Enter flow and pressures — get the required Cv/Kv plus choked-flow and cavitation warnings.
Open the calculator →The valve flow coefficient Cv (or metric Kv) tells you how much a valve will flow for a given pressure drop. EnggiBasis computes the required coefficient from your process conditions, then checks whether the valve will choke, cavitate or flash — the failure modes that ruin real installations.
Cv = Q · √(SG / ΔP) (Q in gpm, ΔP in psi)
Kv = Q · √(SG / ΔP) (Q in m³/h, ΔP in bar), with Cv ≈ 1.156 · Kv.
The usable pressure drop is limited to the choked value:
ΔP_choked = FL² · (P1 − FF · Pv)
where FL is the valve's liquid pressure-recovery factor, Pv the vapour pressure and FF the liquid critical-pressure ratio factor. Above this, extra ΔP does not add flow — and cavitation damage becomes likely.
Compressible sizing uses the expansion factor Y and the terminal pressure-drop ratio xT; steam sizing adds density from steam tables. EnggiBasis handles all three services.
Aim for 60–80% open at normal flow. A valve sized to run nearly wide-open has no control margin; one barely cracked open is oversized. EnggiBasis flags both.
| Input | Value |
|---|---|
| Liquid flow | 50 m³/h |
| Pressure drop | 2 bar |
| Specific gravity | 1.0 (water) |
Result: Kv = 50 · √(1 / 2) ≈ 35.4, i.e. Cv ≈ 40.9 — before choked-flow correction. Try it with your own numbers →
Liquid: Cv = Q·√(SG/ΔP) (gpm, psi). Metric: Kv = Q·√(SG/ΔP) (m³/h, bar). Cv ≈ 1.156·Kv.
Cv is imperial (gpm water at 1 psi), Kv is metric (m³/h water at 1 bar). Cv ≈ 1.156 × Kv.
Control valve sizing is part of EnggiBasis Pro (₹99/month). You can open the app free to explore.
Cv/Kv with choked-flow & cavitation checks · Pro (₹99/month)
Open the calculator →Related: Line sizing · Pump sizing · Relief valve sizing