Control valve Q&A

Q: I have seen an article “Installed Gain as a Control Valve Sizing Criterion.” It would appear that an analysis of control valve installed flow characteristics and installed gain would be very useful as part of the process of selecting the best control valve for a given application. My problem is that, as far as I can tell, only one control valve manufacturer includes an analysis of installed flow and gain in their control valve sizing application. In general, I tend to use the valves of a different manufacturer and, over the years, have become proficient in the use of their control valve selection and sizing application. I don’t have the time or enthusiasm to learn another valve sizing application.

A: I recently posted an Excel worksheet on my website www.Control-Valve-Application-Tools.com that calculates the installed flow and gain of a control valve in the system it is to be installed in, in conjunction with the user’s preferred control valve sizing application. “Enhanced version of graphing control valve installed flow and gain.” The Excel sheet can be downloaded at no cost. Figure 1 is a typical installed flow and gain graph generated by the Excel sheet. The worksheet has a “Read Me” tab that gives detailed instructions on how to use it. A third tab has copies of published articles on installed flow and installed gain.

The red dotted lines on the installed flow and gain graphs are placed on the graphs to show where your minimum and maximum design flows fit on the graphs. The maximum specified flow will always be at 1.0 on the installed gain’s Q/Qmax scale, and the minimum specified flow will always be at Qmin/Qmax on the installed gain graph.

Control valve Q&A
Figure 1. Installed flow and gain graph from the worksheet

The two vertical lines on the installed gain graph will always be in the same place for any valve sizes or styles that are being considered for the system represented by the user’s input of system parameters in Column D, rows 14 through 19 of the process model, making it easy to compare their control capabilities.

Control valve Q&A
Figure 2. Definitions of “Calculated from user supplied data” in the process model.
Control valve Q&A

Jon F. Monsen

About the author

Jon F. Monsen, PhD, PE, is a control valve technology specialist with more than 45 years of experience in the control valve industry. He has lectured nationally and internationally on the subjects of control valve application and sizing.
Jon currently hosts a website, www.Control-Valve-Application- Tools.com where he freely shares articles, training and professional development materials, and Excel worksheets that might be of interest to those who use or specify control valves. He can be reached at cvapptools@gmail.com.

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