility. Thistype of action has proven troublesome in anatmosphere of salt water and exhaust gas. Aflexible strip of one of the chemically inertplastics can provide hinge action.

Valves in Exhaust Water CoolingLinesThe cooling water which is injected into theexhaust gas stream must not be interrupted,for any reason, while the engine is running.Without a dependable supply of cooling water,the high temperature of the exhaust gaseswill cause severe and rapid deterioration ofplastic or rubber exhaust pipe, with potentiallydisastrous consequences.

Therefore, to protect against inadvertent lossof exhaust system cooling, shut-offs orvalves of any kind must never be used inthe lines supplying cooling water to watercooled exhaust fittings.

Location of Exhaust DischargeOpeningAll diesel engines will eventually dischargesome smoke through their exhaust systems ifnot when they are new, then certainly nearthe end of their useful time before overhaul.Locating exhaust discharge openings as far aftas possible will minimize the hull and deckarea exposed to the eventual discoloration.

Dry Exhaust SystemDry Exhaust System WarningsInsulationIt is the responsibility of the engine installerto protect combustible parts of the boat andprovide personnel protection from the heat ofdry exhaust systems piping. Exposed partsof dry exhaust piping can exceed 650°C(1200°F).

Rain/SprayIt is the responsibility of the engine installerto provide appropriate drain connections, raincaps or other means to protect the enginefrom rainwater or sea spray entering theengine through the dry exhaust piping. Longruns of exhaust piping require traps to drainmoisture. Traps installed at the lowest point ofthe line near the exhaust outlet prevent rainwater from reaching the engine.

Slope exhaust lines from engine and silencerto the trap so condensation will drain.

Traps may be built by inserting a vertical pipe,with a drain petcock, down from a tee sectionin the line.

Slope the last few feet of the exhaust pipedischarge to prevent rain water or spray fromentering the pipe. Alternatively, fit some formof rain cap to a vertical exhaust pipe section.

Saw cuts in the exhaust pipe to allowrain/spray to drain harmlessly. Deform theedges of all slots. Use a punch on engine sideslot edges. Bend inward. Cut through nomore than 60° of the pipe circumference.

Exhaust Gas RecirculationExhaust stacks must be designed so engineexhaust is discharged high enough, and in adirection to keep it clear of the air turbulencecreated by wind swirling around the vessel’ssuperstructure. Engine air cleaners,turbochargers and aftercoolers clogged withexhaust products will cause engine failures.

15

Figure 2.5

RAIN/SPRAYDRAIN SLOTS

punch engine - side slotedges inbend discharge - sideslot edges out

VentilationMufflers and other large dry exhaust systemcomponents would be best mounted outsidethe engine compartment.

This is suggested to minimize the additionaland unnecessary load on the machinerycompartment’s ventilation system.

Flexible ConnectionsThe exhaust pipe must be isolated from theengine with flexible connections. They shouldbe installed as close to the engine’s exhaustoutlet as possible. A flexible exhaustconnection has three primary functions:

• To isolate the weight of the exhaust pipingfrom the engine. No more than 28 kg(60 lb) of exhaust piping weight should besupported by the engine.

• To relieve exhaust components ofexcessive vibrational fatigue stresses.

• To allow for relative shifting betweenreference points on engine exhaustcomponents. This shifting has numerouscauses. It may result from expansion andcontraction of components due totemperature changes, or by slow but

continual creep processes that take placethroughout the life of any structure.

Softness or flexibility is very important toprevent excessive vibratory stresses. Theflexible connector must have high fatigue lifeto enable it to survive for indefinite periods.Softness prevents transmission of vibrationbeyond the connection. Resistance to fatiguekeeps it from breaking under vibratory orrecycling stresses.

To prevent the exhaust coupling from flexingduring exhaust system construction, it isrecommended that straps be tack weldedbetween the two flanges to make the couplingrigid. Remove these straps before starting theengines.

The growth and shrinkage of the exhaust pipemust be planned or it will create excessiveloads on exhaust piping and supportingstructure. Long runs of dry exhaust pipes canbe subjected to very severe stresses fromexpansion and contraction. From its coldstate, a steel exhaust pipe will expand about0.11 mm/m for each 100°C rise of exhausttemperature (0.0076 in./ft of pipe for each100°F). This amounts to about 52 mm

16

BorC

A

Free Length

INSTALLATION LIMITATIONSOF BELLOWS - TYPE FLEXIBLE EXHAUST FITTING

A.max. offset

between flangesmm in.

B.max. compression

from free lengthmm in.

C.max. extensionfrom free length

mm in.

0.12.25.38.50.75

1.00.50.28.20.00.00

25.412.77.115.08.00.00

1.50.90.60.40.23.00

38.122.8615.2410.165.840.0

03.056.359.6512.7

19.05

Spring Rate of Bellows = 19.21 N/m (170 lb/in.) Approx.

If bellows-type exhaust fittings aredistorted beyond limits shown in tablewhile engine is operating at full throttle,service life will be greatly reduced.

"Lagging" or insulation must notrestrain flexibility of bellows.

Figure 2.6

expansion per m from 35°C to 510°C(0.65 in. expansion for each 10 ft of pipe from100°F to 950°F).

Divide long runs of exhaust pipe into sectionshaving expansion joints between sections.Each section should be fixed at one end andbe allowed to expand at the other.

It is of utmost importance that the flexiblepipe connection, when insulated, be insulatedin such a way that the flexible pipe connectioncan expand and contract freely within theinsulation. This generally requires either asoft material or an insulated sleeve to encasethe flexible pipe connection.

17

DRY EXHAUST SYSTEM

Engine Exhaust Outlet

Flexible Pipe Connection

Flexible Pipe

Connection

Flexible Pipe

Connection

LongSweepElbow

Long SweepElbow

VerticalPipe

Support

Drain

Expansion Sleevewith Spray Shield

PipeSupport

PipeSupport

Slight Pitch Awayfrom Engine

Figure 2.7

Dry Exhaust System PipeSupportsThe exhaust piping supports/hangers arevery important. If the piping is supported withsome flexibility between the piping and thestructure of the boat, the boat will be muchquieter and more comfortable for theoccupants.

Exhaust Ejector-AutomaticVentilationA relatively simple system utilizing anengine’s exhaust for ventilating an engineroom can be utilized with most dry exhaustsystems.

Utilizing the normally wasted kinetic energyof discharging exhaust gases, this systemmay draw out a quantity of ventilating airapproximately equal to the flow of exhaustgas.

Air must be allowed to enter theengine room freely.A useful rule of thumb is:

• Use 10 cm2 of duct cross section area perengine kilowatt and not more than three (3)right angle bends.

• Use 1.25 in.2 of duct cross section area perengine horsepower and no more than three(3) right angle bends.

If more right angle bends are required,increase the pipe diameter by one pipe size.

For best results, the intake air openingsshould discharge cool air into the engineroom near the floor level. After the intake airhas been heated by contact with hot surfacesin the engine room, draw the ventilating airout from a point directly over the engines,near the engine room overhead.

Place the ejector in the exhaust system justprior to the exhaust’s discharge toatmosphere to avoid back pressure on themixture of exhaust gas and hot air throughany length of stack. Any bends in the exhauststack following the mixture can seriouslyaffect the system’s performance.

Furthermore, the exhaust stack will remaincooler and cleaner if the engine exhaust iscontained within the exhaust pipingthroughout its run through the stack. Thedischarged ventilation air will tend to cool theexhaust stack upstream of the point where itis mixed with the exhaust gases.

Exhaust ejectors are most effective on vesselswith only one propulsion engine. On multipleengine installations, if one engine is operatedat reduced load, the ejector air flow for theengine with reduced load may reverse, pullingexhaust gas from the more heavily loadedengine into the engine room. The followingdiagrams illustrate methods of laying out thesystem:

18

Dimension Chart

FlangeType

P/N NominalID

FlangeOD Bolt Circle # of Bolts

HoleDiameter

OverallLength

mm(in.)

mm(in.)

mm(in.)

mm(in.)

mm(in.)

127(5)152(6)203(8)304(12)

3N3015

3N3017

5L6297

5N9505

Rect.

Rect.

Circ.

Circ.

4

4

8

12

163*(6.42)203***(8.00)274(11)400

(15.75)

127**(5)

152****(6)250

(9.875)375

(14.75)

16.7(.657)16.7

(.657)15.875(.625)13.8

(.500)

457(18)609(24)304(12)304(12)

* This dimension is the length of each side of a square flange.** This dimension is from bolt center to bolt center along a side of the rectangular flange.

*** This dimension is the length of each side of a square flange.**** This dimension is from bolt center to bolt center along a side of the rectangular flange.

19

24.5 L

1.5 L

2 L

0.5 L 3.75 L

5

6

3

4

D

1

2.75 Lormore

Figure 2.8

D = diameterL = X diameter

Example: 3.75 L = 3.75 X diameter

20

5

6

D

5

12

2.25 Lor more

900*

450*

1.5 L

4.5 L

Figure 2.9


21

2L

2.25 L

D

Figure 2.10


Formulae for System Diameterto Back Pressure Limits.These formulae allow the exhaust systemdesigner to calculate a pipe diameter which,when fabricated into an exhaust system, willgive exhaust back pressure less than theappropriate limit.

Calculate the pipe diameter according to theformula, then choose the next largercommercially available pipe size.

Exhaust Pipe Diameter to Meet BackPressure Limits(Metric Units System)P = Back pressure limit (kPa) See section on

exhaust back pressure limits for specificengine.

D = Inside diameter of pipe (mm)

Q = Exhaust gas flow (m3/min). See engineperformance curve.

L = Length of pipe (m). Includes all of thestraight pipe and the straight pipeequivalents of all elbows.

S = Specific weight of gas (kg/m3)

Exhaust Pipe Diameter to Meet BackPressure Limits(English Units System)

P = Back pressure limit (inches of water). Seesection on exhaust back pressure limitsfor specific engine.

D = Inside diameter of pipe (inches).

Q = Exhaust Gas Flow (ft3/min). See engineperformance curve.

L = Length of pipe (feet). Includes all of thestraight pipe and the straight pipeequivalents of all elbows.

S = Specific weight of gas (lb/ft3).

Formulae for Straight PipeEquivalent Length of VariousElbowsTo obtain straight pipe equivalent length ofelbows:

English MetricUnits Units

Standard Elbow (radius of elbow equals thepipe diameter)

Long Radius Elbow radius greater than 1.5pipe diameters

45° Elbow

Where:L = Straight Pipe Equivalent Length of ElbowsD = Pipe Diameter

Useful Facts for Exhaust SystemDesignersConversion Factorspsi = 0.0361 x in. of water columnpsi = 0.00142 x mm of water columnpsi = 0.491 x in. of mercury

columnkPa = 6.3246 x mm of water columnkPa = 4.0 in. of water columnkPa = 0.30 x in. of mercury columnkPa = 0.145 psi

22

D = 3600000 LSQ2

P5

S (kg/m3) = 352

Exhaust Temperature + 273°F

D = LSQ2

187P5

S (lb/ft3) = 39.6

Exhaust Temperature + 460°F

L = 33D12 L = 33

D1000

L = 20D12 L = 20

D1000

L = 15D12 L = 15

D1000

Mufflers Exhaust noise attenuation is best performedwith a quality muffler. However, theattenuation characteristics of a muffler are notthe same for all frequencies. The effect of agiven muffler could be quite different if theengine runs at two different speeds. Themanufacturer must be contacted for anyspecific muffling characteristics.

The location of the muffler within the exhaustpiping, whether close to the engine or nearerthe exhaust outlet, and the number of enginecylinders is important. It will affect theefficiency of the muffler. The sketch belowoffers suggestions for the most efficientmuffler location.

Exhaust Back PressureLimitsAs the exhaust gas moves through theexhaust system, it experiences frictionalresistance—causing back pressure on theengine’s turbocharger discharge. Exhaustsystem back pressure has a number of badeffects on the engine.

Excessive back pressure will shorten exhaustvalve and turbocharger life due to increasedexhaust temperatures. Excessive exhaustback pressure wastes fuel as well.

23

L*

L*

L*

1/3 L 2/3 L

2/3 L 1/3 L

4/5 L 1/5 L

Engine

Engine

Engine

For In-Line and Vee With DividedExhaust System

For Vee Engine With Single Exhaust

Alternate For All In-Line and Vee

*L Is Total Length of Exhaust Piping Excluding The Muffler

MUFFLER LOCATION

Figure 2.11

To ensure the above limits are not exceededduring operation, it is recommended thedesign limit be not more than one-half thespecified back pressure limits.

