In the hydraulic system, if only the boom is lifted slowly and powerless, and the turning bucket overturns normally. It is not difficult to see from the working principle diagram that other works normally, which indicates that the working pump and the general safety valve work normally, and the pressure they provide to the whole system is sufficient. At the same time, it also indicates that the oil quantity and quality of the pipeline at the oil inlet end of the pump, the oil filter and the oil tank are OK. At this time, you only need to check the boom slide valve, boom cylinder, boom oil pipe and its seals.
Inspection steps:
(1) Check the oil circuit for blockage and explosion, and conduct routine treatment first. Remove the oil pipe, remove the boom slide valve body, valve rod and relevant parts for cleaning, clean the oil passage and blow dry with compressed air
(2) Check the oil circuit for leakage. The leakage of the hydraulic system usually occurs after a period of use From the surface phenomenon, it is mostly caused by seal failure, damage, extrusion or tension on the sealing surface The main reasons are: oil pollution, improper sealing surface roughness, unqualified sealing groove, loose pipe joint, increased clearance of mating parts, excessive oil temperature, deterioration of sealing ring or poor assembly, etc Leakage is divided into internal leakage and external leakage. Generally, the fault is mainly caused by internal leakage.
(3) Treatment of internal leakage fault this part of internal leakage is mainly caused by the leakage in boom slide valve and cylinder Internal leakage mainly occurs inside the valve body and oil cylinder, which is not easy to check However, we can use some auxiliary methods to judge the leakage.
(4) Check the boom cylinder. When the boom cylinder piston is fully retracted, remove the oil pipe without rod cavity, so that the rod cavity of the boom cylinder continues to be filled with oil If a large amount of working oil leaks out from the oil pipe port without rod cavity, it indicates that the hydraulic cylinder has internal leakage; It can also make the bucket full of load, lift it to the limit position, put the boom control lever in the middle position, shut down the engine, and observe the sinking speed of the boom: then, put the boom control lever in the rising position. If the sinking speed of the boom is significantly accelerated at this time, it also indicates that the internal leakage occurs in the hydraulic cylinder; If the sinking speed does not change significantly, the internal leakage is caused by the boom slide valve.
Troubleshooting:
If the leakage test result in the oil cylinder exceeds the specified value, it shall be disassembled for further inspection. If the sealing ring is damaged, it shall be replaced; if the cylinder wall is seriously strained, it shall be replaced; if the boom valve is seriously worn, it shall be replaced.
