Generator Set Installation Fundamentals

Generator SetInstallation Fundamentals

PRODUCT INFORMATION

PRODUCT INFORMATION — GENERATOR SET INSTALLAT ION

1

Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

Foundations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-11

Noise. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-14

Air Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15-21

Exhaust. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22-27

Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28-29

Cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30-43

Heat Recovery. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44-54

Fuel System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55-66

Starting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67-77

Engine Governors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .78-86

Servicing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .87-88

CONTENTS

Proper generator set installation is crucial toensuring the efficient, long, and dependablelife of a system, as well as minimizing timespent on maintenance. System planning is thefirst step in achieving Cat performance andreliability. A system installation plan mustaddress the product selected and theenvironment in which the product will operate.Before discussing installation, however, let’sreview some electrical power generationbasics.

• A generator set transforms chemicalenergy into electrical energy and heat.

- The engine converts an air-fuel mixture (chemical energy) into mechanical energyor power.

- The generator then takes power from theengine and converts it into electricalenergy kilowatts (kW).

Primary generator set systems and installationissues include:

• Foundations

• Noise

• Air requirements

• Exhaust

• Emissions

• Cooling

• Heat recovery

• Fuel system

• Starting

• Engine governors

• Servicing


2

GENERATOR SETINSTALLA TION FUNDAMENT ALS

Electricity Horsepower

MechanicalEnergy

ElectricalEnergy

GENERATOR

Several basic foundations are suitable forgenerator sets. The foundation chosen willdepend on the unit selected, as well aslimitations imposed by the specific locationand application.

Generator set foundations must:• Support total wet weight of generator set,

which includes accessory equipment andliquids (coolant, oil, and fuel)

• Maintain alignment between engine,generator, and accessory equipment

• Isolate vibrations of generator set fromsurrounding structures

Support

Mounting Surfaces• Firm, level soil, gravel, or rock provides

satisfactory support for single-bearinggenerator sets used in stationary or portableservice. This support can be used where theweight-bearing capacity of the supportingmaterial exceeds pressure exerted by theequipment package, and where alignmentwith external machinery is unimportant.

• Soil, such as fine clay, loose sand, or sandnear the ground water level, is particularlyunstable under dynamic loads and requiressubstantially larger foundations. Informationconcerning bearing capacity of soils at thesite may be available from local sources andmust comply with local building codes.

• Where support rails or mounting feet haveinsufficient bearing area, flotation pads candistribute the weight. The underside area andstiffness of the pad must be sufficient tosupport the equipment.

• Seasonal and weather changes adverselyaffect mounting surfaces. Soil changesconsiderably while freezing and thawing. Toavoid movement from seasonal changes,extend foundations below the frost line.

Concrete FoundationsMassive concrete foundations are unnecessaryfor modern, multi-cylinder, medium-speedgenerator sets. Avoid excessively thick, heavybases to minimize subfloor or soil loading.Bases should be only thick enough to preventdeflection and torque reaction, while retainingsufficient surface area for support.

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FOUNDATIONS

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7.63 cm(3 in)

FoundationWeightEqual to

Generator SetWeight

FoundationDepth

30.4 cm (12 in)

CONCRETE FOUNDATION

Using Concrete FoundationsIf a concrete foundation is required, minimumdesign guidelines are:

• Strength must support wet weight of unitsplus dynamic loads.

• Outside dimensions must exceed that of thegenerator set by a minimum of 1 ft(304.8 mm) on all sides.

• Depth must be sufficient to attain aminimum weight equal to generator set wetweight (if inertia block is specified forvibration control).

Foundation Design• When effective vibration isolation equipment

is used, floor concrete must only be deepenough to provide structural support of thestatic load.

• If isolators are not used, dynamic loadstransmit to the facility floor and require it tosupport 125 percent of the generator wetweight.

• If generator sets are paralleled, possible out-of-phase paralleling and resulting torquereactions demand foundations that are able towithstand twice the wet weight of thegenerator set.

Estimate foundation depth that willaccommodate generator set weight using theformula:

Bases

There are important factors to consider whenselecting the type of base to be used becausethe different types of bases are designed toaccommodate various needs.

Fabricated BasesEngines with close-coupled, single-bearinggenerators maintain alignment by mountingrails or modest bases. They are commonlysupported by fabricated bases. These bases areused to provide:

• Ease of relocation

• Ease of installation

• Isolation from a flexing foundation

Heavy-Duty Fabricated BaseTwo-bearing generators, generators drivenfrom either end of the engine, tandemgenerators, or tandem engines requiresubstantial boxed bases. They must incorporatesufficient strength and rigidity to:

• Resist outside bending forces imposed on theengine block, couplings, and generator frameduring transportation

• Limit torsional and bending movementcaused by torque reactions

• Prevent resonant vibration

• Provide alignment


4

FD = W

D x B x L

FD = foundation depth in meters (feet)W = total weight of generator set in kilograms (pounds)D = density of concrete in kg/m (lb/ft )

(2402.8 kg/m , 150 lb/ft )B = foundation width in meters (feet)L = foundation length in meters (feet)

3 3

3 3

FOUNDATIONS

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Thermal ExpansionDue to thermal expansion, engines maylengthen 2.3 mm (0.09 in) from cold tooperating temperature. This growth must notbe restrained.

• On single-bearing and most two-bearinggenerators, no close clearance dowels orground body bolts may be used to limitthermal growth.

• For single-bearing generators requiringextremely close alignment, use a groundbody bolt at the flywheel end on one side ofthe engine. No other restraint is permitted.

• Mounting feet of two-bearing generators canbe doweled without harm. Slight expansionwithin the generator is absorbed in thegenerator coupling.

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FOUNDATIONS

ExhaustHeat

RecoveryDevice

1 2 3

Generator

Engine

To Load

Expansion Tank

Low Water LevelShutdown

Pressure Cap & Vacuum Breaker

To Load

From Load

Engine CoolantHeat Exchanger

Load BalancingThermostatic

Valve

From Load

HIGH TEMPERATURE WATER SYSTEM

A/C

Oil/CTo RemoteCooling Device

Load BalancingHeat Exchanger

Circulating Pump

Warm-upThermostatic

Valve

LowWater FlowShutdown

Two-BearingGenerator

Structurally Rigid Base

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Thr ee-point SuspensionOn a long train of equipment such as a tandemarrangement, a very rigid steel base with athree-point suspension is recommended. Thethree-point suspension ensures uniformsupport and factory alignment, even on anuneven surface.

Vibration

Reciprocating engines will vibrate. Whetherslight or severe, the vibration will beperceptable either as noise, a vibration, orboth. Sometimes the vibration will be intenseenough to be detrimental to the engine itself,to ancillary equipment and/or to the actualbuilding.

Engine vibrations are produced and maintainedby regular, periodic driving forces set up byunbalanced moving masses. These are calledforced vibrations.

Free vibrations have no driving force. Whenset in motion such vibrations, if undamped,would continue indefinitely with constantamplitude and natural frequency.

If the frequency of a forced vibration is thesame as the natural frequency of freevibrations, excessive vibration results. This iscalled resonance and can cause seriousproblems.


6

FOUNDATIONSTORSIONAL VIBRATION

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Engine vibration may be of the following typesand causes:

1. Linear vibration — vertical and/orhorizontal inertia forces due to lack ofbalance in reciprocating or rotatingmachinery.

2. Torque reaction — not a vibratory force,but may excite vibration.

3. Torsional vibration of shafting — occurs inany rotating mass elastic system (two ormore masses connected by an elastic shaft)where periodic forces are present. Wherethese forces recur near the naturalfrequency of torsional vibration, resonancemay develop and cause dangerous stress.

4. Axial vibration of shafting — whentorques are applied to a crankshaft, it isalternately shortened and lengthened. Thiscould be troublesome if the natural axialfrequency is near a torsional frequency.

When an engine and generator are to beassembled to each other, vibration studies andtests must be completed to assure satisfactory,trouble-free operation on the job site. Withfactory assembled generator sets, theresponsibility is assumed by the manufacturer.In any case, wherever assembly takes place,someone must assure the integrity of theinstallation from a vibration standpoint.

Vibration IsolationGenerator sets need no isolation for protectionfrom self-induced vibrations. However,isolation is required if:

1.Engine vibration must be separated frombuilding structures

2.Vibrations from nearby equipment aretransmitted to inoperative generator sets

3.System is supported on a flexible mountingsurface, such as a trailer bed

Vibration isolators prevent the transmission ofpossibly damaging generator set vibrationthroughout a building. Noise is also reduced.

Generator Set ProtectionRunning units are rarely affected by exteriorvibrations. Methods of isolation are the samefor external or self-generated vibrations.If an idle engineis located near heavyreciprocating equipment, vibration isolationmust be specified to protect the idle engine. Ifsubjected to repeated shocks or vibrationswhen idle, damage to the bearings, gears, etc.may result. This occurs because the protectionsprovided by the lubricating oil are notavailable.

Another application requiring generator setprotection involves mobile units. Isolationfrom a movable platform is desirable to:

• Reduce vibration

• Reduce noise

• Prevent torque loading on generator setsfrom flexing platforms or trailer beds

• Avoid bending of the generator set bymovement of the sub-base


7

FOUNDATIONS

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Vibration carried throughout an enclosurecauses early failure of auxiliary equipment.Relays, switches, gauges, and piping areadversely affected.

No Isolation ApplicationIf no isolation is required, the generator setmay rest directly on the mounting surface.Factory assembled units are dynamicallybalanced and theoretically there is no dynamicload. However, the surface must support 25percent more than the static weight of the unitto withstand the torque and vibratory loadsresulting from combustion forces andassembly tolerances. Unless the engine is amobile unit or driving equipment whichimposes side loads, no anchor bolting isrequired. Thin rubber or composition padsminimize the unit’s tendency to creep or fretfoundation surfaces.

Both bulk and fabricated isolators utilize staticdeflection. A basic vibration chart willdescribe the general effect deflection has onisolation. By using engine rpm as the nominalvibration frequency, magnitude of compressionon isolating materials can be estimated.

Bulk Isolators

Bulk isolating materials are used between thefoundations and supporting surface, but are notas foolproof as commercial types.

Gravel or sand:• Isolation of block foundations may be

accomplished by 200 to 250 mm (8 to 10 in)in the bed of the foundation pit

• Can reduce engine vibration one-third to one-half

Note: The isolating value of gravel issomewhat greater than sand.

How they’re used:

1. To minimize settling of the foundation,gravel or sand should be thoroughly tampedbefore pouring the concrete block.

2. The foundation pit should be made slightlylonger and wider than the foundation blockbase.

3. A wooden form the size and shape of thefoundation is placed on the gravel or sandbed for pouring the concrete.

4. After the form is removed, the isolatingmaterial is placed around foundation sides,completely isolating the foundation fromsurrounding earth.


8

FOUNDATIONS

IsolatingMaterial

SeparatorFoundation

Sub-Base

INERTIA BLOCK

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Rubber, asphalt-impregnated felt, andfiberglass:• Can also be used to isolate foundation block

from subsoil

• Do not provide significant low frequencyisolation

Cork:• Is not effective with disturbing frequencies

below 1800 cps

• If not kept dry, will rot

• Is seldom used with modern generator sets,but is used to separate engine foundationsand surrounding floor because of resistanceto oils, acids, or temperature changesbetween -18° and 93° C (0° and 200° F)

Commercial (Fabricated) Isolators

Several commercial isolators provide variousdegrees of isolation. Generally, the lower thenatural frequency of the isolator, the greaterthe deflection and more effective the isolation.Weight of generator sets can be unequallybalanced within the limits of the isolators. However, overloading will eliminate isolatorbenefits.

Rubber isolators:• Are adequate for applications where

vibration control is not severe

• Provide 90 percent isolation with carefulselection

• Isolate noise created by transmission ofvibratory forces

• Should not to be used with naturalfrequencies near engine exciting frequencies

Spring Isolators:• Are the most effective isolator design,

isolating over 96 percent of all vibrations

• Provide overall economy

• Permit mounting the generator set on asurface required to support only the staticload

• As with direct mountings, no anchor boltingis usually required; however, when operatingin parallel, vertical restraints are recommended

• Are available with snubbers for use whenengines are side loaded or located on movingsurfaces

Adding rubber plates beneath spring isolatorsblocks high frequency vibrations transmittedthrough the spring. These vibrations are notharmful but cause annoying noise.

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FOUNDATIONS

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10

FOUNDATIONSIsolator Application

Commercial isolators are most effective whenlocated under the generator mounting andengine front support.

To apply isolators, wet weight and center ofgravity of the assembled unit must beestablished. Assuming engine and generator areassembled to a base, wet weight (WT) andassembled center of gravity can be calculated. Acommon reference is needed, usually the rearface of the flywheel housing. Becausemeasurements are to both sides of the reference,one direction can be considered negative.

If additional equipment is added, the process isrepeated to determine a new center of gravity.

Having established the center of gravity for thetotal unit, loading on each pair of isolators(assuming two on each side) is determined by:

Isolators are sized to have natural frequenciesfar removed from engine exciting frequencies.If these frequencies were similar, the entireunit would resonate. A vibrationtransmissibility chart depicts this condition,and also shows the significant improvementcaused by decreasing the mounting naturalfrequency to allow a ratio increase abovesquare root of 2, or 1.414.

Seismic Vibration

Wt(D) = We(D2) – Wg(D1) + Wr(D3)

D =We(D2) – Wg(D1) + Wr(D3)

Wt

where:

wet weight of: distance from rear face block to C/G of:

Generator Set, Wt DGenerator, Wg D1Engine, We D2Radiator, Wr D3

SEISMIC AREAS

Zone 0 — no significant damage

Zone 1 — minor damage

Zone 2 — moderate damage

Zone 3 — major damage

Zone 4 — major faults

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S1 = Wt B

CS2 = Wt

A

C

where:

A = distance from rear isolator to gen set C/GB = distance from front isolator to gen set C/GC = distance between front and rear isolatorsS = load on each pair of isolators

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FOUNDATIONSSeismic shocks are insufficient to harmgenerator sets resting on the floor. However,isolation devices, particularly spring isolators,amplify small movement generated byearthquakes to levels which would damageequipment. Special isolators incorporatingseismic restraining or damping devices areavailable, but exact requirements must bereviewed by the isolator supplier. Isolatorsanticipating seismic shock are bolted to theequipment base and the floor. Positive stopsare added to limit motion in all directions.Attached piping and auxiliary equipmentsupports must also tolerate relative movement.

Trailer Units

Lateral movement of the generator set must beminimized as the trailer is transported. Thiscan be achieved simply by:

• Blocking the unit off the isolators during the move

• Using snubbers to confine vertical andhorizontal movement

A spring-type isolator with the addition ofthrust blocks will restrict lateral movementwithout interfering with spring function.

External Isolation

Piping connected to generator sets requiresisolation, particularly when generator sets aremounted on spring isolators. Fuel and waterlines, exhaust pipes, and conduit couldotherwise transmit vibrations long distances.

• Isolator pipe hangers, if used, should havesprings to attenuate low frequencies, andrubber or cork to minimize high frequencytransmissions.

• To prevent buildup of resonant pipevibrations, long support piping should run atunequal distances.

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Noise can be defined as all unwanted sounds.Noise can produce undesirable psychologicaleffects on people and physical damage to theears. Recognizing this, many governmentalagencies around the world have establishedlimits for various environments.

The physical effects of noise are measured bymicrophones that produce electrical signalsdirectly proportional to sound pressures — theamplitude or strength of the sound pressurewaves. This strength and the frequency of thewaves are the only measurable properties ofsound outside of the laboratory.

The human ear hears pressure levels that areabout 100 000 times stronger than the lowestpressure it is actually affected by. For thisreason, measuring instruments haveextraordinary range and are scaled in decibels(dB). The decibel scale is logarithmic, whichallows sound pressure to be measured in two-or three-digit numbers.

Sound Pressure Level (SPL) in dB = measured pressure

20 log10 x ——————————reference pressure

The reference pressure is taken as: 20 µPa or2 x 10-4 microbars = 0 dB.

The ear is more sensitive to high frequenciesthan low frequencies. To approximate theeffect of sound on the average person,measurements are weighted according tofrequencies corresponding to the sensitivity ofthe ear. The signal from the measuringmicrophone is fed to an amplifier, then to anattenuator, which is calibrated in decibels. Thesignal is then fed to one of four weightingnetworks, referred to as A, B, C, and D. Theresponse of the network chosen modifies theinput signal accordingly.

The most commonly used network isweighting A, and it is known as dB(A). It isoften measured in relationship to time limit forexposure.

Permissible Noise Exposures

Duration of AllowableDaily Exposure Level

(hours) dB(A)

8 90

6 92

4 95

3 97

2 100

1.5 102

1 105

0.5 110

0.25 115

Noise Control

MechanicalMany techniques for isolating generator setvibrations are applicable to mechanical noiseisolation. Modest noise reductions result fromattention to noise sources, i.e., reducing fanspeeds, coating casting areas, and ducting airflows. But for attenuation over 10 dB(A), unitsmust be totally isolated.


12

NOISE

NO

ISE

A 2 dB(A) reduction can be achieved by usingvibration isolators under the generator set.

A 15 dB(A) reduction is afforded with a rigid,sealed enclosure without openings; however,necessary openings for pipes, ventilation, andengine-driven radiator fans drastically reducethe degree of attenuation.

A 40 db(A) reduction can result by usingsealed, double-walled enclosures withabsorption material and double mountingisolators.

Completely enclosed engines, however, areimpractical due to openings required for pipes,ducts, and ventilation. Enclosures withnumerous openings rarely attain over 20 dB(A)attenuation, even with double walls andisolators.

In an effort to achieve high attenuation,radiator air flow may be severely restricted.Reduced radiator cooling capabilities,however, should be anticipated.

