2024.09.16

Regulating Functions of Butterfly Valves

Regulating Functions of Butterfly Valves

All control valve manufacturers will tell you that it is important to carefully calculate and select the type of valve for your control application. This

is to ensure that the process can be accurately controlled, reducing variability and all the inherent instability problems that come with it, and reducing the impact on raw material and utility costs.

However, the reason for selecting a valve is not usually controllability. There are two main considerations when selecting a valve for a given control application.

One is the total range the valve is expected to control and the second is the installed gain of the control valve over its operating range. Gain is the ratio of the rate of change of the input to the rate of change of the output.

Thus, if a 10% increase in the input signal results in a 10% change in flow, the gain is considered to be 1. The installed gain depends on the process conditions and the inherent characteristics of the valve.

When the percentage of valve travel is plotted as a percentage of maximum flow and the pressure drop is constant, the inherent characteristics are described by the shape of the graph. There are three main characteristics, fast opening, linear and equal percentage.