TUBE G25311611 - Caterpillar

Illustration 1 g00814065
Illustration 2 g00544128
Typical example (1) Main relief valve (2) Signal limiter valveThe main relief valve (1) is located in the body of the main control valve. The main relief valve (1) activates in order to limit the main pump output pressure to approximately 36000 to 37000 kPa (5220 to 5365 psi). The pilot controlled main relief valve protects the main hydraulic system against excessive pressure spikes. The main relief valve is set higher than the setting of the load sensing signal limiter valve (2) .The pressure oil that is supplied by the main pump goes into the dump valve through the orifice check valve in order to keep the dump valve closed. When the main pump pressure oil increases to the maximum relief pressure setting, the pressure exceeds the pilot valve pressure setting. The pilot valve opens and the pressure oil inside the dump valve is relieved to the tank. As a result of the pressure drop inside the dump valve, the valve opens allowing pump oil to vent to the hydraulic tank. The main relief valve and line relief valves are identical in construction and identical in operation.