Leaving Air Compressor Full

[Leon]

Why do you drain under low pressure?

[Doug Miller]

Incorrect. Consider that pressures of 135psig ( = 150psia, or 10 atmospheres) are common even in small portable compressors.

[Robatoy]

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.

[Ken McIsaac]

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

[Leon]

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.

[Robatoy]

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?

[Doug Miller]

While that is all quite true, I'm not sure I see its significance to a discussion of the behavior of water vapor when compressed to ten atmospheres.

[Swingman]

IIRC, Willy had two bass players in one his bands ... but, and IIRC again, it was pretty much a mess, even for a bass player. :)

As far as who did it first, I posted pretty much the same thing last year in response to a similar post, but I doubt seriously the idea of using a drain hose originated with me ... I was just looking for a way to drain the tank without moving it, and the "unintended benefits" were too obvious for even a coonass to miss. :)

[Swingman]

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! ;)

[SWDeveloper]

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.

[Scott Lurndal]

While you're down there, replace that silly stopcock with a real ball-valve. Your fingers will be happier.

scott

[Scott Lurndal]

I think that depends both on 'how near' and 'which coast'.

scott

[Scott Lurndal]

It's like a Ni-cad. Let it get too empty and you can't fill it again.

scott.

(That there's a joke, son.)

[Greg O]

You need a Grainger item # 4KT04 I screwed around with the HF drain valve, two of them in fact, and gave up and spent the cash on this one. Easier to install, and it works. Greg

[Leon]

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.

[Swingman]

Besides DFTT, look up the verb "cavil" ... it may help you understand why you are basically engaged in pissing in the wind.

[CW]

[Lowell Holmes]

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.

[Allen Roy]

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....

[Tom Veatch]

Well, I figured it was worth 10 bucks to try it out. When I went to retrieve the URL, I noticed the 100psi limit. That may be new. I don't recall noticing that limit at the time I bought one several months ago. I run my 80 gal compressor at 135 psi shutoff and haven't seen any adverse effects.

Every few days, or whenever I think about it, I open the manual drain valve to verify that it's keeping the tank dry. So far, since installing the automatic drain, I've never had a drop of condensation come out the manual drain when I check it.

I'm satisfied.