PTS Flowbench Forum

Brucepts wrote:

larrycavan wrote: Please clarify your calibration and CFM rating method for your plates.

If I have a PTS calibration plate with a xxx CFM written on it. Is it to be used to calibrate xxx CFM or (xxx CFM * .8)?

If the plate is to be used internally and is marked xxx CFM, is it really (xxx CFM - 25)?

I totally get it with over pressure situation. That's got nothing to do with my questions.

To clarify; if your scale (water or digital) is 100cfm the calibration plate I would recommend is 80cfm, 200cfm would be 160cfm, 300cfm would be 240 etc . . . some flowbenches on the market have various end ranges that are odd numbers, in that case I spec plates in what I consider "normal" numbers for ease of use as close to 80% as possible. This allows one to compare someone else's flowbench to another if they are all using my plates. As you know I can machine plates in any size that would be needed and I don't put the customer into a one size fits all, if someone would want a 223cfm@28" plate or some other what I would consider "weird" number I will machine it for them. I usually discuss this with someone when we work on plates for non-PTS flowbenches, I already have ranges worked out to work with the PTS Bench design with my DM.

Plates flow what they are marked so the internal plate cfm is what it is capable of flowing. But, it's over ranged by 25cfm per my design, it is still marked 625 or what other range is required by the customer. There is no conversion math needed by anyone using my plates.

larrycavan wrote: Are you saying that if a 600CFM range is desired that you make the plate 625 CFM? A 200 Range desired would result in a 225 CFM plate?

SWR wrote:Hi guys,

But. The problem now. I moved it, as in completely took it apart and moved it, now I am reassembling it to a slightly more compact form after a de-tour via a typical orifice bench, that showed too much flow at all times.. just like this now. I did not get the math to work out on it, but now it seems more like I have forgotten something about the setup of a bench as this current bench, although a very different design, shows the exact same numbers - too much flow for the test pressure - like the other one.

Brucepts wrote:

larrycavan wrote: Are you saying that if a 600CFM range is desired that you make the plate 625 CFM? A 200 Range desired would result in a 225 CFM plate?

Yes

1960FL wrote:SWR, I went back and reread your original post and as usual I had some reading comprehension issues! Am I correct in stating that in the way you are testing that if you Teed the test pressure (Vertical Monometer) into the high side (upstream ) of the orifice taps and ran your test the 300 cfm test part would flow correct it is only when you Tap the test pressure just under the test part that you get the pressure loss issue?

For clarification can you please explain the T plumbing in the picture, is it a pressure adjusting valve?

Rick

1960FL wrote:Swr, Is it much trouble to set up a pressure tap for depression right under the test opening?

I am having a hard time believing the footage of pipe from test piece to orifice would cause a 25% loss in pressure, but i am not sure the Tee is not causing some type of venturi effect on the pickup at the tee end messing with the reading.

Rick

1960FL wrote:Swr, Is it much trouble to set up a pressure tap for depression right under the test opening?

I am having a hard time believing the footage of pipe from test piece to orifice would cause a 25% loss in pressure, but i am not sure the Tee is not causing some type of venturi effect on the pickup at the tee end messing with the reading.

Rick

Brucepts wrote:Ok, ran a simple test just a few minutes ago. Using the digital manometer static pressure scale and a water gauge across the orifice plate. I tested two plates of exact same diameter (2.640) one internally the other one flat on top of the bench. Numbers followed along from 1 to 3" and then they started to spread out and the orifice scale started to increase over the static reading.

At 16" static I was showing 16.5" on the water gauge. This would work out to be a 5 cfm increase in flow

My digital manometer is calibrated to follow a water gauge across it's working range. The water gauge I used for this test is the one I use for calibration.

I ran the same test using total digital and saw the same results but I stopped the digital cfm scale at 16" (to avoid maxing the sensor out) and the static was 15.6", I do not currently have a second water gauge setup right now to run total water gauges on both channels.