Note: 1. The above 'WET' means the test fluid is water or other non-lubricating mediums. 'DRY' means the test medium is dry compressed air.

      2. When the valve serves in a too low working temperature, operating torque will increase with the consequence of increased hardness of rubber in low temperature.

Flow Coefficient of Butterfly Valve: Cv Value
Cv Value has an expressions to calculate and definition as follow 
Note: Q---Fluid Volume that pass the valve per minute(Usgal/min)
P---Pressure Difference between import and export of the valve(psi)
G---Density of Fluid
With the above expressions, You may calculate the flow volume that pass the a valve or pressure loss between the two end of a valve.
Example1)A 6" butterfly valve is at 70¡ãopening, and a kind of fluid, which density is 0.8, pass the valve with volume 1200 Usgal/min£¬then the pressure loss between the two end is
P =GQ^2 / Cv^2=0.8*1200^2/958^2

                    
Example2)10" butterfly valve is at 90¡ãopening, and there is a pressure loss 0.6 psi between the two end of the valve when a kind of fluid, which density is 0.8, pass the valve£¬then the flow volume that pass the valve is