Water Flow

Gas EnginesApplication andInstallationGuide

G3600

● Cooling Systems

● Heat Recovery

● Lubrication System

LEKQ7255 (Supersedes LEKQ2460) 8-97

G3600 Cooling SystemsBasic System Configurations

Standard Cooling SystemCombined Heat and Power Cooling System (CHP)Low Energy Fuel Engine Cooling SystemHigh Temperature Cooling SystemSpecial Cooling Systems

Basic Operating ParametersRecommended Temperature Rise Recommended Inlet PressuresTemperature LimitsPressure LimitsFlow LimitsHeat RejectionFlow CalculationsG3600 Cooling System Design Procedure

Types of Cooling SystemSystem Design Requirements

Temperature RegulatorsInlet Controlled Cooling SystemsOutlet Controlled Cooling Systems

Additional External System ResistancesSystem VolumeMinimum Pump Inlet PressureExpanse TanksFull Flow and Remote Flow Expansion TanksExpansion Tanks for Inlet and Outlet Controlled

SystemsSizing Expansion TanksSystem PressuresAttachment Expansion TankFilling and VentingDe-aeration

RadiatorsRemote Mounted RadiatorsRadiator Design Criteria

Heat ExchangersHeat Exchanger Design Criteria

Submerged Pipe CoolingSubmerged Pipe Design Criteria

Cooling TowersTypes of Cooling TowersCooling Tower Design Criteria

Aftercooler Heat Exchanger SizingInterconnection of EnginesFlexible ConnectionsPiping SupportsJacket Water HeatersCleanliness and StrainersServiceability and Isolation ValvesSystem MonitoringCustomer Connections

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Cooling Systems

As with all internal combustion enginesCaterpillar G3600 engines produce heat as aby-product of combustion. As a general rule,20–40% of the energy input into an enginemust be removed by the cooling system. Thethree basic systems that reject this heat arethe aftercooler, oil cooler and jacket watercircuit. Each of these systems have specificrequirements that must be met in order toprovide a well designed cooling system.

All the pressure and temperature values inthis publication are gauge values unlessotherwise specified. All units are in the Metricconvention with English equivalents inparentheses, i.e. meter (feet). Additionalcooling systems topics related to heatrecovery applications are covered in the nextchapter on Heat Recovery.

Basic System ConfigurationsCaterpillar G3600 Engines offer differentcooling system configurations and options tofulfill the customer’s needs. These coolingsystem configurations will be discussedseparately in the following sections. Thecooling system design for the differentconfigurations to calculate flows,temperatures and pressure drops across thedifferent circuits is explained in thesubsequent sections. The design of anycooling system configuration should adhere tothe limits specified in the Temperature Limits,Pressure Limits and Flow Limits sections andto the guidelines for the quality of the coolantspecified in the Water Quality section in theHeat Recovery chapter. Heat Recoverysystems should follow design guidelinesspecified in the Heat Recovery chapter.

The schematics in the following sectionsprovide a functional layout of the differenttypes of cooling systems and do not indicatethe scope of supply or specifications of thecomponents in the system. The variousfactory supplied or available components ofthe cooling system and those that must besupplied by the customer are shown in theCustomer Connections section. The coolingsystem weld flanges and sizes for customerconnections points for all configurations are

also given in the Customer Connectionssection. For more information on coolingsystem options please refer to the G3600Price List.

Standard Cooling SystemThe standard cooling system cools the enginejacket on one circuit and aftercooler and oilcooler on the other. The aftercooler and oilcooler are connected in parallel. This systemis available with the option of either an inletcontrolled or an outlet controlled system.

The inlet controlled system, see Figure 1,regulates the jacket water inlet temperature toa minimum of 83°C (181°F) or 93°C (199°F)and aftercooler-oil cooler circuit inlettemperature to a minimum of 32°C (90°F) or54°C (130°F) by factory supplied regulators.

The outlet controlled system, see Figure 2,regulates the jacket water outlet temperatureto a minimum of 88°C (190°F) or 99°C(210°F) and the aftercooler-oil cooler circuitoutlet temperature to a minimum of 64°C(147°F) by factory supplied regulators.Generally, inlet control is preferred for heatexchanger cooled systems and outlet controlis used for radiator cooled systems. Refer tothe section on Selection of Inlet or OutletControlled Systems for more information oninlet and outlet controlled systems. Theconnections for the A, B and C ports of thetemperature regulator housing are explainedin the section on Inlet Control and OutletControl.

The jacket water circuit and the aftercooler-oilcooler circuit need a minimum expansionvolume provided by separate expansion tanksor integral with radiators header tanks. Referto section on Expansion Tanks for differenttypes of expansion tanks, sizing guidelinesand information about factory providedexpansion tanks. Vent lines are required onboth circuits to return to the expansion tankand eliminate air traps in the circuit. Refer tothe section on Venting and Filling forrecommended vent line sizes and ventinglocations.

The Figures 3 & 4 show a pictorial view of theStandard Cooling Systems on G3600 engines.Additional schematics of the standard coolingsystem with remote flow expansion tank are

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Turbo

Engine Jacket

Jacket WaterPump

Oil Cooler

Aftercooler

AC-OC Pump

VentLine

Jacket WaterHeat Exchanger

Full FlowExpansion Tank

MixerBox


VentLineG3606 &G3608 Only


83°C (181°F)93°C (199°F)

32°C (90°F)54°C (130°F)

AB

C

AB

C

TemperatureRegulator


AC-OC CircuitHeat Exchanger

RawWater In

Raw WaterOut

Raw WaterIn

Raw WaterOut

Figure 1. G3600 Standard Cooling System-Inlet Controlled (with full flow expansion tank).

Turbo

Engine Jacket

Jacket WaterPump

Oil Cooler

Aftercooler

AC-OC Pump

VentLine

Jacket WaterRadiator


MixerBox




88°C (190°F)99°C (210°F)

64°C (147°F)

AB

C

AB

C



AC-OC CircuitRadiator

Figure 2. G3600 Standard Cooling System-Outlet Controlled (with full flow expansion tank).

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Figure 3. Standard Cooling System – G3606 & G3608 engines.

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Figure 4. Standard Cooling System – G3612 & G3616 engines.

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given in the section on Expansion Tanks forInlet and Outlet Controlled Systems.

Combined Heat and Power CoolingSystem (CHP)In applications where the heat energy fromvarious engine components is used to providehot water for domestic and industrial endusers, the aftercooler, oil cooler and enginejacket are all cooled with the same cold watercircuit. Typically the raw water in theseapplications is water from the local utility,referred to as district water. The engine blockshould be cooled by treated water only, so forthese Combined Heat and Power applicationsthe engine jacket circuit is cooled by treatedwater in a closed circuit with a heatexchanger. The district water recovers thejacket water heat load from the heatexchanger. The Combined Heat and PowerCooling System is currently offered only onG3612 and G3616 engines.

The jacket water circuit is inlet controlled to aminimum of 93°C (199°F) with factorymounted temperature regulators, enginemounted pump, expansion tank and heatexchanger. The external system relies ondistrict water pressure to flow water through

the circuit. The aftercooler and oil cooler aredirectly cooled by district water, see Figures 5& 6. The aftercooler-oil cooler circuit requiresa customer provided booster pump and doesnot require a temperature regulator. Theautomatic derating system on the enginestarts to derate the engine when theaftercooler water inlet temperature increasesbeyond 32°C (90°F). The inlet watertemperature to the aftercooler in this systemshould not exceed 70°C (158°F).

The jacket water circuit in this system isdesigned as a closed circuit to control thequality of the coolant used in the enginejacket. The aftercooler and oil cooler cantolerate higher amounts of contaminants thanthe jacket water circuit, permitting districtwater to be used directly in them. Foradditional design guidelines to be followed forthe CHP cooling system, refer to the sectionon Design Criteria for Standard TemperatureSystems in the Heat Recovery chapter. Thegeneral guidelines for the water quality foruse in G3600 engines is given in the WaterQuality section in the Heat Recovery chapter.Strainers should be installed permanently inthe aftercooler and oil cooler circuit toprevent entry of debris into the components

Turbo

Engine Jacket

JW Pump

District Water In

Motor DrivenPump

M

70°C (158°F)Maximum

FactoryOrifice

VentLine


Expansion Tank93°C (199°F)

AB

C


Exhaust HeatExchanger

Second Stage

Exhaust HeatExchangerFirst Stage

District WaterOut

Figure 5. G3600 Combined Heat and Power Cooling System - Option A.

Oil CoolerAftercooler

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which can easily clog the water passages. Therequirement for strainers in the coolingsystem is given in the section Cleanliness andStrainers.

Low Energy Fuel Engine CoolingSystemEngines operating with landfill gas, digestergas or any other low energy fuel need tomaintain higher cooling circuit operatingtemperatures for long engine and oil life. Thishelps to prevent condensation of acids formedduring combustion in the oil. On the LowEnergy Fuel Engine cooling system, seeFigure 7, the jacket water is outlet controlledto a minimum of 110°C (230°F) and theaftercooler-oil cooler circuit is outletcontrolled to a minimum of 64°C (147°F) withfactory supplied temperature regulators.Engine mounted pumps supply water for boththe jacket water circuit and the aftercooler-oilcooler circuit.

The expansion volume for both jacket waterand the aftercooler-oil cooler circuit should beprovided and is typically provided in theradiator tanks. This cooling system must bepressurized to prevent steam formation at thishigh operating temperatures and appropriate

expansion tank cap or radiator cap should beused to maintain system pressure. Refer tothe section Pressure Limits for minimum andmaximum system operating pressures andsection on Minimum Pump Inlet Pressure forpump inlet pressures.

High Temperature Cooling SystemThe ability to produce low pressure steam orhigh temperature water is a necessity forsome cogeneration applications. The G3600High Temperature Cooling System, seeFigure 8, is designed to provide a maximumoutlet temperature of 130°C (266°F) on thejacket water circuit. The aftercooler-oil coolersystem is similar to that of the StandardCooling System can be inlet controlled to aminimum of 32°C (90°F) and 54°C (130°F) oroutlet controlled to 64°C (147°F). A customersupplied pump and temperature regulatingsystem is required to maintain flow throughthe jacket water circuit and the 130°C (266°F)water leaving the engine can be flashed tosteam in an external boiler or used in theliquid phase. Steam formation inside theengine jacket is not allowed at any time andthe control system will shut the engine downif there is any drop in coolant pressure whichleads to steam formation. The operating

Turbo

Engine Jacket

JW Pump

District Water In

MotorDrivenPump

M

70°C (158°F)Maximum

FactoryOrifice

VentLine


Expansion Tank93°C (199°F)

AB

C


Exhaust HeatExchanger

Second Stage

Exhaust HeatExchangerFirst Stage

District WaterOut

Figure 6. G3600 Combined Heat and Power Cooling System - Option B.

Aftercooler Oil Cooler

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Turbo

Engine JacketJacket Water

Pump

Oil Cooler

Aftercooler

AC-OC Pump

Vent Line

MixerBox

Vent Lines (G3606 & G3608 Only)

Vent Lines (G3612 & G3616 Only)

110°C (230°F)

64°C (147°F)




A C

C


Figure 7. G3600 Low Energy Fuel Engine Cooling System.

Engine Jacket

Remote MountedElectric Pump

PressureSwitch

CondensateIn

Steamto Load

Pressure &TemperatureSensors 110°C (230°F)

Steam Separator

Figure 8. G3600 High Temperature Cooling System.

Oil Cooler

Aftercooler

AC-OC Pump

MixerBox




32°C (90°F)54°C (130°F)

AB

C



RawWater In

Raw WaterOut

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pressure in the system should be maintainedabove the minimum specification to preventwater from vaporizing to steam inside theengine which causes serious damage toengine components. If the system results in acombined static and dynamic head of over460 kPa (67 psi) at the engine outlet, use aheat exchanger to isolate the engine from thesystem’s high static and dynamic heads. Insizing the jacket water pump, heat exchangersand other cogeneration equipment, adhere tolimits specified in the Temperature Limits andPressure Limits sections. The designguidelines for the High Temperature CoolingSystem are given in the High TemperatureSystem section of the Heat Recovery chapter.The Heat Recovery section also has somemore recommended configurations for heatrecovery circuits.

Two Stage Aftercooler Cooling SystemsThe two stage aftercooler, currently offeredfor G3612 and G3616 engines, is intended toprovide high temperature heat recovery forElectric Power Generation (EPG) applicationsand reduce overall radiator sizing for GasCompression applications. There are twocoolant stages on the two stage aftercooler,the first coolant stage uses high temperaturecoolant to cool the charge air to anintermediate temperature and the secondstage cools the air down to engine ratingrequirements. The two stage aftercooler canalso allow much higher coolant inlet pressureto both stages than the single stageaftercooler. The two stage aftercooler hasround tubes on the coolant side withremovable end tanks. The coolant tubes aremechanically cleanable.

There are a variety of cooling systemsavailable for use with the two stageaftercooler on the G3612 and G3616 engines.Two of the most common and distinctconfigurations are explained in this section.There are a total of eight configurations ofcooling systems offered in the G3600 PriceList for use with the two stage aftercooler.Contact the factory for more details on thesecooling systems.

The most appropriate cooling system for atwo stage aftercooler engine in a Combined

Heat and Power application is shown inFigure 9. This configuration provides fourdifferent circuits to make optimum use of theheat recovery capabilities of each of thecooling system components on the enginewith a two stage aftercooler. The oil coolerand first stage of aftercooler require acustomer supplied pump to circulate coolantthrough them. The jacket water circuit issimilar to the jacket water system in theStandard Cooling System. The aftercoolersecond stage coolant inlet temperature isregulated to a minimum of 32°C (90°F) by atemperature regulator. The aftercooler firststage coolant inlet temperature can vary from45°C (113°F) to 95°C (203°F). The oil cooleris on its own circuit and the maximum inlettemperature to this circuit is 54°C (130°F).

The second two stage aftercooler coolingsystem configuration shown in Figure 10 isintended to combine the aftercooler first stageheat load with the jacket water to reduce andoptimize radiator sizing for the completeengine installation. The second stageaftercooler and oil cooler are cooled inparallel, similar to the Aftercooler–Oil Coolercircuit in Standard Cooling System. Thejacket water–aftercooler first stage can becooled by coolant at minimum inlettemperatures of either 83°C (181°F) or 93°C(199°F). The oil cooler–second stageaftercooler circuit has minimum coolant inlettemperatures of either 32°C (90°F) or 54°C(130°F) depending on the engine rating.

Special Cooling SystemsThe systems discussed so far are the variousproduction configurations offered. If anapplication requires special features or aunique cooling system configuration, orderthrough the factory using Special EngineeringRequest (SER).

The schematic of one such special coolingsystem with an engine mounted combinedjacket water heat exchanger and plate fin oilcooler is shown in Figure 11.

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EngineJacket

JW Pump

CustomerPump

Stage IMax 95°C,1000 kPa

Stage II32°C or 54°C

1000 kPa

300 kPaAC Pump

ExpansionTank

(CustomerProvided)


To Heat Exchangeror Heating Plants

Oil Cooler

CustomerPump

Max 54°C1000 kPa

Aftercooler

Stage I

Stage II

83°Cor 93°C

ExpansionTank


From HeatExchanger

To HeatExchangeror Heating

Plants

To HeatExchanger

Mixer Box

Mixer Box

Stage I

Stage II

Aftercooler

Oil Cooler

32°C or 54°C1000 kPa Max

300 kPa Pump Expansion Tank(Customer Provided)


EngineJacket

To HeatExchanger

To HeatExchanger

From HeatExchanger

From HeatExchanger

JWPump

83°Cor 93°C

ExpansionTank


Figure 9. Inlet Controlled Cooling System.

Figure 10. Two Stage Aftercooler cooling systems for G3612 & G3616 Gas Compression Applications.

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Basic Operating ParametersAll engine cooling circuits are designated bythe inlet or outlet temperature to that circuit.The basic operating parameters available forthe G3600 Engine cooling systems are:

Standard and CHP Cooling SystemsAftercooler-Oil Cooler Circuit temperatures

a) Inlet 32°C (90°F) or 54°C (130°F)b) Outlet 64°C (147°F)

Two Stage Aftercooler Temperaturesa) Stage 1 45°C (113°F) to 95°C (203°F)b) Stage 2 32°C (90°F) or 54°C (130°F)

Jacket Water Circuit temperaturesLow Compression Ratio engines (9:1)a) Inlet 83°C (181°F)b) Outlet 88°C (190°F)High Compression Ratio engines (11:1)a) Inlet 93°C (199°F)b) Outlet 99°C (210°F)

Low Energy Fuel Engine Cooling SystemsAftercooler-Oil Cooler Circuit temperatures

Outlet 64°C (147°F)

Jacket Water Circuit temperaturesOutlet 110°C (230°F)

High Temperature Cooling SystemsAftercooler-Oil Cooler Circuit temperatures

a) Inlet 32°C (90°F) or 54°C (130°F)b) Outlet 64°C (147°F)

Jacket Water Circuit temperaturesOutlet 130°C (266°F)

Engine Ratings are based on aftercooler watertemperature, jacket water temperature,compression ratio and ambient conditions.

Recommended Temperature RiseFor efficient and trouble free operation ofCaterpillar G3600 Engines the followingvalues are recommended for the temperaturerise across the various cooling systemcomponents.

Aftercooler-Oil Cooler G3616 10°C (18°F) G3612 8°C (14.5°F) G3608 9°C (16°F)

Engine Jacket

Figure 11. G3600 Special Cooling System -Combined JW Heat Exchanger and Oil Cooler.

Aftercooler

AC-OC Pump

MixerBox


VentLine

32°C (90°F)54°C (130°F)

AB

C



RawWater In

Raw WaterOut

AB

C


Full FlowExpansion TankJW Pump

Oil Cooler

Raw WaterIn

Raw WaterOut80°C (176°F)

Maximum

93°C (199°F)


G3606 7°C (12.5°F)Aftercooler (Single Stage)

G3616 10°C (18°F) G3612 8°C (14.5°F) G3608 9°C (16°F) G3606 7°C (12.5°F)

Aftercooler (Two Stage)Stage 1 10°C (18°F) Stage 2 8°C (14.5°F)

Oil Cooler G3616 8.5°C (15°F)G3612 7.5°C (13.5°F)G3606 & G3608 6°C (11°F)

Jacket Water 4.5°C (8°F)

Recommended Inlet PressuresThe recommended range of operatingpressure at the inlet of different circuits are:

Aftercooler-Oil Cooler StandardCooling System 250–330 kPa (36–48 psi)

Two Stage Aftercooler Cooling SystemStage 1 up to 1000 kPa (145 psi)Stage 2 up to 1000 kPa (145 psi)

Jacket water circuitStandard Cooling 225–350 kPa (33–51 psi)Low Energy Fuel

Cooling System 300–400 kPa (44–58 psi)High Temperature

Cooling System 300–460 kPa (44–67 psi)

Note: These values of RecommendedTemperature Rise and Recommended InletPressures are specified to make most efficientuse of the cooling system. In general, for acooling system more flow is always better aslong as the values are within the maximumlimits as specified in the section on FlowLimits. Higher values of temperature rise orinlet pressure are also allowed if needed forspecific sites, adhere to the maximum limitsspecified in the section on Temperature Limitsand Pressure Limits for these.

Temperature LimitsCaterpillar G3600 Engines should not beoperated for any reason beyond the followingmaximum temperature differential for coolantacross the different circuits.

