PIN 3309671 - Caterpillar

Illustration 1 g01209320
Main Relief ValveThere are two main relief valves. Each pump has a dedicated relief valve. Each main relief valve is installed in a manifold that is mounted in the front frame at the articulation hitch.The main relief valve is between the implement pump and the main control valve. The pressure setting of the main relief valve for the fixed displacement axial piston pump is 31000 400 kPa (4496 58 psi).The pressure setting of the main relief valve for the variable displacement axial piston pump 32800 400 kPa (4757 58 psi).Hydraulic oil flows from the implement pump into inlet (1), through the orifice in the center of valve (2) and into the chamber for spring (8). The pressurized oil in the spring chamber contacts poppet (3). When the hydraulic oil pressure is below the setting of the relief valve and below the force of the spring (9), the valve will stay closed.When the oil pressure is above the relief valve setting, the force will overcome spring (9). The poppet (3) will move away from the valve seat. The oil in the chamber will flow past poppet (3 ) and through passage (7) to the hydraulic tank.With poppet (3) off the seat, only the force of spring (8) is acting on valve (2). The pressure of the oil in inlet (1) moves valve (2) off the seat. This will allow oil to flow through the inlet and out through outlet (6) and back to the hydraulic tank.The pressure setting of the relief valve can be adjusted by changing the force of spring (9). This force keeps poppet (3) on the seat. In order to adjust the pressure, loosen locking nut (4) and turn plunger (5). By rotating plunger (5) in the clockwise direction, the pressure in the main relief valve will increase. By rotating plunger (5) in the counterclockwise direction, the pressure setting of the main relief valve will be decreased.