MECHANICAL INSTALLATION — FUEL SYSTEM (GASEOUS FUELS)
Gaseous Fuels
Some MQ Power Industrial generator sets may utilize gaseous fuels such as Pipeline natural gas or Liquid Petroleum Gas (LPG). Regardless of the fuel used, the primary factors in successful installation and operation of a gas fuel system are:
The gas supplied to the generator set must be of acceptable quality.
The gas supply pressure must be measured to ensure that the gas supply at the generator set, not just at the source, is of proper pressure must be available while the generator is running at full load.
The gas must be supplied to the genset in sufficient volume to support proper operation.
Failure to meet the minimum requirements in these areas will result in the inability of the generator set to operate or carry rated load and will induce poor performance.
Gaseous fuels are actually a mixture of several different hydrocarbon gases and various contaminants, some of which are potentially damaging to an engine over time. The quality of the fuel is based on the amount of energy per unit volume in the fuel and the amount of contaminants in the fuel. Most gaseous fuel suppliers can provide a fuel analysis that describes the chemical makeup of the fuel that is to be provide to insure that the fuel is usable for a specific application, and also to verify that the BTU content of the fuel is sufficient to provide necessary kW output of the genset.
Energy Content
One of the most important characteristics of gaseous fuel used in a generator set is the heat value of the fuel. The value of a fuel describes how much energy is stored in a specific volume of the fuel. Gaseous fuel has a low heat value (LHV) and a high heat value (HHV). The low heat value is the heat available to do work in an engine after the water in the fuel is vaporized. If the low heat value of the fuel is too low (generally below 905 BTU/ft3) the engine will not be able to maintain full output power and may not produce rated power at standard ambient temperature conditions.
BTU Content
The total BTU content of the fuel will determine the rating of the generator set when using fuel of a specific compostion. If any component of the fuel has more than the specific value allowed, derating will be required. Consult MQ Power for fuel derating instructions.
TABLE 11. TYPICAL BTU CONTENT OF GASEOUS FUEL
DRY PIPELINE GAS | FIELD GAS |
| LPG | |||
|
|
|
|
|
|
|
LHV | HHV | LHV | HHV | LHV |
| HHV |
|
|
|
|
|
|
|
936 | 1,038 | 1,203 | 1,325 | 2,353 |
| 2,557 |
BTU/ft3 | BTU/ft3 | BTU/ft3 | BTU/ft3 | BTU/ft3 |
| BTU/ft3 |
Pipeline Natural Gas
The most common gaseous fuel for generator sets is called Pipeline natural gas. In the United States, "dry pipeline natural gas" has specific qualities based on federal requirements. U.S. pipeline gas is a mixture composed of approximately 98% methane and ethane with the other 2% being hydrocarbons such as propane and butane, nitrogen, carbon dioxide, and water vapor. "Dry" means that is free of liquid hydrocarbons such as gasoline, but NOT that it is free of water vapor.
Field Gas
The composition of Field natural gas varies considerably by region and continent. Careful analysis is necessary prior to using field natural gas in an engine because in can contain heavier hydrocarbon gases which may require derating of the output of the engine. Field natural gas may also contain other contaminants such as sulfur.
Liquid Petroleum Gas (LPG)
Liquid Petroleum Gas is available in two grades, commercial and special duty. Commercial propane is used where high volatility is required. Special duty propane (also called HD5) is a mixture of 95% propane and other gases such as butane that allows better engine performance due to the reduction
PAGE 40 — INDUSTRIAL GENERATOR SETS — APPLICATION & INSTALLATION MANUAL — REV. #4 (09/07/07)