Aftercooler-Oil Cooler 12°C (22°F)Aftercooler (Single stage) 12°C (22°F)

Aftercooler (Two stage)Stage 1 12°C (21°F)Stage 2 11°C (20°F)

Oil Cooler 10°C (18°F)Jacket Water 6°C (11°F)

The maximum limits for inlet or outlettemperature for coolant in the differentcircuits are:

Aftercooler (Single stage) inlet 70°C (158°F)Aftercooler (Two stage) inlet

Stage 1 95°C (203°F)Stage 2 54°C (130°F)

Oil Cooler (Shell & tube) inletTwo cooler system

G3606 & G3608 54°C (130°F)G3612 & G3616 32°C (90°F)

Three cooler system 54°C (140°F)Jacket Water outlet,

Non-pressurized 99°C (210°F)Pressurized

28–48 kPa (4–7 psi) 105°C (221°F)Low Energy Fuel Engine Cooling Systems

83–110 kPa (12–16 psi) 110°C (230°F)High Temperature Cooling Systems

250–460 kPa (36–67 psi) 130°C (266°F)The minimum limit for inlet coolanttemperatures to the various circuits are:

Aftercooler inlet 25°C (77°F)Oil cooler inlet 0°C (32°F)Engine Jacket inlet 0°C (32°F)

The maximum allowable lubricating oiltemperature to the engine is 85°C (185°F).Failure to abide by this could result in poorengine performance and or engine failure.

Pressure LimitsThe following combined static and dynamicpressure limits to the engine cooling systemcomponents must be maintained to preventdamage to the engine or its components andensure good heat dissipation.

Maximum limits:Aftercooler (Single stage) 330 kPa (48 psi)Aftercooler (Two stage)

Stage 1 1000 kPa (145 psi)Stage 2 1000 kPa (145 psi)

Oil cooler (Shell & tube) 1000 kPa (145 psi)Engine Block 461 kPa (67 psi)Pump inlet 145 kPa (21 psi)

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Caterpillar Expansion Tank 150 kPa (22 psi)Expansion Tank Pressure Cap 49 kPa (7 psi)

Note: Minimum suction pressures for enginemounted aftercooler-oil cooler pump andjacket water pump at various operatingtemperatures are given in the sectionMinimum Pump Suction Pressure.

Flow LimitsThere are some established maximum flowlimits for specific Caterpillar G3600 enginecomponents to prevent erosion of the coolantpassages.

Aftercooler (single stage) lpm (gpm)G3606 & G3608 800 (212)G3612 & G3616 1475 (390)

Oil cooler (shell & tube) 1000 (265)Aftercooler–Oil Cooler (Standard)

G3606 & G3608 1800 (476)G3612 & G3616 2475 (655)

Aftercooler (Two stage)Stage 1 1000 (265)Stage 2 1000 (265)

Cylinder block (Engine jacket)G3606 & G3608 1600 (422)G3612 & G3616 3000 (794)

Heat RejectionBefore a cooling system can be designed, thedesigner must understand how much heat isbeing rejected by each of the enginecomponents. This information is generallyavailable in the TMI and Technical Manualavailable for the G3600 engines. The followingguide will help the designer in interpretingand applying the heat rejection data.

The theory of heat balance states that heatinput into the engine should equal the sum ofthe heat output and work output.

Formula:

Total Heat Input = Work output + Jacket Water heat rejection +Aftercooler heat rejection +Oil Cooler heat rejection +Total Exhaust heat load +Radiation

• Total Heat Input can be calculated in

MJ/min = BSFC (MJ/kw2hr) 3 work (kw)60 min/hr

or

Btu/min = BSFC (Btu/hp2hr) 3 hp60 min/hr

Total fuel consumed in SCMH (SCFH) isobtained by dividing the total heat input bythe heat content of the fuel, Lower HeatingValue (LHV) in MJ/SCM (Btu/SCF).

• Work Output is the total horsepowerdeveloped. It is expressed in kW (Btu/min)where one horsepower= 0.7457 kW (42.4 Btu/min)

• Jacket Water heat rejection is the totalamount of heat transferred to the enginejacket cooling circuit.

• Aftercooler Heat rejection is given forstandard conditions of 25°C (77°F)ambient and 150 m (500 ft) altitude. Thisheat rejection increases for higher ambienttemperatures and higher altitudes. OnG3600 engines a constant aftercooler airoutlet temperature is required for theengine. As air temperature into theaftercooler goes up, so does the heat loadthat must be removed. As the ambient airpressure decreases with altitude, theturbocharger must impart more energy tothe incoming air to get it up to the requiredboost pressure. Use the Aftercooler HeatRejection Factors given in the TechnicalManual or G3600 Specification Sheets toadjust for ambient and altitude conditions.Failure to properly account for thesefactors could cause the engine to detonateand shutdown due to overheating.

• Oil Cooler heat rejection is the amount ofheat transferred from the lubricating oil tothe cooling system.

• Total exhaust heat load is the total energyavailable in the exhaust gases when it iscooled from the stack temperature down tostandard conditions of 25°C (77°F). Valuesshown are lower heating values and do notinclude the heat of vaporization.

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• Radiation is the amount of heat energy lossfrom the engine surface into the engineroom or surrounding ambient.

In every calculation using the engine data,there is a tolerance band or a deviation fromnorm. When using the heat rejection data forengine components use the followingtolerances.

Total Heat Input 62.5%Jacket Water heat rejection 610%Aftercooler heat rejection 65%Oil Cooler heat rejection 620%Total Exhaust Heat energy 610%Radiation 625%Recoverable Exhaust 610%

Recoverable exhaust heat is not a separatecomponent of the heat balance equation, but itis the customary number used in heatrecovery calculations. It represents the heatenergy available when cooling the exhaustfrom stack temperature to 177°C (350°F)unless specified otherwise. If exhausttemperature other than 177°C (350°F) isdesired, the recoverable heat can beapproximated by the following formula. Theactual formula used to calculate the TMI datais more complex and requires data notavailable in published sources. The exhaustgas flow given is at standard pressure andstack temperature.

Heat rejection in kW (Btu/min)

Q = Cp 3 M 3 (T1 2 T2)

Cp = Specific Heat of Exhaust Gases:KJ/KG. °C (Btu/lb. °F)1.107 (0.264) for Natural Gas Engines

M = Mass flow of exhaust gaseskg/min (lb/min) from Technical Manual

T1 = Temperature of Exhaust gases fromEngine in °C (°F) from TechnicalManual

T2 = Temperature of Exhaust gases at theoutlet of Heat Recovery Silencer in °C(°F)

Refer to the Heat Recovery chapter for asample calculation of the recoverable exhaustheat energy.

Flow CalculationsThe first step in the design of a coolingsystem is to calculate the flow required foreach circuit to transfer the heat load from theengine components to the Heat Exchangersor Radiators.

Flow (L/min) = Heat Rejection (kW) DT (°C)3 Density (KG/L) 3

Specific Heat (kW.min/KG.°C)

Flow (Gal/min) = Heat Rejection (Btu/min) DT (°F)3 Density (lb/Gal) 3

Specific Heat (Btu/lb.°F)

DT = Outlet Temperature – Inlet Temperaturefor that circuit. Density and Specific Heat canbe used from the following table:

A small tolerance should be added to thiscalculated flow to account for possiblevariances.

Design Flow = Calculated Flow 1 10%

The following table shows the density andspecific heat capacities for the differentcoolant media used in cooling systems. Thevalues on the last column show the Densitymultiplied by the Specific Heat capacity, this isa good indicator of the heat absorptioncapacity of the coolant. Flow calculationsshould be done with the correct coolantproperties to get the right heat transfer.

For engine mounted pumps the externalresistance corresponding to the designcoolant flow for different engine speeds canbe determined from the External Restriction vsCoolant Flow charts given in subsequentsections (see Figures 17–22). For circuits notusing an engine mounted pump use theInternal System Restriction vs Flow charts todetermine the pressure rise required

Densitykg/l

(lb/gal)

Specific HeatkW min/

kg °C(Btu/lb. °F)

Sp. Ht x Den.kW min/l °C(Btu/Gal. °F)

Pure Water 0.98(8.1)

0.071(1.00)

0.0696(8.1)

50% EthyleneGlycol–

50% Water

1.03(8.6)

0.060(0.85)

0.0618(7.31)

50% PropyleneGlycol–

50% Water

1.01(8.4)

0.065(0.92)

0.0657(7.728)

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corresponding to the design coolant flow (seeFigures 23–31).

This data is also available in the TMI. SinceTMI is updated more frequently than thispublication, in the case of conflicting databetween this guide and TMI, use TMIinformation.

The following charts can also be used toverify the flow of coolant by measuring thepressure drop at inlet and outlet of thecircuits. When verifying flow with the charts,it is very important to ensure that thepressure measurements are taken at therecommended locations for accuratecomparison with the given charts. Therecommended pressure measuring locationsfor both Jacket Water and standardAftercooler-Oil Cooler circuit are shown inFigure 12 and for the Aftercooler and Oilcooler individually are shown in Figure 13.The measuring locations for two stageAftercooler are shown in Figure 14. Evensome of the minor components in the coolingsystem like the mixer box and other castingsintroduce significant restriction to flows andshould be appropriately accounted for in thepressure drop measurements. Externalresistance measurements should be takenwith blocked open temperature regulators,with no bypass flow. Recommended pressuremeasuring locations on Engine and customerside of cooling system are also discussed inthe section on System Monitoring.

For G3600 cooling systems provided withCaterpillar package mounted expansion tanksand temperature regulators for the jacketwater system, the internal resistance of theexpansion tank and the temperature regulatorhousing should be subtracted from the jacketwater external restriction value obtained fromthe charts. In these systems the externalresistance available is between the water inletand outlet of the regulator housing as shownin Figure 14. The internal restriction of theexpansion tank and temperature regulatorhousing is given in Figure 15. So, for engineswith module mounted expansion tank andtemperature regulator housing,

Available External Restriction = External Restriction from the chart 2

Internal Restriction from Figure 15 corresponding to the design coolant flow.

G3606 & G3608

G3612 & G3616

Jacket Water External Restriction = P6 – P4Jacket Water Internal Restriction = P5 – P6

Aftercooler-Oil cooler External Restriction = P3 – P1Aftercooler-Oil cooler Internal Restriction = P2 – P3

Figure 12. Measuring points on G3600 Engines forExternal and Internal Restriction

G3612 & G3616 Separate Circuit

Aftercooler Internal Restriction = P2 – P1Aftercooler Internal Restriction = P4 – P3

Figure 13. Internal Restriction Measuring pointsfor Oil cooler and Aftercooler individually

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P2 AC OUTLET

AC INLET

OC OUTLET

OC INLET

P1P4

P3

➤

➤

➤

➤

➤

➤ ➤

➤

➤

➤

➤

➤

➤

➤

➤

➤

➤

➤➤

➤

➤

➤

➤➤

➤

➤

➤➤

➤

➤

➤

➤

➤

➤

➤

➤

➤

➤

P5

P6

P4

P1 P2

P3

➤

➤➤

➤

➤

➤

➤

➤

➤

➤

➤

➤

➤

➤

➤

➤

➤

➤

➤

➤

➤➤

➤

➤

➤

P4

P5

P6

P1P3P2

18

19

TemperatureRegulatorHousing

FromEngine

Jacket Water Circuit External Restriction = P1 – P2(Taken when Temperature Regulators are fully open)

To HeatExchanger

From HeatExchanger

Engine MountedExpansion Tank

P1P2

Figure 15. Jacket External Restriction for Engines with Module Mounted Expansion Tanks.

P2AC Stage 1 Outlet

P1AC Stage 1 Inlet

P3AC Stage 2 Inlet

P4AC Stage 2 Outlet

Aftercooler Stage 1 Internal Restriction = P1 – P2

Aftercooler Stage 2 Internal Restriction = P3 – P4

Figure 14. Internal Restriction Measuring Points for Two Stage Aftercooler.

20

1050

300250200 350 400

1200 1350 1500 1650750

Water Flow

Exte

rnal

Res

tric

tion

25

75

150

225

50

10

20

30

125

200

100

175

250

G3606 & G3608 External Resistance vs. Coolant FlowJacket Water Circuit

900

Figure 17. Refer to Figure 10 for measuring locations..

1000 RPM

800 RPM

750 RPM

900 RPM

kPapsi

L/Min

g/Min

1200 1600 2000 2400 2800 3200400

Water Flow L/Min

Inte

rnal

Sys

tem

Res

tric

tion

KPa

10

15

20

25

30

800

Figure 16. Internal Restriction for Module mounted expansion tank and temperature regulator.

21

2000 2200 2400 2800 30001200

Water Flow

Exte

rnal

Res

tric

tion

KPa

25

75

150

225

50

125

200

100

175

250

G3612 External Resistance vs. Coolant FlowJacket Water Circuit

1400 1600 1800 2600

Figure 19. Refer to Figure 10 for measuring locations.

750 RPM

900 RPM

800 RPM

1000 RPM

10

20

30

psi kPa

350 400 500450 550 600 700650 750 g/Min

L/Min

850 1000 1150 1450 1600400

Water Flow

Exte

rnal

Res

tric

tion

25

75

150

225

50

125

200

100

175

250

G3606 & G3608 External Resistance vs. Coolant FlowAftercooler-Oil Cooler Circuit

550 700 1300


1000 RPM

800 RPM

750 RPM

900 RPM

10

20

30

psi kPa

300250200 350 400100 150 g/Min

L/Min

22

2300 2500 29001500

Water Flow

Exte

rnal

Res

tric

tion

25

75

150

225

50

125

200

100

175

250

G3616 External Resistance vs. Coolant FlowJacket Water Circuit

1700 1900 2100 2700


750 RPM

800 RPM

1000 RPM

900 RPM

10

20

30

psi kPa

400 500450 550 600 700650 750g/Min

L/Min

2000 2200 24001200

Water Flow

Exte

rnal

Res

tric

tion

25

75

150

225

50

125

200

100

175

250

G3612 External Resistance vs. Coolant FlowAftercooler-Oil Cooler Circuit

1400 1600 1800


750 RPM

800 RPM

1000 RPM

900 RPM

10

20

30

psi kPa

350 400 500450 550 600 g/Min

L/Min

23

1200 1400 1800400

Water Flow

Inte

rnal

Sys

tem

Res

tric

tion

0

100

250

50

200

150

300

G3606 & G3608 Internal System Restriction vs. Coolant FlowJacket Water Circuit

600 800 1000 1600


10

20

30

40

psi kPa

300250200 350 400 450g/Min

L/Min

150

2000 2200 24001200

Water Flow

Exte

rnal

Res

tric

tion

25

75

150

225

50

125

200

100

175

250

G3616 External Resistance vs. Coolant FlowAftercooler-Oil Cooler Circuit

1400 1600 1800


750 RPM800 RPM

1000 RPM

900 RPM

10

20

30

psi kPa

350 400 500450 550 600 g/Min

L/Min

24

2200 2400 28001000

Water Flow

Inte

rnal

Sys

tem

Res

tric

tion

0

50

175

25

125

150

100

75

200

G3612 Internal System Restriction vs. Coolant FlowJacket Water Circuit

1200 1400 1600 1800 2000 2600


10

20

psi kPa

15

5

25

300 350 400 500450 550 600 700650 g/Min

L/Min

1100 1250 1550500

Water Flow

Inte

rnal

Sys

tem

Res

tric

tion

0

50

125

25

100

75

150

G3606 & G3608 Internal System Restriction vs. Coolant FlowAftercooler-Oil Cooler Circuit

650 800 950 1400


5

10

15

20

psi kPa

300250200 350 400150 g/Min

L/Min

25

2200 2400 28001000

Water Flow

Inte

rnal

Sys

tem

Res

tric

tion

0

50

225

25

125

175

200

150

100

75

250

G3616 Internal System Restriction vs. Coolant FlowJacket Water Circuit

1200 1400 1600 1800 2000 2600


10

20

psi kPa

15

5

25

300 350 400 500450 550 600 700650 g/Min

L/Min

1800 2000 2400800

Water Flow

Inte

rnal

Sys

tem

Res

tric

tion

0

50

175

25

125

150

100

75

200

G3612 Internal System Restriction vs. Coolant FlowAftercooler-Oil Cooler Circuit

1000 1200 1400 1600 2200


10

20

psi kPa

15

5

25

300250 350 400 500450 550 600 g/Min

26

1100500

Water Flow

Inte

rnal

Sys

tem

Res

tric

tion

10

30

20

60

50

40

70

G3600 Internal System Restriction vs. Coolant FlowOil Cooler (Shell & Tube Type)

600 700 800 900 1000


2 Section Oil Cooler

3 SectionOil cooler

3

4

6

psi kPa

5

2

7

8

250200150 g/Min

L/Min

2100 2300900

Water Flow

Inte

rnal

Sys

tem

Res

tric

tion

0

50

225

25

125

175

200

150

100

75

250

G3616 Internal System Restriction vs. Coolant FlowAftercooler-Oil Cooler Circuit

1100 1300 1500 1700 1900


10

20

psi kPa

15

5

25

300250 350 400 500450 550 600 g/Min

L/Min

27

1100 1300500

Water Flow

Inte

rnal

Sys

tem

Res

tric

tion

30

80

155

55

130

105

180

G3612 & G3616 Internal Restriction vs. Coolant FlowTwo Stage Aftercooler

700 900


5

10

15

20

psi kPa

25

300250200150 g/Min

L/Min

Stage 2

Stage 1

1700500

Water Flow

Inte

rnal

Sys

tem

Res

tric

tion

25

125

75

325

275

225

175

375

G3612 & G3616 Internal System Restriction vs. Coolant FlowSingle Stage Aftercooler

700 900 1100 1300 1500


10

20

30

40

50

psi kPa

300250200 350 400 450 g/Min

L/Min

150

G3600 Cooling System DesignProcedureThe discussion in the previous sections aresummarized in this section to present asimple step by step procedure for design andsizing of cooling systems for G3600 engines.

• Obtain Heat Rejection for any particularcomponent (AC, OC, etc.) from the G3600Technical Manual or PerformanceSpecification Sheets. For cooling systemdesign use the maximum Heat Rejection(nominal 1 tolerance) value.

• Select a temperature rise for the circuit.The section on Recommended TemperatureRise gives recommended values for allcomponents. The temperature rise shouldnot exceed the maximum limits specified inthe Temperature Limits section at any time.

• Depending on the coolant used (water, 50%glycol, etc.), the appropriate density andspecific heat values should be used. Thetable in the section Flow Calculations givesthese values for standard atmosphericconditions. These values can be used forcooling system calculations even at highertemperatures.

• The calculation of the coolant flow isexplained in the section on FlowCalculations. Ensure that the designcoolant flow is below the maximum limitsgiven in the section Flow Limits.

• Once the design coolant flow is obtained,the external resistance values can beobtained if it is a standard AC-OC or JWcircuit with engine mounted pump.Otherwise the flow can be used todetermine the internal system restriction ofthe circuit for sizing external pumps. Ifmodule mounted expansion tank andtemperature regulator is used, correct forits internal restriction.

Types of Cooling SystemThere are two basic types of cooling systems,open and closed. Examples of each are givenbelow.

Open Systems (not recommended):Cooling Tower (without heat exchanger)Spray PondBody of Water

Closed Systems: Radiator Heat Exchanger Cooling tower (with Heat Exchanger) Evaporative Cooler

In the open system, the cooling water isexposed directly to air and is cooled byevaporation and water-to-air heat transfer.About 75% of the total heat is removed byevaporation and 25% by transfer. Thecontinued process of evaporation means thatany scale forming salts present in the waterwill gradually be concentrated and the watermay pickup further contaminants from the air.These impurities can result in the formationof scale on the walls of the coolant passagesin the engine, decreasing the cooling systemefficiency which may result in overheating.Refer to the section on Water Quality forspecifications for coolant acceptability. Opencooling systems are not recommended exceptwhen specific precautions have been taken toaccommodate the above problems in an opensystem, such as using cleanable componentslike aftercooler and oil coolers. Since theseare not presently offered on the G3600engines, the use of open cooling system isrestricted.

In the closed system, proper water treatmentcan virtually eliminate scale formation andcorrosion. The cooling water does not comeinto direct contact with the air. It is cooled bya process of heat transfer to a cooler medium,usually air or water. The amount of water inthe engine closed system is relatively smalland confined, can be economically treated.

