Pressure drop across the orifice plate

[Brucepts]

Small pressure differential = larger orifice hole = more turbulence through orifice plate = bouncing readings

What is the perfect differential pressure? Probably the "Million Dollar" question? How to test this? I had played with this and shared my thoughts on the old forum when I was working on water gauges for my PTS Style flowbench. 10" rise was found to be the best in my opinion. Good size orifice holes and less bounce than 6-8"

We are still working on recovering the old posts and putting them into a new forum for reference . . .

[Tony]

Now this thing came to my mind:

When I have just two vacuum motors should I use as small pressure drop across the orifice plate as possible to make max test pressure bigger?!

Small orifice pressure drop has the advantage of giving you more flow and pressure available at your test piece, as you suggest.

But there are some definite disadvantages to doing that.

A low orifice pressure drop means the orifice will be far more susceptible to any slight up stream air turbulence or flow instability. A higher orifice pressure drop means a lot more violence and fury at the orifice, and the readings will be more stable.

The other disadvantage is your sloping manometer will be almost horizontal, making it more susceptible to changes in level (if you have an uneven floor) and any slight bend in the manometer tube.

For best accuracy, always use the highest orifice pressure drop you can afford to use with whatever air blower you have. But the choice is entirely up to you.

[MatiasAho]

Thank You! I got some new information to think about!

[zums]

86 rocco, in your flow calc. sheet- what do you mean by , if your using a dwyer durablock #246 red fluid "use 6" as 100%"

[86rocco]

Because that particular manometer is used in Superflow bench and because a few members here also use that manometer I thought it was worth a footnote.

Anyways, if you use happen to be using that manometer with the red 0.826 sp fluid, 100% on the inclined manometer scale corresponds to a 6" W.C. differential pressure.

[coulterracn]

This is a picture of the Dwyer Model 246 incline manometer