How many ways can pressure regulating valve avoid cavitation?

For high pressure and small flow regulating valves, a series of problems caused by high pressure and high pressure difference must also be considered. For example, the actuator must have enough output force to overcome the unbalanced force of the medium, the strength problem of the valve element, the high-pressure sealing problem, and most importantly, the material and processing problems of the valve core and valve seat.

The reasons for the damage of the valve core and valve seat of high-pressure regulating valve are very complicated, and the theories are different, but the common concern is the erosion phenomenon (also called velocity effect) caused by the movement of high-speed liquid (gas) flow relative to the valve core and valve seat and the cavitation phenomenon of liquid medium under high pressure difference. The damage form of the former is scour marks related to streamline, while the latter is sponge holes.

In the case of cavitation, if the materials of valve core and valve seat are not properly selected, the valve will be scrapped in a few days or months.

To solve the problem of cavitation, we should start with the methods to avoid cavitation and the anti-cavitation materials. There are several ways to avoid cavitation.

1. Improve the design of valve core and valve seat to make it have reasonable liquid velocity distribution and pressure distribution. For example, the small flow regulating valve adopts a narrow channel valve core and a valve seat. The taper of valve core and valve seat hole is very small, which is suitable for accurate control of flow under the condition of constant upstream pressure. Because this structure has the function of absorbing energy and reducing cavitation, it is reported that it is used for pressure drop of 4200 kg/cm2.

2. If conditions permit, aerate the liquid flow to partially or completely eliminate the low pressure area.

3. Valves are used in series to reduce the pressure drop of each valve.

4. Make the pressure difference before and after the valve lower than the maximum allowable pressure difference of medium cavitation at the inlet temperature of the regulating valve.

5. When the medium works in the "open flow" state, the allowable pressure difference is more than three times larger than that in the "closed flow" state.