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| Illustration 1 | g00818669 |
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Top view and section views of a gas pressure regulator (1) Chamber (2) Adjusting nut (3) Spring (4) Orifice for the balance line (5) Diaphragm (6) Valve stem (7) Inlet for gas (8) Chamber (9) Outlet for gas | |
The fuel flow is determined by the pressure differential between the gas pressure and the air pressure. Usually, the pressure of the gas must be greater than the air pressure.
To maintain an accurate adjustment of the gas pressure to the carburetor, a balance line is connected to orifice (4) and to the inlet of the carburetor. This causes the pressure in chamber (1) on the air side of diaphragm (5) to be equal to the pressure in the carburetor.
The pressure of spring (3) can be adjusted with nut (2). The pressure must be adjusted for the type of carburetor.
The spring pressure and the air pressure in chamber (1) presses on diaphragm (5). The movement of the diaphragm operates valve stem (6) and the valve opens. This allows gas from inlet (7) to enter chamber (8) and flow through outlet (9). The valve stops opening when the gas pressure in chamber (8) under the diaphragm is equal to the force from the spring and the air pressure in chamber (1).
As the load increases, the governor opens the throttle plate further. This reduces the pressure on the gas side of the diaphragm. The spring and the air pressure open the gas valve. The gas valve opens until the pressure under the diaphragm is balanced again with the forces of the spring and pressure from the balance line on top of the diaphragm.