fans

FA

NS

MODULE 9

Implemented by AGRA Monenco Atlantic Limited for the Canadian International Development Agency

SADC Industrial Energy Management Project

LEARNING OBJECTIVES

In this module you will learn about:

General Objectives:

L Fans

Specific Objectives:

L Types of Fans Used in Industry,

L Basic Operating Principles of Fans,

L Application of Fan Systems,

L Fan Maintenance,

L Opportunities to Improve Fan Efficiency.

Performance Objectives:

After successfully completing this module you will be able to:

L Identify Fan Types,

L Identify Operating Characteristics of Fans,

L Calculate Fan Power and Energy Consumption,

L Evaluate Fan Performance,

L Recommend Fan System Improvements.

Module 9Fans

TABLE OF CONTENTS1.0 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2.0 FANS OPERATING PRINCIPLES AND FAN LAWS . . . . . . . . . . . . . 1

2.1 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.2 Centrifugal Fans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.3 Axial Fans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3.0 AIR FLOW MEASUREMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

3.1 Air Flow Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63.2 Fan Performance Measurements . . . . . . . . . . . . . . . . . . . . . . 7

4.0 FAN PERFORMANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

4.1 Fan Power Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . 84.2 Fan Performance Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . 84.3 Density Consideration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

5.0 FAN LAWS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

6.0 SYSTEM EFFECT FACTORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

7.0 ENERGY MANAGEMENT OPPORTUNITIES . . . . . . . . . . . . . . . . . . 11

7.1 Maintenance Opportunities . . . . . . . . . . . . . . . . . . . . . . . . . . 127.2 Low Cost Opportunities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147.3 Retrofit Opportunities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147.4 Comments on Flow Control . . . . . . . . . . . . . . . . . . . . . . . . . . 14

8.0 WORKED EXAMPLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

9.0 ASSIGNMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

10.0 SUMMARY - Module 9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

SADC Industrial Energy Management Project Page 1 of 20

MODULE 9FANS

1.0 INTRODUCTION

Fans are subject to more misuse, abuse and faulty applications than virtually anyother type of equipment. The result of ineffective utilization is high energy costwhich can be reduced to yield sizeable savings. The fans provide the motive powerto circulate the heating or cooling medium in most of the systems in use today. Inselected applications specially designed fans are used for materials handling. Thecontrol of the energy consumed by fans is very important to the overall efficiencyof the system.

2.0 FANS OPERATING PRINCIPLES AND FAN LAWS

2.1 Definitions

!! Fan

A fan is a device that causes flow of a gaseous fluid by creating a pressuredifference on the medium to be transported. The gaseous fluid transported bythe fan is most often air and/or toxic fumes (whereas blowers may transport amixture of particulates and air).

!! Blower

A blower is similar to fan, except that it can produce a much higher staticpressure. Sometimes higher pressure is achieved by a multistage impellerarrangement. Engineering practice distinguishes fans and blowers for lowpressure and centrifugal compressors for high pressure. The demarcationbetween blowers and compressors is set at a 7% increase in the density of airfrom blower inlet to blower outlet. The fan and blower definitions and formulae,which assume incompressibility, apply below this demarcation with insignificanterror.

In this module, blowers will be designated as fans.

There are two basic types of fans. Centrifugal fans move air by the centrifugalforce that is produced by moving the air between the rotating impeller blades, andby the inertia generated by the velocity of the air leaving the impeller.

Axial fans move air by the change in velocity of the air passing over the impellerblades. There is no energy added to the air by centrifugal forces.

Module 9 - Fans ....


Figure 9.1CENTRIFUGAL FANS & PERFORMANCE CURVES

2.2 Centrifugal Fans

Centrifugal fans are made with several blade types, the two main ones beingforward curved and backward inclined. (Refer to Figures 9.1 and 9.2.)

!! Forward Curved

Forward curved fans are used in most low pressure systems and run at slowerspeeds than backwardly-inclined wheel types. This type of fan, at constantspeed, will show considerable horsepower increase as the system's staticpressure decreases, resulting in the possibility of motor overload.

! Backward Inclined

The backwardly inclined wheel is used in high pressure duct systemapplications and is non-overloading under normal conditions. This fan will have



less blades in the wheel and they may be flat or slighly curved in comparisonto the closely spaced blades of the forward curved fan which are never flat.Backwardly inclined fans will have a higher efficiency in their design range andwill usually operate at considerably higher speeds.

