Initial Test Results

[Thomas Vaught]

Dom, please explain what the hoses go to on the well and where the well is vs the inclined manometer.

Thanks

Tom V.

[larrycavan]

Dom

The one thing that comes to my mind is the side door on the cabinet on the intake side.

If that had a major leak, I don't believe it would show up in a cabinet leakage test but it would drastically kill the motors ability to pull air across the orifice disk. The larger the orifice, the greater the effect on it. That could account for the small orifice being in the ball park but all the larger ones not anywhere near where they should be.....

Larry

[Dom G]

Tom

The inclined manometer is directly on the other side of the panel. The reservoir is slightly more than half full so that I have maximum surface area within the tube. The tubing that comes out of the fitting on the left of the picture loops around the side of the panel and connects to the bottom of the inclined manometer. The tube which connects to the fitting coming out of the top of the reservoir connects to the pressure probe that goes to the upper air plenum. And the tube coming from the upper end of the inclined manometer attaches to the pressure probe that goes in the lower air plenum.

Dom

[bruce]

The surface area of the liquid in your reservoir is changing, you do not have a constant area.

Your pipe should be upright so the fliud has the same surface area, laying on its side the walls are curved which changes this area. As small a change as it is, it might just be some of the problem?

Just my thoughts

[larrycavan]

You might have to download this pic and enlarge it to read my notes....I can't tell till I upload it...

FWIW....I would get those metal boxes bonded together and run it over to the ground strap in the breaker box. Also...by whatever means you can swing..it's a good idea to get some sort of bond on every motor and get it run to the ground tab in the box as well....you just cant' be too careful or have too many grounds....

Larry

[Dom G]

Larry

My description of the connections to Tom a couple of posts ago is the way I have the lines for intake testing. Right now, the picture shows the connections for exhaust testing.

You indicated with your blue arrow that the other end of that line should connect to the lower plenum probe. It doesn't, it goes to the bottom ( 0 end) of the inclined manometer.

The line that your red arrow is pointing to does connect to the probe for the upper plenum.

Where your green arrow is pointing is the line to the upper end of the inclined manometer.

I pick up my test pressure with a line that goes to the center of the head adapter rather than teeing into the upper air plenum.

Just to clarify, the probe to the left bottom of the switch boxes is to the upper plenum and the probe to the bottom right of it goes to the lower plenum.

Additionally, the hole where the wires go through the cabinet is caulked from inside the cabinet.

I thought all of my connections were correct, but maybe not. I'll wait until I hear back.

Dom

[Nick]

Bruce

I think well is fine the way it is mounted. The drop of liquid in a well that size is very small and would not affect the readings enough to matter. It looks like mine that is 1000 times the surface area of the tubing, so a 12" rise would only be about a .012" drop in the well, not enough to matter.

[larrycavan]

Dom,

Yea..I couldn't tell which way you had your machine set for testing....If the fluid is moving the right way in the scale, then you should be fine. As long as each end of the inclined goes to the plenum probes it's cool....If it was hooked up backwards the fluid would go the wrong way and you'd spot that instantly..

Using a T in the top plenum to pick up test pressure and chamber pressure should work. They are one in the same. I've seen that done before and the user reported good results.

I've been thinking about your situation all day and waiting to see what your exhaust tests revealed. There's something being overlooked..I just can't put my finger on it. Like I said in my last post. If you can't find any leak between the plenums then the thing I'd be looking at is the door on the side of the cabinet that you close for intake testing. It's the only other thing I can think of that would cause such low readings. If it were open, you'd be pulling air through the top and straight through the side of the cabinet..mostly through the side...that would rather add up to the results you're getting...The door on the intake side of the motors absolutel must be sealed tightly during intake tests or your motors will not pull strongly across the flowdisk....

Let me know what you find out.....I'm probably as curious as you are at this point...

Larry C

[Dom G]

Although my frustration level is rising, I continue to test and retest various components of the bench in hopes of finding the problem.

Since the problem affects both intake and exhaust testing I decided perhaps I have a problem with my plenum air control valves not really sealing fully. So I removed the exhaust valve (walmart stainless steel bowl) and replaced it with a 12 ply piece of 3/4" birch plywood and bolted it tighly against the silicon seal. I reran both the intake cabinet leakage test and flowed the calibration plate with the same two orifices that I have been using.

The leakage test still came in at .5 cfm if you can believe it. Running the calibration plate and the the 2.009" orifice yielded a slightly higher cfm. The plate is calibrated for 160 cfm. When I first ran it upon receiving the plate from Bruce it measured 155 cfm. When I ran it today after substituting the plywood piece it measured 160 cfm. However, when I moved up to the next larger orifice (2.531") and ran it the results were still extremely low (about 15%) as before.

I'm trying to isolate various components and test them in hopes of discovering the problem so I can avoid taking the bench completely apart. One thing I am thinking about doing, though I don't know at this point how to do it or if it will work, is to apply vacuum to the three individual compartments of the bench that involve intake testing. i.e. upper plenum, lower plenum, and lower left chamber that the motors draw air from. I'm wondering if I was able to seal off each cabinet component and apply vacuum to it, whether a temporary probe inserted in the component and connected to the vertical manometer would give me a reading or tell me anything?

