PTS Flowbench Forum

Numbers reverse, static now higher than differential by the same amount.

larrycavan wrote:I'm with you on that for certain. The test pressure pickup location would cause me to question it's accuracy.

Did the bench read accurately before it was taken apart and compacted or not?

It did. Might have been just dumb luck, though. The footage of piping between orifices then was just a foot or so different, and now it has less bends.

The T-piece is necessary to avoid adding flow suction to the test pressure.

SWR wrote:

larrycavan wrote:I'm with you on that for certain. The test pressure pickup location would cause me to question it's accuracy.

Did the bench read accurately before it was taken apart and compacted or not?

It did. Might have been just dumb luck, though. The footage of piping between orifices then was just a foot or so different, and now it has less bends.

The T-piece is necessary to avoid adding flow suction to the test pressure.

IDK.... trying to compare an unknown to a changed but unproven unknown can be frustrating to say the least. All that is known and appears to be correct is that the inclined manometer scale correlates properly to it's 100% value. Outside of that, the rest is pure speculation.

I'd try a different arrangement for the test pressure pickup and see what happens. Perhaps something adjustable as in a piece of small tubing that you can move in or out until you hit the correct numbers. Not very scientific but sometimes you have to just drop back and punt when there's no clear path to the goal.....

Why can't you just make a reasonably sized chamber under the discharge hole and go out with the pipes from the bottom of the chamber. Put your test pressure pick up in the chamber away from direct flow impact. Shouldn't be difficult to fabricate that up.

Larry,

That's what i am doing with the 2-chambered bench now. I use that to make a hybrid that uses both settling chambers as "dead space" before the orifice and I'll hook the rest of the pipes to that. Easiest way to see if it makes a difference.

Brucepts wrote:Numbers reverse, static now higher than differential by the same amount.

Anther mystery??? Like my mysterious Dwyer U Tube that uses distilled water with green wetting agent. With both ends of the manometer capped, the fluid still vanishes over time. Kicker is that one would be led to believe that the caps leak to cause such a thing. Yet, the columns of water remain unequal as they became when the second cap was put on the U Tube's other leg...... Been trying to fathom that one for months. Even tried a few different caps....always fluid vanishes over time

Not a mystery, I would say. It's the effect of the pressure loss through the orifice. Just like I see here..

In an orifice bench, the top chamber contains two measuring points. One for test pressure and one for the orifice Dp measurement.

That stated, have you ever tried to tap into your orifice chamber on the leading side of the orifice with your test pressure manometer?

SWR wrote:Not a mystery, I would say. It's the effect of the pressure loss through the orifice. Just like I see here..

Unless you have to identical sized orifices as in that test example I don't think it has anything to do with what you see there. Could be wrong. Wouldn't be the first time or the last.

larrycavan wrote:

Flowbench layout mod small.jpg

In an orifice bench, the top chamber contains two measuring points. One for test pressure and one for the orifice Dp measurement.

I know. The two small golden-colored lines either side of the flow orifice is the location of said taps in my bench. You see a photo of an actual orifice somewhere in this thread, too.

That stated, have you ever tried to tap into your orifice chamber on the leading side of the orifice with your test pressure manometer?

Yes I have. Tried running the test pressure manometer from the leading edge of the flow orifice and the low side pressure of the flow manometer from the T-piece test pressure outlet. Differed maybe a couple cfm at most using the 300 cfm orifices. Also tried teeing the flow orifice low side and the test pressure taps together and running both manometers "interconnected" like they would be with a common vacuum source like in a chamber bench. No difference...