The best oriffice Pressure Differential and sensor postion

[ftch]

I have my PTS bench running, its awesome.

I have no problem pulling over 500 cfm at 28 inches with a high differential reading of 10.5 "
The 10.5 is the pressure difference across my PTS 660 cfm flow plate which is inside the bench. I have a solid Radius test piece mounted on the bench no bends.

What do members feel regarding as a ideal flow plate differential pressure.
The dwyer 246 is only 6" is 4 to 6" all you need. Is 10" definately better. Does a high pressure make bench pulsing more pronounced?

I have a small amount of pulse which I have established is in the lower chamber
it is around 0.4 of an inch at worst. I am currently using fluid manometers. I would like any input into this

I really appericate this forum and being a part of it.
Michael Marriott
Australia

[jfholm]

I have my PTS bench running, its awesome.

I have no problem pulling over 500 cfm at 28 inches with a high differential reading of 10.5 "
The 10.5 is the pressure difference across my PTS 660 cfm flow plate which is inside the bench. I have a solid Radius test piece mounted on the bench no bends.

What do members feel regarding as a ideal flow plate differential pressure.
The dwyer 246 is only 6" is 4 to 6" all you need. Is 10" definately better. Does a high pressure make bench pulsing more pronounced?

I have a small amount of pulse which I have established is in the lower chamber
it is around 0.4 of an inch at worst. I am currently using fluid manometers. I would like any input into this

I really appericate this forum and being a part of it.
Michael Marriott
Australia

Here is the way I see it. True if you test with a lower Delta Pressure across the internal orifice you can test at a higher pressure. I feel it is good to test at a higher pressure for sure. Let's take a look at everything and hope we can help you make an informed decision because it is your decision how you test.

If you test at a low delta pressure across the internal orifice the test can be a little less accurate and not as stable. Also your capacity for the internal orifice drops. As an example if your internal orifice is 3.00" with a CD of .62 at 2" H2O it's capacity at 100% would only be 172.6 cfm. If you increase your delta p to 12" H2O then your capacity at 100% would be 422.7 cfm. Now if you flow at a delta p of 16" H2O like Bruce's PTS digital manometer is set to then the capacity of a 3.00" orifice with a .62 CD would be 488 cfm at 100%.

Now let's compare apples to apples here. With Bruce's setup, the DM and test pressure of 28" H2O so you have 28" test plus 16" delta p for a needed 44" H2O from the motors. So at 28" test pressure and 100% on your inclined manometer reading you would have a theoretical 488 cfm reading. Now keep in mind we are using a total of 44" H2O just so we can see the difference. Now if you test with the delta p set to 2" H2O that would leave 42" H2O for test pressure, but your 100% reading on your inclined manometer would only yield 172.6 cfm. Yes your test pressure is much higher but your stability and capacity are compromised.

Right now I personally am using 12" delta p, but I may go to the 16" H2O on my internal orifice. Ideally I would like to see a test pressure of 36" H2O at least or if possible 42" H2O with a delta p of 16" H2O on the internal orifice. Just remember if you are going to test at the higher test pressures be sure your bench is braced well.

John

[ftch]

Thanks once again John

I have a much better understanding of how everything works now, beem extremley valuable.

regards
Michael Marriott
Australia

[ftch]

Bruce Thank you

I be the first to say electronics is not my thing,

I started with fluid manometers and now I understand the bench. Im glad I did .
I am about to do hook up your digital in the next few days .

I notice on a SF 600 may have been a 750 they use blue guage oil with a higher specific gravity and scaled to suit, Im sure the high Specific gravity helps dampen the manometer.

regards
Michael Marriott
Australia

[ftch]

Bruce Thank you

I be the first to say electronics is not my thing,

I started with fluid manometers and now I understand the bench. Im glad I did .
I am about to do hook up your digital in the next few days .

I notice on a SF 600 may have been a 750 they use blue guage oil with a higher specific gravity and scaled to suit, Im sure the high Specific gravity helps dampen the manometer.

Another thing I was playing with is, the single pick up test pressure fluid manomoter is smother, Than the DP manometer because it is only measuiring one pressure.
The DP manomter is measure pressure top and bottom so it exgerates things more. Would it be better to just measure DP below the orifice and then subtract the pressure from above mathmatically. This could be done easily in the software I presume ( big presume). These are just observations, The bench is great.

regards
Michael Marriott
Australia