orifice plate leaking

[cboggs]

Hi Gang,

I got my bench running the other day, .. Mercdog plans with the typical
modifications, .. settling chamber / baffle on top, .. etc.

Well the one problem I didn't fix during the construction was the
orifice plate leak during exhaust, .. yes it leaks under the pressure
of 9 motors, ..

I'm trying to do all my tests at 35" or 42", ..

So, .. I was thinking of doing a removable orifice plate deal, ..
like a little "holder" that the plate slides into and locks down.

It'll be a pain to do a full flow test on a head, .. having to stop to change
the orifice, .. but, .. it'll be more accurate.

Has anyone done this??? thoughts, ..

Also, .. I have my pressure pick up tube in the top chamber / settling
chamber, .. .. and my pick ups for the inclined scale above and
below the orifice plate, .. .. is that correct?

Curtis

[Mousehouse1]

Like others before you Curtis you are finding out that the orifice disk either works or it doesn't.

I decided to chunk the orifice disk for an orifice plate setup and haven't finished putting it together yet. I am just about done but not quite. I bought the orifice plates from Bruce. He made them out of aluminum and they measure 6"x6". I had him make me 4 for different flow ranges. I am installing a 8" deck plate in the front of the bench so I can switch them out when needed. It should take less then 30 seconds to switch the plates out. The plates will fit through a 6" beckson deck plate but I decided to use the 8" one instead.

What kind of motors are you using? We have been discussing some of this in the topic called my bench. I installed two o-rings to help seal the bottom of the orifice plate and I am using a spare piece of wood or metal plate to hold them to the bench. I don't know if I am going to use a bolt and wing nut or how I am going to hold the board down. But that shouldn't be to hard to figure out.

Another member suggested making the orifice plates out of metal and using magnets to hold them in place.

[86rocco]

I've decided to junk the rotating orifice plate idea too. I'll do one of two things instead, I'll either have an orifice on a removable plate with some type of clamping fixture to secure it and just swap over to a plate with a different sized orifice to change ranges or I'll have a larger plate with 3 or 4 holes in it an use stoppers in the holes to change ranges. I think I'll try the stoppers first since that easiest to construct, if that proves unsatisfactory, I'll make up the clamping fixture for the plate with individual holes.

[cboggs]

Yea, I think the rotating disc is gonna get used for a Frizbee, ..

I'll need to contact Bruce for some orifice discs, ..
with electronics I'd guess a set like this,
150 cfm @ 28"
300
450
600
750

Now to figure out a way to hold or clamp them into the bench, ..
and to buy a deck plate to get in there, ..

Curtis

[larrycavan]

[cboggs]

Just posted this in the wrong place, sorry, .. but, ..

All this talk of the multi orifice plate with rubber stoppers, ..

and of course I'm having problems with the orifice disc in my Mercdog
style bench, ..

I was thinking of having multi orifice plates made, 6"x6" square and make a
fixture to clamp them in the bench, .. but, ..

could I just take the entire orifice disc out, .. cut a big square hole, ..
make a plate with say 4 holes in it, .. and put it in place????

If the rubber stoppers stay in under 36" of exhaust pressure I'd say
that is a fairly simple / easy way to solve this problem once and for all.
I think Nick posted that his stay in under that pressure, ..

Rocco, .. have you tried it yet???

Still using the "salad" bowl valves that seem to work just fine, ..

I use the Performance trends software so I ordered a box from them, ..
ordered the "high pressure" box so I'll take the Manometers off all together.

I'm using the Amtek motors, 115923 I think, .. I have 9 in my bench, ..
wired in 3 sets of 3, .. with all the motors on it'll suck the entire shop into it!

I'm hoping to pull at least 36" on a DRCE pro stock head flowing 580 cfm @ 28"
and I'd like to be able to pull 42"

Curtis

[cboggs]

Just thought, ..

question, .. about the flow plate with all the orifices, .. what size holes do I need??

If I wanted flow ranges of say, .. , ..

100 cfm
250
450
600
750

And, .. I want to calibrate the bench at 28" and also at 34"

Curtis

[larrycavan]

Depends on the pressure drop you want to use Curtis. What's your manometer designed to handle?