A simple but effective method of reducingnoise utilizes concrete blocks filled with sandto house the generator set. Materials withdensities greater than 32 kg/m3 (2 lb/ft3) aregood sound barriers. Filling voids with sand oreven a thick coat of paint helps seal smallcracks in the blocks and further reduces noise.However, the unit must also incorporatevibration isolation techniques.

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NOISE

VIBRATION ISOLATORS — 2 dB(A)

BAFFLES — 5 dB(A)

RIGID SEALED ENCLOSURE — 15-20 dB(A)

SOUND TREATED ENCLOSURESAND ISOLATORS — 35-40 dB(A)

Fiberglass

Sand

Cement Block

ENGINE ROOM INSULATION

NO

ISE

ExhaustExhaust noise attenuation is commonlyachieved with a silencer typically capable ofreducing exhaust noise 15 dB(A) whenmeasured 3.3 m (10 ft) perpendicular to theexhaust outlet. Because the number ofcylinders and engine speeds create variedexhaust frequencies, specific effects ofsilencers must be predicted by themanufacturer.

Sound pressure level of site exhaust noise isdetermined by:

If the sound pressure level of a point source atsome distance is known, the sound pressurelevel at a second distance can be calculated by:

NOISE


14

where:

SPL = known sound pressure level, dB(A)SPL = desired sound pressure level, dB(A)D1 = known distance, m (ft)D2 = desired distance, m (ft)

2

SPL = SPL – 20 x log (D2/D1)2 1 10

1

NO

ISE

Sound Pressure Level, dB(A) =

Sound Pressure Level, dB(A) - 10 x Log (3.1416 x CD )

where:

C = 2 for exhaust source adjacent to a flat surface, such as a horizontal exhaust pipe parallel to a flat roof

= 4 for exhaust source some distance from surrounding surfaces, such as a vertical exhaust stack some distance above a roof

D = Distance from exhaust noise source (m)

10 2

There are four air-related issues to consider inplanning generator set installation.

• Combustion air requirements

• Engine room ventilation

• Crankcase breathers

• Air filters

Combustion Air Requirements

Diesel engines require approximately0.09 m3/min (3.2 cfm) of air per brakehorsepower for combustion, or 17 lb of air foreach pound of fuel. Volumetric (V) and mass(M) intake air flow have the following generalrelationships.

• Heavy fuel engines require about 40 percent greater inlet air flow than those burning distillate fuels.

• Gaseous fueled engines demand twice that ofdiesel.

Intake LocationAlthough normally obtained from airsurrounding the engine, some circumstancesrequire ducting combustion air from outsidethe engine room. This is particularly true inhigh altitude operations where light airdensities are further affected by engine roomtemperatures.

• High intake air temperatures can adverselyaffect engine performance and raise exhausttemperatures, which may damage pistons,exhaust valves, and heads.

• Combustion air entering the engine aircleaners should ideally be less than 38° C(100° F).

• On some engine configurations, prolongedoperation with extremely cold inlet air to theengine may require a boost control valve tolimit intake air manifold pressure andresultant peak cylinder pressure.

• Cold air and altitudes above 2440 m(8000 ft) may cause overfueling when startingautomatically, as some governors remain fullopen during acceleration to rated speed.

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AIR REQUIREMENTS

V (m /min) = .01486 x M (kg/hr)

or

V (cfm) = .2382 x M (lb/hr)

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AIR

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Inlet Air Restriction

When ducting is necessary to obtain cooler orcleaner air, filters should remain on the engine.This prevents harmful dirt from leaking intoducting joints or remote filter housings.

• Fabricated ducting or fasteners such as rivetsshould not be used.

• Baffles incorporated in the duct preventwater from entering the engine.

• Design ducting to withstand a vacuum of 12.5 kPa (50 in. H2O).

• If the filter must be remote mounted, pipingat the turbocharger must encourage smoothair flow.

Filter Duct Restriction FilterChange (pipe size, # bends) Life

30" 2" = 28"*30" 15" = 15"

* 46% increased life

• No duct weight should be imposed on theconnection to the engine.

• Flexible connections are required to isolateengine vibration and noise from the ducting,and should be located as close as possible tothe engine.

• Rubber flexible connections must be routedto avoid harmful heat from exhaust piping.

• Insulation can be used on inlet air ducting toreduce turbocharger noise and reduce heattransfer from the room to the combustion air.

Total inlet duct head loss (restriction) isgenerally less than 0.50 kPa (2 in. H2O)column to maximize time between air filterreplacements. As a general guide, ducting witha diameter equal to the standard air cleaneradapter can accommodate 7.6 m (25 ft) ofstraight pipe. Increasing this diameter 25.4 mm(1 in) will allow 19.8 m (65 ft) of straight pipe.Pipe bends are long radii, with flanged orwelded joints to encourage low restriction. Aflexible connection isolates engine vibrationand noise, and allows easy filter servicing.

Saturated air with the dew point near freezingcan cause icing and clogging of the air cleaner,with resulting performance loss. Procedures toavoid this condition include:

- Prewarming intake air

- Blow-in doors (with alarms) spring loadedto open at 12.5 kPa (50 in. H2O) maximum

- Bypassing the cleaners (only in anemergency)


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AIR REQUIREMENTS

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Calculate duct head loss by: Air Cleaners

Combustion air must be clean and cool.Engine-mounted, dry-type air cleaners areconsiderably more efficient than oil-bath typesand remove 99.5 percent of AC fine dust.

• Clean filters offer little restriction so total airrestriction, including ducting, should notexceed 1.2 kPa (5 in. H2O) of water column.

• Air cleaner service indicators will signal afilter change when a restriction of 3.74 kPa (15 in. H2O) develops.

• Ducting must have sufficient strength towithstand minimum restrictions of 12.5 kPa(50 in. H2O), which is also the structuralcapability of the Caterpillar prime power aircleaner.

AC Dust (% total weight)

Micr on Size Fine Coarse

0-5 39+/-2% 12+/-2%

5-10 18+/-3% 12+/-3%

11-20 16+/-3% 14+/-3%

21-40 18+/-3% 23+/-3%

41-80 9+/-3% 30+/-3%

81-200 0 9+/-3%

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AIR REQUIREMENTS

Adapter forPrecleaner or Duct

Precleaner

ServiceIndicator

Filter

P (kPa) = L x S x Q x 3.6 x 102 6

5D

P (in. H O) = L x S x Q 22

2

2

3

5187 x D

P = Restriction (kPa) (in. H O)L = Length of pipe (m) (ft)Q = Inlet air flow (m /min) (cfm)D = Inside diameter of pipe (mm) (in)in. H O = inches water columnkPa = 6.3246 x mm water columnpsi = 0.0361 x inches water column

The radius of 90-degree bends with radii 1-1/2 timesthe pipe diameter help to lower resistance.

3

3

3

3

If duct is rectangular, D =

a and b = sides of duct (mm) (in)S = Density of air (kg/m ) (lb/ft )

S (kg/m ) =

S (lb/ft ) =

To obtain equivalent length of straight pipefor each long radius 90-degree bend:

L = 33 x

L = 20 x

L = 15 x

L = 66 x

L = 31

where X = 1000 mm or 12 in

(2 x a x b)(a + b)

352.05Air Temperature + 273.16¡ C

39.6Air Temperature + 460¡ F

DX

DX

DX

DX

Standard Elbow(Radius equals pipe diameter)

Long Elbow(Radius > 1.5 diameter)

45-degree Elbow

Square Elbow

Flexible connection(1 = connector length)

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PrecleanersPrecleaners adapt to standard air cleaners toextend filter service periods.

• They impose 0.25 to 0.75 kPa (1 to 3 in.H2O) added restrictions, but increasestandard filter life about three times.

• Conventional precleaners approach 70percent efficiency.

• Exhaust-augmented precleaners exhibit92 percent efficiency, further extend filterelement life and are maintenance free.

Heavy-duty air cleanersHeavy-duty air cleaners provide the sameprotection as standard filters but allow furtherextension of filter change periods. Serviceperiods are six to seven times that of standardair cleaners.

Ventilation

Six to 10 percent of fuel consumed by a dieselengine is lost as heat radiated to thesurrounding air. In addition, heat fromgenerator losses and exhaust piping can easilyequal engine radiated heat. The resultingelevated temperatures in the engine roomadversely affect maintenance personnel,switchgear, and generator set performance.

Engine room ventilation must provide anenvironment:

• Permitting machinery and equipment tofunction properly

• Where maintenance personnel can workcomfortably and effectively

A 7° to 10° C (13° to 18° F) temperature riseis a reasonable target for engine rooms.However, in cold climates this may causediscomfort from the flow of cold air. Restrictflow only if engine combustion air is availableand engine jacket water is adequately cooled.

Engine room ventilation can be estimated bythe following formulas, assuming 38° C(100° F) ambient air temperature:

40° C (104° F) = 0.017 kW/(min•kg•°C)

0.24 Btu/(lb•°F)


18

AIR REQUIREMENTS

V (m /min) = + engine combustion airH

1.099 * 0.017 * dT

V (cfm) = + engine combustion airH

1.070 * 0.24 * dT

3

V = ventilating airH = heat radiation; engine, generator,

aux (kW) (Btu/min)dT = permissible temperature rise in engine

room (¡C) (¡F)

Density of air at:3 340¡ C (104¡ F) = 1.099 kg/m (0.071 lb/ft )

Specific heat of air at:

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While engine room temperatures must becontrolled, air velocities affect workercomfort. Typical air motion at various ambientconditions include:

Air Velocity(fpm) m/min Conditions

50 15.2 Offices, seated worker

100 30.5 Factory, standing worker

150 45.7 Capture velocity, light dust

1300 396 Capture velocity, rain

200 61.0 Maximum continuous exposure

1-2000 305-610 Maximum intermittentexposure

Radiator AirInstallations utilizing remote or engine-mounted radiators may provide sufficient airflow for ventilation, but ventilation air flowrequirements must be compared to radiator fancapabilities.

• Intake and exhaust ventilators may havemovable or fixed louvers for weatherprotection.

• If movable, actuate by pneumatic, electric, orhydraulic motors; never depend on airpressure developed by the radiator fan tomove the vanes.

• In cold climates, movable louvers can bearranged to provide circulation inside theroom until jacket water temperatures reach88° C (190° F).

Once jacket water temperatures reach 88° C(190° F), the radiator must be furnished withsufficient cooling air. Use a number of smallventilating fans rather than a single large unit.Selective fan operation compensates forvarying ambient temperatures whilemaintaining engine room temperatures.

Increase air flow 10 percent for every 763 m(2500 ft) above sea level to maintain originalcooling capability. Final ventilationcalculations must use precise heat radiation ofselected engine, generator, and power output.

Air FlowIdeally, clean, cool, dry air circulates aroundthe switchgear, flows through the rear of thegenerator, across the engine, and dischargesthrough the radiator. Cool air should always beavailable for the engine air cleaner.

• Locate room air intakes to provide maximumcooling air to the generator set.

• Multiple generator sets require additionalopenings and fans.

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• Units not using radiators require a forced airdraft.

• Openings for intake air should be low, nearthe rear of the engine; position outlets highon the opposite wall.

Horizontal Air FlowCool, dry, clean air should enter the engineroom as close to the floor as possible usingfans/ducts. Allow this air to flow across theengine room from the entry point across heatsources such as the engine, exposed exhaust,generator, etc.

• For best results, air should flow first acrossthe generator then to both sides of the engine.

• If engine mounted radiators are not used, airdischarge fans should be mounted or ductedat the highest point directly over the heatsources.

• Air inlet must circulate air between theengines.

• Inlets located at the end of the room willprovide adequate ventilation only to theengine nearest the inlet.

• This technique will dissipate engine heat buta certain amount of heat will still radiate andheat the engine room.

Air Cur tainsAir curtains, totally enveloping the generatorset, provide ventilation without exposing theequipment room to high air velocities.Radiated heat is removed with approximatelyhalf the air flow of a horizontal flow system.

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AIR REQUIREMENTSVertical Air FlowThe least desirable ventilation systemdischarges outside air directly down on theengines with inlet fans.

• Exhaust fans should be mounted in thecorners of the room.

• Because this system interferes with thenatural rising of hot air, ducting should beused to prevent air from taking the shortestpath out of the engine room and bypassingthe engine.

Crankcase Breathers

Firing pressure forces slight amounts ofcombustion gases past piston rings into thecrankcase. Resulting crankcase pressure isrelieved to maintain oil control and seal life byhaving crankcase breathers exhausting fumesat the rate of 0.028-0.042 m3 (1-1.5 ft3)/hp-hr.

Piping• Pipe the breather outlet to an outdoor vent.

Fumes are thus prevented from collecting inthe equipment room, clogging engine intakeair filters and radiator cores.

• Low operating hours of standby applicationsdemand little of air filters, so fumes candischarge immediately in front of the filter.Do not bypass this air filter.

• Each engine’s fumes disposal should haveseparate discharge pipes.

• Avoid low places allowing condensation tocollect and block the fumes passage.

• Allowable crankcase pressure at full load isplus 0.25 kPa (1 in. H2O).

• In unusually long runs of pipe, as in below-ground installations, or if forced to combinemultiple engine breathers, increase pipe sizeto reduce backpressure.

• Excessive restrictions may requireinstallation of a suction device in the line toaid ventilation. Flexible oil- and chemical-resistant tubing is connected (in a non-airtight manner) to the disposal tube socrankcase vacuum is less than 0.06 kPa(0.25 in. H2O).

Breathers in ExhaustNEVER incorporate the breather tube into theengine exhaust system. This can result in abuildup of deposits in the exhaust, and createexcessive crankcase backpressure and apossible fire hazard.

Filters• In prime power applications where fumes

cannot be disposed outside the engine room,special filters can be used to clean thecrankcase fumes.

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Exhaust systems collect exhaust gases fromengine cylinders and discharge them quicklyand silently. One purpose of the exhaustsystem is to minimize backpressure becauseexhaust gas restrictions cause horsepowerlosses and exhaust temperature increases.

Components

Engine exhaust manifolds collect exhaustgases from each cylinder and channel theminto a single exhaust outlet. Several types ofmanifolds are available:

Dry manifolds are the most cost-effective, butleast effective type of manifold for heatshielding. During engine operation, drymanifold surface temperatures can range from430° to 480° C (800° to 980° F).

Watercooled manifolds’temperatures areconsiderably lower than those of drymanifolds. Surface temperatures reach onlyabout 100° C (212° F) during operation.

Passages within watercooled manifolds allowengine jacket coolant to flow around themanifold removing heat otherwise carried byexhaust gases. Heat rejection to the jacketwater will increase 20 to 40 percent, whichrequires a larger capacity cooling system.Loss of exhaust heat energy may affectturbocharger performance, causing enginederation and/or loss of altitude capability.

Water shielded manifoldshave a fabricated auxiliary jacket or shield around the manifold.Engine jacket coolant circulates through theshield but does not come in direct contact withthe manifold casting. This adds little heat tothe engine cooling load and will not affectperformance.

Exhaust System Design

Exhaust restrictions cause performance losses,particularly in fuel consumption and exhausttemperature.

EXHAUST

30-40%

7%

33%20-40%

Water-Cooled

Water-Shielded

Dry

Exhaust

AirPassage

Exhaust

Water

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Restriction Criteria• Pressure drop includes losses due to piping,

muffler, and rain cap, and is measured in astraight length of pipe 3 to 5 diameters fromthe last transition change after theturbocharger outlet.

• Pressure drop across the exhaust systemshould not exceed 6.7 kPa (27 in. H2O) ofwater for most Caterpillar engines.

• 3600 diesel gas engine performance will beadversely affected above 2.5 kPa (10 in.H2O). Exceeding this limit on 3600s willincrease fuel consumption approximately 0.8percent per each 2.5 kPa (10 in. H2O) ofbackpressure above the limit.

• Engines burning heavy fuel have an absolutebackpressure limitation of 2.5 kPa (10 in. H2O) to avoid excessive exhaustvalve temperatures.

Calculate backpressure by:

P (kPa) = L x S x Q x 3.6 x 102

L x S x Q 2

2

2

2

3

3 3

2

6

D5

187 x D5

+ Ps

P (in. H O) = + Ps

P = Backpressure (kPa) (in. H O)L = Length of pipe (m) (ft)Q = Exhaust gas flow (m /min) (cfm)D = Inside diameter of pipe (mm) (in)Ps = Pressure drop of silencer/raincap

(kPa) (in. H O)in. H O = Inches water columnkPa = 6.3246 x mm water columnpsi = 0.0361 x inches water columnS = Specific weight of gas (kg/m ) (lb/ft )

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3

S (kg/m ) =

S (lb/ft ) =

352.05Exhaust Temperature + 273.16¡ C

39.6Exhaust Temperature + 460¡ F

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L = 33 x

L = 20 x

L = 15 x

L = 66 x

L = 31

where x = 1000 mm or 12 in

DX

DX

DX

DX

Standard Elbow

Long Elbow(Radius > 1.5 diameter)

45-degree Elbow

Square Elbow

Flexible connection(1 = connector length)

To obtain equivalent length of straight pipe foreach long radius 90-degree bend:

Exhaust flow in:

kg/min =3(exhaust flow in m /min) (2078)

exhaust gas temperature in ¡C + 273

OR

Exhaust flow in:

lb/hr =

Conversion to Standard Air flow (SCFM) = Actual CFM (ACFM)*

* (density at actual temp/density at std temp)

3(exhaust flow in m /min) (2333)exhaust gas temperature in ¡F + 460

The radius of 90-degree bends with radii 1-1/2times the pipe diameter help to lowerresistance.

Exhaust gas mass flow can be calculated fromthe exhaust gas volumetric flow and theexhaust stack temperature.


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Thermal Growth

Thermal growth of exhaust piping must beplanned to avoid excessive load on supportingstructures.