28

System Design RequirementsEngine cooling systems must:

• Maintain a required minimum operatingtemperature

• Provide sufficient water pump inletpressure to prevent pump cavitation

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

• Allow filling without air entrapment (falsefill)

• Reject heat from the jacket water andaftercooler-oil cooler circuit at greatestengine load, highest ambient temperatureand altitude

The following topics describe how these areaccomplished by following recommendedcooling system design practices.

Temperature RegulatorsThe function of the temperature regulator isto control minimum operating temperaturesof the engine cooling system. All coolingsystems must have a method of maintainingminimum operating temperature. If minimumoperating temperature is not maintained,severe maintenance problems may result.

Factory supplied temperature regulators areprovided for most applications for G3600engines either assembled with the factorypackaged cooling system or shipped loose tobe connected with the customer’s coolingsystem. The factory supplied temperatureregulator is only capable of controlling theminimum temperature of the cooling circuitand can not control the maximumtemperature. Once the temperature of thecooling system has reached the full opentemperature of the regulator, the regulatordoes not bypass any flow and this condition isknown as full open flow. The enginemonitoring system provides warnings andshutdown for high water temperature oncooling systems.

There are two basic methods of thermostaticcontrol of minimum operating temperature incooling systems, inlet controlled and outletcontrolled.

Inlet Controlled Cooling SystemsInlet controlled cooling systems, seeFigure 32, are designed to provide aconsistent temperature at the inlet of thecooling circuit, jacket water or aftercooler-oilcooler. This is done by placing the sensingbulb of the temperature regulator in the inletflow to the circuit, see Figure 33. If the inletflow from the heat exchanger is cooler thanthe minimum opening temperature of the

29

EngineThermostat

C

B

A

Return

Outlet

Heat Exchanger

ExpansionTank

Engine DrivenJ. W. Pump

Piping

Part of engineCaterpillar suppliedwhen heat exchanger ismounted on oilfield base

A – B: Cold FlowA – C: Full External Flow

Figure 32. Inlet Controlled Cooling System.

temperature regulator, the regulator thenbalances the cool water from the heatexchanger with the bypass flow (hot waterdirectly from the engine) to provide thecorrect temperature water at the inlet.

As shown on Figure 33, for a factory suppliedtemperature regulator assembly, the bulb sideof the temperature regulator housing, A, isconnected to the inlet of the pump for an inletcontrolled system. The port B is connected tothe tee which gets the supply from the engineand sends it to the heat exchanger. The otherport, C, is connected to the cold water supplyfrom the heat exchanger. The inlet controlledsystems, as will be explained in thesubsequent section, are strongly

recommended for G3600 engines cooled by aheat exchanger or cooling tower.

Outlet Controlled Cooling SystemsOutlet controlled cooling systems, seeFigure 35, are designed to provide a constantoutlet temperature of coolant from the engine.This is accomplished by placing the sensingbulb of the regulator on the outlet side of thecircuit, see Figure 34 and controlling the flowbetween the bypass circuit and the coolingcircuit. As the outlet temperature becomeshigher than the opening temperature of theregulator, water is allowed to flow to thecooling system. If water is too cool, the wateris directed through the bypass and isrecirculated through the engine without beingcooled.

30

Outlet

BypassLine

Engine DrivenJ.W. Pump

ReturnA

B

C

Rad

iato

r

EngineThermostat

Piping

Part of engineSupplied by packageror radiator supplier

B – A: Cold FlowC – A: Full External Flow

Figure 35. Outlet Controlled Cooling System.

Figure 33. Inlet Controlled Regulator layout.

FromEngine

TemperatureRegulator Housing

From HeatExchanger

AB

C

Bulb Side

To Engine/Expansion Tank

To HeatExchanger

Figure 34. Outlet Controlled Regulator layout.

FromEngine

TemperatureRegulator Housing

FromRadiator

A B

C

Bulb Side

To Engine

ToRadiator

31

For outlet control systems, the factorysupplied temperature regulator assembly isplumbed with the bulb side of the housing, A,connected to the outlet of the engine asshown in Figure 34. The port B is connectedto the tee which branches to the inlet of thepump and accepts the cold water from theradiator. The port C is connected to the linesending the hot water to the radiator.

Factory supplied temperature regulators areassembled inside the same housing for bothinlet control and outlet control. If theregulator assembly is shipped loose to beplumbed at the customer site, care should betaken to plumb the temperature regulatorhousing appropriately for inlet or outletcontrol system. Please refer to the installationdrawing of the specific regulator assembly toplumb the connections accordingly. Some ofthe frequent cooling system problems are aresult of wrong connection of regulatorhousing in the circuit.

Outlet controlled systems, as explained in thenext section, are recommended for use withG3600 Engines which are cooled by aradiator.

Selection of Inlet or Outlet ControlledSystemsThere are certain applications that are bettersuited for either inlet controlled or outletcontrolled systems. In general, inletcontrolled systems work well with heatexchangers and outlet controlled systemswork best with radiators. To understandwhich is the better choice for the systemunder consideration the following itemsshould be considered.

A shunt line is required on inlet controlledsystems that do not use a full flow expansiontank. This is to prevent the possibility ofpump cavitation by providing a positive headon the suction side of the pump. Outletcontrolled systems generally do not have thisrequirement as full head pressure is notrestricted by the temperature regulator and ashunt line is not required.

Full engine outlet pressure is present at alltimes on the heat exchanging device for theinlet controlled system. This can be a concern

with a radiator, since the outlet pressures arein the same range as the structural capabilityof some solder tube radiators. Outletcontrolled systems tend to isolate the coolerfrom the pressure during bypass operation.

Nuisance high temperature shutdowns can beexperienced with an inlet controlled system ifthe system flow is inadequate. This is trueeven if there is adequate cooling capacity inthe system. The inlet controlled systemprovides a fixed temperature coolant to theengine independent of the amount of flow. Ifthe flow is low, the temperature rise acrossthe engine will be high. If the temperaturerise is higher than the maximum allowableoutlet temperature the engine monitoringsystem will shut the engine down. An outletcontrolled system would not have thisproblem since it will reduce the bypass flowand increase cooler flow. The temperaturerise across the engine may be higher thandesired for a short period until the systemstabilizes but the engine will continue tooperate.

Thermal shock is caused when thetemperature regulator tries to open and closeto maintain temperature on an outlet controlsystem. Thermal shock of the engine is apotential problem with an outlet controlledsystem because the coolant must passthrough the engine before the temperatureregulator detects the coolant temperature. Ifcool return temperature of coolant is possiblethe inlet controlled system will prevent thethermal shock to the engine components. Anoutlet controlled system with a full flowexpansion tank will also prevent this problem.

The deficiencies of both inlet and outletcontrolled systems can be overcome withproper system design, specifically a full flowexpansion tank. Engine side system pressuresare usually the highest at full bypass. Systempressures are lowest when nearly equal flowis in bypass and the cooler flow. Systempressures at full open flow is near maximumand should match external resistance targets.The external pressure drop of both systemsare identical at full open flow condition.

The selection of expansion tanks for inlet andoutlet controlled tanks is discussed in the

section on Expansion Tanks for lnlet andOutlet Systems with the help of someschematics.

Line VelocitiesCaterpillar G3600 Cooling systems aredesigned for the following maximum linevelocity limits.

m/sec (ft/sec) Pressurized lines 4.5 (15.0) Pressurized thin walled tubes 2.5 (8.0)Suction lines (Pump inlet) 1.5 (5.0)Low velocity de-areation line 0.6 (2.0)

Observing these guidelines will help toprevent erosion of the internal passages of theengine and other engine cooling systemcomponents and extend its life. Figure 36 canbe used to calculate water velocity in a pipe ortube.

Additional External SystemResistancesPiping and heat transfer equipment resistcooling water flow, causing an externalpressure, referred to as head, which opposesthe pump. Cooling water flow is reduced asexternal head increases. Total systemresistance to flow must be limited to ensureadequate flow. Resistance to flow isdetermined by the length of pipe, number andtype of fittings and valves used, coolant flowrate and losses contributed by the heattransfer devices.

When designing an engine cooling system,the pressure drop (resistance) in the externalcooling system can be calculated by totalingthe pressure drop in each of the system’scomponents. Figures 37 and 38 can be used todetermine pressure drop through pipe fittingsand valves. Figure 36 can be used todetermine flow velocities in tubes and pipesfor a given volume of flow. The velocitiesshould remain within limits set forth in thesection Line Velocities. Suppliers of othercomponents such as strainers and heattransfer equipment can provide the requireddata on their components.

The external head allowable if an enginemounted pump is used is shown in the sectionExternal Resistance vs Flow. If the external

head required is higher than that provided bythe engine mounted pumps, use externalpumps with additional pressure capacities.For external customer supplied pump use thedata from Internal System Restriction vs Flowsection to obtain the external head, which isthe difference pump pressure rise and systemrestriction. Figure 54 in the System Monitoringsection shows the preferred location formeasuring internal system restriction andexternal restriction. There are ports providedfor measuring pressure drops at somelocations on the engine and there are somerecommended locations on the customercooling system for providing ports.

System VolumeThe engine coolant volume for the jacketwater and combined aftercooler-oil coolercircuit is given in the following table. Thisdata can also be found in the TMI.

The Jacket water circuit engine volume givendoes not include the expansion tank volume.

The volumes for all other components such asexpansion tanks, radiator and customer pipingshould be added to get a total system volume,if needed for filling and other purposes.

JW CircuitEngine Volume

L (Gal)

AC–OC CircuitEngine Volume

L (Gal)

G3606 60 (16) 340 (90)

G3608 60 (16) 470 (124)

G3612 64 (17) 670 (177)

G3616 72 (19) 900 (238)

32

33

Figure 36. Velocity vs. Flow.

34

gpm L/s5

1015202530354045506070758090

100125150175200225250275300325350375400425450475500750

10001250150017502000

3 in. (76.2 mm)

10 in. (254 mm)

0.070.150.250.380.540.710.911.161.381.922.572.933.284.084.967.5510.5 14.1 17.8 22.3 27.1 32.3 38.0 44.1 50.5

0.190.210.230.260.280.591.231.512.132.803.59

2 1/2 in. (63.5 mm)

9 in. (228.6 mm)

0.050.170.370.610.921.291.722.202.763.324.656.207.057.909.8012.0 17.6 25.7 34.0 43.1 54.3 65.5

0.180.210.240.280.310.350.380.420.460.981.672.553.524.706.02

2 in. (50.8 mm)

8 in. (203.2 mm)

0.160.501.071.822.733.845.106.608.209.9013.9 18.4 20.9 23.7 29.4 35.8 54.0 76.0

0.150.190.240.270.320.370.430.480.550.610.680.750.821.762.974.486.247.45

10.71

1 1/2 in. (38.1 mm)

7 in. (177.8 mm)

0.401.433.055.207.8511.0 14.7 18.8 23.2 28.4 39.6 53.0 60.0 68.0 84.0

102.0

0.170.220.280.350.430.510.600.680.770.891.011.141.261.461.543.235.598.3911.7

1 1/4 in. (31.75 mm)

6 in. (152.4 mm)

0.843.056.5011.1 16.6 23.0 31.2 40.0 50.0 60.0 85.0

113.0 129.0 145.0

0.170.260.360.480.610.770.941.101.301.511.701.952.202.472.742.822.907.0912.0

1 in. (25.4 mm)

5 in. (127 mm)

3.2511.7 25.0 42.0 64.0 89.0

119.0 152.0

0.110.160.210.240.270.340.410.630.871.161.481.852.252.703.143.654.194.805.406.106.707.408.10

3/4 in. (19.05 mm)

4 in. (101.6 mm)

10.5 38.0 80.0

136.0

0.130.170.220.280.340.470.630.720.811.001.221.852.603.444.405.456.707.959.3010.8 12.4 14.2 16.0 17.9 19.8

.34

.63

.951.261.581.9

2.212.522.843.153.794.424.735.055.686.317.899.46

11.0512.6214.2015.7717.3518.9320.5

22.0823.6625.2426.8128.3929.9731.5547.3263.0978.8694.64

110.41126.18

Typical Friction Losses of Water in Pipe (Old Pipe)Nominal Pipe Diameter

Head Loss In f/ 100 ft(m per 100 m)

gal/min

gpm L/s5

1015202530354045506070758090

100125150175200225250275300325350375400425450475500750

10001250150017502000

.34

.63

.951.261.581.9

2.212.522.843.153.794.424.735.055.686.317.899.46

11.0512.6214.2015.7717.3518.9320.5

22.0823.6625.2426.8128.3929.9731.5547.3263.0978.8694.64

110.41126.18

gal/min

Figure 37. Typical Friction Losses of Water in Pipe.

35

Figure 38. Resistance of valves and fittings to flow of fluids.

36

Minimum Pump Inlet PressureIt is important for successful pump operationand obtaining the correct pump rise toprovide sufficient pump inlet pressure at allconditions of flow. Insufficient suctionpressure causes cavitation at pump outletwhich results in reduced flow to the engineand erosion of the pump parts. Whiledesigning the external cooling system, careshould be taken to ensure that the propersuction pressure is provided for the pump.The main factor that affects the suctionpressure required are the operatingtemperature and type of coolant. Therequirements of minimum inlet pressure forthe engine mounted pump with water ascoolant for various operating temperature isshown in Figure 39. This data can be used for50% ethylene or propylene glycol solutionsalso (as they are more resistant tovaporization than water).

The minimum pressure specified in Figure 39is valid for installations where the length ofstraight pipe at the pump inlet is at least 1.5m(5ft). For installations where the inlet to thepump is directly after a right angle (90°)bend, the minimum suction pressure shouldbe increased by 10%. The pump inlet pressureshould exceed the maximum pump inletpressure specified in the section on PressureLimits.

A properly designed expansion tank providesminimum pressure at the pump inlet all thetime. The suction pressure also differs withthe type of cooling system, inlet or outletcontrolled as explained in the section onExpansion Tanks.

Expansion TanksThere are two ways of providing expansionvolume to a cooling system, by separateexpansion tanks or as an integral part of the

1500

Water Pump – Minimum Inlet Pressure Required (KPa gage)

Wat

er P

ump

Inle

t Tem

pera

ture

(Deg

C)

25

45

35

115

95

75

105

85

65

55

125

Minimum Water Pump Suction (inlet) Pressure

10 40 70 100 13020 50 80 110 14030 60 90 120

Figure 39. Minimum water pump suction (inlet) pressure.

37

radiator header tank design. If the expansionis provided as part of the radiator tank, thecustomer does not need to provide anyadditional expansion tank. Many G3600engines are installed with custom coolingsystems and/or remote radiators whichrequire a separate customer suppliedexpansion tank.

The following discussion on expansion tanksis to guide users in specifying and installingthose expansion tanks.

An expansion tank must meet the followingfunctions:

• The tank must be the highest point on thesystem and must be connected with thepump in a way to maintain a positive headon the water pump

• The tank must be vented to atmosphere orincorporate a pressure cap to assuresystem pressure and prevent boiling of thecoolant

• The tank must provide de-areation and isusually the means for filling the system

• The size of the expansion tank shouldinclude the required expansion volume andthe minimum reserve capacity to providefor expansion plus reserve

The functions of the expansion tank requirethat it be located at the highest point of thesystem, otherwise the design criteria will bedifficult to accomplish. The expansion tank’sfunction is to allow for thermal expansion ofthe coolant. Coolant expansion is a function ofthe coolant temperature and type of coolant.In addition to thermal expansion, thereshould be volume for after-boil and sufficientreserve to allow operation with small leaksuntil they are fixed.

Full Flow and Remote FlowExpansion TanksThere are two types of expansion tanks, fullflow and remote flow. A full flow expansiontank performs several functions since all theflow passes through it, see Figures 1 and 2. Itprovides a blending chamber for cooled andbypass coolant from the temperature

regulator, an expansion area to de-areate thecoolant and a positive suction head at thepump inlet without a shunt line. A full flowtank eliminates the disadvantages of inletversus outlet controlled systems. Since fullflow expansion tank performs the de-areationfunction, it will require greater volume. Thistype of a tank must be well designed andconstructed to withstand the full systempressure which is exerted on the tank.

A full flow expansion tank requires carefulattention to design to prevent the tank fromcausing coolant aeration at high flow. A fullflow expansion tank might require a volumeseveral times that of a remote tank to preventaeration. Generally, a full flow tank should besized to limit the fluid change rate to anabsolute maximum of 50 times per minute atthe low level mark. Fluid change rates of 30times per minute or less and proper bafflingwill help insure that the expansion tank willnot cause coolant aeration at the low coolantmark.

A remote (or shunt) flow expansion tank issimply a tank mounted preferably at thehighest point of the cooling system, seeFigures 40 and 41. Its function is to containthe expansion volume of the coolant as itheats up, provide a positive head to the inletof the pump and provide a filling and ventinglocation from the system. In this type of anexpansion tank very little flow takes placethrough the tank itself, usually the shunt lineto vent line bypass flow.

Expansion Tanks for Inlet and OutletControlled SystemsInlet controlled systems have temperatureregulator between the heat exchanger and thesuction side of the circulating pump. If remoteexpansion tank is used, the regulator createsrestriction on the pump inlet and will result incavitation. To prevent the negative pressure(vacuum) and pump cavitation, a shunt line isconnected between the bottom of theexpansion tank and the pump inlet, seeFigure 42. The height of the expansion tankprovides static head on the pump to raise theinlet pressure and prevent cavitation. Theshunt line should be a minimum of 63.5 mm(2.5 in) in outside diameter. The diameter of

38

Turbo

Engine Jacket

Jacket WaterPump

Oil Cooler

Aftercooler

AC-OC Pump

VentLine

MixerBox

Vent Lines

ShuntLine

G3606 &G3608 G3612 &

G3616

ShuntLine

83°C (181°F)94°C (201°F)

32°C (90°F)54°C (130°F)


Remote FlowExpansion Tank





Figure 40. G3600 Cooling System with Remote Flow expansion tank - Inlet Controlled.

RawWater In

Raw WaterOut

Raw WaterIn

Raw WaterOut

Turbo

Engine Jacket

Jacket WaterPump

Oil Cooler

Aftercooler

AC-OC Pump

VentLine

MixerBox

Vent Lines

ShuntLine

G3606 &G3608 G3612 &

G3616

ShuntLine

88°C (190°F)99°C (210°F)

64°C (144°F)







Figure 41. G3600 Cooling System with Remote Flow Expansion Tank - Outlet Controlled.

39

ShuntLine

Deaeration And Vent Line

Vent If Required

EngineThermostat

Return

Outlet

Heat Exchanger

RemoteExpansionTank


EngineThermostat

Return

Outlet

Heat Exchanger

Full FlowExpansionTank


Figure 43. Inlet controlled system with full flow expansion tank.

Figure 42. Inlet controlled system with remote flow expansion tank.

40

Vent Line, If Required

Expansion Tank

Fill Line

Outlet

BypassLine

Engine DrivenJ.W. PumpReturn

Rad

iato

r

ConnectionLine

DeaerationAnd Vent Line

EngineThermostat

FillLine

Cap

Vent Line,If Required



Alternate ConnectionIn Return Line

OutletEngine Thermostat

BypassLine

Return

Fill Line

CapExpansion Tank

Vent Line, If Required


Alternate Connection LocationIn Return Line


Outlet

EngineThermostat

BypassLine

Return

Figure 44. Outlet Controlled System with vertical radiator core.

Figure 45. Outlet Controlled System with vertical cross flow radiator core.

Figure 46. Outlet Controlled System with horizontal radiator core.

the shunt line is important. The area of theshunt line must be at least four times thecombined area of the vent lines connected tothe tank. This will minimize any reduction ofthe static head because of vent and de-areation flow. For a full flow expansion tankthe tank is located in the suction line to thepump, see Figure 43, and no shunt line isneeded.