Measuring Back PressureMeasure exhaust back pressure by a watermanometer at the fitting provided in theengines exhaust discharge location. Use asystem similar to that shown below.

24

Maximum Exhaust Back Pressure Limits

Metric Units English Units

8.47 kPaNaturally Aspirated Engines 34 in. H20

6.72 kPaTurbocharged Engines 27 in. H20

Except for those specifically listed below:

9.96 kPa435 hp 3208, 3116, 3126 Propulsion Engines 40 in. H20

The limits on 3600 are competitive with other mediumspeed diesels. Higher pressure will affect performanceand fuel consumption.

3600 Family Engines

48

36

24

12

Figure 2.12

IN.

Manometer in use

Warning AgainstCommon ExhaustSystemsAlthough economically tempting, a commonexhaust system for multiple engineinstallations is rarely acceptable. Combinedexhaust systems allow operating engines toforce exhaust gases into engines notoperating. Every gallon of fuel burnedprovides about one gallon of water in theexhaust. This water vapor condenses in coldengines and quickly causes engine damage.Soot clogs turbochargers, aftercoolers or aircleaner elements. Duct valves separatingengine exhausts is also discouraged. Hightemperature warp valve seats or soot depositscause leakage.

Slobber (ExtendedPeriods of InsufficientLoad)Extended engine operation at no load orlightly loaded conditions (less than 15% load)may result in exhaust manifold slobber.Exhaust manifold slobber is the black oilyfluid that can leak from exhaust system joints.The presence of exhaust manifold slobberdoes not necessarily indicate an engineproblem. Engines are designed to operate atloaded conditions.

At no load or lightly loaded conditions, thesealing capability function of some integralengine components may be adverselyaffected. Exhaust manifold slobber is notusually harmful to the engine; the results canbe unsightly and objectionable in some cases.

Exhaust manifold slobber consists of fueland/or oil mixed with soot from the inside ofthe exhaust manifold. Common sources of oilslobber are worn valve guides, worn pistonrings and worn turbocharger seals. Fuelslobber usually occurs with combustionproblems.

A normally operating engine should beexpected to run for at least one hour at lightloads without significant slobber. Someengines may run for as long as three, four ormore hours before slobbering. However allengines will eventually slobber if run at lightloads. External signs of slobber will beevident unless the exhaust system iscompletely sealed.

If extended idle or slightly loaded periods ofengine operation are mandatory, theobjectionable effects of the engine slobber canbe avoided by loading the engine to at least30% load for approximately ten minutes everyfour hours. This will remove any fluids thathave accumulated in the exhaust manifold. Tominimize exhaust manifold slobber, it isimportant that the engine is correctly sized foreach application.

25

Marine EnginesApplication andInstallation Guide

● Lubrication Systems

● Fuel Systems


Lubrication SystemsGeneral InformationRecommended Oils for Various Caterpillar ProductsContaminationChanging Lubrication OilEngine Lube Oil Flow SchematicFilter Change TechniqueLubricating Oil HeatersEmergency SystemsDuplex FiltersAuxiliary Oil SumpsPrelubricationSpecial Marking of Engine Crankcase DipstickSynthetic Lubricants and Special Oil Formulations

General InformationBearing failure, piston ring sticking andexcessive oil consumption are classicsymptoms of oil related engine failure. Thereare numerous ways to avoid them. Three of themost important are Scheduled Oil Sampling(S•O•S), regular maintenance of the lubricationsystem, and the use of correct lubricants.Taking these measures can mean thedifference between experiencing repeated oilrelated engine failure and benefiting from aproductive and satisfactory engine life. Thefollowing information will acquaint the readerwith oil; what it is composed of and what itsfunctions are, how to identify its contaminationand degradation, typical consequences, andsome preventive measures to help you protectyour engine against the devastating effects ofoil related engine failure.

FunctionEngine oil performs several basic functions:

It cleans the engine by carrying dirt and wearparticles until the filters can extract and storethem.

It cools the engine by carrying heat awayfrom the pistons, cylinder walls, valves, andcylinder heads to be dissipated in the engineoil cooler.

It cushions the engine’s bearings from theshocks of cylinder firing.

It lubricates the wear surfaces, reducing friction.

It neutralizes the corrosive combustion products.

It seals the engine’s metal surfaces from rust.

AdditivesLubricating oil consists of a mixture of baseoil fortified with certain additives. Dependingon the type of base, paraffinic, asphaltic,naphthenic or intermediate (which has someof the properties of the former), differentadditive chemistries are used.

Additive TypesThe most common additives are: detergents,oxidation inhibitors, dispersants, alkalinityagents, anti-wear agents, pour-pointdispersants and viscosity improvers.

Detergents help keep the engine clean bychemically reacting with oxidation products tostop the formation and deposit of insolublecompounds.

Oxidation inhibitors help prevent increases inviscosity, the development of organic acidsand the formation of carbonaceous matter.

Dispersants help prevent sludge formation bydispersing contaminants and keeping them insuspension.

Alkalinity agents help neutralize acids.

Anti-wear agents reduce friction by forming afilm on metal surfaces.

Pour-point dispersants keep the oil fluid at lowtemperatures by preventing the growth andagglomeration of wax crystals.

Viscosity improvers help prevent the oil frombecoming too thin at high temperatures.

Total Base Number (TBN)Understanding TBN requires someknowledge of fuel sulfur content. Most dieselfuel contains some degree of sulfur. One oflubricating oils functions is to neutralize sulfurby-products, retarding corrosive damage tothe engine. Additives in the oil containalkaline compounds which are formulated toneutralize these acids. The measure of thisreserve alkalinity in an oil is known as itsTBN. Generally, the higher the TBN value,the more reserve alkalinity oracid-neutralizing capacity the oil contains.

ViscosityViscosity is the property of oil which definesits thickness or resistance to flow. Viscosity isdirectly related to how well an oil willlubricate and protect surfaces that contact oneanother. Oil must provide adequate supply toall moving parts, regardless of thetemperature. The more viscous (thicker) anoil is, the stronger the oil film it will provide.The thicker the oil film, the more resistant itwill be to being wiped or rubbed fromlubricated surfaces. Conversely, oil that is toothick will have excessive resistance to flow atlow temperatures and so may not flow quicklyenough to those parts requiring lubrication. Itis therefore vital that the oil has the correct

1

viscosity at both the highest and the lowesttemperatures at which the engine is expectedto operate. Oil thins out as temperatureincreases. The measurement of the rate atwhich it thins out is called the oil’s viscosityindex (or VI). New refining techniques andthe development of special additives whichimprove the oil’s viscosity index help retardthe thinning process.

The Society of Automotive Engineers (SAE)standard oil classification system categorizesoils according to their quality.

CleanlinessNormal engine operation generates a varietyof contamination—ranging from microscopicmetal particles to corrosive chemicals. If theengine oil is not kept clean through filtration,this contamination would be carried throughthe engine via the oil.

Oil filters are designed to remove theseharmful debris particles from the lubricationsystem. Use of a filter beyond its intended lifecan result in a plugged filter.

A plugged filter will cause the bypass valve toopen releasing unfiltered oil. Any debrisparticles in the oil will flow directly to theengine. When a bypass valve remains open,the particles that were previously trapped bythe filter may also be flushed from it and thenthrough the open bypass valve. Filterplugging can also cause distortion of theelement. This happens when there is anincrease in the pressure difference betweenthe outside and inside of the filter element.Distortion can progress to cracks or tears inthe paper. This again allows debris to flowinto the engine where it can damagecomponents.

Recommended Oils forVarious CaterpillarProductsRefer to Operation and MaintenanceManual for lubricaiton specifications.

ContaminationContamination refers to the presence ofunwanted material or contaminants in the oil.

There are seven contaminants commonlyfound in contaminated oil.

1. Wear ElementsWear elements are regarded as thoseelements whose presence indicates a partor component which is wearing. Wearelements include: copper, iron, chromium,aluminum, lead-tin, molybdenum, silicon,nickel, and magnesium.

2. Dirt and SootDirt can get into the oil via air blowingdown past the rings and by sticking to theoil film and being scraped down fromcylinder walls. Soot is unburned fuel.Black smoke and a dirty air filter indicateits presence. It causes oil to turn black.

3. Fuel

4. WaterWater is a by-product of combustion andusually exits through the exhaust stack. Itcan condense in the crankcase if theengine operating temperature isinsufficient.

5. Ethylene Glycol/Antifreeze

6. Sulfur Products/Acids

7. Oxidation ProductsOxidation Products Oxidation productscause the oil to thicken; oxidation rate isaccelerated by high temperature of theinlet air.

Diagnostic TestsCaterpillar’s Scheduled Oil Sampling (S•O•S)program is a series of diagnostic testsdesigned to identify and measurecontamination and degradation in a sample ofoil. S•O•S is composed of three basic tests:

1. Wear Analysis

2. Chemical & Physical Tests

3. Oil Condition Analysis

A brief explanation of what each of these testsinvolves is in order.

2

Wear AnalysisWear analysis is performed with an atomicabsorption spectrophotometer. Essentially,the test monitors a given component’s wearrate by identifying and measuringconcentrations of wear elements in oil. Basedon known normal concentration data,maximum limits of wear elements areestablished. After three oil samples are taken,trend lines for the various wear elements canbe established for the particular engine.Impending failures can be identified whentrend lines deviate from the established norm.

Wear analysis is limited to detectingcomponent wear and gradual dirtcontamination. Failures due to componentfatigue, sudden loss of lubrication or suddeningestion of dirt occur too rapidly to bepredicted by this type of test.

Chemical & Physical TestsChemical and physical tests detect water, fueland antifreeze in the oil and determinewhether or not their concentrations exceedestablished limits.

The presence and approximate amount ofwater is detected by a sputter test. A drop of oilis placed on a hot plate controlled at110°C (230°F). The appearance of bubbles isa positive indication (0.1% to 0.5% is theacceptable range).

The presence of fuel is determined with aSetaflash Tester. The tester is calibrated toquantify the percentage of fuel dilution.

The presence of antifreeze can also bedetermined by a chemical test. (Anyindication that is positive is unacceptable.)

Oil Condition AnalysisOil condition analysis is performed viainfrared analysis. This test determines andmeasures the amount of contaminants such assoot and sulfur, oxidation and nitrationproducts. Although it can also detect waterand antifreeze in oil, infrared analysis shouldalways be accompanied by wear analysis andchemical and physical tests to assure accuratediagnosis. Infrared analysis can also be usedto customize (reduce, maintain, or extend) oil

change intervals for particular conditions andapplications.

Recognizing the Causes &Effects of ContaminationS•O•S identifies and measures variouscontaminants in the oil which cause enginefailure. For example, a high concentration ofcopper indicates thrust washer or bushingwear. A high concentration of chromiumindicates piston ring damage (with theexception of plasma coated rings). S•O•Sgives you an opportunity to inspect thecondition of these parts and, if necessary, takeaction to prevent further damage. Here aresome examples of typical contaminants andwhat effect they have on the condition of yourengine.

SiliconAbove normal readings of silicon can indicatea major problem. Oil loaded with siliconbecomes, in effect, a grinding compoundwhich can remove metal from any number ofparts during operation.

SodiumA sudden increase in sodium readingsindicates inhibitor leaking from the coolingsystem. Inhibitor may indicate antifreeze inthe system which can cause oil to thicken andbecome like sludge, leading to piston ringsticking and filter plugging.

Silicon, Chromium, IronA combination such as this signals dirt entrythrough the induction system, possiblycausing ring and liner wear.

Silicon, Iron, Lead, AluminumThis combination indicates dirt in the lowerportion of the engine, possibly leading tocrankshaft and bearing wear.

AluminumThis can be critical. Concentrations ofaluminum suggest bearing wear. Relativelysmall increases in the levels of this elementshould receive immediate attention becauseonce rapid wear begins, the crankshaft mayproduce large metal particles which willbecome trapped in the oil filters.

3

IronIron can come from any number of sources. Itcan also appear as rust, after engine storage.Frequently, when accompanied by a loss of oilcontrol, increases in iron contaminationindicate severe liner wear.

SootA high soot content is not usually the directcause of failure but as solid particles whichwill not dissolve in the oil, it can plug oilfilters and deplete dispersant additives. Sootindicates a dirty air cleaner, engine lug,excessive fuel delivery, or repeatedacceleration in the improperly set rack limiter(smoke limiter). It can also indicate a poorquality fuel.