• Steel exhaust pipe expands 1.13 mm/m/100°C (0.0076 in/ft/100° F) rise in exhausttemperature.

• A temperature rise from 38° to 510° C (100° to 950° F) will cause 16 mm (0.65 in)growth in 3.05 m (10 ft) length of pipe.

Exhaust Fittings

Exhaust pipes are isolated from the enginewith flexible connections which have threeprimary functions:

Minimize exhaust piping weight on theengineEngine exhaust components should not bemore than 27 kPa (60 lb) of piping weightwhen the system is at operating temperature.

Isolation vibrationFlexible connections are needed to relieveexhaust components of excessive vibrationalfatigue and prevent vibration transmissionthrough the building.

Provide for movement of the engine andexhaust componentsMovement between piping and engine iscommon and results from:

• Torque reactions when a generator set ismounted on spring-type isolators

• Expansion and contraction due to thermalchanges. Pre-stretch the bellows duringinstallation to allow it to operate near its freestate at engine operating temperatures.

Piping Layout

Physical characteristics of the equipment roomdetermine exhaust system layouts.

• Thick-walled pipe provides long life whileabsorbing the shocks and noise of thecombustion gases.

• Arrangements with minimum backpressuresare favored, consistent with otherrequirements.

EXHAUST

510¡ C (950¡ F)

38¡ C (100¡ F)

3.21 m (10.05 ft)

3.05 m (10 ft)

VerticalPipe

Support

FlexiblePipe

Connection

FlexiblePipe

Connection

Flexible Pipe ConnectionEngine Exhaust Outlet

Pipe Support

DrainSlight Pitch Away from

Engine

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• Support long runs of piping at unequaldistances to minimize resonant vibrations.

• Pipes should be securely supported andrubber dampers or springs installed in thebracing to isolate vibrations, and routed toavoid interference with overhead serviceequipment.

• Long pipe runs need to be sectioned withexpansion joints. Each section is fixed atone end and allowed to expand at the other.Supports are located to allow expansionaway from the engine, avoid strains ordistortions to connected components, and toallow equipment removal without additionalsupport.

• Install lines with 229 mm (9 in) minimumclearancefrom combustible materials.

• Exhaustthimbles separate the exhaust pipefrom walls or ceiling to provide mechanicaland thermal isolation.

- Single sleeve thimbles have diameters atleast 305 mm (12 in) larger than theexhaust pipe.

- Double thimbles (inner and outer sleeve)have outside diameter at least 152 mm(6 in) larger than the exhaust pipe.

• Long runs of exhaust piping require traps todrain moisture.

- Traps installed at the lowest point of theline near the exhaust outlet preventrainwater from reaching the silencer.

- Slope exhaust lines from engine andsilencer to the trap so condensation willdrain.

- Traps may be built by inserting a verticalpipe down from a tee section in the line.

- Including a short length of plastic pipebefore the drain cock or removable plugwill indicate drainage periods.

• Extended engine operation at loads less than15 percent of rated may induce exhaustmanifold slobber.- This black oily fluid does not necessarily

indicate an engine problem and is notusually harmful to the engine, but can beunsightly and messy.

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- If extended periods of light loads areunavoidable, slobber can be minimized byoperating the engine above 30 percent ofrated power for at least ten minutes everyfour hours.

• Extend exhaust stacks to avoid nuisancefumes and odors.

- Pipe outlets cut at a 30- to 45-degree anglewill reduce gas turbulence, and thus noise.

- Rain caps forced open by exhaust pressurewill keep water from entering.

Insulation

Flexible pipe connections, when insulated,must expand and contract freely within theinsulation. This generally requires a softmaterial or insulated sleeve to encase theconnection.

Common Exhaust System

Although economically tempting, a commonexhaust system for multiple installations isusually not acceptable.

• Combined exhaust systems with boilers orother engines allow operating engines toforce exhaust gases into engines notoperating.

• Every liter of diesel fuel burned providesabout one liter of water in the exhaust.

• Spark ignited engines burning natural gasdevelop 1.6 kg of water for each cubic meter(1 lb/10 ft3) of natural gas burned.

• This water vapor condenses in cold enginesand quickly causes engine damage.

• Additionally, soot clogs turbochargers,aftercoolers, or air cleaner elements.

• Duct valves separating engine exhausts arealso discouraged.

• High temperatures warp valve seats and sootdeposits cause leakage.

Exhaust draft fans have been appliedsuccessfully in combined exhaust ducts, butmust operate whenever exhaust is present.Separate exhaust systems assure expectedengine performance and life.

Piping Outlet

Exhaust heat must be discharged withoutcausing discomfort to personnel or hazards tobuildings or equipment.

• Locate exhaust discharge away fromventilating air intakes to prevent reentry ofoffensive fumes and odors.

• Directing exhaust emissions in front of aradiator blower fan is acceptable; but avoidpremature clogging of the radiator core bypreventing exhaust passing through theradiator.

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Silencer

• Muffler placement greatly affects silencingability. Locating it near the engine minimizestransmission of sound to the exhaust piping.

• Higher exhaust temperatures near the enginealso reduces condensation and carbonbuildup in the muffler; a drain removescondensation.

• At least 5 diameters of straight pipeupstream, and 2.5 diameters downstream arerequired to minimize turbulence andbackpressure.

Both noise reduction and backpressureconsiderations are necessary when selecting asilencer. Engines using heavy fuel have greaterexhaust flow than those burning conventionalfuels, and silencer sizing must account for thisincrease.

Exhaust System Design Summary

• Locate the muffler near the engine; thetransmission of sound through exhaust willbe minimized.

• Provide a drain at the muffler’s lowest pointto relieve condensation.

• To prevent water from entering the system,vertical exhaust stacks require a bend or raincap.

• Minimize potential system resonance bycutting the end of the exhaust pipe at a45-degree angle.

• To prevent reentry of exhaust fumes into thebuilding, exhaust pipes must be located awayfrom air intakes.

• Use separate exhaust pipes for each engine.

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Gaseous exhaust emissions of diesel enginesare the lowest of modern internal combustionengines. Engine emissions are measured usinga Horiba or Beckman gas analyzer, with

equipment and data measurement techniquesconforming to the U.S. Code of FederalRegulations, Title 40, Part 53 or 86. Caterpillarengines at rated load will not exceed:

Nitr ogen oxidesare formed by decompositionand recombination of the molecular oxygen and nitrogen present in the combustion air.

• They consist primarily of nitric oxide andnitrogen dioxide.

• The designation of nitrogen dioxidesignifies 1 or 2 oxygen atoms can bepresent in the molecule.

• Generally, over 90 percent of nitrogendioxide in engine exhaust is in the form ofnitric oxide.

• The nitric oxide gradually oxidizes to themore harmful nitrogen dioxide in theatmosphere.

• Nitrogen dioxide is a poisonous gas which,when combined with hydrocarbons in thepresence of sunlight, forms smog andozone.

• By convention, the nitrogen dioxide massemissions (such as grams/hour) are usuallyreported as equivalent mass of nitrogendioxide.

Nitrogen dioxide emissions in parts permillion by volume can be approximated fromthe mass emission rate and the exhaust flow:

Depending on configuration and rating, manyengines emit considerably less emissions.Specific emission data is available from theengine supplier.

EmissionDiesel Natural Gas

g/bhp-h NA TA TACatalytic Low Converter Emission

Nitrogen Oxide (NOx) 12.0 15.0 19.0 1.2 2.0

Carbon Monoxide (CO) 3.5 2.0 1.5 1.0 1.7

Hydrocarbons (NMHC) 0.4 1.5 1.5 0.5 0.35

NO concentration = 629 x

where:

NO concentration is in parts per million (ppm)NO mass emissions are in g/hr of equivalent NO

NO mass emissions(exhaust mass flow)

xx

x

x 2

Exhaust flow is in kg/hr

EMISSIONS

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Carbon monoxide(CO) is poisonous and isformed by combustion that takes place with ashortage of oxygen. CO emissions in parts permillion by volume is calculated by:

Carbon dioxide is not regulated in most areasbut is considered a greenhouse gas. It is theresult of combustion of all hydrocarbon fueledengines, including humans. Carbon dioxide isa function of engine efficiency, with highefficiency engines producing the lowest carbondioxide.

Hydr ocarbons(HC) consist of unburned fuelor lubricating oil, and can cause unpleasantodors and eye irritation. HC emissions in partsper million by volume is calculated by:

Particle emissionsinclude unburned carbon(soot), soluble organic fraction (SOF), andsulfates.

• There is no universally accepted measuringmethod for non-truck application, so thelevel of particle emissions depends on themeasuring method.

• Caterpillar has developed a correlationbetween smoke and particulate concentrationwhich can be used to estimate particulateemissions.

Black smokeresults from incompletecombustion and is the soot portion ofparticulates.

White smoke is caused by vaporized butunburned fuel passing through the engine, andusually occurs during startup of a cold engine.

The sulfur present in the fuel oxidizesprimarily to sulfur dioxide, with less than twopercent forming sulfate. The emission of sulfurdioxide depends only on the sulfur level of thefuel and the fuel consumption rate of theengine. Sulfur dioxide emissions are calculatedby:

Aldehydes can cause eye and respiratoryirritation, but levels are quite low for mostengines.

Emission levels are affected by engine rating,speed, turbocharger, timing, fuel, and ambientconditions. Increased intake air temperatureand higher altitudes increase nitrogen dioxideand particulate emissions.

HC concentration = 2067 x

where:HC concentration is in parts per million (ppm)HC mass emissions are in g/hr Exhaust flow is in kg/hr

Particulates and sulfur dioxide levels are also sometimes required.

HC mass emissionsexhaust mass flow

Specific SO = (0.01998) (BSFC) (% sulfur in fuel)

where:Specific SO is emissions in g/kW-hrBSFC is Brake Specific Fuel Consumptionin g/kW-hrPercent sulfur in fuel is in percent by weight

2

2

CO concentration = 1034 x

where:CO concentration is in parts per million (ppm)CO mass emissions are in g/hr Exhaust flow is in kg/hr

CO mass emissionsexhaust mass flow

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Heat Balance

Internal combustion engines produce heat as aby-product of combustion. Twenty to fortypercent of fuel energy required for engineoperation results in heat rejected to the jacketwater, and must be totally removed by theengine’s cooling system to assure dependableengine performance.

• The cooling system is comprised of thejacket water circuit and, depending onengine configuration, aftercooler, oil cooler,and fuel cooler circuits.

• A small percentage of heat is also rejected tothe atmosphere, and is removed by engineroom ventilation.

The distribution of input fuel to energy isapproximately:

• 33% to useful work

• 30% to rejected work

• 30% to jacket water

• 7% to friction and radiation

Engine cooling systems must:

1. Cool jacket water at greatest engine load,highest ambient temperature, and altitude

2. Allow filling without air entrapment

3. Provide sufficient pressure head todiscourage pump cavitation

4. Vent air introduced into the system byfilling, leaks, and engine combustion

There are three primary areas to consider inengine cooling:

• Internal engine coolant flow

• Types of internal cooling systems

• Jacket water and separate circuit aftercooling

Internal Cir cuit

The engine thermostat controls minimumoperating temperature of the engine. It permitsefficient engine operation by disconnecting theexternal cooling system until jacket watertemperature exceeds 79° C (174.2° F).

COOLING

30-40%

7%

33%20-40%

Pump

Thermostat Closed

COOLANT FLOW

Pump

ToCooling

FromCooling

Thermostat Open

31


• After the engine jacket water reachesapproximately 80° C (176° F), thethermostat begins to open and allowscirculation to the external cooling system.

• Never operate without thermostats whenutilizing the normal 88° C (190° F) coolingsystem. Optional thermostats are availablefor applications requiring higher minimumoperating temperatures.

Outlet regulated cooling systemsprovide aconstant outlet temperature from the engine byregulating the flow between the bypass andcooling circuits. Usually applied with radiatorcooled systems, the sensing bulb is placed inthe outlet flow from the engine. Note that allCaterpillar EPG radiator cooled systems use anoutlet regulated cooling system.

Inlet r egulated cooling systemsprovide aconstant temperature to the inlet jacket water,aftercooler, and/or oil cooler. This design isused to minimize overcooling when very coldor large cooling sources are involved. Thesensing bulb of the thermostat is placed in theinlet flow to the engine. The thermostat thenbalances the bypass flow (hot water directlyfrom engine) with cool water from a heatexchanging device.

A potential problem with inlet controlledcooling incorporating a radiator is that fullpump pressure is imposed on the radiator core.This pressure usually exceeds the structuralpressure of a solder tube radiator core.Therefore, inlet controlled systems are notoften used with radiators.

Types of Cooling

There are two basic types of cooling systems,one of which is an open system.

In an open system, untreated water is used tocool the engine. This cooling process canresult in scale buildup, corrosion, and erosionin the internal cooling water passages,decreasing the cooling system’s efficiency andendangering the engine’s service life.

Caterpillar recommends a closedcoolingsystem. In a closed system, cooling mediumdoes not come into direct contact with air, butis cooled by a process of heat transfer, usuallywater or air (example — radiator).

Water Treatment

Prime consideration in closed cooling systemsis to ensure no corrosion or scale forms at anypoint. Select the best quality water available,but never use salt water.

Usually water hardness is described in grainsper gallon – one grain being equal to 17.1 partsper million (ppm), or in mg/L, both expressedas calcium carbonate. Water containing up to3.5 grains per gallon (60 ppm) is consideredsoft and causes few deposits.

Usable water must have the followingcharacteristics as defined by industry standardspecification ASTM D4985:

pH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.5-9.0

Chloride . . . . . . . . . . . . . . . . . . . . . . . . .40 ppm2.4 grains/gal

Sulfate. . . . . . . . . . . . . . . . . . . . . . . . . .100 ppm5.9 grains/gal

Total Dissolved Solids. . . . . . . . . . . 340 ppm20.0 grains/gal

Total Hardness. . . . . . . . . . . . . . . . . . 170 ppm10.0 grains/gal

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Water softened by removal of calcium andmagnesium is acceptable.

• Never use water alone as a coolant. Coolantadditives are required because water iscorrosive at engine operating temperatures.

- Corrosion inhibitors added to water orantifreeze solution maintain cleanliness,reduce scale and foaming, and provide pHcontrol.

- A 3 to 6 percent concentration of inhibitoris recommended to maintain a pH level of8.5 to 10.

- Soluble oil damages hoses, gaskets, andseals, and does not lubricate pumpbearings, or protect from cavitationerosion. Avoid sudden changes in coolantcomposition to minimize failure ofnonmetallic components.

- Caterpillar cooling inhibitor is compatiblewith ethylene glycol and propylene glycolbase antifreezes, but not with Dowtherm209. With 30 percent glycol, no additionalinhibitors are required.

Following are some main points of watertreatment:

• To maintain constant protection, additivesshould be replenished every 250 operatinghours.

• Because modern antifreezes containconsiderable dissolved chemical solids toaccommodate aluminum components, over-concentration needlessly reduces heattransfer and causes water pump seal leakageor failure.

Note: If cooling water contacts domestic watersupplies, water treatment may be regulated bylocal codes.

• Engine cooling water for high temperaturewater systems is circulated within the enginewater jacket at temperatures above 100° C(212° F).

- High temperature solid water applicationshave the potential for steam to form.

- Minerals in the water can precipitate duringthe heating process and form depositswithin the cooling systems, restricting heattransfer and water circulation. The enginecoolant must therefore be treated the sameas boiler feed water.

The engine coolant (boiler water) is a mixtureof feed water and resident water. It should notexceed the following maximumconcentrations.

Silica concentration . . . . . . . . . . . . . . 150 ppmas silicon dioxide

Total alkalinity . . . . . . . . . . . . . . . . . . . 700 ppmas calcium calcium carbonate

Specific conductance. . . . . . . 3500 microhms per cm (2680 ppm)

pH . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10.0-11.5

In addition, the jacket water treatment shouldinclude:

- Maintenance to limit calcium carbonateequivalent of hydroxide alkalinity to200-400 ppm

- A blend of dispersants to condition andsuspend the precipitated solids

- Treatment of condensate return

COOLING

33


• Make-up water should not exceed thefollowing maximum concentrations:

Ir on. . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.1 ppmCopper. . . . . . . . . . . . . . . . . . . . . . . . .0.05 ppmTotal hardness. . . . . . . . . . . . . . . . . . . 0.3 ppm

as calcium carbonate

These stringent guidelines are based in part onestablished limits of the American BoilerManufacturer’s Association (ABMA) andrecommendations of the American Society ofMechanical Engineers (ASME) ResearchCommittee on Water in Thermal PowerSystems.

• Cooling towers supplying cooling waterdirectly to turbocharger aftercoolers mustalso incorporate treatment.

- A corrosion resistance core must bespecified and raw water treated withcorrosion inhibitors and protected fromfreezing.

- Algae formation severely affects heattransfer rates and must also be controlled.

Antifr eeze ProtectionExposing engine coolant to freezingtemperatures requires addition of antifreeze.Ethylene glycol, Dowtherm 209 (sold at 20%),or Cat ELC (sold and recommended at 50%)are recommended to protect against freezingand inhibit corrosion. Borate-nitrite solutionssuch as Caterpillar Inhibitor or NALCO 2000are compatible only with ethylene glycol andcan replenish the original corrosion inhibitorsin the antifreeze.

• The glycol concentration should exceed30 percent to assure protection againstcorrosion and minimize water pumpcavitation, but concentration above60 percent will needlessly penalize heattransfer capabilities.

• Generally, a radiator derates 2 percent foreach 10 percent of antifreeze concentration.

• Use of antifreeze year-round decreasesradiator capabilities at least 3.3° C (6° F).

