The processing method in this example is for reference only.
When a high-speed wheeled hydraulic excavator was working in the field, the boom could not move suddenly, while the bucket, stick and adjusting hydraulic cylinder were working normally. If the boom is forced to operate, the load of the engine will increase significantly and the engine will stop.
The cause of the fault may be: the spool of boom valve in multi way directional valve is stuck. The port for the boom pilot valve cannot be opened. Boom oil pipe is blocked. The oil pressure is insufficient and the boom spool cannot move.
After exchanging and installing the pressure oil pipes of boom and bucket, the bucket works normally. The boom is still not working. Therefore, it is judged that the valve core of the boom valve in the directional valve is stuck. In view of the bad field maintenance conditions, we have to take the replacement method, and exchange the hydraulic oil pipe between the boom on the boom without rod cavity side of the directional valve and the bucket. After lifting the boom, drive the excavator back to the site.
Remove the boom oil pipes and sealing baffle on both sides of the directional valve in the room, and push the valve core by hand, but it cannot be pushed. According to the past maintenance experience, the valve core cannot be forced out, otherwise the directional valve may be scrapped. So the whole reversing valve was disassembled, and it was found that there were a large number of metal chips and small pieces of metal in the oil passage, among which an irregular metal block was stuck on the valve core and valve body, and was deeply embedded in it, resulting in the valve core stuck and the boom could not move. After taking out the small metal block, take out the valve core, trim, grind, clean and reassemble.
After the change-over valve was installed, the return oil filter and other parts were cleaned to prevent the failure of the hydraulic system. According to the analysis, the metal chips and metal blocks are generated in the hydraulic pump, so it is found that one working pressure is 30MPa, and the other working pressure is less than 10MPa. Obviously, the variable displacement pump with low working pressure is faulty. After the pump was removed and repaired, the excavator returned to normal.
