# Pipe flow calculators

## Control valve sizing

#### Calculator Description

Control valves sizing calculator can be used to calculate maximum flow rate through control valve for given pressure drop and known flow coefficient of control valve Cv.

• Calculate:

• Maximum flow rate through control valve
• Flow velocity
• Flow coefficient
• Input:

• Valve diameter
• Pressure drop
• Liquid density

#### Calculator Features

• For turbulent flow of water or other incompressible fluid
• Metric and imperial flow coefficient calculation

Control valve sizing is based on the flow coefficient Cv calculation. Calculation of Cv is made for required flow rate and related pressure drop in control valve. With flow coefficient Cv calculated, size of control valve can be selected. Two control valves from different manufacturers can be compared in terms of flow capacity for certain pressure drop and the same control valve size comparing its Cv.

Cv calculation is based on the relation between pressure drop and flow rate in control valve which is for complete turbulent flow following power law where flow coefficient Cv is the proportional constant. Cv is determined experimentally by control valve manufacturers.

Control valve Cv is expressed as the flow rate of water in gpm u.s. (m3/h) for a pressure drop of 1 psi (1 bar) across a flow passage (flow coefficient: Cv-imperial, Kv-metric).

Control valve calculator can be used for turbulent flow of water or other incompressible fluid. For compressible flow of gases and steam gas flow coefficient Cg should be calculated.

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

If you would like to use the calculator, but actually can't see the blue CALCULATOR button in the upper left part of the page than please read instructions.

Q: Calculate flow coefficient of control valve for 500 gpm and pressure difference of 30 psi. Fluid density is 62 lb/ft3. Valve diameter is 2 in

A: Calculation setup:
Input values:
q = 500 gpm US
D = 2 in deltap = 30 psi
rho = 62 lb/ft3

Q: Calculate pressure drop in control valve with flow rate of 500 gpm and flow coeffient of Cv150. Fluid density is 62 lb/ft3. Valve diameter is 1.5 in

A: Calculation setup:
Input values:
q = 500 gpm US
D = 1.5 in Cv = 150
rho = 62 lb/ft3

Q: Calculate flow rate through control valve with flow coeffient of Cv150 and pressure drop of 4 psi. Fluid density is 62 lb/ft3. Flow velocity is 5 m/s

A: Calculation setup:
Input values:
v = 5 m/s
Cv = 150
deltap = 4 psi
rho = 62 lb/ft3

Control valve flow coefficient calculation is based on the following formula:

Read more about used theory on flow in valves and fittings page.

If you experience problems with calculator start try to find answers on instructions page.

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