3600 Marine EngineApplication andInstallation Guide

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Distillate Fuel● Heavy Fuel

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LEKM8463 8-98

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Engine Systems - Distillate Fuel Oil

Engine Fuel System DescriptionEngine Fuel Flow RatesBulk Storage And Delivery Systems

Day Tank (Distillate Fuel Service Tank)Emergency PumpSettling Tank

Fuel CleanlinessWater SeparationCentrifuges

Sample PointsSuction StrainerCentrifuge Supply PumpFuel Heater

Customer ConnectionsFlex ConnectionsFuel Lines

Pressure and Flow Monitoring

Fuel RecommendationsCetane NumberFilteringPour PointCloud PointSulfurViscosityAdditivesFuel Sulfur ContentSpecific Gravity

Fuel TemperatureFuel Coolers

Day Tank Sizing As A Heat SinkDay Tank Calculations

Fuel HeatersUseful Fuel Formulas and Data

Specific Gravity and DensityMass Flow RateSpecific HeatHeat Rejection

Burning Used Crankcase OilContinuous Blending

Reference Material

5

Engine Fuel SystemDescriptionRefer to Figures 1, 2, and 3 on pages 24,25 and 26 for schematics of the enginefuel system.

The standard primary fuel systemcomponents include an engine drivenfuel transfer pump, duplex media typefilters (secondary), unit fuel injectorsand a fuel pressure regulator. OptionalCaterpillar supplied fuel systemcomponents include flexible hoses, amanual fuel priming pump, and aduplex primary fuel strainer.

If used, the primary duplex fuel straineris installed remote from the engine inthe transfer pump suction line. Thestrainer has 178 micron (0.007 in.)cleanable elements. The manual primingpump is installed on the engine inparallel to the engine driven pump. Themanual pump helps to bleed air from thefuel piping before initial engineoperation and following enginemaintenance (filter element changes,injector replacement, etc.). It has asuction lift of 2.6 m (8.5 ft) and a flow of38 L (10 gal) per 115 revolutions. Themanual priming pump has a lift of 7.8 m(25.5 ft) if the fuel lines between the fueltank and the pump are full, as after afilter element change.

To avoid air suction into the fuel transferpump at low suction pressures and sealleakage at high suction pressures, thefuel pressure at the engine driventransfer pump at rated speed must begreater than -39 kPa (-5.7 psi) or lessthan 100 kPa (14.5 psi). If the manualpriming pump is used the suctionpressure must be less than 50 kPa (7.25 psi). The engine driven transferpump may be used for fuel with aviscosity up to 40 cSt at 50°C. Higherviscosity fuels require a fuel boostermodule to circulate and heat the fuelprior to engine operation (see the

HeavyFuel Oil section of this guide).

The engine driven transfer pumpdelivers fuel to the unit injectors via thesecondary fuel filters. The 5 micron(0.0002 in.) duplex filters are usuallyboth in service for normal operation,although one housing may be isolated ata time during operation for filterreplacement if required. Therecommended fuel delivery pressure tothe injectors is 414-690 kPa (60-100 psi)at rated speed.

The unit injector combines the functionsof pumping, metering and injecting intoa single unit. It is mounted in thecylinder head at the centerline of eachcylinder. External manifolds supply fuelfrom the transfer pump to the drilledpassages in the cylinder head,eliminating the need for high pressurefuel lines. A 100 micron (0.004 in.) edgetype filter within each injector preventscontaminants from entering the injectorduring maintenance. Fuel circulatesthrough the injectors and the portionthat is not used for combustion cools theinjectors and is returned to the fuel tankvia the pressure regulating valve. Forheavy fuel oil applications a specialcooling circuit is designed in the unitinjector to supply and circulate thecoolant through the injector tip (see theHeavy Fuel Oil section of this guide).

The fuel delivery pressure to theinjectors is controlled by adjusting thepressure regulating valve on site. Thevalve is a spring loaded variable orificetype mounted on the front right side ofthe engine, and it maintains adequateinjector supply pressure for all enginespeed and load ranges. The pressureregulator must be adjusted at theinstallation site. To provide 414-690 kPa(60-100 psi) fuel to the injectors, the fuelreturn line restriction must not exceed350 kPa (51 psi) at rated engine speed.

Engine Fuel Flow RatesRefer to the table on page 6 for 3600engine fuel flow rates and heatrejections at various engine speeds.

6

Bulk Storage andDelivery SystemsShipboard fuel systems must insure acontinuous supply of clean fuel to theengines. Bulk fuel is usually stored in alarge tank(s) and transferred to asmaller tank(s) (day or service tank)near the engine room by one of threemethods:

• Fuel flows by gravity from the ship’smain tank(s) to the service tanks. Theengine driven transfer pump takesfuel directly from the service tank.Fuel is normally returned from theengine through a deaeration tank back to the transfer pump inlet ordirectly back to the service tank.

• An electric driven transfer pump delivers fuel from the ship’s main tankto a settling tank. After allowing timefor settling of water and solids the fuel is transferred to the service tank.

• A fuel oil separator may be used totransfer fuel from the ship’s main or settling tank to the service tank.

Install vents on each tank to relieve airpressure created by filling and toprevent vacuum formation as fuel isconsumed. Water and sediment shouldbe periodically drained from each fueltank.

Seal piping and fittings to prevent air ordirt contamination. Air in the systemcauses hard starting, erratic engineoperation, and can also erode injectors.

Fuel lines can be black iron pipe, steelpipe or copper tubing. Galvanized,aluminum, or zinc-bearing alloy pipemust not be used.