! Airfoil

Airfoil fans have a special backward curved air foil type blade. These fans havethe highest efficiencies and operate at very high RPM, from 1750 to 3000.They are found on all system types - low, medium and high pressure; but arealso the most expensive.

! Radial Blade

Radial blade fans are used for material handling and have self-cleaning blades.These are least efficient of the centrifugal fans.

Figure 9.2CENTRIFUGAL FAN PERFORMANCE CHARACTERISTICS

Fan Type Flow Pressure Power Range UsesMaximum Maximum Maximum Efficiency

(1000 L/s) (Pa) (kW) (%)

Forward 100 750 11 72-76 Building ventilatorsCurved Building exhausters

Washroom exhausters

Boiler forced draft

Airfoil 425 3500 2240 84-91 VentilatingAir supply

Flat Radial 70 5000 450 70-72 Flue gas recirculationBlade Hot primary air

Modified 70 4000 450 78-83 Handling gas streams withRadial Blade moderate dust loading

Boiler induced draft

Sawdust and chipsGrain dust

Open Radial 70 4000 450 65-70 Rags and woolBlade Paper shreds and stringy

Long shavings

material

Backward 175 2200 450 77-80 ventilationInclined Ventilation, air conditioningBackward and heatingCurved Boiler forced draft

Commercial and industrial



Figure 9.3AXIAL FANS & PERFORMANCE CURVES

2.3 Axial Fans

Refer to Figures 9.3 and 9.4.

!! Propeller Fans

The propeller type fan, either direct or belt driven with flat or slightly curvedblades, is usually used in places where they operate against very low pressuresand are very seldom connected to a duct system. They are mostly used tomove large volumes of ventilation air through large openings in the walls orroofs where the outlet has a small pressure loss.



! Tubeaxial Fans

The tubeaxial fans are more efficient than propeller fans and are capable ofhigher differential pressures.Tubeaxial fans have four to eight airfoil or curvedblades.

The housings are cylindrical tubes formed so that the running clearancebetween the blade tips and the tube are minimal. The construction results intubeaxial fans having higher efficiencies than propeller fans. Ease ofinstallation, reasonable cost and low maintenance are the main advantages oftubeaxial fans. They are used in certain industrial applications such as dryingovens, paint spray booths and fume exhaust systems.

!! Vaneaxial Fans

Other axial fans have blades of an air foil design and can be operated againstpressure. They are usually direct driven and operate at higher speeds than thepropeller fans. On this type of fan, the horsepower curve will rise sharply withan increase in speed and/or system resistance, so that the motor can be easillyoverloaded.

Figure 9.4AXIAL FAN PERFORMANCE CHARACTERISTICS

Fan Type Flow Differential Power UsesMaximum Maximum Maximum

(1000 L/s) Pressure (kW)(Pa)

Propeller 57 300 15 plants, and agricultural buildings.Ventilation in factories, power

Personnel cooling fans or as a lowcost ventilator.

Tubeaxial 47 500 60 low differential pressure.Transferring large volumes of air at

Exhausting spray booths.

Vaneaxial 118 5500 112Mine ventilation

Tunnel ventilation

Fume exhaust

Velocity ' 0.764 xT x Pv

B

0.50



Figure 9.5PITOT TUBE FLOW MEASUREMENTS

3.0 AIR FLOW MEASUREMENTS

3.1 Air Flow Measurements

The total pressure of an air stream flowing in a duct is the sum of the staticpressure exerted on the sidewalls of the duct and the velocity pressure of themoving air. In Figure 9.5, the illustrated pitot tube is a common device formeasuring the velocity pressure. Measurements should be taken in accordancewith traverse details shown. The velocity pressure should be calculated for eachtraverse position and the readings averaged. Using these measurements, thevelocity of air in a duct can then be calculated.

where:Velocity = average air velocity (m/s)T = temperature (EK) ( C + 273.15)o

P = velocity pressure (Pa)V

B = barometric pressure [kPa(absolute)]0.764 = equation constant and conversion of units

The equation can be simplified for standard conditions of 20 C and 101.325kPao

barometric pressure.

Velocity = 1.30 x PV0.50



The volume air flow rate can then be calculated.

f = Velocity x A x 1000a d

where:f = volume air flow rate (L/s)a

A = area of duct (m )d2

1000 = conversion of units

3.2 Fan Performance Measurements

The performance of fans is easily determined by calculations based on measureddata taken at the fan inlet and outlet using the methods previously described.Several factors, however, can affect the accuracy of the field measurements.

