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# Needle Valve Cv Calculations

## Needle Valve Cv Calculations

(OP)
I'm looking for literature on the design of needle and seat valves or ball and seat valves, but short of that I'll take a general rule of thumb for flow through an orifice with a centerline obstruction (i.e. like a needle valve). Is there a way to approximate the loss given the open area and shape. There are tables a plenty for orifices of every shape and size under the sun, but I'm having trouble locating one for an orifice with something in the middle.

### RE: Needle Valve Cv Calculations

(OP)
I understand there may not be precise literature but i'm sure someone has developed a rule of thumb by now for at least a few simple shapes.

### RE: Needle Valve Cv Calculations

Did you search for needle valve CV??

You get things like this https://www.idealvalve.com/flowcal.htm

And many other options.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

### RE: Needle Valve Cv Calculations

Hello,

Lyon's Valve Designers Handbook section 22, Fluid Throttling Devices, provides K formulas for a wide variety of fluid throttling configurations. Including ball valves, needle valves, butterfly valves, various slot configurations, relief valves, notches, etc. I believe this is what you need.

### RE: Needle Valve Cv Calculations

(OP)
LittleInch,

Thank you for the response. Yes, I had come across this, and it is nice but mainly deals with that one valve, specifically. It covers a few orifice sizes and relates Cv to number of turns but there is no data on what's actually happening at the needle itself.

BCD,

WOW! Lots of good information in there. I might actually purchase the book to add to my library. Still pouring through it but I don't know if it is exactly what I need but its about as close as can be without actually being it. I might even be able to use the info you pointed to, to make a good approximation. Thank you. Seriously old book. Sadly, these sorts of books aren't published anymore as far as I can tell. Either everybody that would publish believes all the info that's publishable is already out there or companies got wise and scooped up all the brains that would publish this sorts of stuff and are keeping all this info in house. There is a Pump Handbook that is ancient and just as data rich and goes for about \$1,000 on eBay because it is no longer published. Again, thank you for the heads up.

Edit: Looks like I spoke too soon. This has exactly what I need and other information for another project I'm working on that I'd basically given up on due to having no starting point and I don't have the time, resources, or possibly brain power to start from scratch. These gems should be shouted from the rooftops in engineering classes but they aren't. Thank you.

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