How Can We Prevent Valve Cavitation?

As some sounds can have a negative impact on the human body, some frequencies can also cause serious damage to industrial equipment. When the selected control valve increases the risk of cavitation, it will cause high noise and vibration to damage the internal and downstream pipes of the valve quickly. In addition, the high noise level usually causes vibration, which may damage pipes, instruments and other equipment. Therefore, how to avoid the influence of cavitation on the valve is a key problem.

1. Principle of Cavitation

As the time goes on, the parts of the valve will degenerate, and the cavitation will cause serious damage to the pipeline system. Most of the damage is accelerated by vibration and noise energy. Although this usually occurs in ball valves and rotary valves, it can also occur in a short v-ball valve with high recovery, especially in the piping downstream of the valve. When the stress of the valve is only one position, it is easy to produce cavitation, resulting in leakage of the valve piping and welding repairing.

If the cavitation occurs in the valve or downstream of the valve, the equipment in the cavitation area will be widely damaged. Frequent fault points are found in instruments, such as pressure gauge, transmitter, thermowell, flowmeter and sampling system. Actuators, positioners, limit switches and other structures with springs will suffer accelerated wearing. Mounting bracket, fastener and connector will be loose and invalid due to vibration. High amplitude vibration will also cause cracking and corrosion of metal valve parts and pipe walls. Scattered metal particles or corrosive chemical materials may contaminate the medium in the pipeline, which has a significant impact on the sanitary valve pipeline and high-purity pipeline medium.

2. Prevention of Cavitation

Valve shunting is to divide a large flow into several small flows. In the design of the valve flow path, the flow will pass through several parallel small openings. Because the size of cavitation bubble is calculated by the opening through which the flow passes, a smaller opening will make the bubble smaller, resulting in less noise and less damage.

Staged pressure reduction means that the valve is designed to have two or more regulating points in series. Therefore, it is not the whole pressure reduction in a single step, but several smaller steps. Less than individual pressure reduction can prevent the pressure in the constriction flow, thus reducing the vapor pressure of the liquid and eliminating the cavitation phenomenon of the valve.

In the process of valve modification, the pressure at the inlet of the valve and the pressure of the positioned control valve are high, so as to eliminate the cavitation problem. In addition, controlling the liquid temperature at the positioned control valve and reducing the vapor pressure by using the heat exchanger at the low temperature side can also help eliminate the cavitation problem.

In short, the valve cavitation can not only reduce the performance of the valve, but also damage the valve. There is also a risk of damage to downstream piping and equipment. Therefore, predicting cavitation and taking measures to eliminate it is the only way to protect the valve, so as to avoid the problem of expensive valve consumption.