Modified EZ-Flow bench problem

[Brucepts]

Then I have tested with a separate U-type manometer, it shows the exact same value as my vertical manometer on the bench. I did some reading on the Flowbench 101 section and there it said you could not flow it with a test piece of the same size of the internal one? Is it something I do not understand..? As long as it is not bigger, it should be fine, right?

Pretty sure what you are referencing has to do with using a digital manometer, I find it's not good practice to run the pressure sensor to it's max so internal plates are rated higher than your actual test range. It's possible to max your sensor out, they are rated to take over pressures but why run that rise?

Water gauges would be able to run to their max over and over again, over pressure on a water gauge simple moves fluid into the over range well, or if home built out into the extra tubing.

Check and see if you have fluid trapped down stream in your tubing this will effect your readings as you would have compressible air trapped between the two fluids.

[1960FL]

Then I have tested with a separate U-type manometer, it shows the exact same value as my vertical manometer on the bench. I did some reading on the Flowbench 101 section and there it said you could not flow it with a test piece of the same size of the internal one? Is it something I do not understand..? As long as it is not bigger, it should be fine, right?

Do you have a smaller test calibration orifice say 150CFM?

I would start in range where you are generating good DetaP across the internal plate.

JMO

Rick

[SWR]

Very good. Your manometers check out when verified against another.

In the drawing I added A,B & C.

For Value of 17.5 @ Location C to be true then A to B Dp would have to be 10 instead of 7.5.

Assuming C as Total Pressure, 7.5 as Delta P across the Internal orifice. Providing I'm looking at this correctly.

Flowbench layout bench 3 small.jpg

DeltaP across the internal orifice is measured to 17.5-7.5=10". That leaves me with a DeltaP across the identical sized test orifice of 7.5. Are you saying I really should see C=20",B=10" and A=0"..?

[SWR]

1 = Inclined Manometer
2 = Vertical Manometer
X = Atmospheric Tap
Y = Flow Feed Pipe Tap

If 1 & 2 don't read identical when connected to X & Y then one or the other is reading inaccurately.
Not likely that the actual inch scaled manometer is reading incorrectly BUT possible the inclined scale could be incorrectly laid out.

They read exactly the same, if I connect both manometers to either pickups they show the exact same rise.

My inclined is a 1000mm / 39,3" ruler, so it's easy to see the exact rise to 0,1% accuracy. At 10" rise one inch of rise is exactly 100mm or about 4" long.

I calculate the flow from seeing say, 657mm pull on a 300 cfm orifice = 65,7% of range, then (square root of 0.657)= 0,8105% flow x 300 = 243,16 cfm. I did that just to make sure I would not need to hand make a percentage flow ruler that would not be as accurate.

What happens if you eliminate the inclined from the picture, hook up the U Tube in it's place and calculate flow from
Formulas instead of % reading?

As they show the exact same rise I would think there is no difference.. but I'll check.

[SWR]

Check and see if you have fluid trapped down stream in your tubing this will effect your readings as you would have compressible air trapped between the two fluids.

Bruce, I double-checked the tubing for leaks and cleared all of them with compressed air now. No difference to measured flow..

[SWR]

Do you have a smaller test calibration orifice say 150CFM?

I would start in range where you are generating good DeltaP across the internal plate.

JMO

Rick

Rick, I have over a dozen verified test orifices of varying sizes laying around. Just tell me what you'd like to see results from and I'll test it.
I can test with a 140 cfm one.. and I easily see 10" across the internal orifice. Problem is that it shows 100% of flow (in the current case, 305 cfm@10" internal orifice) when I pull just 7.5" Test Pressure on a test orifice rated at 300cfm at 10"... at 7.5" it is 259,8 cfm, not the 305 cfm it says on the inclined.

And if I try to pull 10" Test Pressure, the inclined runs out of range (obviously)...

[1960FL]

SWR
just so we are all on the same page please confirm the statement below or correct us there the number are different.
I may be a little confused here but by reading your post and making the assumption that your incline has ten inches of RISE or 10” Delta P and you are using a test pressure of 10 inches not counting in your correction factors for Beta Ratio a 300CFM at 10” sharp edge office would be like 2.649” 67.28mm, the internal since working on the same scale would be 2.667” or 67.74MM. So if all things were equal with this combination of plates your incline should read 9.67” of RISE at 300 CFM. At 7.5” you are uncorrected at 264.

Also if you could confirm a couple other simple but confusing specifications about the mechanics of the bench, Test pressure monometer Well type or U Tube? Incline Rise (Assumed 10” as that what you are stating) length of incline section and incline angel? This helps confirm calculations.

Last I wanted to see the test numbers on say the 140 (1.81” 45.97mm) to see if they are as proportionally off as the big orifice. Also the calculation for the flow rate of the top calibration plate is based on Ed’s sheet (basic flow through an orifice) and the one inside your bench should be based on your corrected calculation including beta ratio.


Rick

[SWR]

SWR
just so we are all on the same page please confirm the statement below or correct us there the number are different.
I may be a little confused here but by reading your post and making the assumption that your incline has ten inches of RISE or 10” Delta P and you are using a test pressure of 10 inches not counting in your correction factors for Beta Ratio a 300CFM at 10” sharp edge office would be like 2.649” 67.28mm, the internal since working on the same scale would be 2.667” or 67.74MM. So if all things were equal with this combination of plates your incline should read 9.67” of RISE at 300 CFM. At 7.5” you are uncorrected at 264.

Rick, the inclined is setup to have a rise of 10". The internal one is a 67.12mm / 2.6425" and it flows 305.1 cfm at 18ºC at 10" WC, due to being inserted into a pipe of just 125mm / 4.921" the Beta ratio is a bit different, I can check with the calculation program the exact values for the whole calculation later today. The test orifice is 67.04 / 2.6393".

Also if you could confirm a couple other simple but confusing specifications about the mechanics of the bench, Test pressure monometer Well type or U Tube? Incline Rise (Assumed 10” as that what you are stating) length of incline section and incline angel? This helps confirm calculations.

Test pressure manometer is a well type. Inclined rise with subtraction of the minimal rise of the well is 258 mm -4 mm = 254 mm / 10.00". Inclined section is 39.3" / 1000 mm. Exact angle I would have to measure later today.

Last I wanted to see the test numbers on say the 140 (1.81” 45.97mm) to see if they are as proportionally off as the big orifice. Also the calculation for the flow rate of the top calibration plate is based on Ed’s sheet (basic flow through an orifice) and the one inside your bench should be based on your corrected calculation including beta ratio.


Rick

I'll do the test and calculations later today and post the findings and the numbers.

[SWR]

The 140cfm orifice I have is calculated by the program to have 140.243 cfm flow at 18ºC inside a 120mm pipe, have a Beta ratio of 0,388, Alpha ratio of 0,607 and will make a pressure loss of 8,34" H2O using the correct Isentropic exponential, density and viscosity index for the temperature in my shop. It has an internal diameter of 46.55mm / 1.8326".

Running that test orifice on the same internal orifice as before, it pulls 2.53" of inclined height, that's 0,503% of range on an orifice that I double-checked the calculation on, it is 305,246 cfm. That gives a flow of 153,536 cfm at 10"...

The inclined angle is as well as I can measure it 15º.

[1960FL]

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