PTS Flowbench Forum

Hey. I have built a flow bench and could use some help.. The pic will not load so I will describe what I have done so far... Inside the box there is a plate that I made probably not accurate but here is how I made it. Drilled a hole with a hole saw, honed out the inside of the hole so that its all one level, Then took a sanding block to both sides to true up the edges. It measures 1.779 with the calipers. The spread sheets says it should flow 137.7 at 10" WC. I used 4 vacuum cleaner motors mounted on a box and have 4” PVC running to another box that is roughly 24x24 with a divider in the middle. 5” hole in the top and 5” hole in the divider where the plate goes. U-tube mano is in upper plenum, incline on one side is the upper and one is in the lower. The 5” hole in the divider is near the left wall. The manometers pickups are in the corners...My question is.. When I turn on all 4 motors, it pulls all the water out of the incline. Does that mean that there is to much vacuum below the plate? There is a 5" hole in top of the bench but it pulls out the water with the head as the test piece. I don't have the full grasp of the math yet, but am working on it. I hope to get the pts plans sometime. If anyone can help I can send pics Via e-mail.

Send me the pics I'll get them posted on the forum, I happen to know someone who can do that

Did you verify your incline manometer is reading correctly compared to your vertical?

Also check each pickup point with your vertical manometer to verify they are working correctly. This can be done using one side of the inclined manometer and "T"ing it in line with the vertical and running your bench up and comparing numbers.

The way I read your post it seems to me one of the pickups is not working right?

Worked on the bench some tonight. I do not have any tee's so I took the one side of the incline loose from the bottom plenum plugged the hole, turned on the bench, the u-tube pulled up to 3 3/4" . The incline pulled down to 10 1/2. Then I switched the pickups and they were not the same, so tomorrow I will move the u-tube over near the incline pickup and see if I can get the same numbers. All this was done with a 1.779 plate on top, no plate inside. Am I headed down the right road? I can also see that more motors will be needed.

First you need to make sure your gauges are working correctly don't worry about plates right now. You can use your plate to create the depression.

What is the vertical rise of your incline?

All you are concerned with right now is making sure the water gauges match in static testing. Compare the vertical rise reading to the same reading on your vertical, if your rise is 10" then you should show 5" rise on your U-tube. Do this test on each pressure pickup point. You can set the bench to a given static and just swap the manometer connections if you do not have a t-fitting no need to shut down the flowbench just swap tubing.

Once you know your gauges are working correctly then you can move on to the next step of figuring out what's not readings right

Let me also add it helps to work in the same pressures so always do your testing at a given static and compare those numbers, it helps us to trouble shoot your flowbench also as we have no clue what your gauges are designed to read.

OK so here is what was done today. Moved the incline over beside the incline pickup is. Only used two motors they pulled 5" according to the 72" Swanson ruler, this is measured on the right side of the u-tube, it's hooked to the bench. The left side is open. Then on the incline it pulled up to 20" measured with a 36" ruler . It took some doing but I did get it to repeat the same numbers on the incline.

On the incline I tried to do a % scale based on 20" but think it was a failure, so in went the yardstick
Going too get some more wood this weekend and redo the incline . What would be the best length for the incline?


Thanks

Brucepts wrote: What is the vertical rise of your incline?

I'll ask this again as I do not think you are following along with what I am trying to get you to do to verify your gauges are working correctly. You need to first verify your incline follows along with your vertical manometer to make sure your pickups are working.

Have you hooked your vertical manometer to each pressure pickup separably and checked the readings? Once you know they are working then compare the rise of your incline to your vertical rise on the same pickup point not the length of the rise across the scale which you are saying is 20".

Maybe I am not explaining this as well as I could?

Ok, so all pickups should read the same on the vertical ?
And the same for the incline is this right?
say 5" on vertical should be 5" rise on incline

The vertical rises should match each other but on the vertical U-tube it will be total rise and fall of the legs so a 5" rise on the u-tube would be 10" total as you also have a 5" fall on one leg.

So to check say a 8" rise incline you would see 4" rise plus 4" fall for a total of 8" on the u-tube. Keep in mind one leg of your incline will be open to atmosphere for this test as you are simply comparing manometers.

Your incline rise can be any length you want to to work with, the longer it is the closer your scale divisions become.

Once you know they are all working correctly then you move onto working with differential pressure across the plate.

Use the spreadsheet in this post for developing your scales http://www.flowbenchtech.com/forum/view ... ?f=14&t=73

See if i am understanding

-
^ -
rise 10" -
___________________v________-____u-tube 5"
if all the pickups read the same on the u-tube (the above is what i should have) would that be correct?

sorry if I seem hardheaded I am flow bench handicapped