In the hydraulic system, the flow of liquid in the pipeline is often due to the rapid change and the valve mouth suddenly closed in the pipeline to form a high peak pressure, this phenomenon is called hydraulic impact.

Hazards of hydraulic impact:

1 impact pressure may be higher than the normal operating pressure of 3-4 times, so that the system components, piping, instrumentation, etc..

2. The impact pressure of 2 impact pressure relay false signal, interfere with the normal work of the hydraulic system, affect the stability and reliability of hydraulic systems.

3 cause vibration and noise, loose joints. Caused by oil leakage, pressure regulating valve pressure changes, flow control valve to adjust the flow of change; affect the normal operation of the system.

Causes of hydraulic impact:

1 pipeline valve port closed quickly when the hydraulic impact.

2 the moving part is suddenly stopped by the high speed motion, and the pressure impact (inertia impact) is produced.

General methods for preventing hydraulic shock:

For the pressure drop caused by the sudden closure of the valve port, the following measures may be taken to eliminate or mitigate:

1 slow down the speed of the valve, that is, to increase the commutation time. Such as the use of DC electromagnetic valve is smaller than the AC hydraulic shock; gear pump with electro-hydraulic reversing valve with damping by adjusting the damping and control pilot valve pressure and flow to slow down the main spool valve commutation (off) speed, the hydraulic valve is similar.

2 increase the diameter, the velocity decreases, in order to reduce the impact pressure, shorten the length, to avoid unnecessary bends; or the hose is effective.

3 slow down the flow of liquid before the valve is completely closed. For example, improved structure valve control valve side, namely a rectangular or V shaped grooves in the spool edge, or tapered (half cone angle of 2-5 DEG) than the throttle cone angle control, hydraulic impact is greatly reduced; on the external grinder, take the prefabricated reversing valve then, the main valve to jump to the middle position, working hydraulic cylinders to the left and the right cavity into the instantaneous pressure oil (main valve type P), such as Taiwan without the impact of the steady stop; plane grinder worktable can adopt H type reversing valve, when the valve after the jump in the middle position, liquid the left and right cylinder two chamber through the oil pool and exchange, can reduce the braking shock pressure.