Control valve calculator

calculation of flow coefficient - Cv or Kv

online since 2007

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Read all about available deployments. In any way of utilizing calculator, Internet connection is not required, but nice to have for authentication at least.

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common and custom fluid properties
K factor for fittings, resistance coefficient
pipe surface roughness selection
pipe material selection
select between gauge and absolute pressure
compressible isothermal flow
dry air isothermal flow
gas offtake flow
natural gas flow

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When is this calculator suitable?

To select a size of a control valve, you should calculate the required flow coefficient Cv/Kv for the flow rate and pressure drop.

For a specific control valve, flow coefficient Cv/Kv is determined experimentally by control valve manufacturers, and you can found it in manufacturers technical specifications.

They express coefficient Cv/Kv as the flow rate of water in g.p.m. [m3/h] for a pressure drop of 1 psi [1 bar] across a flow passage [flow coefficient: Cv-imperial, Kv-metric]. You can use the calculator to calculate maximum flow rate through control valve for given pressure drop and known flow coefficient of control valve Cv. With maximum flow rate calculated, you can compare control valves from different manufacturers for their efficiency for the same nominal size.

Control valve calculator is suitable for turbulent flow of liquids.

When is this calculator not relevant?

Flashing, cavitation, and chocked flow may reduce the control valve capacity. That calculation is not in this version of control valve calculator.

How is the calculation executed?

The calculator is calculating flow coefficient Cv/Kv using the relationship between pressure drop and flow rate in the control valve which is for complete turbulent flow following power law where flow coefficient Cv/Kv is the proportional constant:

where is:

q - flow rate
Cv - flow coefficient
Δp - pressure drop
S - specific gravity (relative density)

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