Cabinet Leakage Testing - Fundamental Question?

[Dom G]

As some of you have read on other posts I have submitted during the last few days, I'm trying to perform cabinet leakage testing this weekend.

To show my inexperience with flowbench operations, it just occurred to me that I don't know whether minimal leakage in my cabinet will be indicated on the inclined manometer as being close to the upper end (100%) on the scale or closest to the lower end (0)?

In fact, I checked old threads and I couldn't find any specific mention of it. Everyone always says you want leakage under 5 CFM or so.

So which end is it?

Thanks.

Dom

[larrycavan]

[Dom G]

Larry

After I sent this post I ran a couple more tests and found a small leak in one of my temporary duct tape seals. When I put my finger over it the reading on the inclined scale went down so I knew the answer at that point.

The result I keep coming up with is just about .5 cfm which is hard to believe but very good news. On a 1 meter scale with a .750 diameter orifice assuming 12" rise, the reading at 28" was 120 on the scale.

If I may, I have a couple of questions.

Larry, you said in another post I sent about which ends of the inclined connections go where that for intake testing, which is all I've done so far, that high pressure was in the top plenum and pushes the fluid up the inclined manometer.

I'm having some difficulty understanding this since the pickup probe for the vertical manometer connects in the same plenum and it measures vacuum. What am I missing. Can you provide a simple explanation of what's occurring?

Another quick question. Again in another post about how to fill the vertical manometer you said to use a syringe. Are you talking about a medical one that diabetics use or something else that is commonly available?

Thanks again for your timely and informative responses.

Dom

[Thomas Vaught]

Dom,

What Larry was referring to was the higher pressure above the inclined manometer's flow orifice vs the lower pressure below the flow orifice during intake testing.

You have different pressures:

Atmospheric pressure outside the cabinet.

A different pressure (Atmospheric pressure -28" of h2o) below the cylinder head for example.

A third pressure (atmospheric pressure - 28"
h2o) - the pressure drop across the flow orifice
which in your case at full scale would be an additional 12" h2o lower so 40 inches difference between atmospheric pressure outside the cabinet and the motors inlets when testing at 28" test pressure and at 100 percent on the meter stick.

Tom V.

[larrycavan]

[resbum]

Hello All,

My project is advancing nicely though slowly, I doesn't help that I am working 600 miles from my home right now. I got an awsome 3 phase blower to move air recently.

Since I am a couple weeks away from getting it wired I was planning to do a "gross" leak test before I started making any holes for the head adapter, measuring orifice, wires etc.

I envision simply connecting a gauge to my shop vac, measuring the suction pressure, connecting it to the bench and repeating the reading. If it reads the same, I have a good sealing bench. If it is lower I have a leak.

After I make holes in vaious places I could repeat the process and see if I caused any leaks.

I have not yet made any holes in the partion where my measurement plate will be so I feel this initial test will give me an idea of how successful my carpentry skills were before I move to the next step in the build.

Anyone see anything wrong with this approach other than not just getting on with finishing it?

Steve

[resbum]

I am back home and I performed a leak test of the cabinet.

First, I only checked the partition between the pressurized and unpressurized sides. I had a 1" WC leak (.03 PSI) which I determined to be through the un painted MDF.

Next I pressurized the rest of the cabinet (four sides, top and bottom) and had a 9" WC leak. I fixed a small leak in a corner and ended with an 8" (.29 PSI) leak which I determined to be through the MDF.

I was surprised to see the amount of leakage through the MDF but it was confirmed by putting a piece of Saran Wrap near it and watching it get pulled onto the side and flatten out.

I am happy with my carpentry, now that I know I won't have to pull it apart to fix something I will prime it and recheck it to see how much it changed.

Steve Parker

[jfholm]

WOW! Steve you really have proved to us how important painting the inside is. If there was any question before, that is totally gone now. Bruce has been adamant about this and now I see why.

Thanks Again,
John

[86rocco1]

I wish I could remember who it was but, a quite while back someone having leakage issues with an unpainted particular board bench decided to test for leaks with soapy water, when he pressurized the bench, it turned into a big foamy block. The pictures were pretty telling, for any of us that saw them, the paint/don't paint issue was settled right then and there.

[bruce]

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