Outlet Controlled systems differ from theinlet controlled systems in the routing of theexpansion tank connection. In this system theexpansion tank connection is called fill line.The fill line size should also be a minimum of63.5 mm (2.5 in). Since there is notemperature regulator located between theheat transfer equipment (radiator) outlet tankand the suction of the pump, the fill line doesnot need to be plumbed back to the inlet ofthe pump. The relative sizes of the return lineof radiator provides minimum pressure loss.This means the expansion tank may beconnected to either the outlet tank oranywhere in the return line to the pump, seeFigures 44, 45 and 46. Do not connect the fill

line to the inlet tank. There will not besufficient head for the de-areation circuit tofunction properly. There will also not besufficient head on the pump suction and thepump head may force coolant to overflow thepressure cap.

Sizing Expansion TanksThe required expansion volume for the jacketwater circuit can be calculated based on theoperating temperature and type of coolant.The expansion rate for the different type ofrecommended coolants are shown inFigure 47. The maximum expansion volumefor the jacket water on standard coolingsystems is 15%. For higher temperaturesystems (higher than 100°C or 212°F) willneed a larger volume to adsorb after-boil thatmay occur on hot shutdown, see section onHigh Temperature Solid Water Systems in theHeat Recovery chapter for more information.

A separate expansion tank is required for theaftercooler-oil cooler cooling system toeliminate the possibility of coolant exchangebetween the high temperature jacket water

41

1300

Temperature °C

Cool

ant E

xpan

sion

%

0

2

1

9

7

5

8

6

4

3

10

10 40 70 90 11020 50 80 100 12030 60

Figure 47. Expansion rate of coolant

100% Propylene Glycol

50% Propylene Glycol

100% Ethylene Glycol

50% Ethylene Glycol

Pure Water

Figure 47. Expansion rate of coolant.

system and this circuit. The maximumexpansion required for this circuit is 8%. Thisis due to the lower coolant temperatures andsystem volume of the aftercooler-oil coolercircuit.

The system volume for jacket water andstandard aftercooler-oil cooler systems isgiven in the section System Volume. Theminimum reserve capacity is determinedfrom the following table:

Therefore the minimum acceptable expansiontank volume is:

Minimum Tank volume 5 (Expansion Rate 3System Volume) 1 Minimum Reserve Capacity 5

Expansion vol. 1 Minimum Reserve CapacitySystem PressuresDepending on the altitudes and ambient ofthe engine site, pressurizing the system willhelp to prevent the coolant from boiling underoccasional adverse conditions. Slight systempressures minimizes pump cavitation even athigh altitudes and increases pump efficiency.For each 6.9 kPa (1 psi) of increase in systempressure, the boiling point of pure water israised about 2°C (3.5°F). Elevations above3048 m (10,000 ft) require higher ratedpressure caps to avoid boiling. Ethylene andpropylene glycol solutions raise the boilingpoint. However alcohol or other volatileantifreezes lower the boiling point. Figure 48shows the effects of system pressure onboiling point of water at various altitudes.

Caterpillar supplied expansion tanks have asuitable pressure cap to maintain correctsystem pressures for normal applications asdiscussed in the section AttachmentExpansion Tank. When a factory expansiontank is not used, the following three methodscan be used to ensure the right systempressure.

1. Use a pressure cap on the auxiliaryexpansion tank.

2. Providing the pressure with a water columnby locating the auxiliary expansion tank(without pressure cap) at an elevationabove the pump.

3. A combination of an elevated auxiliaryexpansion tank with a pressure cap 1 m of water = 9.8 kPa (1 ft = 0.43 psi)

Static head is the maximum height thecoolant is raised. Large static heads areencountered when radiators are located onthe roof. Excessive static head can causeengine mounted pump seal leakage.

Dynamic head is the sum of the staticpressure head plus the pump rise at operatingcondition. Excessive dynamic head can causeleakage at gasket joints downstream of thecoolant pumps. The combination of static anddynamic head must meet the pressure criteriaspecified in the Pressure Limits sections.Components in the external cooling system,particularly radiators, must meet operatingpressure levels. When static and dynamicpressure exceed acceptable limits, isolate the

Figure 48. Boiling point change with change in coolingsystem pressure.

Altitude

Sea Level°Fahrenheit°Celsius

18082

00.0

20.1

40.3

60.4

80.6

100.7

120.8

141.0

PSIkg/cm2

19088

20093

21099

220104

230110

240115

250121

Feet Meters430037003000240018001200600

0

1400012000100008000600040002000

Cooling System Pressure

Boiling Point of Water

Min. Reserve Capacity(% of Total System Vol.)

Total External Circuit Vol.(% of Engine Coolant Vol.)

10≤ 50

960

870

780

690

5≤ 100

42

engine side by providing a heat exchanger orhot well.

Attachment Expansion TankAn attachment expansion tank, designed withthe functions discussed above, is available asa full flow expansion tank for the jacket watercircuit for the G3600 engines.

The Caterpillar expansion tank provides thefollowing features.

Expansion Volume for coolantCoolant Level AlarmPressure Cap & VentCoolant Sight gaugeDe-areation ChamberTemperature Regulator Mounting location

The following recommendations andguidelines should be followed when using thistank,

• The maximum pressure capability of thisexpansion tank is 150 kPa (22 psi). Thismaximum pressure limitation wouldpreclude the expansion tank from manyhigh temperature applications. Thestandard pressure cap on this expansiontank is rated for 49 kPa (7 psi). Higherpressure rated caps have to be speciallyrequested from the factory for coolanttemperatures higher than 99°C (210°F).

• The expansion tank must be the highestpoint in the cooling system. If theattachment expansion tank is not thehighest point of the system, an auxiliaryexpansion tank will be required. Theadditional added static head provided bythe auxiliary tank may raise the systempressure above the limit for the attachmentexpansion tank. The auxiliary expansiontank is added cost and may make theattachment expansion tank redundant.Those installations may be better designedwith a shunt flow expansion tank instead.

• Attachment expansion tanks have sufficientvolume for a specific total system volumefor the standard cooling configuration listedin the TMI. This expansion tank should notbe used on larger systems than it isdesigned for. Application on larger systems

will result in coolant loss during operationfrom the overflow and a low coolantshutdown on a subsequent restart attempt.

Filling and VentingG3600 Engines can be filled either throughthe filler cap on the expansion tank or bypumping coolant from the bottom, throughthe ports on the pump or cylinder block. Thefiller cap is usually located on the expansiontank. The line connecting the expansion tankwith the pump suction should be sized toaccept the maximum fill rate of the system.The maximum guidelines for filling rate,through the filler cap, is 19 L/min (5 Gal/min). Bottom fill by pumping shouldnot exceed a rate of 112 lpm (30 GPM). Airtrapped in the high point of the coolingsystem during the initial fill is difficult topurge and requires venting. A cooling systemthat will not purge itself on initial fill musthave vent lines from the highest points of thesystem to the expansion tank. Some highpoints that must be vented on the G3600engine are turbocharger housing, mixer box(both jacket water and aftercooler-oil coolersides) on G3612 and G3616 and oil cooler onG3606 and G3608. Vent lines must travel at acontinuous upward slope from the engine andenter the expansion tank below normal waterlevel and contain no air traps. An adequatevent line would be 9.5 mm (0.375 in) to 12.7mm (0.5 in) outside diameter tubing. Ventlines must be provided by the customer for allinstallations. Refer to the installation drawingsof the specific engine for venting locations.

The preferred system is to have all highpoints vented to the expansion tank. Thereare some installations where that is notpossible, especially when modifying existinginstallations. Mechanical vent valves can beadded to high points to vent air and gases,that accumulate at high points, after every fill.Vent valves require servicing. Occasionallythey leak coolant or allow air to enter thesystem during shutdown. In some areas,coolant may be considered a hazardous liquidand coolant leaks should be avoided. In thoselocations an active venting system ispreferred over mechanical vent valves.

43

44

Caution: The constant fill level in theexpansion tank must be above all piping. Venthigh points of the engine to the expansiontank to allow specified fill rate and preventfalse fill.

De-aerationAir can be trapped in the cooling system atinitial fill or enter through combustionleakage during engine operation. This air andgas must be vented from the system, orsystem deterioration and pump cavitation willoccur.

Since there is a possibility of entrainedcombustion gases in the cooling system, de-areation capabilities are required to be builtinto the system. De-aeration may be with acentrifugal de-aeration gas separator with thegases vented back to the expansion tank, seeFigure 49. If a centrifugal de-aeration gasseparator is not used separation of gas fromthe liquid medium requires a low coolantvelocity of 94 mm/sec (2 fps) with a divertedflow to the expansion tank, where the

relatively static velocity in the tank allows thegases to be separated. The de-aeration flow isregulated by a 10 mm (3/8 in) diameterorifice placed in the line. Therefore, in theareas where de-aeration must take place holdthe coolant velocity below this limit byincreasing the diameter of the pipe, seeFigure 50. The de-aeration line is typicallyconnected to the radiator inlet tank, mostradiator tanks have sufficient cross-sectionalarea to meet this velocity requirement, seeFigure 50. Full flow expansion tanks must bedesigned with sufficient cross-sectional areato slow the velocity of the water. They musthave the internal baffles designed to separatethe gases from the coolant. Closedaccumulator type expansion tanks are notrecommended since they cannot be designedto actively de-aerate the coolant.

Figure 49. De-aeration Chamber (modified).

RadiatorsRadiator Cooling is the most common type ofcooling systems. Radiator cooling provides aclosed, self-contained system that is bothsimple and practical for most installations.

Figure 51 shows a diagram of a typicalradiator design. Hot engine water flows to theinlet tank and then through the radiator corewhere it is cooled by air being pushed (orpulled) through the core by a fan. Cooledwater is then pumped back to the engine.Circulation is then maintained by a geardriven, engine mounted water pump. Thecooling system is designed to operate under apressure of 27–48 kPa (4–7 psi).

Remote Mounted RadiatorsRemote Systems impose added restriction oncooling water flow by additional piping andfittings. An auxiliary pump in series with theengine mounted pump should not be used toovercome this restriction. When longdistances separate the engine from theradiator, oversized piping may be required tominimize piping restriction.

Never locate remote mounted radiators morethan 17.4 m (57 ft) above the pump. At greaterheights the static head developed may causeleakage at the engine water pump seal.

The radiator inlet tank loses its ventingcapability if it is located below the level of theengine regulator housing. When a radiatormust be mounted lower than the engine anexpansion tank must be used, see Figure 52.

If an engine mounted expansion tank is used,the radiator must be selected with the inletcontrolled guidelines and the core mustwithstand full pump pressure. This willusually require a round tube radiator. If thecore is vertical reverse water flow through theradiator. This ensures gas or air is not trappedin the radiator inlet tank. Radiator designoperating pressure must be increased by6.9 kPa (1 psi) for every 610 mm (2 ft) theengine is above the radiator. Do not useradiator pressure caps. It should be removedand the opening sealed. The expansion tankpressure cap can be used to relieve excesspressure and fill the system.

Radiator Design CriteriaConsider the following factors whendesigning and installing a radiator coolingsystem. Size the radiator to accommodate aheat rejection rate approximately 10% greaterthan the engine’s maximum (nominal +tolerance) heat rejection. The additional 10%will compensate for possible variations fromthe published or calculated heat rejectionrates, overload and system deterioration.Even if the expected load is less than theengine rated power, size the radiator to matchengine rated power.

Correction factors to the observed ambientair temperature capability for the machinemust not be overlooked. Altitude above sealevel reduces the density of air and its abilityto cool the radiator. A good correction factoris 1.38°C (2.5°F) deducted from the observedambient temperature capability for each305 m (1000 ft) above sea level.

It must be kept in mind that the ambient airtemperature may not be the same as the airtemperature flowing across the radiator core.An engine equipped with an engine mountedradiator and blower fan will increase the airtemperature as it flows across the engine tothe radiator. The decrease in the ambientcapability of a radiator can be found from thefollowing table.

Figure 50. Pipe Diameter for De-aeration.

Water VelocityLess Than

0.6 m/s (2 ft/sec)

To SystemExpansion Tank



45

46

Fill Line

Cap

Vent And De-aeration Line

SealedRadiatorCap

ExpansionTank

Engine

Pump

Figure 52. Radiator Cooling System with expansion tank.

Outlet

BypassLine


ReturnA

B

C

Rad

iato

r

EngineThermostat

Piping

Part of engineSupplied by packageror radiator supplier

B – A: Cold FlowC – A: Full External Flow

Figure 51. Radiator Cooling System.

Another correction which must be included isthe effect of antifreeze. The ability to transferheat diminishes with the addition of anyantifreeze, ethylene glycol or propyleneglycol. Antifreeze decreases heat transfercapability of a radiator by approximately 2%for every 10% of antifreeze. If antifreeze isused year-round, this must be considered.Year-round use of antifreeze decreasesradiator capabilities by at least 3.3°C (6°F).

When selecting radiator location, consider fannoise. Noise transmits through the air inlet aswell as outlet. Soft flexible joints betweenradiator and duct will prevent vibration andnoise transmission.

Position the radiator so prevailing winds donot act against the fan. One form of windprotection for the radiator is a baffle setseveral feet away from the radiator exhaust.Another method is to install an air ductoutside the wall. Direct the air outlet (or inlet)vertically. Large radius bends and turningvanes prevent turbulence and air flowrestriction. For remote- mounted radiators,the radiator can be mounted horizontally sothe prevailing winds do not effect fan flows asshown in Figure 53.

Care must be taken to prevent the hotradiator discharge from recirculating to itsinlet or the inlet of another radiator, seeFigures 54a and b. Radiators must bearranged so that the engine exhaust gasesand crankcase ventilation gases are not drawninto the air inlet of the radiator, seeFigure 54c.

Engine only, outside or in a large engine room

3°C (5.4°F) None

BlowerFan

SuctionFan

Estimated Air to Core Rise

Engine/generator outside or in a large engine room

4°C (7.2°F)

Engine/generator in enclosurewith external muffler

7°C (12.6°F)

Engine/generator in enclosurewith internal muffler

9°C (16.2°F)

NotRecommendedwith generator

NotRecommendedwith generator

47

Figure 53. Remote mounted radiator cooling system.

Heat ExchangersA heat exchanger is sometimes preferred tocool the engine when ventilation air is limitedor when excessive static head on the enginemust be avoided.

The most common type of heat exchanger isthe shell and tube type. Inside the heatexchanger, the engine coolant is cooled bythe transfer of heat to some other liquid at alower temperature. Heat exchangers aresingle or multi pass type depending on theflow in the raw water circuit of the exchanger,see Figure 55. In the multi pass exchanger,water flows twice or more through theexchanger, single pass type flows raw wateronce. Raw water in the single pass type flowin the opposite direction to the coolant flow toprovide maximum differential temperatureand heat transfer. In multi pass exchanger,relative direction of flow is not significant.

Heat Exchanger Design CriteriaSome heat exchangers suitable for G3600engines are listed in the price list. Considerthe following factors when designing andinstalling a heat exchanger cooling system.

Size the heat exchanger to accommodate aheat rejection rate approximately 10% greaterthan the maximum (nominal + tolerance) heatrejection of the engine or component. Theadditional 10% will compensate for possiblevariations from the published or calculatedheat rejection rates and engine overload.Different cooling mediums have varyingcooling capacities and tendencies to foul or

Figure 55. Heat Exchanger Types.

48

Radiator Recirculation

IncorrectIncorrect

Correct

CBA

Figure 54. Radiator Recirculation.

reduce the heat transfer and are representedby the fouling factor. Fouling factor affects theheat transfer of a heat exchanger by thefollowing formula:

FF = 1 2 1 Ucoolant Uclean core

where:

FF = Fouling factor, m2.°C/kW (h ft2.°F/Btu)

Ucoolant = Heat transfer coefficient of core withcoolant, kW/m2.°C (Btu/h ft2.°F)

Uclean core = Heat transfer coefficient of theclean core, kW/m2. °C (Btu/h ft2.°F)

Factors for commonly used water types isgiven in this table,

For the coolants listed above fouling factorsgreater than 0.001 will result in significantchange in the heat transfer capacity. Use thefollowing table to correct the heat capacity ofthe heat exchanger given in TMI for foulingfactor different than the base of 0.001. Forcoolants with fouling factors less than 0.001the values have been left unchanged.Caterpillar does not recommend designing fora fouling factor less than 0.001.

Since heat exchanger tubes can be cleanedmore easily than the surrounding shell(jacket), the raw water should be passedthrough the tubes and the engine coolingwater through the shell or jacket.

If solenoid valves are used to control coolingwater, position them upstream of the heatexchanger. The drain for the heat exchangeris always open and the heat exchanger isrelieved of pressure when inoperative. Ifsolenoid valves are installed on both sides,raw water could be trapped in the tubes if thesolenoids fail to open. Water trapped duringengine operation expands and could rupturethe exchanger. All solenoid valves shouldinclude manual bypass.

Do not add temperature regulators in rawwater supplies. Engine jacket water iscontrolled by a temperature regulator,additional controls add expense, restrictionand decrease reliability.

Submerged Pipe CoolingThis method is simplest to use if the engine isstationary and is used to pump water, or isnear a supply of relatively cool water,preferably 29°C (85°F) or less. In this system,the engine coolant water is pumped throughcoils or lengths of pipe submerged in thecooler water. These coils can be placed in aconcrete catch basin or tank placed in adrainage ditch. Care must be taken to protectthe coils from damage and to insure they donot become buried in the mud or silt.Figure 56 shows a typical submerged pipecooling system.

Raw Water Velocity

Engine Coolant Temperature ≤116°C (240°F)Raw Water Temperature ≤52°C (125°C)

≤ 0.9 m/s(3 ft/s)

> 0.9 m/s(3 ft/s)

City or Well Water(such as Great Lakes)

1.0 1.0

River Water 0.71 0.71

Hard (over 15 grains/gal) 0.71 0.56

Engine Jacket 1.0 1.0

Treated Boiler Feedwater 1.0 1.0

1.00.71

1.00.56

Fouling Factors Chart Correction Factors

Sea Water 1.0 1.0

Brackish Water 0.83 1.0

Cooling Tower and ArtificialSpray Pond: Treated Makeup

Untreated

Raw Water Velocity

Engine Coolant Temperature ≤116°C (240°F)Raw Water Temperature ≤52°C (125°C)

≤ 0.9 m/s(3 ft/s)

> 0.9 m/s(3 ft/s)

City or Well Water(such as Great Lakes)

0.001 0.001

River Water 0.003 0.002

Hard (over 15 grains/gal) 0.003 0.003

Engine Jacket 0.001 0.001

Treated Boiler Feedwater 0.001 0.0005

0.0010.003

0.0010.003

Fouling Factor Chart for Water

Sea Water 0.0005 0.0005

Brackish Water 0.002 0.001

Cooling Tower and ArtificialSpray Pond: Treated Makeup

Untreated

49

Submerged Pipe Design CriteriaEngine heat rejection and the temperatures ofthe cooling medium must be carefullyconsidered in determining the correct sizeand length of pipe to use. As a rule of thumb0.003 m2 (0.0353 ft2) of submerged pipesurface area is required for every kW(56.87 Btu/min) of engine heat rejection thatmust be removed. This rule of thumb is forraw water temperatures up to 29°C (85°F).

A trial and error method can be used if jacketwater temperature is too high or low. Byadding or removing pipe as necessary, theengine cooling water temperature can bemaximized. Pipe must be kept out of mud andoff the bottom of the tank to insure maximumcooling efficiency. Connect the system so thatthe engine water flows from the engine to thecooling coils and to the expansion tank beforereturning to the water pump inlet.

Cooling TowersSince radiators are often ineffective forcooling AC-OC water below 54°C (130°F), analternate source of water is needed for lowtemperature cooling circuits like 32°C (90°F).In such cases cooling towers are used when alarge supply of cool water (i.e. a river, lake,cooling pond, etc.) is not available or notusable for environmental reasons.

