What is the Cavitation of the Valve? How to Eliminate it?

Valves are accessories in the piping system which are used to open and close the pipeline and control the flow direction of the conveying medium and so on. According to its function, it can be divided into regulating valve and so on.

 

The valve is used as the control component in the delivery system of fluid, and it has functions such as, regulation, diversion, prevention of back-flow, or pressure relief. Valves for control systems of fluid range from the shut-off valves which is the simplest to the various valves used in extremely complex systems. For example, the valves can be divided into gate valves, globe valves, check valves, ball valves, butterfly valves, water check valves, forged steel valves, knife gate valves and so on.

 

With the passage of time, the degradation of parts and components in the valve and the cavitation of the valve can cause damages to the pipeline system. Most of this damage is caused by the energy of vibration, which accelerates the the process of corrosion. The formation and collapse of the contracted flow and the bubble caused by vibrations with high levels of noise levels reflect the cavitation of the valve. Although it usually occurs in the valve body of the ball valve and rotary valve, it can actually occur in other valves such as in the pipe of the butterfly valve. When the force placed on the valve is from a position, cavitation is easy to occur. Hence, it is easy to leak in the connection of the pipe, and the valve is not suitable for the pipeline any more.

 

No matter where the cavitation occurs, the equipment in the cavitation zone will be extensively damaged. Vibrations in high amplitude can also crack and corrode the elements in metal valve and pipes. Metal particles or chemical materials which come from the damaged valve or pipes may contaminate the medium in the pipeline.

 

The way to eliminate the cavitation of the valve lies in the design of split flow and staged pressure in the valve.

 

"Diverting of the flow in the valve" is a way which divides a flow into several flows. The path of flow in the valve is designed to pass through several openings which are small and parallel to each other. The sizes of the bubbles getting through the paths are calculated according to the size of the opening which the flow passes. Smaller openings allow smaller bubbles to get through, resulting in less noise and less damage.

 

"Staging pressure" means that the valve is designed to have two or more settings in series. Therefore, instead of the pressure drop in a single step, it takes several smaller steps to make it. Pressure drop finished by several steps can prevent the pressure in the constriction to eliminate the cavitation of the valve.

 

In addition, we can determine the fluid temperature in the position of the control valve to reduce the vapor pressure, which can help to eliminate the cavitation of the valve.