The main reasons are that the piston rod is not accurately positioned, the thrust is insufficient, the speed is reduced, and the work is unstable. The reasons are:
(1) Internal leakage of rebound hydraulic cylinder. The internal leakage of the rebound hydraulic cylinder includes leakage caused by excessive wear of the rebound hydraulic cylinder body seal, the piston rod and the seal cover seal, and the piston seal.
The reason for the leakage of the piston rod and the sealing cover is that the seal is wrinkled, squeezed, torn, worn, aging, deteriorated, deformed, etc. At this time, a new seal should be replaced. The main reason for excessive wear of the piston seal is improper adjustment of the speed control valve, resulting in excessive back pressure and improper installation of seals or contamination of hydraulic oil. Secondly, there is foreign matter entering during assembly and the quality of the sealing material is not good. The consequence is slow and weak movements. In severe cases, it can also cause damage to the piston and cylinder, resulting in a "pull cylinder" phenomenon. The processing method is to adjust the speed control valve, and the necessary operation and improvement should be done according to the installation instructions; clean the filter or replace the filter element and hydraulic oil.
(2) The hydraulic circuit is leaking. Including leakage of valves and hydraulic lines. The maintenance method is to check and eliminate the leakage of the hydraulic connection pipeline by operating the directional valve.
(3) The hydraulic oil bypasses the overflow valve and returns to the tank. If the overflow valve enters the dirt and catches the valve core, so that the overflow valve is normally open, the hydraulic oil will bypass the overflow valve and flow directly back to the oil tank, causing no oil to enter the rebound hydraulic cylinder. If the load is too large, although the regulating pressure of the relief valve has reached the maximum rated value, the rebound hydraulic cylinder still cannot get the thrust required for continuous action and does not act. If the adjustment pressure is low, the vertebral force still required for loading cannot be achieved due to insufficient pressure, which is manifested as insufficient thrust. At this time, the relief valve should be checked and adjusted.