Though there are several types of coolingtowers, the basic method of heat transfer isthe same. As seen in Figure 57, air is brought

in direct contact with the cooling water.Cooling is accomplished in two ways,approximately 75% occurs by waterevaporation and about 25% by direct heattransfer from the water spray to the passingair. Since the primary mechanism for coolingthe water is through evaporation, the ability ofthe air to absorb moisture is critical to theeffectiveness of a cooling tower. It is for thisthat the performance of a cooling towerdepends on the relative humidity of theambient air.

Relative humidity is the measure of the air’sability to absorb moisture. When the relativehumidity is 100%, the wet-bulb and thedry-bulb temperatures are equal and the aircannot absorb any more moisture. Thereforethere will be no evaporation and little cooling.However, when the relative humidity is lessthan 100%, the wet-bulb temperature is lessthan the dry-bulb temperature and the air canabsorb moisture by evaporation. The use ofcooling towers are most practical in areaswith an ambient dry-bulb temperature above37.8°C (100°F) and when the relativehumidity averages 50% or less.

The prevailing wet-bulb temperature is a keyfactor in the design of a cooling tower. It isthe theoretical limit to which a cooling towerwill cool. However, in practical application of acooling tower, the coolant temperature canonly be maintained down to about 5.6°C(10°F) above the wet-bulb temperature.

50

Flexible Connectors

Galvanized Pipe


Support Pipe In WaterTo Allow Circulation Of Water Around Pipe

Drain Plug

Figure 56. Submerged Pipe Cooling.

In open cooling systems using cooling towers,the engine cooling water is sprayed directlyinto the tower and is subjected to the inherentconcentrations of water contaminants of thissystem. Unless special provisions are made,such as cleanable aftercooler and corrosionresistant plumbing, the use of an open coolingsystem is NOT recommended for G3600engines.

Figure 57 demonstrates how a heatexchanger can be used to maintain a closedcooling system for the engine while using acooling tower. In this system raw water iscirculated by an auxiliary water pump drivenby the engine or by an electric motor. Thepump flows cool water from a basin at thebottom to the cooling tower, forces it throughthe heat exchanger and to the distributionsystem at the top of the tower. As the heatedwater passes through the tower it cools andcollects in the basin.

Types of Cooling TowersCooling towers are generally two types, theopen type described above and the closedloop type or evaporative cooler. For the closedloop cooling tower the engine coolant can be

circulated to the cooler eliminating the heatexchanger at the engine, see Figure 58. Thecoolant in the closed loop can be treated toprevent corrosion eliminating therequirement for corrosion resistant piping.

Cooling Tower Design CriteriaAs a general rule, cooling towers are mosteffective in areas with an ambient dry-bulbtemperature above 37.8°C (100°F) and whenthe relative humidity averages 50% or less.

Cooling towers are very sensitive to approachtemperatures (i.e. the difference between thewet-bulb temperature and the desired coolanttemperature). For an approach temperature of8.3°C (15°F), all other factors held constant,tower size increases by 50% if approachtemperature of 5.6°C (10°F) is required. Anyapproach temperature below 2.8°C (5°F)becomes unrealistic.

As with radiators, cooling towers are verysensitive to recirculation and the presence ofother upwind cooling towers, see Figure 59.Any recirculation ingestion of exhaust airfrom another cooling tower effectivelyreduces the approach temperature and the

51

Heat Exchanger


Water Spray

Air Flow

Fan

CirculatingPump

Water Sump

Figure 57. Cooling Towers with External Mounted Heat Exchangers.

wet-bulb temperature of the incoming air. Aswas demonstrated earlier, the approachtemperature has a significant effect on thecooling tower, size. Therefore, factors such aslocation of the towers, direction of theprevailing winds and the height of the towers(a taller tower will reduce recirculation)should be taken into consideration.

The continued process of evaporation meansthat any scale forming salts present in thewater will gradually be concentrated and thewater may also pick up contaminants from the

air. These impurities can result in the build upof scale on the cooling water passages,decreasing the cooling system efficiency. Asthese salts and minerals collect, they must bedrained and the tower diluted with freshwater. Solids such as dust may alsoaccumulate in the tower water and can bereduced by a filter or centrifugal separators.

If the tower water is used in engine circuitssuch as aftercooler, tower water should betreated with corrosion inhibitors to becompatible with engine piping andcomponents. Even with treated water acleanable aftercooler core is required whenused with cooling tower water. Cooling towersinstalled in frigid locations require additionaldesign requirements to prevent freezing.

Aftercooler Heat ExchangerSizingThe aftercooler heat rejection data given inTMI and Technical Manual is for standardconditions of 25°C (77°F) and 150 m (500 ft)altitude. This data meets all standardconditions for SAE J1349, ISO 3046,DIN 6271, BS 5514 and API 7B–11C.

Ambient temperature higher than standardwill raise the amount of heat in the inlet air tobe rejected to the aftercooler circuit. Altitudes

Figure 59. Tower recirculation due to wind.

Wind

Tower Recirculation due to wind

52

Outlet

Fill Line


CirculatingPump

BypassLine

Return

EngineThermostat

Deareration Line

Expansion Tank

Air Flow

Fan

Water Sump

Water Spray

Figure 58. Closed Loop Cooling Tower.

higher than standard will require a highercompression ratio across the turbocharger(i.e. the turbocharger works harder) to obtainthe rated absolute pressure in the intakemanifold. Higher pressure ratios result inmore heat of compression and more heatrejected to the aftercooler circuit.

For ambients and altitudes above the standardconditions, the aftercooler heat exchangermust be enlarged to dissipate the additionalheat described in the above paragraph. Toproperly size the aftercooler for a specificambient and altitude, it is necessary tomultiply the heat rejection at standardconditions by a multiplier. These multipliers(between 1.0 and 3.0) are for a combination ofthe ambient and altitude and are found in theAftercooler Heat Rejection Factors charts inthe Technical Manual or Specification Sheets.Heat rejection data and the multipliers as wellas the air flow and compressor outlet pressurecan be found in TMI or the Technical Manualfor G3600 engines.

Since the altitude and ambient temperatureaeration curves are designed to be used witha known water temperature, some effort mustbe put into converting the inlet airtemperature of the aftercooler to a watercircuit temperature. Failure to compensate forthe actual air inlet temperature can causedetonation and result in engine shut downand possible damage.

To obtain the turbocharger compressor outlet(inlet air to aftercooler) temperature for otherthan standard conditions, use the formula:

Tc = Fac 3 [Tcstd 2 Tman] 1 Tman

Tc = Actual Compressor Outlet airtemperature

Fac = Aftercooler Heat Rejection FactorTcstd = Compressor Outlet Air Temperature

at standard conditionsTman = Inlet manifold air temperature

Interconnection of EnginesCentral cooling systems utilize a singleexternal circuit supplying coolant to severalengines. Although separate cooling systemsfor each engine is preferable, use of single

radiator or heat exchanger is theoreticallypossible. Practice has shown that onlyidentical engines at the same loads andspeeds can be successfully combined in ajoint cooling system. A failure on one enginecan adversely affect all engines. For thisreason, interconnected engines should haveisolating valves. Check valves are required onthe outlet line of each engine to preventrecirculation through an engine that is shutdown with the temperature regulators open.

The cooling systems for mixed engines withmixed speeds and loads are very difficult todesign and are rarely successful. They mustmeet the required criteria (water flows,temperatures, pressure, etc.) for each enginewhile operating in all possible combinationswith other units. Central cooling systems arenot recommended for G3600 engines. If acentral system is desired, each engine can becooled by an individual heat exchanger and allthe heat exchangers can be cooled by acentral system.

Flexible ConnectionsUse flexible connections for all connections tothe engine (rubber hoses are notrecommended). The positions of flexibleconnections are important. Shut off valvesshould be located to allow replacement offlexible connections without draining theentire cooling systems. Orient the flexibleconnection to take the maximum advantage ofthe flexibility. When selecting connectionsconsider normal thermal expansion andmaximum expected movement.

The flexible connection should be rated forconditions well above the anticipatedmaximum operating temperature andpressure of the cooling system. Clamp typeflexible connections are not recommended forthe high temperature circuits on G3600Engines. Bolted flange type connectionsshould be used for all jacket water circuitsand any other circuit running more than 65°C(149°F). Material compatibility must also beevaluated. The internal surface must becompatible with the coolant used and the linermaterial must be compatible with potentialcoolant contaminants, such as lube oil and

53

system cleaning solutions. The outer covermust be compatible with its environment(temperature extremes, ozone, grease, oil,paint, etc.). Factory provided flexibleconnections are available for most pipe sizes,refer to the Price List for available options.

Piping SupportsAll piping to and from the engine must besuitably supported by means of brackets andclamps. Piping must not overhang excessivelyfrom the pump inlet, mixer box outlet,temperature regulators and expansion tanks.The weight of the piping combined with thewater in the pipes can load the enginecomponents considerably, especially when theengine is vibrating during operation. Pipingshould be supported adequately oninstallations where the radiators or heatexchangers are roof-mounted or the piping isrouted through the roof.

Jacket Water HeatersJacket water heaters are recommended forfaster, easier starting in ambient airtemperatures below 21°C (70°F). Allautomatic starting installations should includethese heaters. The correct size heaters foreach engine at minimum ambient roomtemperature to maintain engine jacket waterat approximately 32°C (90°F) is shown in thetable below.

Heater sizing is based on wind velocity of0 kmph (0 mph) around the engine. When a24 kmph (15 mph) wind is present the heaterrequirement doubles. Factory provided jacketwater heaters are available for the abovespecifications.

Time required for temperature to stabilize is10 hours. Wattage requirements for shorterperiods are inversely proportional to the 10hour requirement. Physical location and

exposure to the elements can affect sizing.Contact Caterpillar for special voltages, threephase current and special heaters for ambienttemperatures lower than listed. For customerinstalled systems, the following guidelinesshould be considered.

• Mount the heater as low as possible, seeFigure 60.

• The cold water inlet to the heater should befrom the lowest possible point in the enginecooling system.

• Avoid cold water loops, any situation wherecold water must rise to enter the heater,see Figure 60, location A.

• Join the hot water side of the heater nearthe top of the engine cooling system, butbelow the temperature regulators.

• Use the same pipe size (or larger) as theheater connections.

Caution: Do not create hot water loops. Hotwater line should enter the engine in either ahorizontal or slightly inclined plane,eliminating the possibility of forming a steampocket, see Figure 60.

Cleanliness and StrainersAll pipe and water passages, external to theengine, must be cleaned before initial engineoperation. There must be flow and any foreignmaterial must be removed. The radiators andheat exchangers must also be clean.

The cooling system should be filled with rustinhibitors and strainers should be installedbefore a package test or installation atcustomer site. Rust inhibitors can be in theform of ethylene or propylene glycol ifoperating temperatures are expected to gobelow freezing, or in the form of coolantconditioner. The coolant conditioners or rustinhibitors should be compatible with theantifreeze used in the engine, refer to thesection Water Quality and Treatment in theHeat Recovery chapter or Caterpillarpublication Coolant and Your Engine(SEBD0970) for more information.

Jacket Water Heater Sizes kW (Btu/min)[Conditions are no winds and 10 hours for warm up,

power to heat from -18°C (0°F) to 32°C (90°F)]

18.0 (1024)G3606

18.0 (1024)G3608

30.0 (1706)G3612

30.0 (1706)G3616

54

Strainers are available from Caterpillar to beinstalled in all pipes leading to equipmentadded externally during installation. They areavailable for 100 mm, 127 mm and 152 mm(4 in, 5 in, and 6 in) pipe sizes and all have1.6 mm (1/16 in) mesh size. On closedsystems, these strainers should be removedafter commissioning the unit. On opensystems like the Combined Heat and Powersystems where the raw water is directlycooling aftercoolers and oil coolers,permanent strainers should be installed in thecustomer piping to prevent large particlesfrom entering the engine components. Similarprecautions must be taken when significantmodifications are made to the externalcooling circuit.

If an engine is expected to be stored for longperiods without operating or beforecommissioning, special treatment in the formof Vapor Corrosion Inhibitor (VCI) is requiredfor the cooling system to prevent rustformation. Please refer to the other Caterpillarcooling systems publications listed at the endof the Heat Recovery chapter for moreinformation on coolant additives for engineprotection. There are long-term preservationtreatment for cooling systems provided by thefactory, please refer to the Price List for moreinformation.

Serviceability and IsolationValvesAccess to the heat exchangers is required forcleaning or removal of the tube-bundleassembly. Engine water pumps must be easyto remove. Remote water temperatureregulators should be accessible and haveappropriate isolation valves to allow servicingof engine and temperature regulators withoutdraining the entire system. Apply similarguidelines to radiators, heat recovery units,de-areation units, jacket water heaters andother components requiring service orreplacement.

System MonitoringProvide locations to measure pressure andtemperature differentials across major systemcomponents. This allows accurate set-up andperformance documentation of the coolingsystem during the commissioning procedure.Future system problems or componentdeterioration (such as fouling) are easier toidentify if basic data is available. It alsoprovides information for relating fieldconditions to original factory tests.

Temperature and pressure measurementlocations should give accurate reading of fluidstream conditions. Preferred locations are instraight lengths of piping reasonably close toeach system component. Avoid pressuremeasurements in bends, piping transition

55

Upper Water

Level of Engine

Regulator

B

A

Lower Water

Level of Engine

Recommended

Not recommended

Figure 60. Pipe routing with jacket water heater.

pieces or turbulent regions. Plan to installmonitoring ports during the design andconstruction of the cooling system. If theports are installed later, ensure the pipes arecleaned of drill chips and weld slag after thepressure ports are installed. Install sampleports and fittings before the cooling system isfilled. The preferred sizes for the ports on thecustomer side are 3.17 mm (1/8 in) or6.35 mm (1/4 in) NPT and 14.3 mm (9/16 in)O-ring ports. These port adapters areavailable as standard Caterpillar parts, refer tothe G3600 Price List for part numbers. Therecommended locations for measurementsand available measurement ports are shownin Figure 61.

Self-sealing probe adapters are available inseveral sizes of male pipe threads and straightthreads for g-ring ports. The adapters use arubber seal allowing temperature andpressure to be measured without leakage.Probe diameters up to 3.2 mm (0.125 in) maybe used. The straight threaded adapters areused on the engines with available ports. Pipethreaded adapters are more easilyincorporated in the customer supplied system.The adapters are an excellent alternative topermanently installed thermometers,thermocouples or pressure gauges. They arenot subject to breakage, fatigue failures andgauge to gauge reading variations.

Customer ConnectionsThe customer connection points for allconfigurations explained in the Basic SystemConfigurations Section are given in Figures62–65.

56

57

Engine Jacket

Jacket WaterPump

Mixer Box P3, T3 P4*, T4*

P5*, T5*P1*, T1*P2

P8, T8 P9*, T9*

P10*, T10*P6*, T6*P7

AB

C

AB

C

TemperatureRegulatorFull Flow

Expansion TankJacket Water

Heat Exchanger


Oil Cooler

Aftercooler

AC-OC Pump

JW: Internal Restriction = P2 – P3

AC–OC: Internal Restriction = P7 – P8

* Recommended Customer Provided Ports

External Restriction = P3 – P1

External Restriction = P8 – P6

MixerBox



Figure 61. Port locations for system monitoring.

JW Pump Inlet P1, T1* AC–OC Pump Inlet P6, T6*

JW Pump Outlet P2 AC–OC Pump Outlet P7

JW Engine Outlet P3, T3 AC–OC Engine Outlet P8, T8

JW Heat Exchange Inlet P4, T4* AC–OC Heat Ex. Inlet P9, T9*

JW Heat Exchange Outlet P5, T5* AC–OC Heat Ex. Outlet P6, T6*

58

JW TemperatureRegulator

Jacket WaterExpansion Tank

JW Heat Exchanger(Customer Provided)

JW Pump

Weld FlangesProvided or Available

Factory PlumbingProvided or Available

Customer Plumbing

Engine Block

C

C

D

A E

G

G

F

G

B

Oil Cooler Aftercooler

Mixer Box/Manifold

AC-OCExpansion Tank

(Customer Provided)

AC-OCHeat Exchanger

(Customer Provided)

AC-OCTemperatureRegulator

AC-OCPump

Flange Type

Flange Dimensions

Inner Dia.mm (in.)

Outer Dia.mm (in.)

Numberof Bolts

Bolt CircleDia.

mm (in.)

Bolt HoleDia.

mm (in.)Thicknessmm (in.)

G3606

A B C D E F G

CAT 6.5" CAT 5.5" CAT 5.5" CAT 6.5" CAT 6.5" CAT 4.5" CAT 5.5"

G3608 CAT 6.5" CAT 5.5" CAT 5.5" CAT 6.5" CAT 6.5" CAT 4.5" CAT 5.5"

G3612 CAT 6.5" CAT 5.5" CAT 5.5" CAT 6.5" CAT 6.5" CAT 5.5" CAT 5.5"

G3616

CAT 4.5" 116 (4.57) 168 (6.61) 8 146 (5.75) 10.5 (0.41) 23 (0.91)

CAT 5.5" 143 (5.63) 194 (7.64) 8 174.6 (6.87) 10.5 (0.41) 23 (0.91)

CAT 6.5" 171 (6.73) 225 (8.86) 8 200 (7.87) 10.5 (0.41) 23 (0.91)

CAT 6.5" CAT 5.5" CAT 5.5" CAT 6.5" CAT 6.5" CAT 5.5" CAT 5.5"

JW PumpInlet

JW Eng.Outlet

JW Reg.Conn.

Exp Tankto Eng.

AC-OCInlet

AC-OCOutlet

AC-OCReg Conn.

Figure 62. Customer connections - Standard Cooling System.

59

JW TemperatureRegulator

Jacket WaterExpansion Tank

JW Heat Exchanger

JW Pump


Customer Plumbing

Engine Block

D

A

B

C

D

EE

Aftercooler

Oil Cooler

Mixer Box/Manifold

Flange Type

Flange Dimensions

Inner Dia.mm (in.)

Outer Dia.mm (in.)

Numberof Bolts

Bolt CircleDia.

mm (in.)

Bolt HoleDia.


G3612

A B C D E

DIN 3.5" DIN 4" DIN 4" DIN 5" DIN 4"

G3616 DIN 3.5" DIN 4" DIN 4" DIN 5" DIN 4"

DIN 3.5" 88.9 (3.5) 220 (8.66) 8 180 (7.09) 17 (0.67) 23 (0.91)

DIN 4" 116.1 (4.57) 220 (8.66) 8 180 (7.09) 17 (0.67) 23 (0.91)

DIN 5" 127.0 (5.0) 220 (8.66) 8 180 (7.09) 17 (0.67) 23 (0.91)

ACInlet

ACOutlet

OCInlet

OCOutlet

Heat Ex.In & Out

Figure 63. Customer connections - Combined Heat and Power Cooling System.

60

JW Radiator(Customer Provided)

AC-OC Radiator(Customer Provided)

JW Pump


Customer Plumbing

Engine Block

D

C

B

A

Mixer Box/Manifold


JW TemperatureRegulator AC-OC

Pump

Flange Type

Flange Dimensions

Inner Dia.mm (in.)

Outer Dia.mm (in.)

Numberof Bolts

Bolt CircleDia.

mm (in.)

Bolt HoleDia.


G3606

A B C D

ANSI 6" ANSI 6" ANSI 6" ANSI 6"

G3608 ANSI 6" ANSI 6" ANSI 6" ANSI 6"

G3612 ANSI 6" ANSI 6" ANSI 6" ANSI 6"

G3616

ANSI 6" 168.3 (6.63) 279.4 (11.0) 8 241.3 (9.5) 20.5 (0.81) 25.4 (1.0)

ANSI 6" ANSI 6" ANSI 6" ANSI 6"

JW Inlet

JW Outlet

AC-OCInlet

AC-OCOutlet

Figure 64. Customer connections - Low Energy Fuel Cooling System.

