Modified EZ-Flow bench problem

[SWR]

Thanks SWR, I am a little confused are you not setting the calibration orifice directly on top to the bench? it too is in a pipe?

Please clarify as the test orifice should not have any alpha or beta ratio applied to it the only corrections are for the internal (In the pipe) orifice.

To a point if this is a sharp edge orifice then the od puts up more like 144CFM not where we want to be but a lot closet than the 300.

Rick

Rick, yes it is, and it has an extension that leads to a bellmouth where it's fed. I did that because the industrial program I am using can't calculate open air on one side and say 4" diameter pipe downstream in one calculation, the difference from "open air to open air" across it vs. "open air to small pipe beneath" is significant. So I made the scenario to something that the program could calculate. But, as you say, it's only a very few cfm, so it should still work to iron out the big bugs.

[1960FL]

SWR, so this is starting I think to make sense it we look at the test results you Delta P is .4" high at abut 50% scale and is 2.5++ inches high at 98% scale. So as I think both Bruce and Larry have eluded to, one should start by looking for leaks/blockages

1.) in the pickup tubing on the low side of the Delta P/Test pressure tap
2.) blockage in the well vent on the vertical monometer or leak at the tap side
3.) possible turbulence at the low side pickup of the DP connections or leak at the orifice there.\

Will think about this some more.

Rick

[SWR]

SWR, so this is starting I think to make sense it we look at the test results you Delta P is .4" high at abut 50% scale and is 2.5++ inches high at 98% scale. So as I think both Bruce and Larry have eluded to, one should start by looking for leaks/blockages

1.) in the pickup tubing on the low side of the Delta P/Test pressure tap

Double-checked for both manometers. I can pull the water to any height, block it and it just stays there indefinitely.

2.) blockage in the well vent on the vertical monometer or leak at the tap side.

Has a quarter-inch hole I can see right through on one side, the other holds the height, as mentioned above.

3.) possible turbulence at the low side pickup of the DP connections or leak at the orifice there.

Could be turbulence, but I would think the air had straightened out a bit after moving over a yard in straight line? The orifices are true "corner tapped" too. As far out to the side that is possible and literally touching the orifice plate. The whole system is steel piping with double-lipped internal rubber seals and duct-tape over all joints. Using a 10mm (just over 3/8") flow orifice I get less than 0.3" flow depression at 70" on the vertical. That's 0,035 of the full scale, just over 18% flow. 1.87 cfm. I can try to expand the piping before the straightline to the orifice to 200mm / 8" to see if it makes a difference..

[1960FL]

SWR no I would not change anything if this bench worked before than we need to resolve the issue I am just asking these questions to better understand the bench, I have been traveling and just got home from picking up another project I do not need, I will try tonight to go back to the old forum archives and dig up your thread on your build I vaguely remember it but I hope it will trigger some thought. Sorry I have not been so much help yet just getting all the information.

can you post the math formula you are using in your flow calculation or is just in the industrial program?

Rick

[SWR]

SWR no I would not change anything if this bench worked before than we need to resolve the issue I am just asking these questions to better understand the bench, I have been traveling and just got home from picking up another project I do not need, I will try tonight to go back to the old forum archives and dig up your thread on your build I vaguely remember it but I hope it will trigger some thought. Sorry I have not been so much help yet just getting all the information.

can you post the math formula you are using in your flow calculation or is just in the industrial program?

Rick

Rick, it did work before. I used it for years, and the numbers of heads I did was verified by other known good benches as far as I know from my customers. Never had anyone come back and tell me my numbers were a mile better than reality, at least. Mine was even a little "mean", it did not give quite as big numbers as some of my competitors benches on the same heads. The strange thing is that I had just the same manometer results on a big 2-chambered bench - the one I gave up on - using the exact same orifices (just without the tubes), so I have a question for all of you guys, as I think my issue is math/physics related:

If you use say, a 2.5" orifice inside your bench, and another one of the exact same size as the test orifice, or ANY size test orifice that is the exact size as your flow orifice, do you really see a pressure drop across the test orifice that is exactly as high as the inclined manometers rise? I.e., when you pull 100% flow on an incline with a 7" rise, you have a test pressure of 7"..? 9" test pressure on a 9" rise manometer, and so on?

So that if you pull that, stop the bench without touching anything, unhook your pressure taps and measure every part by restarting the bench and testing each tap by itself, it would give 0" for outside of the bench, 7" for the pressure below the test orifice and 14" after the flow orifice?

[SWR]

I just noticed an interesting correlation.. the calculation program gives me the flow and many other values. Herein also the flow loss through the orifice. I was just playing around with calculations trying to find ANYTHING to go on with - as I am about to not have much hair left to pull out and I have lots of jobs in the wait for this - and just for kicks I flowed the 140 cfm orifice again, using my 305 cfm flow orifice. It flowed about 153.5 cfm. I then calculated the 140 cfm test orifice x (sq.rt test pressure / sq.rt. the pressure loss).. hey presto. 153.3 cfm.