Dwyer #246 with .826 red guage oil...6"...could use the following sizes. [.62Cd is assumed]

1.75" - 101.7 CFM
2.75" - 251.1 CFM
3.70" - 454.6 CFM
4.25" - 599.9 CFM
4.75" - 749.3 CFM

Go with heavier guage oil [1.92] in the same manometer and you could use smaller holes or figure those ranges * 1.5.

Make your own manometer with 12" rise is another way to reduce the sizes.

It's not what you want to test at for pressure that determines the flow ranges. It's the pressure drop across the disk that drives that. The manometer vertical rise [basically] determines that. You can play with fluids to either increase your ranges or decrease your orifice sizes.

FWIW...IMO....the last two holes are quite large. Opting for the larger manometer or heavier fluid would be the better choice....eg. 12" rise - 4" hole = 751.5 CFM.




Larry C

[cboggs]

Larry,

I want to set the thing up with a 28" standard depression, .. 12" rise.
3.75" I think will be my largest orifice plate hole.

but for the orifice plate, .. I think I'm going to remove the manometers all together
and just run the PT Black Box & software.

I'm assuming I'll have to set up the manometers and calibrate this thing first, ..
then use the PT software???

Can I just use my 36" vertical manometer to check pressure drop across the
orifice disc? or do I need both manometers, .. ??

I've got two calibration orifices coming from bruce, .. but
I'm not sure I understand the calibration method and just what I'm supposed to be doing.

Curtis

[cboggs]

Got another question too, ..

if I remove the orifice disc and replace it with a single flat plate with
say 5 holes using the rubber stoppers, ..
where do the pressure pick ups need to be placed?

Being that there are 5 holes, .. can't really get them close like you can
with a rotating orifice disc, .. so if they aren't that close, .. will it effect
the accuracy?

Curtis

[Thomas Vaught]

Curtis,

The PT software is good as is the FP#1 stuff.

You can keep your vertical manometer if you want. Test pressure is test pressure.

The SF 1200 bench only uses 3 holes 200 cfm 400 cfm and 600 cfm.

I added a 100 cfm hole to the one I use on occasion.

100 cfm = 1.75 inch hole .61 cd

200 cfm = 2.50 inch hole .60 cd

400 cfm = 3.53 inch hole .60 cd

600 cfm = 4.37 inch hole .587 cd


The cd goes down typically on the larger holes in the SF1200 bench. I use an average of .587 for cd and it works out well. You can now have 100 cfm changes in the ranges from 100 cfm to 1300 cfm if you had the motors to pull the number. SF uses 16 motors 115923 to get actual 1147 cfm.



Tom V.

[cboggs]

Now this may be a stupid question, .. but, ..

Say I use 4 ranges / holes, .. 100, 200, 400, 600 as an example.
Does using tow or more of the holes together effect the accuracy of the holes, ..
and does the calibration change?

Should I calibrate for each range or if I do each hole separately can I just then
use the holes together and add their flow value???

How should the holes be laid out on the plate, .. all in a row like a SF-110?

thanks,

Curtis

[Thomas Vaught]

I have verified many times that if the holes are some distance apart the flow numbers are pretty much close to being additive.

The plate in a sf1200 is 24"x24"

Make a "X" in the plate then locate the holes so
that you have the largest hole 600 cfm in the top left of the "X", the smallest hole 100 cfm in the top right of the "X", the 200 cfm hole in the bottom left of the "X", and the 400 cfm hole in the bottom right of the "X"

I just divided the distance between the center of the "X" and any one leg and put the center of the given hole there.

Tom V.

[larrycavan]

Tom,

You calculations are based on a 6" drop.

With digital manometers you are not as limited as you are with water guages, they handle much higher drops. The FP1 will handle 40". I'll just leave it at this.

What you have available to you as "measurable flow" with a water guage is lower than the potential " measurable flow you have available to you with a digital guage that handles much higher pressure drops. As such, your " measurable flow potential across any size orifice, is increased by a significant factor.

Where that comes into play is when you're determining what size orifices you need to accomplish the task at hand...

Larry C

[larrycavan]