What is CV?
A constant (CV) related to the geometry of a valve, for a given travel, that can be used to establish flow capacity. It is the number of U.S. gallons per minute of 60◦F water that will flow through a valve with a one pound per square inch pressure drop.
The formula used to select the control valve CV with the specified differential pressure is:
W = Mass rate of flow
FP = Piping geometry factor, dimensionless
P1 = Upstream absolute static pressure
P2 = Downstream absolute static pressure
ϒ = Specific weight at inlet conditions
N6 = Numerical constant
What is CV test?
CV test is based on ANSI/ISA-S75.02, Control Valve Capacity Test Procedures that utilizes the mathematical equations outlined in ANSI/ISA S75.01, Flow Equations for Sizing Control Valves, in providing a test procedure for obtaining the following:
a) Control valve flow coefficient, CV
b) Liquid pressure recovery factors, FL and FLP
c) Reynolds Number factor, FR
d) Liquid critical pressure ratio factor, FF
e) Piping geometry factor, FP
f) Pressure drop ratio factor, XT and XTP
A basic flow test system as shown in Figure includes
a) Test specimen
b) Test section
c) Throttling valves
d) Flow-measuring device
e) Pressure taps
f) Temperature sensor