Excavator boom cylinder is unstable due to boom valve core failure

A crawler excavator was found to have serious boom sinking. This will have a serious impact on the handling during operation. The operator responded that when the excavator lifted the boom, it would sink a certain distance. And it is weaker than before to use the bucket to support the excavator. This will prevent normal construction. This article will explain the troubleshooting process and reasons. For reference only.
1. The engineer found that the boom of the excavator sank obviously within a few minutes and found that the cylinder rod extended a lot. Use the bucket to support the excavator. However, the car body cannot be properly supported. Then check that the measured pressure of the front pump is normal.
2. Use the boom stick for composite action support. The excavator can be reluctantly supported. After shutdown, the sound of hydraulic oil pressure relief flow inside the left boom cylinder can be heard clearly.
3. The engineer first predicted that there was an internal fault in the left boom cylinder. The engineer removed the oil return filter element and found iron filings inside. Therefore, disassemble the left boom cylinder. Damage is found on the cylinder rod. After replace the cylinder, the fault of boom sinking is clear.
4. Use the bucket again to support the excavator. The rear pump pressure display is normal, but the body still cannot be properly supported. At this time, the combined action of stick and boom can support the body. Check the right boom cylinder and find no fault, and replace the overload overflow valve. The fault phenomenon remains unchanged.
5. The engineer speculated that there might be leakage in the regeneration check valve inside the boom spool. Replace the boom spool first. When the excavator is supported again, the body can be supported. The rear pump shows normal pressure. Subsequently, the boom spool was disassembled and the regeneration check valve was found to be broken. Therefore, it can be determined that the failure is caused by the failure of the regeneration check valve.
Therefore, the hydraulic oil tank must be carefully cleaned during the daily use of the excavator. Regularly replace new hydraulic oil, hydraulic oil filter element and new regeneration check valve.