< Air flow not at right angles to the measurement plane.< Non-uniform velocity distribution.< Irregular cross sectional shape of the duct or passageway.< Air leaks between the measurement plane and the fan.

Field Performance Measurements, Publication 203 by the Air Movement andControl Association Inc (AMCA) provides information about equipment andprocedures for more precise fan performance measurements.

The total differential pressure across the fan can be calculated from the measureddata.

DP = Ps + Pv - Ps - PvT o o i i

where:DP = total differential pressure (Pa)T

Ps = static pressure at outlet [Pa(gauge)]o

Pv = velocity pressure at outlet (Pa)o

Ps = static pressure at inlet [Pa(gauge)]i

Pv = velocity pressure at inlet (Pa)i

The total fan static differential pressure can also be calculated

DP = Ps - Ps - PvS o i i

where:DP = total fan static differential pressure (Pa)S

The effect of inlet and outlet conditions have not been included in these equations,however, they provide a reasonable basis for the further calculation of fan powerand static efficiency.

Wt 'Q x Pt

1000



Figure 9.6PERFORMANCE CURVES

4.0 FAN PERFORMANCE

4.1 Fan Power Requirement

The work done by a fan can be measured by the quantity of air it delivers, and thepressure against which this air is delivered. Assuming the fan is 100% efficient, thetheoretical power (W ) required to move a given volume of air (Q) against a totalt

pressure (P ) can be calculated as follows:t

whereW = theoretical power required to move air at 100% efficiency (kW)t

Q = air flow (L/s)P = total pressure against which air is moved (kPa)t

The overall fan efficiency relates the theoretical output against the electrical powersupplied to the fan system and includes fan losses, belt drive losses, and motorlosses. Note that the efficiency stated by most fan manufacturers is for the fan unitalone; (i.e. the theoretical output as a ratio of the power input to the fan shaft).

4.2 Fan Performance Curves

Fan performance information is available from the manufacturers on all productionfans in the form of "fan performance curves". Figure 9.6 shows a typical curve.

A fan operates along a performance give given by the manufacturer for a particularfan speed. (The fan performance chart shows performance curves for a series offan speeds.) At fan speed N , the fan will operate along the N performance curve1 1

as shown in the schematic. The fan's actual operating point on this curve willdepend on the system's performance characteristics.



In any fan system, the resistance to air flow (pressure) increases when the flow ofair is increased. The pressure required by a system over a range of flows can bedetermined and a "system performance curve" can be developed (shown as SC ).1

This system curve can then be plotted on the fan curve to show the fan's actualoperating point at "A" where the two curves (N and SC ) intersect. This operating1 1

point is at air flow Q delivered against pressure P .1 1

Two methods can be used to reduce air flow. One is to restrict the air flow bypartially closing a damper in the system. This action causes a new systemperformance curve (SC ) where the required pressure is greater for any given air2

flow. The fan will now operate at "B" to provide the reduced air flow Q against2

pressure P .2

The air flow could also be decreased by leaving the damper fully open andreducing the fan speed to N . The fan would operate at "C" to provide the same2

Q air flow but at a lower pressure P . Reducing the fan speed is a much more2 3

efficient method to decrease air flow since less power is required and less energyis consumed.

4.3 Density Consideration

Fan performance data, unless otherwise specified, is based on dry air at thestandard atmospheric pressure of 101.325 kPa (29.921 in. Hg) and a temperatureof 20EC (70EF). The density at standard test conditions is 1.2 kg/m .3

In most applications, fans process moist air at temperatures and pressures otherthan standard conditions; therefore the air density must be corrected to obtain theactual fan performance. For fans processing moist air, the moisture content of theairstream is determined by measuring the wet bulb temperature or the dew pointtemperature or relative humidity. Wet bulb and dry bulb temperatures are mostoften determined at fan inlet conditions, using a sling thermometer. When theairstream exceeds 82EC the dew-point temperature is more reliable to determinethe moisture content. Density, when the dry bulb temperature falls between 5ECand 38EC, may be determined by using the psychrometric chart.

For Standard Atmospheric Data for Altitudes and Psychrometric Charts, refer toAppendix D.

5.0 FAN LAWS

The fans operate under a predictable set of laws concerning speed, horsepowerand pressure. A change in RPM of any fan will predictably change the pressurerise and horsepower necessary to operate it at the new RPM.

Flow1

Flow2

''Speed1

Speed2

P1

P2

''Speed1

Speed2

2

kW1

kW2

''Speed1

Speed2



If only the RPM is changed the the following will take place:

Figure 9.7

! Air volume in cubic meters persecond will vary directly as therevolutions per minute (RPM).

