Flow coefficient. Liquid flow scales as Q = Cv times the square root of pressure drop divided by specific gravity, so a valve with Cv 100 passes about 100 gpm of water at 1 psi drop and 200 gpm at 4 psi. Rated Cv is the full-open value, while control valves are sized so the required Cv falls around 20 to 80 percent travel. The metric equivalent is Kv, cubic meters per hour at 1 bar, and Cv is about 1.16 times Kv.
Required Cv at max flow is 38, the 2 inch valve has 46 full open, so it's tight but it'll work.
Size the valve to the Cv, not the line. A control valve one or two sizes below line size is normal.
Also heard as
- flow coefficient
- valve coefficient
Related terms
Rangeability
The ratio of the largest to the smallest flow a control valve can regulate while keeping its characteristic.
Flow characteristic
The relationship between how far a valve is open and how much flow it passes.
Control valve
A power-operated valve that modulates flow on a controller signal to hold pressure, level, flow or temperature at setpoint.
Throttle
To hold a valve partly open on purpose to restrict and regulate flow or pressure.