The action of excavator boom is one of the most frequently used actions in the daily construction process. If the boom is lifted slowly and powerlessly, it must be shut down for repair. This article will share how to analyze and judge the problem of slow and weak boom lifting until it is solved. It is only for reference.
If only the boom is lifted slowly and weakly, and other actions are normal, it indicates that the working pump and main safety valve work normally and the pressure provided to the whole system is sufficient. It also shows that there is no problem with the oil quantity and quality of the pipeline and oil filter at the oil inlet end of the pump and the oil tank. At this time, just check the boom slide valve, boom cylinder, oil pipe and sealing ring of boom.
1) Check the oil circuit for blockage
First remove the oil pipe, remove the boom slide valve body, valve rod and related components for cleaning. Clean the oil passage and blow it dry with compressed air.
2) Check the oil circuit for leakage
The leakage of hydraulic system is generally produced after using for a period of time, and most of them are caused by seal failure, damage, extrusion or tensile injury of sealing surface.
There are many reasons for seal damage, such as 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
The internal leakage mainly occurs in the boom spool valve and the 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) Inspection of boom cylinder
After the boom cylinder piston is retracted to the bottom, remove the oil pipe without rod cavity to make the rod cavity of boom cylinder continue 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, stop the engine, and observe the sinking speed of the boom.
Then, place the boom control lever in the rising position. If the boom sinking speed 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.
5) Inspection of boom spool valve
The leakage of boom slide valve is mainly due to the large matching clearance between valve rod and valve body, damage of pressure regulating spring, damage of seal in valve, etc. Check the fit clearance between the valve stem and the valve body, check the pressure spring, and see if the seal in the valve body is damaged.
If the leakage test result in the oil cylinder exceeds the specified value, it shall be disassembled for further inspection. For example, the sealing ring is damaged, the cylinder wall is seriously strained or the boom valve is seriously worn. In any of the three cases, it shall be replaced.
