A 20t crawler excavator was found to have the boom falling automatically. Some people believe that the one-way throttle valve of boom cylinder is stuck due to abnormal wear. This causes the boom to have this fault. But this reason is not sufficient. First, the one-way throttle valve is used to prevent the boom from falling or falling at an excessive speed. Only when these two kinds of faults occur, the maintenance personnel will take the initiative to check the valve core. Second, if the reversing valve and overflow valve are not faulty. Only the one-way throttle valve can not affect the oil in the lower chamber of the boom cylinder. It will not cause the boom to fall automatically.