WaterWater combined with oil will create anemulsion which will plug the filter. Water andoil can also form a dangerous metal corrodingacid. Most instances of water contaminationare the result of condensation within thecrankcase. More serious contaminationoccurs when a leak in the cooling systemallows water to enter from outside the engineoil system.

FuelFuel contamination decreases the oil’slubricating properties. The oil no longer hasthe necessary film strength to prevent metal-to-metal contact. This can lead to bearingfailure and piston seizure.

SulfurThe presence of sulfur signals danger to allengine parts. The type of corrosive wearattributed to high sulfur content can also

cause accelerated oil consumption. Also, themore fuel consumed during an oil changeinterval, the more sulfur oxides are availableto form acids. Therefore, an engine workingunder heavy loads should be checked moreoften. Also, its TBN should be checked morefrequently. Fuel sulfur damage can causepiston ring sticking, and corrosive wear of themetal surfaces of valve guides, piston ringsand liners.

Engine operating conditions can also play amajor role in the type and degree of oil

contamination. A dry environment will forinstance affect silicon readings. Anotherexample is engines which stand idle for longperiods at a time. The liners in such engineswill rust at an unusually rapid rate; oil sampleswill reveal high iron readings.

Changing Lubrication OilChanging lubrication oil can be simplified byusing a system as described below: Install amachine thread-to-pipe-thread adapter* in theoil pan drain.

Connect a length of flexible, oil andtemperature resistant hose to the adapter.Engine vibration working against a rigid pipecan cause drain boss failure in the oil pan inshort time.

Connect the other end of the hose to the inletof a small, electric motor-driven pump.Control the pump motor with a key-operatedswitch. Use a key-operated switch to preventunauthorized operation of the pump.

Connect the discharge of the motor-drivenpump to a dirty oil tank for storage of theused lube oil until proper disposal is practical.

Keep the Key on the Captain’s Key Ring.

Check oil level prior to every engine start.

* Adapter 6L6155 is available to convert the oil panmachine threads to 1/2-14 NPTF female threads forremote oil draining of the 3304B, 3306B, 3406B, and3408B Marine Engines. Seal 8M4432 and washer1S3889 are required to prevent leakage between thepan drain boss and the adapter.

Adapter 3N9442 and Gasket 3B1925 are available toconvert from machine threads to 1/2-14 NPTF femalethreads on 3208 Marine Engines.

4

5

TurboCharger

7

6

4

89

2

5

1

3

Engine Lube Oil Flow Schematic

1. Sump – lube oil is drawn from the sump through a strainer into the inlet of the lube oil pump.2. Lube Oil Pump – the quantity of lube oil delivered by the lube oil pump exceeds the engine's needs when the engine is new. As the engine clearances increase through normal wear, the flow required to properly lubricate the engine will remain adequate.3. Oil Pressure Regulating Valve – this valve regulates oil pressure in the engine and routes excess oil back to the sump.4. Lube Oil Cooler – the oil to the engine is cooled by jacket water in the engine oil cooler .5. Oil Cooler Bypass Valve – when the viscosity of the oil causes a substantial pressure drop in the oil cooler, the bypass valve will open,

causing the oil to bypass the cooler until the oil is warm enough to require full oil flow through the cooler.6. Lube Oil Filter – Caterpillar lube oil filters are the full-flow type with a bypass valve to provide adequate lubrication should the filter become plugged. The filter system may have the replaceable element type or the spin-on type. The oil filter bypass valve is a protection against lube oil starvation if the oil filter clogs.7. Engine Oil Passages – the main oil flow is distributed through passages to internal engine components. The oil flow carries away heat and wear particles and returns to the sump by gravity.8. Prelubrication Pump – used only during starting cycle on largest engines.9. Check Valve.

Figure 1.1

Filter Change TechniqueSpin-on oil filters are conveniently changed bygripping the loosened used oil filter with aplastic garbage bag. As the used oil filter isthen removed, the oil which might have soiledthe engine compartment can be caught by thegarbage bag.

Lubricating Oil HeatersCaterpillar does not recommend the use ofimmersion-type lubrication oil heaters due totheir tendency to overheat the oil in contactwith the heating element. This overheatingcauses deterioration and sludging of thelubricating oil and may lead to prematureengine failure.

Emergency SystemsSome marine applications require thecapability to connect an emergencylubricating oil pump into the engine’s lubesystem.

This is a specific requirement of some marineclassification societies for seagoing singlepropulsion engine applications. The purposeis to ensure lube oil pressure and circulation ifthe engine lube pump fails.

Requirements for emergency lube systemoperation:

1. Keep pressure drops to a minimum byusing short, low restriction lines.

2. Use a line size at least as large as theengine connection point.

3. Install a low restriction strainer in front ofthe emergency oil pump.

4. Install a low restriction check valvebetween the emergency pump dischargeand the engine inlet connection.

5. Use a pressure limiting valve in theemergency system set at 8.8 kg/cm2

(125 psi).

Transmissions

Some marine classification societies requireemergency lube oil pumps for marinetransmissions to meet unrestricted serviceclassification.

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Duplex FiltersThe optional Caterpillar Duplex Oil FilterSystem meets the requirements of thestandard filter system plus an auxiliary filtersystem with the necessary valves and piping.The system provides the means for changingeither the main or auxiliary filter elementswith the engine running at any load to speed.A filter change indicator is included to tell

when to change the main filter elements. Avent valve allows purging of air trapped ineither the main or auxiliary system wheninstalling new elements. Air must be purgedfrom the changed section to eliminate possibleturbocharger and bearing damage. Theauxiliary system is capable of providingadequate oil filtration for at least 100 hours under full load and speedoperation.

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Figure 1.2

Auxiliary Oil SumpIf longer oil change periods are desired,consider the auxiliary oil sump. Engine oilchange period is directly proportional to totaloil quantity, all other factors remaining equal.This is: to double oil change period, add anauxiliary oil sump with a capacity equal to theengine mounted oil sump. This will doublethe amount of oil available to becontaminated/diluted/neutralized and allowproportionately longer periods between oilchanges. Previously mentioned considerationsregarding fuel sulfur, oil TBN and oil analysisshould be followed. After a basic changeperiod has been confirmed, then an auxiliaryoil sump may be used to increase the basicperiod-based on fuel quality, oil TBN and oilanalysis.

Auxiliary Oil Sump SystemConsiderations1. Connect the oil source line to the auxiliary

tank as close to the engine oil pump aspossible. The auxiliary oil sump tankmust be full prior to starting theengine. The auxiliary tank must remainfull of oil at all times. As soon as the enginestarts, the auxiliary oil sump will overflow,returning the oil to the engine; exactlycompensating for the oil removed throughthe oil source line to the auxiliary tank.

2. Use a 1.5 to 1.8 mm (0.060 to 0.070 in.)orifice in this line to flow approximately 3.8 L/m (1 Gpm).

3. Put a check valve in the oil pump dischargeline, set to open at 75% of the measuredpressure at the line connection point, whenthe engine is up to temperature and atmaximum operating speed.

8

Figure 1.3

AUXILIARY OIL SUMP CONNECTION SCHEMATIC

1.5 to 1.8 mm (.060 in to .070 in)Maximum DiameterOrifice

Return LineMust HaveContinuous DownwardSlope to Engine 12 mm (1/2 in)minimum inside diameter

Minimum Inside DiameterWith No ValvesorShut-Off Provisionsof Any KindOil Pump

A

Drain Opening

Fill Opening

Vent to Elevation1500 mm (5 ft) AboveHighest Point onEngine

Check ValveOpening Pressure Setfor 75% of Full Load OilPressure Measured at A.

PrelubricationA prelube system provides the capability toprelubricate all critical bearing journals beforeenergizing the starting motors.

The automatic system utilizes a small pumpwhich fills the engine oil galleries from theengine oil sump until the presence of oil issensed at the upper portion of the lubricationsystem. The starter motors are automaticallyenergized only after the engine has beenprelubricated.

The manual system uses the engine’smanually operated sump pump and allows theengine operator to fill all engine oil passagesafter oil changes, filter changes, periods ofidleness, and before activating the startermotors.

Either prelube system will allow the engineoperator to fill all engine oil passages after oilchanges, filter changes, and before activatingthe starter motors. Either system will allowthe engine user to minimize the sometimessevere engine wear associated with startingan engine after periods of idleness.

Special Marking ofEngine CrankcaseDipstickSometimes marine engines are installed andoperated in a tilted position. If the tilt angle issignificant (5° or more) the amount of oilneeded to fill the engine crankcase to the fullmark on the dipstick (usually marked for leveloperation) may be more or less than thecorrect amount the oil pan was intended toaccommodate without uncovering the suctionbell or flooding the crankshaft seal.

The maximum safe tilt angle is dependentupon the design of the oil sump as well as thedipstick location—both of which are notnecessarily uniform for all engine models.Therefore, where a tilted engine installation isencountered it is wise to check and, ifnecessary, remark the standard dipstick inorder to make certain that the high and lowmarks will really reflect the proper amount ofoil for safe engine operation. Oil pressure maybe lost due to an uncovered suction bell, aflooded crankshaft seal may leak excessively,

and engine vibration can be caused bycrankshaft counterweights dipping into theoil. These are all problems that can be causedby an improper amount of oil in the sump.

Procedure1. Drain engine crankcase and remove oil

filter elements.

2. Install new oil filter elements.

3. Fill crankcase with a given volume of oil

(Vf) which can be determined as follows.Vf = Vr – Vm

Where:Vr = Volume of oil required to refill to Full

mark with filter change.Vm = Volume of oil between add mark and

Full mark for level operation.

Note: Both Vr and Vm values for a specificengine model are published in the currentTechnical Marketing Information (TMI) onMarine Engine Systems and PerformanceSpecification Data microfiche under subjectheading Pan-Oil Capacity.

Add to this any additional oil volume requiredfor special filters, oil lines, or coolers whichare additions to the standard engine or uniqueto the installation.

4. Insert the dipstick to make certain thatthe oil shows on the dipstick. Be certainthat the correct dipstick is used and that itdoes not hit the bottom of the sump or isotherwise improperly installed.

5. Start the engine and operate it at one halfrated rpm until the oil has reached normaloperating temperature. Reduce enginespeed to low idle and mark the levelindicated on the dipstick. This is the addoil or low mark.

6. Add additional oil equivalent to Vm asshown in the Technical MarketingInformation (TMI) and let the engineoperate at least another five minutes inorder to bring all the oil up totemperature. Mark the new oil level onthe dipstick. This is the full oil mark.Refer to Operation and Maintenancemanuals for dipstick marking base onintalled tilt angles.

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Synthetic Lubricants andSpecial Oil FormulationsSome producers of synthetic lubricants implytheir products have properties which allowextended oil life.

Caterpillar Inc. neither endorses norrecommends a brand or type of extended oildrain interval crankcase oil for itsengines.Caterpillar recommends (SOS)Schedules Oil Sampling to determine ifextended oil drain periods can be achievedwith synthetics. Caterpillar offers bothpetroleum and synthetic oils which areformulated for maximum wear conditions andlong life because the additive package is onthe high side of the tolerance range ofCG4/CF4 specification.

Crankcase oil is changed because it becomescontaminated with soot (unburned carbon),wear products, partially burned fuel, acids,dirt, and products of combustion. The additivecomponents included in the oil becomedepleted as they perform their intendedfunctions of dispersing soot, preventingoxidation, wear, foaming, etc. Caterpillarrequires petroleum and synthetic enginecrankcase lubricants to meet Engine ServiceDesignation CG4/CF4.

Types of Synthetic OilTwo widely used synthetic oil types use basestocks made of synthetic hydrocarbons or di-basic acid testers. Both types of syntheticbase oils have high viscosity indexes whichmake them advantageous in cold weatheroperations. Their use in any other applicationshould be treated with caution.

The cost of these synthetic base oils rangefrom three to four times the price ofpetroleum based lubricants, and makes theeconomics of their general use questionable.

Another type oil is called a partial syntheticengine oil. This is a petroleum base oil withsome synthetic base oil which is blended forgood cold weather performance.

Special Oil FormulationsCaterpillar does not recommend the use ofadditives to extend oil change periods. Oiladditives such as graphite, teflon,

molybdenum disulfide, etc., which have beenproperly blended into an oil that meets APICG4/CF4 specification can be used inCaterpillar Diesel Engines. These additivesare not necessary to achieve normal life andperformance of the engine.

