Multiquip MQP40IZ, MQP20IZ Mechanical Installation Fuel System Gaseous Fuels, Contaminants

MECHANICAL INSTALLATION — FUEL SYSTEM (GASEOUS FUELS)

Contaminants

The most harmful contaminants in gaseous fuels are water vapor and sulfur. Water vapor is damaging to an engine because it may cause uncontrolled burning, pre-ignition, or other effects that can damage an engine. Liquid vapor or droplets must be removed from the fuel prior to entry into the engine by use of a dry filter that is mounted in the fuel system prior to the primary fuel pressure regulator. Sulfur and hydrogen sulfides will cause corrosion and serious damage to an engine over a relative short periods of time. The effects of sulfur in the fuel can be counteracted in part by use of high-ash natural lubricating oils. In general, engines should not be operated with fuels in excess of 10 parts per million (ppm).

Gaseous Fuel Supply

Consider the following when installing a natural gas or LPG fuel system:

„Gaseous fuel supply system design, materials, components, fabrication, assembly, installation, testing inspection operation and maintenance must comply with all applicable codes and standards. In addition, see NFPA Standards No. 30, No. 37, No. 54 and No. 58.

„The layout and sizing of gas piping must be adequate for handling the volume of gas required by the genset and all other equipment, such as building heating boilers supplied by the same source. Full load gas flow must be available at not less that the minimum required supply pressure, typically from 5 to 10 inches WC (water column) depending on the model. Final determination of pipe sizes must however be based upon the method approved by the authority having jurisdiction (see NFPA No. 54).

„Most installations will require one or more service gas pressure regulators. Gas supply pressure should not exceed 13.8 or 20 inches WC at the inlet to the generator set depending on the model. High pressure gas piping is not permitted inside buildings (5 psig for natural gas and 20 psig for LPG unless higher pressures are approved by the authority having jurisdiction). Gas pressure regulators must be vented to the outdoors according to code.

„All fuel gas systems at service pressures of 125 psig and less shall be installed in accordance with NFPA 54. All fuel gas systems at service pressures in excess of 125 psig shall be installed in accordance with ANSI/ ASME B31.3.

„LP-Gas systems, whether liquid or vapor phase, shall be installed in accordance with the provisions of NFPA 58.

„The pressure regulator installed on the supply line at the gas source for generator applications should never be a “pilot” regulator. A “pilot” style regulator is the type where the regulator requires a pressure line from the regulator housing to the downstream gas pipe to “sense” when downstream pressure has dropped. Pilot regulators do not work because the response time is unacceptable compared to the large–instantaneous changes in demand from the generator set.

„Approved flexible fuel hose must be used for connections at the engine to take up generator set movement and vibration.

„Most codes require both manual and electric (battery– powered) shut-off valves ahead of the flexible fuel hose(s). The manual valve should be of the indicating type.

„A dry fuel filter should be installed in each line to protect the sensitive pressure regulating components and orifices downstream from harmful foreign substances carried along in the gas stream (rust, scale, etc.).

„The rate of vaporization in an LPG tank depends upon the outdoor air temperature, unless the tank is equipped with a heater, and the quantity of fuel in the tank. Even on cold days ambient air heats and vaporizes LPG (mostly through the wetted tank surface) when air temperature is higher than LPG temperature.Withdrawing vapor causes tank temperature and pressure to drop. (At –37° F [–38° C] LPG has zero vapor pressure.) Unless there is enough fuel and enough heat available from ambient air, the vaporization rate will drop off, as the generator set runs, to less than that required to continue running properly.

Leakage of gaseous fuel is extremely dangerous. Natural gas and LPG contain carbon monoxide which can cause severe bodily harm or death when inhaled. Also, serious explosions and fires will occur if gas or propane leakage occurs where there is a spark. To prevent such hazards, immediately shut off all natural gas or propane supplies if a leak is detected. If in an enclosed area, ventilate the area as quickly as possible.

INDUSTRIAL GENERATOR SETS — APPLICATION & INSTALLATION MANUAL — REV. #4 (09/07/07) — PAGE 41