Valve Sizing Calculator (Cv)

About Valve Sizing and Cv

The valve flow coefficient (Cv) quantifies the capacity of a valve to pass fluid. For liquid service a commonly used relationship is:

Cv = Q / sqrt(ΔP / SG)

Where Q is flow rate (m³/hr), ΔP is pressure drop across the valve (bar) and SG is the fluid's specific gravity relative to water. The Cv helps select a valve that can handle the required flow at the given pressure drop.

FAQs

Q: What units should I use?
A: Use Q in m³/hr, ΔP in bar, and SG dimensionless. Cv will be dimensionless in this form.

Q: Is Cv the same for gases?
A: For gases, compressibility matters and different formulas (or Kv) are used. This tool targets liquid service.

Q: How to interpret Cv?
A: Higher Cv means higher capacity; manufacturers provide Cv for valve sizes to aid selection.