What is cavitation in control valves and how is it controlled?

Cavitation occurs when liquid pressure drops below vapor pressure in the valve (creating vapor bubbles) then recovers downstream (collapsing bubbles violently). Effects: severe erosion of trim and body, noise, vibration, and reduced flow capacity. Identification: noise, vibration, pitting on trim. Control methods: select valves with high FL factor (low recovery), use anti-cavitation trim (multi-stage pressure reduction, tortuous path), increase downstream pressure (back-pressure device), reduce inlet pressure, or use cavitation-resistant materials. Size properly to avoid excessive pressure drop in single stage.