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"CV" valve calculation outline

"CV" valve calculation outline

"CV" valve calculation outline

(OP)
How does one undertake a "CV" calculation. And what is a CV calculation regarding flow through valves.

RE: "CV" valve calculation outline

Cv= flow of water at 60 deg F in USgal/min at a pressure difference of 1 psi

Best regards

Morten

RE: "CV" valve calculation outline

I always resist giving MortenA's example, Not that it is wrong, but it does seem to imply thatthe relationship between flow and Delta-P is linear.  it's not.  

If you get 1 gallon at 1 psi loss, you will get 1.414 gpm at 2 psi  differential.  

There are a family of Cv equations.  Liquids, Gases, Steam, SUbcritical, Choked flow, etc.  Most of the major control valve companies allow at least a trial version of their sizing software to be downloaded from their website.  ANy decent program runs all the checks to determine the flowing conditions and applies the appropriate equation.  

RE: "CV" valve calculation outline

Cv is another way of expressing the amount of pressure drop, or in otherwords, flow resistance, you can expect through a valve or fitting.  If the manufacturer cannot give you the value, you can calculate it using the data in Crane Technical Paper #410.  However, I would be very surprised if the valve manufacturer does not have the data readily available for you.

bcd

RE: "CV" valve calculation outline

Jim

The definition of Cv is clear. The fact that sizing and choosing a control valve isnt just calculating a single Cv value is something else.

Best regards

Morten

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