Radiator Cooling

Radiator cooling is the most common andreliable method used to cool engines. As withall cooling systems, radiators are usually sized15 percent greater than the engine’s maximumfull load heat rejection. This allows foroverload conditions and system deterioration.

Temperature DifferentialMost engines operate with water temperaturedifferential (outlet minus inlet) of 5.5° to8.3° C (10° to 15° F) maximum. Temperaturelimitation of water leaving the engine isdetermined by cooling system design. Instandard systems operating with 27.6 to48.2 kPa (4 to 7 psi) pressure caps, maximumtop tank temperature is 99° C (210° F). Thislimit prevents steam formation in the enginewater jacket. The drawing below illustrates theeffect of system pressure on the boiling pointof water at various altitudes.

COOLING

Pump

90.5¡ C (195¡ F)

96.1¡ C (205¡ F)

Thermostat Open

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System PressureSlight system pressure minimizes pumpcavitation (voids in water) even at highaltitude, and increases pump efficiency.

• For each 6.9 kPa (1.0 psi) of pressure, theboiling point is raised about 2° C (3° F).Elevations above 3048 m (10,000 ft) requirehigher rated pressure caps to avoid boiling.

• Additions of alcohol or other volatileantifreeze coolants lower the boiling point,while ethylene glycol solutions raise theboiling point.

Engine Mounted RadiatorSystem DesignJacket water flow is determined by engine heatrejection and allowable jacket watertemperature rise.

• Minimum temperature rise is desirable toreduce thermal stresses, but water flows arelimited to reduce erosion and pumphorsepower requirements.

• Watercooled exhaust manifolds increase heatrejection 15 percent over dry manifolds, andmay affect turbocharger performance,causing power deaerations.

• Exact power ratings and configurations arenecessary when calculating heat rejection.

Water flow rates in external cooling systemsare calculated by:

Pure Water 50/50 Glycol

Density kg/L at 80° C= 0.98 1.03

(Ib/gal) at 175° F= 8.1 8.6

Specific Heat (kW-min/kg-°C)= .071 0.06

(Btu/Ib-°F)= 1.0 0.85

dT = Allowable temperature rise, °C, °F

• Piping and heat transfer equipment resistjacket water flow, causing an externalpressurehead which opposes the engine-driven pump.

- Jacket water flow reduces as external headincreases.

• To ensure adequate coolant flow, externalhead losses must be balanced against waterpump capabilities.

- Excessive external heads demand pumpswith additional pressure capacity.

- Friction head losses are a function of pipesize, number and type of fittings andvalves used, coolant flow rate, and lossescontributed by heat transfer devices.

- After determining required coolant flowrate, pump performance establishesmaximum allowable external head.

COOLINGFlow (L/min) =

Flow (gal/min) =

Heat Rejection (kW)

dT (¡C) x Density (kg/L) xSpecific Heat (kW-min/kg-¡C)

Heat Rejection (Btu/min)

dT x Density (Ib/gal) xSpecific Heat (Btu/Ib-¡F)

COOLING SYSTEM PRESSURE

BOILING POINT OF WATER

ALTITUDEMeters

430037003000240018001200600

0

Feet14 00012 00010 000

8000600040002000

Sea Level¡Fahrenheit¡Centigrade

18082 88 93 99 104 110 115 121

190 200 210 220 230 240 250

00.0

40.3

100.7

psikPa

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• Coolant velocity is maintained to achieveoptimum heat transfer without damage tosystem components by erosion.

- Jacket water external circuit velocities of0.6 to 2.5 m/s (2 to 8 fps) are acceptable.

- Raw or sea water circuit velocities reduceto 0.6 to 1.9 m/s (2 to 6 fps).

Water Maximum Velocity

m/sec ft/secpressurized lines 4.5 15

pressurized thin-wall tubes 2.5 8

suction lines (pump inlet) 1.5 5

low velocity deaeration line 0.8 2

• Radiators may contain orifices to limitcoolant flow, so flow in engines withradiators may be less than in those withoutradiators.

- Because published pump data reflectscoolant flow without a radiator, auxiliarycooling equipment installed with standardradiators must anticipate flows lower thanpublished.

Pressure relationships:

• Pressure drop and velocity of liquids iscalculated in EPG Designer, while bothpressure drop and velocity are estimated inthe Generator Set A&I Guide. For example,new 6-inch steel pipe carries 2270 lpm ofwater at 66° C (600 gpm at 150° F).

• If a high capacity pump is installed in serieswith the standard engine pump, total pressurehead imposed on the engine pump inlet mustbe less than 1172 kPa (25 psi).

- External system modifications may benecessary to prevent cavitation of the highcapacity pump.

• Consult manufacturers’specification sheetsfor friction head loss through heat transferdevices.

- Decrease resistance by minimizing numberof bends.

- Use long sweep elbows and gate-typevalves.

• Suction head on the pump must not besignificantly below atmospheric pressure.

• Inlet piping should have internal diameters atleast the diameter of that furnished on theengine.

• Radiator bottom tank must have greatercross-sectional area than inlet piping.

- Depending on the coating thickness,radiator capability will be reduced at least3 percent.

• Coatings such as solder or paint aresometimes used to protect the copper fins ofthe radiator core from aggressiveatmospheres.

• Altitude affects radiator sizing.

- Increased air flow is required at higheraltitudes to maintain cooling capabilitiesequivalent to sea level.

- Reduce radiator performance 1.4° C per 305 m (2.5° F per 1000 ft) of elevation tocompensate for lower air densities.

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Top Tank

Radiators normally have top tanks for filling,expansion, and deaerating of engine coolant.Extended systems using added coolant mayrequire enlarged expansion tanks.

Installation

• When an engine-mounted radiator is usedand the generator set is installed in a room, ablower fan and a radiator duct running to theoutside can be used.

- Ducts directing radiator air to the outside prevent recirculation and high equipmentroom temperatures.

- Some generator set packages have standardradiator duct flanges for installation ease.

- The duct length is short and direct tominimize backpressure, with total inlet andoutlet restriction on the radiator fan beingless than 6.35 kPa (0.25 in. H2O).

- Radiator ducting should be larger than theradiator core, with inlet air ducts 1.5 timesgreater than outlet ducts.

Restrictions

• When louvers are used, the duct size shouldbe increased at least 25 percent due to louverassembly restrictions.

• If common window screening is used, thesize of the opening may increase 40 percent.

• Solid walls perpendicular to fan air flowmust not be closer than 2 fan diameters fromthe radiator.

• Avoid uneven loading of the fan caused byobstructions or auxiliary coolers partiallyobstructing air flow.

• Fatigue failure of fan blades as well as airturbulence may occur when obstructions arewithin 150 mm (6 in) of the fan face.

Movable Louvers

If movable louvers are used, specify thosewhich open in a positive manner. Pneumaticand electric-actuated louvers are satisfactory.

Louver Operation

• Louvers which open from the dischargepressure of the radiator fan are discouraged.

• Rain, ice, and snow can render theminoperative within a short time and result inengine overheating and shutdown.

COOLING

37


• Do not wait to activate the louvers until theengine warms up. In an emergency, theengine will be loaded immediately andrequire full air flow.

• Heat sensors needlessly complicate thesystem and their malfunction can reduce airflow to the engine and cause shutdown.

• Open louvers as soon as engine starts.

• Don’t use heat sensors.

Enclosures

Enclosures trap radiated heat and direct itthrough the radiator decreasing coolingcapabilities 8° to 10° C (14° to 18° F). Evenwith doors open, radiators can derate 5° to7° C (9° to 13° F).

Remote Mounted Radiators

The radiator may be located some distancefrom the engine.

• Remote-mounted radiator systems addrestriction to cooling water flow byadditional piping.

• The standard engine coolant pump may beunable to provide adequate flow, so it mayhave to be replaced or boosted by anadditional pump usually located in theengine return line. (The auxiliary pumpoperates whenever the engine is running.)

• Allowing engine warmup before pumping toremote radiator can cause the radiator core tofail due to thermal shock.

- If the empty radiator is exposed to extremecold, initial flow of unprotected coolantcan freeze and block the core. Antifreezemust be included in the water treatment toassure uninterrupted flow.

Vertical remote radiatorsare positioned soprevailing winds or structures do not impedefan air flow or cause the heated air torecirculate through the radiator core.

Horizontal r emote radiatorsnullify theeffects of wind but may require protectionfrom snow and ice.

Static Head

Static head is the maximum height the coolantwater is raised.

• Large static heads are encountered whereradiators or heat exchangers are located onthe roof.

• Heights above 17.4 m (57 ft) cause leakageat the engine pump seals.

• Brace pipes at bends and use Marmon (orequal) clamps.

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• High static head and movement in long piperuns cause straight clamped rubber hoses toleak. A separate external cooling systemrelieves the engine system from thispressure.

• Automatic make-up water controls and lowwater alarms are desirable in remote systemsto avoid inattention.

• Radiators mounted level or above engineand connected with straight piping willavoid air traps.

• The engine outlet pipe, which dips below theengine, will trap air during initial fill orcombustion gases which leak into thecoolant.

• If piping dips are unavoidable, vent linesfrom each potential trap run to the radiatortop tank.

• Vent lines must also slope up with no dips.

While preferable in installations involvingmultiple generator sets to provide separatecooling systems for each engine, using a singleradiator is possible. Such designs must beanalyzed by a cooling system engineer.

Location

• When selecting radiator location, considerfan noise.

- Noise transmits through the air inlet aswell as outlet.

- Soft flexible joints between radiator andduct will reduce vibration and noisetransmission.

• Position the radiator so prevailing winds donot act against the fan.

- One form of wind protection for radiatorsis a baffle set several feet from the exhaust.

- Another method is to install an air ductoutside the wall directing the air outlet (orinlet) vertically.

COOLING

17.37 m(57 ft)

Radiator

Expansion Tank

Jacket WaterPump

39


Air Density

Air density, flow restrictions, and speed affectfan performance, possibly limiting radiatorambient temperature capabilities. Performancechanges are estimated by these relationships:

Speed

Fan speed affects the performance of a fan inrespect to radiator ambient temperaturecapabilities. Revised air flow, static pressure,and fan horsepower can be calculated usingrevised and original fan speeds.

TemperatureRevised coolant temperature and radiatorambient capabilities are calculated as shown.

Radiator Ambient Capability =Rad Top Tank, usually 99° C (210° F) - Revised Coolant Temperature

where:

Air Density = kg/cu cm (Ib/cu in)Air Flow = cu m/min (cfm)Coolant Temperature =

99° C (210° F) – (5.5) – Original Radiator 2Ambient

Assumptions: Coolant Top Tank Temperature =

99° C (210° F)Inlet to Outlet Radiator Temperature

Change = 5.5° C (10° F)Fan Horsepower = kW (hp)Fan Speed = rpmStatic Pressure = mm (in) of H2O

Heat ExchangerCooling

A heat exchanger is sometimes used to coolthe engine when ventilating air is limited orexcessive static head on the engine must beavoided. Caterpillar exchangers are all shelland tube-type.

COOLING

Revised Coolant Temperature =Original Coolant Temperature x

Original Air Flow

Revised Air Flow

0.7( )

Revised Coolant Temperature =Original Coolant Temperature x

Original Fan Speed

Revised Fan Speed

0.7( )Revised Static Pressure =

Original Static Pressure xRevised Air DensityOriginal Air Density

Revised Fan Horsepower =

Original Fan Horsepower xRevised Air DensityOriginal Air Density

Original Air Flow x Revised Fan SpeedOriginal Fan Speed

Revised Static Pressure =

Original Static Pressure x

Revised Fan Horsepower =

Original Fan Horsepower x

Revised Fan SpeedOriginal Fan Speed

2

( )Revised Fan SpeedOriginal Fan Speed

3

( )C

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Advantagesof heat exchangers include:

• No fan noise

• Reduced air flow requirement

• Minimum space requirement

• Less parasitic load, improving fuelconsumption

The disadvantagesof heat exchangersinclude:

• A separate cooling source

• A separate expansion tank

• An extra pump and plumbing

• Room ventilation

DesignShell and tube heat exchangers are single- ortwo-pass. This refers to the flow in the rawwater circuit of the exchanger.

• Multi-pass exchangers flow raw waterthrough the exchanger two or more times. Inmulti-pass exchangers, relative direction offlow betweenjacket and cooling water isunimportant.

• Single-pass types use raw water only once.Raw water in single-pass exchangers flows through the exchanger opposite to coolantflow to provide maximum differentialtemperature and heat transfer. This results inimproved heat exchanger performance.

• Heat exchanger performance depends on rawwater flow and differential temperature.

- To reduce tube erosion, flow of raw water through the tubes should not exceed2.4 m/s (8 fps).

- Minimum flow rate for good heat transferdesign is 1.2 m/s (4 fps).

- The heat exchanger must accommodateraw water temperature and flow needed toremove maximum engine heat rejection.

- Thermostats are retained in the jacketwater system to provide adequate lowtemperature control.

• Heat exchangers must accommodate heatrejection 10-15 percent greater than enginefull load heat rejection, depending on foulingfactors.

- Standard Caterpillar exchangers incorporatea 0.001 hr-ft °F/Btu factor. Fouling factoraffects heat transfer by the followingrelationship:

where:

FF = fouling factor, Btu/h ft °F/U coolant = heat transfer coefficient of core

with coolant, Btu/h ft2 °FU clean core = heat transfer coefficient of clean

core, Btu/h ft2 °F

COOLING

Jacket Water

Cooling Water

Single Pass

Two-Pass

HEAT EXCHANGER TYPES

Jacket Water

FF = 1U coolant U clean core

1

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• Solenoid valves controlling cooling water areapplied upstream of the heat exchanger.

• Since heat exchanger tubes can be cleanedmore easily than the surrounding jacket, rawwater usually is routed through tubes andengine coolant through the shell. Strainersprevent premature system fouling.

- The exchanger is relieved of pressure wheninoperative and raw water cannot betrapped in the tubes if the solenoid fails toopen.

- Water trapped during engine operationexpands and can rupture the exchanger.

- All solenoid valves include manualbypasses.

• Do not add temperature regulators in rawwater supplies. Engine jacket water isthermostatically controlled and additionalcontrols add expense, cause restriction, anddecrease reliability.

Installation• Always use flexible connections on water

lines to prevent transmission of enginevibration to the heat exchanger.

• Limit total system volume by mounting theheat exchanger close to the engine.

Expansion TanksUnlike radiators, heat exchangers have nobuilt-in provision for jacket water expansion.Surge (expansion) tanks must be included inheat exchanger systems. Factory-designedtanks are normally specified to assure properperformance of the total system.

Design• Water expands about five percent between

0° and 100° C (32° and 212° F).

- Expansion tanks should have capacity forat least 15 percent of system water volumefor expansion, plus reserve.

- Tanks vent to atmosphere or incorporatepressure caps to assure system pressure.

- Tanks are located to prevent formation of avacuum, a primary cause of cavitation onthe suction side of the pump.

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• Deaerate jacket water to prevent formationof air pockets and minimize pump cavitation.

- Entrained air encourages corrosion anderosion in the engine.

- Coolant may be lost because air expandsmore than water when heated.

- Entrained air is caused by air trappedduring fill operations, combustion gasesleaking (five percent per cu indisplacement), leaks in piping (particularlyon the inlet side of the pump), or low after-level in the expansion tank.

- A low velocity area must be providedwhere deaeration can occur.

- Entrained air separates from the water ifthe tank is sized and baffled to slow waterflow to 0.6 m/s (2 fps).

If full flow is not directed to the expansiontank, a 10 mm (3/8 in) deaeration line to theexpansion tank can be run from an enlargedcross-section of the return water line.

Expansion tanks are the highest point in thecircuit. The heat exchanger mounts lower thancoolant in the expansion tank, preferablyseveral feet. Jacket water flows from engineoutlet to heat exchanger, to expansion tank,and back to jacket water pump inlet. Thispurges air and creates positive pressure at thejacket water pump inlet. If the heat exchangeris remote mounted, locate in a minimumvibration area, with flexible fittings betweenheat exchanger and engine.

Cooling System Features

The various features of a cooling systemensure that the cooling system runs properly,in turn, aiding the performance of the entiregenerator set.

Hot WellHot well systems are used when static headexceeds 17.4 m (57 ft.), or a boost pumpimposes excessive dynamic head. Theauxiliary pump operates whenever the engineis running. Allowing engine warmup beforeengaging the pump can cause the radiator coreto fail due to thermal shock.

If the empty radiator is exposed to extremecold, initial flow of coolant can freeze andblock flow in the core. Antifreeze must beincluded in the water treatment to assureuninterrupted flow.

Mixing TanksA 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.

A tank sized for 110 percent of radiator andpiping coolant ensures that pumps will notsuck air and that water level can be checkedduring shutdown.

TurbochargingTurbocharging compresses combustion aircharge, but this compression increasestemperature, limiting the benefits ofturbocharging. Lowering intake air temperaturethrough jacket water aftercooling furtherincreases the density of air for combustion.

COOLING

43


The resulting increase in oxygen allows morefuel to be burned, which produces greaterengine power. Improved combustion can alsolower:

• Brake Specific Fuel Consumption (BSFC)

• Exhaust temperature

• Certain exhaust emissions

Separate Circuit After cooling (SCAC)Separate circuit aftercooling removes theaftercooler from the jacket water circuit andprovides aftercooler cooling from anindependent source. While jacket watertemperature to aftercooler approaches 88° C(190° F), a separate source provides muchcooler water, allowing air charge temperatureto be further reduced, which improves engineperformance.

• SCAC is necessary on all turbocharged gasengines and high temperature jacket watersystems used in heat recovery applications.

• A closed cooling circuit, such as a heatexchanger or radiator, is preferred to controlwater quality.

• If supplied from an open system, such as acooling tower or pond, the aftercooler coreand associated plumbing must be non-corrosive and cleanable.

