Try Google.

You will find the answer very quickly.

You need to provide the data.

For valve CV you need to have two out of three of CV, flow, Dp to calculate the third

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

A calculator from a reputable Vendor will provide accurate results based on standardized procedure.
https://go.emersonautomation.com/FSMDownload

@Er.

With regards to dP - remember you are specifying a control valve! So the dP is what you want it to be! Of course the valve has a max capacity - but that is implicit at the dP you specify!

So in order to specify you need to know your dP and your flow! This is the tricky part on sizing a CV - you have a lot of combinations of flow and dP and you wish the valve to be operating at say 30-70% open!

This was also a bit hard for me to grasp initially but consider this, you have a vessel and you wish to control level. Your upstream vessel normally has a pressure between 5-7 barg and the downstream is atmpsheric (fixed 0 barg). SO this means that the dP will be 5-7 bar. Your required flowrate will depend on your inlet rate- If this was 20-40 m3/hr then you would specify max flowrate with min dP so 40 m3/hr and 5 bar. But should this be you ideal operating point? Hardly. This should be your CV for say 70% open. And the other end would be dP=7 bar and flow 20 m3/hr and this could be you CV and 30% open.

If its the pressure you wish to control its the same way around.

Best regards, Morten

--- Best regards, Morten Andersen

OP hasn't been seen for three weeks....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.