Varying the RPM by 10% decreases orincreases air delivery by 10%.

! Static pressure ( SP) will vary asthe square of the RPM.

Varying the RPM by 10% decreases orincreases the static pressure by 19%.

! Fan power (kW) will vary as thecube of the RPM.

Varying the RPM by 10% decreases orincreases the power requirement by27%.

6.0 SYSTEM EFFECT FACTORS

The fan is normally tested with open inlets and straight duct attached to the outlet;this results in uniform airflow into the fan and efficient static pressure recovery atthe fan outlet. If these conditions are not matched in the actual installation, theperformance of the fan degrades; this must be allowed for when selecting a fan.

The fans are sensitive to their application in the distribution system. Thischaracteristic is called "System Effect" and involves air movement at the inlet andoutlet connections of the fan. The changes in direction of flow at the outlet or inletof the fan will adversely effect the fan performance. Dampers very close to the inletor outlet and branch ducts very close to the discharge will also have an adverseeffect on fan performance. The biggest problem with the system effect is that itcannot be measured in the field even though it reduces the output of the fan.Typical conditions are shown in Figure 9.8.



Figure 9.8FAN INLET CONDITIONS

7.0 ENERGY MANAGEMENT OPPORTUNITIES

Balancing of an air handling system normally requires services of an experiencedspecialist and is generally performed after the system is installed. For the purposeof this module it is assumed that the existing air handling system was initallybalanced and has been operating efficiently. Over the years, however, thecomponents of the system wear down. The fan wheels get out of balance due todirt accummulation and start to vibrate and become noisy. Bad bearings on the fanshaft can cause vibration as well as damaged fan wheels. Dirty filters can reduceair flow considerably reducing the motor load and creating false savings. It isevident that the first step in assessing the air handling systems is to bring them upto design operating conditions through proper maintenance



Figure 9.9BELT DRIVE LOSSES

7.1 Maintenance Opportunities

!! Check Fan for Correct Rotation

!! Check and Adjust Belt Drives on Fans Regularly

Improper alignment of the fan drive sheaves can cause excessive powerrequirement and damage to belts. Properly aligned and tensioned belt drivesystems will have mechanical losses as indicated in Figure 9.9. Misaligned andloose belts will have losses of power outside the indicated limits. High speedfans will have losses close to the upper limits of the curve and low speed fanswill have losses close to the lower limit of the curve.

!! Lubricate Fan Components According to Manufacturer's Instructions

Lubrication of fan components, such as couplings, shaft bearings, adjustmentlinkage and adjustable supports, must be maintained with proper lubricants andat intervals recommended by the manufacturer.

! Clean Fan Components Regularly

Fans, particularly those handling dirty air, should be cleaned regularly tomaintain their efficiency. Contamination on blades and housing interior causeshigher static pressure loss in the fan, thereby reducing their efficiency.



!! Correct Excess Noise and Vibration to Ensure Smooth and EfficientOperation

The noise and vibration of the fan can be caused by one or more factors:

< Fan wheel out of balance< Bad bearing< Insufficient isolation< Misaligned shaft seal< Corrosion between shaft and bearing

!! Correct Leaks

Energy is lost when air leaks from loose connections, improperly sized dampershaft openings and unsealed expansion connections. These and similarconditions at fan suctions and discharges should be corrected.

!! Replace Loaded Air Filters

Loaded air filters is a common cause of poor performance in fan systems. Filtermanufacturers provide recommendations for the pressure drop at which theirfilters are considered fully loaded for various air velocities at the inlet to thefilters. Filters should be replaced before their pressure drop reaches the loadedvalues for the particular air velocity. Balancing a system with loaded filters willresult in excessive air flow and higher fan energy consumption when the filtersare replaced.

!! Implement Maintenance Programme

A maintenance programme for fans should be tailored to the specific needs ofthe facility. This type of programme could include the following actions:

< Daily; observe fan sounds, vibration, bearing temperature, and readingof installed gauges and meters.

< Monthly; check drive belt alignment, belt tension, and lubricate the fanbearings.

< Semi-annually; inspect fan shaft seals, check inlet and outlet dampers,check inlet vanes, drain and refill oil lubricated bearings.

< Annually; check lubrication lines to assure proper movement of greaseor oil, check fan auxiliaries, recalibrate all associated instrumentationand carry out performance tests.