• Cooling tower water should be treated withcorrosion inhibitors and protected againstfreezing.

• Separate circuit aftercooling generallyimproves operating performance of allturbocharged engines, but gas enginesMUST have a separate cooling source.

- Cooling water temperature less than 54° C(130° F) is required to maintain proper(full) engine/generator power ratings andemission levels and to avoid detonation ofthe fuel mixture.

- Split or dual core radiators will usuallyprovide 54° C (130° F) coolant.

- Lower water temperatures or air-to-airaftercooling will allow even greaterperformance.

Air -to-Air AfterCooling (ATAAC)ATAAC is an optional cooling medium used toachieve low charge air temperatures. Thecharge air is routed to the heat exchangerwhile ambient air driven by the radiator fanpasses across the external surface. Aftercoolerheat rejection, charge air flows, and pipingrestrictions require analysis to avoidcompromising engine performance.

COOLING

Inlet Temperature Range For Aftercooling:32¡ C (90¡ F) to 54¡ C (130¡ F)

SEPARATE CIRCUIT AFTERCOOLING (SCAC)

EngineJW Out

JW ReturnA/C

Generator

1 2 3

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Recovery design for any installation dependson several technical and economicconsiderations. The primary function of anyheat recovery system is to cool an engine orgroup of engines. Provisions must be made toensure engines operate at correct temperatures,even when plant heat demands are small.

Fuel is the largest operating expenseassociated with a generator set.

In typical prime power applications, fuel costsover a ten-year cycle can range from 75 to85 percent of total operating costs. Therefore,in installations where heat can be recoveredand used, it is possible to increase total energyoutput per dollar and yield significant savings.

Reciprocating engines convert about 30 to37 percent of their input fuel energy intomechanical power. The remainder transformsinto heat and is carried from the engine byjacket water, exhaust, and radiation.

• The 20 to 40 percent of generator set heatcontained in jacket water can be totallyrecovered.

• About half of the 30 to 40 percent carried bythe exhaust is economically recoverable.

• Total heat recovery results in fuelefficiencies approaching 80 percent.

HEAT RECOVERY

Purchase Price& Associated Costs

Downtime & Associated Costs

Component Repairs & Overhauls

FuelOther Fluids& PreventiveMaintenance

GENERATOR SET OPERATING COSTS

USING HEAT RECOVERY

Recovered

45


Heat recovery may be as simple as utilizingheat from the engine radiator. Air passingthrough the radiator core of a loaded enginehas a temperature of 38-65° C (100-150° F),and is suitable for:

• Drying

• Space heating

• Preheating boiler combustion air

Recovering radiator heat requires nomodification of standard engine equipment,with overall efficiency approaching 60 percent.

Types of Heat RecoveryHeat recovery methods are grouped as follows:

• Standard Temperature [93° C (200° F)]

• High Temperature [127° C (260° F)]

- Solid Water [127° C, 137.4 kPa (260° F, 20 psi)]

- Ebullient Steam [121° C, 103.4 kPa (250° F, 15 psi)]

Standard Temperature HeatRecovery

This approach uses a shell and tube heatexchanger to transfer the heat of normal jacketwater [temperatures about 93° C (200° F)] to asecondary circuit — usually water.

The typical heat recovery system involvingstandard temperature jacket water includesstandard engine equipment. Plant hot water istaken from the secondary side of the heatexchanger. After warmup, the regulator allowsflow to the plant load heat exchanger.

Expansion Tank LocationIdeally, all flow passes through the expansiontank to promote deaeration.

The added external head of the extended jacketwater circuit may exceed the allowable headon the engine mounted pump, so an auxiliarypump may be necessary.

The amount of heat available is dependent onthe mechanical load on the engine, so, in timeswhen electrical loads are light but plant heatloads are high, an additional heating source(boiler) may be necessary. If heating loads aresometimes low when electrical loads are high,a load balancing heat exchanger should beincorporated.

HEAT RECOVERY

38¡ to 65¡ C(100¡ F to 150¡ F)

TYPICAL HEATRECOVERY APPLICATIONS

• preheating boiler combustion air• space heating• drying processes

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An exhaust heat recovery muffler may beadded to the system as a separate water circuitor in series with the jacket water. As a separateheat source independent of the jacket water,the muffler water circuit can produce hightemperature water or steam.

• The amount of heat available is highlydependent on engine load.

• Coolant must flow through the heat recoverydevice whenever the engine operates toavoid thermal shock.

Muf fler Heat Recovery

Heat recovery mufflers economically recoverabout half the engine exhaust heat. Exhaustexit temperature above 149° C (300° F)discourages condensation in ducting. For eachgallon of diesel fuel burned, a gallon of wateris carried into the exhaust.

Recoverable heat data is obtained from theengine manufacturers but can be estimated by:

HEAT RECOVERY

Heat

Exhaust

Jacket Water

Recovered

HEAT RECOVERY

Q = CpM (T1-T2) where:

Q = Recoverable Heat (KJ/h)Cp = Specific Heat Diesel Engines – 1.081 KJ/kg per ¡C Gas Engines – 1.170 KJ/kg per ¡C

T1 = Exhaust Gas Stack Temperature (¡C)T2 = Exhaust Gas Exit Temperature (¡C)M = Exhaust Mass Flow (kg/h)

M = M /min x 60 x 353.0

T1 (¡C) + 273¡ C

3

M = Exhaust Flow (cfm) x 60 x 39.6

T1 (¡F) + 460¡ F

Q = CpM (T1-T2) where:

Q = Recoverable Heat (Btu/hr)Cp = Specific Heat Diesel Engines – 0.258 Btu/Ib per ¡F Gas Engines – 0.279 Btu/Ib per ¡F

T1 = Exhaust Gas Stack Temperature (¡F)T2 = Exhaust Gas Stack Temperature (¡F)M = Exhaust Mass Flow (Ib/h)

OR

47


Muf fler/Jacket Water in a SeriesPlacing the muffler in series with the secondaryside of the jacket water heat exchanger adds theheat rejection of the two systems into a singlesource. The additional heat from the mufflerdemands a larger load balancing device thanwith the jacket water alone.

• Removal of engine thermostats and blockingwater bypass prevents sudden thermal shockof coolant on hot muffler surfaces.

• An external regulator directs coolant backthrough the engine and the heat recoverymuffler.

• When heat available from the engine andmuffler exceeds plant heating requirements,an additional cooling source is added to thesystem to accommodate both jacket waterand muffler heat.

1 2 3

Generator

Engine

Expansion Tank



To Load

From Load

LoadHeat Exchanger


Valve

STANDARD TEMPERATURE WATER SYSTEMWith Series Exhaust Heat Recovery

A/C

CirculatingPump

JacketWaterPump

Separate CircuitCooling

Load BalancingHeat Exchanger


Excess FlowBypass Valve

To RemoteCooling Device

JW HeatExchanger

HEAT RECOVERY

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Water-Steam Circuit Heat Recovery SystemThe heat recovery muffler can be included inthe system as a separate water-steam circuitfor loads requiring high temperatures — inexcess of 99° C (210° F).

In hospital applications, for example,absorption equipment may require 93° C(200° F) water, while sterilization equipmentmay require water-steam in excess of 99° C(210° F). The engine jacket water systemcould be used for the absorption equipment,and the exhaust heat recovery system for thesterilization equipment.

Here’s how it works:1. Water-steam flows through the exhaust heat

recovery device to the steam separator.

2. Load demands determine valve pressures.

3. The pressure control valve regulatespressure within the steam separator.

• The relief valve should be set at least 6.9 kPa (1 psig) above the pressure control valve setting.

• The excess steam valve is set equal to or less than the pressure control valve setting.

4. As steam is absorbed by the load, itcondenses to a liquid state, flows throughthe condensate tank, and is pumped back tothe steam separator.

• To avoid thermal shock on hot muffler surfaces, a low water flow shutdown device ensures constant coolant flow through the muffler.

HEAT RECOVERY

ExhaustHeat

RecoveryDevice

SEPARATE CIRCUIT EXHAUST HEAT RECOVERY SYSTEM

CondensatePump

CondensateTank

AirEliminator

CondensateFrom Load

Steam To Load

ExcessSteamValve

Pressure ControlValveRelief Valve

Steam Separator

Water LevelControl

To RemoteCooling Device

Make-up Water

LowWater LevelShutdown

Load BalancingCondenser

49


Design Criteria — Standard TemperatureHeat Recovery SystemsCertain requirements are necessary for properoperation of a standard temperature heatrecovery system. The following is not,however, an all-inclusive list. An engineershould be consulted for specific installations.

• The system must provide adequate coolantflow through the engine so the enginecoolant temperature differential (outlet minusinlet) does not exceed 8.5° C (15° F).

• The expansion tank must be the highestpoint in BOTH the engine and load loopcooling systems. Locate the jacket water heatexchanger as near the engine as possible.

• Only treated water should be used in theengine cooling circuit.

• Incorporate air vents to eliminate air trapsand locks.

• A load balancing thermostatic valve must beused to direct coolant through a secondarycooling source to limit jacket water inlettemperature.

• Coolant must continually flow through theexhaust heat recovery device whenever theengine is operating to avoid thermal shockon hot muffler surfaces. This can beaccomplished by using a low water flowshutdown device.

High Temperature Heat Recovery

Types of high temperature heat recoverysystems include:

• Solid water system

• Ebullient system

• Water-steam system

High Temperature Heat Recovery SystemDesignElevated jacket coolant temperatures [99° to127° C (210° to 260° F)] recorded at engineoutlet require higher system pressure toprevent flashing to steam. Operating pressuresare normally 27.6 or 34.5 kPa (4 or 5 psig)above the pressure at which steam forms. Thesource of this pressure may be a static headimposed by an elevated expansion tank, orcontrolled pressure in the expansion tank.

HEAT RECOVERY

ExhaustHeat

RecoveryDevice

1 2 3

Generator

EngineTo Load

From Load



Valve

STANDARD TEMPERATURE WATER SYSTEMCritical Design Criteria

A/C


Engine MountedExpansion Tank

Thermostat

To Load

From Load

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• For 127° C (260° F) water temperature,engine pressures are approximately 138 kPa(20 psig).

• Pumps suitable for elevated temperaturesand pressures replace conventional enginejacket water pumps.

• High temperature engine operation requiresseparate cooling circuit for oil cooler andaftercooler.

Separate Circuit Oil Cooler/After coolerTo ensure proper cooling in all types of hightemperature systems, the engine oil cooler(heat exchanger) and aftercooler require acooling water circuit separate from the enginejacket water.

• A thermostat in the oil system controlslubricating oil temperature to preventovercooling.

- The thermostat begins to open at 82° C(180° F), and oil leaving the cooler shouldnot exceed 88° C (190° F).

- The maximum allowable coolanttemperature to the oil cooler is 77° C(170° F).

• An external control valve is recommended toprevent oil gelling and ensure oil flowthrough the oil cooler.

- The valve will bypass coolant to theradiator until the coolant reaches correctoperating temperature.

• The standard water pump should be removedand replaced by a special high temperaturepump.

Load Balancing Cooling CircuitBelow is a schematic of a load balancingremote radiator cooling circuit. There is nowater flow through the load balancing heatexchanger when the load uses all thewater/steam provided.

In cold environments, to prevent water fromfreezing in the heat exchanger, an externalthermostatic control valve will bypass coolantto the radiator until the coolant reaches correctoperating temperature.

Solid Water SystemThe function of this system is similar to astandard temperature water system, exceptelevated jacket water temperatures [99° to 127° C (210° to 260° F)] are used.

• The standard engine thermostat and bypassare removed and replaced by an externalcontrol (warm-up thermostatic valve).

• A pressure cap must be provided in theengine coolant circuit to assure a pressure ofseveral kPa (psi) above the pressure at whichsteam forms.

HEAT RECOVERY

51


- The source of this pressure may be a statichead imposed by an elevated expansiontank, or controlled air pressure in theexpansion tank.

- For 127° C (260° F) water, pressure shouldbe about 172 kPa (25 psi).

• The standard jacket water pump must beremoved and replaced with one with hightemperature and pressure capabilities.

Design Criteria — High Temperature SolidWater SystemsThese design features are similar to thoserequired for a standard temperature system.Check with a consulting engineer for a morecomprehensive list.

• The system must provide adequate coolantflow through the engine so the enginecoolant temperature differential (outlet minusinlet) does not exceed 8.5° C (15° F).

• The expansion tank must be the highestpoint in the cooling system. Locate theengine coolant heat exchanger as close to theengine as possible.

• Only treated water should be used in thecooling circuit.

• Incorporate air vents to eliminate air trapsand locks.

• A load balancing thermostatic valve must beused to direct coolant through a secondarycooling source to limit jacket water inlettemperature.

• Coolant must continually flow through theexhaust heat recovery device whenever theengine is operating to avoid thermal shockon hot muffler surfaces. This may beaccomplished by using a low water flowshutdown device.

Unlike a standard temperature system, a highpressure system also requires:

• A pressure control for the engine coolantcircuit.

• Water pumps suited for use with elevatedtemperatures and pressures

• Engine oil cooler and aftercooler with acooling water circuit separate from enginejacket water

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ExhaustHeat

RecoveryDevice

1 2 3

Generator

Engine

To Load

Expansion Tank



To Load

From Load



Valve

From Load

HIGH TEMPERATURE WATER SYSTEMCritical Design Criteria

A/C

Oil/C

Circulating Pump



52

Ebullient System“Heat of vaporization” removes rejected heatfrom the engine. A pound of water atatmospheric conditions of 101 kPa and 16° C(14.696 psia and 60° F) gains 1122.3 Btu[970.3+(212-60) = 1122.3] duringvaporization. While ebullient installations arehighly successful when properly applied, thedifficulties involved in integrating the enginecooling system with the plant heating loaddiscourage widespread acceptance.

• Steam is not collected within the engine butmoves through the water passages mixedwith high temperature water.

• Thermal action carries the mixture to a steamseparator elevated above the engine.

• No jacket water pump is required with thissystem.

• While temperature differential between“water in” and “water out” is usually quitelow [1.1° to 1.7° C (2° to 3° F)], flow isassured by change in coolant density as itgains engine heat.

• Formation of steam causes coolant tobecome lighter and creates a pressuredifferential between water inlet and outlet.

A variety of heat recovery arrangements arepossible. The exhaust gas boiler, or muffler,and the steam separator can be combined intosingle “packaged” units — one package unitused for each engine. Other equipmentcombines exhaust gas boilers and steamseparators in single units which may include adirect-fired section to eliminate the auxiliaryboiler. Such units can each serve two engines,but to do so requires complex exhaust pipingwith a steam separator located above theengine.

Design Criteria — Ebullient Systems• To avoid excessive boiling within the engine

and the formation of steam pockets in waterpassages, engine coolant must be under astatic head of at least 55 kPa (8 psi), but thecombination of static and dynamic headmust not exceed 197 kPa (28.5 psi).

HEAT RECOVERY

HE

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CO

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ExhaustHeat

RecoveryDevice

EBULLIENT SYSTEM

CondensatePump

CondensateTank

AirEliminator

CondensateFrom Load

Steam To Load

ExcessSteamValve

13 psig

Pressure ControlValve

14 psigRelief Valve15 psig max

Steam Separator

Water LevelControl

To WasteCooling Device

Make-up Water


1 2 3

Generator

Engine


To Load

From Load

A/C

Oil/C

Low PressureShutdown

Min.StaticHeadReqd.


53


• The engine oil cooler and aftercooler requirea separate water circuit from engine jacketwater.

• The engine oil cooling system must beprotected against a sudden loss of pressure.

- Controls which limit a sudden pressuredrop to 21 kPa (3 psi) must be locatedbetween the separator loads.

• Coolant piping between engine and steamseparator must be installed so the flow ofcoolant (water and steam) will always beupward.

• Make-up water should be provided tocompensate for any loss in the system.

- This water should be treated and fed intothe condensate tank.

Water-Steam SystemThe high temperature water-steam system issimilar to the ebullient system with theaddition of a circulating pump to assurepositive flow. The circulating pump forces

water through the cylinder block and heads toflush steam bubbles that may form in theengine.

Next the mixture flows to a steam separator.The steam separator is similar to the one usedwith the ebullient system, except it is sized forlarger water flow.

The following pressures are representativevalues. The relief valve pressure 103 kPa(15 psi) is set by boiler codes. Pressure in theseparator is controlled by the pressure controlvalve. Once the pressure builds to 97 kPa(14 psi), the control valve will allow steam toflow. The actual steam pressure in the load lineis a function of load requirements. If the load isnot consuming steam, the pressure in the steamline will increase. Once pressure reaches 90 kPa(13 psi), the excess steam valve will open totransfer engine heat to the waste cooling device(load balancing condenser). Install the excesssteam valve downstream of the pressure controlvalve. If it is upstream, the pressure controlvalve may not function properly.

HEAT RECOVERY

ExhaustHeat

RecoveryDevice

HIGH TEMPERATURE WATER-STEAM SYSTEM

CondensatePump

CirculatingPump

CondensateTank

AirEliminator

CondensateFrom Load

Steam To Load

ExcessSteamValve

13 psig



Steam Separator

Water LevelControl

To WasteCooling Device

Make-up Water


1 2 3

Generator

Engine


To Load

From Load

A/C

Oil/C

Low Water FlowShutdown


HE

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HEAT RECOVERY

HE

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Design Criteria — Water Steam SystemsThere are no elevation or static headrequirements for the steam separator.Therefore, this system may be used inlocations with limited overhead clearance.

• Pressure at the engine outlet must bemaintained between a minimum of 55 kPaand a maximum of 197 kPa (8.0 to 28.5 psig).

• Maximum temperature at engine outlet mustnot exceed 127° C (260° F).

