1. Improper adjustment of hydraulic components, such as: oil pump, oil motor, sequence valve, directional valve, overflow all over the world, unloading valve, balance valve pressure and flow adjustment is not correct;
2. The sealing element is damaged or the impurity makes the hydraulic element unable to work normally;
3, hydraulic machine components wear or damage, such as valve components seal failure, spring failure, clearance, etc;
4. Failure of the control mechanism (electrical appliance), such as: relay failure, poor contact or damage of the button, incorrect installation of the electromagnet, misconnection of the motor phase line and other causes of hydraulic component misoperation or program error;
5. Failure of auxiliary mechanism, such as improper adjustment or damage of limit switch position, damage of pressure gauge, damage or false signal of pressure relay, filter problem of fuel tank, etc.