An efficient solution to the problem that the dipper stick of doosan-9 excavator can only be retracted but not released
It is said that the arm of the excavator is as flexible and important as the arm of the transformer. It can be said that the arm plays a decisive role in whether the project can be completed with quality and quantity, so it has also become the "baby" in the eyes of the owners of the machine that can not break down
Recently, the maintenance master of the Doosan excavator received an urgent help message. The doosan-9 excavator of the owner of the machine encountered a failure that the stick can only be retracted but not released. The construction site has been in a semi stoppage state because of the sudden drop of the machine. It needs immediate maintenance
Fault phenomenon:
According to the description of the owner of doosan-9 excavator, the failure of the excavator was very sudden. The construction was OK the day before and everything was normal. As a result, the safety lock was opened after the vehicle was started the next day, and the problem that the stick could only be retracted but not released occurred
The reason for the failure that the dipper stick of doosan-9 excavator can only be retracted but not released
1. Internal leakage of oil cylinder
If the oil cylinder leaks internally, the overflow pressure of the jib will not be enough, and it will be weak whether it is retracted or released. Of course, it will also happen that it can only be retracted However, this situation can be eliminated by checking the pressure, and most of the fault phenomena are that the playback is unable or slow
2. Abnormal pilot pressure
If the pilot pressure of the boom extension is not enough, the control valve of the boom will not be opened or fully opened, affecting the flow and causing the boom extension to move slowly or immovably The possibility of this kind of reason is not very high, because the pilot pressure will not be insufficient in general
3. Stick valve core is stuck
According to the fault phenomenon, the above fault phenomenon will certainly occur when the stick valve core is stuck in the retracted state, which is also the most likely cause of the fault Because the valve element is at this position, the ignition engine cannot be started or it is difficult to start, so if there is an engine in this situation, it is basically this reason that the hydraulic oil will flow directly to the large chamber of the oil cylinder and the direction of the retraction of the small arm. But at the same time, it will also start under pressure, resulting in abnormal starting. Otherwise, the cause of this failure can be eliminated
4. Pilot handle failure
The possibility of failure of the pilot handle is also very high, because the pilot handle is stuck, which will certainly happen when it is opened or stuck at a certain position. Once the engine is on fire, the pilot lock will act when it is lowered In addition, when you extend in the opposite direction, you will not be able to extend if you are stuck by the retraction pilot pressure. Therefore, the probability of this is also very high
An efficient solution to the problem that the dipper stick of doosan-9 excavator can only be retracted but not released
Inspection process
1. Check whether the system pressure is normal
2. Check the pilot pressure and it is normal
3. Check whether the safety lock switch and the safety lock solenoid valve are normal
4. Check the idle core of the stick on the main valve for any damage, deformation and stagnation
5. Check the pilot pressure of the stick. When the safety lock is closed, there is pressure. When it is opened, there is no pressure. It is analyzed that the stick spool of the PPC valve is stuck and abnormal
6. A small scrap of iron was found stuck at the valve core during disassembly and inspection. After cleaning, the test run was normal after reassembly
Maintenance end
Because the fault analysis was very accurate, the inspection process was very smooth, and the owner eliminated all the faults without too much downtime. Everything was normal after the test run
