🎛️ Control Valve Sizing (Cv/Kv)
Calculate control valve coefficients (Cv, Kv) for liquid, gas, and steam flow. Analyzes choked limits, flashing, cavitation risk, and recommends optimal globe valve sizes.
⚡ Fortran 90 Engine
Double Precision (IEEE 754)
✓ ISO / ASME Validated
Tools
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📅 Released
Jun 2026
⏱️ Latency
< 1 ms
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Hardware & Sizing Partner: Need to size a control valve or check ASME flange bolt torque for this line?
📋 Sizing Parameters
Units:
SI Metric (m³, bar, °C)
📊 Sizing Results
Flow Coef (Cv)
—
Imperial units (gpm/psi0.5)
Flow Coef (Kv)
—
Metric units (m³/h/bar0.5)
Normal Flow Regime
The pressure drop across the valve is below the critical threshold. Flow is fully subcritical and stable.
📋 Globe Valve Capacity & Recommended Size
| Nominal Size (NPS) | Max Flow Coef (Cv) | Operating Load (%) |
|---|
📘 Calculation Methodology: Control Valve Sizing & Flow Coefficient (Cv / Kv)
Mathematical Model & Theory
Sizes industrial control valves for liquid and gas service per IEC 60534 / ISA-75.01 standards, relating volumetric flow rate $Q$ and differential pressure $\Delta P$ to flow coefficient $C_v$:
$$C_v = Q \sqrt{\frac{SG}{\Delta P}} \quad (\text{US GPM, psi}), \quad K_v = Q_{m^3/h} \sqrt{\frac{SG}{\Delta P_{bar}}} = 0.865 \cdot C_v$$
$$\text{Choked Cavitation Limit: } \Delta P_{max} = F_L^2 (P_1 - F_F P_v)$$
Assumptions
- Newtonian liquid flow without flashing (sub-critical pressure drop $\Delta P < \Delta P_{max}$).
- Liquid specific gravity $SG = ho / ho_{water}$ at reference temperature.
Academic References
- IEC 60534-2-1: Industrial-process control valves — Flow capacity sizing equations.
- ISA-75.01.01: Flow Equations for Sizing Control Valves, ISA.
Worked Engineering Example
Problem Statement:
Water ($SG = 1.0$) flows through a control valve at $Q = 150\text{ m}^3/\text{h}$ with allowable pressure drop $\Delta P = 1.5\text{ bar}$. Calculate the required valve capacity $K_v$ and $C_v$.
Step-by-step Solution:
1. Calculate $K_v$:
$$K_v = Q \sqrt{\frac{SG}{\Delta P}} = 150 \times \sqrt{\frac{1.0}{1.5}} = 150 \times 0.8165 \approx 122.47\text{ m}^3/\text{h}$$
2. Convert to Imperial $C_v$:
$$C_v = \frac{K_v}{0.865} = \frac{122.47}{0.865} \approx 141.58\text{ US GPM}$$
Final Result:
Required valve capacity is $K_v = \mathbf{122.5}$ ($C_v = \mathbf{141.6}$).
Water ($SG = 1.0$) flows through a control valve at $Q = 150\text{ m}^3/\text{h}$ with allowable pressure drop $\Delta P = 1.5\text{ bar}$. Calculate the required valve capacity $K_v$ and $C_v$.
Step-by-step Solution:
1. Calculate $K_v$:
$$K_v = Q \sqrt{\frac{SG}{\Delta P}} = 150 \times \sqrt{\frac{1.0}{1.5}} = 150 \times 0.8165 \approx 122.47\text{ m}^3/\text{h}$$
2. Convert to Imperial $C_v$:
$$C_v = \frac{K_v}{0.865} = \frac{122.47}{0.865} \approx 141.58\text{ US GPM}$$
Final Result:
Required valve capacity is $K_v = \mathbf{122.5}$ ($C_v = \mathbf{141.6}$).