Common Fault Analysis and Improvement Suggestions for Hydraulic Hooks

1、 Common fault types and cause analysis

Automatic sliding of hook (sliding hook)

Hydraulic system internal leakage: Hydraulic pump, balance valve or hydraulic cylinder internal leakage causes insufficient pressure, unable to maintain load. For example, if the pressure of a worn hydraulic pump is lower than the rated value (such as 250-260kg/cm ² dropping to 190kg/cm ²), the hydraulic pump needs to be replaced.

Brake failure: Brake pad wear, cracks, or excessive clearance (such as exceeding 0.4mm), resulting in insufficient braking force. The brake pads need to be replaced and the clearance adjusted.

One way damping valve failure: The valve seat spring is broken or the throttle fails, causing premature release of the brake. The one-way damping valve needs to be disassembled, inspected, and replaced.

Balance valve damage: The spring inside the balance valve stem is broken, causing insufficient back pressure in the return oil and allowing the load to fall freely. The balance valve needs to be replaced.

Incorrect connection of hydraulic oil pipe: The balance valve control oil pipe is connected incorrectly, resulting in abnormal operation. Reconnect the oil pipe according to the hydraulic schematic diagram.

Slow or weak movements

Insufficient oil discharge of hydraulic pump: Improper adjustment of the variable displacement pump's inclined plate angle or failure of the differential piston seal of the servo mechanism, resulting in a decrease in oil discharge volume. Need to repair the servo variable mechanism and replace the seals.

Insufficient system pressure: The pressure regulating spring of the overflow valve is damaged or the sealing of the cone valve fails, resulting in the system pressure being lower than the rated value. The cone valve needs to be ground and the pressure regulating spring needs to be replaced.

Hydraulic oil contamination: The oil deteriorates or impurities enter the system, causing valve body jamming or damping hole blockage. The hydraulic system needs to be cleaned and the hydraulic oil needs to be replaced.

Abnormal noise or vibration

Mechanical wear: Fatigue failure of sealing surfaces and spring steel plates of hydraulic variable displacement pumps or oil motors, resulting in metal impact noise. Wear parts need to be replaced and the sealing surface repaired.

Clutch malfunction: The clutch friction plate is deformed or the clearance is too small (such as less than 5-6mm), causing difficulty in rotation. The clutch clearance needs to be adjusted or the friction plate needs to be replaced.

Loose components: The piston rod nuts, support rubber pads, and other components are loose and need to be tightened and replaced with aging parts.

2、 Improvement suggestions and solutions

Targeted maintenance and component replacement

Hydraulic pump and balance valve: Regularly check the system pressure, and replace the hydraulic pump or balance valve if the pressure is insufficient. For example, troubleshooting of the QY8 truck crane after replacing the hydraulic pump.

Brake and damping valve: Check the wear of the brake pads to ensure that the contact area is not less than 70%; Disassemble and inspect the one-way damping valve and replace the broken spring.

Clutch and friction plate: Adjust the clutch clearance to 5-6mm. If the friction plate deforms, replace it with a new part.

System upgrade and optimization

Hydraulic oil management: Regularly replace hydraulic oil (such as L-HM 46 anti-wear hydraulic oil), clean the oil tank and filter to prevent oil contamination.

Seal upgrade: Using high-temperature resistant and wear-resistant sealing materials (such as polytetrafluoroethylene) to extend the life of the seal.

Calibration of electronic control system: Software upgrade of intelligent electronic control system to optimize shock absorption response speed and action coordination.

Operation and maintenance standards

Regular inspection: Check the hydraulic oil level, oil quality, and oil leakage every 200 hours; Clean the hydraulic oil radiator and sediment at the bottom of the oil tank every 500 hours.

Adjustment of driving habits: Avoid passing through deep pits or speed bumps at high speeds, and reduce the impact load of shock absorbers under extreme working conditions.

Environmental protection: Vehicles driving in saline alkali areas should undergo chassis rust prevention treatment every 3 years to extend the lifespan of rubber components.

Preventive maintenance strategy

Graded maintenance: Develop a maintenance plan based on the severity of the fault. If there is a mild oil leak, the replacement of the assembly can be postponed, and if there is a severe fault, it needs to be repaired immediately.

Component selection: Prioritize the use of original factory parts or internationally certified parts (such as KYB, Sachs) to balance performance and cost.

Training and recording: Train operators on fault phenomena and handling methods, establish maintenance records to track equipment lifespan and fault patterns.

3、 Typical Case Analysis

Case 1: QY8 Truck Crane Sliding Hook

Fault phenomenon: The hook automatically slides down when lifting heavy objects.

Reason: Insufficient system pressure caused by hydraulic pump leakage.

Solution: Replace the hydraulic pump and adjust the system pressure to the rated value, and troubleshoot.

Case 2: LIEBHERR's suspension action lags behind

Fault phenomenon: After resetting the joystick to zero, the boom continues to rotate.

Reason: The differential piston sealing ring of the servo variable mechanism is worn, resulting in delayed oil discharge of the hydraulic pump.

Solution: Disassemble and inspect the servo variable mechanism and replace the sealing ring to restore normal operation of the equipment.

The main equipment produced by Hebei Makita: stage electric hoist, electric chian hoist, wire rope electric hoist，Hand chain hoist, lever hoist, pneumatic hoist and other lifting equipment