One, Definition and causes of cavitation phenomena



Cavitation refers to the phenomenon where bubbles (or steam bubbles) form in the liquid when the local pressure in the liquid flow decreases to below the saturated vapor pressure of the liquid. When these bubbles flow into the high-pressure area, they burst rapidly, producing local high pressure and high temperature, thereby causing severe impact and corrosion on the inner wall of the valve and other components. This is the destructive mechanism of cavitation.



The main factors causing cavitation in valves include:



1. Excessive pressure difference: When the pressure difference between the inlet and outlet of the valve is too high, especially at the throttling section, the flow velocity increases and the pressure drops rapidly, which is very easy to form bubbles.

　　2. Insufficient pressure recovery after the valve:If the pressure after the valve is not sufficient to maintain the stability of the bubbles, they will break.



3. Medium characteristics: Certain liquids (such as water, oils) are more prone to vaporization at low pressure, thereby causing cavitation.



4. Unreasonable valve structure design: Unsmooth flow channel design, overly concentrated throttling areas, and other factors will exacerbate local pressure changes,诱发空化.



Two, Hazards of cavitation phenomena



Cavitation not only shortens the service life of the valve but may also bring the following hazards:



- Cause valve vibration and noise;



- Lead to damage of the sealing surface, affecting the sealing performance of the valve;



- Cause equipment material fatigue and corrosion;

　　- Increase system maintenance costs and affectproduction continuity.

　　Three, Prevention and control measures for cavitation phenomena



To avoid the adverse consequences of cavitation, efforts can be made from the following aspects:



# (1) Rational selection of valve type and model



Under high-pressure difference conditions, valves with strong cavitation resistance should be prioritized, such as multi-stage pressure-reducing valves, cage valves, or multi-hole valves. These valves effectively reduce local pressure drop through multi-stage pressure reduction or uniform distribution of flow channels, thereby reducing the risk of cavitation.



# (2) Control the pressure difference before and after the valve



During system design, reasonable bypass, pressure relief valves, or other regulating means should be set to avoid the valve operating under extreme pressure differences. If necessary, multi-stage regulation can be adopted to distribute the total pressure difference among multiple valves.



# (3) Optimize the internal structure design of the valve



Optimize the valve flow structure through CFD (Computational Fluid Dynamics) simulation to reduce the formation of local vortices and negative pressure zones, and improve the stability of fluid flow.



# (4) Use high-erosion-resistant materials



For parts prone to cavitation, materials such as stainless steel, duplex steel, or other high-hardness, high-corrosion-resistant materials can be selected to improve the cavitation resistance of the valve.



# (5) Regular inspection and maintenance



Regular inspections of valves in key systems should be carried out to detect wear and erosion in a timely manner, and replacements or repairs should be made to prevent further deterioration of cavitation.



Four, Conclusion



Cavitation is a phenomenon that cannot be ignored during valve operation, as it not only affects the stability of the system but also brings safety hazards and economic losses. Therefore, through various means such as scientific design, selection optimization, material upgrading, and regular maintenance, it is possible to effectively prevent and control the occurrence of cavitation. Only by fully understanding the causes and consequences of cavitation can we better ensure the safe and efficient operation of valve equipment and promote the sustainable development of industrial systems.