Application Notes

KV coefficient Valve sizing

Calculation of the valve flow coefficient KVThe procedure specified in the IEC 60534 standard is applied todetermine the valve flow coefficient KV. The relevant device-spe-cific data can be found in the associated data sheets.The equations below are given to allow a preliminary, simpli-fied calculation of the valve flow coefficient to be performed.Please note that these equations do not take account of the influ-ence of the connection fittings and the flow limitation in case ofcritical flow velocities.

Selection of the valve flow coefficient KVSOn the basis of the calculated valve flow coefficient KV, the ap-propriate valve flow coefficient KVS for the relevant valve typecan be selected from the associated data sheet.If realistic operating values have been used for the calculation,the following applies in general: For self-operated regulators: KVmax = 0.75 KVS For motor-operated valves: KVmax = 0.9 KVS

Edition March 2012

Application Notes AB 05 EN

p1 Upstream pressurep2 Downstream pressureH Travel

V.

Volume flow rate in m/h (gases)W Mass flow rate in kg/h (liquids, steam) Density in kg/m

(general, also in liquids)1 Density upstream of the valve in kg/m

(in gases and vapors)1 Temperature in C upstream of the valve

Medium Liquids Gases Steam

Pressure drop m/h kg/h m/h kg/h kg/h

p2 >p2

1

KV = V.

1000 pKV =

W

1000 p

KV =V.

G

519

G Tp p2

1 KV =W

519Tp p1

G 2 KV =

W3162.

vp2

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