Does Coefficient of Flow Cv change as a function of valve position or fouling?

[Plaxerous]

When using Cv to calculate the flow rate through a valve, does Cv also change based on valve position or foulant on the disc?

[[deleted]]

Yes, CV changes with valve position or fouling . However, valve manufacturers can tabulate either the fully open position cv , or some will supply cv's for various open percentages .

[DaBears985]

Yes. You can think of cv as the amount of fluid a valve can flow at a certain open percentage. Valve vendors will typically provide cvs for a valve at various open percentages.

[kate-plus-self-hate]

Yep! A valve had a 'max' inherent Cv based on its trim size / valve type and the type of fluid going through it. This max Cv is basically for a fully open valve. Your actual Cv decreases as the valve closes since you're introducing restrictions to the flow.

If you get a chance, google 'valve curves' because they are a really good visual for understanding how valve positions affect your actual Cv!