1. The system has no pressure
① The oil is too dirty or the damping hole of the slide valve is not cleaned during assembly, so that the damping hole is blocked and the slide valve cannot move. Filter or replace the hydraulic oil and clean the spool valve to make the damping hole clear.
② The spool spring is broken or bent, and the spool cannot be reset. Replace the spring.
③ The spool is stuck in the open position. Disassemble and overhaul. If the slide valve is corroded or rough, it can be polished with metallographic sandpaper. If the valve body has burrs, it needs to be repaired.
④ The pilot valve spring is broken. replace.
⑤ The main valve of the pilot valve is damaged. replace.
⑥ The oil inlet and outlet are reversed, there is no pressure oil to push the slide valve to move. Replace the inlet and outlet oil pipes.
⑦ The fluid of the hydraulic control port is directly connected to the fuel tank. Install a blockage on the fluid control port and protect the seal to prevent leakage.
2. Large pressure fluctuations
① The sliding of the spool valve or bending deformation makes the spool valve move in the valve body hole inflexibly, and sometimes the phenomenon of jamming occurs. Remove burrs or replace spool.
② The oil is not clean, so that the damping hole is closed when it is blocked. Replace oil, remove impurities in valve body and dirt in damping hole.
③The damping aperture is too small, and the damping effect is poor. The original damping hole can be closed and the damping hole can be reprocessed (generally about 1mm).
④ Air exists in the hydraulic system. Remove air from the system.
⑤ The cone valve is damaged, the cone valve and the seat are not well matched, and the wear is uneven. Replace the poppet valve and the valve seat.
⑥ The spring is deformed or too soft, making it difficult to reset the spool. Replace the appropriate spring.
⑦The pressure adjusting screw changes the pressure due to the loosening of the lock nut. After adjusting the pressure, the lock nut will be tightened.
⑧ The pressure and flow of the hydraulic pump fluctuate greatly, making the overflow valve unable to play a balancing role. Replace or repair hydraulic pump.
3. Noise generation
① The roundness error of the spool and the body hole is large or the gap is too large, causing leakage. Grind the valve body hole, reconfigure the spool valve, and make each precision meet the technical requirements.
② The gap between the spool and the valve body hole is too small, and the spool does not move flexibly. Grind the spool valve or grind the valve body hole to control the clearance within the required range.
③The pressure-regulating spring is bent and deformed. replace.
④The lock nut has been loosened. The lock nut should be tightened immediately after pressure adjustment.
⑤ The pilot valve is in poor contact with the seat hole. The rough surface and large roundness error make the pressure-regulating spring unbalanced, the cone valve oscillates screamingly. Grind the valve seat hole to control the roundness error of the seal oil between 0.005 ~ 0.01mm, and the surface roughness Ra <0.8fzm. For grinding cone valves, the surface roughness value should reach 0.4Mmo
⑥ The vertical error of the spring axis of the pilot valve and the end face makes the poppet valve tilt and uneven contact with the valve seat. Replace the spring whose end face is ground and perpendicular to the axis to prevent the cone valve from tipping.
⑦ The hydraulic pump has poor oil intake and insufficient oil supply. Remove the filter dirt at the oil inlet and increase the oil inlet area appropriately.
⑧ The oil return pipe of the valve is not smooth. Adjust the height of the oil return pipe to be more than 50mm away from the bottom of the tank.
4. Excavator leaks seriously
① The clearance between the spool valve and the valve body hole is too large. Remake spool valve and match research.
②The seal is damaged. replace.
③Poor contact between the poppet valve and the valve seat hole or serious wear. Grind the cone valve and grind the seat hole to make it fit tightly.
④ The clearance between the valve cover and the valve body hole is too large. Refit the valve cover to control the fit clearance.
⑤ The oil-resistant paper pad at the joint surface was broken. When replacing oil-resistant paper pads, be careful not to cover the oil-through holes to ensure that the oil-through holes are unobstructed.
⑥ The screws at each connection are not tightened. Tighten the screws at each connection.