• A low water flow shutdown device isstandard on high temperature coolingengines; it is a pressure differential switchlocated across the engine water jacket. - When the water flow rate slows or stops, a

pressure drop across the engine block willshut down the engine.

• The pump should be running while theengine is operating, and the pump shouldcontinue to run for approximately fiveminutes after the engine is stopped.

• Proper water treatment care is essential forsuccessful system operation.

• A low water level shutdown in the steamseparator device is required and a low waterlevel pre-alarm is also recommended. Lowengine water level could cause engineoverheating and more serious damage.

Lubricating Oil — an Auxiliar y Heat SourceWhen recovering heat from engines using hightemperature cooling systems, it may beworthwhile to use heat rejected to lubricatingoil. This heat can be applied to preheat boilerfeed water, domestic hot water, or other lowtemperature requirements.

• Heat removed by lubricating oil fromengines operating above 104° C (220° F) isalways rejected to a cooling medium otherthan the jacket water.

• Heat rejection to the oil for Caterpillarengines is approximately 7.9 Btu/kW-min(5.5 Btu/hp-min) for gas engines, 12.2 Btu/kW-min (8.5 Btu/hp-min) for diesel engines.

HIGH TEMPERATURE WATER-STEAM SYSTEMCritical Design Criteria

CirculatingPump

CondensateTank

AirEliminator

CondensateFrom Load

Steam To Load

ExcessSteamValve

13 psig



Steam Separator

Water LevelControl

Make-up Water


1 2 3

Generator

Engine


A/C

Oil/C

Low Water FlowShutdown

The main areas of consideration in adiscussion of fuel systems and fuels are:

• Fuel tanks, main and auxiliary

• Fuel coolers

• Fuel filters

• Types of fuels

• Gas engines

Fuel Tanks

Main tanks are large tanks where fuel is stored.The fuel is transferred from the main tanks tosmaller auxiliary tanks for ready access by theengine.

Bulk Storage

Fuel supply systems assure continuous andclean supplies of fuel. Bulk fuel is usuallystored in large tanks and transferred to smallertanks (day tanks) near engines by electricmotor-driven pumps. Flexible nonmetalliclines routing fuel inside buildings should meetfire-resistant qualifications similar to U.S.Coast Guard Specification 56.60-25(c).

• National Fire Protection Association (NFPA) 37 further identifies fuel storage methodsand quantities.

• The 1981 U.S. National Electric Code,Article 700, calls for on-site fuel suppliescapable of operating the prime mover at fulldemand load for at least two hours.

• Fuel storage is one of the cheapest items foran installation. It is wise to provide too muchrather than too little storage capacity.

Tank Material

• Steel tanks are preferred, but black iron tanksand fittings are satisfactory.

• Avoid galvanized, aluminum or zinc-bearingfittings and tanks, because chemical reactionswith fuel impurities will clog fuel filters.

Tank Installation

Large capacity storage tanks allow bulkpurchases and minimize dirt contamination.Maintaining full tanks reduces condensation,particularly if fuel is seldom used.

• Tanks may be above or below ground level, but high fuel level generally should notexceed the engine injector’s height. Thisprevents possible fuel leakage into cylinders.

- New and existing tanks must meetstringent corrosion protection and leakdetection regulations.

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- Above ground tanks provide accessibility,allowing for easy draining of impuritiesand reducing the danger of ground water contamination.

- Underground tanks allow the earth to workas an insulator, limiting radical temperaturechanges which can cause flow restrictions,condensation, and possible power loss.

- Regulations governing the installation andmaintenance of both above and belowground fuel tanks may apply.

Tank Design

• Water and sediment are drawn periodicallyfrom the tank. Contaminants can be localizedby rounding the tank bottom and tilting itabout two degrees toward the drain.

• Consider ground settling when installingtanks so drain cocks remain low.

- Avoid seasonal settling by burying tanksbelow frost lines.

- Locate storage tank fill tubes forconvenience and safety of fillingoperations.

• In underground tanks, remove water bypumping through a tube placed down the fillpipe.

• Vents relieve air pressure created by fillingand prevent vacuum as fuel is consumed.

Tank Maintenance

• Water contamination of fuel during long-term storage encourages microorganismgrout, forming a dark slime which:

- Plugs filters

- Deposits on tank walls and pipes

- Swells rubber products that it contacts

• Sulfur compounds are natural antioxidants,so the low sulfur fuels (0.05 percent byweight) now available will degrade quickerin storage. Gums and varnishes will formwhich can plug fuel filters and injectors.

• Because microorganism growth occurs in thefuel/water layer, the tank should be designed to minimize this interface, and water bottomsshould be drained regularly.

• Microbiocide additives, either water- or fuel-soluble, can be added to fresh fuel to inhibitmicroorganism growth. Consult your localfuel supplier for recommended additives.


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FUEL SYSTEM

For UndergroundTanks

For SurfaceMount Tanks

2¡

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• In warm climates, large bulk storage dieselfuel requires full filtering every six monthsto one year.

- Every two years fuel should be completely changed to remove water, scale, bacteriagrowth, oxidized gums/resins, and minimizefilter clogging due to fuel separation intocomponents such as asphaltenes.

• If it is necessary to store fuel longer,kerosene may be substituted for diesel fuel.

- A simple engine power adjustment may beneeded for this fuel’s lower Btu content toachieve full rated power.

Pump Lift

Cat engine-mounted transfer pumps arepositive displacement gear-type or piston-type

and have a prime and lift capacity of 2.0 m(7 ft) of diesel fuel. Pipe size, bends, and coldambients limit this capacity.

Total System

If day tanks are not used, bulk tanks mustprovide a ready fuel supply to the engine-mounted transfer pump.

• Because the fuel shutoff function is normallyaccomplished in the engine fuel system, the supply line requires no additional shutoff to stop engine operation.

- A shutoff in the supply line can cause avacuum if activated prior to the enginecoming to a complete stop, which,depending on the inertia of the system, canrequire several seconds.

- If a separate supply line shutdown is required by specification, avoid hard starting problems by including a time delayfor the solenoid.

• The return line enters the top of the tankwithout shutoff valves, allowing air to passfreelyandpreventavacuumin thefuel system.

- No more than 60 kPa (8.7 psi) restriction isrecommended in the return line.

- Fuel suction lines remove fuel about51 mm (2 in) above the tank bottom andtank end opposite the return line.

FUEL SYSTEM

Fuel TransferPump

AuxiliaryTank

AuxiliaryPump

Engine

Draw MainTank

OverflowLine

20 m7 ft

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58

• Piping and fittings should be sealed toprevent air and dirt contamination.

- Air in the system causes hard starting and erratic engine operation.

• Joint cement affected by fuel should be avoided, and connection should be made without gaskets.

• Flexible fuel lines between fuel source (bulk storage or day tank) and engine fuel inlet andreturn will isolate vibration.

Fuel Lines

The delivery line carrying fuel to the fuel transfer pump, and the return line carryingexcess fuel to the tank should be no smallerthan engine fittings. If the fuel tank feeds

multiple engines over 9.14 m (30 ft) from thetank, or temperatures are low, larger fuelsupply and return lines ensure adequate flow.The overflow line from the day tank (or, if noday tank is used, the engine fuel return line)should be one size larger.

Auxiliar y Tanks

If the fuel tank is placed more than 2 m (7 ft)below the engine transfer pump, or more than15 m (50 ft) from the pump, an auxiliary tank— or “day tank” — is desirable. While mostengines have 9-12 ft lift capability, the 3208and 3304 have a 7 ft limit.

Base Mounted Fuel Tanks

Base mounted day tanksare sometimes usedto provide a convenient and close source offuel with adequate capacity for four to eighthours of operation. While minimizing the floorspace needed for fuel storage, the height of theengine will increase significantly with thisoption designed to ease maintenance.

If fuel must be located above the injectors, anoverhead mountingday tank isrecommended to avoid excessive pressures onthe fuel system.

FUEL SYSTEM

Main Fuel Tank

Drain

Fill & Vent Cap

ELEVATED FUEL SUPPLY DESIGN

Day Tank Supply

GeneratorEngine

FlexibleHoses

Fuel TransferPump

1 2 3

Engine Fuel Return

Engine Fuel Supply

Fuel Cooler

Fuel Level Must BeBelow Injector Height

Fuel toDay Tank

Vent

DayTank

Day Tank Nominal Level

Solenoid or Float ValveManual Shutoff

From MainTank

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• A float valve or solenoid valve in this type ofday tank regulates the fuel level to keep itbelow the level of the injectors.

• Fuel returning to the main tank will, becauseof its volume, aid with cooling, but returningto the day tank is permissible.

• If overhead mounting is unavoidable, as inNFPA Section 20 concerning fire pumps,include a 20.67 kPa (3 psi) differential checkvalve in the supply line and a 3.45 kPa(0.5 psi) differential check valve in thereturn line.

Coolers and Filters

By reducing the temperature of fuel andremoving harmful particles, coolers and filtersimprove the quality of the fuel used by anengine.

Coolers

Engines incorporating unit fuel injectorstransfer about 42.2 kJ (40 Btu) per minute perinjector into the return fuel. If the fuel tank isinsufficient to dissipate this heat, a coolingsource must maintain fuel temperatures below68° C (155° F). Heat also causes a volumetricchange, resulting in a one percent power lossfor each 6° C (10° F) above 38° C (100° F).

Auxiliar y CoolingThe air-fuel mixture a naturally aspiratedengine can draw into its cylinders is limited bythe engine’s breathing characteristics andatmospheric conditions. Therefore, enginepower output is limited.

Turbocharging is an efficient means ofincreasing air flow and power output.However, air compression by the turbochargerincreases air temperature. An aftercoolerbetween the turbocharger and intake manifoldcools the compressed air. Acceptabletemperature levels are achieved using a watersource separate from engine jacket water.

Two temperature ranges are available:

• Water at a minimum of 32° C (90° F)

• Water at a minimum of 54° C (130° F)

Filters

Clean fuel is necessary for dependable engineperformance. Engine filters protect the fuelinjection pumps and nozzles and should neverbe removed or bypassed.

Primar y filters with 0.30 mm (0.012 in)screens extend engine filter and transfer pumplife. Water and sediment traps can be includedupstream of the transfer pump, but pump flowmust not be restricted.

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SCAC

Engine

A/C

JW In

JW Out

Out In

130˚90˚ Aux. Water

Duplex filters for fuel and lubricating oilallow extended operation without interruption.

• The main and auxiliary filter systems allow changing either the main or auxiliary filter elements with the engine running under load.

• Generally, the same elements are used inboth systems, and are capable of providingadequate filtration for at least 100 hours fullload running time with reasonably clean fueland oil.

• Use pressure gauges to determine whenfilters must be changed.

• Avoid mounting filters near the radiator fan,because a fuel or oil leak during replacementcould create a fire hazard. (As eithersubstance passes through the fan it can beatomized, and therefore easier to ignite.)Plus, coated radiator fins trap dirt which candiminish cooling capability.

Caterpillar Engines

Caterpillar engines operate efficiently with avariety of fuels. Generally, use the lowestpriced distillate fuel which meets therequirements.

Diesel enginesmay require optional equipmentto run on fuels as light as Jet-A, JP-5, andkerosene, and fuels with heavy distillates.

Clean fuels provide maximum service life andperformance. Dirty fuels adversely affectcombustion, filter life, injection systemperformance, startability, and componentservice life.

Requirements

Fuels meeting the above requirements include:

* These distillate fuels are also referred to as “gas oil,” “35-second oil” (Redwood No. 1), or “diesel oil.”


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FUEL SYSTEM

Cetane NumberPrecombustion Chamber 35 minimumDirect Injection 40 minimum

Viscosity100 SUS at 38° C (100° F) max.

Pour Point 6° C (10° F) below ambient temp.

Cloud Pointnot higher than ambient temp.

Sulfur

adjust oil change period for high sulfur fuel (greater than 0.5%)

Water and Sediment 0.1% maximum

ASTM D396No.1 and No. 2 fuels (burner fuels)

ASTM D975No. 1 and No. 2-D diesel fuel oil

BS2869Class A1, A2, B1, and B2 engine fuels

BS2869Class C, C1, and C2 and class D burner fuels

DIN51601 Diesel fuel*

DIN51603 EL heating oil*

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Other fuel categories requiring specialtreatment or blending when applying tomodern engine designs include:

• Light residual fuel oil — ASTM D936-67 heavy, BSS2869 Class F, loosely referencedas “boiler fuel” or “1000-second oil”

• Heavy residual fuel oil — ASTM D936-67 No. 6, BSS2869 Class G, sometimes called “burner fuel oil” or “3500-second oil”

Aviation kerosene can be used as a fuel forCaterpillar diesel engines but some precautionsmust be taken. The following aviation fuelsare defined by military, NATO, andcommercial codes:

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FUEL SYSTEM

Name(militar y or MIL-Spec NATO Commentscommercial) ASTM SPEC Code

JP-4 MIL-T-5624 F-40Aviation gasoline; NOTfor use as Cat engine fuel

JP-5 MIL-T-5624 F-44Aviation kerosene; acceptable Cat engine fuel; must control viscosity

JP-8 MIL-T-83133 F-34Aviation kerosene; acceptable Cat engine fuel; must control viscosity

Jet A-1 ASTM D 1655 F-35Commercial aviation kerosene; acceptable Cat engine fuel; must control viscosity

Jet A ASTM D 1655U.S.A. commercial aviation kerosene; acceptable Cat engine fuel; must control viscosity

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The viscosityof fuel is significant because thefuel serves as the lubricant for the fuel systemcomponents.

• If the viscosity of the fuel is lower than 1.4 cSt as supplied to the engine, excessive wear and scuffing, and seizure can occur.

• JP-5 fuel typically has a viscosity of 1.5 cSt measured at 40° C (the normal temperature used to evaluate a fuel).

• JP-8, Jet A-1 and Jet A have a viscosity of1.2 cSt typically measured at the 40° C temperature, which is below the desiredvalue for Cat engines.

- To eliminate the problem of low viscosityof JP-8, Jet A-1, and Jet A kerosenes, thefuel can be supplied to the engine at alower temperature to provide an increasedfuel viscosity.

- At a temperature less than 25° C (77° F),the fuel should have sufficient viscosity toproperly lubricate the fuel systemcomponents.

- The military fuel JP-8 does have amandatory additive package (icinginhibitor, corrosion inhibitor, and staticdissipator additive) which does increase thelubricity of the fuel. Jet A-1 may or maynot have this additive package.

• Light fuels may out-produce rated power atfactory settings, but adjustments to theengine fuel system are generallydiscouraged.

- Fuel system component life mayexperience increased wear due to the lowviscosity of the lighter fuel.

• The customer should order as heavy a distillate fuel as engine and temperature conditions permit.

NOTE: Caterpillar diesel engine fuel settingsare based on 35-degree API (specific gravity)fuel. Fuel oil with a higher API (lower specificgravity) number reduces power output unlesssettings are corrected. When using heavierfuels, a corrected setting prevents poweroutput above approved ratings.

Crude Oil FuelsCrude oil, in some cases, is a practical andeconomic fuel for diesel engines. Crude oils areevaluated individually and special equipmentmay be needed to condition the fuel. Minimumguidelines have been established to determinethe suitability of crudes.

Residuals

Residual fuel(which resembles tar andcontains abrasive and corrosive substances) iscomposed of the remaining elements fromcrude oil after the crude has been refined intodiesel fuel, gasoline, or lubricating oil.

After the more desirable products have beenrefined, residual fuel can be combined ordiluted with a lighter fuel to produce a mixturethat can flow. This mixture is calledblendedor heavy fuel. Heavy fuels tend to create morecombustion chamber deposit formations whichcan cause increased cylinder and ring wear,particularly in smaller, higher speed engines.

• Blending may improve fuel density, butaddition of alcohol (ethanol, methanol) orgasoline causes an explosive atmosphere inthe tank and is not recommended.

• Cat 3500 and 3600 family engines can bemodified to run on blended fuels, butextreme PREVENTIVE MEASURES MUSTBE TAKEN, including following athoroughmaintenance program and use ofhigh quality fuel treatment equipment.


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Blended fuel can lower fuel cost, but there areoften significant trade-offs. Fuel price must beweighed against:

• Fuel containment effects

• Reduced engine component life

• Higher maintenance and personnel costs

• Reduced warranty

Total Base Number

Most diesel fuels contain some degree ofsulfur. Usually, heavy fuels have a highersulfur content than distillates. Lubrication oilsneutralize sulfur by-products, namely sulfuricacid, and thus retard corrosive engine damage.

TBN (Total Base Number) reflects thealkalinity number and is a measure of an oil’sacid-neutralizing capacity.

• The higher the TBN, the more neutralizing capacity.

• When the fuel sulfur content exceeds0.5 percent, special lubricating oil and more

frequent oil changes are required to assuresatisfactory engine/oil service life.

New oil TBN — Follow 1.25 line to line Awhich intersects at 25. This is therecommended TBN for 1.25 percent sulfurcontent.

Used oil TBN — Follow 1.25 line up to line Bwhich intersects at 12.5. At 12.5 TBN the oilshould be changed.

Fuel Economics

Heavier fuels generally provide more energy.Examining the economics (see the illustrationprovided) we can see that a gallon of No. 1diesel fuel weighs 3.08 kg (6.79 lb)and will produce approximately 3.10 kW-h/L(15.78 hp-h/gal). The normal — and heavier —weight of No. 2 furnace oil is 3.37 kg (7.40 lb)and willproduceapproximately 3.21 kW-h/L(16.56 hp-h/gal).

Thus, for each 3785 L(1000 gal) of No. 2furnace oil, you obtain an additional 582 kW/h(780 hp/h) — or a 4.9 percent gain. What’smore, furnace oil is usually less expensive.

