Table of Contents
Advertisement
4.3 Fuel Lines
Note: Never use fuel piping to ground electrical
equipment.
Line Type. Use Schedule 40 black-iron pipe, steel
tubing, or copper tubing for diesel fuel systems. Diesel
fuel reacts adversely with galvanized tanks and piping,
producing flaking sediment that quickly clogs filters and
causes fuel pump and fuel injector failure. Ensure that
any flexible fuel lines used are approved for diesel fuel.
Flexible
connectors.
spanning a minimum of 152 mm (6 in.) between the
stationary piping and the engine fuel inlet connection.
Note: Keep fuel lines away from exhaust system.
Sizing fuel lines. Size the fuel line to handle the flow of
fuel and to withstand year-round climate conditions.
Use steel tubing as the codes require. Use 8-mm
(5/16-in.) ID (minimum) tubing with a 230 mm (8 in.)
(minimum) flexible section to allow free movement of the
generator set.
Fuel line connection sizes:
Fuel Inlet
Fuel Return
Routing fuel lines. Take care when routing the fuel line
from the fuel tank to the generator set. Keep the fuel
lines as short as possible but maintain adequate
clearance from the exhaust system. Locate the fuel
lines with the entry point near the fuel/water separator
(max. lift of the fuel pump is 1 m or 39 in.). See NO TAG
or the dimension drawings in Section 7 for fuel inlet and
return connections.
Return lines. A diesel system delivers more fuel to the
injectors than the engine uses; therefore, a system has
one supply line from the fuel tank and at least one return
line from the fuel injectors. Size the fuel return lines no
smaller than the fuel supply lines.
Route the return fuel line to either the day tank or the
main storage tank. Place the return lines as far away
from the pickup or fuel diptube as possible to prevent air
entry and to keep warm fuel from being reintroduced to
the engine. If fuel lines are routed to the day tank, note
TP-6609 6/08
Use
flexible
connections
1/4 NPT
8 mm (5/16 in.)
the day tank size requirements in Section 4.2, Day
Tanks.
A properly designed fuel return line is unrestricted and
as short as possible, and it allows gravity return of fuel to
the storage tanks. In installations where gravity return is
not possible, obtain approval of the design from the
generator set supplier based upon the engine's
specifications before installing a fuel system with static
head pressure on the return lines. Fuel return line
restriction can cause engine hydraulic lock or
uncontrollable overspeed on some systems.
4.4 Auxiliary Fuel Pumps
Primary, engine-driven fuel pumps typically develop a
maximum of 48 kPa (7 psi) pressure and draw fuel to
approximately 1.2--1.4 m (4--6 ft.) vertically or 6 m
(20 ft.) horizontally. When the main tank is located a
greater distance from the engine or for a more reliable
fuel system, use an auxiliary pump alone or in
connection with a day tank. See Figure 4-4. Limit
auxiliary fuel pump pressure to approximately 35 kPa
(5 psi).
Use a shutoff solenoid valve wired into the engine run
circuit or a check valve to help keep the fuel line primed.
Install the check valve on the outlet side of the auxiliary
fuel pump to minimize inlet restriction.
Auxiliary fuel pump options. Connect an engine
starting battery-powered electric fuel transfer pump in
series with the engine-driven transfer pump. Locate the
electric pump nearer to the fuel tank than to the engine.
An auxiliary pump located at the fuel tank approximately
doubles the horizontal and vertical distance limits of a
single engine-driven pump.
Where vertical runs exceed 5.5 m (18 ft.) or horizontal
runs exceed 61 m (200 ft.), remote-mount the pump
adjacent to the fuel storage tank. This type of installation
allows these pumps to push fuel over 305 m (1000 ft.)
horizontally or more than 31 m (100 ft.) vertically and
deliver adequate fuel for generator sets up to 2000 kW.
Always connect a positive-displacement pump directly
to a day tank and float switch to protect the engine fuel
system from excessive fuel pressures.
Section 4 Diesel Fuel System
33
Advertisement
Table of Contents
