The front-mounted crane’s lifting attachments move slowly (including lateral movement and rotation).
Release time:
2025-11-27
Author:
Source:
Fault cause analysis:
1. The main pump is damaged, resulting in insufficient system pressure.
2. The multi-port overflow valve of the lifting device is damaged.
3. The lead feedback is abnormal.
4. The rotary valve block contains a stuck or damaged valve.
5. The solenoid valve of the main fuel supply valve is not energized or is not fully open.
The main pump is damaged, resulting in insufficient pressure in the system.
The spreader multi-pass overflow valve is damaged.
Abnormal pilot feedback
Valve stuck or damaged in the rotary valve block
The total oil valve solenoid valve did not receive power or did not open fully.
Troubleshooting Procedure / Repair Procedure:
1. When performing the lifting device extension operation, the pressure reading displayed on the screen is 18.5 MPa, which is within the normal range, ruling out a main pump failure.
2. Use a multimeter to check whether the voltage across the solenoid valve of the main fuel supply valve is normal. The solenoid valve plug should receive proper power—voltage should be 24V. Also, ensure that the valve spool is free from any sticking or jamming. If these conditions are met, the fault in the main fuel supply solenoid valve can be ruled out.
3. Use a pressure gauge to measure the pressure at the main oil supply valve of the lifting device, the anti-sway pressure, and the pressure in the lifting device’s multi-way manifold.
4. Clean the pilot valve block and the multi-way body of the lifting device, checking for any sticking spools in the valves. Also inspect the pressure-reducing valve (16 MPa) and the relief valve (28 MPa) for damage. After cleaning with diesel, confirm that all components are functioning normally.
5. When performing mobile counterweight adjustments and cabin movement pressurization, the pressure remains normal at 18.5 MPa, confirming that the feedback relief valve is functioning properly.
6. Inspect the solenoid valves and relief valves on the lifting gear’s rotary valve assembly. The lifting gear system is experiencing pressure buildup, but the pressure only reaches 8-9 MPa—while the normal pressure should be between 17 and 18 MPa. There is oil leakage between circuits, preventing the pressure from being established.
7. Judging from the pressure measurement results, the problem lay with the lifting device itself. So I started by examining the anti-sway valve block, checking each overflow valve, pressure-reducing valve, and solenoid valve. Eventually, I discovered that the brake solenoid valve was stuck, causing oil to leak between circuits and resulting in slow overall movement of the lifting device.
When the spool is extended, check the pressure value of 18.5 MPa from the display screen, which is normal, and rule out a main pump malfunction.
2. Use a multimeter to measure whether the voltage of the solenoid valve of the main oil supply valve is normal and whether the power supply to the solenoid valve plug is normal.
3. Use pressure gauges to measure the pressure of the spreader’s general oil supply valve, anti-pendulum pressure, and spreader’s multi-body pressure.
4. Clean the pilot valve block and the spool body with multi-pass channels. Check whether there are any spool hair clips. Verify that the pressure relief valve (16 MPa) and the overflow valve (28 MPa) are undamaged. Clean them with diesel and ensure that all components are in normal condition.
5. When the balance weight is moved and the cab shifts to relieve the pressure, the pressure returns to normal at 18.5 MPa, confirming that the feedback overflow valve is functioning properly.
6. Check the solenoid valve and overflow valve on the spool valve set. The spool system holds pressure, and the pressure is only 8-9 MPa. Based on the pressure measurement, the problem lies in the spool itself; therefore, we’ll start with the anti-swing valve block and check the overflow valve, pressure relief valve, and solenoid valve.
7. The final check brake solenoid valve is stuck, causing a continuous oil flow and slowing down the overall spool action. Rotary valve group.
Failure Summary / Principle & Experience Summary:
When dealing with hydraulic faults, it’s crucial to be meticulous and patient in your troubleshooting efforts. You need to keep your思路清晰 and approach the problem step by step—from simple to complex. Through this troubleshooting experience, you’ll be able to quickly identify the root cause of similar faults in the future.
When checking for hydraulic faults, it’s essential to be careful and patient during troubleshooting, clearly organizing your thoughts and proceeding from simple to complex issues. Through this troubleshooting process, we can quickly identify the root cause of future failures.
Rotary valve group
Lifting Gear Multi-Body Spreader
Brake solenoid valve
Pilot overflow valve 
Lifting device pressure, Spreader pressure
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