WASHER-HARD 4813909 - Caterpillar

Illustration 1 g02150341
Components of the gas pressure regulator (typical example)
(1) Adjusting nut
(2) Spring
(3) Chamber
(4) Balance line port
(5) Diaphragm
(6) Compensation sensing line
(7) Valve stem
(8) Inlet for gas
(9) Chamber
(10) Outlet for gas On a low-pressure gas installation, the quantity of fuel supplied to the carburetor is determined by the following two factors:
Differential between the regulator outlet pressure and the carburetor air inlet pressure
Differential between the main supply pressure to the regulator and the carb air inlet pressureThe carburetor supply differential pressure is determined by referencing the "High and Lower Heating Value Fuels" graphs. The carburetor supply differential pressure is based on the orifice used in the carburetor and the heat value of the fuel.A balance line must be connected between balance line port (4) and the inlet of the carburetor. This balance line allows the regulator to maintain a consistent gas pressure to the fuel control valve. The balance line allows the pressure in chamber (3) to equalize to the pressure of the air supply that is supplied to the carburetor. Compensation line (6) allows carburetor supply pressure (10) to fill chamber (9) under the diaphragm (5).The pressure of the spring can be adjusted with adjusting nut (1). The pressure must be adjusted for the type of carburetor and the energy value of the fuel.The pressure from spring (2) presses on diaphragm (5). The spring pressure is countered by negative pressure created in the chamber by any air cleaner restriction. This negative pressure enters the chamber through balance line port (4). The movement of the diaphragm operates valve stem (7) and the valve opens. The valve opening allows gas from inlet (8) to flow to outlet (10). The valve stops opening when the gas pressure in chamber (9) equalizes the spring pressure and the vacuum in chamber (1).As the load increases, the ECM opens the throttle plate further. The increased throttle plate opening allows fuel to flow into the inlet manifold which reduces the pressure on the gas side of the diaphragm. The pressure from the spring, minus the negative air pressure, opens the gas valve. The valve opens until the pressure under the diaphragm is balanced with the forces of the spring and the negative air pressure above the diaphragm.