The tacit cooperation between the large and small arms of the excavator is the prerequisite for the completion of the project with quality and quantity. Every action can be smoothly deployed and retracted to ensure that it can be completed quickly without delaying the construction time.
Since the upper and lower arm movements are so important, you can imagine that once there is an abnormal boom movement, or the combined movements of the upper and lower arms cannot start, not only the operation of the hand is limited, but also the problem of stopping the machine to repair the machine. Today I will tell you What I shared is the abnormal failure of the combined action of the Liebherr repair and excavator, and I hope to help everyone.
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Failure phenomenon
When a Liebherr repairing excavator is working on level ground, the operator responds to the combined action of the boom and the second boom. The boom can’t work, but if the boom is working alone, the action is normal. This kind of malfunction is encountered for the first time by the machine. , And the operation is very delayed and crappy, so I got a maintenance master to start the overhaul.
Failure cause analysis
After the maintenance master arrived at the site, he tried the machine repeatedly, clarified the operation and phenomenon when the failure occurred, and then began to analyze the reasons for the failure phenomenon basically as follows:
First: The common cause of failure is the failure of the machine's high-pressure sensor and the boom pressure switch.
Second: The pump control system is faulty, and the maintenance is relatively troublesome.
Third: The pilot pressure or secondary pilot pressure is low, and the inspection is relatively simple.
Troubleshooting
1. The maintenance of faults follows the process from simple to difficult, so first observe the instrument carefully, and find no fault code or abnormal alarm mark, and then make sure that the high pressure sensors of pump 1 and pump 2 are working normally, and the pressure switches of the boom and the second arm are also No abnormalities, so the electrical system problems are ruled out first.
2. After performing various pressure observations and tests, it is found that the output pressure of pump 1 and pump 2 is 345Kg, and the control pressure is 39Kg. According to the pressure, the machine can walk left and right without deviation, and it is normal and powerful to walk alone, so the flow of pump 1 and pump 2 are basically the same, which can eliminate the abnormality of the pump control system.
3. The secondary pilot pressure of the boom is 36Kg and the secondary pilot pressure of the second arm is 36Kg measured by the test meter. Therefore, it is determined that the secondary pilot pressure is normal when the boom and the second arm act independently, indicating that the handle output pressure is normal. , The distributor has no internal leakage. In the combined action of the boom and the second arm, the measured secondary pilot pressure of the boom is 13Kg, and the secondary pilot pressure is much lower than the normal value.
Fault handling
1. At this time, the schematic diagram comes in handy, because the boom and the second arm do a compound action, the SK outlet is connected with the pilot oil of the boom lifting, the oil pressure at the SK outlet is also 15Kg, and the signal valve SK outlet outputs 2 The secondary pilot oil controls the bucket flow control valve, so it can be judged that the bucket flow control valve spool in the signal valve is faulty.
2. Check the signal valve. It is found that the front end of the bucket flow control spool is severely worn. When it moves, the oil from the boom lift outlet and the SK outlet leaks into the oil return channel, causing the output pressure to drop to 13Kg, causing the combined action boom to fail. Up.
3. Repair the signal valve hole, reconfigure the spool, and re-test the boom lift secondary pilot pressure and SK outlet pressure after the processing is ready to reach 35Kg, and the failure phenomenon of the re-testing will all disappear.
to sum up
Under normal circumstances, the signal valve material is made of aluminum, and the hardness of the valve body and valve core material is not high, so if the hydraulic oil has impurities, it will cause the valve core to jam or strain and cause the control pressure to be inaccurate. Therefore, it is necessary to observe frequently and maintain on time to ensure the cleanliness of the hydraulic oil.
