orifice plate leaking

[Thomas Vaught]

A Deck Plate Port Hole, such a simple little idea, that I had, that has made so many people happy!
(Including Super Flow!) LOL!

Tom V.

Wish I had made some money off the deal!

ps I did some playing around with sizing of the orifice holes and have come to the conclusion that a 50, 75, 100, 150, 200 hole combination
will give 575 total cfm capability but will give about 29 different ranges in 25 cfm increments. Also the combinations offer about 13 cross checking orifice combinations (more than one orifice combo for the same cfm)

[Nick]

Tom

Why do you think having such a small difference between sizes is so important? I did 50, 100, 150, 200, 250, 300, The only one I use right now is the 200. I did not find a big difference using the three smaller holes. I think the biggest difference was 2cfm. But it is very repeatable just using the 200. I suppose there nice to have if you want to get real accurate. The lowest reading I get on the heads I'm playing with is 13% and it figures out the same number as if I use the 50cfm hole, so I just stopped messing around with it.

I think Superflow was on to something when they did there 200, 400, 600, in the 1200 bench.

Also, say you wanted to stay above the 50% line, you would only need, 50 100 200 400.


What do you think? I just don't see the big bad turn down ratio that Ive read about. Electronics may not see the difference between 13% and 14% but I can!!!!!!!! That's 2cfm on my 200 orifice.


Feel free to tell me I'm nuts.

I'm not saying it's wrong, I'm just curious as to your reasoning.



Nick

[larrycavan]

[larrycavan]

[Thomas Vaught]

When I did the layout on one of my first orifice plates, I copied the basic ranges of a SF 1200 bench as I liked the design, (200, 400, 600 holes) with rubber stoppers.

A couple of years later I installed the first "port hole" in a SF 1200 bench, except on that bench I had also added a 100 cfm hole. The ranges were 100, 200, 400, 600 with none of the larger holes being able to read the smaller hole as a cross-check on the flow (assuming you wanted to be above the 70% range or higher). The 100 hole was 50% of 200 hole, 200 hole was 50% of the 400 hole. The 400 hole was better but still was only 66% on the scale.

A couple of years after that I made more plates and put in a "Dice" pattern 5 hole arrangement: 50 cfm, 100, cfm, 200 cfm, 400 cfm, 600 cfm. It worked well except I rarely used the 600 cfm hole or went as high as 1350 cfm.

I saw the value of cross-checking holes and played around with the hole sizes for cfm to try and get many ranges with a few holes and also a small cfm change per range. Now I had 50, 100, 200, 300, 400 holes where I could do 100 cfm steps and test using only one hole or still
do 1050 cfm if I needed it. I could also do some cross-checking: 100 + 200 holes = 300 cfm hole, 100 + 300 holes = 400 cfm hole, etc.

86rocco proposed to me a hole combo that was "different" for his bench:
I believe he had a 50, 75, 100, 150, and 250 sizes. Help me out here, Ed.

The point is he had looked at things differently:

Range 1 50 cfm
Range 2 75 cfm
Range 3 100 cfm

Now Range 4 was range number 1 plus Range number 2 so 125 cfm.
Etc, etc, etc. But basically he could do 25 cfm increments just by having the 75 cfm hole size as one of the holes. It also worked out that the combinations opened up a lot more for cross-checking. Like 9 possible
cross-checks over the whole range.

Simple is good but some people like my buddy want to be dead on with the number and want to work on the top part of the scale all the time.

The FP stuff with do that but we are talking non electronics here with my friend.

I think this is also one of the ways that SF is using their many orifices to calibrate their benches.

Last but not least.

I don't know if many of you have looked at the Orifice calc sheet in detail but it gives AREA of the hole.

If you plug in the normal .62 cd using a 2.5 sq in hole area you wind up being a few cfm over 50 cfm. Same deal for the 5 sq inch deal: a little
over 100 cfm. You do this for all of the SF 300 ranges: 50, 100, 200, 300, 400 and you find that they are all over the range value using the .62 value. You change the cd to .586 and guess what all of the holes match
the range perfectly.

What I think SF did was they knew it would be very hard to do a perfect .62 cd plate every time on every hole so they decided to make a square
edged orifice vs a sharp edged orifice. They possibly tried different material thicknesses and materials until they could consistantly machine a hole that was about a .586 cd on the SF 300 bench. The ones I have tested are pretty darn close to being on the number.

With the later SF 600 benches it seems they would just REPORT the calibration number vs trying to hit the number every time.

I reported in a earlier post about the .586 cd number. This is where that value came from.

Tom V.

[86rocco]

[larrycavan]

[Thomas Vaught]

Larry,

Quote:

"I don't understand what you mean there???"

You take a "calibration plate reading" using the 100 cfm hole in the "orifice" plate, say the calibration plate reading was 75 cfm. You read 74% on your manometer scale. Pretty close.