3600 Engine Fuel Flow

Rated Speedrpm

Fuel Flow-L/min (gal/min) Fuel Heat RejectionWithout Injector

Tip Cooling, kW (Btu/min)to Engine from Engine

3606 1000 41.5 (11.0) 32.4 ( 8.6) 12.5 ( 712)900 38.0 (10.0) 30.0 ( 7.9) 11.0 ( 626)750 31.5 ( 8.3) 24.5 ( 6.5) 10.5 ( 598)720 30.0 ( 7.9) 23.6 ( 6.2) 10.0 ( 567)

3608 1000 41.5 (11.0) 30.0 ( 7.9) 16.7 ( 951)900 38.0 (10.0) 27.6 ( 7.3) 14.6 ( 831)750 31.5 ( 8.3) 22.6 ( 6.0) 14.0 ( 797)720 30.0 ( 7.9) 21.4 ( 5.6) 13.3 ( 757)

3612 1000 78.5 (20.7) 60.1 (15.9) 25.0 (1423)900 72.0 (19.0) 55.4 (14.6) 22.0 (1252)750 61.2 (16.2) 47.3 (12.5) 20.2 (1150)720 58.1 (15.3) 45.2 (11.9) 19.1 (1087)

3616 1000 78.5 (20.7) 55.2 (14.6) 33.3 (1895)900 72.0 (19.0) 51.1 (13.5) 29.3 (1668)750 61.2 (16.2) 43.2 (11.4) 26.9 (1531)720 58.1 (15.3) 41.2 (10.9) 25.4 (1446)

Maximum inlet restriction on pump = -39 kPa (-5.7 psi).Maximum return line restriction = 350 kPa (51 psi) at rated speed.

Day Tank (Distillate FuelService Tank)Day tanks are used in almost all marineapplications. The installation designmust consider engine mounted transferpump limitations. Total suction headmust not exceed 2.6 m (8.5 ft).

Locate tanks to avoid fuel levels higherthan the engine fuel injectors to preventfuel leakage into the cylinders due tostatic head when the engine is shutdown. If overhead mounting isunavoidable, include an open/closesolenoid valve in the supply line and a3.45 kPa (0.5 psi) check valve in thereturn line.

The delivery line carrying fuel to the fueltransfer pump and the return linecarrying excess fuel to the service tankshould be no smaller than the enginefittings. Larger fuel supply and returnlines ensure adequate flow if the fueltank feeds multiple engines over 9.14 m(30 ft) from the tank or temperatures arelow. The maximum inlet flow restrictionis -39 kPa (-5.7 psi) at rated speed.Caterpillar fuel pumps prime up to 2.6 m (8.5 ft) of suction lift, but pipe size,bends, and cold ambients modify thiscapability. Position fuel suction lines toremove fuel about 76 mm (3 in.) above

the tank bottom and near the tank endopposite the return line. Do not use jointcement affected by fuel or gasketedconnections. Flexible fuel lines must beinstalled at the engine fuel inlet andoutlet to accommodate engine motion.

The return line should enter the top ofthe tank without shutoff valves. Avoiddips so air passes freely and preventsvacuum in the fuel system. All returnfuel from the engine must be allowed todeaerate before being returned to theengine. The maximum return flowrestriction is 350 kPa (51 psi) at ratedspeed.

All engines add heat to the fuel as theengine operates. The day tank can besized to dissipate the added heat. If thisis not possible fuel coolers may berequired (see the section on FuelTemperature).

Figure 4 on page 27 shows a typicaldelivery system from the day tank to amain propulsion engine.

See Figure 5 for a recommended tankdesign. The rules and regulations forfuel tanks of the applicable marinesociety must be observed.

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Emergency PumpAn electric motor driven emergencypump may be required in some engineapplications for use as backup to theengine driven pump. This is generally amarine society requirement for singleengine propulsion applications.Recommended flow rates are shown inthe following table and will fulfill theminimum engine requirements at allrated speeds between 700 and 1000 rpm.

The emergency pump must deliver thestated flow of diesel fuel at 65°C (149°F)against a head of 500 kPa (73 psi)pressure. Adjust the fuel pressureregulator to 414-690 kPa (60-100 psi).

Fuel treatment systems should becapable of being maintained withoutinterruption in engine operation.

Settling Tank The settling tank should hold a 24 hourminimum supply of distillate fuel for thepropulsion engine, plus the normalexpected kilowatt load from the dieselgenerator sets. Refer to the typicalsettling tank design (Figure 14) in theHeavy Fuel Oil section of this guide.

A heating coil can be installed in thetank. It can be used as a standby heaterto bring the fuel to the proper centrifugetemperature. The coil should keep thedistillate fuel temperature approximately20°C (11°F) above the pour point. Fit theheating steam supply with an automatictemperature regulating valve to controlfuel tank temperature.

R

R

TO SLUDGE TANK

TO FUEL OIL TRANSFER PUMP

SLOPED BOTTOM

VALVES FITTED WITH REMOTE OPERATING GEAR (AS REQUIRED

BY CLASSIFICATION SOCIETY)

SLUDGE SPACE

STEAM BLOW-OUT

RETURN FROM DEAERATION TANK

OR ENGINE

OVERFLOW TO SETTLING TANKS

BAFFLE PLATE

MANHOLE

TO ENGINE TRANSFER PUMP SUCTION

R

LLA

LOCAL THERMOMETER

HLA

ANTI-SIPHON OPENING

VENT PIPE LED TO ATMOSPHERE AND FITTING WITH FLAME SCREEN AND DRIP PAN

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Figure 5

Typical Arrangement of Service Tank

Flow Rate L/min (gal/min)

Engine 3606 3608 3612 3616Fuel Pump 42 (11) 42 (11) 79 (21) 79 (21)

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Use screw type pumps to transfer fuelfrom the bunker tanks to the settlingtank. They minimize the possibility ofemulsifying water entrained in thedistillate fuel. The transfer pump shouldoperate automatically and fill thesettling tank in less than two hours.

