orifice plate leaking

[Terry_Zakis]

Sorry Thomas,

I didn't realize that the 2" orifice was refferenced to a single motor.

The file has a lot of information in it, and even for myself, it takes a little time to get reacquainted.

Best Regards,

Terry T.

[Nick]

If you use a lower delta P then you will have more vacuum available for the test pressure. There is another way around this to, you can do your tests lower in the incline scale, but if your bench is not accurate down there that might not be so good.

I would use 6" Delta P. I would use the Roccos spread sheet in the spread sheet section to figure out your orifice sizes.

For instance, 6" delta P = CD .62 = 299.9 cfm = 3.005" orifice If you can machine it to half a thousandth, more power to ya.

Also I have found in my bench the CD is closer to 5.9. I don't know why, but others have posted similar numbers, perhaps because it is in a box instead of being open air.

Hope this helps

Nick

[Thomas Vaught]

Agree with the cd. I personally see an average of .587 on a lot of the SF benches for the holes.

Tom V.

[cboggs]

Well,

first guys I want to thank you very much for the help, support, discussion
in getting this going, .. you are a great bunch !!!

OK, .. had a long talk with Kevin at Performance trends, he made some
very good points.

First with the flow losses etc in the bench he doesn't think I'll hit 40" at 600 cfm.
He made the point that the SF-600 used 8 of the same motors and only
pulls 600 cfm @ 25", .. but using the DP of 13.8"
I have 9 motors ( I knew I should've stuck 12 in there )

So he suggested using a DP of 8" across the orifices, .. I can still use the
Dewyer inclined with the red fluid and extend the scale by 2"
8" dp should give enough accuracy as long as I'm above 20% flow.
He thought 6" dp wouldn't give proper accuracy unless the flow range was
above 50%.

Use three orifices, .. 1.6" for 98 cfm, 2.3 for 202.9 cfm and 3.25" for 405.1 cfm.

That will give me 7 ranges from 98 cfm up to 700 cfm.

He thinks I'll end up pulling around 36" @ 600 cfm max, .. considering flow
losses in the bench. I can live with that.

So, that's the plan for now, .. .. you guys thoughts ?????

Curtis

[Thomas Vaught]

Quote:

"So he suggested using a DP of 8" across the orifices, .. I can still use the
Dewyer inclined with the red fluid and extend the scale by 2"
8" dp should give enough accuracy as long as I'm above 20% flow.
He thought 6" dp wouldn't give proper accuracy unless the flow range was
above 50%."

How did he propose you change a durablock 246
designed for a 6" delta P and make it a 8" delta P without changing the fluid?

Tom V.

[86rocco]

Using Tony's formulae from , you need the blowers to provide about 3800 total air watts at 13.6" DP (i.e. total pressure of 13.8+40=53.8").
Now if we look through the blower specs from , we see that at 53.5" those motors each provide 447 air watts for a total of 4023 so depending on how much efficiency is lost running 9 motors in parallel, you should be at least close to the goal of 600 cfm @ 40". And, as you decrease the DP, the numbers look better yet, at 8"dp you require about 3400 air watts, at 6" about 3250.

[larrycavan]

[cboggs]

Hummmm, ..

I have NO idea how to change the durablock 246 to 8", .. and I didn't ask, ..
He did say that electronics aren't always perfect and thought it's a good idea
to keep a Manometer back up.

What does the Violet gauge oil, . . 1.00sp. gr. change the 246 range to?
It's the same as water right??? Why can't I just use water with food coloring?

Does Dwyer make water range scales for the 246 for use with the
different gauge oils?

So the statement about the accuracy of using a DP of 6", .. is this true??
If I use 6" instead of 8" or 13.8" will the accuracy of each hole suffer?
I assume that's why there's 6 orifices in a SF-600.

It seems to me that there's a trade off, .. at 6" it takes a larger orifice then
at 13.8", .. so at the lower dp's the accuracy must really suffer.
So with a 6" dp you should never flow below 50% of the range?

I also agree with the SF-600 comparison for motor power, .. if it only
pulls 24" with 8, how is it that I can expect to pull 36" with just one more motor?
I'm beginning to fear I may only get 28" @ 600, ..

I'm going to make an orifice plate tomorrow and try to get it installed and
running over the week end to see what happens.

Curtis

[Peter]

The following is from one of the Dwyer engineers;

The difference in the red gauge oil and the blue oil is a factor of approximately 2.31. Therefore, a 6" w.c. scale will result in a 13.87" scale. You will not have to change the 0-100% since percert is virtually unitless, you just have to change the meaning of the 100% to 13.87 from 6. You will not need much blue gauge oil, two of the 3/4 oz dispenser bottle (model # A-110) should be enough. If I can be of further service, please let me know.

Hope this helps.

[Thomas Vaught]

Thank you Peter.

The Super Flow 600 already used the Blue fluid and according to some will only flow 600 cfm
at 25 inches of test pressure across the test part. I agree the orifice delta P is 13.87" h2o.

The man's question was he could get a manometer that would have a 8" delta P across the orifice at 100 percent on the normal 20" long Durablock 246 scale.

Thanks

Tom V.

[Peter]

You can't get 8" on a 246, the only two scales available are 0-6" and 0-100%, which I have on mine.

[cboggs]

I'm going to put three orifices in it based on a 6" dp just to
get it running and see what it does, .. I'm shooting for it running by Sunday.

1.75" -- 100 cfm
2.50" -- 200 cfm
3.53" -- 400 cfm

Curtis

[Thomas Vaught]

Will look forward to the results.

Tom V.

[gofaster]

Peter,
Dwyer will also sell you the square root scale, 0% to 100 %, which is what I bought. It is a special order and they nick you for more money, and it also took me a lot of telephone and e-mail conversations to get it right. Had to send one back, etc.....

If persuasion and perseverance don't work, try stubbornness.

[Rick360]

Curtis,
If you use water or a fluid of 1.000 S.G. in the same manometer that was 6" with .826 S.G. fluid the new range would be 7.264"wc.

BTW, I have an 8"wc range on my bench with a home built manometer (26" long scale) using .826 red fluid. I think the manometer scale length is the most important thing for accuracy. When you are below 50% on any square root (flow %) scale, the problem is the resolution of the manometer, not that the orifice doesn't present a consistent airflow restriciton at that D.P.

Doesn't a SF300 use 6"? Is it less accurate than a SF600?

Rick