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Posted:
Tue Feb 05, 2008 4:44 pmby Erik
So now it time to build a new bench this is an adiction.
Qestion????
Planing to use ruber plugs to determin ranges inside the bench on a fixed orifice pate that is flowing both directions. If I put in the pugs from one side will they stay in place when i revers the bench?? or do I nead to move the plug to the oter side?? when the test presure is ower 28"H2O. Have anyone thryed this??
I am using FP1 so I was thinking of using three ranges on the orifice plate 150cfm, 300cfm, 600cfm is this a good idea
nead opinions
Posted:
Tue Feb 05, 2008 5:54 pmby 86rocco1
There are quite a number of benchs out there using that technique so yes it can be made to work.
If you're worried about the particular setup you have in mind, why not make a mock up and test it. Make a sample of your largest orifice, put a rubber stopper with an eyelet screwed into the center of it, hold it upside down and see how much weight you can hang off of the eyelet before the stopper pulls out. And remember, the stoppers will not usually see the full 28" pressure difference, the most they would normally have to hold back is whatever pressure is at 100% on your inclined manometer.
Posted:
Tue Feb 05, 2008 8:52 pmby thomasvaught-1
Say for example you have a conventional looking orifice bench with the orifice plate located about 1/2 way up the height of the bench. If you install TWO port holes, one in the upper chamber and one in the lower chamber of the bench, when you are doing intake testing you can install the stoppers from the top side. When you are doing exhaust testing the stoppers will remain in place if the stoppers are installed from the bottom side through the lower port hole and wedged in place. Exhaust pressure will seat them firmly.
Another method is to put a thick metal ring on the top side of the stopper and even when doing exhaust testing the weight will keep the stopper seated in the orifice hole.
A third way to correct the issue is to mount the orifice plate sideways like Tony did his bench and use two port holes. Move the stoppers from side to side like in the forst example.
I have done them all with equal results.
Tom V.
Posted:
Wed Feb 06, 2008 3:35 amby Erik
[color=#000000]Thank
Posted:
Wed Feb 06, 2008 10:57 amby SWR
Erik, I'm using ventilation pieces from Lindab Sweden for my port holes.. in the larger sizes the tube end caps I'm using even have a bayonet locking tab either side of the cap,so you just twist it,then pull it straight off in 1 second. And the Lindab inlet parts that bolt to the bench have dual neoprene gaskets,so no sealing issues.. 
Not that I found yet,at least.
Posted:
Wed Feb 06, 2008 11:12 pmby thomasvaught-1
Some of our european friends have posted about the Beckson Port Holes in the past.
Tom V.
Posted:
Thu Feb 07, 2008 12:08 amby larrycavan
Posted:
Thu Feb 07, 2008 12:51 pmby 86rocco1
Posted:
Thu Feb 07, 2008 3:05 pmby larrycavan
Posted:
Thu Feb 07, 2008 4:04 pmby Erik
I dont think that there will be aproblem with the orifices.
I planing to use 2mm stainless for the orifice plate with square edge.
soner or later the orifice probobly will be worn out, but I think it will be after my retierment 
I think steel is harder than rubber
:p
Normaly I check the calibration prety often.
Posted:
Thu Feb 07, 2008 4:30 pmby bruce
Its not that the orifice plate will get worn out it's the fact it will lose it's sharp edge which will change the Cd over time. Be aware also, that to thin a plate could possibly vibrate.
Posted:
Thu Feb 07, 2008 5:12 pmby larrycavan
Posted:
Thu Feb 07, 2008 6:36 pmby Erik
[color=#000000]Thank
Posted:
Thu Feb 07, 2008 9:14 pmby thomasvaught-1
I would not worry so much about potentially damaging the sharp edge of the orifice plate vs doing routine calibration checks to determine what the flow range was for a given day.
If you look at 86Rocco's spreadsheet for the orifice calculation you will see that even if you set the discharge co-efficient at a perfect .62 cd
and you think you have a perfect .62 cd created orifice plate, the flow number in the program is based on an assumed lbs/cubic foot number like .076 lbs/cubic foot.
Depending on where you are in the world, unless you are at seal level on the perfect Standard Temperature and Pressure day, the flow number calculated will be slightly different vs what you assumed in your initial calculations when you designed the orifices.
Using Bruce's calibration orifice before testing each day will tell you the offset for that day whether the Delta P orifice has a perfect sharp edge or a slightly worn edge, in my opinion.
Tom V.
Posted:
Fri Feb 08, 2008 3:21 pmby Erik
This is my opinion also
When I used my old bench and the SF110 I always started the test sesion with check the calibration.
when using yhe FP1 the Cd only is a walue to calibrate the bench it dont seams like Cd walue affects the qality fo the flowtest as long as the calibation is ok to a good calibration plate.
Erik