Elimination of weakness of boom lifting of WL80 excavator

A WL80 wheeled excavator, when loaded with lifting capacity, slow action, rising oil temperature. For this, you can follow the following steps for testing and troubleshooting.

(1) connecting the pressure gauge in the hydraulic system, measuring the pressure of 18MPa, reaching the rated pressure value of the system, and thus eliminating the possibility of the safety valve being out of order. Preliminary judgment, the problem may be in the boom cylinder or hydraulic pump.

(2) it is troublesome to disassemble the hydraulic cylinder, so it is necessary to test and judge whether the hydraulic cylinder is normal before disassembly. In full load, lift the moving arm to the maximum height (pay attention to safety), then turn off the engine and make the main valve of the manifold valve in the middle locking state. At this moment, the boom cylinder is obviously sinking. The causes of this phenomenon are:

1) boom overload, low pressure. As requested, the setting pressure of the boom overload valve is 20MPa, at the full load lifting arm. The pressure gauge indicates that the system pressure is 18MPa, indicating that the setting pressure of the overload valve is not less than 18MPa. Therefore, the possibility of low pressure of the boom overload valve can be basically eliminated. The position of the overload valve and the system relief valve can also be interchanged for accurate measurement.

2) multiway valve main valve leakage. Generally speaking, at rated pressure, the normal leakage of the main valve in the middle position is very small, which is not enough to cause obvious hydraulic cylinder subsidence. At the same time, taking into account the use of this machine is not long, so it can basically eliminate the possibility of leakage of multi-channel valve main valve.

3) the piston ring of the boom cylinder is damaged. The above analysis shows that this possibility is most likely. Therefore, the hydraulic cylinder was disassembled and it was found that the piston rings of the two boom cylinders had been seriously damaged, which confirmed the prior judgment.