How do you diagnose and prevent cavitation in control valves?

Cavitation occurs when local pressure drops below vapor pressure, forming and collapsing bubbles. Symptoms: noise, vibration, pitting damage downstream of trim. Diagnosis: check operating conditions against cavitation indices (Sigma, Xfz), inspect for damage during maintenance. Prevention: use anti-cavitation trim (staged pressure reduction, tortuous path), relocate valve to higher pressure location, increase back pressure, use larger valve at lower dP, or consider applying back pressure via downstream restriction. For severe cases, use specialized cavitation-resistant materials.