1. Model: Hitachi ZX240-3
2. Anomaly investigation:
① When the engine is idling at high speed, the boom will naturally descend.
②When the engine is idling at a low speed, the main pole stops and descends naturally, and the rotation stop is not released and the rotation operation will slip and drag.
3. Analysis of the cause of the failure:
(1) The pilot pump pressure at high speed idling is below 40 kg f/m2.
(2) The pilot pressure when idling at low speed is below 20 kg f/cm?.
(3) The pressure of the H/V release port Pic of the high-speed idling time control valve arm H/V is 2.5 kg f/cm?
(When there is 2.5 kg f/cnP in the Pic when there is no load, the boom will naturally not drop).
It can be judged that when the pilot pressure goes to the drain line, it is estimated that the pilot pressure is low and the pressure at the boom H/V release port is too high when the pressure at the boom H/V release port is 2.5 kg, and the drain flow rate will increase.
(4) Since on the hydraulic circuit, the drain circuit of the remote control valve for operation and the drain circuit of the collective valve for rotation stop braking are common, it can be judged that the pilot pressure of the collective valve for rotation stop braking has reached The drain line is gone.
(5) Pull out the hose from the port P of the manifold valve, and the boom will no longer fall naturally, so the reason is set to be the failure of the manifold valve.
4. Troubleshooting method:
(1) An abnormality caused by the connecting rod (line) from the P port to the T port in the manifold valve for stopping the rotation.
(2) Replace the manifold valve and repair it.
Summary: In daily work, the excavator must operate smoothly every time the boom is raised and lowered. Therefore, when the excavator has the above failures, it needs to be stopped for inspection. The so-called sharpening does not accidentally chop wood, only the machine Your efficiency will be high if it runs well.
