Control Valve Cv Calculator

💧 Liquid Cv Sizing

INPUT DATA

Flow Rate

Mass Flow Rate W kg/h

kg/h

Liquid Density ρ kg/m³

kg/m³

Water = 1000 kg/m³ @ 15°C | Specific gravity Gf = ρ/1000

Pressures

Upstream Pressure P₁ bara

bara

Downstream Pressure P₂ bara

bara

Vapour Pressure @ flowing temp Pᵥ bara

bara

Water @ 20°C = 0.023 bara | Use 0.001 if unknown

Critical Pressure P꜀ bara

bara

Water = 220.9 bara | Hydrocarbons typically 40–50 bara

Valve Parameters

Liquid Pressure Recovery Factor Fₗ —

—

Globe valve ≈ 0.85 | Ball valve ≈ 0.60 | Use 0.80 if unknown

Piping Geometry Factor Fₚ —

—

Fₚ = 1.0 when no reducers are installed

📐 Formula Reference — IEC 60534-2-1

Cᵥ = Q / (0.865 × Fₚ × √(ΔP_eff / Gf))
ΔP_crit = Fₗ² × (P₁ − FF × Pᵥ)
FF = 0.96 − 0.28 × √(Pᵥ/P꜀)
ΔP_eff = min(ΔP, ΔP_crit)

where Q = W/ρ [m³/h] | Gf = ρ/1000 | ΔP = P₁ − P₂ [bar]

INTERMEDIATE RESULTS

Enter input data and click Calculate Cᵥ to see results.

Sizing note: Select the next larger standard valve size with Cᵥ rated ≥ calculated Cᵥ. Typical design target: valve operates at 60–80% of rated Cᵥ at normal flow.

Kᵥ (metric): Kᵥ = 0.865 × Cᵥ [m³/h per √bar]

💨 Gas / Vapour Cv Sizing

INPUT DATA

Flow Rate Input Mode

Flow input

Mass Flow Rate W kg/h

kg/h

Gas Properties

Molar Mass (Molecular Weight) MW g/mol

g/mol

Air = 28.964 | Methane = 16.04 | CO₂ = 44.01 | H₂ = 2.016 | G = MW/28.964

Flowing Temperature T °C

°C

Compressibility Factor z —

—

Ideal gas z = 1.0 | For most process gases use 0.90–0.98

Inlet Density ρ₁ kg/m³ (auto-calculated — informational)

kg/m³

ρ₁ = P₁×10⁵×MW / (8314×Tₖ×z) — not directly used in Masoneilan Cᵥ formula

Pressures

Upstream Pressure P₁ bara

bara

Downstream Pressure P₂ bara

bara

Valve Parameters

Critical Flow Factor Fₗ —

—

Globe = 0.91–0.99 | Ball = 0.55–0.80 | Use 0.90 if unknown

Piping Geometry Factor Fₚ —

—

📐 Formula — Masoneilan Control Valve Sizing Manual (Metric)

G = MW / 28.964 [gas sp. gravity, air = 1]
Gf = G × 288 / T [sp. gravity @ flowing temp, T in K]
ρ₁ = P₁×10⁵×MW / (8314×T×z) [kg/m³ — informational]
y = 1.63 / Fₗ × √(ΔP/P₁) [max y = 1.50]
y−0.148y³ → 1.0 when y = 1.50 [choked = critical flow]

Mass flow:
Cᵥ = 54.5 × (W/1000) × √z / (Fₗ × P₁ × √Gf × (y−0.148y³))

Volumetric flow (@ 15°C, 1013 mbar):
Cᵥ = Q × √(G×T×z) / (257 × Fₗ × P₁ × (y−0.148y³))

W [kg/h] | Q [m³/h @ 15°C] | P₁, ΔP [bar absolute] | T [K] | z [—]

INTERMEDIATE RESULTS

Enter input data and click Calculate Cᵥ to see results.

Critical (choked) flow occurs when y reaches 1.50. At this point (y − 0.148y³) = 1.0. Increasing ΔP further does not increase flow through the valve.

y coefficient: y = 1.63/Fₗ × √(ΔP/P₁) for all standard valves (y = 1.40/Fₗ × √(ΔP/P₁) only for LO-DB® cartridges and two-stage 41000/72000 series).

