Valve Sizing for Liquid

Written by Jerry Ratzlaff on . Posted in Valve

flow rate Formula

\(\large{ Q = C_v \;\sqrt {\frac {\Delta p} {SG} } }\)   

Where:

\(\large{ Q}\) = flow rate capacity, gpm

\(\large{ C_v}\) = flow coefficient

\(\large{ \Delta p}\) = pressure differential, psi

\(\large{ SG}\) = specific gravity of fluid (water at 60°F = 1.0000)

 

flow coefficient Formula

\(\large{ C_v = Q\; \sqrt {\frac{SG} {\Delta p} } }\)   

Where:

\(\large{ C_v}\) = flow coefficient

\(\large{ Q}\) = flow rate capacity, gpm

\(\large{ SG}\) = specific gravity of fluid (water at 60°F = 1.0000)

\(\large{ \Delta p}\) = pressure differential, psi

 

actual required cv Formula

\(\large{ C_{vr} = K_v \;C_{v} }\)   

Where:

\(\large{ C_{vr}}\) = corrected sizing coefficient required for viscous applications

\(\large{ K_v}\) = viscosity correction factor

\(\large{ C_v}\) = flow coefficient

 

maximum flow rate assuming no viscosity correction Formula

\(\large{ Q_{m} =   C_{vr} \;  \sqrt{ \frac {\Delta p}{SG } } }\)   

Where:

\(\large{ Q_{m}}\) = maximum flow rate, assuming no viscosity correction required, gpm

\(\large{ C_{vr}}\) = corrected sizing coefficient required for viscous applications

\(\large{ \Delta p}\) = pressure differential, psi

\(\large{ SG}\) = specific gravity of fluid (water at 60°F = 1.0000)

 

predict actual flow rate Formula

\(\large{ Q_{p} =   \frac {Q_m}{K_v }   }\)   

Where:

\(\large{ Q_{p}}\) = predicted flow rate after incorporating viscosity correction, gpm

\(\large{ Q_{m}}\) = maximum flow rate, assuming no viscosity correction required, gpm

\(\large{ K_{v}}\) = viscosity correction factor

 

corrected size coefficient Formula

\(\large{ C_{vc} = \frac {C_{vr}} {K_v} }\)   

Where:

\(\large{ C_{vc}}\) = Cv flow coefficient including correction for viscosity

\(\large{ C_{vr}}\) = corrected sizing coefficient required for viscous applications

\(\large{ K_v}\) = viscosity correction factor

 

predicted pressure drop Formula

\(\large{ \Delta p_p = SG   \;  \left( \frac {Q} {C_{vc} } \right)^2 }\)   

Where:

\(\large{ \Delta p_p }\) = predict pressure differential drop for viscous liquids

\(\large{ SG}\) = specific gravity of fluid (water at 60°F = 1.0000

\(\large{ Q}\) = flow rate capacity, gpm

\(\large{ C_{vc}}\) = Cv flow coefficient including correction for viscosity

 

maximum allowable pressure drop Formula

\(\large{ \Delta p_a = K_m \;\left( p_i \;-\; r_c \;p_v   \right)   }\)   

Where:

\(\large{ \Delta p_a }\) = maximum allowable pressure differential for sizing purposes, psi

\(\large{ K_m}\) = valve recovery coefficient from manufacturer’s literature

\(\large{ p_i}\) = body inlet pressure, psia

\(\large{ r_c}\) = critical pressure ratio

\(\large{ p_v}\) = vapor pressure of liquid at body inlet temperature, psia

 

pressure drop at which cavitation damage will begin Formula

\(\large{ \Delta p_c = Ca\; \left( p_i \;-\; p_v   \right)   }\)   

Where:

\(\large{ \Delta p_c }\) = pressure differential drop at which cavitation damage will begin, psi

\(\large{ Ca }\) = dimensionless Cavitation Number index used in determining \(\;\Delta p_c \)

\(\large{ p_i}\) = body inlet pressure, psia

\(\large{ p_v}\) = vapor pressure of liquid at body inlet temperature, psia

 

Tags: Equations for Valves Equations for Liquid Equations for Valve Sizing