Excavator accessories E200B E320B relief valve Auxiliary gun hydraulic valve 352-7122

The main relief valve is installed on the upper and lower ends of the main control valve, one upper and one lower. The valve sets the maximum pressure for the entire hydraulic system to work. When the system pressure exceeds the set pressure of the main relief valve, the main relief valve opens the oil circuit of the return tank to overflow the hydraulic oil back to the tank to protect the entire hydraulic system and avoid excessive oil pressure. The relief valve has two sets of pressure, when the pilot pressure is OFF, for the first set pressure of 355kg/cm2; When the pilot pressure is ON, set the pressure 380kg/cm2 for the second stage.

Fault diagnosis

Fault phenomenon: The speed of all working devices is slow (the speed of all working devices is lower than the standard value), the work is weak, the maximum pressure of the main pump is less than 150kg/cm2.
Inspection result: The main relief valve plunger (3) has a dirt blocking the φ0.5 hole.

Fault analysis: Due to the plug of the plunger (3) hole, the pressure difference between the two ends of the plunger (3) is very large, the plunger (3) is usually open, and the high pressure oil passes through the plunger (3) normal oil tank, so the main pressure is reduced.

Troubleshooting: 1) disassemble and clean the valve before assembling it.

2) Check the hydraulic oil and filter element has not been changed for a long time, it is very dirty, the impurities blocking the holes are from the hydraulic oil, so clean the pipeline, replace the hydraulic oil and filter element.

3) Try again after all is completed, and the pressure will return to normal.