# Control valve sizing and flow coefficient Cv calculation

Control valve sizing is based on flow coefficient Cv calculation. Flow coefficient Cv calculation is made for required flow rate and related pressure drop in control valve. With flow coefficient Cv calculated, size of control valve can be selected, or two control valves from different manufacturers can be compared in terms of flow capacity for certain pressure drop and the same control valve size.

Flow coefficient Cv calculation is based on the relation between pressure drop and flow rate in control valve which is for complete turbulent flow following power law where flow coefficient Cv is the proportional constant. Flow coefficient Cv is determined experimentally by control valve manufacturers.

Flow coefficient of control valve Cv is expressed as the flow rate of water in gpm u.s. (m^{3}/h) for a pressure drop
of 1 psi (1 bar) across a flow passage (flow coefficient: Cv-imperial, Kv-metric).

Control valves sizing calculator you can use to calculate maximum flow rate through control valve for given pressure drop and known flow coefficient of control valve Cv.

Control valve calculator can be used for turbulent flow of water or other incompressible fluid. For compressible flow of gases and steam gas flow coefficient Cg should be calculated.

Flashing and cavitation and chocked flow may reduce the control valve capacity and it is not in this version of control valve calculator.

For compressible flow - for gases, you should use gas control valve calculator, as this control valve calculator is for incompressible flow.

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