cv calculation for liquid,gas for contro lvalve

To the best of my knowledge, C_v is always determined experimentally.

i s a 7 5 s e r i e s

cv cal for liquids...

cv = Q * Sqr root( G/p1-p2 )

if P is specified in gpm

cv = 1.17* Q* Sqr root( G/p1-p2 )

if P is specified in Kg/cm2

G = Speific gravity of the source

Q = Flow rate

Cv can be calculated roughly by the formula :

Cv = Q * sqr root( rho/(1000*Pressure drop))

where,

rho = density of the fluid

Q = Flowrate

A more accurate approximation can be achieved by using the sizing softwares provided by valve manufacturers.

Regards