machinery reliability-heinz bloch

8/22/2019 Machinery Reliability-Heinz Bloch

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Second levelThird level

Fourth level

Fifth level


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(1) Start with cost estimates and budgets

Why Best-of-Class companies budget towards mostrel iable machinery and not towards their least

expensive initial outlay options

They start by having only the most capablevendors on their bidders (vendors) lists

Their budgets for machinery include 5% of thecost of this machinery to perform MQA

Have a contingency budget to pay forupgrades or things overlooked in the specs


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of Webinar 9, (6/20/ 2013)

Several recent texts

include descriptionsof MQA

The smartest budgets

include 5% or more forperforming MachineryQuality Assessment(MQA);often a one-year payback

Next slide: Pre-invest!


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MQA Example: Nozzle size increases for

D$ ~ 4 to 6 k--low gas velocity The benefits of soundly

done pre-investment in

contingency upgrades(as successfully done by

Dakota Gasification;

briefly discuss example)

Examples of large gearbox and compressor

nozzle sizing upgrades


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(2) Decisions with Reliability Impact for

Reciprocating Compressors: Or,

small matters add up

Suction valves were not automatically opened whenpower was interrupted--bearing bores then contact their

pins or journals Grout support under compressor frame had been allowed

to degrade over time--generally no issue, but crankshaftis then slightly curved

Bearing bores then experienced edge loading With no power to compressor driver, there was no lube

oil supply to bearings, hence no cooling; some melting


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Edge loading means reduced areas of

contact;pressure = force per unit area (psi) Crank pin

Crosshead pin

Main journal______________

The loads (arrows) actonly on a smallarea, psi. Now the

pressure becomestoo high; no oilfilm; high temperat.,softening of alloy(babbitt) takes

place; bearing fails

1


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Edge-loading of bowed crankshaft wrecks a bearing Theowner plant allowed four deviations to become new normal: curvature

of crankshaft, high force on bearing, no cooling oil

2


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Real pros always look at the entire system: Example ofKing Tool

conventional horizontal filter-coalescer vs. self-cleaning models


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Why reciprocating compressor moisture

disengagement strategies are often flawed

Example of a reciprocating machine having an

inlet capacity of 1000 volume units (cubic feet per

minute, or cubic meters per hour)

Volume = Area times velocity [cfm=sq ft x ft/min]

Volume = Area times velocity [m^3/hr = m^2 x m/hr]

1000=10 x 100----- small area x high velocity ($)

1000=100 x 10----- large area x low velocity ($$$)


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(3)The merits of superior machinery storagepreservation (cost justification is not difficult)


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Cost justification for OM storage protection

System cost: ~$300,000 Without oil mist outdoor storage protection, must

dismantle and inspect/clean 120 process pumps($10,000 each) = $1,200,000 and electricmotors ($3,000 ea) = $ 360,000

Total cost avoidance is $1,560,000-$300,000 =

$1,260,000. Operating cost of the OM storagesetup is offset by credits for future use as unit-wide oil mist lubrication system


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(4+5) Examples of knowledge requirements:

Lube and bearingenvironment (synonymous) Specify the correct lube viscosity: Enlist vendors

Select film strength formulations, know about

viscosity improvers and other additives

What does this imply? Mineral oils versus

synthesized hydrocarbons---synthetics

When are the latter justified? For an experts

answer, view the next slide


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Liquids always tend to wash off lubricants


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(4) Where only synthetics will do:

(1) In bearings operating at (or developing) hightemperature, synthetics slow down oxidation and filmthickness degradation

(2) When increased vibration alerts you to an incipient

defect, synthetics fill micro-cracks(3) After deleting cooling water (which best-of-class

companies have done for the past 40 years), synthetics

greatly expand range of allowable operating temps

(4) In gear units of all sizes (except if common w/comp.(5) In reciprocating process gas compressor cylinders


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(5) Superior bearings

are available

Double-row bearingswith two inner rings (top)

Ceramic bearings best inwet screw compressors

API 610 is only a guide

PumPacbrgs preventsliding and heat-related

bearing degradation Buy only from mfrs that

can provide applicationengineering expertise


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Notice the REs expanding horizons

Its not machine fail; must be machines fault

Its not fix only what is broken. Underlyingcauses must be found and addressed

Always an early warning; API-stds are only min.

Rarely only one deviation; several deviationswill combine and cause a failure

When someone says weve always done it thatway---they may have always done it wrong


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(5a)--Sliding pipe support details

Note that 2 polymer(Teflon) plates areneeded

Consider whathappens if money issaved using onlya single poly plate:Rust forms on thesteel surfaces andnothing moves!


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(5b) Effect of pulling pipe into place: Distress

Bearing is designedto make contourcontact

Pipes pulled into

place to matchcasing nozzles willcause casings todistort

Bearings are point-loaded and the oilfilm is no longeradequate


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(6) Rotary valve stuffing boxes and pump bearing housings

need protection against intrusion of debris

Remember: Modernbearing housing seals

for pumps are designed

as rotating labyrinths

Advanced seals do not

have an O-ring that

contacts a sharp edge or

O-ring groove Unless specified, youll

always get the cheapest


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(7) Spare parts management: New 3D

printer methods make patterns for

castings; contour measuring machines

Getting primed for implementing modern 3D PrinterMethods of pattern production for certain spare parts(buying very few spare parts). A good project decision!

