What measures can be taken to reduce the effect / damage due to cavitation in a cavitating control valve?

When cavitation is predicted, some available remedies include: 

1. Increase the downstream pressure by throttling a downstream valve or installing an orifice.

2. Decrease the differential pressure by using two valves in series.

3. Use a small bypass line for low flow rates.

4. Install vacuum breaker ports immediately downstream of the valve to reduce the vacuum pocket. 

• Make sure you select the right valve for your application. If your valves are the wrong size or the wrong style, their likelihood of cavitation increases. In water and liquid systems with high pressure drop, use an anti-cavitation valve.
• Use multiple control valves or multistage control valves so that the pressure drop happens gradually rather than all at once. This is called pressure drop staging.
• Place the control valve at a lower elevation in the system or in an area where the fluid temperature is reduced.

We can eliminate the cavitation using the the trim design

Using the various stage pressure reduction we can eliminate the cavitation. Which means the trim will not allow to go below the vapor pressure.