If the hydraulic working device moves slowly, it indicates that the fault of slow lifting of boom cylinder is in the main oil supply or total oil return part. If the working speed of other working devices is normal and only the boom cylinder is lifted slowly, it indicates that the failure of weak lifting is in the boom branch.
(1) Visual inspection for leakage outside the main oil circuit. If the main oil circuit leaks oil outside the system, it indicates that it is the fault of weak boom lifting, find out the cause of oil leakage along the oil trace and eliminate it.
(2) Check the oil liquid in the oil tank. If the oil is seriously insufficient or there are too many bubbles, it is due to the slow lifting of the boom caused by the insufficient pressure of the main oil circuit. Add oil to make the liquid level meet the height requirements. If there are too many bubbles, the oil circuit at the swivel may be connected with the air circuit, and the swivel sealing ring should be replaced. If the oil is oxidized and deteriorated, it is dark brown and gives off a bad smell, indicating that the oil is deteriorated and should be replaced.
(3) Check the oil temperature. If the oil temperature of the system exceeds 80 ℃, it indicates that it is the cause of slow boom lifting and should be cooled. If the fault disappears after cooling, it proves that the radiator has poor heat dissipation or the continuous working time under heavy load is too long. In addition, if it works normally when the oil temperature is low and the boom lifting speed is slow when the oil temperature is high, it indicates that the oil quality is deteriorated or the hydraulic components of the system are worn, which reduces the system efficiency. The former mostly occurs in the service life. The latter mostly occurs in the depletion period.
(4) Check the main safety valve. If the pressure of the adjusting stud of the safety valve rises to the specified value (the pressure changes by 2.352mpa every turn) and the boom lifting speed is normal, it is caused by improper adjustment of the main safety valve. If the adjustment is invalid, it indicates that the valve core of the main safety valve is stuck in the open position or not tightly closed. It should be removed for inspection and troubleshooting. If the pressure regulating spring is broken, it shall be replaced.
(5) When adjusting the main safety valve, the pressure regulating stud is screwed in every turn, but the pressure does not increase (23.52mpa), indicating that the oil pump is faulty. If the boom lifting is slow and the fault occurs in the early stage (running in period), it indicates that there is air leakage in the oil suction passage; If it occurs in the wear out period, it proves that the oil pump is seriously worn and the pump oil efficiency is low, it shall be repaired or replaced.
(6) Check the oil cylinder. If the boom drops obviously automatically when the control valve is in the middle position after the oil cylinder is lifted, it may be that the oil cylinder is poorly sealed, the oil cylinder safety valve is not tightly closed, the oil pipe is leaking, and the control valve is leaking. Then find out the cause and eliminate the symptoms. If the slow lifting of the oil cylinder occurs in the early stage, most of them are likely to be damaged when assembling the oil cylinder; It is also possible that the mechanical impurities (metal chips, sand, etc.) during manufacturing are not removed during assembly, and the safety valve core or one-way valve is stuck in the open position, affecting the closing of the valve core; The pipe joint is loose and the sealing ring is damaged, resulting in oil leakage. All the above reasons can cause the pressure drop in the hydraulic system, resulting in slow boom lifting. Further, find out the causes and eliminate them. If the set pressure of the safety valve of the boom cylinder is lower than the specified value, it shall be adjusted. The method is to screw out the screw plug and increase the pressure on the spring pad. The cause analysis, diagnosis and troubleshooting methods of bucket cylinder are basically the same as those of boom cylinder.