Thus: Linking up with a knowledgeable provider will beadvantageous to the owner-purchaser or design firm, andalso for existing plants that need to consolidate spares.

Contour-measuring allows superb reverse-engineering


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(8) Old traditional oil mist lubrication: Some OMescaped before it had an opportunity to reach the bearings


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(8) Oil mist applied per API-610 (2009)

allows flow entirely through bearings


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(9) Grouting and hold-down bolt issues

avoided with epoxy-filled base


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Anchor bolt, on left, must have a free length (non-

encased, allowed to stretch) equal to 10 diameters


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Typical as-installed baseplate cost

comparison:Conventional vs. Pre-Filled

$ 6,259

$ 4,194

$ 2,065

IMMEDIATE

PAYBACK!

Equipment Installation: Baseplates


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(10) Seal-related upgrade opportunities

Enlist an expert to optimize your mechanical sealSpecifications and buy seals from 2 or 3 suppliers

Make a competent vendor your failure reduction

partner, not merely your supplier of inexpensivemechanical seals

Plan to upgrade to dual seals and closed-loopwater management systems wherever possible. Itis sure to decrease repair frequency and will savemuch money


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Sometimes it is advantageous to interrupt the flow

around the seal faces; one could use Vortex Breakers

Option 1: Changing the seal environment


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Option 2: Change to dual sealsbut beware

Some seal designs do not optimize the exchange of fluid.

Parallel slots move little, if any, of the barrier fluid


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Change the environment with a superior dual

seal; add value with better pumping rings

Some dual seal designs truly optimize the exchange of fluid.

This one uses a wide-clearance tapered pumping ring


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Mechanical seal with internal flow baffle(shown here with a flow guide, but w/o tapered pumping ring)


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Bi-directional internal flow device (Buffer Fluid

Impeller) incorporated in mechanical seal


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Bi-directional barrier fluid pumping device---a

highly effective Tapered Barrier Fluid ImpellerTHREE ADVANTAGES

Efficient No cost impact

Moves more

cooling fluid to

critical regionof mechanical seal


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API 682 / ISO 21409Awareness of

Standards and deviations from same

All seals should operate continuously for

25,000 hours without need for replacement

The minimum performance requirements and

permitted leakage detailed in Section

10.3.1.4.1 of the standard specifies an average

leakage rate of less than 5.6 grams / hour perset of seal faces


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Air Testing Protocol outlined in Section10.3.4.2 of the standard

Each sealing section shall be independently

pressurized with clean air to a gauge pressure of0.17 Mpa (1.7 bar) ( 25 psi). The volume of eachtest setup shall be a maximum of 28 liters (1 cu. ft.)

Isolate the test setup from pressurizing source and

maintain the pressure for at least 5 minutes The maximum pressure drop during the test shall be

0.014 Mpa (0.14 bar, or 2 psi)*

API 682 / ISO 21409

T t


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Test 125 L Vessel plus

1.5 approximate air volumein rig providing total of

26.5 liters, or95% of the

maximum air volume per

10.3.4.2 pressure tested.Result: Pass

Tests

Test 226.5 Liter air

volume fitted with a NPT plug with a 0.008

hold drilled through the

center. Pressure tested.

Result: Pass


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Test 326.5 L Air volume

connected to mechanicalseal fitted with the NPT

plug with 0.008 hole.

Pressure tested

Result: Pass

Tests

Test 41.5 L Air Volume

connected to Mechanical

seal fitted with the NPTplug with 0.008 hole.

Pressure tested

Result: Fail

T t 6 7 & 8 O ifi d f th l d tt h d

F il


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Test 6, 7 & 8 Orifice removed from the seal and attached

to nitrogen pressurized water vessel to measure the leakage

at different pressures against the 5.6 grams /hour (g/h)

specification in API 682 / ISO 21409

1,500 g / h270 x allowable test

Fail

3,000 g / h

540 x allowable test

Fail

7,500 g / h

1,300 x allowable test

Fail

of Webinar 9, (6/20/ 2013)


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Summary

1. Decision to deal only with the best vendors;MQA and pre-investment in risk reduction

2. Decisions with impact on reliability of

reciprocating compressors3. Oil mist for superior storage preservation

4. Use synthetics where only synthetics will do

5. Bearings for highest reliability: from vendorswith application engineering know-how!


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Summary

6. The right bearing protection is part of built-inreliability. Specify it in the project

7. Fewer spare parts: Use 3D print pattern library

8. Plant-wide oil mist includes electric motors!Rapid payback is possible (SKF/Colfax Ind., etc)

9. Pre-grouted epoxy-filled base plates make

economic sense and give long trouble-free life10. Better and smarter mechanical seal options exist


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QUESTIONS?

machinery reliability-heinz bloch

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