< Replace worn components.



7.2 Low Cost Opportunities

Implemented low cost opportunities are Energy Management actions that are doneonce and for which the cost is not considered great. The following are typicalEnergy Management Opportunities in this category.

! Reduce fan speed to suit optimum system air flow with balancing dampers intheir maximum open position for balanced air distribution.

! Improve fan inlet and outlet duct connections to reduce entrance and dischargelosses.

! Shut down fans when not required.

7.3 Retrofit Opportunities

The retrofit opportunities are the ones for which the implementation cost issignificant. Many of the projects in this category, with the exception of replacementof oversized motors, require detailed analysis by specialists and are beyond thescope of this module. The following are typical energy management opportunitiesin the Retrofit category.

! Add variable speed motor to allow fan output to follow system requirements.

! Replace outdated equipment with new units sized at optimum efficiency.

! Replace oversized motors.

! Install a microprocessor-base energy management control system.

7.4 Comments on Flow Control

Air handling systems are usually engineered for 100% design flow, but many timescould operate with less flow. Let's say that 50% flow is required for some time.

What are the options? Operate with constant volume, control the flow withdampers or air inlet vanes, or install one of the adjustable speed drives? Figure9.10 shows the approximate energy use by different control systems at 50% flowconditions.

Some observations about these methods:

< Constant volume waste energy.< Dampers may be noisy and have limited turn down.< Inlet vane control restricts flow even when wide open.< Adjustable speed drives have the ability to re-adjust the fan to exact needs

through speed control. This reduces fan noise and more importantly, savesthe most energy. However, will the extra cost be justified?



Figure 9.10ENERGY USED AT 50% FLOW

Figure 9.11TYPICAL POWER vs FLOW CURVES

.

When the cost of speed control must be justified through energy savings alone,there are several pieces of information required. The most obvious are:

< Fan kW (not the motor kW);< Cost of electricity (including demand and power factor penalties);< Installed cost of equipment.

Some less obvious information requirements are:

< Hours/year from 0 - 60% flow< Hours/year from 60 - 80% flow< Hours/year from 80 -100% flow



Figure 9.11 shows typical Power vs Flow curves that are based on the % powerrequired by the fan to produce design flow, i.e. 100% design flow requires 100%power at the fan input shaft. These curves are based on a fan which is 10%oversized. The fans are usually oversized because:

< filters clog and leaks develop,< design engineers are conservative,< the next smaller sized fan could not meet design flow requirements.

All curves are based on the use of an AC motor with 90% efficiency at full speed,full load, and typical reduction in efficiency for reduced loads.

If the preliminary investigation indicates a good potential savings with the use of theadjustable speed drive, a speed control specialist should be consulted to work outthe details.

8.0 WORKED EXAMPLE

Reduce Fan Speed to Match System Requirements

A belt-driven centrifugal supply fan supplies air to a series of process stations asillustrated. While doing an air balance check on the system, all supply air systemdampers, including the damper on the main duct run, had to be partially closed toreduce air flow to the design values. It was recognized that fan energy could besaved by reducing the supply fan speed to allow the main balancing damper to befully opened.

The following initial conditions were measured on the air supply system:

< Air Volume Flow Rate (f ) 19,000 L/sa

< Fan Differential Static Pressure (DP ) 1.12 kPas

< Pressure Differential Across MainBalancing Damper (DP) 0.17 kPa

The following initial conditions were measured on the air supply fan and motor:

< Calculated Motor Power Input (W ) 26.8 kW1

(per measured volt / amp / PF)< Supply Fan Speed (N ) 730 rpmf1

< Motor Speed (N ) 1,800 rpmm1

< Fan Sheave Pitch Diameter (D ) 560 mmf1

< Motor Sheave Pitch Diameter (D ) 230 mmm1

Nf2 ' Nf1 xDf1

Df2

' 730 x 560230

' 1,777rpm

%Slippage 'NM & NF

NM

x 100 '1,800 & 1,777

1,800x 100 ' 1.3%

DPs2 ' DPs1 & DP ' 1.12kPa & 0.17kPa ' 0.95kPa

Wt1 'Q x Ps1

1000'

19,000 x 1.121000

' 21.28kW

Wt2 'Q x Ps2

1000'

19,000 x 0.951000

' 18.05kW

W2 ' W1 xWt2

Wt1

' 26.8 x 18.0521.28

' 22.7kW

N2 ' N1 xDPs2

DPs1

0.5

' 730 x 0.951.12

05

' 672rpm



The supply air system operates 10 hours per day during 260 days per year that theprocess operates, or 2,600 hours per year. Electricity costs $0.10 per kWh.

a) Check belt slippage to confirm acceptable operation.

