ChemCalc sizes control valves (throttling valves) per IEC 60534-2-1 and ISA S75.01. The calculator computes the required flow coefficient Cv (US customary) and Kv (SI metric) for liquid and gas service, and flags choked flow and cavitation conditions.
Service Types
Liquid — incompressible, Cv and Kv Gas — compressible, critical and subcritical Cavitation index check (Kc / σ) Choked flow (ΔP ≥ FLΔPmax)Key Inputs
| Parameter | Notes |
|---|---|
| Upstream pressure P1 (kPa) | Absolute, at valve inlet flange |
| Downstream pressure P2 (kPa) | Absolute, at valve outlet flange |
| Flow rate (m³/h or kg/h) | Volumetric for liquid; mass for gas |
| Specific gravity SG (liquid) | Relative to water at 15°C |
| Gas: T, MW, γ, Z | Inlet temperature and gas properties |
| xT (pressure differential ratio) | Valve-specific; globe ~0.70, ball ~0.25 |
Outputs
- Required Cv — US customary (gpm / √psi)
- Required Kv — SI metric (m³/h / √bar), Kv = Cv / 1.156
- Flow regime — turbulent, transitional, or laminar flag
- Choked flow indicator — whether ΔP exceeds FL²·(P1 − FF·Pv)
- Effective ΔP — limited to choked value when applicable
IEC 60534 Equations
| Equation | Standard | Condition |
|---|---|---|
| Liquid: Cv = Q / (N1 · FL · √(ΔP/SG)) | IEC 60534-2-1 Eq.(1) | Turbulent, non-choked |
| Gas (Y expansion): Cv = W / (N6 · Y · √(x·P1·ρ1)) | IEC 60534-2-1 Eq.(3) | Subsonic to critical |
| Choked limit: xmax = Fγ · xT | IEC 60534-2-1 §6.3 | Limits Y = 0.667 |
Numerical factors: N1 = 0.0865 (m³/h, kPa, SG), N6 = 2.73 (kg/h, kPa, kg/m³).
Also Available: Cavitation Check
ChemCalc includes a separate cavitation index display showing σ = (P1 − Pv) / ΔP. When σ approaches the valve's Kc (critical cavitation coefficient, typically 3–8 for globe valves), the calculator flags a cavitation risk. Flashing service (P2 < Pv) is also detected.