How to solve the problem that the electronic control outriggers of a large-tonnage truck crane cannot be opened? Look here!

Fault diagnosis and handling

The first step

During the test drive, the horizontal movements of the left and right outriggers were normal, but there was no vertical movement. Additionally, the movements of other outriggers were observed to be normal.

Based on the above analysis, the fault should be from the left rear outrigger control valve to the vertical cylinder. Then, the possible causes of this fault may be:

① The solenoid valve must not be electrified.

② The solenoid valve is damaged;

③ The oil pipe is bent and blocked.

④ Fault of the insertable hydraulic lock;

⑤ Vertical cylinder failure.

Step Two

First, perform the left rear outrigger extension action. Check that the left rear outrigger extension solenoid valve is energized normally. Remove the solenoid valve coil for inspection and find that there is normal magnetic force. It is determined that the solenoid valve is normal. Because it is rather difficult to disassemble the valve core, the vertical oil cylinder connection oil pipe was removed. The pressure was tested and found to be normal, so faults ①②③ can be ruled out.

2. Remove the insertable hydraulic lock and upon inspection, it was found that the O-ring on the hydraulic lock was damaged. Replace it with a new O-ring and test run again, but the fault could not be eliminated.

When the hydraulic lock was removed again, it was found that it could not be disassembled for inspection. After replacing the new hydraulic lock, the outriggers operated normally during the test run. After several test runs, the outriggers could not be extended again. The hydraulic lock was removed for inspection and found to be normal.

4. It was suspected that the vertical oil cylinder was faulty. After disassembling and inspecting the vertical oil cylinder, no fault was found. It was decided to replace the vertical oil cylinder. However, the fault still existed after the replacement.

Step Three

1. Remove the vertical cylinder connection oil pipe again. During the test run, it was found that there was no pressure when the vertical cylinder was extended, but the pressure when it was retracted was normal. It was determined that the fault lay on the valve islands of the left and right outriggers.

The valve island was removed and the vertical bidirectional solenoid valve assembly was taken off. Upon inspection, it was found that the valve core could not move flexibly but was at the B port end. During cleaning, a small iron particle fell out of the valve core. After careful identification, it was found that this object was the valve needle of the previously broken insertable hydraulic lock. It was judged that the fault should be here and the solenoid valve core needed to be cleaned. After cleaning, the fault was solved.

Outriggers - Other fault phenomena and handling

Fault phenomenon ① : One of the legs is sinking vertically into the oil cylinder

This fault is mostly a fault of the vertical outrigger bidirectional hydraulic lock. It can be eliminated by swapping it with any other non-faulty vertical outrigger bidirectional hydraulic lock. Before the swapping operation, make sure to extend the piston rod of the corresponding vertical outrigger cylinder. The replacement should be carried out under the condition that the outrigger foot plate is about to touch the ground and has not been subjected to force.

Fault phenomenon ② : When one leg of the vertical oil cylinder is under heavy load, it sinks. After no force is applied, it rebounds and floats

This fault is mostly related to the vertical outrigger cylinder. It can basically be determined that there is internal leakage at the piston of the cylinder. Disassembly and replacement of the seal are required. In particularly severe cases of cylinder pulling, the vertical outrigger cylinder assembly needs to be replaced.

Fault phenomenon ③ : Multiple outriggers are sinking vertically to the oil cylinder

This malfunction may be due to the vertical outrigger cylinder swelling (commonly known as "big belly") or a fault in the lower control valve assembly. The pressure of the outrigger system can be detected first. When the peak pressure is within the safety value, the problem with the oil cylinder can be temporarily ruled out. That is to say, it's time to replace the lower control valve assembly.

Fault phenomenon ④ : Loose joints cause oil leakage in the oil circuit

Handling method: a. Locate the part and tighten it; b. The seal is damaged and should be replaced. c. If there are cracks in the pipeline, it should be replaced or welded.

Fault phenomenon ⑤ : The outriggers fail to extend and retract. The bidirectional hydraulic lock malfunctions, and the plunger inside the lock is stuck and does not move

Handling method: a. Disassembly, cleaning, installation and adjustment are required; b. The plunger is severely worn and a new hydraulic lock should be replaced.

Fault phenomenon ⑥ : When the hydraulic small crane is lifting a load, the outriggers automatically retract

Reason one: The one-way valve in the bidirectional hydraulic lock has poor sealing performance

Solution: It should be disassembled for inspection, cleaned, and then reinstalled and adjusted.

Reason two: Internal leakage of the hydraulic cylinder

Solution: The seal on the inspection piston must be removed, replaced with a new one and then reinstalled.