PTS Flowbench Forum

A pic with description of bench.
http://s1364.photobucket.com/user/rvaug ... f.png.html
I have read but am not quit understanding the incline mano. And/or if I am looking at it correctly.
I made a copy and enlarged it to fit the 28" length. http://s1364.photobucket.com/user/rvaug ... sort=3&o=0
This is where I am kinda getting lost. With the 150cfm @ 16" wc plate internally and testing with the 100cfm on top my inclined read 83 on the scale. . If I made that scale only 12" long and had the same 30ish degree angle... I would have pulled all the liquid into the syringe.
I have read where the incline has to match the vertical if the incline was "tee'd" to do the test.
Tony mentioned here: http://www.flowbenchtech.com/forum/view ... 1&start=20
But the measurement used was based on a percentage of the mano. ex:

100%...... 1.00 x 1.00 x 900mm =900mm
99%.........0.99 x 0.99 x 900mm = 882mm
98%.........0.98 x 0.98 x 900mm = 864.4mm
97%.........0.97 x 0.97 x 900mm = 846.8mm

Not seeing how the above references to a mano.
How do I go about checking the incline to the mano? I know I can tee the two together, but the 0-100%... is that based on 0-16wc?
If the 0-100%/0-16wc is true then would I need to have another scale going to 0-28wc?

Thanks.

On your drawing you are showing the rise of your water gauge as 12", so the internal plate CFM is now based on 12" of differential pressure and not 16".

If you work with 16" across the plate then your rise of your water gauge should be 16".

So with your setup now your internal plate based on a 12" differential pressure and is now only capable of flowing 130cfm @12"

Your 100@28" plate would now read 83% on the 130@12" plate when you run your flowbench up to 28"

If you haven't already done so, download the spreadsheet found in THIS THREAD, it'll take care of most of the nasty math for you. Now, to do precise calculations with your inclined manometer, the information needed is the inside diameter of the inclined tube, the inside diameter of the manometer reservoir, the vertical rise between 0% and 100% on the inclined manometer. With that information, you can calculate how much pressure is required to make your inclined manometer read 100%.

Now, you don't provide quite enough information in you post actually do the calculations on your inclined manometer but just to move things along, let's say you've done them and you've come up with 12.0" at 100%. The inclined manometer measures the pressure difference across the internal plate and since your internal plate is rated at 16", we need to calculate what it would flow at 12.0", to do that take the square root of 12.0/16 and multiply that result by 150cfm and you come up with 129.9cfm that would be the 100% value of your inclined manometer when the flowbench has the 150cfm@16" plate installed so the 83% you measured would translate to 129.9 * 0.83 = 107.8 cfm

A couple of corrections...
The orifice is 132cfm@28"/100cfm@16".

If you work with 16" across the plate then your rise of your water gauge should be 16".

So, I will place my incline back to a 16" rise and use the 16" cfm #'s to measure against.
Lets see if I get this so far... if the total length of the incline (from 0-100) is 16" then 16" rise on the mano is the most I can test and the "incline" would actually be straight vertical because it is 16" tall. Then, you would want to increase the length of the incline mano to say 21" (or so) to "incline" it on a 30 degree rise?

If you haven't already done so, download the spreadsheet found in THIS THREAD,

I had. I measured my incline mano to the percentages and came out exact.

I think I am there. My biggest issue was understanding that the incline is just another manometer but the rise (0-100 scale) has to be set up to the same wc you will be testing at. Assuming my analysis above is correct... you can't test 28" wc with a scale less than 28" (0-100) and the whole point of "leaning" this particular manometer is to allow the graduations to be read easier.
* To any future reader... keep in mind that by using the sheet/hyperlink 86rocco mentioned earlier; you have to account for the minor issues of the tubing id, reservoir id, etc.

The rise of your incline is your differential pressure ie 16", this could be any rise though if someone machines their own plates. I machine my plates to 16" so they work with my digital manometer or is easy for someone to convert over at a later time. A smaller rise and your readings get bouncy to large a rise and you need to much motor power.

The length sets your percent, the longer it is, the finer (wider) your divisions will be so you can see minor changes easier. You could make your length 2', 3' 4' etc again using Ed's spreadsheet helps do all the math.

28" is your test depression and it could be any number you want to test at, 28" is a "standard" this would be set using a vertical U tube or well manometer.

Now to calibrate your flowbench you can change the rise of your incline manometer so it follows along with your calibration plates, so it could be your rise is higher or lower than 16" based on your calibration plates. This is one thing you have with making your own water gauges as opposed to buying set rise gauges.

Make your inclined manometer with the ability to change the rise of your scale for calibration.

