Steam Flow Through a Valve Calculator
Calculate the steam mass flow (lb/hr and kg/hr) through a valve from its Cv and the pressure drop, with an optional superheat correction.
Method
Superheated steam is less dense, so for a given Cv it carries slightly less mass: W is divided by (1 + 0.00065 × °F superheat).
Notes
Use absolute pressure (psia). The 2.1 constant is the ISA saturated-steam value. For choked steam (P2 below ~58% of P1) the relationship changes; treat results near that point as approximate.
Frequently Asked Questions
How do I calculate steam flow through a valve?
Use W = 2.1 × Cv × √(ΔP × (P1+P2)) with pressures in psia; the result is in lb/hr.
How does superheat affect steam flow?
Superheated steam is less dense, so for the same Cv it passes slightly less mass; apply the superheat correction factor.
What pressure units do I use?
Absolute pressure (psia), not gauge. Add atmospheric (~14.7 psi) to gauge readings.
Does this handle choked steam?
Near choked conditions (large pressure drop) treat the result as approximate; choked steam flow becomes limited by inlet pressure.
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