Kᵥ (metric): Kᵥ = 0.865 × Cᵥ [m³/h per √bar]

♨️ Steam Cv Sizing

INPUT DATA

Steam Condition

Steam type

Mass Flow Rate W kg/h

kg/h

Pressures

Upstream Pressure P₁ bara

bara

Downstream Pressure P₂ bara

bara

Steam Temperature

Flowing Temperature T °C

°C

Must be ≥ Tₛₐₜ at P₁ for superheated steam

Valve Parameters

Critical Flow Factor Fₗ —

—

Globe valve ≈ 0.91–0.99 | Use 0.90 if unknown

📐 Formula — Masoneilan Control Valve Sizing Manual (Steam)

y = 1.63 / Fₗ × √(ΔP/P₁) [max y = 1.50]
T_sh = T − T_sat [steam superheat, °C]

Saturated steam (T_sh = 0):
Cᵥ = 83.7 × (W/1000) / (Fₗ × P₁ × (y−0.148y³))

Superheated steam (T_sh > 0):
Cᵥ = 83.7 × (1 + 0.00126×T_sh) × (W/1000) / (Fₗ × P₁ × (y−0.148y³))

W [kg/h] | P₁, ΔP [bar absolute] | T_sat from built-in steam table (IAPWS)

INTERMEDIATE RESULTS

Enter input data and click Calculate Cᵥ to see results.

No density needed: The Masoneilan steam formula uses only the superheat correction factor (1 + 0.00126·T_sh). Steam density cancels out of the derivation.

Superheat T_sh: Auto-calculated as T_flowing − T_sat(P₁). For saturated steam, T_sh = 0 and the correction factor = 1.

Kᵥ (metric): Kᵥ = 0.865 × Cᵥ [m³/h per √bar]

INPUT DATA

Mass Flow Rates

Gas Mass Flow Rate Wg kg/h

kg/h

Liquid Mass Flow Rate Wf kg/h

kg/h

Phase Densities @ Inlet Conditions

Gas Density ρg kg/m³

kg/m³

At P₁ and flowing temperature. Use process simulator or ideal gas law.

Liquid Density ρf kg/m³

kg/m³

Pressures

Upstream Pressure P₁ bara

bara

Downstream Pressure P₂ bara

bara

Vapour Pressure of Liquid Phase Pᵥ bara

bara

For saturated liquid: Pᵥ = P₁

Critical Pressure of Liquid Phase P꜀ bara

bara

Gas Phase Properties

Specific Heat Ratio (Gas) k —

—

Valve Parameters

Liquid Pressure Recovery Factor Fₗ —

—

Use 0.80 (globe) if unknown — see Masoneilan OZ1000 supplement

Pressure Drop Ratio Factor x_T —

—

Use 0.62 if unknown (typical globe valve)

Piping Geometry Factor Fₚ —

—

📐 Formula — Masoneilan OZ1000 (Two-Phase)

ff = Wf/(Wf+Wg) | fg = Wg/(Wf+Wg)
FF = 0.96−0.28√(Pᵥ/P꜀) | Fₖ = k/1.4
ΔPf = Fₗ²×(P₁−FF×Pᵥ) [liq. choke limit]
ΔPg = min(ΔP, Fₖ×x_T×P₁) [gas choke limit]
Y = 1 − x_g,eff/(3×Fₖ×x_T)
Cᵥ = Wf/(27.3×Fₚ×√(ΔPf×ρf)) + Wg/(27.3×Fₚ×Y×√(ΔPg×ρg))

Per Masoneilan Control Valve Sizing Handbook, Bulletin OZ1000 7/00

INTERMEDIATE RESULTS

Enter input data and click Calculate Cᵥ to see results.

Two-phase sizing note: Mixed phase (gas + liquid) sizing is inherently uncertain. This calculation follows the Masoneilan superposition method — each phase is sized separately, then combined. Use a safety factor of 1.2–1.3 on the calculated Cᵥ. Confirm final sizing with the valve manufacturer.

Typical applications: Flash valves, separator inlet valves, two-phase pipeline letdowns.

IEC 60534-2-1 · ISA-75.01.01 · Masoneilan OZ1000 · For initial sizing only — confirm with valve manufacturer

Your 90-day free save period has ended

💾 Save your Cv calculation