How to solve the slow lifting of the long reach front of the excavator

Diagnosis and elimination

If the hydraulic working device moves slowly, it indicates that the failure of the long reach front cylinder to lift slowly lies in the main oil supply or the 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 lifting is weak in the boom branch.

1. Visual inspection of leakage outside the main oil circuit. If there are oil traces leaking out of the system in the main oil circuit, it indicates the failure of the long reach front.

2. Check the oil liquid in the oil tank. If the oil is severely insufficient or there are too many bubbles, it is caused by the insufficient pressure of the main oil circuit to raise the boom slowly. Oil should be added to make the liquid level meet the height requirements. If there are too many bubbles, it may be that the oil circuit and the air circuit at the rotary joint are connected, and the rotary joint sealing ring should be replaced. If the oil is oxidized and deteriorates, it is dark brown and emits an odor, indicating that the oil has deteriorated and should be replaced.

3. Check the oil temperature. If the oil temperature of the system exceeds 80°C, it indicates the cause of the slow lifting of the long reach front boom, and it should be cooled. If the fault disappears after cooling, it proves that the radiator has poor heat dissipation or the continuous working time of 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 efficiency of the system. The former mostly occurs during the use period. The latter mostly occurs during the wastage period.

4. Check the main safety valve. If the safety valve adjusting stud is screwed in (the pressure changes 2.352MPa per rotation), the pressure rises to the specified value, and the extension speed of the long reach front boom is normal, it is caused by improper main safety adjustment.

If the adjustment is invalid, it indicates that the spool of the main safety valve is stuck in the open position or is not tightly closed. It should be removed for inspection and ruled out. If the pressure regulating spring is broken, it should be replaced.

5. When adjusting the main safety valve, every time the pressure regulating stud is screwed in, the pressure does not increase (23.52MPa), indicating that the oil pump is malfunctioning. If the slow boom of the excavator boom occurs in the early stage (run-in period), it proves that there is a leak in the oil suction channel; if it occurs in the wear period, it proves that the oil pump is severely worn and the pump efficiency is low, and it should be repaired or replaced.

6. Check the oil cylinder. If the control valve is in the neutral position after the oil cylinder is lifted, the long reach front boom will automatically drop obviously. It may be that the oil cylinder is not well sealed, the safety valve of the oil cylinder is not closed tightly, and the oil pipe leakage control valve is leaking. Find out the cause and rule out the symptoms.

If the cylinder lifting slowly occurs in the early stage, most of the seals are likely to be damaged during the assembly of the cylinder; it is also possible that the mechanical impurities (metal chips, sand, etc.) during the manufacturing process have not been removed during the assembly. The safety valve spool or the one-way The valve stuck in the open position affects the closing of the spool; the pipe joint connection is loose and the sealing ring is damaged and oil leaks. The above reasons can cause the pressure in the hydraulic system to drop, causing the excavator's boom to rise slowly. The cause should be further investigated and eliminated.

If the safety valve setting pressure of the long reach front boom cylinder is lower than the specified value, it should be adjusted. The method is: unscrew the screw plug, and increase the cushion in the spring to increase the pressure (for every 1mm increase in the thickness of the gasket, the pressure can increase by 2.45MPa). Bucket cylinder failure phenomenon, cause analysis, diagnosis and troubleshooting methods.