What is Cv in control valves?

Cv (Valve Flow Coefficient) is the flow rate in US gallons per minute of water at 60°F with a pressure drop of 1 psi across the valve. It's the universal sizing parameter for control valves.

Which valve has the highest Cv?

Full-port ball valves have the highest Cv (often >300), followed by butterfly (>100), globe (5–150), and V-notch ball valves. Globe valves offer best control but lowest Cv.

Should I size valve at 70% or 80% opening?

Best practice: Size control valves so normal flow occurs at 60–80% opening. This provides rangeability, avoids cavitation/choked flow, and leaves headroom for future increases.

Free Control Valve Cv Sizing Calculator

Q: When does cavitation occur in control valves?

Cavitation occurs when downstream pressure (P2) drops below the liquid's vapor pressure, forming vapor bubbles that collapse violently when pressure recovers. Use anti-cavitation trim when σ < FL².

Control Valve Sizing Analysis

Calculate Cv for liquid, gas, and two-phase flow with cavitation analysis

Liquid Type

Flow Rate

Inlet Pressure (P1)

Outlet Pressure (P2)

Density

Viscosity

Vapor Pressure

Valve Style

Control Valve Sizing Results

Required Cv

Pressure Drop (ΔP)

psi

Flow Velocity

ft/s

Reynolds Number

Viscosity Correction Factor

Recommended Valve Types

Globe Valve

Cv: 5-15

Butterfly Valve

Cv: 50-100

Ball Valve

Cv: 100-300

Plug Valve

Cv: 20-80

Control Valve Sizing Fundamentals

Valve Flow Coefficient (Cv)

The valve flow coefficient (Cv) is defined as the flow of water at 60°F in US gallons per minute at a pressure drop of 1 psi across the valve.

IEC 60534 Standard

This calculator follows IEC 60534 standards for control valve sizing, providing internationally recognized methods for liquid, gas, and two-phase flow.

Cavitation Analysis

Cavitation occurs when local pressure drops below vapor pressure, forming vapor bubbles that collapse when pressure recovers, causing damage.

Liquid Flow Equation

Cv = Q × √(SG/ΔP) where Q is flow rate (gpm), SG is specific gravity, and ΔP is pressure drop (psi).

Gas Flow Equation

Cv = Q / (1360 × P1 × Y) × √(SG × T1 × Z) where Y is expansion factor, T1 is temperature, and Z is compressibility.

Cavitation Index

σ = (P1 - Pv) / (P1 - P2) where P1 is inlet pressure, Pv is vapor pressure, and P2 is outlet pressure. Cavitation occurs when σ < FL².

Control Valve Sizing Calculator