Close, so I tried again using the 200 cfm test orifice and the flow loss value for that orifice. Same formula gave the same result, it flowed within 0.5% of what it should have. It does correlate all the way to a 60mm / approx. 250cfm test orifice. So it seems it is related to pressure loss... in some way.

[1960FL]

SWR

If you use say, a 2.5" orifice inside your bench, and another one of the exact same size as the test orifice, or ANY size test orifice that is the exact size as your flow orifice, do you really see a pressure drop across the test orifice that is exactly as high as the inclined manometers rise? I.e., when you pull 100% flow on an incline with a 7" rise, you have a test pressure of 7"..? 9" test pressure on a 9" rise manometer, and so on?

If I am understanding your question correctly your incline monometer is representing the differential pressure between the test apparatus and the motor box side. say 10" rise and a test pressure of 10" then the motor side must be pulling 20". and with each orifice we see some pressure loss. It is my understanding there are two industrial formulas used to determine orifice flow in a pipe and one is actually used for determining pressure losses across the orifice and not intended for flow. I have attached a link that may be of interest it is an issue I am facing with a port I am personally working on and I came across it in my research. The issue I think is that when approaching 100% on the internal orifice for ones scale the velocity across the orifice is higher than that of the test piece thus stealing energy in the form of pressure that cannot be translated to pulling the 100% of the calibration orifice thus you are over driving your internal orifice to try to get to the 10" of test pressure.

http://www.aft.com/easyblog/entry/2015/ ... -equations

[SWR]

If I am understanding your question correctly your incline monometer is representing the differential pressure between the test apparatus and the motor box side. say 10" rise and a test pressure of 10" then the motor side must be pulling 20". and with each orifice we see some pressure loss. It is my understanding there are two industrial formulas used to determine orifice flow in a pipe and one is actually used for determining pressure losses across the orifice and not intended for flow. I have attached a link that may be of interest it is an issue I am facing with a port I am personally working on and I came across it in my research. The issue I think is that when approaching 100% on the internal orifice for ones scale the velocity across the orifice is higher than that of the test piece thus stealing energy in the form of pressure that cannot be translated to pulling the 100% of the calibration orifice thus you are over driving your internal orifice to try to get to the 10" of test pressure.

http://www.aft.com/easyblog/entry/2015/ ... -equations

Rick,

What I am asking is if any of you have in essence zero pressure loss in your benches? If you have a 6" rise on your inclined manometer, and you pull 6" of test pressure, and both orifices are identical in size, you will have pressures of 0" before the test piece / 6" after it and also 6" before the flow orifice / 12" after the flow orifice when you pull 100% on the inclined, hence zero flow loss through orifices. Is that even possible given that both orifices have identical sizes?

It is just like in a cylinder head. When you reach close to .25 L/D you get both the worst loss of the valve window and the most loss of the port wall friction, hence the coefficient is at it's lowest at that point. A double whammy. That's why kicking the valve past that point is the only way to make the port work. Below that the port does almost nothing, it is all in the valve window.

I'll roll in the 2 chambered bench again and see exactly how much the results differs from the pipe bench. Given that any wall effects and friction losses through the pipes then are negated, if the results are the same again atleast I have taken some of the issue out of the equation.

[Brucepts]

What I am asking is if any of you have in essence zero pressure loss in your benches? If you have a 6" rise on your inclined manometer, and you pull 6" of test pressure, and both orifices are identical in size, you will have pressures of 0" before the test piece / 6" after it and also 6" before the flow orifice / 12" after the flow orifice when you pull 100% on the inclined, hence zero flow loss through orifices. Is that even possible given that both orifices have identical sizes?

I have never done this test on my bench reading the same static as depression testing, Rick and I chatted about this last evening on the phone and I'm going to do some testing on it. I am machining a few sets of customer orifice plates either today or Tuesday and can test the plates against each other at my rated internal DP pressure of 16".

As a design note I over-rate my internal plates by 25cfm so I am not up against the max on the digital pressure sensor. I also recommend on calibration plates they be rated at ~80% of the scale cfm for calibration, I find this number works the best. No specific reason for ~80% just what I have found over the years that works for all bench designs I have supplied calibration plates for.

Might be a day or two before I get to run this test on my flowbench, I have a few orders to get finished this week.

[Tony]

I tried something like this a very long time ago, and it does work.
Two identical orifices in series will generate equal pressure drops. its really interesting because the absolute pressures and air densities are different, but the differential pressure drops end up being the same.

Ain't nature a wonderful thing !