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Valve Sizing

Saturated Steam

Steam Temperature Inlet Pressure Flow Coefficient Volumetric Flow Pressure Drop ΔP
Celsius (°C) mm Water Column Cv kg/h PSI

Air & Gases

Fluids Inlet Pressure Flow Coefficient Volumetric Flow Pressure Drop ΔP Fluid Temperature
Ozone torr = mmHg kv m3/h mWatercolumn Celsius (°C)

Water & Liquids

Liquids Inlet Pressure Flow Coefficient Volumetric Flow Pressure Drop ΔP
Diesel Fuel bar Kv bar m3/h
Approx.Kv Approx.Φ
0,05 1,2mm
0,17 2,4mm
0,45 4,8mm
0,6 6,4mm
1,7 9,0mm
3,0 13,0mm
4,0 16,0mm
4,5 18,0mm
6,5 19,0mm
11,0 25,0mm
15,0 32,0mm
22,0 38,0mm
41,0 51.0mm

100.00 m3/h (Kv) =

1,670.00 l/mn (Kvh)

117.00 US gal/mn (Cv)

97.50 UK gal/mn (Cve)

Valve Sizing Calculation - Theory

Control valve sizing is based on the calculation of flow coefficient for given pressure drop and fluid flow rate. Main equitation that gives relation between flow rate and pressure drop is:


for imperial units, and:
for metric units,


where is:

Cv - flow coefficient in imperial units
Kv - flow coefficient in metric units
Dp - pressure drop through control valve
Q - fluid flow rate
G - specific gravity
ro - relative density

Flow coefficient is defined as the proportional constant between pressure drop and flow rate and it is determined experimentally by the valve manufacture. It 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. note: (flow coefficient: Cv-imperial, Kv-metric)


Relation between volumetric and mass flow rate is calculated using well known equation:
Also, velocity or pipe diameter can be calculated using following equations:


For all valve sizing calculations please consult one of our friendly staff at Just Valves


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