Normal engine life and performance can beachieved by properly applying the engine, byservicing at recommended oil change period,by selecting the correct oil viscosity, by usinga API CG4/CF4 oil and performing andmaintenance as outlined in the engineoperation and maintenance guide.

Caterpillar does not recommend the use ofmolybdenum dithiophosphate frictionmodifier additive in the engine oil. Thisadditive causes rapid corrosion of bronzecomponents in Caterpillar Diesel Engines.

Oil Publications AvailableFrom CaterpillarThe following publications are availablethrough your local Caterpillar Dealer. Some ofthe publications may have a nominal charge.Some may be revised or discontinued in thefuture. These publications should be ordereddirectly from your dealer. Your dealer canalso assist you in answering questionsconcerning available oils in your operatingarea.

All Engine Data Sheets are included in theCaterpillar Engine Technical Manual, VolumeI, Form No. LEKQ2030.

Synthetic Lubricants and Special OilFormulations LEKQ2051 (Engine Data Sheet90.3)

Special Dipstick Marking of EngineCrankcase Dipstick LEKM3272 (Engine DataSheet 94.0)

Oil Consumption Data LEKQ4028 (EngineData Sheet 96.2)

Oil and Your Engine SEBD0640

Full Synthetic Diesel Engine Oil PEHP7062

Introduction of New Full Synthetic CATDiesel Engine Oil SAE 5W-40 PELE0580

Fuel SystemsGeneral InformationCleanlinessTank DesignFuel LinesFuel SpecificationsFiltersFuel Systems—MiscellaneousAppendix

General InformationCaterpillar Engines have three different typesof fuel systems.

The earliest has the high pressure pumps (forall the cylinders) in a single housing. Theinput shaft for that housing is driven by theengine’s gear train. The high pressure fuelpump housing provides the high pressure fuelto the fuel valves at each cylinder, at theproper time, and in precisely meteredamounts. The fuel valves at each cylinder aresimple and easily replaced.

A later design combines each cylinder’s highpressure pump and the fuel valve in a singleunit; therefore, the term unit injector. Thepower to generate the high pressures forinjection is taken from the engine’s camshaftsby way of pushrods and rocker arms.

Electronic unit injectors use engine camshaftand push rods to generate injection press butuse electronics to time the fuel delivery andthe amount.

Caterpillar Diesel Engine fuel deliverysystems are designed to deliver more fuel tothe engine than is required for combustion.The excess is returned to the fuel tanks.

CleanlinessClean fuel meeting Caterpillar’s fuelrecommendations provides outstandingengine service life and performance; anythingless is a compromise and the risk is the user’sresponsibility. Dirty fuel and fuels not meetingCaterpillar’s minimum specifications willadversely affect:

• The perceived performance of thecombustion system and fuel filters.

• The service life of the fuel injection system,valves, pistons, rings, liners and bearings.

Heat in FuelExcess fuel (returned to the fuel tanks) picksup engine heat and can raise the temperatureof the fuel in the tanks.

To avoid decreased injector life, fueltemperature to the engine must not exceed66°C (150°F). Heat will also increase thespecific volume of the fuel, resulting in apower loss of 1% for each 6°C (10°F) above29°C (85°F) .

If the tank is so located and is of such sizethat the accumulated heat will not beobjectionable when temperature stabilizes,then nothing more needs to be done. If thestabilized fuel tank temperature is high, thereturning fuel should be cooled. See sectionon Fuel Coolers.

Air in FuelGases entrained in the supplied fuel aredischarged from the engine in the returnedfuel. The gases (generally, air introducedthrough leaks in the fuel suction plumbing)must be vented to prevent engine power loss.

Standpipe SystemsThe simplest method for eliminating the airproblems is to install a standpipe between thefuel tank and the engine. Fuel will flow fromthe tank to the bottom of the standpipe bygravity. This is the point where the enginepicks up fuel. The fuel return line must enterthe standpipe at a point a few inches abovethe higher of either the supply or deliverypoint. The top of the standpipe can be ventedinto the top of a fuel tank or to atmosphere.This system works satisfactorily with anynumber of fuel tanks. There must be noupward loops in piping between the fuel tankand the standpipe, as entrapped air may blockfuel flow.

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Fuel CoolersThe excess fuel returned from enginesequipped with unit injectors (1.7 liter, 3500and 3600 Family Engines) can absorbconsiderable heat from the injectors and thesurrounding jacket water. Fuel coolers maybe necessary for proper engine performance.The following factors affect the need for fuelcooling equipment:

• Length of periods of continuousoperation—If the operating periods areshort, the amount of heat returned to thefuel tanks will be relatively small. Fuelcoolers are not generally required forengines used in high performanceapplications.

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FUEL SUPPLY SYSTEM-SINGLE TANKOR DAY TANK

1. Fuel filler2. Fuel tank or day tank3. Drain valve – install at lowest part of tank to enable draining of all water and sediment. Outlet of valve should be plugged when not in use to prevent fuel dripping.4. Fuel discharge valve5. Water and sediment trap – must be lowest point of system.6. Fuel return standpipe7. Primary fuel filter – to be cleanable without shutting down engine8. Fuel supply line to engine

9. Flexible fuel lines connecting to basic fuel delivery system10. Return from engine to standpipe11. Vent from top of standpipe to top of fuel tank12. Vent from top of fuel tank atmosphere-must be high enough above deck to prevent water washing over deck from entering pipe 13. Cleanout drain for water & sediment-valved and kept below fuel discharge from tank, to allow flushing water & sediment tank by gravity feed from supply

Figure 2.1

• Length of time between periods ofoperation—If the time between periods ofoperation is long, the heat will have anopportunity to dissipate.

• Volume of the fuel tank—If thevolume of the fuel tank is large (larger than11 000 L [3,000 gal]), it will accept a greatdeal of heat before the temperature of thefuel leaving the tank increases significantly.

• Ability of the fuel tanks to dissipatethe heat of stored fuel—If the fuel inthe tank is in contact with shell plating*,the fuel heat will be easily dissipated andstored fuel temperature will remain within afew degrees of the ambient watertemperature.

Day Tanks (Auxiliary FuelTanks)

Auxiliary or day tanks are required if the mainfuel tanks are located:

• More than 15.25 m (50 ft) from the engine;• Are located above the engine;• Or are more than 3.65 m (12 ft) below the

engine.

Auxiliary or day tanks also provide a settlingreservoir so air, water, and sediment canseparate from the fuel.

The auxiliary or day tank should be located sothat the level of the fuel is no higher than thefuel injection valves on the engine. If the fuellevel is higher, the static pressure may allowfuel to leak into the combustion chamberswhen the engine is not running. The presenceof liquid fuel in the combustion chamber at theinstant of engine starting is very likely to causeengine failure. The tank should be closeenough to the engine so the total suction lift isless than the 3.65 m (12 ft). The smaller thisfigure, the easier the engine will start.

* The shell plating should be approximately 10% of theinside surface area of the fuel tank.

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Fuel Return Line PressureLimitsEngine fuel pressure measured in the fuelreturn line should be kept below 27 kPa (4 psi), except for the 3300 Engine Family,which is 20 kPa (3 psi) and the 3600 EngineFamily, which is 350 kPa (51 psi). The fuelreturn line must be at least the same size asthe supply line. A shutoff valve is notrecommended.

CleanlinessAll connecting lines, valves, and tanks shouldbe thoroughly cleaned before making finalconnections to the engine. The entire fuelsupply system should be flushed prior toengine start-up.

Tank DesignMaterialFuel tanks are best made from low carbonrolled steel. Zinc, either in the form of platingor as a major alloying component, should notbe used with diesel fuels. Zinc is unstable inthe presence of sulfur, particularly if moistureis present in the fuel. The sludge formed bychemical action is extremely harmful to theengine’s internal components. Zinc should beavoided where continuous contact with dieselfuel is involved.

SizingThe capacity of a fuel tank or tank system canbe estimated by multiplying the averagehorsepower demand by the hours of operation

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Baffle

Baffle

Vent Cap – Locate Away From Flame or Sparks

Engine to Tank(Return Line)

Shut-OffValve

Tank to Engine(Delivery Line)

Main Tank toAux. Tank(Fill Line)

Auxiliary FuelPump

SightGlass

High FuelLevel

Aux. Tank to MainTank Line(Overflow Line)

Pump ControlFloat Switch

Cleaning Access

Sediment andWater Trap

Drain Valve

AUXILIARY FUEL TANK

Figure 2.2

between refuelings, and divide the result by16 for U.S. gallons and by 4 for liters.

This calculation does not allow for any reservecapacity which should be added to this basicrequirement.

Grounding/Bonding (ElectricalConnections)The filler attachment and tank should beconnected with a ground cable if they are notalready connected electrically. The tanksshould also be connected to the vessel’sbonding system.

This is necessary to reduce the fire hazard ofsparks discharged from static electricitybuildup during refueling operations.

DrainsAll fuel tanks should have easily accessibledrain connections. Water and sediment whichcollects in the bottom of the tank must beeliminated regularly.

Provide clean-out openings for periodicalremoval of sediment and trash which settlesout of fuel tanks.

Well-designed tanks have large enough clean-out openings so the lowest part of the fueltank can be accessed with cleaningequipment.

Fuel LinesMaterialBlack iron pipe is best suited for diesel fuellines. Copper pipe or tubing may besubstituted in sizes of 13.0 mm (0.5 in.)nominal pipe size or less. Valves and fittingsmay be cast iron or bronze (not brass). Zinc,either in the form of plating or as a majoralloying component, should not be used withdiesel fuels. Zinc is unstable in the presenceof sulfur, particularly if moisture is present inthe fuel. The sludge formed by chemicalaction is extremely harmful to the engine’sinternal components.

RoutingWhenever possible, route fuel lines under anymachinery, so any leakage will be confined to

the bilges. Leaks from overhead fuel systemcomponents may fall onto hot machinery,increasing the likelihood of fire danger.

SizingDetermine the fuel line sizing by the supplyand return line restriction. The maximumallowable restriction is published in theEngine Performance books (green books).Supply and return lines should be no smallerthan the fittings on the engine.

Fuel SpecificationsCaterpillar Diesel Engines have the capacityto burn a wide variety of fuels. See yourCaterpillar Dealer for current information onfuel recommendations. In general, the enginecan use the lowest priced distillate fuel whichmeets the following requirements:

PropertiesCetane Number or IndexThe cetane index is a measure of the ignitionquality of fuel which affects engine startingand acceleration.

The fuel supplier should know the cetanenumber or index of each fuel shipment.

Precombustion chamber fuel systems requirea minimum cetane number of 35.

Direct injection engines require a minimumcetane number of 40 for good startingcharacteristics.

Engine EffectsFuel with a low cetane number usually causesan ignition delay in the engine. This delaycauses starting difficulties and engine knock.Ignition delay also causes poor fuel economy,a loss of power and sometimes enginedamage. A low cetane number fuel can alsocause white smoke and odor at start-up oncolder days. Engines running on fuels withlow cetane numbers may need to be startedand stopped using a good distillate fuel.

Blended fuels or additives can change thecetane number. The cetane number is difficultand expensive to establish for blended fuelsdue to the complexity of the required test.

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White exhaust smoke is made up of fuelvapors and aldehydes created by incompleteengine combustion. Ignition delay during coldweather is often the cause. There is notenough heat in the combustion chamber toignite the fuel. Therefore, the fuel does notburn completely.

Using a cetane improver additive can oftenreduce white smoke during engine start-up incold weather. It increases the cetane numberof diesel fuel which improves ignition qualityand makes it easier for fuel to ignite and burn.Contact your local fuel supplier forinformation on where to obtain cetaneimprovers.

The cetane number sensitivity can also bereduced in an engine by raising the inlet airtemperature, if practical.

Cetane number is usually calculated orapproximated using a cetane index due to thecost of more accurate testing. Be cautiouswhen obtaining cetane numbers from fuelsuppliers.

Flash PointThe flash point is the temperature at whichfuel vapors can be ignited when exposed to aflame. It is determined by the type of fuel andthe air-fuel ratio. It is important for safetyreasons, not for engine operatingcharacteristics.

The minimum flash point for most diesel fuelsis about 38°C (100°F).

WARNING! For safety, maintain storage,settling and service fuel tanks at least 10°C(18°F) below the flash point of the fuel. Knowthe flash point of the fuel for safe storage andhandling, especially if you are working withheavy fuels that need heating to a highertemperature to flow readily.

