Leaving Air Compressor Full

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Buck Turgidson wrote:

I have a CH 4 gallon twin tank. I never leave it full and usually run the tool until the tanks are almost empty, then open the drain and allow the low pressure to blow whatever water is there out. The drain on this model is not on the very bottom of the lower tank, so I have to tilt the unit to drain. If I don't have enough air to finish, I turn the unit on with the drain open.
--

Bill
In Hamptonburgh, NY
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Why do you drain under low pressure?
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On Fri, 27 Apr 2007 17:23:49 GMT, "Leon"

I am not willshak, but I have observed (I have a Porter-Cable pancake style compressor) that if I just open the drain valve when the tank is pressurized, very little water comes out, even if I am holding the tank so the valve is the lowest point.
It is only after the air has almost entirely bled out of the tank (down around 30psi or so) that the bulk of the water is blown out. I am not able to explain this observation, but it seems to always happen that way.
I did leave it full once over a two week period because I was feeling lazy and doing a lot of trim carpentry. The water that came out after the two weeks was a nasty brown colour that convinced me the rust warning was to be taken seriously. I now drain it at the end of every day's work.
- Ken
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Water vapour condenses when the water/air mixture is compressed...ASSUMING the temperature stays the same...which it won't as air temperature increases when the pressure does during compression...... so we wait till it cools to the original ambient inle temperasture.... then it condenses.
When my Porter Cable pancake becomes difficult to lift, I drain it. (Besides, any water in your tank will diminish the air storage as water won't compress.)
Draining my vertical in the shop is a PITA, but I stole an idea from Swingman to make that easier. I'm buying a 90-degree fitting to replace the drain cock, and I am going to run a length of brake line along the side of the tank to the top where I will bend a swan neck and install the drain cock. It will be at eye-height and the air pressure will push the water up the line to an awaiting plastic bottle.
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Water vapor condenses regardless of pressure. Ever take a glass of ice water out side on a hot humid day? You get condensation on the cool sides of the glass. The condensation is formed when the humid air that has been heated up during compression, enteres the cooler compressor tank.
You can transfer humid compressed air to another container and there will be no condensation inside the tank as long as the temperature remains the same. Have you ever wondered why portable air tanks seldom if ever have no bleeder valve for releasing water?
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That's what I said, and I quote, including some fat, laptop induced typos: "so we wait till it cools to the original ambient inle temperasture.... then it condenses"
IOW.. when it cools.

If the air being transferred is humid, it condenses when it cools. When you move 100 gallons of 10% humid air into a 50 gallon container, the air compresses, but the water does not. The air/water ratio will therefore become 20%...by volume of humid air. I can put 400 gallons of 14.psig air into a 50 gallon tank..and all the water will go in there with it. As the volume decreases, the temperature and pressure increase... but the quantity of water stays the same.
IOW.. when I shove 100 gallons of air which contains 1 pint of water, into a 50 gallon tank, the pressure and temperature go up proportionally, but that pint of water stays a pint. Then when the whole mess cools off, the dewpoint now changes and the increased humidity condenses... and there is no way to reduce the quantity of air's occupying space without heating it up in the process. I think I got that right..LOL

I had never given that any thought... but I think that's related to duty-cycle.. just not enough air going through to matter.
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OK, I misunderstood, This part threw me, Water vapour condenses when the water/air mixture is compressed. I probably took that out of context. Sorry. It'lneverhappenagainuntilnexttime. ;~)

That's probably ture too.
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It gets really interesting when the pressure gets to be so high that the water in the air changes state from liquid to gas absorbing a lot of heat due to latency... unless the pressure is REALLY high, then water and steam change state without needing a whole lot of extra heat(pressure)... by that time, your tank will be a decal on the walls. I have a headache now.... what walls?
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"Robatoy" wrote in message

All I know is what any good country boy observed when putting his hay field induced, sweaty brow against the wall of the water well tank ... sure does feels good.
Or when he learned the cure for a "water logged" water well tank was to drain it, because, while air compressed, water did not! ;)
--
www.e-woodshop.net
Last update: 2/20/07
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LOL,, and sticking the air nozzle, that is attached to the hose on your compressor, inside your pants front pocket and lettin'er open up, really feels good on a hot sweaty day. Your pants tend to inflate and it's like wearing air conditioned pants.

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Hot weather work apparel. Just what any well dressed Texan needs. http://www.utilikilts.com/store/custom_product.php?products_id 

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Could you imagine steadying the ladder for someone wearing that....And if he is a true Irish Texan.....However I have heard of male postal workers wearing the standard issue skirt because of objections to them wearing shorts....

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OSHA might cite you for that. :-)
Don't use compressed air on your skin. They claim it can penetrate your skin or something. I'll do it on occasions though.
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LOL, I do it all the time but obviously don't blow it where you should not and don't blow extreme pressures where you should not.
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To protect the tools instead of the tank.
--
I am extraordinarily patient, provided I get my own way in the end.
- Margaret Thatcher
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