Fuel Pressure Regulator

Fuel Pressure Regulator

Figure 74: Fuel Pressure Regulator:

The fuel pressure regulator (Figure 74) used in the Natural Gas fuel system is a single-stage pressure reducing regulator which expands natural gas from storage pressures of 1,379 to 20,685 kPa (200 to 3,000 psig) to engine fuel injector pressures of 724 to 862 kPa (105 to 125 psig).

The regulator contains a pressure relief device [1,896 kPa (275 psig) check valve] which protects the low pressure fuel system. The low pressure fuel system no longer must fulfill the design requirements of the high pressure fuel system, therefore reducing cost, weight and complexity.

When gas expands, the fuel temperature drops significantly causing extreme cold temperatures [-177°C (-160 °F)] that may damage synthetic fuel system components as well as cause water vapor within the fuel to condense, freeze and plug the lines, valve and injectors. To prevent this, engine coolant is routed through the fuel pressure regulator to warm the fuel before it expands.

The regulator has an internal thermostat to control the flow of engine coolant. This prevents overheating and subsequent thinning of the fuel which may cause lean combustion. Outlet coolant flow is restricted by the thermostat when it rises above approximately 82°C (100°F).