The following pump characteristics areprovided for guidance:

• Operating pressure — to suitconditions of piping system

• Operating fluid temperature — 38°C(100°F)

• Viscosity for sizing the pump motor —500 cSt

Fuel CleanlinessClean fuel is essential. The final filtersare engine mounted and tested at thefactory and are never bypassed on anoperating engine. Optional factorysupplied duplex primary filters with 178 micron (.007 in.) cleanable meshscreens collect large debris prior to theengine transfer pump.

Water SeparationWith modern high output engines usinghigh injection pressure fuel pumps, it isextremely important to maintain waterand sediment levels at or below 0.1%.Depending on how the engines areapplied, water and sediment can collectin fuel tanks. Therefore, fuel meetingthe required specifications whendelivered to the site can exceed limitswhen used in the engine. Severalmethods can be used to remove excesswater and sediment:

• A water and sediment separator canbe installed in the supply line ahead ofthe transfer pump. The separator mustbe sized to the handle the fuel beingconsumed by the engines as well asfuel being returned to the tank.

• Coalescing filter systems workeffectively to remove sediment andwater. If the level in the day tank is not maintained at a consistent level,install them between the main tankand the day tank. If proper day tankoperation is maintained, a smaller

system can be used between themain tank and the day tank to cleanonly the fuel being burned. The filterscan plug and careful attention must be given to fuel pressure levels at the injectors to guard againstmisfiring.

• A centrifuge system can be used,particularly if the fuel qualityconsistently exceeds the defined limitsspecified herein.

CentrifugesClean distillate fuel with a separatecentrifuge system from those dedicatedfor heavy fuel on the same ship (seeFigure 6 on page 28 of this section).Even though the main propulsionengines may be arranged for heavy fuel,size the distillate fuel treatment plant tosuit both the main engines and the shipservice generator sets. Two transferpumps, two centrifuges and heaters arenormally used.

Use an automatic self cleaningcentrifuge. Consult the centrifugemanufacturer to size the flow.

The fuel centrifuge piping system mustallow one of the centrifuges to act as astandby. The required flow rate can beapproximated as follows:

P x b x 24 x 1.15Q = {_______________}R x t

Where:Q = Flow required, L/hrP = Total Engine Output, kWb = Fuel Consumption, g/kW-hrR = Density of fuel, kg/m3

t = Daily separating time inautomatic operation: 23 hr

or:

P x be x 24 x 1.15Q = {________________}R x t

Where:Q = Flow required, gal/hrP = Total engine output, bhp be = Specific fuel consumption,

lb/bhp-hrR = Density of fuel, lb/galt = Daily separating time in

automatic operation: 23 hr

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Note:• The centrifuge manufacturer should

assist in the final centrifuge selection.• The centrifuge flow has been

increased by 15% as a safety factorfor operational tolerances.

Centrifuge seal water and control airrequirements must be specified by thecentrifuge manufacturer.

Sample PointsThe centrifuge operating efficiency ischecked by drawing samples from bothsides of the centrifuge. Arrange thepoints as shown in Figure 15 on page 48of the Heavy Fuel Oil section.

Suction StrainerInstall a simplex strainer ahead of thecentrifuge supply pump and use astainless steel basket with perforationssized to protect the pump (0.8 mm (1/32 in.)). The strainer body is normallymanufactured from cast iron or bronze.

Centrifuge Supply PumpMount an electric motor driven supplypump separately from the centrifugeand size for the centrifuge flow. Thefollowing pump characteristics areprovided for guidance:• Operating pressure - to suit

conditions of piping system• Operating fluid temperature - 38°C

(100°F)• Viscosity for sizing pump motor -

500 cSt

Fuel HeaterThe heater is sized using the pumpcapacity and the temperature riserequired between the settling tank andthe final centrifuge. The heater shouldbe thermostatically controlled andselected to maintain fuel temperature tothe centrifuge within ± 2°C (± 4°F). Themaximum preheating temperature fordistillate fuel is 40° to 50°C (104° to122°F).

Customer Connections

Flex ConnectionsConnections to the engine must beflexible hose located at the engine inletand outlet. Do not attach rigid fuel lines.The factory provided flex connectionscan be oriented to take maximumadvantage of multiple direction flexing.

Fuel LinesBypass (return) fuel leaving the enginepressure regulator should be returned tothe engine day tank. Any fuel returneddirectly to the transfer pump inlet mustbe routed through a deaerator.

The final installation must behydrostatically tested to at least 1.5times normal working pressure or toapplicable marine society requirements,whichever is greater.

After fabrication and testing, steel pipingmust be removed and chemically cleaned(pickled) to remove mill scale, dirt, etc.Wash piping with suitable solvent anddry thoroughly. Coat the inside of pipingwith oil prior to final assembly.

Pressure and Flow MonitoringEngine fuel lines have pressurevariations due to injector spill pulses.Monitoring devices must includedampers or orifices in the lines tominimize pulse effects and obtainaccurate readings. Caterpillar suppliedgauges have proper dampingincorporated in the hardware.

Fuel SupplyFuel Return

3606/360822 mm (7/8 in.)22 mm (7/8 in.)

3612/361628 mm (1-1/8 in.)22 mm (7/8 in.)

Engine Fuel Piping (Inside Diameter)

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Fuel RecommendationsCaterpillar 3600 engines are capable ofburning a wide range of distillate fuels.Also see the Heavy Fuel Oil section ofthis guide.

The fuels recommended for 3600 enginesare normally No. 2-D diesel fuel and No. 2 fuel oil. No. 1 grades and ISO-F-DMB fuels are also acceptable. Otherfuel types may be used when economicsor fuel availability dictate.

Consider the following fuelcharacteristics when procuring fuel:

Cetane NumberThe minimum cetane number requiredfor average starting conditions is 40. Ahigher cetane value may be required forhigh altitude operation or cold weatherstarting.