Cloud PointThe cloud point of a fuel is that temperatureat which a cloud or haze appears in the fuel.This appearance is caused by the temperaturefalling below the melting point of waxes orparaffins that occur naturally in petroleumproducts.

Engine EffectsThe cloud point of the fuel must be at least6°C (10°F) below the lowest outside(ambient) temperature to prevent filters fromplugging.

The fuel’s cloud and pour points aredetermined by the refiner. Generally, thecloud point is most important to you since it isat this temperature that fuel filter pluggingbegins to occur and stops fuel flow to theengine.

Steps to Overcome a High CloudPoint TemperatureThree steps can be taken to cope with highcloud point fuels.

1. Use a fuel heater when the outsidetemperature is below the cloud point ofthe fuel. Since the cloud point is also thewax melting point, when your fueltemperature is maintained above thecloud point, the wax will remain melted inthe fuel. The heater should warm the fuelbefore it flows through the filter(s). Fuelheaters often use the engine coolant toheat the fuel and prevent wax particlesfrom forming. Make sure the heater iscapable of handling the maximum fuelflow of the engine. When the ambienttemperature is low enough to require theuse of a fuel heater, start and run theengine at low idle until the fueltemperature is high enough to preventwax formation in the engine fuel filtercircuit. Otherwise, high fuel rates withcold fuel will increase the risk of plugging.

Note: Do not allow the fuel to get too warmbecause fuel above 29°C (85°F) will affect thepower output of the engine. Never exceed66°C (150°F) with straight distillate fuel. Thehigh fuel temperatures also affect the fuel

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viscosity. When the fuel viscosity falls below1.4 cSt, pump damage may occur.

2. You can also dilute high cloud point fuelswith a low cloud point fuel like kerosene.

3. The fuel manufacturer can also add flowimprovers (wax crystal modifiers) to thefuel. These do not change the cloud pointof the fuel, but they do keep the waxcrystals small enough to pass through thefuel filter.

Caterpillar does not recommend the use ofaftermarket fuel flow improvers because ofoccasional compatibility problems.

Pour PointThe pour point of a fuel is that temperaturewhich is 3°C (5°F) above the temperature atwhich the fuel just fails to flow or turns solid.Usually the pour point is also determined bythe wax or paraffin content of the fuel.

Steps to Overcome a High Pour PointTemperatureThe pour point can be improved with flowimprovers or the addition of kerosene. Fuelheaters cannot normally solve problemsrelated to a high pour point temperature.

ViscosityViscosity is a measure of a liquid’s resistanceto flow. High viscosity means the fuel is thickand does not flow as easily. Fuel with thewrong viscosity (either too high or too low)can cause engine damage.

When comparing viscosity measurements, besure they are taken at the same fueltemperature. Caterpillar recommends aviscosity between 1.4 cSt and 20 cSt deliveredto the fuel injection pump. Engines with unitinjectors can expect a 20°C (68°F)temperature rise between the transfer pumpand the injector.

Engine EffectsHigh viscosity fuel will increase gear train,cam and follower wear on the fuel pumpassembly because of the higher injectionpressure. Fuel atomizes less efficiently andthe engine will be more difficult to start.

Low viscosity fuel may not provide adequatelubrication to plungers, barrels, and injectors;its use should be evaluated carefully.

Steps to Correct Viscosity Problems:The viscosity of fuel will vary with the fueltemperature.

Heating or cooling can be used to adjustviscosity somewhat.

Blending fuels is another way to adjustviscosity.

Viscosity and Heavy FuelThe Caterpillar 3500 and 3600 Families ofEngines can run on a blend of heavy anddistillate fuels. Viscosity is a key factor. Heavyfuel must be diluted or heated until it reachesa viscosity of 20 cSt or less before it reachesthe fuel system. Unless the engine hasextremely low rpm, there is little economicbenefit to trying to treat fuel with a higherviscosity than 380 cSt.

Steps to Correct Viscosity ProblemsTo handle high viscosity fuel, some additionalinstallation requirements may be needed,depending on the exact viscosity. Theinstallation may require:

• Fuel tank and fuel line heating.• Centrifuging and back flush filtering.• Externally driven fuel transfer pumps.• Additional fuel filtering.• Washing of the turbocharger exhaust

turbine. (3600 Family Engines)

Specific GravityThe specific gravity of diesel fuel is the weightof a fixed volume of fuel compared to theweight of the same volume of water (at thesame temperature). The higher the specificgravity, the heavier the fuel. Heavier fuelshave more energy or power (per volume) forthe engine to use.

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Effects on Engine

Light FuelsWhen comparing fuel consumption or engineperformance, always know the temperature ofthe fuel measurement for correct gravity anddensity.

• Lighter fuels like kerosene will not producerated power.

• Do not adjust engine fuel settings tocompensate for a power loss with lighterfuels (with a density number higher than35 API). There is a likelihood of inaccuracyin the compensation process (if not done byauthorized personnel) and the service lifeof a compensated engine might beseriously reduced if occasionally subjectedto denser fuel.

• Fuel system component life can bedecreased with very light fuels becauselubrication will be less effective (due to lowviscosity). Lighter fuels may also be a blendof ethanol or methanol with diesel fuel.Blending of alcohol (ethanol or methanol)or gasoline into a diesel fuel will create anexplosive atmosphere in the fuel tank. Inaddition, water condensation in the tankcan cause the alcohol to separate andstratify in the tank. Caterpillar recommendsagainst such blends.

Heavy FuelsA heavy fuel tends to create more combustionchamber deposit formations which can causeabnormal cylinder liner and ring wear.

Correct Specific Gravity

• Blending is the only way to correct fueldensity problems.

ContaminantsSulfurSulfur, in diesel fuel, is converted to sulfurtrioxide during combustion. Sulfur trioxidewill exhaust from the engine (without causingserious problems for the engine), as long as itdoes not come in contact with liquid water. Ifthe sulfur trioxide gas does contact liquidwater, the result is H2SO4 or sulfuric acid; ahighly corrosive compound which will causesevere engine damage.

Engines should maintain jacket watertemperatures above 74°C (165°F) at all timesto minimize internal condensation of watervapor (from combustion).

Fuels containing higher sulfur levels can beutilized in Caterpillar Marine Engines. Thisdoes require proper lubrication oil selection.Consult the appropriate lubrication andmaintenance manual, published by theCaterpillar Service Department, for specificrecommendations.

Maintain the crankcase breather system toprevent condensation in the crankcase oilwhich will cause rapid TBN depletion.

Maintain a regular Scheduled Oil Sampling(S•O•S) oil analysis program. Infrared (JR)analysis is valuable as well.

Follow standard oil change intervals unlessS•O•S or known sulfur content indicatesdifferently.

Caterpillar Fuel Sulfur AnalyzerThe Caterpillar 8T0910 Fuel Sulfur Analyzerwill allow the vessel operator to immediatelyanalyze fuel containing up to 1.5% sulfur.Caterpillar recommends checking each bulkfuel delivery, especially if fuel quality isquestionable.

VanadiumVanadium is a metal present in some heavyfuels. It is impractical to remove or reducethis element at the refinery.

Vanadium compounds accelerate depositformation.

Vanadium is not present in distillate fuels.

Engine EffectsVanadium in the fuel quickly corrodes hotcomponents. It will often first appear in theform of molten slag on exhaust valve seats.

Vanadium forms highly corrosive compoundsduring combustion. These compounds attachto hot metal surfaces, like exhaust valve faces,injector tips and turbocharger blades.Vanadium compounds melt and remove theoxide coating. When component temperaturesrise, vanadium corrodes even faster. Forexample, exhaust valves can wear out in a few

20

hundred hours when vanadium content in afuel is high.

Steps to Help Prevent VanadiumCorrosion DamageVanadium compounds must reach theirmelting point to become active. The bestcorrosion control is to limit exhaust systemcomponent temperatures by controlling thetemperature of the exhaust gas. Coolerexhaust gas temperatures can allow an engineto tolerate more vanadium in the fuel.

Some of the measures utilized to deal withhigh vanadium fuels include:

• Using special heat resistance materials.• Rotating exhaust valves (standard on

Caterpillar Engines).• Engine derating to lower exhaust

temperatures.• Special cooling of high temperature parts.• Blending the fuel with low vanadium fuel

will reduce effects.

WaterWater can be introduced into the fuel duringshipment or as a result of condensationduring storage.

Engine EffectsWater (both fresh and salt) can cause:

• Excessive separator sludge after the fuelhas been centrifuged.

• Piston ring groove deposits.• Wear in fuel system plunger and barrel

assemblies.• Power loss from fuel starvation; the water

causes fuel filter media to swell, cutting offthe engine’s fuel supply.

Steps to Overcome Effects of Water• The effects of water in fuel can be

minimized by draining water from the fueltank daily.

• Obtaining fuel from reliable sources.• Removal of salt water may require

centrifuges.

Water SeparatorsThere are two types of water separators.

Sediment-Type Water SeparatorThe sediment type is installed ahead of theengine’s fuel transfer pump. For water andsediment to separate properly, the sediment-type water separator should not be subject toviolent motion.

A sediment water separator does not have afiltering media in the element. It does notnormally need scheduled elementreplacement.

The water and sediment trap should be largeenough to reduce the fuel flow rate to avelocity less than 0.61 m/s (2 ft/s). The largerparticles of sediment and water will settle outat this flow rate.

Locate the water and sediment trap as close tothe fuel tank as possible. This is to minimizethe length of ship’s fuel lines which aresubject to water and sediment contamination.It will minimize any problem with waterfreezing in fuel lines.

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Coalescing Water SeparatorThe coalescing type of separator must beused if the water in the fuel is broken intosuch small particles that they make the fuelcloudy.

A coalescing-type separator will separate allwater from fuel. It can be put anywhere in thefuel line, such as next to the components thatneed the most protection from water. Theelements are composed of two-stage papermedia that are replaceable. You can tell theelement is plugged when there is a lack offuel pressure.

Catalytic FinesCatalytic Fines are small, hard particles whichoriginate at the refinery. They are usuallycomposed of aluminum and silicon particlesand can cause very rapid abrasive wear.

Engine EffectsCatalytic Fines will severely damage injectionpumps, injectors, piston rings and cylinderliners.

Proper fuel treatment methods (centrifugingand filtration) will remove these particles.

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2

SUGGESTED ARRANGEMENT FOR WATER AND SEDIMENT TRAP

1. Fuel inlet2. Inlet baffle3. Hand hole and cover4. Fuel Outlet5. Baffles6. Openings at bottom of baffles for drainage7. Drain Opening8. Air bleed plug

SedimentTrap Capacity

Note: Suggested minimum size of trap

Fuel Cons. Tank Cap. 25 5000

= +

Figure 2.3

Volatile Fuel ComponentsCertain liquids are present in fuels in a vaporor gaseous state. This can cause aninterruption of fuel supply to the fuel pump.

Lighter fuels and crude oils will have greatertendency to this problem than heavier fuels.

An air eliminator, or vapor trap, can be usedto minimize the effect of interrupted fuelsupply due to vapor lock.

The vapors and gases, thus separated arecombustible and must be disposed ofaccording to safe venting practice.

Simple venting to atmosphere is not adequate,since some of the vapors and gases may beheavier than air and tend to collect or pool inlow spots, forming a severe safety hazard.

AsphaltenesAsphaltenes are components of asphalt thatare insoluble in petroleum naphtha and hotheptanes but are soluble in carbon disulphideand benzene. They are hard and brittle andare made up of long molecules with highmolecular weight. In high concentrations,asphaltenes can cause filter plugging. Theyoften contain heavy metals such as nickel,iron and vanadium. Asphaltenes are notpresent in distillate fuels.

Microorganisms in FuelAll water and fuel offer a medium formicroorganism growth. These simple lifeforms live in the water and feed on fuel.

Engine EffectsMicroorganisms in fuel cause corrosion andfilter plugging. They may be any color but areusually black, green or brown. They grow inlong strings and have a slimy appearance. Abiocide added to the fuel will kill themicroorganisms but will not remove theremains of their bodies. Extensive filtering ofthe fuel after using the biocide is required toeliminate engine-mounted filter plugging.

Steps to minimize problems withbacterial growth:• Avoid long fuel storage periods.• Drain water from fuel tanks daily.• Purchase fuel from reliable sources.

