Cavitation occurs when the pressure inside the valve drops below the vapor pressure of the liquid, causing the liquid to boil. When the pressure recovers above the vapor pressure, the gas bubbles implode. This creates shock waves and microjets.
Erosion damage is closely linked to the flow velocity. When a valve is used at a very high flow velocity, it creates a high noise. If the noise level is higher than 110 dBA, the valve will be mechanically damaged.
How to avoid cavitation?
To prevent cavitation, either the flow parameters must be adapted or the pipe size must be increased. In general, we recommend to keep the noise level below 90 dBA as government regulations limit noise level to 85 dBA.
Following table shows our recommendation for flow velocity based on media type.
Media
Valve type
Flow velocity
Liquid
Loose liner
3 m/s up to DN 400 2 m/s up to DN 800 1 m/s for larger valves
Vulcanised liner
5 - 6 m/s
Double offset
7 m/s
Gas
All types
10 m/s
Steam
All types
50 – 80 m/s
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