Note fan rpm and motor rpm should be the same if both sheaves were equaldiameter. The "equivalent" fan rpm with a 230 mm sheave (similar to motorsheave) would be:

Slippage can be calculated by comparing the motor rpm against an "equivalent"fan rpm as follows:

This level of slippage is considered acceptable. Therefore adjustment is notrequired before proceeding with the analysis.

b) Reduced differential static pressure across fan (DP ) with main balancings2

damper full open will be:

c) Theoretical power (W ) with damper in original partially-closed position is:t1

d) Theoretical power (W } with damper in new fully-open position would be:t2

e) Reduced fan power requirement (W ) to operate with open damper at reduced2

fan speed will be based on a ratio of the two theoretical powers.

f) Reduced fan speed (N ) to supply equal air flow with reduced static pressure2

differential will be:

CostSaving ' PowerReduction x Op.Hours x Energy' (26.8kW & 22.7kW) x 2,600hrs/yr' $1,066peryear

Dm2 ' Dm1 xN2

N1

' 230 x 672730

' 212mm

Df2 ' Df1 xN1

N2

' 560 x 730672

' 608mm

SPB 'CapitalCostCostSaving

'$1,000

$1,066/y' 0.94years



g) Energy cost saving resulting from reduced fan power requirement will be:

h) Reduce fan speed either by installing larger sheave on fan or by installingsmaller sheave on motor. New diameter sheave required in either case is:- If new motor sheave, replacement size will be:

- If new fan sheave, replacement size will be:

f) Cost to install new sheave is estimated at $1,000. Simple payback (SPB) is:

9.0 ASSIGNMENT

The purpose of this assignment is to assess the operating condition of the existingair handling systems in the facility and to bring them close to their design operatingcondition. After completing this task several energy management opportunities canbe explored appropriate to the plant or the building conditions.

The following procedure is suggested:

!! Measure and record electrical data as required to complete Electric MotorSchedule (part of Module 6 assignment). Estimate operating hours andcalculate energy consumption and energy cost per annum.

! Check condition and operation of fan. Record (and correct) maintenance /housekeeping deficiencies (Section 7.1) using "Summary Action" or "EnergyManagement Opportunities" forms from Module 3.

! For belt-drive fans:< Measure and record the sheaves pitch diameters.< Measure and record fan and motor rpm.< Calculate belt slippage. (1-2% is normal. Correct if more.)

! Recheck electrical power and energy usage. Calculate energy cost savings,if any, from implementation of maintenance measures.

! Check fan performance curves.< Is the fan appropriate for the specified design air flow and pressure?



!! If instrumentation is available, measure static and total pressure drop acrossfan and locate actual operating point on the fan performance curve. (Use fanrpm as second parameter.)

< Is actual operation in excess of design requirements?< Can the actual flow rate be reduced?

Note: if instrumentation is not available for measurements on larger systemswith significant energy usage, the services of a balancing specialist should beconsidered.

! Investigate complete air handling system to determine if fan pressure can bereduced.

< Check fan inlet and outlet conditions.< Check if dampers are set to throttle system flow?< Check the vovlume control system.

! Investigate the possibilities of reducing the running cost of air handling systemusing the approaches outlined in the Energy Management Opportunities in thismodule.

< Calculate power, energy and cost savings by applying fan laws andconfirming on fan performance curve.

! Prepare one page report for each recommended action using either theSummary Action Form (maintenance improvements) or Energy ManagementOpportunities Form (cost measures) from Module 3.

! Investigate the existing scheduled maintenance for air handling systems andconfirm if program is adequate. Implement additional procedures as required.



In this module you have learned about:

L Types of Fans,

L Fan Operating Principles,

L Fan Laws,

L Air Flow Measurements,

L Fan Performance Measurements,

L Energy Management Opportunities.

You should now be able to perform the following tasks:

L Establish Belt Slippage,

L Measure Operating Conditions,

L Calculate Power and Energy Consumption,

L Calculate Annual Energy Costs,

L Evaluate Fan Performance,

L Evaluate Fan Maintenance Program,

L Develop System Improvement Recommendations.

6.0 SUMMARY - Module 10

fans

Documents

fan types

fan maintenance

fan laws96

fan efficiency

fan laws2

fana fan

centrifugal fans

fan performance measurements