• Dose all fuel inventory with biocide at thefirst sign of microorganism contamination.

AirAir can be dissolved in fuel, and it can also bepulled into the fuel lines by a leak on thesuction side of the fuel transfer pump.

Engine EffectsAir in the fuel will cause starting problems,missing, low power and smoke problems. Aircan also cause excessive white smoke in someengines.

Reducing the effects of air in the fuelsystem.Remove air by bleeding the fuel system.Check for dissolved air in fuel with a 2P8278Fuel Flow Tube. Correct suction piping leaks.

FiltersPrimary Fuel Filter ElementSpecificationThe primary fuel filters elements should havethe following properties:Mesh Size— 32 x 28 strands per cm

(70 x 80 strands per in.)Element— Monel wire cloth material

or equivalentElement Area— 645 cm2 (100 in.2 ) or

greaterOpening Size— 0.1778 mm x 0.2235 mm

(0.007 in. x 0.0088 in.)

Duplex Fuel FiltersMany Caterpillar Engines can be equippedwith duplex fuel filters. These filters may beserviced (change elements), without shuttingoff the engine. There are two types: thesymmetrical type—which has two identicalfilter sets and the main-auxiliary type—whichhas a main filter set and a smaller capacityauxiliary filter set. A special valve connectsthe two sets of filters in each type. The valveroutes the fuel to be filtered through either orboth sets of filters.

Both filter sets can be used simultaneously toextend running time in an emergency.

23

Filter Micron RatingsCaterpillar does not specify filter or filterpaper by micron rating.

Caterpillar specifies actual filter capability,rupture strength, the capacity for holding dirt,flow resistance, filter area, etc.

Micron ratings are easily confused for thefollowing reasons:

• The test for micron ratings is notrepeatable at different labs. Onemanufacturer may give a rating of 10 microns (0.00039 in.), another at2 microns (0.000079 in.), and a third mayrate a particular filter media (paper) at 15 microns (0.00059 in.).

• There is no consistent relationship betweenmicron rating and actual filtrationefficiency. The entire filter needs to betested, not just the media (paper).

• The micron rating does not show whathappens to a filter over time. The testprovides no information about how a filterwill stand up under continual use.

Micron ratings are overemphasized; a 10 micron filter will not always stop a 10 micron particle. Many reputable filtermanufacturing firms are drifting away frommicron ratings to more conclusive tests.

Smaller micron ratings are not necessarilybetter.

If all other factors (area) were equal, a smallermicron number media (paper) has a severedrawback: less capacity before plugging,needs to be replaced more often. The size ofthe pores in the paper needs to be balancedagainst the costs of the filter replacement.

Common questions are:

• What is the maximum particle size whichcan pass through Caterpillar filters?

• What is the difference between nominalsize and absolute size filters?

For example: A nominal 10 micron filtermedia (paper) will pass some particles up toabout 50 microns in size. Theoretically, an

absolute rating of 10 microns will stop allparticles larger than 10 microns. In fact, filterswith absolute micron ratings of 10 will passsome particles larger than 10 microns due tothe irregularity of the paper weave. Newfilters may pass larger particles than they willafter only a few hours of use.

As a general rule, Caterpillar fuel filter media(paper) is about 3 microns nominal,20 microns absolute. Oil filter media (paper)is about 10 microns nominal, 50 micronsabsolute. These are approximate values only.

Filters are not effectively compared on thebasis of micron rating alone. Evaluate filterson the basis of their ability to collect foreignmaterial as a whole.

Fuel System —MiscellaneousDisposal of Used Lube OilIt is necessary to collect, store, and dispose ofused crankcase oil from engines correctly. Itis not acceptable to dump used crankcase oilinto the oceans, rivers and harbors fromvessels or offshore drilling and productionplatform installations. It may be necessary forengine operators to consider burningcrankcase oil in their Cat Engines. This canbe done, providing the precautions below arecarefully followed:

• Only diesel engine crankcase oils can bemixed with the diesel engine fuel supply.The ratio of used oil to fuel must notexceed 5%. Premature filter plugging willoccur at higher ratios. Under nocircumstances should gasoline enginecrankcase oil, transmission oils, hydraulicoils, grease, cleaning solvents, etc., bemixed with the diesel fuel. Also, do not usecrankcase oils containing water orantifreeze.

• Adequate mixing is essential. Lube oil andfuel oil, once mixed, will combine and notseparate. Mix used filtered crankcase oil withan equal amount of fuel, then add the 50-50blend to the supply tank before new fuel isadded (maintaining the 5% used oil to fuelratio). This procedure should normally

24

provide sufficient mixing. Failure to achieveadequate mixing will result in prematurefilter plugging by slugs of undiluted oil.

• Filter or centrifuge used oil before puttingit in the fuel tanks to prevent prematurefuel filter plugging, accelerated wear orplugging of fuel system parts. Soot, dirt,metal and residue particles larger than 5 microns (0.000197 in.) should beremoved by this process.

If filtering or centrifuging is not usedbefore adding the oil to the fuel, primaryfilters with 5 microns (0.000197 in.)capability must be located between the fuelsupply and engine. These will requirefrequent servicing.

• Clean handling techniques of the usedcrankcase oils are essential to preventintroducing contaminants from outsidesources into the diesel fuel supply. Caremust be taken in collecting, storing andtransporting the used crankcase oil to thediesel fuel tanks.

Diesel fuel day tank sight glasses maybecome blackened in time due to thecarbon content in the crankcase oil. Ashcontent of the lube oil added to the fuelmay also cause accumulation ofturbocharger and valve deposits morerapidly than normal.

CorrosionCopper Strip CorrosionCorrosion is commonly tested by examiningthe discoloration formed on a polished copperstrip when immersed in fuel for three hours at100°C (212°F). Any fuel showing more thanslight discoloration should be rejected.

Many types of engine parts are of copper orcopper alloys. It is essential that any fuel incontact with these parts be noncorrosive tocopper. There are certain sulfur derivatives inthe fuel that are likely sources of corrosion.

Sodium or Sodium Chloride (Salt)Sodium is an alkaline, metallic element. It isvery active chemically. Sodium’s mostcommon form is table salt.

Sodium is frequently introduced duringstorage or because of incorrect handlingprocedures. Sodium can come directly fromsea water or salt air condensation in fueltanks. It can also be present in crude oil in itsnatural state.

Engine EffectsSodium acts as a catalyst for vanadiumcorrosion. When sodium and vanadiumcombine, they react to form compoundswhich melt within normal engine operatingtemperatures.

The sodium/vanadium combination causeshigh temperature corrosion of exhaust valves.It can also cause turbocharger turbine andnozzle deposits.

Steps to Reduce the Effects ofSodiumFuel can be blended to reduce theconcentration of sodium.

Fuel contaminated with sodium can be washedby blending fresh water with thecontaminated fuel in one centrifuge andseparating the two (with the sodium nowdissolved in the added fresh water) in asecond centrifuge.

Handle and store fuel in a manner whichminimizes the exposure to salt water and saltwater laden air.

Crude OilsDescriptionCrude oil is used to describe unrefinedoils/fuels. Crude oil is basically the same as itwas when pumped from the ground. Certaintypes of crude oils can be burned inCaterpillar Engines. See the Crude Oil Chart(Limits of Acceptability for Use in CaterpillarEngines) in the Fuel Section Appendix.

Heavy/Blended/Residual FuelsDescriptionHeavy/Blended/Residual Fuel is composed ofthe remaining elements from crude oil afterthe oil has been refined into diesel fuel,gasoline or lubricating oils, etc. After themore desirable products have been refined,the remaining elements (which resemble tar

25

and contain abrasive and corrosivesubstances) can be combined or diluted witha lighter fuel (cutter stock) so they can flow.These are called blended, heavy or residualfuels.

Caterpillar 3500 and 3600 Family Engines canbe modified to run on fuels which meet thespecifications in the Heavy/Blended/Residual Fuel Chart in the Fuel SectionAppendix.

Caterpillar 3500 and 3600 Diesel Engines canatomize many heavy fuels because of the unitinjector fuel system. This system does nothave high pressure fuel lines and canwithstand higher injection pressures. 3500Family Engines are capable of operating onblended fuels up to 180 cSt at 50°C at 1800 rpm and lower, usually without changingengine timing. However, engine aerating maybe required to keep the exhaust temperaturebelow maximum limits. 3600 Family Enginesare capable of operating on blended fuels upto 380 cSt at 50°C.

There are many other considerations to keepin mind when making the decision to switchto heavy fuel. Because heavy fuel is the heavyresidue which is left over from the refiningprocess, it has concentrated contaminants. Inthe best situation, using heavy fuel willincrease the workload of the operatingpersonnel. In the worst situation, heavy fuelcould cause extremely short engine andcomponent life. For your engine to operatesuccessfully on heavy fuels, you must have athorough maintenance program and highquality fuel treatment equipment.

It is recommended that you always consultwith your local Caterpillar Dealer whenconsidering fuel changes.

The Economics of Using Heavy FuelLower fuel costs make heavy fuel appear to bemore economical. Blended fuels can lowercosts for some customers, but there are oftensignificant tradeoffs. Fuel price must becompared to fuel contaminants, effects ofreduced engine component life, highermaintenance and personnel costs. Conduct athorough analysis of all the costs involvedbefore you decide to use heavy fuel.

Caterpillar or your Caterpillar Dealer will aidyou in this evaluation.

Also, investigate other fuel-saving methods.The following is a list of some fuel-savingalternatives:

• More modern, fuel-efficient engines.• Lower speed (Engines can operate at

1200 rpm instead of 1800 rpm; 1000 rpm,instead of 1500 rpm; etc.).

• More efficient propeller (larger diameterwith reduced pitch) or more efficientgenerator or other driven unit.

• Waste heat recovery.• Lighter blends.• Crude oil instead of diesel fuel.

Installation Costs Associated WithUsing Heavy FuelInstallation costs for an engine using heavyfuel may range from 25-85% more than anengine using No. 2 diesel fuel or marinediesel fuel. Other costs result from the needfor fuel treatment equipment.

Downtime is also typically increased.Operators must spend more time taking careof engine and fuel handling equipment. Theymust understand the system and havetraining on the engine as well as on the actualfuel preparation equipment.

How Your Caterpillar WarrantyApplies to Using Heavy FuelWhen you decide to use heavy fuel, you aremaking an economic tradeoff. Though yourfuel costs may be 5-40% lower when usingblended fuels, this savings does not comefree. Because of contaminants, fuel injector,valve and piston ring life could be significantlyshorter. These worn components may have tobe replaced during the warranty period, butthey are not covered by Caterpillar.

Caterpillar does not offer a warranty onreplacement of parts which have a shortenedservice life because of the use of heavy fuel.The Caterpillar warranty which applies toyour engine is available from your dealer.

Fuel BlendingMany fuel characteristics can be tailored byblending different fuels. A blended fuel can

26

help improve engine starting and warm-up,reduce deposits and wear, improve emissionsand sometimes have an effect on power andeconomy.

In general, lighter fuels are cleaner and helpengine starting. Heavier fuels have higherheating values (per volume), better cetanequality, etc.

The 3600 and 3500 Family Engines can useblended fuel economically as long as the fueltreatment facilities are adequate, and thereare trained personnel to run this equipment.

Blended Fuel Should Be AnalyzedChemical labs can evaluate fuel properties.Some oil companies and regulating agenciesalso provide fuel analysis services.

Fuel System MaintenanceFilter MaintenanceFirst clean around the filter housing, thenunscrew or otherwise remove the old filter(s)without introducing dirt into the housing.

Lubricate and clean the new filter gasket withclean diesel fuel.

Install the new filters dry.

Prime the fuel system.

Never pour fuel into the new filter elementbefore you install it. Contaminated fuel willcause fuel system damage.

Always bleed the fuel system to remove airbubbles after changing the fuel filters andbefore starting the engine.

Check the fuel pressure differential which canindicate a restricted or plugged fuel filter.

Inspect all new filters (especially check thethreads on spin-on filters) for debris or metalfilings. Any filings already in the filter will godirectly to the fuel pumps and injectors.

Use genuine Caterpillar fuel filters to ensurequality, consistency and cleanliness. Thereare great differences in fuel filters. Even if thefilter fits your engine, it might not be thecorrect filter. There are a lot of importantdifferences between Caterpillar filters and

nongenuine filters. For more information onfuel filter differences and considerations, seeyour Caterpillar Dealer.

Properly store new filters to prevent dust fromdirect entry into the filter before use.

