What is Cv of a valve?

Cv is the capacity of a valve and is defined as :

“No of gallons per minute of water which passes through a fully open valve at a pressure drop of 1 psi.”

CV = q ( ▲P / G )


Cv = Valve co-efficient

q = Volumetric flow rate ( gallons minute )

▲P = Pressure drop across the valve in psi.

G = Specific gravity of flowing fluid.

The valve coefficient Cv is proportional to the area ‘A’ between the plug and valve seat measured perpendicularly to the direction of flow.