The action of the excavator boom is one of the most frequently used actions in the daily construction process. If the boom is lifted slowly and powerlessly, it is basically declared that it needs to be stopped for repair. Let's take a look at a case of how to solve the problem of slow and weak boom lifting!
Fault details:
A CAT 320d excavator was found to be weak and slow in boom lifting during recent work
The steps for on-site inspection of faults are as follows:
(1) Tooling inspection: check whether the working device does not match the model. If it does not match, it will cause weak boom lifting and replace it
(2) Appearance inspection: check the leakage outside the main oil circuit of the boom branch and boom pilot branch. If the branch leaks oil outside the system, it indicates that it is the fault of weak boom lifting, find out the cause of the oil leakage along the oil trace and eliminate it
(3) Noise inspection: check whether the boom branch and boom pilot branch have noise. If there is noise, it indicates that there is blockage or internal leakage in the branch. Find out the cause along with the noise and eliminate it
(4) Check the oil cylinder. If the control valve is in the middle position after the oil cylinder is lifted, the boom has obvious automatic lowering, which may be due to poor sealing of the oil cylinder, loose closing of the oil cylinder safety valve, oil leakage of the oil pipe, and oil leakage of the control valve. Further, find out the causes and eliminate the symptoms
3. Confirm the cause of the fault
Check the overflow pressure of boom pipeline safety valve as follows:
(1) To increase the pressure of the main safety valve of the excavator, loosen the lock nut of the main safety valve, turn the adjusting screw clockwise for one or half turn,
(2) Start the excavator, set the engine speed adjustment knob to the position of gear 10, and lift the boom to the machine holding state
(3) By observing the pump pressure displayed by the monitor, it is found that the pump pressure is 35000kpa, lower than 38000+1000-1500kpa, reaching a normal value
Therefore, it can be concluded that the failure of boom lifting is caused by the low pressure setting of the pipeline safety valve
4. Cause of maintenance failure
The steps for commissioning the overflow pressure of the boom pipeline safety valve are as follows:
(1) Loosen the lock nut on the pipeline safety valve;
(2) Rotate the adjusting nut clockwise to increase the set pressure of the pipeline safety valve (Note: the pressure change of the pipeline safety valve after one revolution is llookpa, and the angle of rotating the adjusting nut depends on the difference between the actual pressure of the pipeline and the expected pressure (38000+1000-1500kpa)
(3) Tighten the locknut on the line relief valve to 20 ± 2n m;
(4) After the pipeline safety valve is adjusted, the pressure of the main safety valve shall be adjusted back to 36000kpa (Note: when the pressure is reduced, it cannot be directly adjusted to the expected pressure, but it shall be adjusted to a half turn lower than the expected pressure and then adjusted to a half turn tighter, that is, the pressure of the safety valve can only be adjusted tightly, not loosely);