AftercoolerOil Cooler

61

Weld FlangesProvided or Available


Customer Plumbing

Engine Block

C

E

E

D

E

B

A

Oil Cooler Aftercooler

Mixer Box/Manifold

AC-OCExpansion Tank

(Customer Provided)

External JW Pump(Customer Provided)

AC-OCHeat Exchanger

(Customer Provided)


AC-OCPump

Flange Type

Flange Dimensions

Inner Dia.mm (in.)

Outer Dia.mm (in.)

Numberof Bolts

Bolt CircleDia.

mm (in.)

Bolt HoleDia.


G3606

A B C D E

ANSI 4" CAT 5.5" CAT 6.5" CAT 4.5" CAT 5.5"

G3608 ANSI 4" CAT 5.5" CAT 6.5" CAT 4.5" CAT 5.5"

G3612 ANSI 6" ANSI 6" CAT 6.5" CAT 5.5" CAT 5.5"

G3616

CAT 4.5" 116 (4.57) 168 (6.61) 8 146 (5.75) 10.5 (0.41) 23 (0.91)

CAT 5.5" 143 (5.63) 194 (7.64) 8 174.6 (6.87) 10.5 (0.41) 23 (0.91)

CAT 6.5" 171 (6.73) 225 (8.86) 8 200 (7.87) 10.5 (0.41) 23 (0.91)

ANSI 4" 144.3 (4.5) 228.6 (9.0) 8 190.5 (7.5) 19.1 (0.75) 23.8 (0.94)

ANSI 6" 168.3 (6.63) 279.4 (11.0) 8 241.3 (9.5) 20.5 (0.81) 25.4 (1.0)

ANSI 6" ANSI 6" CAT 6.5" CAT 5.5" CAT 5.5"

JW PumpInlet

JW Eng.Outlet

AC-OCInlet

AC-OCOutlet

AC-OCReg Conn.

Figure 65. Customer connections - High Temperature Cooling System.

G3600 Heat RecoveryHeat BalanceTypes of Heat Recovery SystemsStandard Temperature System

Design Criteria for Standard Temperature SystemsHigh Temperature Systems

High Temperature Liquid Water SystemDesign Criteria for Water-Steam System

Water Quality TreatmentWater Quality and Treatment for Standard

Temperature SystemsWater Quality and Treatment for High Temperature

SystemsTotal Dissolved and Suspended SolidsMeasurement of TDS ControlAlkalinityTotal AlkalinityReserve or Hydroxide Alkalinity

Other Caterpillar Cooling System Related Publications

Heat Recovery

G3600 Engines convert about 35–41% of theirinput fuel energy into mechanical power.Another 22% is rejected to the cooling system,34% to the exhaust gas and 3% to theenvironment. A large portion of the heatenergy rejected to the cooling systems andcontained in the exhaust gas can berecovered by various means. In large engineslike the G3600s this recoverable energy isquite significant. The following sectionsdiscuss the means of harnessing this heatenergy.

Heat BalanceThe typical Heat Balance for the G3600engines is shown in Figure 66. Heat rejectionvalues for the following components isprovided for all G3600 Engines in theTechnical Data Manual or SpecificationSheets.

1. Jacket Water heat rejection 2. Oil cooler heat rejection 3. Aftercooler heat rejection 4. Exhaust heat rejection 5. Exhaust heat recoverable

Typical Heat Balance Calculations areillustrated in Figure 67. The values used inthe example are for illustration purposes andshould not be used for design. Refer to thepublished heat rejection data for the specificengine for design calculations.

65

Mechanical Work Energy 41%

Total Fuel Energy Input 100%

Exhaust Gas 34%

Radiation 3%Oil Cooling Water 5%

Engine JacketCooling Water 8%

AftercoolerCooler Water 9%

Figure 66. Typical Heat Balance for the G3600 Engines.

66

HEAT BALANCE EXAMPLE

Using a G3612 Combined Heat and Power (CHP) Engine with 11:1 compression ratiorated at 2990 bKw Prime Power at 1000 rpm, with the CHP cooling system, as anexample:

Engine Output 2990 bkW (4010 bhp) (At 100% load conditions)Generator Output 2875 kW (At 96.2% Generator Efficiency)

Heat Rejection Available (from Specification Sheet): kW (Btu/min)a) Engine Jacket (cylinder block) water at 99°C (210°F) 534 (30,321)b) Oil Cooler (std. shell & tube, 3 coolers) 365 (20,725)c) Aftercooler (single stage) 652 (37,021)

Total Heat Rejected to the cooling system 1551 (88,066)

Fuel input can be taken from the specification sheet or calculated as shown below,Total Fuel Input = BSFC 3 bkW in kW or = BSFC 3 bhp in Btu/min

3.6 60= 8.66 3 2990 = 7192 kW (409,009 Btu/min)

3.6

Recoverable Heat rejection can be taken from the Specification sheets or calculated.Total Exhaust flow from Specification Sheet = 20892 KG/hr (45.962 lb/hr)Exhaust Stack Temperature =359°C (678°F)

Recoverable Exhaust Heat Rejection at 120°C (248°F)*= Specific Heat of Exhaust Gas 3 Total Exhaust Flow 3 DT kW (Btu/min)= 1.107 KJ/KG.°C 3 (20892/3600) KG/sec 3 (359 2 120)°C 1554 (88,376)where Specific Heat of Exhaust Gases, Cp, is given in the Heat Rejection section of theCooling System chapter

Total Recoverable Heat Energy = Jacket water heat energy 1 Oil cooler heat energy 1 Aftercooler heat energy 1 Exhaust heat energy (at 120°C or 248°F)= 534 1 365 1 652 1 1554 = = 3105 kW (176,581 Btu/min)

Recoverable Heat in % = 3105 kW/Fuel input kW = (3105/7192) 100 = 43.2%

Brake Thermal Efficiency, h =bkW/Fuel input kW = (2990/7192) 100 = 41.6%

Total Thermal Efficiency = Brake thermal efficiency 1 Recoverable Heat energy= 41.6 1 43.2

Total Thermal Efficiency = 84.8%

* The values of Recoverable Exhaust Heat Rejection calculated with this formula will varyby ±3% from the specification sheet values due to changes in Cp value withtemperature and other conditions.

Figure 67. Heat Balance calculation for G3600 Engines — Example.

Types of Heat Recovery SystemsThe heat rejected to the jacket water, oilcooler and aftercooler can be totallyrecovered and 70% of the exhaust gas energyis economically recoverable as shown in theprevious example. Heat Recovery results intotal efficiencies as high as 85% for G3600Engines.

Heat Recovery design best suited for anyinstallation depends on many considerations,both technical and economical. The primaryfunction of any heat recovery system designis to cool the engine sufficiently. The enginemust be cooled even when the heat demand islow but power is still required.

Heat recovery methods are grouped intoStandard Temperature Systems (up to 99°Cor 210°F jacket water outlet temperature) andHigh Temperature Systems (up to 130°C or266°F jacket water outlet temperature). HighTemperature Systems can be liquid watersystems or water-steam systems.

Standard Temperature SystemThese Standard Temperature Heat RecoverySystems are designed to operate at coolanttemperatures below 99°C (210°F). These

systems are modified versions of the StandardCooling Systems and Combined Heat andPower Cooling Systems discussed in theprevious chapter on Cooling Systems.

Heat recovery of a standard engine mayamount to nothing more than utilizing heattransferred from the engine radiator. This airis usually 38–65°C (100–150°F). Therecovered heat is quite suitable for preheatingboiler combustion air, space heating, dryinggrain or lumber. The system cost is minimaland overall efficiency will increase toapproximately 60%. It is not recommended toplace the entire engine-radiator unit in the airduct, operational and maintenance problemscan result from the cool air flow across theengine. The radiator should only be placed inthe air duct.

A more versatile method of recovering heatfrom a standard temperature system is to usea heat exchanger to transfer rejected engineheat into a secondary circuit, usually processwater to heat load such as buildings orequipment. One of the commonly usedconfigurations is illustrated in Figure 68.There are many advantages inherent with thisdesign, the standard engine jacket waterpump, temperature regulators and bypass line

67

ExhaustHeat RecoveryDevice

Generator

1 2 3

Engine

Temperature Regulator


Engine CoolantHeat Exchanger

Separate CircuitCooling

A/C

O/C

Load BalancingTemperature Regulator

Load BalancingHeat Exchanger

To RemoteCooling Device

To Load

From Load

To Load

From Load

Figure 68. Standard Temperature Heat Recovery System.

are retained. The engine jacket water coolingsystem is isolated from the load process loop,which allows operation with antifreeze andcoolant conditioner. This alleviates waterquality concerns for using process water tocool the engine jacket. When engine is cold, atemperature regulator bypasses the enginecoolant heat exchanger and recirculates thecoolant within the engine. After the coolantreaches the opening temperature of thetemperature regulator, the regulator begins toopen and allows some coolant flow throughthe heat exchanger. The heat exchangertransfers heat energy to the load.

When normal process load is insufficient toabsorb enough heat, load balancingtemperature regulator limits jacket water inlettemperature by directing coolant through asecondary cooling source (load balancingheat exchanger). The secondary coolingsource should be incorporated in the engineloop, not the load loop. The load balancingdevice should be a heat exchanger or aradiator. Heat transfer through the loadbalancer is usually cyclical. If a radiator isused, it must be designed to withstandthermal shocks developed from the cyclicloading.

The second option of a standard heatrecovery system uses an exhaust heatrecovery device included in the system in

series, parallel or as a separate water or steamcircuit, see Figure 69. A muffler is included inseries with the engine system. Note theengine loop is still separate from the loadloop. The engine expansion tank may beutilized. Generally, boiler water is used as themedium in the load loop. Boiler water ispumped through the jacket water heatexchanger and the exhaust heat recoverymuffler in series where it is heated to thedesired temperature. As shown the water flowthrough the expansion tank provides de-areation.

A third variation on the standard heatrecovery system is to incorporate the exhaustheat recovery device into the engine coolingloop, see Figure 70. To ensure coolant flowthrough the muffler, the engine temperatureregulators and the by-pass line must beremoved and an external warm-uptemperature regulator must be added. Theadded restriction of the exhaust heat recoverydevice may exceed the allowable externalrestriction from the engine mounted pump.An auxiliary circulation pump may berequired. The advantages of this system arethat the obtainable process water temperatureis usually higher and there are fewercomponents. The disadvantages to thissystem are the engine cooling system ismodified, and the design of this system

68

Air Vent & Deareration

Pressure Cap &Vacuum Breaker Relief Valve

Expansion TankLow Water LevelShut DownExhaust

Heat RecoveryDevice

Generator

1 2 3

Jacket WaterPump

Engine

Excess FlowBypass ValveX Engine Mounted

Expansion Tank

J.W. HeatExchanger

Low Water FlowShut-Down

CirculatingPump




Load HeatExchanger

To Load

FromLoad


A/C

O/C

Figure 69. Standard Temperature Heat Recovery System – with series exhaust muffler.

becomes more critical to the successfulengine operation.

Any heat recovery system where the processwater circulates in the engine jacket is notrecommended. Experience has shown that inmost cases the user can not economicallytreat the quantity of process water to the levelrequired to avoid maintenance problems withthe engine.

The Combined Heat and Power Cooling Systemdiscussed in the Cooling Systems chapter alsoexplains similar heat recovery configurationsoffered.

Design Criteria for StandardTemperature SystemsThe purpose of the following discussion is tocall attention to certain basic criteria criticalto the proper operation of a heat recoverysystem, additional criteria may be required.Contact the Caterpillar dealer or the factoryfor specific requirements.

• The system must provide adequate coolantflow through the engine jacket to maintaincoolant temperature differential (outlet-inlet) below 6°C (11°F) at all conditions.

• The expansion tank must be the highestpoint in both the engine and the load loopcooling systems.

• Use only treated water or antifreeze, asrecommended in the Water Quality andTreatment for Standard Temperature Systemsection, in the engine jacket cooling circuit.

• Incorporate air vents to eliminate air trapsand locks as recommended in the sectionFilling and Venting.

• A load balancing temperature regulatormust be used to regulate coolant throughthe secondary cooling source to maintainjacket water inlet temperatures belowmaximum limits.

• Coolant must continually flow through theexhaust heat recovery device when theengine is operating to avoid thermal shockon hot muffler surfaces.

• To keep external resistance withinallowable limits for the engine mountedpump, locate heat recovery mufflers andheat exchangers as close to the engine aspossible. An engine mounted jacket waterpump requires a minimum inlet pressure,as specified in the section on Minimum

69

Air Vent & De-aeratrion Line


Expansion Tank

Low WaterLevelShut Down


Generator

1 2 3Engine

CirculatingPump


Warm-upTemperatureRegulator




To Load

From Load

To Load

From Load

A/C

O/C

Figure 70. Standard Temperature Heat Recovery System – combined JW and muffler circuit.

Suction Head in the Cooling Systemschapter, at all times.

High Temperature SystemsThe basic operation of these systems isalready described in the section on HighTemperature Cooling System in the CoolingSystem chapter. The aftercooler-oil coolercircuit in this system is similar to one in theStandard Cooling System. The jacket watercircuit is cooled by high temperature water.As mentioned earlier, there are two types ofhigh temperature systems, liquid water andwater-steam systems.

For both systems, the standard temperatureregulator and bypass are removed andreplaced by an external control. The standardjacket water pump is removed and must bereplaced by an external electric pump capableof the high temperature and pressures of thissystem.

Steam formation is not acceptable inside theengine jacket at any time for CaterpillarG3600 engines. The engines with HighTemperature cooling systems have a factoryprovided protection system to ensure thatthere is no steam formation inside the enginejacket. The protection system checks thetemperature pressure of the coolant at the

engine outlet to ensure that the minimumpressure is maintained for that temperature. Ifa low pressure at the engine outlet isdetected, the protection system shuts theengine down.

High Temperature Liquid WaterSystemThis system functions similar to a standardtemperature system, except for the elevatedjacket water outlet temperatures 99–130°C(210–266°F), see Figure 71.

A pressure cap or static head must beprovided in the engine coolant circuit toassure a pressure of 70–85 kPa (10–12 psi)above the pressure at which steam forms atthat particular engine outlet temperature ofthe coolant. The source of this pressure maybe a static head imposed by an elevatedexpansion tank or controlled air pressure inthe expansion tank. For 130°C (266°F) water,the pressure at the engine outlet should beminimum of 345 kPa (50 psi) to prevent steamformation. Maximum system pressureallowed on the engine jacket, measured at theinlet to the engine, is 460 kPa (67 psi). Excesspressure may result in internal water leaksand damage the water cooled turbochargerhousing.

70

Air Vent & De-aeratrion Line


Expansion Tank

Low WaterLevelShut Down


Generator

1 2 3Engine

CirculatingPump


Warm-upTemperatureRegulator




To Load

From Load

To Load

From Load

A/C

O/C

Figure 71. G3600 High Temperature Liquid Water System.

Design Criteria for Liquid WaterSystemThe criteria for this system is similar to theStandard Temperature Heat Recovery system:

• The system must provide adequate coolantflow through the engine so the enginecoolant temperature differential (outletminus inlet) does not exceed 6°C (11°F).

• The expansion tank must be the highestpoint in the cooling system. The pressurecap on the expansion tank should be ratedfor pressure higher than the inlet pressurerequirements of the jacket water pump.

• Proper water treatment is essential for thesuccessful system operation asrecommended in the section Water Qualityand Treatment for High TemperatureSystems.

• Incorporate de-aeration circuit and air ventsto eliminate air traps and locks asrecommended in the section Filling andVenting.

• A load balancing temperature regulatormust be used to direct coolant through asecondary cooling source to maintain thejacket water inlet temperature within limits.

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

• A high temperature system requires apressure control for the engine coolantcircuit to maintain a required range ofpressure.

• Water pumps must be suitable for use withelevated temperatures and pressures.

• An external warm-up temperature regulatoris required.

• The load balancing heat exchanger must beincorporated in the engine loop, not theload loop. The load balancing condensermay be either a heat exchanger or radiator.Heat transfer through the load balancer is

usually cyclic. Thus if a radiator is used, itmust be designed to withstand thermalshocks developed from cyclic loading.

• For multiple units that share a single steamseparator, all circulating pumps must runwhen any one engine operates. Thispractice prevents a severe thermal shock ifa unit is started later.

• High jacket water temperatures will resultin after-boil if there is a hot shut down. Addan additional 10% of system volume to thenormal expansion tank sizing guidelines.

High Temperature Water-SteamSystemThe high temperature water-steam system,see Figure 72, provides liquid water to coolthe engine, but then flashes it to steam to beused for loads requiring low pressure steam97 kPa (14 psi). A circulation pump forceswater through the cylinder block to the steamseparator. In the steam separator, some of thewater flashes to steam and the rest iscondensed back to water and returns to theengine.

The pressures shown in Figure 72 arerepresentative values. The relief valvepressure 103 kPa (15 psi) is set by boilercodes. Pressure in the separator is controlledby the pressure control valve. Once pressurebuilds to 97 kPa (14 psi), the control valveallows steam to flow. The actual steampressure in the load line is a function of loadrequirements. If the load is not consumingthe steam the pressure in the steam line willincrease. Once the pressure reaches 90 kPa(13 psi), the excess steam valve will open totransfer engine heat to the waste coolingdevice (load balancing condenser).

Caterpillar requires excess steam valve to belocated downstream of the pressure controlvalve. If it is upstream, the pressure controlvalve will not function properly.

Design Criteria for Water-SteamSystem• The system must provide adequate coolant

flow through the engine so the enginecoolant temperature differential (outletminus inlet) does not exceed 6°C (11°F).

71

• There are no elevation or static headrequirements for the steam separator otherthan what suction head is used for thecirculating pump. So, this system may beused in locations with limited overheadclearance.

• Since a electric motor driven pump shouldbe used for the jacket water circuit, it isimportant to insure that the pump isoperating while the engine is running. Thepump should continue runningapproximately five minutes after the engineis stopped, to cool the engine.

• Maximum temperature at the engine outletmust not exceed 130°C (266°F). Inletpressure to the pump should be maintainedwithin limits to prevent cavitation at thehigh temperatures.

• A pressure switch is required at the jacketwater inlet to the engine to monitorabsolute pressure.

• Use only treated water in the engine jacketcooling circuit as recommended in thesection Water Quality and Treatment forHigh Temperature Systems. Continuouswater chemistry monitoring with automatic

boiler blow-down devices arerecommended.

• A low water shutdown on steam separatordevice is required. A low water level pre-alarm is also recommended. Low waterlevel could cause engine overheating andserious damage.

• The excess steam valve cannot be in thesteam separator and must be downstreamof the pressure control valve.

• No warm-up temperature regulator isrequired since the pressure control valvedoes not allow any heat (steam) to exit thesystem until the engine has warmed up andthe separator has reached system pressure.

Water Quality and TreatmentThe coolant used in the Caterpillar G3600engine cooling systems should adhere to thespecifications given in the following sections.If the available coolant is not withinacceptable limits, proper water or coolanttreatment should be incorporated to use thatcoolant.

72

Low Water LevelShut-down

Water LevelControl

CondensatePump

Condensate Tank

Make-upWater

Air Eliminator

LoadBalancingCondenser

To WasteCooling Device

Excess SteamValve13 psig

SteamTo Load14 psig

CondensateFrom Load

Pressure ControlValve


Generator

1 2 3Engine

15 psig MaximumRelief Pressure

CirculatingPump

To LoadFrom Load

X

X

X


A/C

O/C

SteamSeparator

Figure 72. G3600 High Temperature Water – Steam System.

Water quality is prime consideration in closedor open cooling systems. Excessive hardnesswill cause deposits, fouling and reducedeffectiveness of the cooling systemcomponents. Water used for initial fill andmakeup must meet the criteria shown in thesubsequent sections.

If the engine is expected to operate underfreezing conditions, antifreeze must be addedto the coolant. Ethylene glycol or propyleneglycol is recommended. They both havesimilar properties, but propylene glycol hasslightly better heat absorption capability thanethylene glycol. The concentration requiredfor ethylene glycol can be determined fromFigure 73.

