The successful operation of a controlled system depends on proper sizing of the valve. A practical method - utilizing a graphical presentation of valve sizing based on the Cv ("C" sub"v") ratings of valves - is presented for the GC Valves general purpose designs.
The Cv rating of any valve is the flow rate of water at standard conditions (60°F, specific gravity = 1) in GPM (gallons per minute), which will pass through the valve with a one psi (pound per square inch) pressure drop across the valve when in the fully open position.
A valve so restricted or ported which passes 1 GPM of liquid with a specific gravity of 1 and an accompanying pressure drop of 1 psi is assigned a rating of Cv = 1. By comparison, a valve having a Cv = 2 would have twice the flow capacity with the same pressure drop.
