How to deal with the forearm drop of the excavator long reach front

If the excavator has the phenomenon that the long reach front forearm automatically drops quickly during operation, it is needless to say that the first thing that affects is the construction efficiency. The forearm pops up and then falls quickly, making the driver feel very mad, and it is prone to safety accidents if the operation is not good. Today I will share with you how to troubleshoot the forearm drop.

The malfunctioning equipment is a CAT345 long reach front excavator. When the equipment is parked, the long reach front forearm cylinder will automatically drop, and the drop exceeds the normal falling distance. Other actions of the excavator are normal.

Cause Of Issue

According to the working principle of the hydraulic system of the long reach front forearm, the forearm action oil inlet circuit is mainly the hydraulic oil from the hydraulic pump to the main control valve, and then enters the hydraulic cylinder after passing through the pipeline safety valve and the holding valve, which causes the forearm to fall. The main reasons are:

1. The safety relief valve of the control arm oil cylinder is faulty, the valve core is blocked or worn 2. The oil seal of the arm oil cylinder is worn and damaged 3. The arm holding valve spool or spring is worn and stuck, resulting in internal pressure leakage

Troubleshooting

1. Check the safety overflow valve controlling the extended arm forearm cylinder. Disassembly and inspection did not find any wear. After cleaning the spool and replacing it with other overflow valves, the test failure still persists, and the safety overflow valve problem is eliminated.

2. The forearm cylinder was disassembled and inspected by the bottom of the forearm cylinder. No oil leakage was found, and the cylinder and oil seal were not found to be worn.

3. The inspector adjusts the working device to the maximum radius, puts the top of the boom horizontally, then turns off the engine, and then locks the safety lock lever to release the pressure in the hydraulic oil tank.

4. After inspecting the forearm holding valve of the long reach front, it is found that the open oil port of the pilot hose connected to the holding valve is leaking. The valve core is found to be worn out after the holding valve is disassembled. It is judged that the arm holding valve is faulty.

Fault handling

After replacing the long reach front holding valve, the equipment returned to normal and the fault was eliminated.

Summarize

The large and small arms of the long reach front excavator are very high-intensity work every day, and it is normal for them to malfunction. I remind everyone that when encountering such faults, start from simple to complex troubleshooting. Most of them are caused by internal leakage of the oil seal and the oil cylinder, which causes the arm to fall. Therefore, pay more attention to maintenance at ordinary times. If the oil seal is damaged, replace it in time.