If the operating temperature will not dropnear freezing, water with a 6–8% mixture ofcoolant conditioner is recommended forcooling systems. For more information onrecommended coolant composition, refer tothe Caterpillar publication Coolant and YourEngine (No. SEBD0970).

Caterpillar recommends using a 50%/50%mixture of glycol and water by volume in allG3600 engines. Concentrations less than 30%require the addition of corrosion inhibitors tomaintain cleanliness, reduce scale andfoaming and to provide acidity and alkalinity(pH) control. The corrosion inhibitor must becompatible with the glycol mixture and notdamage flexible connections, seals or gaskets.Avoid sudden change in coolant compositionto minimize adverse effects on non-metalliccomponents. Caterpillar antifreeze containsthe proper amount of coolant conditioner.Caterpillar inhibitors are compatible withglycol base antifreeze. The reduction in heattransfer capability of the coolant by theaddition of antifreeze is explained in thesection Radiator Design Criteria.

Note: Do not use coolant conditionerelements or liquid coolant conditioners withDowtherm 209 full-fill coolant. Soluble oil orchromate solutions should not be used.Methoxypropanol based coolants must not beused in G3600 Engines.

Water Quality and Treatment forStandard Temperature SystemsWater hardness is usually described in partsper million, ppm (or grains/Gal) of calciumcarbonate content. Water containing up to60 ppm (3.5 grains/Gal) is considered softand causes very few deposits. Usable waterfor cooling systems must be below thefollowing limits:

Chloride (CL) 40 ppm (2.4 grains/Gal)Sulfate (SO4) 100 ppm (5.9 grains/Gal)Total Hardness 170 ppm (10 grains/Gal)Total Solids 340 ppm (20 grains/Gal)pH 5.5–9.0

Water softened by removal of calcium andmagnesium is acceptable. Distilled or de-ionized water is preferred over water softenedby salts. Corrosion inhibitors added to wateror antifreeze solution maintain cleanliness,reduce scale and foaming and provide pHcontrol. With the addition of an inhibitor, a pHof 8.5 to 10 should be maintained.

Figure 73. Recommended glycol concentration.

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Water Quality and Treatment for HighTemperature SystemsThe engine cooling water for a low pressuresteam (water-steam) or high temperaturewater system is circulated within the enginewater jacket at temperatures above 99°C(210°F). As a result, there is a potential forsteam to form in both of these applications.For these purposes, treat the engine coolantas for a steam boiler. Since several localizedareas of the engine jacket water system canhave very high heat flux rates and verynarrow water flow passages, the engine waterchemistry will have the same chemistry as aclose tolerance steam boiler. The coolantspecifications published above and in theCaterpillar Operator Manual are for less than99°C (210°F) ethylene glycol or propyleneglycol systems. This is not applicable for lowpressure steam and liquid water heatrecovery systems.

Minerals in the water can precipitate duringthe heating process and form deposits withinthe cooling system of the engine. Thesedeposits can restrict the heat transfer andwater circulation, resulting in engine failure.To prevent these deposits within the coolingsystems, the following engine jacket water(boiler water) quality guidelines arerecommended.

Make-up water is added to a low pressuresteam system to replace steam and blow-downlosses. It should not exceed the followingmaximum concentrations:

Iron 0.1 ppmCopper 0.05 ppmTotal Hardness 0.3 ppm as CaCO3

The make-up water can be treated to reduceor remove, the impurities from the water. Ingeneral, the water is treated when one ormore of the feed water impurities is too highto be tolerated by the system. There are manytypes of water treatment — softening,evaporation, de-aeration and ion exchangethat can be used to treat make-up water for aparticular system.

Feed Water is a mixture of returningcondensate and make-up water that enters theengine jacket water loop to replace steam that

has left the engine jacket water loop. Watertreatment chemicals that are added to thesystem are usually mixed with the feed wateras it enters the engine jacket water system.

Engine jacket water (boiler water) is amixture of feed water and resident water. It isthe water circulated within the water jacket ofthe engine to cool the engine and recoverheat. Engine jacket water (boiler water)should not exceed the following maximumconcentrations:

Silica Concentration 150 ppm as SiO2Total Alkalinity 700 ppm as CaCO3Specific Conductance 3500 micro mho per cm Total Suspended solids 10 ppm

In addition to the above chemistry, Caterpillarrecommends the engine jacket water (boilerwater) be treated with chemicals as listedbelow:

• An oxygen scavenger to remove oxygenfrom the feed water with sufficient reservein the engine jacket (boiler water) toremove all the oxygen from the water.

• Maintain 200 to 400 ppm as CaCO3equivalent of hydroxide alkalinity in theengine jacket water (boiler water). Thereserve alkalinity prevents corrosion andcauses precipitation of iron and silica in theform that can be removed by blow-down.

• A blend of dispersants to adequatelycondition and suspend the precipitationsolids in the water. The dispersants keepthe solids suspended until they areremoved during blow-down.

• Appropriate treatment of the steam toprovide condensate returning to the enginethat meets the engine jacket water (boilerwater) specifications.

Total Dissolved and Suspended SolidsDepending on the make-up water source andtreatment, the feed water will contain somedissolved and suspended solids. On a lowpressure steam system, the steam will leavethe engine; the minerals and chemicals willremain. This results in a concentrating of thetotal Dissolved Solids (TDS). The amount of

74

makeup water per hour approximatelyequals twice the system volume. This meansfor feed water with a TDS of 100 ppm, theTDS in the engine jacket water will increaseby 200 ppm per hour.

Engine jacket water scale forms when theconcentration of solids reaches a critical point.This depends on the type of contaminants inthe feed water, engine operating temperatureand other factors. The maximum allowableconcentration of dissolved solids can beexpressed in parts per million TDS or interms of conductivity (micro mhos/cm).

Measurement of TDS ControlTDS can be measured by ppm or byconductivity (micro mhos/cm). TheCaterpillar level for TDS is given in michromhos/cm because conductivity is easier tomeasure with commercial continuousmonitoring equipment or hand-heldequipment. There is a direct relationshipbetween ppm and conductance, 3500 mhos =2680 ppm.

To avoid exceeding the maximum allowableconductivity, it is necessary to drain off someof the engine jacket water (boiler water)periodically. This is referred to as boilerblow-down. As it occurs new feed water isadded to dilute the water in the engine waterjacket, thereby reducing its conductivity.Historically operators have performed blow-down manually by periodically opening avalve to drain the steam separator. This maybe done once per hour, once per shift or someother interval, depending on thecircumstances.

A less common method of monitoring TDS isto measure chlorides in both the enginejacket water (boiler water) and the make-upwater by a titration process. Since chloridesare not affected by chemical treatment, theoperator can determine the number ofconcentrations that have occurred in theengine jacket water (boiler water) bycomparing the ratio of the two values. Basedon known values of the make-up water, theoperator can calculate the acceptable numberof concentration that can occur beforeblow-down is required.

Because blow-down is only performedperiodically, significant dilution is needed toensure that the engine jacket water (boilerwater) conductivity does not exceed themaximum before the operator returns toblow-down the engine again. Note that theconductivity can exceed targeted maximum oreven absolute maximum if the operator doesnot blow-down the boiler at the appointedtime, or if the engine steaming rate increasesbetween blow-down operations. If the absolutemaximum is exceeded, scaling will occur.Because small amounts of scale wastesenergy and can lead to engine damage, it isvery important to stay below the absolutemaximum. Conversely, the steam productionrate may decrease and as a result the operatorwould blow-down the engine sooner thannecessary. Therefore, Caterpillarrecommends continuously monitoring of TDSand automatic blow-down controls.

AlkalinityAlkalinity is required in a high temperaturewater and a low pressure steam system toprevent corrosion. Alkalinity holds silica insolution and causes iron to precipitate in aform removable by blow-down. Too muchalkalinity can result in a high pH and causecaustic cracking and caustic attack to externalengine compartments.

Total AlkalinityTotal alkalinity is usually measured on site bya titration with methyl orange and isfrequently referred to as “M” alkalinity. Manycoolant analysis companies refer to pH ofcoolant water. Because of the wide variation inlocal make-up water and commercialtreatments, there is no direct correlationbetween total alkalinity and pH. Generally, inhigh temperature water and low pressuresteam systems, the pH will be in a range of10.0 to 11.5 pH

Reserve or Hydroxide AlkalinityTo prevent corrosion and scale deposits, areserve of hydroxide (OH) alkalinity isrequired. The OH alkalinity is not easilymeasured in the field, but can be calculated. A"P" alkalinity is measured by phenopthaleinand sulfuric acid titration. Once “P” value is

75

determined, the following formula is used tocalculate “OH” alkalinity.

“OH” Alkalinity 52 3 “P” Alkalinity 2 “M” Alkalinity

Low pressure steam engines will have specialrequirements if the unit does not runcontinuously. Any low pressure steam enginethat is shut down frequently can be prone todeposits even with good water treatmentprograms. Once the engine is shutdown, thedispersants in the feed water can no longerkeep the solids in suspension. They willcollect and harden to form scales and canresult in engine failure. For engines that donot run continuously, we recommend acirculating pump of 100 lb water/lb of steamcapacity to be operated even while the engineis shutdown to keep the solids in suspension.

The above water chemistry limits arestringent, but not when considering thatdeposits formed inside the engine arecumulative. Cogeneration and heat recoveryequipment is intended to last 20 years orlonger. To maintain performance and value ofequipment, it is important to eliminate scaledeposits within engines. Once a deposit isformed it is very difficult and may beeconomically impractical to remove. Toemphasize again, scale formation iscumulative and the successful method ofavoiding scale is to not permit conditions forscale to form. These guidelines are based onestablished limits of the American BoilerManufacturer’s Association (ABMA) andsuggested guidelines by the ASME researchcommittee on Water in Thermal PowerSystems. We have reasonable confidence thatoperators who adhere to these guidelines willhave years of deposit free and scale freeperformance from their Caterpillar Engines.

Since water chemistry and water treatmentare very regional items and tend to varyconsiderably around the world, the engineowner has the ultimate responsibility for theengine water treatment.

A comprehensive discussion of feed waterproblems and treatment of boiler feed water isavailable in a bulletin from Nalco ChemicalCo. To obtain the bulletin, write to:

Nalco Chemical Co1 Nalco CenterNaperville, IL 60566Attention: Marcom Dept.

Request bulletin 30, titled “Boiler feed WaterTreatment”. There is no charge for thebulletin.

Other Caterpillar CoolingSystem Related PublicationsIn addition to this publication the user isrecommended to refer to other relatedCaterpillar publications for more information.Some of them are listed below, for otherinformation contact your Caterpillar dealer orthe factory.

• Cooling System Fundamentals (text andslides) LEKQ1475

• Coolant and your Engine SEBD0970

• Special Instructions – Storage Proceduresfor CAT products SEHS9031

• System Operation and Adjustment – G3606and G3608 engines SENR4258

• System Operation and Adjustment – G3612and G3616 engines SENR5528

76

G3600 Lubrication SystemGeneral System Description

Engine SumpStrainerMain Oil PumpEmergency PumpsOil ThermostatsOil CoolerOil FiltersPriority ValveOil Metering Pump

PrelubricationAir Prelube MotorTypes of PrelubricationIntermittent Prelube SystemQuick Start Prelube System

PostlubricationLubricating Oil Heaters (Optional)Oil Level Alarm, Shutdown, and Makeup (Optional)Oil Level Gauge (Dipstick)

Oil SelectionCaterpillar Natural Gas Engine Oil (NGEO)Commercial OilsSour Gas & Alternate Fuel Gas ApplicationsMulti-Viscosity OilsSynthetic OilsLubricant Viscosity

Monitoring Lubricating Oil QualityScheduled Oil Sampling (S•O•S)Lubrication Oil Condemning LimitsOil Change IntervalOil Consumption

G3600 Lubrication

General System DescriptionFigures 74 and 75 show the G3600 lube oilsystem. Figures 76 and 77 contain simplifiedschematics of the lubrication circuit. Figures78 and 79 show oil and coolant flow directionsthrough the oil cooler bundles. Below is adescription of each component in the system.

Note: The G3600 lubrication circuit has beendesigned such that only filtered oil reachesthe cylinder block main oil manifold. At notime (during prelubrication/postlubrication,engine startup, or during normal engineoperation) is unfiltered oil allowed to enterthe cylinder block main oil manifold.

Engine SumpTable 1 contains the sump capacities forG3600 engines. Use the oil level gauge toinsure proper fill after each oil change.

Table 1.

StrainerThe strainer is a 650 micron (0.025 in.) screenlocated between the suction bell and suctiontube.

Main Oil PumpThe main oil pump is a fixed displacementpump. The pump output depends on enginespeed and varies little with back pressure.The pump operates at 1.524 times the enginespeed. Table 2 contains the pump flow rates.It is important to note that not all of the oilpumped goes through the cooler/filter circuit.To maintain 430 kPa (63 psig) to the main oilmanifold, a significant quantity is bypassedimmediately back to the sump via the priorityvalve (see priority valve in this section).

Table 2.

Emergency PumpsEmergency pumps may be required in someapplications in case of main oil pump failure.Table 3 contains the flow rates to fulfillminimum lubrication requirements at fullpower for rated speeds between 700 and 1000rpm.

Table 3.

Oil ThermostatsThe oil thermostats begin to divert oil to thecoolers between 75°C and 78°C (167°F and172°F). The full open temperature of an oilthermostat is 85°C. The desired steady stateoil temperature is 83°C.

Oil CoolerThe oil coolers are of tube bundleconstruction. The coolant water is containedin the tube side; the oil is contained in theshell side of the oil cooler.

G3606 and G3608 engines use two oil coolerbundles. The maximum water approachtemperature to the coolers is 54°C (140°F).

G3612 and G3616 engines may use two orthree oil cooler bundles. If two oil coolers areused, the maximum water approachtemperature to the coolers is 32°C (90°F). Iftwo oil coolers are used, the maximum water

Minimum Flow Rates forEmergency Oil Pump, Lpm (gpm)

G3606

G3608

G3612

G3616

750 (198)

770 (203)

890 (235)

1200 (317)

Main Oil Pump Flow Rates

Engine *Pump Type**900 rpmLpm (gpm)

**1,000 rpmLpm (gpm)

G3606

G3606

G3608

G3608

G3612G3612

G3616

G3616

high speed

low speed

high speed

low speed

high speed

low speed

high speed

low speed

1,000 (263)

1,260 (333)

1,260 (333)

1,470 (388)

1,470 (388)

1,630 (430)

1,630 (430)

2,050 (540)

1,110 (293)

1,400 (370)

1,400 (370)

1,630 (431)

1,630 (431)

1,810 (477)

1,810 (477)

2,280 (600)* High speed pumps are used for constant speed applications at 900

or 1000 rpm. Low speed pumps are used for variable speed applications ranging from 800 to 1000 rpm.

**Engine speed

G3600 Sump Capacities

G3606

G3608

G3612

G3616

708 (187)

912 (241)

1,030 (272)

1,325 (350)

* Stopped, Cold EngineFull Volume, L (gal)

* Corresponds to oil in pan temperature of 21°C (70°F)

79

80

1. Oil Pump2. Prelube Pump3. Oil Coolers4. Oil Filters5. Oil Themostat Housing6. Oil Filter Duplex Valve Handle7. Priority Valve8. Emergency Oil Connection

* Flow in Opposite Direction During Prelube

9. Oil Manifold (Oil to Bearings)10. Oil Manifold (2) (Oil to Piston Cooling

Jets)11. Oil to Main Bearings12. Oil to Camshafts13. Turbocharger14. Bypass Oil15. Check Valve16. Piston Cooling Jets

approach temperature is 54°C (140°F). Forwater inlet temperatures above 54°C (140°F)consult the factory for custom, off-engine plate-type heat exchangers.

Figures 78 and 79 show oil and coolant flowdirections through the oil cooler bundles. Themaximum water flow through one tube bundleis 1,000 lpm (260 gpm). Exceeding this flowlimit will cause erosion and weaken the tubewalls.

Figure 74. G3600 Inline Lubrication System.

81

1. Oil Pump2. Prelube Pump3. Oil Coolers4. Oil Filters5. Oil Themostat Housing6. Oil Filter Duplex Valve Handle7. Priority Valve8. Emergency Oil Connection

* Flow in Opposite Direction During Prelube

9. Oil Manifold (Oil to Bearings)10. Oil Manifold (2) (Oil to Piston Cooling

Jets)11. Oil to Main Bearings12. Oil to Camshafts13. Turbochargers14. Bypass Oil15. Check Valve16. Piston Cooling Jets

Figure 75. G3600 Vee Lubrication System.

82

IntakeAir Plenum

Vent to Sump

Vent to Sump

Breather to Atmosphere

Engine Sump

Strainer

IntermittentPump

Intermittent Prelube

Oil Cooler

Oil Cooler

Oil TempRegulator

MainOil

Pump

Check ValveCheck Valve

Oil MeteringPump Priority Valve

Oil Filter (3 Filter Elements)

FilterChangeValve


Main Oil Manifold(Oil to Bearing):ContinuousFlow

Bypass Valve:Flow to SumpBegins at 430 kPa(63 psi)

Relief Valve:Flow to SumpBegins at 1000 kPa(145 psi)

Piston CoolingJet Manifold: FlowBegins at 140 kPa(20 psi)

Figure 76: G3600 Engine Lubrication System with Intermittent Prelube.

83

Optional Quick Start Prelube

Figure 77: G3600 Engine Lubrication System with Optional Quick Start Prelube.

IntakeAir Plenum

Vent to Sump

Vent to Sump

Breather to Atmosphere

Spill Valve Pilot Line

Engine Sump

Strainer

ContinuousPump

(6 gpm)

Oil Cooler

Oil Cooler

Oil TempRegulator

MainOil

Pump

Check ValveCheck Valve

Oil MeteringPump Priority Valve


SpillValve

Flow to SumpWhen PilotPressure isBelow 48 kPa(7psi)

FilterChangeValve


Main Oil Manifold(Oil to Bearing):ContinuousFlow

Bypass Valve:Flow to SumpBegins at 430 kPa(63 psi)

Relief Valve:Flow to SumpBegins at 1000 kPa(145 psi)

Piston CoolingJet Manifold: FlowBegins at 140 kPa(20 psi)

BoosterPump

(17 gpm)

Check Valve

Oil FiltersEach engine contains six oil filter elements.The filter change valve allows filter elementsto be changed during engine operation. Theoil filters are rated at 20 microns. The oil filterchange interval is 1000 hrs. The maximumallowable pressure drop across the filters is103 kPad (15 psid).

Priority ValveThe priority valve regulates oil pressure at theinlet to the cylinder block main oil manifoldnot at the oil pump. Thus, the oil manifoldpressure is independent of the pressure dropacross the oil filter and oil cooler. The priorityvalve serves the four following functions:

1) The priority valve serves as the passage tothe engine's main oil manifold. Only filteredoil passes to engine's main oil manifold.

2) It diverts flow to the piston cooling jetsonce pressure at the valve reaches 140 kPa(20 psig). Only filtered oil passes to theengine's cooling jets.

3) The priority valve contains a bypass valveto control the oil pressure to the main oilmanifold. The desired pressure to the mainoil manifold is 430 kPa (63 psig). Thebypass valve adjusts pressure by directingunfiltered oil to the oil sump.

4) The priority valve contains a relief valve toprotect the system from excessive oilpressure. When system pressure at thevalve reaches 1000 kPa (145 psig) the valvebegins to divert flow back to the sump. Therelief valve directs unfiltered oil back to theoil sump.

Oil Metering PumpThe oil metering pump is driven by thecamshaft. The oil metering pump issometimes called a 'mister pump' as it forcesoil droplets into the air stream in the airplenum. The purpose of aerating the oil in theair plenum air stream is to provide furtherlubrication of the intake valves.

PrelubricationAll G3600 engines must be adequatelyprelubed prior to cranking or rotating thecrankshaft with the barring device.

