Kvcoefficient Valve Sizing

 Application Notes K  V  coefficient · Valve sizing

Calculation of the valve flow coefficient K  V  The pro proced cedure ure spe specif cified ied in the IEC 605 60534 34 sta standa ndard rd is app applie liedd to determ det ermine ine the val valve ve flo flow w coe coeffi fficie cient nt K  V . The rel releva evant nt dev device ice-sp -speecific data can be found in the associated data sheets. Thee eq Th equa uatition onss be belo low w ar aree gi give venn to al allo low w a pr prel elim imin inar ary, y, si simp mplili-fied calculation of the valve flow coefficient to be performed. Plea Pl ease se no note te th that at th thes esee eq equa uatition onss do no nott ta take ke ac acco coun untt of th thee in inflfluuence en ce of th thee co conn nnec ectition on fi fittttin ings gs an andd th thee flflow ow lilimi mita tatition on in ca case se of  critical flow velocities.

Selection of the valve flow coefficient K  VS On th thee ba basis sis of th thee ca calc lcul ulat ated ed va valv lvee flflow ow co coef effifici cien entt K  V , the approp pr opria riate te va valv lvee flflow ow co coef effifici cien entt K  VS fo forr th thee re rele leva vant nt va valv lvee ty type pe can be selected from the associated data sheet. If re real alist istic ic op oper erat atin ingg va valu lues es ha have ve be been en us used ed fo forr th thee ca calc lcul ulat ation ion,, the following applies in general: – For  self-operated self-operated regulators: K  Vmax = 0.75 · K  VS motor-operated valves: K  Vmax = 0.9 · K  VS – For  motor-operated

p1 Upstream pressure p2 Downstream pressure H Travel .  V   Volume flow rate in m³/h (gases)  W Mass flow rate in kg/h kg/h (liquids, steam)  Density in kg/m³ (general, also in liquids) 1 Density upstream of the valve in kg/m³ (in gases and vapors)  1 Temperature in °C upstream of the valve

Medium Pressure drop p1 p2 > 2 p1 p < 2 p1 p2 < 2 p1 p > 2

 where: p1 [b [bar ar]] p2 [b [bar ar]] [bar ar]] p [b T1 [K] .

Liquids

m³/h

Gases

k g/ h

m³/h .

 V  K  V  = G 519 .

K  V  = V 

 1000   p

kg/ h G  T1 p

p2

kg/h

K  V  =

 W  T1 519 G p p2

K  V  =

 W   v 2 3162 . p

K  V  =

 W  T1 259.5 25 9.5 p1 G

K  V  =

 W  2v * 3162 . p1

 W  K  V  = 1000  p

Absolu Abso lute te pr pres essu sure re pabs Abso Ab solu lute te pr pres essu sure re pabs Abso Ab solu lute te pr pres essu sure re pabs (differential pressure p 1 – p2) 273 +  1

 V G [m³/h [m³/h]] Flow rate rate of gases, gases, related to 0 °C and 1013 mbar 

Steam

.

K  V  =

 G

 v 1  v 2  v*

 V G G T1 259.5 p1

[kg/m³]] [kg/m³ [kg/m³] [kg/m ³] [m³/kg] [m³/ kg] [m³/kg] [m³/ kg] [m³/kg]

Densityy of liqu Densit liquids ids Density Densi ty of gases at 0 °C and 1013 1013 mbar  mbar  Specific Spec ific volume volume (v´ found found in the steam steam table) table) for p 1 and  1 Specific Spec ific volume volume (v´ found found in the steam steam table) table) for p 2 and  1 p1 Specific volume (v´ found found in the steam table) table) for  2 and  1

Edit Ed itio ionn Ma Marc rchh 20 2012 12

 Application Notes

AB 05 EN

Specifications subject to change without notice

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 AB 05 EN

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