Pressure measurement

[APH]

Guys,

I'm a little low confused on the basic here. I need help.

I'm doing a bubble immersion test here, just for fun. The inlet air hose has pressure gage in it. I filled the enclosure with 30 psi of air ( reading from the gage) and I saw air bubble from the seam of my enclosure. Can I say that I got a leak problem at 30 psi.

What does the gage pressure measure for?. How do you measure the enclosure pressure when air buble start to show up?. In other word, the pressure gage on you air generator indicate the pressure inside your tire not the air pressure coming in the tire?

Am I loosing it or just suck at this.

APH

 

[quark]

You can say it as your enclosure (air)pressure. When you connect your compressor to an enclosure via a pipe then pressure starts building up(the gauge initially shows zero and and as the pressure builds up in the enclosure the pointer moves)

You are also right that your enclosure leaks at 30psi(gauge)provided your eye sight is good

Regards,

 

[APH]

Quark,

Thanks. Here the catch though, the gauge pressure doesn't start at zero. When the gage is at zero, there's no air flowing. When I put my thumb on the pipe outlet, the gage still read 30 psi. When I release the thumb the gage still read at 30 psi. Ig the gage is functioning correctly, it should be zero when I release my thumb and at 30 when I put my thumb.

Am I right????

APH

 

[quark]

What does the gauge read when the compressor is off? Actually you can't close the pipe with your thumb if the pressure is 30psig as far as I am concerned(ofcourse I weigh 56kgs with a height of 6'1"). You are right again.

Regards,

 

[APH]

When compresor is off, the gauge read zero.

Last night, I put put a pressure gage on the enclosure while supplying it with air and the gage read pretty close to what the gage in the pipe. So I guess the gage on the pipe measures the pressure inside the enclosure.


I'm still baffle, wish there's w website that talk about this basice pneumatic schematics.

APH

 

[sterl]

I believe what I heard was: I have a flowing hose, with a gauge near the oulet end. The outlet is actually considerably smaller than the inside (area) of the hose, otherwise I'm with quark, you couldn't close a 30-psi line with your thumb; and when I weighed 56 kilos, I wasn't anywhere near 6-1.

If the compressor or drive or what have you is valved off or disconnected from the gauge end, the gauge should go to zero....unless its a "telltale" gauge that stays at the maximu pressure it has ever seen, until you "reset" it.

If the hose is consideralby bigger than the outlet orifice, the flow through the hose itself will be slow, thus there will be small pressure drop from the inlet (compressor or tank0 end of the hose to the gauge...all the pressure drop occurred at the orifice. Thus the gauge reading didn't change much when flow was stopped by restricting or stopping the orifice.

Your leak probably occurred at a pressure considerably lower than 30 Psig, but it would have been impossible for the enclosure to have been at a pressure higher than 30-psi, and if the rest of my assumptions are correct, it would almost certainly been considerably lower.

Are you trying to estimate how fast it leaks at a given pressure?

Hope this helps...

 

[APH]

Sterl,

You are correct, the outlet is smaller than the hose. The outlet is about .25 inch ID. because I didn't believe what I was reading at the outlet gauge, I put another gauge directly on the enclosure body. I was hoping to get the pressure inside the enclosure by it. When I did this, the pressure gauge (on the enclosre body) read pretty close the same as the gauge on the outlet ( 2-3 psi different). So I guess, I could safely says that the pressure inside the enclosure is the same as the pressure at the outlet.

Let me clarify this. I saw air bubles at around 20 psi, even at this pressure I still am baffled, because I'm expecting to leak at pressure lower than 10 psi. I guess I don't know why unit is working better than what I expected.

Well..this experiment is probably not accurate of what I'm trying to accomplish with, now that I realized.

My unit is supposed to withstand rain, dust, sunlight, moisture,etc. We had a testing method we called rain and shine (basically a period of simulated rain and sunlight). I didn't get a consistence pass rate with my deign...so I'm trying to find a correlation between pressurizing the unit with the ability to withstand moisture which I don't think I'm in the right track.

APH