"Morris Dovey" <[email protected]> writes:
>Swingman wrote:
>
>| I moved the drain plug to the end of a 3' length of air hose on my
>| small vertical, where it is much more accessible.
>|
>| The air hose holds quite a bit of water that would otherwise be in
>| the tank, and, unlike the tank, is rustproof ... and gravity does
>| the work.
>|
>| It is a simple matter to open the cock slightly every other day or
>| so and let the water in the hose squirt out, and draining the tank
>| this way doesn't even cause the compressor to cycle on.
>
>Great idea - consider it stolen :-)
>
While you're down there, replace that silly stopcock with a real
ball-valve. Your fingers will be happier.
scott
"Mike Marlow" <[email protected]> wrote in message
news:[email protected]...
>>
>
> Close but not quite. It's the act of compressing the air that causes the
> water build up in the tank.
It's the heat generated during compression that causes condensation to build
up in the tank. Compress air with out changing the temperature and you have
no condensation during that process.
Tom Veatch wrote:
> On Mon, 30 Apr 2007 17:41:08 GMT, B A R R Y <[email protected]>
> wrote:
>
>> What if it takes my compressor a week or two to drain down, so there's a
>> sizable change I might use the energy? If I have half left, I use half
>> as much enegery refilling the tank.
>
>
> Leave the tank pressurized and shut power off to the motor.
I do.
On Mon, 30 Apr 2007 17:41:08 GMT, B A R R Y <[email protected]>
wrote:
>
>What if it takes my compressor a week or two to drain down, so there's a
>sizable change I might use the energy? If I have half left, I use half
>as much enegery refilling the tank.
Leave the tank pressurized and shut power off to the motor.
The normal failure mode of a tank pressurized within specifications is
to develop a pinhole leak, not to explode catastrophically. So there
is very little risk in leaving it pressurized. Understand that is not
the case if the failure is due to overpressurization. In that case,
the failure can be catastrophic so make sure the pressure relief valve
is properly set and functioning.
On Apr 26, 6:50 pm, "Buck Turgidson" <[email protected]> wrote:
> Partially out of laziness, inertia, procrastination, and partially because I
> use it several times a month, I leave my Porter Cable air compressor full.
> Does this do longterm harm to the machine?
no
On Apr 26, 7:57 pm, lwhaley <[email protected]> wrote:
> On Apr 26, 6:50 pm, "Buck Turgidson" <[email protected]> wrote:
>
> > Partially out of laziness, inertia, procrastination, and partially because I
> > use it several times a month, I leave my Porter Cable air compressor full.
> > Does this do longterm harm to the machine?
>
> no
I've been led to believe that the compressed air will create moisture/
condensation in the unit which obviously can do damage. I usually try
to remember to bleed mine.
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
On 27 Apr, 00:50, "Buck Turgidson" <[email protected]> wrote:
> I leave my Porter Cable air compressor full.
> Does this do longterm harm to the machine?
In general, no. However a machine that has a slow leak down somewhere
and is going to be switched off for long enough to empty itself is
usually best vented deliberately rather than being left to do it
inevitably itself (or just fix the leak!)
You should of course always blow down the water after any sufficient
use of the compressor. This doesn't mean emptying the reservoir
though. Nor does it require doing if the reservoir has been left full
long-term with the compressor off, except possibly if you've had major
temperature changes.
On Apr 26, 6:50 pm, "Buck Turgidson" <[email protected]> wrote:
> Partially out of laziness, inertia, procrastination, and partially because I
> use it several times a month, I leave my Porter Cable air compressor full.
> Does this do longterm harm to the machine?
I have a 6 gallon pancake compressor by Porter Cable. When I use it
it's only for an hour or two. Afterwards, when I bleed it I see water
coming out of the tank. So I bleed it after each use. It only takes a
few minutes to compress the unit so it's well worth the effort. So my
recommendation is, if you see water coming out when you bleed the
tank, then bleed the tank whenever you are done using it.
On Apr 27, 11:00 am, "Morris Dovey" <[email protected]> wrote:
>
>
> Great idea - consider it stolen :-)
>
> Thanks!
>
Ditto.
Thanks
On Apr 27, 11:08 am, B A R R Y <[email protected]> wrote:
> Swingman wrote:
>
> > I moved the drain plug to the end of a 3' length of air hose on my small
> > vertical, where it is much more accessible.
