Leaving Air Compressor Full

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On Apr 28, 11:38 am, snipped-for-privacy@milmac.com (Doug Miller) wrote:

[snip]
There, let's get this over with.
oh.. AND DON'T FEED THE TROLL!!!!!
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Which one! I see quite a few in this thread! ;-) Greg
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You quoted him so I saw what Doug Miller had to say and,,,,,
I must say, isn't it polite jesture how Doug always ends his often toxic and condecending comments with,
Regards, Doug Miller
LOL
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"Leon" wrote in message

Say no more ... some would argue that's justification for another 'plonk' right there! :)
--
www.e-woodshop.net
Last update: 2/20/07
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I guess you're not familiar with the concept of a "sig" ?

--
Regards,
Doug Miller (alphageek at milmac dot com)
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You just can't *stand* it when I point out a mistake you made, can you?
Grow up, why dontcha?
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Dew point, condensation, partial pressures, humidity; come on guys. To roughly quote a former ng participant, "lets stick to stuff we know something about, like lektricity."
--
Often wrong, never in doubt.

Larry Wasserman - Baltimore Maryland - lwasserm(a)sdf. lonestar. org
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Well, good point, but through the years we have learned a lot about water in the tank also. ;~)
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Condensation building up in the tank, causing internal rust, eventually leading to tank rupture, is a long term possibility. Compressors have a drain valve on the tank for this reason.
--
Lloyd Baker

"Buck Turgidson" <jc snipped-for-privacy@hotmail.com> wrote in message
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I just disposed of one (an old one) that rusted through. It manifest itself through a pin hole leak in the bottom of the tank. I think if it had been bled properly through out it's life, it would still be here. If the condensate is rusty color, you know it is rusting.
I never leave air in my pancake compressor now. The pancake is easy to drain. The old tank required getting down in my knees and looking under the tank. I should have piped the drain to a valve located in the open where I could see it. I would have drained the tank more often.
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Buck Turgidson wrote:

Yes and no.
Typically, the smaller the compressor, the less efficient, and the more condensate it generates.
Not emptying the tank and bleeding off the condensate on a frequent basis leads to problems.
Lew
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How does the efficiency of the compressor make any difference?
--
Regards,
Doug Miller (alphageek at milmac dot com)
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You guys are making this too hard. It's just pV=nRT (ideal gas law).
1. Compressor takes in outside air, which typically has water vapor in it, and packs it into the tank, thus raising the pressure.
2. As you let air out of the tank, the pressure drops. This cools the air (as p goes down, do does T).
3. Cold air holds less moisture so liquid water condenses from the water vapor and collects in the tank.
Kevin
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snipped-for-privacy@email.unc.edu wrote:

So are you. :-)

And thus condensing the water vapor into liquid. End of story.

Not correct. It was *already* condensed when under pressure. Water accumulates in the tank during operation: air and water vapor, at ambient pressure, is taken in by the compressor. As it is compressed, some of the water vapor condenses into liquid and remains in the tank. Air withdrawn from the tank as the tools are used contains less water vapor than the air that was taken in, because some of the vapor remains behind in the tank as liquid. The longer the compressor is operated, the more water will accumulate in the tank.
--
Regards,
Doug Miller (alphageek at milmac dot com)
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Doug Miller wrote:

Only supersaturated air will condense upon compression. Normally, it won't happen.

The pressure also drops as the tank cools, whether it's being used or not. So does the dewpoint, so this is when normal air will start to condense.

That *is* correct.
--
Mortimer Schnerd, RN
mschnerdatcarolina.rr.com
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Doug's never wrong. Just ask him, he'll tell you. "Mortimer Schnerd, RN" <mschnerdatcarolina.rr.com> wrote in message

won't
So
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Look at a state diagram for water. Below the critical temperature/pressure, increasing pressure drives the liquid/vapor equilibrium point toward more liquid/less vapor which enhances condensation in a closed container. Point for Doug.
Decreasing temperature does the same. Below the critical temperature/pressure the reverse is also true; increasing temperature enhances evaporation in a closed container. Point for Kevin/Mortimer.
Critical temperature is the temperature above which water cannot exist in a liquid state no matter how much pressure is applied. For water, that is about 374C or 705F. Critical pressure is essentially the vapor pressure at critical temperature; about 217.7 atmospheres or 3200 psi.
Also note that the pressures involved are the partial pressures of the individual gases, not the total pressure of a mixture of gases. In a container of atmospheric air at total pressure of 10 atmospheres, the partial pressure of the water vapor will vary depending on the absolute humidity of the air, but it will be much less than 10 atm.
The equilibrium point (mass of liquid vs mass of vapor) in a closed container is a function of both temperature and pressure. Doug, Kevin, and Mortimer are simply arguing opposite sides of the same coin.
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RN" <mschnerdatcarolina.rr.com> wrote:

Incorrect. Consider that pressures of 135psig ( = 150psia, or 10 atmospheres) are common even in small portable compressors.
--
Regards,
Doug Miller (alphageek at milmac dot com)
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On Fri, 27 Apr 2007 17:51:18 GMT, snipped-for-privacy@milmac.com (Doug Miller) wrote:

From my college physics class... There is a sealed room with two bathtubs at normal temperatures and pressures. One bathtub is full of water at 90 degrees F. The other bathtub is empty and has a temperture of 72 degrees on the insides, the lowest temperture in the room. What happens in this closed system is all the water will evaporate from the 90-degree tub and the water vapor will condense into the 72-degree tub. This makes sense why houses have damp basements.
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