Hahaha thanks. Yeah, it’s one that I’m probably most proud of, and I was learning as I made it. I think it’s probably a little niche. But the point is I’m not chasing views, if there are a handful of people that really benefit then I’ve achieved what I wanted to achieve! Thanks for the nice comment.
Great discussion about control valve characteristics. I'd worked with several control systems and getting the linear behavior was always a key part of getting good control performance. One notable problem was a control valve to regulate steam flow to an auxilliary turbine that was coupled to a centrifugal pump where the end goal was to control the flow via pump speed. So first the system curve, then the pump curve, then the hp vs pump speed, then steam flow vs turbine power developed, then finally steam flow vs valve percent opening. Ugh... So naturally, we did some manual tests at various points, plotted things out and made a 'little black box' of electronics that converted linear flow controller output to the desired valve-open command. Process flow control systems have always been fascinating for me, and I've enjoyed your videos on the topic. Thanks you.
I remember studying this particular topic during my chemical engineering course and I didn't get very much of it. This was very well explained and understandable
Yes, I certainly had the same experience. It is something that is fairly easily demonstrated and hopefully sticks, rather than needing someone to memorise it and parrot it later (which I was doing before going through this exercise). Thanks for the comment.
Great explanation. I am a Quality GM with Doosan, and i am able to understand Control Valve design. Thank you very much for your explanation and hard work.
You are a gentleman and scholar! Excellent explanation. I love workbooks like this, I have added your workbook to my toolbox. greetings from a test engineer.
One other thing to keep in mind is that Eq% works better when you have a normal flow close to the low end of the valve. For instance, say you normally need 2 gpm of flow through a valve, but there are times you want 10 gpm lose when you want to quickly fill a tank but after doing so, you need much less flow to maintain that level. The Eq% gives you better resolution and finer control at the lower flow while allowing you to still have high flow when you need it. The quick opening trim can give you better resolution and finer control when your normal flow requirements are close to your maximum flow rate.
Pats, how would you go from a % opening vs CV plot to a % opening to a flow rate plot. That is the part that confuses me. Also would the CV only work for one specific pressure drop?
Nice. A question. You said that some of the valves had higher operating cost. But if we are hitting the same targeted flow of 30 with all else being the same in the system, then we have the same delta-P across the valve to achieve it. Isn't the pressure capacity of the pump vs the chosen operating pressure what selects for cost? Though I never studied chemical engineering and I'm a college drop out so I may have it wrong.
How did you calculate the value of 0,7 when you choose 25% ▲p of the total pressure drop i didnt get that? could you please explain that or some one :)
