By entering the damper diameter and reading one value of dP at a select fluid velocity from the performance curve, the C_{v} can be determined. For example, the 36" damper has a pressure drop of 0.018 in wc at a velocity of 2000 ft/min air velocity. An expansion factor (Y) value of 1.0 is estimated in order to determine the C_{v} without considering the effect of gas expansion. The piping geometry factor (F_{p}) is assumed to be 1.0 to evaluate the performance of the damper without attached reducers or other fittings.

At 100% open, the damper has a calculated C_{v} of 143,649 (which corresponds to a resistance coefficient of about 0.07). Because this is an estimated value based on values taken from a curve, different points on the curve can be used to determine the C_{v} and an average can be determined.

Once the C_{v} is determined, the Control Valve Data Estimator in PIPE-FLO can be used to estimate a C_{v} profile for the damper. A sample Control Valve Data Estimator dialog box is shown below.

In this example, a Butterfly, Center Shaft body style was used with a trim type of Aligned 60° and equal percentage characteristic curve. Once the Valve Position of 100% and C_{v} value are entered, PIPE-FLO can estimate the remaining Control Valve data to fit the selected characteristic curve.

It will also enter an FL and xT profile based on typical butterfly valves shown in the IEC and ISA standards for sizing control valves.