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LP Gas System
See
Figure
4-2. LP gas uses vapors formed above liquid
propane in fuel supply tank (A). The maximum fuel tank
fill capacity is 80% and a minimum of approximately 20%
of fuel tank capacity is needed for fuel expansion from liq-
uid to vapor state. Fuel pressure and volume require-
ments for a LP gas system at the connection point of the
generator are listed on the unit specification sheet.
Pressure regulation for vapor withdrawal systems is typi-
cally a two-step process. First, by reducing high tank
pressure to a lower line pressure with a first-stage regula-
tor (C), then reducing line pressure to pressure required
by unit with a second-stage regulator (E). Both regulators
and associated system piping and valves need to be
sized correctly to provide generator with the required vol-
ume and pressure of fuel at the generator connection
point.
A
Fuel supply tank
B
Manual fuel shutoff valve
C
First-stage regulator with relief valve and pressure tap
Sediment Trap
Some local codes require a sediment trap (D). The sedi-
ment trap must be installed downstream of the generator
fuel shutoff valve, and as close as practical to the inlet of
the generator. Sediment trap must be either a tee fitting
having a capped nipple installed vertically in the lowest
opening of the tee fitting, or a device approved for use as
an effective sediment trap.
Installation Guidelines For Spark-Ignited Stationary Generators
B
F
Figure 4-2. Typical LP Gas Withdrawal Fuel System
Fuel pressure from the primary regulator (supplied by
installing contractor) to generator's fuel shutoff valve (B)
should be between 7–14 in water column (1.74–3.48
kPa). Always verify fuel pressure using the appropriate
specification sheet for the generator.
The piping system connecting outlet of the first-stage
regulator to the connection point on the second-stage
regulator must be correctly sized to provide fuel volume
required by unit at 100% load.
The piping system between outlet of second-stage regu-
lator and generator connection point must be sized to
provide fuel volume required by generator at 100% load,
while also staying within pressure range noted on the unit
specification sheet.
Follow regulator manufacturer's recommendation for
placement and mounting of the regulator.
E
D
D
Sediment trap
E
Second-stage regulator
F
Flexible fuel line
Gaseous Fuel Systems
A
B
C
009909
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