FilteringFuels should have no more than 0.1%sediment and water. Storage of fuel forextended periods of time can cause fueloxidation and formation of solids,leading to filtration problems.

Pour PointThe pour point of the fuel should be atleast 6°C (10°F) below the lowestexpected starting and operatingtemperatures. The lower pour point ofNo. 1 or No. 1-D fuel may be necessaryin cold weather.

Cloud PointThe cloud point should be below thelowest expected ambient operatingtemperature. This prevents fuel filterelements plugging with wax crystals.

SulfurFuels containing 0.5% or less sulfur maybe used with normal crankcase oil drainintervals using API CF performance oils.With sulfur above the 0.5% level, useAPI CF oil with an ASTM D-2896minimum total base number (TBN) of 10times the fuel sulfur for normal oil drainintervals. See the guide section onLubricating Oil for further details.

ViscosityFuel viscosity is important forlubrication of fuel system componentsand fuel atomization. The minimumallowable viscosity at the injectors is 1.4 cSt.

AdditivesFuel additives are generally notrecommended. Cetane improvers can beused as necessary. Biocides may beneeded to eliminate microorganismgrowth in storage tanks. Treatment forentrained water may also be necessaryin cold conditions. Consult the fuelsupplier about the use of additives toprevent incompatibility with additivesalready in the fuel.

Fuel Sulfur ContentThe percentage of sulfur in fuel willaffect engine oil recommendations. Fuelsulfur is chemically changed duringcombustion to form both sulfurous andsulfuric acid. The acids chemicallyattack metal surfaces and causecorrosive wear.

Certain additives used in lubricating oilscontain alkaline compounds formulatedto neutralize acids. The measure ofreserve alkalinity is total base number(TBN). Required TBN values areessential to neutralize acids andminimize corrosive wear.

Distillate Fuel Recommendations

Requirements*35% Maximum0.02% Weight Maximum40 MinimumNot above lowestexpected ambienttemperature30 Minimum and 45 Maximum6°C (10°F) belowambient temperature0.5% Maximum(See Sulfur Topic)20.0 cSt Maximum1.4 cSt Minimum0.1% Maximum

SpecificationsAromantics (ASTM D1319)Ash (ASTM D482)Cetane Number (ASTM D613)Cloud Point (ASTM D97)

Gravity API (ASTM D287)

Pour Point (ASTM D97)

Sulfur(ASTM D2788, D3605, or D1552)Viscosity, Kinematic @ 38°C (100°F) (ASTM D445)Water & Sediment (ASTM D1796)

*As delivered to fuel system.

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The TBN recommendation for an oil isdependent on the amount of sulfur in thefuel used. For 3600 engines running ondistillate fuel oil, the minimum new oilTBN (by ASTM D 2896) must be 10times the sulfur percent by weight in thefuel, with a minimum TBN of 5regardless of the sulfur content (seeFigure 7).

In most oil formulations the TBN is afunction of the ash bearing additives inthe oil. Excessive amounts of ashbearing additives can lead to excessive

piston deposits and loss of oil control.Therefore, excessively high TBN or highash oils should not be used with 3600engines running on distillate fuel.Successful operation of 3600 engines ondistillate fuel has generally beenobtained with new oil TBN levelsbetween 10 and 15. See the guide sectionon Lubricating Oil for more information.

Periodically request fuel sulfurinformation from the fuel supplier. Fuelsulfur content can change with eachdelivery.

NEW OIL TBN FOR DISTILLATE FUEL

USED OIL TBN LIMIT

0 .5 1 1.5 2 2.5 3

17

15

13

11

9

7

5

3

1

FUEL SULFUR — % WEIGHT

TB

N —

AS

TM

D 2

896

TBN VS FUEL SULFUR FOR 3600 SERIES ENGINES ON DISTILLATE FUEL

NOTE: OPERATION AT FUEL SULFUR LEVELS OVER 1.5% MAY REQUIRE SHORTENED OIL CHANGE PERIODS TO MAINTAIN ADEQUATE WEAR PROTECTION.

Figure 7

TBN vs Fuel Sulfur for 3600 Engines on Distillate Fuel

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Specific GravityFuel rack settings are based on 35° API(specific gravity) fuel. Fuel oil with ahigher API (lower specific gravity)number reduces power output unless therack setting is corrected. When usingheavier fuels (lower API number), acorrected rack setting prevents poweroutput above the approved rating. TheCaterpillar dealer will correct the racksetting for non-standard fuels.

Fuel TemperatureThe fuel temperature supplied to theengine can affect unit injector life andmaximum power capability. Reducedlubrication capability as a result of hightemperature/low viscosity fuel mayresult in plunger scuffing. The minimumallowable viscosity at the injectors is 1.4 cSt. A maximum fuel temperaturelimit of 72°C (162°F) to the unit injectors,regardless of fuel viscosity, preventscoking or gumming of the injectors. Themaximum fuel viscosity to the unitinjectors of 20 cSt prevents overpressuredamage to the injectors.

The engines are power set at the factorywith 30 ± 3°C (86 ± 5°F) fuel to theengine transfer pump. Higher fueltemperatures reduce maximum powercapability. The fuel stop power reductionis 1% for each 5.6°C (10°F) fuel supplytemperature increase above 30°C. If theengine is operating below the fuel stoplimit, the governor will add fuel asrequired to maintain the requiredengine speed and power.

Day tank sizing is critical to maintainthe desired fuel supply temperature. Fuelcoolers may be required.

Fuel CoolersFuel coolers are site specific and sized tohandle fuel heat not dissipated by theday tank. The cooler must be located onthe return circuit with a three waytemperature regulating valve to controlfuel return temperature to the servicetank (see Figure 4). Submit the coolerdesign and materials to the appropriateclassification society for approval.

