A pressure control failure

(1) The system is weak. During the operation of the production line, the system pressure suddenly drops to zero and cannot be adjusted. The causes of this failure may be: the damping of the relief valve is blocked; there are foreign matters on the sealing surface of the relief valve; the main valve core of the relief valve is stuck in the open position; the electromagnet of the unloading reversing valve is burnt out, the wire is broken or the electrical signal is not sent out, etc. Obturator

(2) The system pressure is not high. This situation is generally caused by internal leakage. The causes of the failure can be the wear of the hydraulic pump, forming a gap; the wear of the main valve core and the mating surface of the relief valve, reducing the control pressure of the relief valve; the wear of the actuator of the hydraulic cylinder or the hydraulic motor or the damage of the seal; the cracks in the relevant valves and valve plates in the system, forming a leakage. The above reasons will lead to the system can not adjust the pressure, and eventually make the system pressure drop.

(3) The system pressure is high and cannot be adjusted. This situation is usually caused by overflow valve failure. When the main valve core is stuck or rusted in the closed position, the system pressure will rise and cannot be adjusted. When the pilot control oil circuit of the relief valve is blocked, the control pressure will increase sharply, and the system pressure will also increase suddenly. This generation of investigators

(4) The system pressure is unstable. The main reasons are: the overflow valve is worn, which causes internal leakage; the overflow valve is mixed with human and foreign matters; the hydraulic oil is mixed with air, which causes bubbles to break when the system pressure is high; the guide rail is not installed and lubricated properly, which causes uneven load; the parts in the hydraulic pump are worn; the plunger type hydraulic motor has void and collision, etc.

(5) Unloading out of control. The so-called unloading out of control is the phenomenon that the system pressure is not zero when the hydraulic system uses the relief valve to unload. The main reason is that the main valve core of the relief valve can not be fully opened; when the directional valve is stuck, it can not be fully opened or the return spring of the directional valve is broken, the system pressure can not be unloaded normally.

If it is a M-type directional valve, the reverse installation of directional valve and the broken return spring of directional valve cause the valve core not to return to the middle position, the system will not unload. In addition, the proportional pressure valve automatically unloads when the control signal is not received. If the proportional electromagnet gets an unexpected electrical signal, the system pressure will not be unloaded naturally.

B. It is caused by the failure of speed control.