Cut apart used filters after every filter change.A way to thoroughly inspect filters is to usethe 6V7905 Filter Cutting Tool to cut themapart after they have been used (every filterchange period). This will allow you to inspectinternal filter components, see contaminants,and to also compare brands of filters forquality and filtering effectiveness.

Storage Tank MaintenanceFill the fuel tank after each day of operation tominimize condensation of water. A full fueltank helps prevent condensation by drivingout moisture laden air. However, don’t fill thetank too full; if the temperature increases, thefuel will expand and may overflow.

Drain water and sediment from the fuel tankat the start of every shift or after the tank hasbeen filled and allowed to stand for 5-10minutes. Be sure to drain a cupful at the startof every shift for inspection. Drain storagetanks every week.

Install and maintain a water separator beforethe primary fuel filter.

As Needed Periodic ActivitiesTest fuel as it is delivered. Identifycontaminant levels immediately and notifyappropriate operations personnel.

Before storage, test for compatibility betweenfuel in the tanks and the fuel beingpurchased. Keep the fuel in separate tanks, ifpossible.

Use regular S•O•S oil analysis to determine ifthere are wear particles in the oil andmaintain the proper Total Base Number(TBN) level.

Request infrared analysis on used oil todetermine the effects of burning heavy fuel onthe crankcase oil.

27

Daily ActivitiesMaintain and monitor fuel treatmentequipment.

Record engine temperatures to assureadequate jacket water temperature,aftercooler temperature and air intaketemperature.

Check exhaust thermocouples and recordexhaust temperatures. Be alert for wornexhaust valves.

Note: Measure valve stem projection whennew; use a stationary point such as the valvecover gasket surface for a reference point.Record the measurements for each valve forlater follow-up measurements. If valve stemprojection moves more than 1.25 mm(0.050 in.), consider disassembly to find thereason. Another way to observe valve facewear is to measure and record changes onvalve lash over a period of time.

Fuel Publications AvailableFrom CaterpillarThe following publications are availablethrough your local Caterpillar Dealer. Some ofthe publications may have a nominal charge.Some may be revised or discontinued in thefuture. These publications should be ordereddirectly from your dealer. Your dealer canalso assist you in answering questionsconcerning available fuels in your operatingarea.

All Engine Data Sheets are included in theCaterpillar Engine Technical Manual, VolumeI, Form No. LEKQ2030.

Mixing Used Crankcase Oil With Diesel FuelLEKQ6070 (Engine Data Sheet 62.0)

Fuel Recommendations for Caterpillar DieselEngines LEKQ4219 (Engine Data Sheet 60.1)

Alcohol Fuels for Caterpillar Diesel EnginesLEKQ0287 (Engine Data Sheet 61.2)

Fuel Heaters for Cold Weather OperationLEKQ4065 (Engine Data Sheet 64.5 for No. 1and No. 2 Diesel Fuel Only)

Installation of 8N9754 Fuel Heater GroupSEHS7653-02 (Special Instruction)

Fight Fuel Sulfur, Your Diesel’s Silent EnemySEBD0598

Analyzing Fuel Nozzle and Fuel Line FailuresSEBD0639

Using Diesel Fuel Thermo-HydrometersGMGO0977 (Special Instruction)

Using 2P8278 Fuel Flow Tube to Check forEntrained Air in Diesel Fuel GMGO0825(Special Instruction)

Heavy Fuel Contaminant Levels for 3500 and3600 Engines LEKQ2314 (Engine Data Sheet61.1)

Sizing Fuel System Components for HeavyFuels LEKQ9173 (Engine Data Sheet 61.3)

Heavy Fuel Operating Procedures for 3500and 3600 Engines LEKQ1177 (Engine DataSheet 61.4)

Fuel Water Separator for Use With 3208 and3300 Engines Equipped With Sleeve MeteringFuel System LEKQ3383 (Engine Data Sheet64.1)

Fuel Conservation Practices LEKQ3106(Engine Data Sheet 60.2)

Other PublicationsABS Notes on Heavy Fuel Oil (1984)American Bureau of Shipping 45 Eisenhower Drive Paramus, NJ 07652U.S.A. Telephone: (201) 368-9100 Attention: Book Order Department

28

Appendix

29

Table of Specific Gravity Versus Density

Gravity Density

Degrees API@ 15°C (60°F)

Specific Gravity@ 15°C (60°F) kg/L lb/gal

25262728293031323334353637383940414243444546474849

.9042

.8984

.8927

.8871

.8816

.8762

.8708

.8654

.8602

.8550

.8498

.8448

.8398

.8348

.8299

.8251

.8203

.8155

.8109

.8063

.8017

.7972

.7927

.7883

.7839

.902

.897

.891

.886

.880

.874

.869

.864

.858

.853

.848

.843

.838

.833

.828

.823

.819

.814

.809

.804

.800

.795

.791

.787

.782

7.5927.4817.4347.3877.3417.2967.2517.2067.1637.1197.0767.0346.9936.9516.9106.8706.8306.7906.7526.7136.6756.6376.6006.5636.526

30

Crude Oil Chart

Fuel Properties and Characteristics Permissible Fuels as Delivered to the Fuel System

Cetane number or cetane index Minimum 35(ASTM D613 or calculated index)(PC Engines)

(DI Engines) Minimum 40

Water and sediment % volume (ASTM D1796) Maximum .5%

Pour Point (ASTM D97) Minimum 6°C (10°F) below ambient temperature

Cloud point (ASTM D97) Not higher than ambient temperature

Sulfur (ASTM D2788 or D3605 or D1552) Maximum .5% — See page 15 to adjust oil TBNfor higher sulfur content

Viscosity at 38°C (100°F) Minimum 1.4 cSt

(ASTM D445) Maximum 20 cSt

API gravity (ASTM D287) Maximum 45Minimum 30

Specific gravity (ASTM D287) Minimum .8017Maximum .875

Gasoline and naphtha fraction Maximum 35%(fractions boiled off below 200°C)

Kerosene and distillate fraction (fractions boiled off Minimum 30%between 200°C and cracking point)

Carbon residue (ramsbottom) (ASTM D524) Maximum 3.5%

Distillation — 10% Maximum 282°C (540°F)

— 90% Maximum 380°C (716°F)

— cracking % Minimum 60%

— residue (ASTM D86, D158 or D285) Maximum 10%

Reid vapor pressure (ASTM D323) Maximum 20 psi (kPa)

Salt (ASTM D3230) Maximum 100 lb/1,000 barrels

Gums and Resins (ASTM D381) Maximum 10 mg/100 mL

Copper strip corrosion 3 hrs @ 100°C (ASTM D130) Maximum No. 3

Flashpoint °C°F (ASTM D93) Maximum Must be legal limit

Ash % wieght (ASTM D482) Maximum .1%

Aromatics % (ASTM D1319) Maximum 35%

Vanadium PPM (ASTM D2788 or D3605) Maximum 4 PPM

Sodium PPM(ASTM D2788 or D3605) Maximum 10 PPM

Nickel PPM (ASTM D2788 or D3605) Maximum 1 PPM

Aluminum PPM (ASTM D2788 or D3605) Maximum 1 PPM

Silicon (ASTM D2788 or D3605) Maximum 1 PPM

PPM = parts per million

31

Heavy/Blended/Residual Fuel Chart

Fuel Properties and Characteristics Permissible Fuels as Delivered to the Fuel System

Water and sediment percent volume (ASTM D1796) Maximum 3500 3600

.5 .5

Sulfur (ASTM D2788 or D3605 or D1552) Maximum 4% 5%

Viscosity Minimum 1.4 cSt 1.4 cSt

(To the Unit Injector)(ASTM D445) Maximum 180 cSt @ 50°C 380 cSt @ 50°C

Carbon Residue (Conradson Carbon Residue) Maximum 15 18(ASTM D189)

Vanadium Maximum 250 300(PPM)

Aluminum (ASTM D2788 or D3605) Maximum 1 2(PPM)

Silicon (ASTM D2788 or D3605) Maximum 1 2(PPM)

PPM = parts per million

Heavy/Blended/Residual Fuel Viscosity Chart

Viscosity (cSt @ 50°C) Viscosity (Redwood Seconds @ 100°F)

30 20040 27860 43980 610100 780120 950150 1250180 1500240 2400280 2500


● Dredge Engines


Dredge EnginesDefinitionsPump Engine ConsiderationsEngine Installation

Basically, dredging is the removal of materialfrom under water, and its disposal elsewhere.It includes two distinct operations: first,excavating the material, and second,transporting it to a disposal area. There aretwo ways of doing this— mechanically andhydraulically.

DefinitionsMechanical DredgesMechanical dredges were the first to bedeveloped. Today three basic types are used:1. Grapple Dredge2. Dipper Dredge3. Bucket Dredge

The Grapple DredgeThe grapple dredge is essentially a derrickmounted on a barge and equipped with aclamshell bucket for dredging. It is mostsuitable for excavating soft and cohesivematerials.

This type of dredge does not give the bestresults in very soft deposits where thematerial is likely to be washed out of thebucket or in very hard materials where thepenetration is not sufficient to fill the bucket.Grapple dredges have the advantage of beingable to work in confined areas near docks andbreakwaters.

The Dipper DredgeThe dipper dredge is essentially a barge-mounted power shovel. Its main advantage isin the strong crowding action of the bucket asthe dipper stick forces it into the material tobe moved. Its best use today is for excavatinghard compact materials, rock and other solidformations after blasting. For its size, a dipperdredge can handle larger pieces, thusreducing the amount of blasting. For mostother work it has been replaced by moreefficient, faster working hydraulic dredges.

1

Spud Boom

Bucket

Figure 1.1

The Bucket DredgeThe bucket dredge consists of an endlesschain of buckets moving from the work faceto a point above the surface of the water. Eachbucket digs its own load, carries it to thesurface and, as it rotates over the top tumbler,dumps its load and goes back for another.Bucket dredges are more efficient than dipperor grapple dredges because the work cycle iscontinuous. Dredges of this type have foundwide use in commercial production of sandand gravel and in the the recovery of variousores and precious metals such as tin and gold.

All three types of mechanical dredges havetheir advantages; however, each fulfills onlyone part of the two-phase dredging operationof excavation and disposal. Mechanicaldredges remove material, but to disposerequires a fleet of barges and tugs to movethe material to its disposal point. Hydraulicdredges handle both phases of the dredgingprocess.

Hydraulic DredgesUnlike the mechanical dredges, hydraulicdredges use the water on which they float tomake dredging more efficient. A hydraulicdredge mixes the material to be removed withwater and pumps it as a fluid. Hydraulicdredges are usually more versatile, efficientand economical to operate than mechanicaldredges because the digging and disposingoperation is performed by one self- containedunit.

The Plain Suction DredgeThe plain suction dredge consists of a dredgepump which draws in a mixture of water andexcavated material through the suction pipelowered to the working face of the deposit.The mixture is discharged through a pipelineto the spoil area or into barges or hoppers.The use of units of this type is limited todigging soft and free-flowing materials, suchas clay, sand, silt, or gravel.

2

Spud

Bucket

Boom

Dipper Stick

Figure 1.2

Spud Bucket Ladder

Figure 1.3

As a further development, dredges of this typeare sometimes equipped with a special suctionhead, using water jets or other devices toagitate the material. One particular adaptationof this principle is the Dustpan dredge, sonamed because of the shape of the suctionhead. Units of this type are used extensivelyon large rivers where accumulated materialsmust be rapidly removed from the navigationchannel.

The Self-Propelled HopperDredgeResembling an oceangoing ship, the self-propelled hopper dredge functions in a similarmanner to the plain suction dredge. Inoperation, as the suction pipe or pipes aredragged along the bottom while the dredge ismoving ahead at a slow speed, a mixture ofwater material is picked up and conveyed to

the pump or pumps installed on the dredge.The discharge pipes are connected to thedredge pump or pumps to carry the materialsto the hoppers which are built into the hull.When the hoppers are filled, the dredgeproceeds at full speed to the dumpinggrounds in deep water. Here, the hopperdoors built in the bottom of the hull areopened and the material dumped. The dredgethen returns to the site of work and repeatsthe cycle.

Dredges of this type are necessary formaintenance work and improvement inexposed harbor entrances where traffic andoperating conditions will not permit use ofstationary dredges. These dredges have beenbuilt with hopper capacities ranging up to6116 m3 (8,000 yd.3).

