Control valve Cv for liquids
Required Cv and Kv for a liquid control valve, with the choked-flow check — water properties built in.
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Liquid, gas and steam control valve sizing with choked-flow and cavitation checks — print-ready reports, any units and visible formulas. Pipe sizing and orifice plate tools are already in the shop.
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How this calculator works
For liquids, Kv = Q·√(SG/ΔP) with Q in m³/h and ΔP in bar, and Cv = 1.156·Kv (US gpm at 1 psi). The calculator first checks for choked flow: when the pressure drop reaches ΔPmax = FL²·(P1 − FF·Pv), with FF = 0.96 − 0.28·√(Pv/Pc), more pressure drop gives no more flow, and the valve is sized on the choked drop instead.
The example is 100 m³/h of water at 25 °C, 10 bar a inlet and 1 bar drop through a globe valve (FL 0.9): Kv 99.8, Cv 115.4 — choose a valve with a rated Cv of about 145 or more.
Limits: liquids only, turbulent flow, valve the same size as the line (no reducers, FP = 1). References: IEC 60534-2-1 / ISA-75.01.01 (method aligned with the published equations); Perry's §8; Ludwig Vol. 1.