SCS1000A-CC0100CF0070#Main variable amplitude lowering action is slow.

On June 26, 2025, a SCS1000A crawler crane from Singapore, with equipment number CC0100CF0070#, had been in operation for 236 hours. The crane’s main boom lifting action was normal, but the lowering action was extremely slow.

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- Commodity name: SCS1000A-CC0100CF0070#Main variable amplitude lowering action is slow.
On June 26, 2025, a SCS1000A crawler crane from Singapore, with equipment number CC0100CF0070#, had been in operation for 236 hours. The crane’s main boom lifting action was normal, but the lowering action was extremely slow.

Fault phenomenon:

On June 26, 2025, a SCS1000A crawler crane from Singapore, with equipment number CC0100CF0070#, had been in operation for 236 hours. The crane’s main boom lifting action was normal, but its lowering action was extremely slow.

Troubleshooting Approach ：

Possible factors causing the slow downward movement of the main boom include electrical and hydraulic issues.

1. The pressure at the lower end of the main amplitude handle is too low.

2. The pressure sensor or wiring connection at the lower end of the main amplitude handle is abnormal.

3. The main variable-amplitude lowering proportional solenoid valve is malfunctioning.

4. The main amplitude drop and overflow pressure are too low.

The basic principle of the main amplitude reduction action.

1. Electronically controlled positive-flow control: The displacement of the main pump is directly proportional to the control current.

2. The main variable-amplitude hoisting speed is related to the handle opening degree, and the handle opening degree affects the sampling of handle pressure.

3. The handle pressure value further influences the control current of the main pump and the main valve.

In the diagram, number 8 is the main boom-lowering overflow valve, and number 16 is the main boom-lowering proportional solenoid valve.

The positions of the main variable-amplitude rising and falling proportional solenoid valves, as well as the main valve.

Troubleshooting process:

1. According to on-site feedback, the boom lifts normally, and the boom lowers with proper movement without any pressure buildup. The only issue is that the movements are slow, which indicates that the brake can fully disengage.

2. During on-site service inspection, the IO interface was checked, and the pressures at both the upward and downward ends of the main boom lift handle were found to be around 30 bar, indicating that the pressure sensor for the boom-lowering handle and its associated wiring are functioning normally.

3. When the arm-lifting and arm-lowering operations are performed, if the AD values fed back by the main pump both hover around 480, it can be determined that, in both the lifting and lowering states, the main pump’s displacement meets the requirements for arm-lowering.

4. Check the IO interface and verify the feedback status of the AD value for the solenoid valve controlling the main amplitude reduction ratio; the value should be around 400. This basically confirms that the wiring of this proportional solenoid valve is functioning properly.

5. Remove the main amplitude-reduction proportional solenoid valve from the main valve, clean it using a spray cleaner, and after reinstalling it, the main amplitude-reduction actuator’s speed returns to normal.

Troubleshooting Summary:

Currently, whether it's the SCS series or the SCA series crawler cranes, electrical systems play a very significant role. Before troubleshooting, it’s essential to thoroughly verify that all electrical conditions required for each movement are met. Only after confirming that there are no electrical abnormalities should you proceed to address hydraulic issues—this approach ensures quick and efficient resolution of equipment malfunctions and also helps prevent unnecessary contamination of hydraulic fluids.