Reasons and solutions for failure to raise hydraulic system pressure of excavators
In the hydraulic system of hydraulic excavator, the main relief valve is installed at the upper and lower ends of the main control valve, one at each end. This valve sets the maximum pressure when the entire hydraulic system is working. When the system pressure exceeds the set pressure of the main relief valve, the main relief valve opens the oil circuit of the oil return tank to overflow the hydraulic oil back to the oil tank, so as to protect the entire hydraulic system and avoid excessive pressure in the oil circuit. The main relief valve is mainly used to regulate and limit the system pressure. The main relief valve can effectively protect the hydraulic system from being damaged by changing pressure. Therefore, if the main relief valve fails, it will affect the working efficiency of the excavator and even damage the excavator. This article will explain the causes and solutions of the failure of the main relief valve to raise the system pressure, for reference only.
1. Causes
1) The damping hole of the main valve element is blocked. If the main valve element is not cleaned, the oil is too dirty or debris is brought in during assembly.
2) The fitting accuracy is poor during assembly, and the clearance between valves is adjusted incorrectly. The main valve element is stuck in the open position.
3) The return spring of the main valve core is broken or bent, so that the main valve core cannot be reset.
4) The pilot valve fails because the adjusting spring is broken or not installed.
5) The pilot valve fails because the cone valve or steel ball is not installed.
6) Pilot valve failure caused by cone valve fragmentation.
7) The normally open solenoid valve of the remote control port is not energized or the slide valve is stuck.
8) The hydraulic pump coupling key falls off or rolls.
9) Excessive clearance between sliding surfaces.
10) The blade of the vane pump is stuck in the rotor slot.
11) The blade and rotor are installed reversely.
12) The spring in the blade is fatigue deformed or broken due to the high-frequency periodic load.
13) The oil inlet and outlet are installed reversely.
2. Solutions
1) Disassemble the main valve, clean the damping hole and reassemble it.
2) Filter or replace the oil.
3) Tighten the valve cover fastening screws and replace the broken spring.
4) Replace the damaged parts or repair the parts, and the pilot valve will return to normal operation.
5) Check the power line to see if the power is connected. If it is normal, it indicates that the slide valve may be stuck, and the failed parts should be repaired or replaced.
6) Replace or readjust the coupling key, and repair the keyway.
7) Repair the gap between sliding surfaces.
8) Remove and clean the vane pump.
9) Correct the wrong installation direction.
10) Replace the broken spring.
11) Align the oil inlet and outlet.
