The repair master arrived at the site based on the defect phenomenon and the relevant introduction of the hydraulic operating principle of the machine, and the preliminary recognition of the defect and the analysis of the reasons are as follows:
1. The machine has planned and added regeneration function in the forearm retracting oil circuit. A brief introduction to the benefits of the regeneration function is to prevent the forearm cylinder from extending too fast under the effect of the forearm’s own weight when the forearm is retracted. Cavitation in the cylinder constitutes an adverse effect. On the other hand, the continuous phenomenon of the forearm and the retraction speed of the traveling forearm must be avoided.
2. The key point is that this function is completed by the one-way valve in the ARM1 spool and the arm regeneration valve. With this visible defect, we also need to open the key around the two parts.
3. Return to the operating principle of the machine. When the owner chooses the excavation construction method, the regeneration valve spool is in the saving position and binds the oil return of the rod cavity of the cylinder. When the oil pressure of the rod cavity is higher than the oil pressure of the rodless cavity, the one-way valve in the ARM1 spool opens, so that the return oil from the rod cavity returns to the rodless cavity to end the regeneration function.
4. Therefore, after the above introduction, we will easily understand that if the regeneration valve spool cannot be in the saving position or the one-way valve in the ARM1 spool cannot be opened smoothly, the regeneration function in the arm circuit cannot be ended. Then form the forearm to produce continuity in a straight position.
Maintenance process of small excavator
After analyzing based on the above working principle, the engineer inspected the regeneration valve spool and the pilot oil circuit, and found no abnormal defects. The cause can be cleaned up immediately. When the repairer checked the check valve in the ARM1 spool, he found that the saving hole at the front end of the check valve was blocked by foreign matter, which caused the check valve to fail to open, which eventually caused this defect.
Small excavator treatment method
Since the defect of the saving hole was only caused by foreign matter blocking, and there were no other abnormal wear and other conditions, it was only necessary to completely clean the saving hole and then test the machine from the beginning. It was found that the continuous phenomenon of retracting the forearm did not reappear, indicating that the defect has been cleared.