Tomorrow I plan to retest with the side door on the intake side sealed with caulk instead of the weather seal I have been using.

The one thing that troubles me the most is that all intake tests with the calibration plate and the 2.009" orifice consistently yield the same accurate results, but the results with larger orifices aren't anywhere close. Can it be just luck?

When trying to look at this simplistically, it seems whatever forces or dynamics that are present and causing problems with the larger orifices must be there when testing with the next smaller one.

If anyone has any other ideas or thoughts I'd appreciate hearing them because I'm running out of them.

Thanks.

Dom

[larrycavan]

Dom,

Wow..that thing isn't playing fair at all...

Let's approach this from another perspective.

You're 2" range is pretty close. How many motors are required to pull 28" using your 160CFM test plate with the 2" orifice?

Now let's see if we can rule out anything with this test.

Select your 2.5" orifice and seal off the rest with duct tape.
Also, take something that you can tape across the 2.5" orifice to reduce it's size by about half. A thin piece of metal...anything...just reduce the size of that orifice. See if you can pull any CFM then.

Don't change anything else just yet....try that test first.

Not one thing about this adds up.
Leaking side doors won't show up in a cabinet leak. Air isn't passing across the disk so it can't be measured.

If the Intake door was leaking badly, it would reduce your ability to pull air across the orifice plate...BUT on exhaust testing the door is removed..YET you still have the same low readings.

I don't get it how you're pulling 28" to the top side of the disk and not showing a healthy pressure drop across it....To me, that says the air is just blowing right through a major leak and the bottom side of the disk is seeing darn near the same pressure. It's like the orifice isn't even there to restrict the flow...

You said you had the top chamber and test pressure feeds T'd into the same line. Check the T fitting...is it cracked...is it leaking....

Larry

[Mousehouse1]

Dom how many motors are you using? I think you said 6. What is the most cfm you have been able to pull with all 6? Just curious. I haven't had time to test my bench with all 10 of mine yet. Hopefully it will pull 600 but we will see.

I have no doubt that you will be able to figure out what is wrong with your bench. I changed/added a few things to my bench and they were a baffle in between the orifice disk and top chamber and I added a new top chamber and moved the pressure probe about 2" to the left of the head hold down fixture.

Larry, John, Bruce, Tom and others helped me figure out what was wrong with mine and/or came up with ideas on what to check and look at.

You might try taking a candle or lighter around the outside of your bench and see if it has any leaks in the seams. Larry told me to do this and I found a few small ones. Also block off your office disk completely and turn on a few motors (you shouldn't need many if your disk is sealed properly).

I am trying to find a way to block off my unused motors to see if they are causing any leakage. I will let you know what I find out.

[Mouse]

When you change to a larger orifice, any supporting structure/material near the orifice opening may be affecting your Cd (Coeffifient of Discharge) to a greater extent. What is the nearest structure and the proximity to the opening of the orifice?

John

[Dom G]

Thanks for the continuing support and ideas everyone, I appreciate it.

I'm going to try to respond to Larry, Mouse and Mousehouse1 since each of you commented or made suggestions to my last post.

I'll respond to Larry last since I made the changes he suggested and the results may mean something to you guys, but not to me at this point.

Mousehouse1

Yes, I have 6 motors presently. Since I've been struggling with testing up to this point I can't honestly say what the total cfm I've been able to pull. If the testing that suggests one of my orifice ranges is really accurate I know I can pull about 160 cfm with 4 motors. I may find I'll need to make many of the changes you made to get my bench straightened out. Since we are both using the same motors, I'm wondering how many motors you need to turn on when doing a leakage test @ 28"? I have to use 4.


Mouse

To answer your question about the nearest supporting structure or material I attached a picture I took when I was making the change Larry suggested. The two pressure fingers are about 7/8" high and 2 1/2"-3" away from each side of the orifice. Also the back wall is not too far away from the top of the orifice.

Larry

It takes 4 motors to pull 28" with the calibration plate and the 2" orifice.

You had mentioned to check my T fitting to make sure it wasn't cracked or leaking. Since I'm not using a T fitting a light went on in my head and said to reroute your vertical manometer pickup from the head adapter, where I actually have had it connected, to the probe running to the upper plenum to see if I get the same readings.

With the intake control valve in the same position using the calibration plate and 4 motors, I obtained the same 28" reading. I tried it again with a tee in the line as well and the reading was the same again. I'm not sure if this has any significance?

Next, I made the changes you suggested. I selected the 2.531" orifice. I covered 1/2 of it with a piece of metal and duct taped it in place. I also duct taped all other orifices and around the sealing ring so air could only theoretically pass through one half of the 2.531" orifice.

When you said to leave everything else in place, I assumed you meant leaving the calibration plate in place as well so I did.

Now the drum roll and the results.

With 4 motors on, I could only get to 20" of pressure when the inclined manometer got to 100%. I had to close down the control valve a bit to keep the inclined from going over 100%.

By the way, if you notice from one of the pictures I attached, I offset the hole in the benchtop from the orifice to avoid having a straight line.

So what do these results tell us and where do I go from here?

[Dom G]

I forgot the pictures. If I can remember how I did the last time they should be attached.

[Dom G]

Here's another