3

Pump

Suction Pipe

Discharge Pipe

Figure 1.4

Hoppers

Pump

PropellerSuction Pipe

Figure 1.5

The Cutterhead Pipeline DredgeThe cutterhead pipeline dredge is the mostversatile and widely used marine excavatingunit. It is similar to the plain suction dredge,but is equipped with a rotating cuttersurrounding the intake end of the suctionpipe. This cutter loosens the material which isthen sucked in through the dredging pump,delivered to the stern of the dredge andconveyed to the disposal area by means of apipeline. Hydraulic pipeline dredges canefficiently dig and pump loose materials as

well as compacted deposits such as clay andhard pan. The larger and more powerfulmachines are used to dredge rocklikeformations, such as coral and softer types ofbasalt and limestone, without blasting.

The cutterhead pipeline dredge, like severalother types, is held in working position byspuds and advances by walking itself on thesespuds. The advantages of the cutterheadpipeline dredge are its versatility and nearlycontinuous operating cycle, resulting inmaximum economy and efficiency.

4

WinchPump

Spud Frame

Discharge Pipe

Cutterhead Ladder Spud

Figure 1.6

Figure 1.7

Spud LiftersSpuds-Stowed Position

Pump Clean-Out Opening

SpudsWinches Pump Suction Line

Cutter Head

Dredge NomenclatureCutterhead—A rotating toothed auger fordislodging material. The cutterhead containsthe pump suction inlet. The cutterhead isusually driven by a separate diesel enginethrough hydraulic motors, electric motors, ora shafting drive line. Winches and spud liftersmay also be driven by this engine.

Ladder—A horizontally hinged boom,rigidly constructed, which provides structuralsupport for the cutterhead, the cutterheaddriving mechanism, and the dredge pumpsuction line. It is hinged to the front of thedredge and may be lifted or lowered tocontrol digging depth.

Main or Center Hull—A rectangular-shaped hull which contains the dredge pumpand its associated reduction gearing, clutches,engine(s), and controls. Mounted on thecenter hull is the control station, swing andladder winches, spuds, hydraulic drive engine,and the dredge’s service power generationmachinery.

Spuds—The dredge is equipped with two,long, tubular, sharp pointed poles, verticallymounted on the rear of the dredge. Thesespuds are raised and alternately lowered intothe bottom material. The spuds provide pivotpoints around which the dredge may swing asthe cutterhead advances into the bottommaterials.

Pontoons—The pontoons are longer thanthe center hull and are mounted on eitherside. They provide flotation stability and fueland water storage capacity.

Pump EngineConsiderationsHorsepower (Engine Load)Versus Discharge Line LengthA common misunderstanding is that morehorsepower is required to pump against along distance line than a short one. Thehorsepower requirement of a pump isproportional to the gallons per minute (gpm)being pumped. The longer the discharge line,the greater the resistance to flow, therefore,the fewer gpm and a lower horsepowerrequirement results. Conversely, as the linelength is reduced, resistance to flow isreduced, more gpm are being moved and ahigher horsepower required.

If a dredge must be operated with a dischargeline shorter than its design length, the enginerpm must be reduced. This reduces the pumprpm, causing a decrease of the horsepowerrequirement. Throttling back will relieve theengine from an overload situation and mayeven result in an increase in dredgeproduction.

5

Discharge Pipe

Pump Engine/s

Dredge PumpCenter Hull Ladder

Pontoons

Figure 1.8

Horsepower Versus SpecificGravity (Percent Solids)The heavier the material being pumped, thegreater the horsepower requirement. It takesless horsepower to pump pure water than itdoes to move a mixture of solid material andpure water. The pump horsepowerrequirement is directly proportional to thespecific gravity of the pumped fluid.

Example: If a pump engine is called on toproduce 100 hp when pumping clear water,the same pump engine must be capable ofdeveloping 150 hp while pumping the sameflow rate (gpm) of a slurry (water and solidmix) whose specific gravity is 1.5.

Horsepower Versus PumpSpeedThe load on the dredge pump engine isproportional to the cube of the pump speed.This means a small increase in pump rpm willresult in a much greater horsepower demandon the engine. For example: To double thespeed of the pump impeller would requireeight times more horsepower. Stated anotherway, a pump impeller which demands 100 hpto turn at 150 rpm will require 800 hp at300 rpm.

Engine Operation to AvoidOverloadIf dredging conditions are such that the pumpengine(s) are not able to reach rated rpmwhile at full throttle, then throttle positionmust be reduced to avoid engine overload.Reduce throttle position from full throttle—while digging—until engine speed dropsapproximately 50 rpm. This will result inapproximately the same horse power outputdelivered to the pump, but will allow theengine to deliver that horsepower safely,without overfueling.

Engine InstallationMany marine engine installation practicesapply equally to dredges. When this is thecase, the reader will be referred to theappropriate marine engine section. Only thosepractices and recommendations that areunique to the dredge application will bediscussed in this section.

Mounting and AlignmentMounting RailsAll large bore Vee-type engines should bemounted with angle section, ledge-typemarine mounting rails. Engines can besuccessfully installed using industrial channelsection mounting rails, but mountingflexibility is sacrificed. See Marine MountingRecommendations section for further detailson shimming and bolt fit.

Tandem Engine Thermal GrowthConsiderationsThe thermal expansion of engines must notbe restrained. The flywheel end of the enginemounting rails should be fixed by a groundbody, fitted bolt on either or both sides of theengine. The diameter of the mounting bolts—fixing the engine’s rails to the dredgestructure—forward of the flywheel must be1.6 mm (0.06 in.) less than the diameter of theholes in the mounting rails. This clearancewill1 allow the engine and mounting rails togrow without confinement.

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When installed properly, there is sufficientaxial clearance within the Caterpillar viscousdamped engine-to-engine coupling to allowthe engine nearest the load to grow withoutrestraint. The axial clearance dimension canbe checked on a new installation bymeasuring from the outer face of the greaseretaining plate (of the Caterpillar viscousdamped coupling) to the nearest surface ofthe coupling inner member. This dimensionshould be 8.6 ± 0.76 mm (0.34 ± 0.03 in.).

Tandem Engine TimingConsiderationsTiming Recommendations are contained onTandem Engine Coupling Arrangementdrawings. These directions must be followedto avoid possible torsional vibration problems.

Tandem Engine GovernorSettings (Low Idle rpm)Some dredge pump drive applications requirea special engine low idle setting to

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AXIALCLEARANCEDIMENSION

DRIVEN EQUIPMENTSHAFT OR HUB

COUPLING INNER MEMBER

GREASE RETAINING PLATE

RUBBER ELEMENT

CATERPILLAR VISCOUSDAMPED COUPLING

ENGINE FLYWHEEL

Figure 1.9

avoid torsional resonance. Many Caterpillarengines used in tandem service must have alow idle setting of not less than 600-650 rpm.Always check the engine data plate todetermine proper governor settings. Manydredge engine settings are special and notlisted in standard Caterpillar Serviceliterature.

Fuel Treatment and PlumbingSince dredges are normally equipped withvery large fuel tanks, condensation, fungus/bacteria growth, and contamination of the fuelmay be troublesome. Fuel systemmaintenance is especially important in dredgeapplications.

The lowest point within the dredge's fueltanks should be drained or pumped daily toeliminate condensed moisture and sediment.

Water and sediment traps should be used infuel supply lines.

Terminate engine fuel supply plumbing atleast 300 mm (12 in.) above the lowest pointin fuel tanks.

See fuel section for information on detectionand prevention of fungus/bacteria growth infuel tanks.

Exhaust, Ventilation, andCrankcase Vent SystemsAll diesel engines require large quantities ofclean, cool air for long trouble free life.

Combustion AirEquip dredge engines with combustion airinlet ducts, located and routed to preventrecirculation of exhaust gases and crankcasefumes. Locate combustion air inlets so theydo not ingest heated engine room ventilationair rising through removable roof caps.Exhaust gases must be discharged toatmosphere high enough above thecombustion air inlet openings to preventrebreathing of exhaust gases. Equip exhauststacks with joints which allow addition ofextra sections of exhaust pipe if exhaustrecirculation proves to be a problem onoperating location. An unrestricted elbow-typeexhaust discharge fitting is preferred over thecounterbalanced flapper valve because therewill be less chance for downward deflection ofexhaust gases.

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"H" Dimension Must Be Large EnoughTo Prevent ExhaustGas Recirculation

H

Crankcase VentDischarge OpeningThrough Side Of Engine CompartmentAs Far As Possible FromCombustion Air Inlet Ducts

Rain CapsFor Combustion AirInlet Ductwork

"Flapper" Type RainCaps Are DiscouragedDue To PossibilitiesOf Exhaust Recirculation

Figure 1.10

See Ventilation and Exhaust sections for flow,pressure, and temperature information.

RatingsEngines in dredge pump drive service shouldbe applied at the continuous ratings.

Engines driving electric or hydrauliccutterheads and/or winches may carry theintermittent or light duty commercial ratingsince neither cutterheads nor winches arecontinuous loads.

Engines driving generators which supplylighting and service pumping power should berated for prime power due to the continuousnature of lighting and pumping loads.

For additional explanation of Caterpillarengine rating philosophy, see Ratings section.

CoolingThe dredging application may place severedemands on the engine cooling system.

Keel Cooling ConsiderationsThe dredge is normally stationary on itsdigging location with little or no water flowingpast the hull. The efficiency of keel coolers isgreatly reduced under these conditions. Keelcoolers operating in dead water conditionsrequire more than twice the surface area thatwould be required if the cooling surface had afive knot water velocity over the outside of thecooler. See Keel Cooler Area Requirementcurves in the Marine Cooling System sectionfor added information.

Heat Exchanger CoolingUsing inboard (shell and tube-type) heatexchangers may be troublesome due to thehighly abrasive particles suspended in thewater common to dredging operations.Cooling water suction line strainers are anecessity to minimize damage to pumps andheat exchangers tubes. Use Caterpillarengine-mounted sea water pumps (particularlyrubber impeller pumps) with the knowledgethat their service life, when pumping watercontaining abrasive particles, will besignificantly shortened.

Hydraulic Dredges will have, as one of theirnormal components, a “service water” pump.This pump is usually designed for abrasivewater service. The service water pumpprovides clean sea water, at higher pressure,for lubrication and flushing of the dredgepump and cutterhead lineshaft bearings. Useof excess flow from the service water pump isa superior alternative to Caterpillar enginemounted sea water pump.

Box CoolersBox-type coolers offer many of the advantagesof keel cooling and shell and tube coolers,particularly in dredging applications.

Aftercooler CoresAlthough many dredges operate in freshwaterponds, lakes, and rivers, experience hasproven that engine aftercooler cores suitablefor sea or salt water are a necessity. Themoisture-laden air surrounding any floatingequipment will corrode the fins on the air sideof nonmarine aftercooler cores severelylimiting the heat transfer and possibly evenrestricting the combustion flow.

ControlsSingle Engine DriveDredge engine controls are the same asconventional controls for engines in otherpumping or electric power generationapplications, with the exception of tandem orcompound engines driving a single load.

Tandem/Compound Engine DriveWhen multiple engines are tandemed(nose-to-nose configuration) or compoundedside-by-side configuration with flywheeloutputs (combined in gearing or with chains),the capability to share load equally at full loadbecomes important.

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Load ShareEngines must share load equally so oneengine, the one taking most of the load, willnot wear out prematurely or fail. Theprecision of the sharing of the load is onlyimportant at or near the engines full powercapability (large fractions of the enginerating).

Hydra-Mechanical GovernorsA way to ensure load share at full load is toadjust the air actuators on Caterpillar standardhydra-mechanical governors so both enginesreach the same high idle speed (rpm) withthe same air actuator pressure. Theadjustment is normally done at the factorywhen pairs of engines are specified to be usedin tandem or compound.

Isochronous GovernorsLoad sharing is more easily attained ifgovernors capable of isochronous operationare avoided or adjusted to operate in a droop,or non-isochronous mode. Generally 5-10%droop is satisfactory.

Safety System Considerations onTandem/Compound EnginesPrelubrication SystemWire the oil pressure sensors included withprelubrication systems in series to preventeither tandem/compound engine’s crankingmotor from engaging before both engines areprelubed.

Shut-down DevicesSensors connected to automatic shut-downdevices must be interconnected ontandem/compound engines to insure bothengines shut-down in the event of amalfunction in either engine.

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marine engines application and installation guide...power is based on a 35 api [16 c (60 f)] fuel...

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