ElectricValve Actuators
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How to find the necessary cV value for a valve for liquids:

Q = flow rate in gpm (US gallons)

G = specific gravity of liquid

DP = pressure drop = (inlet pressure – outlet pressure) (in psi)

 
 
Q
CV =
-------------
 
(DP /G)½

or..

   
DP = G x (Q/CV)2

Approximate specific gravities of some common liquids are:

Acetone = 0.78 Benzene = 0.88
Ethanol = 0.79 Kerosene = 0.80
Water (fresh) = 1.00 Water (salt) = 1.03

Example: 

A Series 18 Swagelok® valve has a CV of 1.8 when fully open. (at 2 turns open, it would be cV = 0.75)

For a flow of 6 gpm of benzene, the pressure drop will be approximately:
0.88 x (6/1.8)2 = 0.88 x 3.332= 9.8 psi 

You may want to simply use our maximum flow or minimum CV calculators

  Flow based on Cv     Cv based on Flow
  Flow based on Cv (metric)     Cv based on Flow( metric)

Note: this relationship is widely published and commonly used in industry. It provides reasonable estimates for liquids with viscosities similar to water.