The suggested material for a shell andtube type heat exchanger is:

• Shell Red brass

• Heads Cast iron

• Tubes Copper

• Tube sheets Brass

• Baffles Brass

A plate type heat exchanger may also beused with titanium plates for sea watercooling or stainless steel plates for freshwater cooling.

Day Tank Sizing as a Heat SinkDay tank sizing is critical when fuel tothe engine is from a day tank without afuel cooler. The supply temperaturemust be within specified limits forinjector life and maximum powercapability.

Day tank temperatures are impacted by:

• Day tank wetted surface area(including tank bottom)

• Engine(s) fuel consumption rate

• Day tank replenishing level

• Storage tank fuel temperature

• Ambient temperature

• Spaces contiguous to the day tank(void tanks, cofferdams, vessel shellplating, etc.)

• Return fuel temperature

Tank temperature calculation areperformed in five [5] steps. The firstdetermines the fuel mass in the tank ateach time interval. The second step isbased on a fuel mix temperatureresulting from the engine driventransfer pump flow rate to the engineand the return flow rate to the day tank.The third step determines the day tankfuel height for each incremental timeelement. Typically, the calculations willbe based upon a 30-60 minute iterativetime function. The end point for thecalculation is assumed to be when theday tank is refilled. The fourth stepapproximates the heat transfer from thetank to the surrounding environmentdue to the temperature differencebetween the fuel mix temperature andthe ambient temperature. Thisconvective heat transfer thendetermines the resultant tanktemperature. The fifth step evaluatesthe impact of the final fuel supplytemperature on the engine’s maximumpower capability.

The included example calculationsshould only be used to provide generalguidance. If the day tank size ismarginal use a fuel cooler.

To simplify the following calculations, itis assumed the day tank walls aresurrounded by free moving air. If thetank walls are contiguous to the shellplating, heat transfer from the day tankwill be enhanced. Conversely, if the daytank is bounded by void spaces andcofferdams, heat rejection from the daytank will be retarded. Typically, mostday tanks are located with variouscombinations of the preceding boundaryelements. The individual performing theevaluation must be familiar with theinstallation as well as the fundamentalengineering concepts of the formulasused in the calculations.

Day Tank CalculationsThe following information is required toperform the calculations:• Engine model• Engine developed power (MCR or CSR) • Engine speed

• Brake specific fuel consumption (bsfc)• Initial day tank fuel temperature• Storage tank fuel temperature

(Make-up)• Ambient air temperature• Day tank length, width, and height• Typical full day tank fuel height

(assume 95% of tank capacity)• Engine fuel transfer pump flow rate

(see page 6 of this section)• Fuel heat rejection from the engine

(see page 6 of this section)• Incremental time element

Day Tank Thermal CapacityCalculationExample:• Application: Single main engine• Engine Model: 3612• Rated Power: 4640 bhp (CSR)• Rated Speed: 900 rpm• bsfc: 0.326 lb/bhp-hr• Initial Day Tank Fuel Temperature =

85°F• Storage Tank Temperature = 85°F• Ambient Air Temperature = 95°F• Day Tank Dimensions:

Length (L) = 12 ft.Width (W) = 8 ft.Height (H) = 8.42 ft.

• Fuel Height (@ 95% of total Capacity)(H) = 8 ft.

• Engine Fuel Oil Transfer Pump FlowRate (qxfer) = 19.0 gpm

• Heat rejection from engine to fuel oil (Q) = 1252 Btu/min

• Incremental time element, (t) = 60 min.

Assume that the day tank will bereplenished from the vessel’sstorage tanks when the day tanklevel falls to approximately 50-55%of normal operating capacity.

Some of the data above must beconverted to other units prior tobeginning calculations. The followingformulas can be used:a) Engine Driven Transfer Pump Mass

Flow Rate = Mxfer (lb/min)Assume: #2 DO with an APIgravity of 35 (7.1 lb/gal)

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15

Mxfer = qxfer x 7.1 lb/gal = 19.0 gpm x7.1 lb/gal = 134.9 lb/minb) Engine burn rate under full load

conditions1) Burn rate (gpm) =

bsfc x bhp x 1 Hr._____________________Fuel density x 60 min.

0.326 lb/bhp - hr x 4640 bhp x 1 hr. = _________________________________7.1 lb/gal. x 60 min.

= 3.55 gpm

2) Fuel mass flow burn rate =MBR (lb/min)= 3.55 gpm x 7.1 lb/gal= 25.21 lb/min

c) Engine fuel return rate under fullload conditions:

1) Fuel return flow rate = qrtn (gal/min)= Supply rate - burn rate= 19.0 gpm - 3.55 gpm= 15.45 gpm

2) Fuel return mass flow rate = MRTN(lb/min)= 15.45 gpm x 7.1 lb/gal= 109.70 lb/min

d) ∆ TENG of fuel = (T supply - T rtn)

Q∆ TENG = ______________MRTN x cp

1252 Btu/min= ____________________________

(109.70 lb/min x 0.5 Btu/lb-°F)

= 22.83°Fe) 95% Capacity of Diesel Oil Day Tank,

(lb)Weight density (p) for #2diesel oil = 52.42 lb/ft3

MDT = L x W x H x pDO= 12 ft x 8 ft x 8 ft x 52.42 lb/ft3

= 40258.6 lb.

Step 1Calculate the fuel mass in the day tankat specific time intervals:Day Tank Fuel Quantity = MDT - (MBR x t)

Where:MDT = Day tank contents at a specific

time step (lb)MBR = Engine fuel consumption (lb/min)t = Incremental time step (min)

Assume the day tank is replenished at55% of initial quantity of fuel. Prepare atable of volumes as shown below for ourexample.

