The main Control Valve was removed for repairs, but upon reinstallation, issues arose when attempting to lift the machine boom. The coordination between components proved inconsistent, making leveling operations nearly impossible. Despite replacing the hydraulic pump, handle assembly, and seals for the main arm cylinder, the problem persisted. Over three months passed without resolution, leaving the equipment inoperable.
To address this, I contacted professional distributors for assistance. During my on-site inspection, I noticed the large arm's lifting speed was slower than expected. Performance tests revealed the large arm took 4.85 seconds to lift, while the forearm and bucket performed normally. However, when both arms were used together, the forearm moved faster than usual, while the large arm struggled to move at all. This led me to suspect an issue with the combined action of the two arms.
Further testing showed that when the large arm lifted, Pump 2 registered a pressure of 30MPa, while Pump 1 remained at only 4MPa. This indicated no confluence between the two pumps during the lifting action. Upon inspecting the logic valve related to the main arm’s joint operation, I discovered an incorrect connection between the oil pipe pb and dr5. Even after correcting this error, the issue persisted, with Pump 1 still showing no pressure when the large arm lifted.
Analyzing the schematic, I suspected the problem might lie with the pilot selection valve or the merging/cutting solenoid valve for the large arm. Inspection confirmed that the merging/cutting solenoid valve was stuck in the closed position instead of its normal open state. Cleaning and resetting the valve seemed to resolve the issue initially, but further measurements revealed the pressure at the logic valve pb oil port was still zero when the large arm lifted. Interestingly, when lowering the arm, the pressure there was 4MPa, suggesting an incorrect oil line connection.
Upon closer examination, I identified a misinstalled high-arm oil line at the shuttle valve block. Correcting this mistake normalized the pressure at the logic valve pb oil port. However, even after these adjustments, the large arm’s lifting speed in combination actions remained sluggish. Testing the forearm fusion valve revealed a pressure of 0MPa when the large arm lifted, indicating the forearm fusion had not been properly disconnected. Further investigation showed the 2px hose of the forearm fusion valve was incorrectly connected to the main control valve dr1 oil port.
Ultimately, it became clear that the main arm merging solenoid valve had been improperly reconnected during disassembly and cleaning. With the help of professional distributor engineers, we corrected the hydraulic oil lines. During subsequent performance tests, the large arm achieved a lifting time of just 2.8 seconds, fully restoring its functionality.
In conclusion, engaging experienced distributors is crucial for such repairs. It is imperative to avoid overconfidence when handling hydraulic oil lines—always mark connections properly to prevent costly mistakes. By doing so, we can avoid unnecessary complications and financial losses!
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