DIESEL FUELS & DIESEL FUEL SYSTEMS

Diesel Fuels & Diesel Fuel SystemsApplication and Installation GuideFuel Transfer PumpsEngine DrivenCaterpillar engine-mounted transferpumps are positive displacementgear-type or piston-type pumps, witha limited prime and lift capability.The pump lifts the fuel bydisplacing air from the suction pipeto the discharge pipe. Low pressure(vacuum) develops in the suctionpipe and atmospheric pressure [101kPa (14.5 psi) at sea level] movesthe fuel into the vacuum. However,a perfect vacuum cannot bemaintained, and the maximum that apump can lift is about 5 m (17 ft).Caterpillar fuel pumps’ prime andlift capability is 3.7 m (12 ft), butpipe size, routing, and ambienttemperature will impact thiscapability.To determine if a pump canperform the required lift, thefollowing items must be considered.1. The vertical distance from thetank to the pump. The distanceshould be measured from theinlet pump port of the pump tothe bottom of the tank.2. Internal piping system lossesreduce the lifting capability. Thisis based primarily on the size andthe total length of the pipes, butalso includes the various fittingsand valves. As the temperaturegoes down the resistance goesup. The internal losses can beestimated using the PipingSystem Basic Information sectionof the Application & InstallationGuide.3. Elevation has a big impact onthe pump’s lifting capability. Asdescribed above the atmosphericpressure is helping the fuel intothe vacuum, but as the elevationgets greater, the atmosphericpressure decreases and theavailable lift will also decrease.Refer to Table 3.ElevationAtmospheric AvailablePressure Liftmeters feet kPa psi meters feet0 0 101.3 14.7 5.18 17.030.5 1000 98.0 14.2 4.87 16.061.0 2000 93.8 13.6 4.70 15.591.5 3000 90.3 13.1 4.57 15.0122.0 4000 86.9 12.6 4.40 14.5152.5 5000 83.4 12.1 4.26 14.0183.0 6000 80.7 11.7 4.10 13.5Table 3AuxiliaryAn auxiliary transfer pump isrequired when the service tank orday tank is located further away,horizontally or vertically, than theengine driven pump’s lift capability.Special considerations must begiven to the auxiliary transfer pumpwhen dealing with electronic enginesand the 3500 engine family. Thefuel flow for these engines isapproximately 2 to 3 times what isneeded for combustion. The auxiliarytransfer pump must be sized tomove the additional fuel.A primary filter must be installedbefore the auxiliary pump and asclose as possible to the tank.Page 20©2005 Caterpillar®All rights reserved.