Orifice plate support features - Should it be sharp edge or not

[MMack]

I have a 4.25" hole under the orifice plate in the panel that it attaches to. Should this be square edged or rounded? I can see that the top surface should be squared off to seal better. What about the bottom surface. My intention is that the whole is larger than anything I will use as an orifice, so it shouldn't come into the equation, but the top and bottom conditions won't be the same for a larger orifice. Don't know how often I will use that big a plate, but since I can't get to the underside without major surgery, I want to finalize this before I install it.

Thanks for the help.

Mike

[200cfm]

Good question. My plates from Bruce were the 6 X 6 size and the biggest office was under 2.00" I left square the top mounting portion of the board for the plate as you recommended and rounded or radius the underside portion. Not sure if square or radius makes a difference on air passing through on the exist side of the plate.

[MMack]

Thanks for the feedback, my thinking is that on the exhaust testing anything to minimize the differences will help repeatability.

Any other sage advice? I am a newbie, and therefore know just enough to be dangerous, or stupid. Oops, that was redundant!

Mike

[Thomas Vaught]

I typically have used square edged orificed (like SF does in their commercial benches).

Because the plate has multiple orifices and the outside dimension is 24" x 24" I never worried about an entry or exit prior to the orifice plate.
(This too is SF thinking on the SF 1200 bench which used stoppers).

I really like that bench design. The SF1200 bench is a "one direction" bench but I have seen little difference flowing from either direction with the multi-direction benches I have built in the past. Easy calibrated either way.

The next bench I do with have two plenums side by side with the orifice plate mounted between then and will use two "port holes" to move the stoppers accordingly.

The University of Miami showed me a bench they built like that and it was a very nice accurate orifice bench. Bench was over 5' long but not very deep (26") 42" height. It was built like a SF 1020 in appearance.

Tom V.

[MMack]

Thanks for the advise. I will leave the panel square edged. I should be installing it tonight, I painted the top side last night so I can install it and paint the bottom side this evening.

I have seen several people talking about only flowing in one direction. As a Six Sigma Black Belt this makes me cringe as you aren't testing in a real life condition, but if the data supports it, party on!!!

The more I learn about this stuff the more I realize how little I know. But that is why I am doing this, to learn!

Mike

[bruce]

[MMack]

Well don't I look dumb!!! Here's my sign!

I was thinking that they were going in an entirely different direction. Now it makes more sense. Thanks for clearifying what was obvious to everyone else. Now I am happy with what you all are talking about.

Mike

[bruce]

[MMack]

Warning!!! Learning curve approaching vertical!

Thanks for your patience and info. I want to learn, and I will. Very open ended....

Mike

[rusty105]

OK, just so I am clear, there are benches that do flow both directions, yes??

[bruce]

[Thomas Vaught]

MMack, who are you a six sigma Black belt with?

I work with a bunch of them in Ford Research.

Tom V.

[Maxflow]

If you flow only in one directiion and use hose to connect your exhost with, do bends in the hose create inaccurate readings. Also how large of hose would you need to use.
I am thinking that with a msd/mercdog bench this would
help with the leaking past the flow disk.

[SWR]