>
> That's exactly what I did.
Sooo who did it first? Who am I 'really' stealing this from?
Stay tuned.
Film at 11.
On Apr 26, 7:50 pm, "Buck Turgidson" <[email protected]> wrote:
> Partially out of laziness, inertia, procrastination, and partially because I
> use it several times a month, I leave my Porter Cable air compressor full.
> Does this do longterm harm to the machine?
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.
On Apr 27, 12:01 pm, B A R R Y <[email protected]> wrote:
>
> Must be bass players thinking alike...
>
Oh noes...... two solos, duet style?
On Apr 27, 1:21 pm, "Leon" <[email protected]> wrote:
> "Robatoy" <[email protected]> wrote in message
>
> news:[email protected]...
>
>
>
> > 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.
>
> 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.
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.
>
> 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.
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
>Have you ever wondered why portable air tanks seldom if ever have no
> bleeder valve for releasing water?
I had never given that any thought... but I think that's related to
duty-cycle.. just not enough air going through to matter.
On Apr 27, 2:44 pm, "Leon" <[email protected]> wrote:
>
> OK, I misunderstood, This part threw me, Water vapour condenses when the
> water/air mixture is
> compressed.
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?
On Apr 28, 11:38 am, [email protected] (Doug Miller) wrote:
> In article <%[email protected]>, "Leon" <[email protected]> wrote:
>
>
>
> >"Mike Marlow" <[email protected]> wrote in message
[snip]
>
> This is simply false.
> Either you don't remember what you wrote,
> you have a language comprehension problem
> you're just a liar.
> falsely claimed
> attempting to deceive
> you mischaracterized what you wrote.
> And that's dishonest.
> And so are you.
> Regards,
> Doug Miller
There, let's get this over with.
oh.. AND DON'T FEED THE TROLL!!!!!
On Apr 28, 2:06 pm, "Leon" <[email protected]> wrote:
> > Doug Miller wrote:
> >> In article <[email protected]>, "Leon"
> >> <[email protected]> wrote:
>
> >>> You are on the right track.
> >>> Actually the compressed air does not create the condensation. It is
> >>> the heat generated from compressing the humid air that causes the
> >>> condensation.
>
> >> Incorrect. It is *exactly* the compression that causes the condensation:
> >> water that is vapor at ambient pressure can be condensed into liquid by
> >> increasing the pressure.
>
> So Doug, I suspect you believe it is the pressure from "your firm grip" on
> a glass of ice water that causes the warm humid air surrounding the glass to
> cause condensation on the cool side of the glass.
In his case, it would likely be a glass of vinegar.
It would be better if it was bourbon or something, maybe he'd lighten-
the-fuck-up.
but alas... I said too much.
On Apr 26, 6:50 pm, "Buck Turgidson" <[email protected]> wrote:
> Partially out of laziness, inertia, procrastination, and partially because I
> use it several times a month, I leave my Porter Cable air compressor full.
> Does this do longterm harm to the machine?
On a related question... why are air dryers placed after the
compressor and not before it?
Thanks
TMT
On Apr 29, 7:24 pm, Lew Hodgett <[email protected]> wrote:
>
> Question:
>
> Which container contains the most pounds of water vapor?
That would be the shop-dog's bladder.
On 27 Apr, 16:10, B A R R Y <[email protected]> wrote:
> Andy Dingley wrote:
>
> > In general, no. However a machine that has a slow leak down somewhere
> > and is going to be switched off for long enough to empty itself is
> > usually best vented deliberately rather than being left to do it
> > inevitably itself (or just fix the leak!)
>
> Why is that?
A compressor is a pressure vessel, i.e. it's potentially dangerous if
left pressurised. The risk is small, the convenience and energy saving
of leaving it full outweighs this if we're going to come back to it
later and use that stored pressure.
However if we've got a leak, or we're leaving it for a long time such
that we're _not_ going to benefit from that stored energy, then good
practice is to not leave it lying around. You don't know what it's
going to do, but it ain't going to bake you a cake. There's also the
risk of leaving the compressor powered up (and leaking), which is just
a sizable waste of energy.