0 40258.6 100.060 38746.0 96.2

120 37233.4 92.5180 35720.8 88.7240 34208.2 85.0300 32695.6 81.2360 31183.0 77.5420 29670.4 73.7480 28157.8 69.9540 26645.2 66.2600 25132.6 62.4660 23620.0 58.7720 22107.4 54.9

Refill 40258.6 100.0

IncrementalTime (Min)

Tank FuelQuantity (lb)

Capacity(%)

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Step 2Calculate the fuel oil mix temperature (Tmix):

[ (MDT - [(Mxfer x t)]) TDT + (MRTN x t) x (TDT + ∆ TENG)](t -1) (t -1) (t -1)

______________________________________________________________________________

MDT - (MBR x t)(t -1)

Where:MDT = Day tank contents at a

specific time step (lb)Mxfer = Engine transfer pump mass

flow rate (lb/min)t = Incremental time step (min)TDT = Day tank temperature for(t -1)

previous time step orstarting temperature (°F)

MRTN = Engine return mass flowrate (lb/min)

∆T ENG = Fuel temperature riseacross the engine (°F)

MBR = Engine fuel consumption(lb/min)

Values for the example calculation:

MDT = Day tank contents from(t -1)previous time step (lb)

Mxfer = 134.9 lb/mint = 60 min.TDT = Initial day tank temperature(t -1)

is used for first iteration, 85°F MRTN = 109.70 lb/min∆TENG = 22.83°FMBR = 25.21 lb/min

[(40258.6 - (134.9) (60)) (85)] + [(109.70) (60) (85 + 22.83)]Tmix = _____________________________________________________

[40258.6 - (25.21) (60)]= 88.9°F @ t = 60 min.

This calculation is repeated for each increment (t). Prepare a summary table as shown below for each increment (t).

0 85.060 88.9

120 92.9180 97.1240 101.5300 106.1360 110.9420 116.0480 121.3540 126.9600 132.9660 139.3720 146.1

Refill

Incremental Time (Min)

MixTemperature (°F)

17

Step 3Calculate the height of fuel contained inthe day tank at t = incremental timestep. Prepare a summary table for eachtime increment (t).

MDTH =____________ p x L x W

Where:H = Height of fuel in the tankMDT = Fuel contained in the day tank

at each incremental time stepp = Weight density of #2 DO

(52.42 lb/ft3)L = Length of day tank (12 ft)W = Width of day tank (8 ft)

Where:QTK = Heat transfer to/fromatmosphere (Btu)

This considers 6mm (0.25 in.) steel plateforming the tank boundaries, and thefilm coefficient for air and oil. The airside film coefficient is predominant whencompared to the oil side film. The tankthickness has a negligible effect.

U = Coefficient of heat transfer,(0.0424 Btu/min •ft2 •°F)

L = Day tank length (ft)W = Day tank width (ft)TAMB = Ambient temperature (°F)TMIX = Mix temperature of return fuel

and fuel in tank (°F)TDT = Day tank temperature

resulting from heat transferto/from day tank (°F)

t = Incremental time step (min)H = Fuel height for specific time

step (ft)

b) Temperature change in the day tankresulting from heat to/from day tank:

Q TK∆TDT = _____________MDT x Cp

Where:∆TDT = Temperature change of fuel in

the day tank (°F)

QTK = Heat transfer to/fromatmosphere (Btu)

MDT = Mass of fuel in day tank (lb)

cp = Specific heat of #2 MDO = 0.5 Btu/lb •°F

c) Day tank temperature resulting fromheat transfer to/from day tank:

TDT = TMIX + ∆TDT

Incremental Time (min) Height (ft)

060

120180240300360420480540600660720

Refill

8.0 7.77.47.16.86.56.25.95.65.35.04.74.48.0

Step 4Calculate the heat transferred between the fuel in the day tank and the atmosphere,the ∆T of the fuel in the day tank due to the heat transfer, and the resulting fuel daytank temperature.

a) Heat transferred between the day tank and the atmosphere:

(TMIX + TDT)QTK = [U x [ (H x (2L + 2W) + (L x W) ] x [ T AMB - _______________ ]] x t

2

18

Where:TDT = Day tank temperature (°F)

TMIX = Mix temperature of return fueland tank fuel (°F)

∆TDT = Temperature change of daytank (°F)

These three calculations areinterdependent in nature. First, QTKis determined for the first incrementaltime step. The resulting value for QTKis then used to compute the ∆TDT. ∆TDT is then used to determine TTK.This process is then repeated for eachincremental time step.

Example a):QTK = [U [ H x (2L + 2W ) + (L x W)] x [ TAMB - (TMIX+ TDT)]] x t____________

2QTK = 0.0424 x [7.7 (40) + 96 ] x [ 95 - (88.9 + 85)] x 60_________

2= 8283.6 Btu

Example b):QTK∆TDT =____________

MDT x cp

8283.6 Btu=___________________________(38746.0 lb) (0.5 Btu/lb °F)

= 0.43 °F (From atmosphere to daytank)

Example c):TDT = TMIX + ∆TDT

= 88.9 °F + 0.43 °F= 89.3 °F

This series of calculations is thenrepeated for the subsequent incrementaltime steps.

Prepare a summary table for each timeincrement (t).