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FUEL SYSTEM

A

B

1.51.00.5

0.5

0.5

0.5

0.5

0.5

0.5

Percent Fuel Sulfur

Alkalinity Value

TBN by ASTM D2896

Used OilMinimum TBNUSEFUL RANGE OF OIL

New OilRecommended TBN

NEW OIL ALKALINITY VALUE REQUIRED FOR A STANDARD OIL CHANGE PERIOD WITH

UP TO 1.5% FUEL SULFUR

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Since fuel consumption is the largest generatorset operating expense, consider using a fuelwhich will provide the lowest cost per kW/h(hp/h) while delivering satisfactory performance.

Engine Configuration

To correctly determine which spark ignitedengine configuration is required for a specificapplication, the following minimuminformation must be known:

• Horsepower required

• Gas pressure

• Type of fuel

• Type of cooling system

• Temperature of auxiliary cooling water

• Exhaust emission levels permitted

Gas Pressure• Naturally Aspirated (NA) engines and

turbocharged engines using optional lowpressure equipment require minimum gaspressure of 13.8 kPa (2psi) to the gas regulator.

• Standard turbocharged engine minimumrequirements range from 82.7 kPa (12 psi) to330 kPa (48 psi).

- Lower values may be applicable only atlow altitude installations where response tosudden load changes is not critical.

• Turbocharged engines require separatecircuit aftercooling, so a 30° or 55° C(90° or 130° F) cooling source must beavailable.

• Operating with supply gas pressures slightlybelow the minimum values may be possibleif the engine is not subjected to large loadfluctuations.

• If the supply gas pressure to the regulator isbelow published limits, a low pressureconversion group should be used.

Note: minimum gas pressure must be adjusted for altitude.

RegulatorsRegulator valves are positioned close to thecarburetor for optimum gas pressure control. Abalance line from regulator to air inletmanifold compensates for air cleanerrestriction and turbocharger boost.


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Gas Pressures Required

Engine Models Pipeline DigesterLandfill

3300 NA 14 kPa (2 psi) Consult Factory3500 NA

3306 TA 83 kPa (12 psi) Consult Factory

3408 & 138 kPa (20 psi) 138 kPa (20 psi)3412 TAs

3500 SITA L.E. 207 kPa (30 psi) 241 kPa (35 psi)

Low Pressure 14 kPa (2 psi) Consult FactoryConversion Gp.

3785L (1000 gal)

3.08 kg(6.79 lb)

3.37 kg(7.40 lb)

3.21 kW - h/L(16.56 hp - h/gal.)

#1Diesel

#2Furnace

Oil

• Manual and solenoid valves are upstream(high pressure side) of the regulator tominimize restriction between regulator andcarburetor.

• Regulators will withstand inrush of pressuregas when the valve is open.

• The upstream valve position slightly extendsengine stopping time during normalshutdown.

• Emergency shutdown remains immediate bygrounding magneto power and closing gasvalves.

• Gas pipes cannot be used for electricalgrounding.

Types of Fuel

A wide variety of gaseous fuels can be burnedin Caterpillar gas engines. Various gases canback up the primary fuel. Addition of anotherregulator and change of carburetor may benecessary to accommodate a particular gas.

The low heat value (LHV) of a gas is the highheat value (HHV) less the heat used tovaporize the water formed by combustion.LHV is the figure Cat uses to express fuelconsumption.

Power capabilities are calculated using LHVofthe air-fuel mixture and not directly to theLHV of the fuel. Using fuels other thannatural gas requires a recalculation of enginepower capabilities.

Natural GasThe recommended fuel for Cat SI engines isdry natural gas or “pipeline gas.” Thesecommercial gases have less than 10 parts permillion (ppm) of hydrogen sulfide. Any gaswith a greater concentration should beevaluated to determine engine effects andrequired special maintenance practices.

• Natural gas is a mixture of gases composedmostly of methane with varying percentagesof methane, propane, butane, and smallamounts of helium, carbon dioxide, andnitrogen.

• In its original state, natural gas is oftenreferred to as field, well head, or wet gas.

• The designation “wet” or “dry” does notrefer to water content, but to the presence orabsence of liquid hydrocarbons such asbutane or pentane.

- Before distribution, the wet ends areremoved to provide dry pipeline gas.

Natural Gas — Propane• Propane is transported and stored in a liquid

state, and converted to a vapor at the point ofuse.

- Local codes may prohibit liquid propanestorage within a building.

- It is heavier than air, so good ventilation isnecessary to prevent concentration in lowareas.

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Low HeatValue =Useful Energy

Latent Heat ofVaporization =Lost Energy

High HeatValue

Alternative Fuels• Sweet gaseshave low concentrations (below

10 ppm) of sulfur compounds, and can be usedwithout treatment or changes to the engine.

• Sour gasgenerally refers to fuels containinghigh concentrations of sulfur compounds(above 10 ppm).

- Fuels such as field, digester, bio-mass, and landfill gases usually fall into this category,and require special operating considerations.

Gas/Diesel Operating EfficiencyPerformance characteristics of gas enginesrequire consideration when analyzingoperating costs. The Brake Specific FuelConsumption (BSFC) at part load is muchhigher than at full load. When compared to adiesel engine, this part load inefficiency isapparent.

For most efficient operation, gas enginesshould operate near full load.

BSFC

FUEL EFFICIENCY VS. LOAD

25 50 75 1000

Gas

Diesel

% Load


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Several starting mediums are available, butmost common are electric (DC) and air. Thesemediums are both easily controlled andapplied either manually or automatically.

Starting Basics

Startability of a diesel engine is affectedprimarily by ambient temperature andlubricating oil viscosity. The diesel relies onheat of compression (resulting from crankingtime) to ignite fuel. When engines are cold,longer cranking periods are required to developignition temperatures.

Lubricating OilHeavy lubricating oil imposes the greatest loadon the cranking motor. Oil type andtemperature drastically alter viscosity. SAE 30oil approaches the consistency of grease below0° C (32° F).

Electric Starting

Electric motors utilize low voltage directcurrent and provide fast, convenient,pushbutton starting with lightweight, compact,engine-mounted components.

• Electric starting is generally 24-volt or 30- to32-volt DC.

• A manual starting system includes a startswitch, solenoid, and starting motor.

- When the start switch is closed, thesolenoid moves a pinion to engage with theflywheel ring gear.

- After engagement, the main motor contactsclose and the motor begins to crank.

- The starting motor will continue to crankuntil the start switch is opened (usually byreleasing the start button).

Flywheel Magnetic Switch

Starting Motor

StartSwitch

Batteries

STARTING

STA

RT

ING

BatteriesBatteries provide sufficient power to crankengines fast and long enough to start.

• Lead-acid battery types are common, havehigh output capabilities and low cost.

• Nickel-cadmium batteries are costly, buthave long shelf life and require minimummaintenance.

- Nickel-cadmium types are designed forlong life.

Battery SizingLow ambient temperatures drastically affectbattery performance and charging efficiencies,as well as oil viscosity. High temperaturesshould also be avoided.

• Maintain 32° C (90° F) maximumtemperature to assure rated output.

• High temperatures also decrease battery life.

• Ideally, temperatures surrounding the batteryshould not exceed 25° C (77° F). Battery lifeis roughly halved by a 10° C (17° F) rise intemperature; doubled if ambients are reduced10° C.

Battery Location and Considerations• To minimize voltage drops between the

batteries and starting motor, place thebatteries near the starting motor and connectwith adequately sized cables.

• Cables should be routed to avoid sharpbends and have sufficient play and supportto minimize stress on the battery terminals.

• Locate cranking batteries for easy visualinspection and maintenance, away fromflame or spark sources, and isolated fromvibration.

• Mount level on nonconducting material and protect for splash and dirt.

• Disconnect battery charger when removingor connecting battery leads, as solid-stateequipment (electronic governor, speedswitches, etc.) can be harmed if subjected tothe charger’s full output.


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STARTING

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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 requireless than 59.2 ml (2 oz) make-up waterduring 30 hours of operation.

• Float-equalize chargersare more expensivethan trickle chargers and are used inapplications demanding maximum battery life.

- These chargers include line and loadregulation, and current limiting deviceswhich permit continuous loads at ratedoutput.

• Engine-driven generators or alternators canbe used, but have the disadvantage ofcharging batteries only while the engineruns.

- Where engine-driven alternators andbattery chargers are both used, thedisconnect relay is usually controlled todisconnect the battery charger duringengine cranking and running.

• Chargers must be capable of limiting peak currents during cranking cycles, or have a relay to disconnect during cranking cycles.

- If generator sets are subject to many starts,insufficient battery capacity could threatendependability.

- Charging alternators are not required forstandby applications.

Air Starting

Manual or automatic air starting is highlyreliable. It is generally applied where facilitieshave existing plant air, or where a combustiblegas may be present in the atmosphere. Torque available from air motors accelerate theengine to twice the cranking speed in abouthalf the time required by electric starters.Remote controls and automation, however, aremore complex. Because the exhaust from theair starter is very loud, an air silencer may beappropriate.

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An air starting system includes:

• Air starting motor

• Air storage tank

• Starting solenoid valve

• Pressure regulator

• Oiler

• Optional air silencer

• Pressure air may originate from air receiversand plant air.

- A check valve between plant air andreceiver assures that failure of plant airwill not deplete the backup supply.

- The air compressors are driven by gasolineengines and electric motors wired to theemergency power source.

• Air motor supply pipes should be short anddirect, and at least equal in size to the motorintake opening.

- Black iron pipe is preferable, and it shouldbe supported to avoid stresses on thecompressor.

- Flexible connections between motor andpiping are required.

• Tandem or compound engines use twomotors and two solenoid valves.

- Valves are equal distance from their respective motors for coordinated motor engagement.

- When a single solenoid controls air to bothmotors, piping between valve and eachmotor must be equal in length.


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AIR STARTING SYSTEM

Plant Air Supply

Storage Tank

CheckValve

Oiler Regulator

Solenoid Valve

Compressor

Engine

Starting Motor

Generator

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• Deposits of an oil-water mixtureaccumulating in receiver and piping areremoved by traps installed at intervals in thelines.

- Lines slope toward these traps.

• The compressed air may freeze in lowambient temperatures as it expands throughthe motor.

- Below 0° C (32° F), a dryer at thecompressor outlet or a small quantity ofalcohol in the air tank prevents freezing.

- Consult the factory for recommendationsbelow -18° C (0° F).

Air PressureCompressed air from a 758 to 1723 kPa (110to 250 psi) source is regulated to 759 kPa(110 psi) and piped to the air motor. Highersupply air pressures may be utilized byplumbing regulators in series.

Air ReceiversAir receivers should meet ASMEspecifications and be equipped with a safetyvalve and gauge. Check safety valvesfrequently to guard against sticking.

Receivers are sized for a specified number ofstarts. Receiver size is estimated by:

Free AirQuantity of free air required per start (Ar)depends on:

1. Time required perstart. Time per start depends upon:

• Engine model

• Condition

• Ambient air temperature

• Oil viscosity

• Fuel type

• Condition of fuel system

• Cranking speed

Five to seven seconds is typical for dieselengines at 25° C (77° F), but restarts of hotengines normally take less than two seconds.

Due to the time necessary to develop acombustible mixture in the intake manifold,natural gas engines usually exhibit startingtimes up to double that of a diesel.

2. Free airconsumption.Free airconsumption depends on the same variablesas time required per start, and also on thepressure regulator setting.

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Rc =

where:

Rc = Receiver Capacity (m3) (ft3)Ns = Number of StartsRp = Receiver Pressure (kPa) (psia)Ar = Free Air Requirement per Start (m3) (ft3)Ap = Atmospheric Pressure (kPa) (psia)Minimum = (724 kPa) (90 psia)

Ns (Ar x Ap)

Rp - 724 or 90S

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Engines equipped with a pneumatic oil prelubrication pump require an additional 0.03 m3/s (1 cu ft/s) of air volume. Cat 3600engines require a one- to five-minute prelube; all other models require 2-20 sec. Five- to

seven-second starting (prelube is additional) istypical for engines operating at 25° C (77° F)ambient temperature.

3. Prompt manual or automatic air shutoffafter engine starting

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Air StartingFree Air Consumption m3/s (cu ft/s)

Required for Air Motor to Start Engine at 10° C (50° F)Min. Tank

Model MotorsAir Pressure to Motor kPag (psig)

Pressure690 (100) 862 (125) 1034 (150) kPag (psig)

3304 1 0.16 (5.8) 0.20 (6.8) 0.21 (7.7) 242 (35)

3306 1 0.17 (5.9) 0.20 (6.8) 0.22 (7.8) 248 (36)

3406 1 0.18 (6.4) 0.21 (7.3) 0.24 (8.6) 276 (40)

3412 1 0.25 (9.0) 0.29 (10.3) 0.33 (11.8) 207 (30)

D379 1 0.26 (9.3) 0.30 (10.3) 0.36 (12.6) 207 (30)

D398 1 0.28 (9.8) 0.32 (11.4) 0.38 (13.3) 242 (35)

D399 1 0.30 (10.8) 0.34 (12.1) 0.40 (14.1) 345 (50)

3508 1 0.26 (9.3) 0.30 (10.8) 0.36 (12.6) 207 (30)

3512 1 0.28 (9.8) 0.32 (11.4) 0.38 (13.3) 242 (35)

3516 1 0.30 (10.5) 0.34 (12.1) 0.40 (14.1) 345 (50)

3606 1 0.38 (13.6) 0.46 (16.4) 0.54 (19.2) 690 (100)

3608 1 0.38 (13.6) 0.46 (16.4) 0.54 (19.2) 690 (100)

3612 2 0.76 (27.2) 0.92 (32.8) 1.08 (38.4) 690 (100)

3616 2 0.76 (27.2) 0.92 (32.8) 1.08 (38.4) 690 (100)

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Starting Aids

Starting aids for temperatures below 21° C (70° F) reduce cranking time and assuredependable starts.

Starting Aid Options

Jacket waterheatersare used on both manualand automatic starting systems, but areessential for automatic starting below 21° C(70° F). Heaters precondition engines forquick starting and minimize the high wear ofrough combustion, by maintaining jacket watertemperature during shutdown periods. Dualheaters are used on large vee-type engines toensure circulation.

Heaters thermostatically control jacket watertemperature near 30° C (90° F) to promote faststarts. Higher temperatures accelerate aging ofgaskets and rubber material.

Preheating engine combustion chambersimproves fuel ignition. Precombustionchambered engines provide a resistance-typeglow plug in each chamber to aid manualstarts in cold weather. The plug tip reaches980° C (1800° F) in approximately 30 secondsto vaporize injected fuel. Direct injectionengines cannot accommodate glow plugs.

In a flame start, glow plugs project into theair inlet manifold and ignite a small amount ofdiesel fuel during manual starting. The flameis maintained until smooth idling conditionsare achieved.

Ether starting aids are restricted to manualstarting systems and are rarely used forgenerator sets. Ether is highly volatile, with itslow ignition point. Introduced into the intakeair, it ignites the mixture at low cylindertemperatures. High pressure capsules are thesafest and most positive injection method.Ether injection should not be used on Cat 3600engines.

Oil heatersare usually not recommended dueto the danger of oil coking. If specified, heaterskin temperatures should not exceed 150° C(300° F) and have maximum heat densities of 0.02 W/mm2 (13 W/in2).

Starting Requirements

Automatic Start-StopAutomatic start-stop systems are primarily forunattended engines which must:

• Start automatically

• Pick up the load

• Operate the load

• Stop automatically when demand ceases

For example, a standby generator set muststart automatically when utility power fails.

Caterpillar offers both electric and air poweredsystems.

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Ten-Second StartTen-second starting is often required either byapplication or local regulation. The NationalFire Protection Association (NFPA) 99, HealthCare Facilities 1996 Edition states, “generatorset(s) shall have sufficient capacity to pick upthe load and meet the minimum frequency andvoltage stability requirements of theemergency system within ten seconds after theloss of normal power.”

Caterpillar requirements for ten-secondautomatic starting include:

• Combustion air a minimum of 21° C (70° F)

• Jacket water heaters which maintain aminimum of 32° C (90° F) water temperature

• Fully charged batteries to provide 60 secondsof continuous cranking, or full air supply

• Readily available fuel

Engine ShutdownEngine shutdowns result from either manuallyor automatically shutting off fuel, air, or both.

Depending on engine configuration, fuelshutdowns vary from a manual position on agovernor control (shown) to an electro-mechanical shutoff control.

AutomaticIf automatic or remote shutdown is required, asolenoid shutoff is used on engines withmechanical, hydromechanical, or hydraulicgovernors. The solenoid shutoff operates bymoving the fuel rack to the shutoff position.Either an energized-to-run or energized-to-shutdown system is available. For energized-to-run systems, an electrical signal must bepresent at the fuel solenoid for the engine tooperate. When the signal is lost, the enginewill shut down.

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For engines using electronic governors, thecontrol panel signals the actuator to shut offthe fuel. In some cases a solenoid shutoff isalso used.

In either system, the engine may be shut downmanually.

Engine Shutdown DevicesCaterpillar offers protection devices to preventserious engine damage. Minimum protectionfor any generator set includes engine shutdownin the event of:

• Overspeed

• Low lubricating oil pressure

• High jacket water temperature

If the generator set is remotely started,overcrank protection is required.

• Indicators for engine water level and floware recommended.

• Additional operating functions can bemonitored with minor modifications.

Overspeed ShutdownEngine overspeed can result from a governormalfunction or fuel rack sticking. With nooverspeed protection, a diesel engine canrapidly accelerate to the point of destruction.

Inlet Air ShutdownEngine overspeed can result from a seized fuelrack, or by the engine drawing in combustiblegases which are sometimes present in thesurrounding atmosphere — in oil or gasdrilling operations, for example. If either ofthese conditions cause the engine to overspeed,a fuel shutoff system may be ineffective.

