Tiny Orifice Plate Sizing 1

[ChEMatt]

I'm sizing an orifice plate for flow reduction, as the upstream (on/off) dump valve has a very large CV and we're concerned about emptying the tank before the operator can close the valve.

Using equations from McCabe, Smith, & Harriott I solve directly for the beta ratio, which comes out to be 0.06 for the desired flow. The pipe size is 0.5" tubing, and the orifice hole, therefore, is 0.03". This gives me a Reynolds number of 8566 in the upstream pipe, which, according to the literature, should cause me to look closely to the value for C that I am using.

Since I am not measuring flow, but simply trying to reduce the rate, is this anything to be concerned about?

Thanks for the help!

Onwards,

Matt

 

[JLSeagull]

If choices exist in the equations or program, assure that you select pipe taps not orifice flanges. Pipe taps assures permanent loss. Orifice taps would measure across the vena contracta but most pressure recovers after an orifice plate.

 

[ChEMatt]

JL,

Thanks for the advice. There are no options for this; it's my own spreadsheet using an equation from the literature.

I ran a couple demo programs over the weekend and I'm spot on with FE-Sizer, so I figure I'm OK. Since we're just trying to slow the flow, this should suffice.

Onwards,

Matt

 

[moltenmetal]

Personally I've always preferred a metering valve to a fixed orifice personally. That way, when it plugs, you can always open it a bit more to clear the blockage and get the thing drained. Costs about the same as a filter upstream of the orifice, and way more effective. Don't want the operator to fiddle with it? Adjust and then remove the handle...

Begs the question: why are you using 1/2" tubing if you can tolerate that much pressure drop? Why not a smaller valve and 1/4" heavy wall tubing?

 

[ChEMatt]

moltenmetal,

I think the metering valve is a great suggestion; I wasn't familiar with those previous to your post.

Probably could go with 1/4" tubing all the way to the downstream drum, but it's already installed and replacing that tubing, and the associated heat trace, would be expensive and delay things.

I like the metering valve option. Have a star!

Onwards,

Matt