control valve sizing for extremely low flows
control valve sizing for extremely low flows
(OP)
Does anyone have good, proven sizing equations for extremely small control valves (Cv less than, say, 0.01) for liquid services, where the flow through the trim (much less the body!) is clearly laminar?
Unless I've missed something, the typical low flow control valve manufacturers (Kammer, Baumann (now Fisher), Badger Research etc.) don't give you anything useful on this subject. It's not mentioned in Fisher's otherwise very useful little black book. Viscosity corrections exist and are given but don't apply to this case. And I can find equations for laminar flow control valve sizing on the 'net, but without references as to where they're from and what data they're based on etc. I'm about as suspicious of using that sort of stuff as I am about eating food I find lying on the ground...
Unless I've missed something, the typical low flow control valve manufacturers (Kammer, Baumann (now Fisher), Badger Research etc.) don't give you anything useful on this subject. It's not mentioned in Fisher's otherwise very useful little black book. Viscosity corrections exist and are given but don't apply to this case. And I can find equations for laminar flow control valve sizing on the 'net, but without references as to where they're from and what data they're based on etc. I'm about as suspicious of using that sort of stuff as I am about eating food I find lying on the ground...





RE: control valve sizing for extremely low flows
"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
***************
http://virtualpipeline.spaces.live.com/
RE: control valve sizing for extremely low flows
Aside from experimentation (which we're doing!), is there any way to a priori know the pressure loss across this valve, such that you can select the right one for the job- based only on the turbulent flow Cv value the vendor gives you?
I can't imagine I'm the first person to have asked this question! People have been using needle-type control valves for a very, very long time...but so far, a web search turns up nothing I feel comfortable using...
RE: control valve sizing for extremely low flows
RE: control valve sizing for extremely low flows
"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
***************
http://virtualpipeline.spaces.live.com/
RE: control valve sizing for extremely low flows
BigInch: single Cv value- that's all you get to choose from when you buy 'em.
RE: control valve sizing for extremely low flows
Is there some reason you can't use that Cv?
Is it linear, equal percentage, or what type?
If you know the type, you can relate Cv to %open.
"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
***************
http://virtualpipeline.spaces.live.com/
RE: control valve sizing for extremely low flows
RE: control valve sizing for extremely low flows
They do exhibit reasonably good Cvs for gases, even down to the triple zero Cv size. But they're in error for viscous liquids, and the standard viscosity correction factors don't work.
RE: control valve sizing for extremely low flows
RE: control valve sizing for extremely low flows
RE: control valve sizing for extremely low flows