• A positive way to stop the engine is to shutoff the air supply. An engine cannot operatewithout a source of combustion air.

• The air inlet shutdown is not recommendedfor routine shutdowns because there aresome potential adverse mechanical effects onthe engine.

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Conventional SwitchesConventional electro-mechanical controlpanels use switches and probes for monitoringengine conditions.

• Shown below is a Caterpillar two-wire typecoolant temperature switch.

- The two-wire system eliminates the need toground through the case and providesgreater reliability and accuracy.

- To minimize electrical arcing, the switchutilizes snap action contacts activated by aminiature switch mechanism in lieu ofbutt-type contacts.

- The temperature sensing element is a waxmotor type, yielding excellent sensingaccuracy.

• Low oil pressure can cause serious enginedamage.

- If pressure falls below a safe level, the oilpressure switchwill activate an engineshutdown.

- The oil pressure switch is also two-wiretype with the same stable groundingcharacteristics.

- It also includes the same self-cleaningcontacts as the coolant switch.

• The magnetic pick-upmeasures enginespeed and converts it to a digital pulse.

- Generally Cat engines are shut down at118 percent of rated speed.

Electronic Modular Control Panel (EMCP)Monitoring SystemThe Caterpillar Electronic Modular ControlPanel II (EMCPII), consisting of solid statemicroprocessor-based engine control modules,uses electronic transducers to monitor anddigitally display engine conditions. Operatingfunctions are monitored by three components:

• Jacket water transducer (water temperatureprobe)

• Oil pressure transducer

• Engine speed magnetic pickup

The oil pressure and water temperaturetransducers and the magnetic engine speedpickup send information directly to the enginecontrol module. Transducers are industrialgrade and environmentally sealed forreliability. They help eliminate additionaljacket water and oil pressure temperatureswitches needed to activate alarm systems andgauges, and require significantly less wiring.

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MPUDSU/OPT

EMCP

MONITORING SYSTEM

• Jacket Water Temperature Transducer• Oil Pressure Transducer• Engine Speed Magnetic Pick-Up• DSU (Data Sending Unit)• Single Wire Serial Data Link

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Alarm Modules

Warning alarms and alarm modules areavailable to provide an audible and/or visualwarning of engine conditions before theybecome severe enough to shut the enginedown, or keep it from starting. This givesmaintenance personnel time to remedy thecondition.

The prime power alarm module shownsatisfies NFPA 99 and NFPA 110. Also, remoteannunciators are available which also satisfyNFPA 99 and NFPA 110.

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A governor controls engine speed (generatorfrequency). The main areas of enginegovernors to understand are:

• Basic terms

• Types of governors

• Governor selection

Basic Terms

A few terms must be understood in order toselect the appropriate governor for a specificapplication. These terms are commonlyencountered when specifying or analyzinggovernor and generator set performance.

Speed bandrefers to the amount of variancefrom a set speed at any steady load.Caterpillar governors have a speed toleranceof +/- 0.33 percent while Woodwardgovernors offer +/- 0.25 percent.

Transient speedsare temporary excursionsfrom steady-state speed caused by sudden loadchanges.

Recovery time is the time of excursion fromthe steady-state speed band until returning andremaining within the band.

Droop, speed droop, and regulation are termsused interchangeably to describe therelationship of engine speed change from noload to full load in steady-state operation.


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Time

Hz STEADY STATE REGULATION (0.33%)

50.17

(60.19)

50

(60)

49.83

(59.81)

LoadApplied

LoadRemoved

Steady StateSpeed Band

Time

TRANSIENT CONDITION

LoadApplied

RecoveryTime

Steady StateSpeed Band

Time

RECOVERY TIME

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Expressed as a percentage, droop is calculatedby dividing the difference in speed betweenfull rated load and no load by speed at ratedload and multiplying the quotient by 100.

Example:A generator set equipped with a three percentdroop governor will operate at 60 Hz or1800 rpm (50 Hz or 1500 rpm) at rated load (athalf load — 60.9 Hz [50.75 Hz]). At no load thegenerator set frequency will increase no morethan three percent to 61.8 Hz or 1854 rpm(51.5 Hz or 1545 rpm).

A generator equipped with a zero percent droopgovernor will operate at 60 Hz or 1800 rpm (50 Hz or 1500 rpm) at rated load and 60 Hz or1800 rpm (50 Hz or 1500 rpm) at half load orno load.

Transient Response with DroopThe following graphic depicts a 60 Hzgenerator set equipped with a three percentdroop governor. With no load, the generator

operates at 61.8 Hz (1854 rpm). When halfload is applied, the frequency drops toapproximately 59.2 Hz (1777 rpm). Thegovernor senses this speed drop and adjusts therack, delivering more fuel to the engine. Thiscauses a momentary increase in generatorfrequency above 60.9 Hz (1827 rpm) before itlevels off at 60.9 Hz (1827 rpm). Recoverytime from when the load is applied until thefrequency levels off at 60.9 Hz is four seconds.Governors are only one factor affectingtransient speed and response. Greaterinfluencers of the engine’s recovery capabilitiesinclude:

• Size and type of load

• Engine configuration

• Type of generator voltage regulator

• Rotating inertia of motor load, engine, andgenerator

Governor Types

The following governors are noted in order ofcost, simplicity, and power output. Catrecommends using the simplest governorwhich adequately satisfies the application.

ENGINE GOVERNORS

% Load0 50 100 150

Hz3% DROOP

51.5(61.8)

50(60)

3%

% Load0 50 100 150

Hz% DROOP — ISOCHRONOUS

50(60)

Time

4 Sec.

Hz

50% LOAD APPLIED

61.8

60.9

60.0

59.2

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Mechanical and HydromechanicalGovernors

Although the exact design of ahydromechanical governor may vary, basicallyit is a mechanical governor assisted by ahydraulic servo valve.

Mechanical GovernorsThe simplest Cat governor is the mechanicaltype. It uses a ball head with flyweights forspeed sensing. The mechanical governordevelops sufficient force by flyweight action tomove a fuel rack or carburetor control.

• The Caterpillar mechanical governor is athree percent fixed droop governor andfeatures 0.33 percent steady-state regulation.

• Mechanical governors are adequate formanual paralleling and will share load withinten percent at any load point.

Hydr omechanical GovernorsAs the force required to move the governorlinkage and fuel injection pumps increases, theforce developed by the governor must alsoincrease. On a larger engine, instead ofincreasing the size of the mechanical governor,engine lubricating oil pressure is sometimesused to support the action of a mechanicalcontrol.

• Like Cat mechanical governors, Cathydromechanical governors havenonadjustable three percent droop and areadequate for manual paralleling.

• Engine lubricating oil is used for lubricationand hydraulic power.

• They are used in most installations under500 kWfor spark ignited and 600 kWfordiesel.

• They share load with paralleled units within+10 percent.

Speed ControlCaterpillar mechanical and hydromechanicalgovernors have an optional governor controlmotor. The 24-volt direct current motor is usedfor speed control from remote locations.

Hydraulic GovernorsA hydraulic governor builds on the basicmechanical governor design, and developsadditional work force. A control valve allowsoil pressure to work directly on the terminalshaft through a power piston. No longer is thework force associated with the governor’sspeed-sensing mechanism.

• Depending on oil pressure and the area ofthe power piston, adequate force can bedeveloped to control almost any size engine.

• The Woodward PSG, UG8D, and 3161 arehydraulic governors offered by Caterpillar.

• The governors have zero to ten percentadjustable droop and exhibit steady-stateregulation of ± 0.25 percent.

• When adjusted to three percent droop,they share load with parallel units withinfive percent.

• These governors are applicable for singleunit or manually paralleled multiple unitapplications.

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Woodward PSG GovernorsThe Woodward Pressure-Compensated SimpleGovernor (PSG) uses engine lubricating oil fora hydraulic medium and a self-containedpump, gear driven from the engine, to developits work capacity. Generally it is adequate forgenerator sets up to 600 kW.

• The PSG has an externally adjustable droopcontrol from zero percent (isochronous) toseven percent.

• Shares load with paralleled units withinfive percent. A 24- to 32-volt DCsynchronizing motor for remote speedcontrol is included with the basic governor.

Woodward UG8D Dial GovernorTwo versions of the Woodward UG8D DialGovernor are available — one for single unit(non-parallel) operation and the other formultiple unit (parallel) operation. The singleunit version is fast acting, providing excellentsteady-state speed control and transientresponse to off speeds in startup and loadrejection.

The paralleling version possesses dampeningcharacteristics allowing it to perform well inparallel operations. It is slower acting, butretains excellent steady-state speed control andtransient response. Both versions use a self-contained oil supply and gear driven pump.They are generally usedon generatorsetsover600kW.

The Woodward UG8D has four externaladjustments:

• Speed Droop — zero to ten percent, sharesload within five percent

• Load Limit — provides movable stop whichlimits the amount of load the generator setwill accept

• Speed Setting — manually adjusts enginespeed (rpm)

• Speed Setting Indicator — indicates percentof travel of terminal shaft; the UG8D hasremote speed control which operates on110 VAC or 24-32 VDC

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Woodward 3161 GovernorThe Woodward 3161 governor is completelyinterchangeable with the UG8D. Thesegovernors feature:

• A synchronizing motor for remote speedcontrol

• Zero percent (isochronous) to ten percentdroop

• External adjustability

• Synchronizing motor for remote speedcontrol

• Adjustable load limit

• Use of an independent oil supply and pumpwhich develops the output force necessary tocontrol large engines

All hydraulic governors feature ± 0.25 percentsteady-state regulation, load sharing withinfive percent, and are capable of single unitisochronous operation or manual paralleling.

Electronic GovernorsElectronic governors offer the greatercapability and flexibility needed for complexcontrol applications.

Advantages of electronic governing systemsinclude:

• Automatic paralleling of multiple units

• Isochronous load sharing

• Fast response to load changes whichminimizes speed changes and recovery time

• Flexibility with numerous options

• Excellent steady state frequency control

• Fail-safe speed sensing

Most electronic governing systems include:

• Electronic speed control assembly withoptional load sharing control

• Actuating system (electronic or electronichydraulic)

• Magnetic pickup

• Oil pressure switch (optional)

Operation1. Engine speed is detected with the magnetic

pickup which is located next to the flywheelring gear. The magnetic pickup generates avoltage with frequency proportional toengine speed. This voltage travels to theelectronic control assembly where it iscompared to the adjusted governor setting

2. The control sends the appropriate signal(voltage) to the actuating system thatconverts the electrical input to a mechanicaloutput which positions the engine fuel rack.

3. The oil pressure switch attaches to theengine and is electrically connected to thecontrol assembly. When proper oil pressureis obtained, the switch signals to the controlassembly to accelerate their engine to ratedspeed.

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• All wiring should be isolated from ACpower.

- Low grade voltage lines, e.g., magneticpickup, and oil pressure switch linesshould be shielded and grounded becausesignals flowing through these wires areinherently weak.

Governing SystemThe Woodward 8290/1724 and 8290/Peakactuator is a completely electronic governingsystem. The 8290 identifies the controlassembly and the 1724 identifies the electronicactuator. In contrast, the 8290/Peak uses anelectrical motor to control a hydraulic servovalve which provides the mechanical power tomove the fuel rack. Both systems as standardhave zero speed droop and exhibit steady-stateregulation of ± 0.25 percent.

• When load demand increases, requiring additional units in parallel, a load sensor maybe added to the system for droop (zero to tenpercent) — or isochronous — load sharing capabilities.

- Units can share load within ± 0.5 percent.

• An SPM (Speed and Phase Matching) Synchronizer can be connected to the load sensor for a fully automatic system.

Woodward 2301 EG ActuatorsThe 2301 identifies the Woodward electroniccontrol assembly. The electric/hydraulicactuator is either an EG3P, EG10P, or EG26P,and contains an engine driven oil pump todevelop power to move the fuel mechanismsof larger engines.

• The EG3Phas a maximum work capacity of 6.1 J (4.5 ft-lb).

• The EG10Phas a maximum work capacityof 12.6 J (9.3 ft-lb).

• The EG26Phas a maximum work capacityof 54 J (40 ft-lb).

- The EG26Pis an electrically controlled actuator with an integral backupmechanical governor. The actuator is usedon units which must continue to functioneven when the electrical governor fails.

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Isochronous Load SharingThere are two major reasons why electronicgoverning systems can share loadsisochronously:

• The governor’s reaction time to speed andload changes is very fast.

• When units are paralleled, auxiliary contactscontrolled by the circuit breaker connect thecontrols through paralleling lines.

This allows the controls to continuouslycompare their real-time positions to each other.

Woodward 2301 Load Share/Speed ControlGovernor characteristics are expanded whenthe 2301 Load Share/Speed Control Modulereplaces the standard/basic 2301 SpeedControl. It adds:

• Isochronous load sharing capability

• Input for an SPM synchronizer (required inautomatic paralleling applications)

Woodward 2301ALoad Share/SpeedControl ModuleThis system further extends the 2301’scapability to include:

• Fuel limiting during engine startup

• Actuator compensation for increased stability

• Protection from voltage spikes and reversepolarity

The starting fuel limit sets the maximumactuator position during engine cranking and isremoved when the engine is running. Thiscreates improved starting and minimizessmoke emissions from the engine. The actuatorcompensation allows the control to work onseveral different fuel systems.

Share/Speed Control ModuleThis electronic governor features zero percent(isochronous) to ten percent droop andincludes:

• Magnetic speed pickup

• Control for parallel/nonparallel operation

• Hydraulic actuator using engine lubricatingoil and internal pump

This system is applied where extremefrequency control is demanded or in automaticparalleling installations. Models include EG3P,EG10P, and EG26P, depending on work forcerequired.


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Caterpillar Electronic Control Module(ECM)The Caterpillar Electronic Control Module(ECM) offers all the advantages ofconventional electronic governors, plusenhanced capabilities to optimize engineperformance. It is available on all Cat 3500Bengines. The ECM combines traditionalgoverning functions with real-time input fromsensors monitoring:

• Coolant temperature

• Fuel pressure

• Oil pressure

• Atmospheric pressures

• Exhaust temperature

• Turbocharger inlet pressure

• Boost pressure

• Injection timing

This information allows the governor tocontinuously adjust to operating conditions.

• System includes:

- Magnetic speed pickup

- Fuel-air ratio control

- Cold start programming

- Independent oil pressure

- Coolant temperature engine protection

- Automatic altitude deration

• Allows custom programming to:

- Improve fuel consumption

- Minimize exhaust emissions

- Improve transient response whileminimizing over/undershoots

• Used where extreme frequency control is demanded or in automatic paralleling installations

• Shares load within five percent

• Droop is adjustable, zero percent(isochronous)to ten percent.

SelectionWhen selecting a governor, always use thesimplest governor that will adequately satisfythe application. To review:

• A mechanical governoris used when theapplication requires:

- Manual paralleling

- Share load within ten percent

- 0.33 percent steady-state regulation

- Fixed droop of three percent

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• The PSG governorcan be used to satisfythe following conditions:

- Manual paralleling

- Share load within five percent

- 0.25 percent steady-state regulation

- Adjustable droop zero to seven percent

- Isochronous capability for single unitoperation

• The criteria for using a UG8D governor isthe same as for the PSG, except:

- It produces more work force and is usedwith larger engines

- It is available in two versions — one forsingle unit operation and one for paralleloperation

• The criteria for using a 3161 governoris similar to the UG8D, but:

- It utilizes engine lubricating oil

- It delivers better performance

- Only one version is used for allapplications

• An electronic governor is recommended ifthe following are critical:

- Automatic paralleling

- Isochronous load sharing

- Improved response time


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Optimum Performance

Two keys to optimum performance and longservice life are:

• Serviceability

• Preventive maintenance

Adherence to proper generator set maintenancepractices is critical to generator set reliability.Caterpillar publishes guidelines and serviceintervals for every engine and generator model.Reference should be made to these guidelinesfor specific maintenance practices. However,the installation must be designed for ease ofservicing to ensure adequate maintenance.

Location for Serviceability

A generator set should be positioned so servicecan be performed easily. Floor space must beadequate for both routine service and majorengine repair.

• As a rule of thumb, the minimum amount offloor space between engines or a wall shouldbe at least the width of the representativeengine.

• Floor space at the front or back of thegenerator set must be adequate for engineremoval or removal of any of its majorcomponents — either by forklift or crane.

• Camshaft or crankshaft removal on manyengines requires an area at one end of theengine equal to the engine length.

Overhead clearance(between top of engineand ceiling or nearest obstruction) shouldpermit the removal of cylinder heads, exhaustpiping, etc. With larger engines adequate areashould be provided to permit use of a chainhoist or overhead crane to remove heaviercomponents.

ExpansionWhen determining the location of a generatorset, future expansion should be considered. Aninstallation should be designed so additionalunits can be added with minimum effort.

Preventive Maintenance

Inspection, test, and maintenance programsmust be carefully planned and carried out onschedule. Poorly maintained equipment can bevery unreliable. Load increases must becarefully monitored. Overloads, if sustained,can cause failure even though maintenance isgood.

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Preventive maintenance of generator sets willvary depending on configuration and usage.However, areas that require easy accessinclude:

• Batteries

• Oil drain

• Oil filters

• Fuel filters

• Coolant

• Air cleaners

Batteries should be positioned so water caneasily be added, and battery cables andterminals can be cleaned to assure goodcontact.

With an engine mounted radiator, sufficientarea above the radiator is required to addcoolant.

A remote-mounted radiator requires periodiccoolant levelinspectionsand convenientaccess is a must. Depending on the radiatorlocation, a stairway or permanent ladder maybe required.

Air filter replacement intervals will vary withengine usage. The area required to replace afilter will be determined by the filter size andlocation.

SERVICING

Generator Set Installation Fundamentals

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