Table of Contents
Advertisement
Gaseous Fuel Systems
Fuel Pressure Regulators
General
A common cause of a generator not operating correctly is
incorrect sizing and installation of gaseous fuel supply
system between gas meter (utility source) and generator
connection. The fuel supply system consists of a primary
regulator to regulate flow and volume from fuel source
(utility supply) to generator, and all of the associated pip-
ing, fittings, and shutoff valves, both upstream (feeding
main meter/regulator) and downstream (between meter
and primary regulator), which connect fuel source to con-
nection point on generator. Fuel supply system must be
capable of supplying the correct volume of fuel within the
correct pressure range to connection point on generator.
The volume of fuel and operating pressure required are
listed in the technical specifications for the applicable
generator. Fuel pressure at unit must remain within spec-
ified operating range and not drop below minimum pres-
sure specified.
Best Practices
These are the manufacturer recommended best prac-
tices for configuring and sizing fuel supply piping to gen-
erators. These best practices have been developed
specifically for the manufacturer's product and may not
represent conventional gaseous fuel system sizing meth-
ods, particularly those used frequently with low volume
appliance installations. Compliance with these best prac-
tices will help to verify the generator engine will operate
correctly under dynamic conditions.
•
Minimum distance from primary pressure regulator
outlet to generator connection point is covered in
the pressure regulator manufacturer's installation
instructions. Do not connect pressure regulator
directly to flexible fuel line on generator. Piping
between primary pressure regulator and connec-
tion point on the generator acts as a reservoir
(accumulator) which stores fuel and, therefore, can
minimize or maximize changes in delivery pressure
that the generator sees during cranking and load
changes.
•
See
Fuel Shutoff
Valve. Required fuel pressure to
unit is measured before the fuel shutoff solenoids
at the inlet to the unit mounted regulator. A 1/8 in
pipe port in the pressure regulator body, or in the
piping just before the pressure regulator, is pro-
vided for this purpose.
•
Natural Gas: CFH x 1000 = BTU per hour
•
Natural Gas: CMH x 37.26 = MJ per hour
NG Operating Range: 3.5–14 in water column (0.87–
3.48 kPa)
20
•
Seasonal supply pressure changes to primary
pressure regulator can affect correct operation of
the generator. Fuel supply pressure to unit must
remain within specified operating parameters as
stated in the unit specification sheet. Contact local
utility to find out what can be done to correct sea-
sonal changes.
•
Use sediment traps.
•
Generator must have its own dedicated fuel supply.
Do not connect any other loads to the outlet of the
primary pressure regulator.
For LP gas systems, due to the nature of the conversion
process from LP liquid to LP vapor, consider the follow-
ing:
•
Vaporization rate of a given LP tank is dependent
on the liquid level in tank (wetted surface area),
ambient temperature around tank, and relative
humidity.
•
When ambient temperatures are below 40 °F (4
°C), engine fuel consumption is high, and sufficient
humidity is present, condensation can occur result-
ing in frosting of the tank at the liquid level. This
condition can lead to a reduced rate of vaporiza-
tion. See LP tank sizing section for more informa-
tion.
Operating Fuel Pressure
The unit specification sheet lists operating fuel pressure
range, as well as 100% load fuel consumption rate. Pres-
sure range is minimum and maximum acceptable pres-
sures for correct operation of the unit under all operating
conditions. Maximum fuel system pressure drop at each
condition, that is, static, cranking, running at no load, and
running at full load, is 1–2 in water column (0.25–0.50
kPa) as measured at primary fuel pressure regulator. See
Final Test Procedure
for definitions of each condition.
Engine Fuel Consumption
Volume of gaseous fuel consumed at various loads is
listed in the unit specification sheet. Both NG and LP gas
values are provided in cubic feet per hour (CFH). Interna-
tional units of measure are also provided.
Use the following formulas if it becomes necessary to
convert CFH to BTUs per hour:
•
LP Vapor: CFH x 2500 = BTU per hour
•
LP Vapor: CMH x 93.15 = MJ per hour
LP Operating Range: 7–14 in water column (1.74–3.48
kPa)
Installation Guidelines For Spark-Ignited Stationary Generators
Advertisement
Table of Contents
