Control.com - Nerds in Control

Hi everyone,

I am looking for information about how to modeling (matlab-simulink, it would be great!) a control equalporcentaje valve, the model is
going to be used in a control algorithm test for my thesis, anyone have some ideas?

Thanks

Mark Lezama

Hi Mark;
I suggest to take a look at EASY5 from the Boeing Company. This is a simulation package, this has an extensive hydraulic library of devices.

I would suggest contacting your Vendor or Factory for the valves. They may have a "free" software sizing program for these valves. The sizing programs that I have received are pretty simple to use.

Jerry Curtis

Hi Mark,

Sorry I haven't replied sooner - but I've been away at a paper mill doing exactly what you want (i.e. modelling process plant, including
valves, in Simulink).

We model valves using simple look-up tables (obtained directly from valve data sheets) that convert percent valve opening to Cv (which
relates % of max flow to % opening at constant pressure drop). This is then converted to give valve admittance, which can then be combined with
the admittance of any pipes in parallel or series with the valve. The valve characteristics (e.g. equal percent, linear etc.) are embedded in the look-up table.

The pressure drop (or flow, given pressure drop) is then calculated from the standard equation:

pressure drop = (flow)^2 * fluid density / admittance

Thanks to my colleague Gerrit van der Molen for helping with this explanation.

I hope this helps. Regards.


Andy Clegg________________________________________andy@isc-ltd.com___

Advanced Control Technology Club, Industrial Systems and Control Ltd.,
50 George Street, Glasgow, G1 1QE Tel: (+44) 0141 553 1111
http://www.isc-ltd.com/actclub.html Fax: (+44) 0141 553 1232
______________________________________________________________________

In the book "Principles and practice of automatic process control" by Carlos A. Smith and Armando B. Corripio (ISBN 0-471-88346-8) you can find a good explanation, and the equations, of that kind of valves.

Regards, Josue

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