IncrementalTime(min)

Heat Rejectionto/from Day Tank

(Btu)

Temperature Chg.in Day Tank

(°F)

Day Tank Temperature

(°F)

0 - - 85.060 8283.6 0.43 89.3

120 4069.7 0.22 93.2180 -4.0 0.00 97.1240 -4022.0 -0.24 101.3300 -7966.3 -0.49 105.6360 -11818.7 -0.76 110.2420 -15561.4 -1.05 114.9480 -19257.8 -1.37 120.0540 -22802.6 -1.71 125.2600 -26253.3 -2.09 130.8660 -29655.5 -2.51 136.8720 -32973.6 -2.98 143.1

Refill - - 116.9

19

The last part in Step 4 determines the day tank temperature after refilling (TDT ):refill

[ (MDT - MDT ) x TMUF] + (MDT x TTK )full tn tn nTDT = ____________________________________________________refill

MDTfull

Where:MDT = Capacity of day tank, (lb)

full

MDT = Fuel in day tank prior to refilling, (lb)tn

TMUF = Temperature of make-up fuel, (°F)

TTK = Temperature of tank fuel prior to refilling, (°F)n

Example:[(40258.6 - 22107.4) x 85] + (22107.4 x 143.1)TDT = ____________________________________________

refill 40258.6 lb= 116.9°F

Step 5The last step calculates the maximumpower capability of the engine at theresultant day tank temperature for eachtime interval. A summary table for eachincrement (t) is also prepared:

Note: The engines are power set at thefactory with 30 ± 3°C (86 ± 5°F) fuel tothe engine transfer pump. Higher fueltemperatures reduce maximum powercapability. The fuel stop power reductionis 1% for each 5.6°C (10° F) fuel supplytemperature increase above 30°C. If theengine is operating below the fuel stoplimit, the governor will add fuel asrequired to maintain the required enginespeed and power.

(TDT - Tref ) 1Pcorr = P rated x (1 - [___________ x _____] )10°F 100

Where:

Pcorr = Corrected Engine Power, bhp

Prated = Rated bhp

Tref = 86° (Power setting)

TDT = Actual day tank fueltemperature, °F

Example:For t = 60, the corrected power of the

engine is:PCORR =

[ (89.3°F - 86°F) x 1 ] 4640 bhp x (1 - ___________________ )(10°F) (100)

= 4625 bhp

20

ConclusionThe previous calculations indicate daytank fuel temperatures can have aneffect on the maximum power capabilityof the engine. The example was basedupon a fixed pitch propeller application.Typically, a fixed pitch propeller isselected and sized to absorb 85-90% ofthe engine's name plate rating. In thisexample, this would equate to 3950-4175 bhp. The lowest calculatedcorrected power was determined to be4375 bhp. This would leave a 5-10%power margin and vessel performancewould not be affected.

While vessel performance may not beaffected in this example, the maximumfuel temperature of 143.1°F will put thefuel viscosity near or below theminimum allowable viscosity of 1.4 cStat the injectors depending on the type ofdistillate fuel being used. In addition,the temperature of the fuel in the tank

after refill is now 116.9°F instead of 85°Fas used at the beginning of the iteration.Therefore, continued operation at fullload on this fuel tank would cause thefuel temperature to rise even higherthan the maximum temperature shownin this iteration. To protect the fuelinjectors a fuel cooler should be used inthis application, despite the fact thatavailable engine power is stillacceptable.

Aside from the impact on engineperformance, maximum fuel tanktemperatures are also established byvarious marine classification societiesand regulatory bodies. Their interest isbased upon the increased risks of firethat results from elevated fueltemperatures.

Fuel HeatersCold weather can form wax crystals inNo. 1 or No. 2 diesel fuel if temperaturesgo below the cloud point. Small amountsof heat added to the fuel before thefilters can prevent clogging problemsdue to wax. At temperatures below thecloud point, fuel will flow throughpumps and lines but not filters. Attemperatures below the pour point, fuelwill not flow in lines or pumps. The useof fuel with a pour point above theminimum expected ambienttemperature is not recommended. Fuelheaters will often solve cloud pointproblems but not pour point problemsunless applied to the entire fuel storagevolume.

IncrementalTime (min)

Day Tank Temp. (°F)

Corrected EnginePower (bhp)

0 85.0 -60 89.3 4625120 93.2 4607180 97.1 4588240 101.3 4569300 105.6 4549360 110.2 4528420 114.9 4506480 120.0 4482540 125.2 4458600 130.8 4432660 136.8 4405720 143.1 4375Refill 116.9 4497

21

The following are several suggestions forapplying fuel heaters:

• Use fuel heaters when the ambienttemperature is below the fuel cloudpoint. Many types of heaters can beused. Heat the fuel before the firstfilter in the fuel system. Do not usefuel heaters when the ambienttemperature exceeds 15°C (60°F). Themaximum fuel temperature at theoutlet of the fuel heater must neverexceed 72°C (162°F).

• Use heaters capable of handling themaximum fuel flow of the engine. Therestriction created must not exceedthe maximum allowable.

• Coolant may be taken from taps onthe engine when using the engine as

a heat source. Care must be taken toassure that coolant shunting to onesystem does not adversely affectanother system, and that both haveadequate flow.

Caution: Failed water sourced fuelheaters can introduce excessive waterinto the engine fuel system and causeinjector failure. Maintenanceresponsibility of this type of heater mustbe clearly defined.

When fuel heaters are used in ambienttemperatures below 0°C (32°F), start theengine and run at low idle until theengine temperature rises slightly. Thisallows heat transfer to the fuel beforehigh fuel flow rates at high power outputoccur, reducing fuel filter wax plugging.

22

Useful Fuel Formulas and DataThe following information can be useful in sizing fuel coolers and heaters:

Specific Gravity (SG) and DensityAPI Gravity = (141.5/SG) - 131.5SG = 141.5/(API Gravity + 131.5)SG = Density__________

998 kg/m3

Density (kg/m3) = SG x 998 kg/m3

Density (lbm/gal) = SG x 998 kg/m3 1 lbm/ft3 1 ft3x ___________ x ________

16.02 kg/m3 7.48 gal

Mass Flow Rate•M (kg/sec) = Density (kg/m3) x

1 m3

xFlow Rate (L/min)_____ __________________

1000 L 60 (sec/min)

•M (lbm/min) = Density (lbm/gal) x Flow Rate (gal/min)

Specific Heat (cp)

The following table shows typical specific heat values for two different API gravity fuelsin Btu/lbm-°F:

