Equal percentage flow characteristics, in simple terms, 

means that a given percentage change in the valve opening will produce the same percentage change in flow. 

the table above and chart for short pattern and for long pattern type ball valves, are provided to assist in sizing MV’-Flanged ball valves for control applications.

Kv indicates the quantity of m3/h of water at 20 C (70 F) which flows through the valve at apressure drop of one bar. Cv indicates the quantity of U S Gallons per minute of water at 20° C (70° F) which flows through the valve at

a pressure drop of one p.s.i. 

Cv =Kv x 1.1688