Control Valve Sizing

http://www.iceweb.com.au/Valve/Control%20Valves/Masoneilan/DeaeratorLevelControl.pdf

Open a dialogue with the local friendly Valves Distributor, and get that organisation to provide a quotation. That way, the liability for getting it right lays with that organisation.

Is this the same control valve?

How did those calls to the Valves Distributor go?

The Valve Distributor will need to know the fluid and its temperature, among other things of little interest to the Mechanical Engineer.

That's the right basic approach. I assume it's water as it's a deaerator. If you calculate line loss at maximum flow that will you minimum valve ΔP hence max Cv. As the valve will most likely be smaller than line size, divide by 0.8 swaging factor to get required Cv. But if it's a control valve you probably need to consider other conditions. Calculate minimum Cv from minimum flow and maximum valve ΔP, based on lower line loss, plus any higher upstream pressure or lower deaerator pressure, if that's a possibility. Use swaging factor 0.9 or 1 for safety.

That gives the range of Cv, needed to correctly size a control valve. Give that to the valve supplier, along with the water temperature, to check for cavitation, which could be a problem at this sort of ΔP.

As it's a 800mm dia line it's going to to be a big valve, I doubt there are many suppliers who can do it. Check what they offer, they're not all too competent, though at this level one hopes they are. In the past I have given all the process data to valve suppliers, with line size, saying valve size to be advised by supplier, assuming it would be 1 or 2 sizes below line size. Sometimes they would ignore the process data completely and just quote a line size valve.

The link below to a valve manufacturer has a calculator for your purpose.

https://go.emersonautomation.com/FSMDownload

It has specification manager software.

It should be useful even if you do not use their brand of valve.

It took less than 30 seconds to find it.(yawn)

Good luck!

⇒ "The Chemical Engineer" magazine, April 2021, pages 48-50.

⇒ "Rules of Thumb for Chemical Engineers" 6th Edition, by Stephen Hall, (Elsevier, 2018)