1 Btu/lbm-°F = 4.186 kJ/kg-°C

Heat Rejection•

Q (kW) = M (kg/sec) x cp (kJ/kg-°C) x ∆T (°C)

•Q (Btu/min) = M (lbm/min) x cp (Btu/lbm-°F) x ∆T (°F)

100°F 140°F 180°F 200°F 240°F

API Gravity (38°C) (60°C) (82°C) (93°C) (115°C)

30 0.463 0.482 0.501 0.511 0.530

40 0.477 0.497 0.516 0.526 0.546

23

Burning Used Crankcase OilWith legislation and ecologicalpressures, it is becoming increasinglydifficult to dispose of used oil. Burning ofused crankcase oil in 3600 engines isnot recommended due to thedetrimental effects on exhaustemissions. However, if ancillary methodsof reducing exhaust emissions toacceptable limits are used, or ifemissions are not a problem, burningcrankcase oil in 3600 engines is possiblewith these guidelines:

• Only diesel engine crankcase oils canbe mixed with the diesel engine fuelsupply. The ratio of used oil to fuelmust not exceed 5%. Prematurefilter plugging will occur at higher ratios. Under no circumstances should gasoline engine crankcaseoil, transmission oils, specialhydraulic oils not covered byCaterpillar recommendations,greases, cleaning solvents, etc., bemixed with the diesel fuel. Do notuse crankcase oils containing wateror antifreeze from engine coolantleaks or from poor storage practices.

• Adequate mixing is essential. Lube oiland fuel oil, once mixed, will combineand not separate. Mix used crankcaseoil with an equal amount of fuel,filter, and then add the 50-50 blend tothe supply tank before new fuel isadded. This procedure will normallyprovide sufficient mixing. Failure toachieve adequate mixing will resultin premature filter plugging byslugs of undiluted lube oil.

• Filter or centrifuge used oil prior toputting it in the fuel tank to preventpremature fuel filter plugging oraccelerated wear or plugging of fuel system parts. Soot, dirt, metal,and residue particles larger than 5 microns (.0002 in.) must be removed.

Caution: Diesel fuel day tank sightglasses may blacken. Ash content of thelube oil in the fuel may also cause moreaccumulation of turbocharger and valvedeposits.

Continuous BlendingIf the installation warrants, usedlubricating oil can be blended and usedin the engine in a continuous manner.The normal method uses a centrifugemodule similar to Figure 8. Thefollowing information describes thesystem:

Centrifuge No. 1Engine crankcase oil is continuouslycentrifuged except when the clean wasteoil tank is low, at which time the dirtywaste oil is centrifuged and directed tothe clean waste oil tank.

Centrifuge No. 2Distillate fuel/oil mixture daytank iscontinually centrifuged.

Metering PumpAdds up to 5% clean waste oil to thedistillate fuel (from the main supplytank) when the daytank low level switchcalls for more fuel.

Static MixerRuns when the metering pump is on toinsure a proper homogeneous mixture ofthe fuel and clean waste oil.

The centrifuge module is electronicallycontrolled and includes the componentswithin the dotted line. Size the systemfor appropriate fuel delivery.

Reference MaterialSEHS9031 Special Instructions -

Storage RecommendationsSEBD0717 Diesel Fuel and Your EngineSEBD0640 Oil and Your EngineLEKQ4219 EDS 60.1 – Fuel

Recommendations forCaterpillar Diesel Engines

24

Figure 1

FUEL SUPPLY

15

FUEL RETURN

141312

11

10

9

8

7

12 3 4 5

6

16

3606 and 3608 EnginesFuel Flow Schematic

1. Fuel Filter Housings2. Fuel Inlet Line3. Unit Injector4. Fuel Outlet Line5. Fuel Return Manifold6. Fuel Supply Manifold7. Check Valve8. Fuel Filter Change Valve

9. Check Valve10. Fuel Pressure Control Valve11. Fuel Supply Line12. Check Valve13. Fuel Transfer Pump14. Check Valve15. Fuel Priming Pump16. Emergency Fuel Connection

25

2 31 4

8

9

15141312

11

10

7

6

5

FUEL SUPPLY

FUEL RETURN

16

Figure 2

3612 and 3616 EnginesFuel Flow Schematic

1. Fuel Filter Housings2. Fuel Outlet Line3. Unit Injector4. Fuel Inlet Line5. Check Valve6. Fuel Filter Change Valve7. Check Valve8. Fuel Supply Manifold

9. Fuel Return Manifold10. Fuel Pressure Control Valve11. Fuel Supply Line12. Check Valve13. Fuel Transfer Pump14. Check Valve15. Fuel Priming Pump16. Emergency Fuel Connection

26

CHECKVALVE

SECONDARYFUEL FILTER

ELEMENTSCHECKVALVE

CHECKVALVE

FILTERCHANGE VALVE

SECONDARYFUEL FILTERELEMENTS

PRESSURERELIEF VALVE(FUEL PUMP)

MAINFUELPUMP

HANDPRIMING

PUMP

PRIMARYFUEL FILTER

MAIN FUELTANK

PRESSUREREGULATING VALVE

(RETURN FUEL)

UNITINJECTOR

CHECKVALVE

EMERGENCYFUEL INLET

(IF REQUIRED)

Figure 3

Fuel System Schematic

27

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29

CENTRIFUGE #1 STATIC MIXER

METERING PUMP

CENTRIFUGE#2

TRANSFER PUMP

FROM SUMP

ENGINE OIL TO SUMP

TO ENGINE

FROM ENGINE

FUEL DAY TANK

RECIRCULATION PUMP

DIRTY WASTE OIL

CLEAN WASTE OIL

Centrifuge Module Schematic For Burning Used Crankcase Oil

(Continuous Blending Method)

FROM DISTILLATE FUEL STORAGE TANK

Figure 8

Centrifuge Module SchematicFor Burning Used Crankcase Oil(Continuous Blending Method)