1. The control mechanism of the arm operated slide valve is not adjusted properly, so that the arm operated slide valve is not completely in the middle, should check whether the control mechanism is adjusted in the middle.
2. If the piston seal ring of the boom cylinder is damaged or the cylinder barrel is damaged, which causes serious internal leakage of the cylinder, the seal should be replaced or the boom cylinder should be replaced.
3. distribution valve arm slide valve stem wear too much, seal is not strict, should replace the distribution valve.
4. the safety valve on the distribution valve is damaged, causing the leakage of the valve.
The method of judging the automatic drop of the valve or cylinder caused by the distribution valve or the oil cylinder is to lift the arm to the highest position, to bring the arm stem to the middle, and to hear the sound of the oil cylinder at the hearing arm. If there is a sound of "bang and bang", the valve has a fault. If there is no noise, it may be the problem of the oil cylinder and the oil should be removed the cylinder.