Prelubrication systems supplied by Caterpillarare integrated with starting controls, electricor air powered pumps, check valve andengine piping.

For remote mounted prelube pumps, thepump must be located and piped to preventexcessive inlet restriction. The maximumallowable line velocity at the prelube pumpinlet is 1.5 m/sec (5 ft/sec) to prevent pumpcavitation. The net positive suction headrequired to fill the pump is 2m H20(6.5 ft H20).

Air Prelube MotorA schematic for the air flow to an air prelubemotor is shown in Figure 80. The air prelubemotor operates at 689 kPa (100 psig); airconsumption is 1.84 m3/min (65 ft3/min). Airconsumption is given at standard conditions.

Types of PrelubricationThere are two prelubrication systemsavailable for G3600 engines. The standardsystem is an intermittent prelube system.The intermittent prelube gives suitableperformance for applications not requiringquick start capability. The other prelubeoption is a quick start prelube system. Aquick start system significantly reduces theamount of prelube time prior to engine crank.Refer to the G3600 Price List for the variousoptions available.

Intermittent Prelube SystemAn intermittent prelube system sends filteredengine oil to the main engine manifold priorto startup. The system uses an enginemounted motor and pump. The prelube pumpcan be driven by either an electric motor, acompressed air motor, or a compressednatural gas motor.

In Figure 76 is shown a schematic of anintermittent prelube system. Oil is drawnfrom the sump, passes through the prelubepump and is sent to the oil coolers (if needed)and oil filters. The oil enters the priority valve

84

85

Coolant Circuit

Figure 78: G3600 Oil and Coolant Flow for Two Bundle Oil Cooler.

Oil Circuit

Oil Thermostat Housing

Front Oil Cooler

To Priority Valve andOil Mister Pump

From Oil Pump

From CoolantPump

To Radiator or Heat Exchanger

Rear Oil Cooler

86

Coolant Circuit

Figure 79: G3600 Oil and Coolant Flow for Three Bundle Oil Cooler.

Oil Circuit

Oil Thermostat Housing

Front, Top Oil Cooler

To Priority Valve andOil Mister Pump

From Oil Pump

To Radiator or Heat Exchanger

Front, Bottom Oil Cooler

From CoolantPump

Rear, Bottom Oil Cooler

mounted on the front housing of the engineand then passes to the engine's main oilmanifold.

The intermittent prelube sequence follows:

1) The start initiate signal is given from theESS panel.

2) Prelube motor begins to operate.

3) Prelube motor continues as the oil pressurein the main oil manifold rises.

4) As the oil manifold pressure rises, theprelube pressure switch will close at6.89 kPa (1 psig). (The prelube pressureswitch is located at the right rear of theblock.)

5) Thirty seconds after the prelube pressureswitch closes, the starters are engaged.

6) The prelube motor continues to operateuntil the engine reaches 250 rpm.

Intermittent prelube time will vary with oiltemperature. Typical intermittent prelubetimes, measured from the start initiate signalto starter engagement, is 90 to 120 secondswith 25°C (77°F) oil (with a 30 second delayafter the pressure switch closes).

Quick Start Prelube SystemThe quick start prelube system consists oftwo electric prelube pumps, a 23 Lpm (6 gpm)continuous pump and a 64 Lpm (17 gpm)booster pump.

In Figure 77 is shown a schematic of a quickstart prelube system. When the engine is off,the continuous pump draws oil from the sumpand sends oil to the coolers (if needed), oilfilters, priority valve and the engine's main oilmanifold. Oil level is maintained near the topof the cylinder block by a pilot operated spillvalve.

When the engine is signaled to start, thecontinuous pump shuts off and the boosterpump starts. The pressure created by thebooster pump is sufficient to close the pilotoperated spill valve and quickly fill the engineas well as close the oil pressure switch at theright rear of the cylinder block.

The engine control software is set to a zerosecond delay between pressure switch closureand engine crank, so the engine startsimmediately. Upon starting, the spill valveremains closed.

When the engine shuts down, the intermittentpump will postlube. After postlube the oilpressure decreases and the pilot controlledspill valve opens and the prelube pressureswitch opens. When the pressure switchopens the continuous pump will energize andmaintain the oil level in the engine.

The quick start prelube sequence follows:

1) While the engine is not operating, thecontinuous prelube pump circulates lowpressure oil through the engine's main oilmanifold. The oil level is maintained nearthe top of the block by the spill valve.

2) Once the start initiate signal is givenfrom the ESS panel the continuous pumpstops and the booster pump beginsoperating.

3) The pressure created by the booster pumpcloses the pilot operated spill valve.

4) Oil manifold pressure quickly rises sincethe spill valve is closed and the manifold isalready filled with oil. The prelube pressureswitch will close at 6.89 kPa (1 psig). (Theprelube pressure switch is located at theright rear of the block.)

5) Immediately after the prelube pressureswitch closes the starters are engaged.

6) The booster pump continues to operateuntil the engine reaches 250 rpm.

Quick start prelube time will vary little withoil temperature. Typical quick start prelubetimes, measured from the start initiate signalto starter engagement, is 5 to 7 seconds with25°C (77°F) oil (with a 0 second delay afterthe pressure switch closes).

PostlubricationG3600 engines have a standard postlube cycleof sixty seconds. Postlubrication protects theturbo's bearings upon engine shutdown.

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An engine will not postlube if the EmergencyStop (E-Stop) button is depressed toshutdown the engine. Since an oil leak couldpotentially require the use of the E-Stopbutton, the postlube is disabled to stop oilflow to a possible leak. An E-Stop button islocated on the ESS panel, junction box, andthe customer terminal strip. Since no postlubeoccurs with the use of the E-Stop button, theE-Stop should only be used for emergencyshutdowns.

Lubricating Oil Heaters (Optional)Oil heaters are recommended for heating thelube oil to 10°C (50°F) when ambientconditions are below this temperature.Heating elements in direct contact withlubricating oil are not recommended due tothe danger of coking. To avoid coking the oilwhen heating oil, heater skin temperaturesmust not exceed 150°C (300°F) and musthave a maximum heat density of 1.24 w/cm2

(8W/in2).

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Figure 80: G3600 Air Prelube.

ESS Panel Exhaust

Air PrelubePump

Prelube SolenoidValve

PressureReliefValve

PressureRegulator

Prelube OilPressureSensor

EngineBlock

EngineSump

PressureReliefValve

Lubricator

Starter RelayValvePressure

Regulator

Strainer LubricatorStarter RelayValve

Air Starter

Barring Device

Starter SolenoidValve

Electrical SignalAir CircuitOil Circuit

Customer Supplied

AirCompressor

WaterSeparator

AirFilter

Air StorageTank

CheckValve

Exhaust

Oil Level Alarm, Shutdown, andMakeup (Optional)The oil level alarm and shutdown switchesalert the operator when low oil levels arepresent. The oil level alarm should soundwhen the oil in the sump drops below the Addmark on the oil level gauge (dipstick). An oillevel shutdown occurs when the oil in thesump drops below an acceptable level in thesump.

It is important to mount the oil level alarmand shutdown switchgauges in the properlocation. Failure to properly locate the gaugescould result in premature alarm/shutdownconditions or allow the sump oil level to dropfar below recommend levels before thealarm/shutdown is activated. See Figure 81for proper mount locations.

Most oil level switches and oil level makeupdevices are vented. If vented to theatmosphere they will regulate to someerroneous level due to the crankcasepressure. The vent line from these devices

should go to the crankcase (well above the oilline).

An oil makeup system maintains a constant oillevel in the oil sump. The system should addoil to the sump when the level drops belowthe Running Full mark on the oil level gauge(dipstick). See Figure 81 for proper mountlocation. This automatic system senses the oillevel and feeds oil into the sump from anexternal oil reservoir as required. Theexternal reservoir must be able to feed the oilinto the sump at all operating conditions.Some makeup systems are pump operatedwhile others are gravity fed. Depending onthe height at which the makeup line entersthe oil pan, pressure in the oil pan can rangefrom 0 kPa to 7 kPa (0 psig to 1 psig). Ingeneral, the oil pressure prior to the makeupvalve should be above 21 kPa (3 psig).However, each system should be inspected toinsure proper operation and positive flow.

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Vent Line: Vent eack component to crankcase pressure

Figure 81. Locations for Oil Level Alarm, Shutdown, and Makeup Gauges.

A: Oil Level MakeupB: Oil Level AlarmC: Oil Level Shutdown

Sump

Block

Top of Oil Pan

A

175 mm

BC

341 mm261 mm

Oil Level Gauge (Dipstick)The oil level gauge has three graduations onit as shown in Figure 82. Below is adescription of each mark:

• STOPPED FULL OIL COLD NOPRELUBE: This mark indicates thecorrect oil level for a drained engine (no oil in block), 25°C (77°F) oil, and noprelube operating.

• RUNNING FULL: This mark indicates thecorrect oil level for a running engine withan oil to block temperature of 83°C(181°F).

• ADD: Below this level oil should be added.If the oil level is below the ADD line duringengine operation, oil should be added untilthe RUNNING FULL mark is reached. Ifthe oil level is below the ADD line for astopped, drained, and cool engine, oilshould be added until the STOPPED FULLOIL COLD NO PRELUBE mark is reached.

Oil SelectionCaterpillar does not recommend lube oils bybrand name. Field operation may identify oilbrands which yield good results. Oils whichmay be listed as having good fieldoperating results by oil companies do notform a Caterpillar recommendation. Theyserve only as potential oils which may besuccessful. Each particular oil company hascontrol of its product and should beaccountable for its oil performance.

Caterpillar Natural Gas Engine Oil(NGEO)Caterpillar has an oil formulated to providemaximum performance and life in CaterpillarGas Engines. This low ash oil has 0.45%sulfated ash (ASTM D874) and 5.0 Total BaseNumber (TBN), (ASTM2896).

Caterpillar NGEO is formulated from selectbase stock blended with special additives toprovide excellent anti-oxidation/nitrationproperties and thermal stability. Cat NGEOreduces levels of carbon and sludge formationand provides excellent oil and filter life. Theproduct has superior resistance to foaming,exhibits good demulsibility, and providesprotection against corrosion. This oil uses anadditive technology which offers excellentvalve and seat protection, improved pistoncleanliness, and control of deposit formation.

Caterpillar NGEO is especially useful forCaterpillar Gas Engines when used with fuelshaving a concentration of hydrogen sulfide(H2S) at 0.10% by volume, or less. Sites usinglandfill or biogas fuels would typically havesuch H2S concentrations.

Commercial OilsNo universal industry specifications aredefined for the performance requirements oflubricating oils for G3600 engines. Thefollowing guidelines have been established forcommercial oils to be used in G3600 engines.These oil requirements are for processednatural gas.

• Caterpillar recommends the use of oilsformulated specifically for heavy duty gasengines--oils that are designed for gasengines operating at 1240 kPa (180 psi)BMEP rating. Do not use oils formulatedexclusively for gasoline or diesel engines.

• Caterpillar recommends oils that havesulfated ash values between 0.40 and 0.60%to be used in G3600 engines.

• Caterpillar recommends oils that havesuccessfully completed 7,000 hours ofdocumented field service in G3600 engines.The field trial must be performed in asimilar configuration to the proposedengine and at a power level (BMEP) that

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Figure 82. G3600 Oil Level Gage (Dipstick).

Add Running Full Stopped Full Oil Cold No Prelube

meets or exceeds the proposed engine.During the field trial, the followingparameters must be monitored: oilconsumption, oil deterioration and valverecession. At the completion of the fieldtrial, the condition of the oil and the enginemust be within the following limits.

• No ring sticking or ring scuffing.• No liner scuffing or carbon cutting from

excessive piston top land deposits.• Valve recession and deposits must not

exceed the limits established forCaterpillar G3600 engines.

• Oil consumption must not exceed twotimes the initial oil consumption. Initialoil consumption is established duringthe first 1000 hours of operation.

• At the end of all specific oil changeperiods, the oil condition must remainwithin Caterpillar's limit for oxidation,nitration, TBN, TAN, and wear metals.

• At the end of the 7,000 hour field trial,two pistons must be removed for visualinspection. Photographs of the pistons,piston rings, and cylinder liners arerequired.

Sour Gas & Alternate Fuel GasApplicationsSour gas generally refers to fuels containing ahigh concentration of sulfur compounds(above 10 ppm), primarily hydrogen sulfide(H2S). Fuels such as field, digester, bio-mass,or landfill gas generally fall in this category.Sweet gases are fuels with low concentrationsof sulfur compounds (below 10 ppm).

If gas with excessive sulfur levels is used as afuel, sulfur compounds could be dissolved inthe oil from blow-by gas and cause corrosiveattack on internal engine components. Thecorrosion usually is caused by a direct H2Sattack of the bright metals within the engine,such as the oil cooler and bronze/ brassbushings or bearings. This direct H2S attackcan not be deterred by high TBN oils orcontrolled by oil analysis. There are variousdevices available to reduce H2S in the fuel gassuch as chemical active filters, reactive beds,and solutions. Most of these devices depletethe reactive chemicals, their performance

deteriorates, and they need servicing orreplacing.

Caterpillar recommends that even though afuel gas is scrubbed to a pipeline level of H2S,the precautions listed below should be takenfor high sulfur fuels to protect against thoseintervals of operation with high sulfur fuelwithout precautions can severely damage theengine.

• Maintain the jacket water outlettemperature between 96°C and 102°C(205°F and 215°F). Water and sulfur oxidesare formed during combustion and willcondense on cylinder walls at lowtemperature. The higher jackettemperature will minimize the amount ofcondensation.

• Maintain the temperature of the oil in thesump high enough to prevent water fromcondensing in the oil. Normally,maintaining the jacket water outlettemperature at a minimum of 96°C (205°F)will accomplish this. G3600 engines haveoutlet-controlled jacket water systemsavailable that operate at 110°C (230°F).

• Establish an oil analysis program to assureoil change periods are not extended beyondsafe limits and that other problems are notoverlooked. Caterpillar Dealers are capableof establishing and conducting suchprograms.

• Where it is possible to start the engine onsweet gas, bring the engine up to operatingtemperature on sweet gas, then switch tosour gas. Reverse the procedure whenshutting down the engine.

• Select a natural gas engine oil with a higherTBN, or select a natural gas engine oilspecifically formulated for use withalternate fuel gas. Use the same selectionmethod of this oil as specified in theprevious section. Oils with higher TBNvalues generally have higher levels ofsulfated ash. Ash can cause deposit buildupthat leads to valve, combustion chamber,and turbocharger damage. These depositscan potentially shorten engine life.

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• There is no known oil additive than canprotect the internal bright metal enginecomponents from H2S attack. A positivecrankcase ventilation has proven tosuccessfully reduce the H2S attack ofinternal engine components. Theventilation system should positively removethe fumes from the crankcase and allowfiltered air to enter the crankcase to dilutethe levels of H2S. Guidelines for installingand sizing a crankcase ventilation system iscontained in the Crankcase Ventilation A & I Guide.

Multi-Viscosity OilsThe operation of gas engines using multi-viscosity oils has been very limited. Resultsfrom these tests has indicated poor oilperformance as compared with single gradeoils relative to deposits.

For applications where continuous coldstarting is an absolute, single grade oil usedin combination with jacket water heatersand/or oil heaters are recommended.

Performance requirements for multi-viscosityoils in G3600 engines are the same as singlegrade oils. Multi-viscosity oils require asuccessful 7000 hour field trial as previouslydescribed for commercial oils. Field trial datafrom single grade oils using similar additivesdo not apply to multi-viscosity oils.

Synthetic OilsThe use of synthetic base stock oils is verylimited in Caterpillar gas engines because oftheir high cost. Performance requirementsfor synthetic oils in G3600 engines is thesame as single grade oils. Synthetic oilsrequire a successful 7000 hour field trial aspreviously described for commercial oils.

Lubricant ViscosityAll G3600 engines currently operate withSAE 40 oil. Other lubricant viscosities are notrecommended for use with G3600 engines.Oils other than SAE 40 require require asuccessful 7000 hour field trial as previouslydescribed for commercial oils.

Monitoring Lubricating OilQualityScheduled Oil Sampling (S•O•S)Caterpillar Dealers offer Scheduled OilSampling (S•O•S) as a means of determiningengine condition by analyzing lubricating oilfor wear particles. This program will analyzethe condition of your engines, indicateshortcomings in engine maintenance, showfirst signs of excessive wear, and help reducerepair costs. This program is not able topredict a fatigue or sudden failure. Caterpillarrecommendations for oil and oil changeperiods are published in service literature.Caterpillar does not recommend exceedingthe published oil change recommendationsunless the change intervals are established bya comprehensive maintenance managementprogram that includes oil condition analysis.

Lubrication Oil Condemning LimitsThe lubricating oil condemning limits weredeveloped from engine operating experienceand oil analysis. The limits provide guidelinesin determining the oil's useful life in theengine. Table 4 and 5 establishes the limitsfor oil service life.

Table 4.

Table 5.

Alternate Oil Analysis(additional test procedure for more data)

Viscosity(ASTM D445)

Total Base Number(TBN), (ASTM D2896)

Total Base Number(D664)

Total Acid Number(TAN) (D664)

3cSt increase from new oil

50% of original TBN

1.5 minimum

3.0 max or2.0 over new oil

LimitParameter

Scheduled Oil Sampling

Oxidation

Nitration

Sulfur Products

Water

Glycol

Wear Materials

100% as defined by S•O•S Program



0.5% maximum

0%

Trend Analysis

LimitParameter

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There have been occurrences where wearmetal levels indicate a TBN depletion but theTBN by ASTM D2896 has not shownsignificant depletion. Those occurrences havebeen with corrosive fuels such as landfill gas.Those customer have found that measuringthe TAN by ASTM D664 has given a bettercorrelation between wear metals protection .If there are wear metals with adequate TBNreserve by ASTM D2896 it is suggested to tryASTM 664.

Oil Change IntervalTo achieve maximum life from the engine oiland provide optimum protection for theinternal engine components, a Scheduled OilSampling program (S•O•S) must be used.Information is available through CaterpillarDealers. The program will determine oilchange intervals based on trend analysis andcondemning limits established for the engine.For an optimized program, oil samples must betaken every 250 operating hours through thelife of the engine.

The typical oil change interval for G3600engines is 5,000 operating hours forcontinuous operation on pipeline gas.However, due to the variety of applicationsand fuel qualities, the S•O•S must be used tomonitor the quality of the engine's oil. If theS•O•S results condemn the oil, then the oilmust be changed regardless of the operatinghours.

If oil change intervals are consistently lowerthan 5,000 hours, consult your CaterpillarDealer.

Oil ConsumptionOil consumption, along with fuel consumptionand maintenance information, can be used toestimate total operating cost. Oil consumptiondata may also be used to estimate the quantityof make-up oil required to accommodatemaintenance intervals. Many factors such asengine load, oil density, oil additive packagesand maintenance practices can affect oilconsumption.

The rate of oil consumption is called BSOC(brake specific oil consumption) and the unitof measure is grams per brake kilowatt hour(G/bkW-hr) or pounds per brake horsepower

hour (lb/bhp-hr). The following lists thetypical mid-life BSOC for engines operating at100% load factor.

Table 6.

Note: BSOC can typically vary by as much as+275% to minus 50%. Also, with very lowconsumptions, measurement methodsbecome difficult and number erratic.Therefore these values can only be used as aguide for make up oil requirements.

The following formula may be used toestimate oil consumption per hour:

L/hr = Engine bkW 3 Load Factor(%) 3 BSOC (g/bkW-hr)

Density of Oil**

gal/hr = Engine bhp 3 Load Factor(%) 3 BSOC (lb/bhp-hr)

Density of Oil**

**Typical engine oil has a density of 899 g/L(7.5 lb/gal)

EngineModel g/bkW-hr lb/bhp-hr g/bhp-hr

G3600 0.304 0.000521 0.227

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