
SEBU8219-01 33
Product Information Section
Model Views and Specifications
The fuel transf
er pump requires a specific minimum
Net Positive Suction Head Available (NPSHA) to
properly operate. The NPSHA can be estimated
by adding the s
tatic suction head and the dynamic
restrictions that are in the system’s piping that is
external to the connection for the power module fuel
supply.
The static suction head is the pressure difference
between the f
uel connection of the power module
and the fuel level in the fuel supply tank. The static
suction head pressure is considered negative if the
fuel connec
tion of the power module is above the fuel
level in the fuel supply tank. The static suction head
pressure is considered positive if the fuel connection
of the power
module is below the fuel level in the fuel
supply tank.
If the stati
c suction head pressure difference is
negative, determine the NPSHA by subtracting the
negative static suction head pressure value from
the extern
al restriction allowance value that is g iven
below. If the static suction head pressure difference
is positive, then determine the NPSHA by adding
the posit
ive static suction head pressure value
to the external restriction allowance value that is
given below. Finally, subtract the pressure that is
lost to dy
namic restrictions in the piping in order
to determine a final value for NPSHA. For proper
system operation, the final value for NPSHA must
be great
er than zero.
Note: A chart that shows the relative resistance
of valve
s and pipe fittings to the flow of fluids is
provided in Caterpillar Electric Power Application
and Installation Guide, LEBX0030, “Fuel Systems”.
All pip
ing should be a minimum of 1.5 inches in
diameter. This size of piping will optimize the velocity
friction losses for the system.
The power module will have an Onboard
Import/Export Fuel Transfer system. The system is
configu
redwiththe207-4512 Fuel Transfer Pump
As.
The pub
lished maximum external restrictio n for
the 207-4512 Fuel Transfer Pump As is 54 kPa
(217 inches of H
2
O).