You now want to check that reading by using the 200 cfm "Orifice" plate hole. You take the reading and the manometer reads 39% on the scale. .39 times 200 = 78 cfm. Is it the actual reading or is it that you are not in the straight line part of the curve on the orifice? Every orifice has a sweet spot in the accuracy. Typically that is at 70% or higher. That is my point, try and test as much as you can in the 70% or higher range on the manometer.

Quote:

"The SF calibration / range values part makes perfect sense." Thanks.

Quote:

"What I'm wondering about is where you found the best location for the manometer probes with the holes being fashioned in the dice pattern. Did you find any particular location that seemed better than others?"

I put the probe for the orifice plate coming from the back of the plenums, 1/4 inch off the surface using a stick-on tube support, and the probe was 3 inches away from the top of the center (smallest hole) in the dice pattern. The other orifice holes were a farther distance away. The second probe was directly under the orifice plate in the same locations.

My plate was mounted flat (horizontal) as I wanted the baffle plate to evenly condition the air going to the orifices.

Quote:

"Another thing that comes to mind is a horizontal orifice plate mount board vs the 45* angle mounted board. Which way did you go with that choice?"

See above!

Quote:

"Did you experiment at all with it? Were there different results?"

I never tried a 45 degree plate but I have built a couple of benches with vertical orifice plates and had a very long "cylinder tube" that expanded in tube diameter as it neared the floor next to the vertical orifice plate. The end of the tube was 6" of the floor and the floor acted as the baffle. The vertical plate worked well because I had two port holes and could always have the air flow pushing the stoppers deeper into the plate. The horizontal plate deal needed a retainer device unless you really wedged the stoppers in the holes in my testing.

Tom V.

[cboggs]

Larry,

Yes I put three holes across the disc, .. a few inches apart.
The probes are located in the wrong place, .. cause I ran the bench tonight
and they aren't stable at all, .. and really bounce around at 36" test pressure.

I have the probes located about center of the plate on the side to side axis, ..
and about 8" to 10" back towards the rear of the chamber.
I'm going to put some rubber tube on them and try different placement
tomorrow.

Got the divider fixed today, .. ran the 400cfm calibration plate at 36" with
no problems.

I did notice unless I had all the motors on it didn't seem to pull very hard, ..
could this be the non-running motors running backwards?
I'll have to check for cabinet leaks tomorrow too.

Thomas, .. I'll be glad to send you a check for the deck plate idea, ..
what's your address ??

Curtis

[larrycavan]

Tom

I see what you mean now about the way you compared orifices. I don't honestly know if there's a way to prove a comparison. As you pointed out...are you in the sweet spot or is it something about that particular orifice that has the readings differing slightly..

I have 3 calibration plates that I use. One from SF, one from John and one I made. My quick check is using the one I made and I use it every time I start up my bench as a quick check. I hate unbolting my test stand to calibrate every time. To work around that I made a plate and flowed it on a SF on top of a test stand with the 3" bore facing up. I pop that plate on my stand with my 3" reducer cylinder in place and run it up to the same pressure. It's always within 1-2 CFM of what I got on the SF for a reading.

What I've found on my single orifice bench at this point in time is that it's most accurate within a range of pressure.

If I perform calibration using John's plate and my SF plate, both bolted to the top of the bench with no stand, I cannot get both of them to read perfectly. If I calibrate to John's plate the SF is a couple CFM off. If I calibrate to the SF, John's is a couple CFM off. Either way they are certainly within and acceptable range of readings and the bench repeats.

I hope you have the opportunity to test the pass it around plates on Ford's proving equipment. I'm really curious to see what they read. I'm probably still going to wonder though because I won't know if the Cd of those plates was changed between the time I flowed them and the time they get to you. I HOPE nobody starts poking calipers in them and buggers up the Cd....

Larry

[Mouse]

Thomas,

.62 is a standard value, like .075lb/ft^3 is for standard air density. If you do not know the exact Cd of a sharp edge orifice, .62 is a pretty good guess and a good starting point.

When I test a calibration orifice, I usually have to very carefully touch the edge with some 1200 grit paper to achieve the desired Cd of .62.

And the Cd can change. I can't believe the pounding a Pitot tube will take after just a few hours of flow testing. Like it has been sand-blasted. Fortunately, Pitot tubes are not too effected by wear and tear.

John

John

[Mouse]

[Nick]

[larrycavan]

Nick,

My 54CFM plate is 18.4% of my total measurable range flow capacity. The FP1 reads that with no trouble at all. When I flow a head that is flowing 22CFM at .050 lift, @10" that's 7% of full range capacity and it's just a little higher than what I got on an SF110 using the 40CFM range. Were I to flow that using the 84CFM range of the 110, the number would be slightly higher just like it is on my 292 range.

So to answer your question, yes, the FP1 reads the bottom of the scale with what I would consider to be good accuracy.

Larry C

[Mouse]

I have experimented measuring through a 4" orifice with .020" Dp. It calculated the CFM pretty well. Not perfect but not bad. Those test results are somewhere on this forum.