nagative percentage on leakage test

[SuperRunner]

I am getting about -15% on a leak test using a 1" orifice...what is that trying to tell me?

[Nick]

Your incline manometer lines are hooked up backwards, and you have a leak.


Nick

[SuperRunner]

Nope, not hooked up backwards. If un-seal the head adapter it will show greather than 0, but with it plugged to show leakage, the reading will go less than 0.

This is not the case on exhaust flow. It will actually show greater than 0 on a leak test.

My orifice is .87"

[SuperRunner]

I did some more testing. Either way I connect the tubes it shows a negative percent of flow.

Connected the correct way, it will flow .34 inches the wrong way. Connected the wrong way, it will flow about 3 inches the wrong way.

I tried using a 'T' off my test pressure and I got the same thing.

On an exhaust test I get about 30% or 9.3 cfm of leakage.(got a lot of little stuff I need to seal)

[Rick360]

Is this a homemade inclined manometer? What is the well made of? Is there any flexible tubing that has fluid in it on the inclined manometer?

It sounds like vacuum and pressure are flexing either the well of the manometer or tubing that has fluid in it causing the volume at zero to change. To test this you can tee the two manometer connections together and apply a single pressure or vacuum to tee into both manometer connections. There should be no movement in the fluid doing this.

Another possibility is a leak in the sensing line for flow.

Rick

[SuperRunner]

Rick, you were right on the leaking line. I had a leak in my reservoir...fixed. Seemed to more evident on exhaust rather than intake. Intake would probably help seal the leak. Anyway, I sealed the leak and guess what.....NO LEAKAGE, at least none detectable by the guage. I can feel a little bit at the front deck plate on an exhaust flow, but it isn't enough to make the guage move at all. Maybe I will try a larger orifice later to see if I can register cabinet leakage there.

Thanks