BUCKET AR-GENERAL PURPOSE 2795373 - Caterpillar

Illustration 1 g02425976
Components of the gas pressure regulator (typical example)
(1) Balance line connection
(2) Control spring
(3) Adjusting nut
(4) Pitot tube
(5) Outlet
(6) Inlet
(7) Stem
(8) Lever
(9) Pipe plug
(10) Diaphragm 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 full load carburetor air inlet pressureThe carburetor supply differential pressure is determined by referencing the high and lower heating value fuels graphs within Testing and Adjusting, "Gas Pressure - Check and Adjust". The carburetor supply differential pressure is based on the orifice used in the carburetor and the heat value of the fuel.The pressure of control spring (2) can be adjusted with adjusting nut (3). If necessary, spring force is adjusted during setup to match the type of carburetor and the energy value of the fuel.The force from the control spring pushes down on diaphragm (10). When the force of outlet (5) pressure pushing up on the diaphragm exceeds the combined force of control spring and inlet (6) pressure, stem (7) will close and gas will not flow to the outlet.When downstream demand increases, the pressure under the diaphragm decreases. The control spring pushes down on the diaphragm and lever (8). The stem shifts, allowing gas to flow from the inlet to the outlet. The stem stops opening when gas pressure in the chamber equals spring force.When downstream demand decreases, the pressure under the diaphragm increases. This pressure overcomes the control spring force. The diaphragm and lever lift, shifting the stem, and restricting gas flow from the inlet to the outlet. The stem stops closing when gas pressure in the chamber equals the spring force.The balance line (not shown), is a tube or hose located between balance line connection (1) and the carburetor air inlet. The balance line connects the carburetor air inlet directly with the top of the diaphragm. The balance line allows the carburetor to adjust fuel demand directly with the regulator. This direct connection keeps the pressure differential between the carburetor and the regulator a constant regardless of actual pressure supplied to the carburetor. The balance line prevents the air fuel mixture from becoming overly lean or rich.On a natural aspirated engine without a balance line, the engine will run rich if the air cleaner restricts airflow. However, the balance line connects the vacuum within the carburetor inlet to the regulator above the diaphragm. The vacuum causes the lever to lift and decrease the gas flow supplied to the carburetor, keeping the air/fuel ratio correct. On a turbocharged engine without a balance line, the increased boost pressure would cause the engine to run lean. The balance line transfers the extra boost pressure to the regulator on top of the diaphragm. The boost pressure causes the lever to lower and increase the gas flow supplied to the carburetor, keeping the air/fuel ratio correct.