Orifice hole sizes the all common ?

[JRM]

I was reading through all the posts and thinking about all the orifice hole size questions i see. The spread sheets that have been posted im sure really help alot of people Kudos to the ones who made them.
But I was thinking maby we should team up and make a list of common hole sizes and the cfm they flow at a common pressure drop. Have it all listed as a sticky on the entrance of the form.
I know for me unless I have it saved to my computer I'll loose it everytime :laugh:

Now where did I leave my mind

[larrycavan]

I think that's a great idea. A standard would be needed for the thickness of the disk. Thick enough so it doesnt' flex and thin enough so we dont' run into a lot of cf variances. What do you think?

Best Regards,
Larry

[JRM]

I agree. I guess the next question should be what is a good std thickness of metal or alum to use. I know 12ga and 16ga sheetmetal is quite common around here at lows and home depot.
I need to go through my old files beccause i think the MSD bench used 16ga for their flow disk

[larrycavan]

They say 22 guage steel in the cost breakdown sheet. I can't remember what mine is. I have a friend that works for Macintosh Stero that made mine in their model shop. They were able to punch all the holes in the steel.

I"m seriously considering building an entirely new bench based on the design of the SF110.

Larry

[bruce]

.125 thick, sharp edge, 45* back angle, machined to .001" in diameter will give a .62 Cd. You could not list a set of common hole sizes to use since they are all going to be machined by seperate people, it would only be a reference list to get you close. A change of .007" in dia on a 1" orifice will give you a difference of 1 cfm and 2.1 cfm on a 2" orifice at 28" of depression. You can not hold the level of accuracy you are seeking (from my observation of the manometer % thread in the past few days) with punched or drilled holes in thin material.

[Thomas Vaught]

I had .125 steel 24" X 24" cut on a laser with 5 holes in a "dice"
(Number 5) pattern. The holes were arranged to have the maximum distance between the walls and each other. All of the holes were with-in .001" of My requested size after the process.

The holes did not have a 45 degree under cut as I was thinking
about flowing in both directions during that part of the design/
construction phase. Also a lot of people were copying the MSD type bench and wanted flow in both directions.

When I build a new bench it will use 4 holes (vs 5 now) and will
be one direction only but I will use two measurement plates (Like
Tony did with his Blower Centered bench). The Super Flow 600 is actually a form of a blower centered bench .

Example:

Exhaust flow: Air comes from outside the case, thru the motors,
past the orifice plate, and up to the test piece.

Intake flow: Air comes from the test piece, thru the orifice plate,
thru the motors, and then outdside the case.

If you made a bench so that when you read exhaust flow you by-pass the intake orifice plate, you would have the same thing.

Same for the intake flow. (By-pass the exhaust plate).

Food for thought.

I will post some numbers for the SF orifices I have measured over
the years the flow, and the delta P.

Tom V.

[84-1074663779]

I definitely agree. Reversing the flow through the whole bench is a bad idea, it is complicated, and can create all sorts of extra problems.

I have two identical test holes on my bench top, one sucks and the other blows. No need to reverse anything. There are three vertical manometers, one for flow, and two permanently hooked up for positive and negative test pressures.

The only controls I have are a car steering wheel to rotate the (rather large) orifice turret, and a ten turn potentiometer on the variable speed drive to my blower. Very simple to build and very easy to use.

[Thomas Vaught]

I have posted orifice flow numbers, discharge co-efficients and hole sizes for the sf 300 and the sf 600 benches in the 246 durablock post..

Tom V.

[JRM]

what i was more thinking of was if you use a given thickness of sheet metal.
A hole that is
.500 flows xxx cfm @28
.750 flows xxx cfm
etc

Just to give a general guide line to help when setting up the ora. plate. Either way you will still need a calibration plate to correct your cfm once you are finished. Correct me if I an wrong. Arent you suspose to recheck the calibration before use anyway, So if you are off by a fiew cfm after the calibration plate has been used you can mathmatically correct for the flow error.
If I understand what other people have been asking Including myself. Is where to get an accurate calibration plate or plates so the variable can be compinsated for.

ps sorry if I am sounding brash im sick as a dog with the flu