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Valve Cv — Gas & Steam

Compressible flow is not like liquid: once the pressure drop reaches half the absolute inlet pressure the flow chokes and extra Δp buys nothing. This caps Δp automatically and flags it.

Fluid

Solve for

Inlet pressure P1 (psia)

Pressure drop Δp (psi)

Specific gravity (air = 1)

Temperature (°F)

Flow — gas scfh / steam lb/h

Known Cv

Flow state

—

Effective Δp

—

Result

—

Kv equivalent

—

Engineering-practice formulas in imperial units (psia, °R, scfh, lb/h). For a rated design, and for superheated steam or high-noise service, use the full IEC 60534 / ISA-75 method with Fk, xT and piping factors.

A helper, not a substitute for engineering judgment. Verify against the governing standard.