Whew hope this all makes sense . . .

rvaughnp wrote: I think I am there. My biggest issue was understanding that the incline is just another manometer but the rise (0-100 scale) has to be set up to the same wc you will be testing at. Assuming my analysis above is correct... you can't test 28" wc with a scale less than 28" (0-100)

That's not quite correct. Don't forget, you have two manometers, what it often referred as the test pressure or depression (commonly 28" wc) measures the pressure difference across the cylinder head or whatever it is you're testing and it's usually measured using a vertical manometer. The second manometer usually inclined measures the pressure difference across a calibrated orifice, this is usually referred to as the differential pressure. Let's say you've got an orifice that's calibrated at 150cfm@16" and the port you're test flows 100cfm@28", when you're testing, you increase the flow through your bench until the vertical manometer reads 28" and then read the inclined manometer, the differential pressure it reads would be 7.1" (BTW 7.1= 16 x (100/150)²) where 7.1" lies on your inclined percentage scale depends only on the angle you have in your incline. So as you can see the inclined manometer can have a maximum differential pressure range MUCH smaller than your test pressure provided you size your calibrated orifice accordingly.

rvaughnp wrote: and the whole point of "leaning" this particular manometer is to allow the graduations to be read easier.

That part you got right.

The actual length of the manometer tube and scale does not matter, as I think you already realize.
It is how far the high end is raised above the low end that matters.

However, when it comes to marking out an actual scale, it will be much easier if you use a metric steel ruler than an inch steel ruler to mark off the divisions.
Much easier to mark off 68.4% on a 1,000mm scale length than trying to mark off 68.4% on a 20, 30, or 40 inch long scale.

I tested a head and got these results... would you mind looking and seeing if it looks accurate?
The plate is 240cfm @ 16”wc
I ran the mano up to 16" wc and then read the incline @ 55%
.55 x 240 = 132cfm @ 16”wc
28/16 = 1.75 x 132cfm = 231cfm @ 28”wc

It is how far the high end is raised above the low end that matters.

I have the rise set at 16" and plan to keep it there and just use the orifice #'s based on the 16" wc. As well I plan to just use 16" wc height on the "U" mono and then convert to 28".

However, when it comes to marking out an actual scale, it will be much easier if you use a metric steel ruler than an inch steel ruler to mark off the divisions.
Much easier to mark off 68.4% on a 1,000mm scale length than trying to mark off 68.4% on a 20, 30, or 40 inch long scale.

Already made. I used a piece of 1" angle aluminum.

Let's say you've got an orifice that's calibrated at 150cfm@16" and the port you're test flows 100cfm@28", when you're testing, you increase the flow through your bench until the vertical manometer reads 28" and then read the inclined manometer, the differential pressure it reads would be 7.1" (BTW 7.1= 16 x (100/150)²) where 7.1" lies on your inclined percentage scale depends only on the angle you have in your incline. So as you can see the inclined manometer can have a maximum differential pressure range MUCH smaller than your test pressure provided you size your calibrated orifice accordingly.

Still working on that.

The length sets your percent, the longer it is, the finer (wider) your divisions will be so you can see minor changes easier. You could make your length 2', 3' 4' etc again using Ed's spreadsheet helps do all the math.

Got that. Thanks.

28" is your test depression and it could be any number you want to test at, 28" is a "standard" this would be set using a vertical U tube or well manometer.

Now to calibrate your flowbench you can change the rise of your incline manometer so it follows along with your calibration plates, so it could be your rise is higher or lower than 16" based on your calibration plates. This is one thing you have with making your own water gauges as opposed to buying set rise gauges

Still working on that.

rvaughnp wrote:I tested a head and got these results... would you mind looking and seeing if it looks accurate?
The plate is 240cfm @ 16”wc
I ran the mano up to 16" wc and then read the incline @ 55%
.55 x 240 = 132cfm @ 16”wc
28/16 = 1.75 x 132cfm = 231cfm @ 28”wc

What plate is inside your flowbench? 240@16"?

What plate is being tested on top of your flowbench?

Can you not test at 28" If not what is the max pressure you can test at?

Personally, I do not like to work in conversions while trying to get a flowbench calibrated. I want to know everything is reading correctly before introducing something that could add or subtract accuracy. Hey that's just me and others have had success doing the "math" for conversions.

rvaughnp wrote:I tested a head and got these results... would you mind looking and seeing if it looks accurate?
The plate is 240cfm @ 16”wc
I ran the mano up to 16" wc and then read the incline @ 55%
.55 x 240 = 132cfm @ 16”wc
28/16 = 1.75 x 132cfm = 231cfm @ 28”wc

The math is wrong, flow is not linear with respect to pressure difference, it's a squared relationship i.e if you double the flow, the pressure difference goes up by a factor of 4 or working it in the opposite direction if you double pressure difference, the flow will increase by a factor of √2 = 1.414 so the correct calculation is:
√(28/16) X 132 = 1.3229 X 132 = 174.6 cfm

rvaughnp wrote:I have the rise set at 16" and plan to keep it there and just use the orifice #'s based on the 16" wc. As well I plan to just use 16" wc height on the "U" mono and then convert to 28".

You've got to shake the idea that your test pressure is limited by the inclined manometer, that's NOT the case You can run the test pressure up as high as you like as long as the flow through your test piece doesn't exceed the rating of your calibrated orifice at 100%. Your test here is a good example of that, rather than test at 16" and calculate the flow at 28", it would have been simpler (and probably more accurate) to just run the vertical manometer up to 28" then your inclined manometer would have read 72.8% .728 X240 = 174.7 cfm.