On Apr 30, 11:01 pm, "Edwin Pawlowski" <[email protected]> wrote:
> "B A R R Y" <[email protected]> wrote in message
>
>
>
> > What if it takes my compressor a week or two to drain down, so there's a
> > sizable change I might use the energy? If I have half left, I use half as
> > much enegery refilling the tank.
>
> But does it take more energy to fill the second half than the first half?
Yes
Buck Turgidson wrote:
> Partially out of laziness, inertia, procrastination, and partially because I
> use it several times a month, I leave my Porter Cable air compressor full.
> Does this do longterm harm to the machine?
>
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
"Michael Faurot" <[email protected]> wrote in message
news:[email protected]...
> Tom Veatch <firstname_lastname AT pixius dot net> wrote:
>
>> >Bottom line... it's probably better to dump the air when you're
>> >done... at least for shop compressors.
>
>> Or:
>> http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=42221
>
>
> I bought one of these from HF, when I bought a new compressor
> recently. I must have spent the better part of a day or so trying to
> figure out a way to install this. The main problem I ran into is with
> the air hose supplied and the compression fittings it uses.
> Basically there weren't enough parts there to splice this device into
> the system as they don't give you any additional compression fittings.
> On my compressor, there's a solid copper line running between the
> tank and the regulator. So I would need two more fittings to
> rework things so that the automatic drain valve could be tee'd in
> between the tank and the regulator.
>
> I spent several hours trying to find more of those fittings locally,
> but none of the hardware stores had them and HF itself does not
> sell them. Perhaps a specialized industrial supply would have them,
> but after spending a few hours trying to hunt stuff down, I gave
> up and returned the device. The device itself probably works fine,
> but you'd likely need to dig up some other type of way to splice
> it into your system that uses some other type of fittings and hose.
> It would be nice if they'd supply additional male and female
> compression fittings with the device, even if that increased the
> price of the device by a few bucks.
>
> In the end, I found it's easy enough to just open the drain at the
> bottom once a day and let it blow out the accumulated moisture.
>
> --
>
> If you want to reply via email, change the obvious words to numbers and
> remove ".invalid".
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
"Robatoy" <[email protected]> wrote in message
news:[email protected]...
>
>
> oh.. AND DON'T FEED THE TROLL!!!!!
>
Which one!
I see quite a few in this thread! ;-)
Greg
Edwin Pawlowski wrote:
> <Tom Veatch> wrote in message
>> Everything that is correct in this thread follows from those basic
>> facts of physics.
>
> That easy. Now try to explain where everything wrong in this thread came
> from. C'mon, I dare ya!
>
Egypt?
It's just a guess. ;-)
--
http://nmwoodworks.com/cube
---
avast! Antivirus: Outbound message clean.
Virus Database (VPS): 000738-2, 05/04/2007
Tested on: 5/4/2007 11:45:16 PM
avast! - copyright (c) 1988-2007 ALWIL Software.
http://www.avast.com
On Fri, 27 Apr 2007 17:23:49 GMT, "Leon"
<[email protected]> wrote:
>
>"willshak" <[email protected]> wrote in message
>news:[email protected]...
>> 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.
>
>Why do you drain under low pressure?
>
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
In article <[email protected]>,
Too_Many_Tools <[email protected]> wrote:
> On Apr 26, 6:50 pm, "Buck Turgidson" <[email protected]> wrote:
> > Partially out of laziness, inertia, procrastination, and partially because I
> > use it several times a month, I leave my Porter Cable air compressor full.
> > Does this do longterm harm to the machine?
>
> On a related question... why are air dryers placed after the
> compressor and not before it?
>
To protect the tools instead of the tank.
--
I am extraordinarily patient, provided I get my own way in the end.
- Margaret Thatcher
In article <[email protected]>, "Leon" <[email protected]> wrote:
>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
I guess you're not familiar with the concept of a "sig" ?
>
>
--
Regards,
Doug Miller (alphageek at milmac dot com)
It's time to throw all their damned tea in the harbor again.
"Larry W" <[email protected]> wrote in message
news:[email protected]...
> 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."
>
>
Well, good point, but through the years we have learned a lot about water in
the tank also. ;~)
On Sun, 29 Apr 2007 05:11:22 GMT, Lew Hodgett
<[email protected]> wrote:
>Too_Many_Tools wrote:
>
>> On a related question... why are air dryers placed after the
>> compressor and not before it?
>
>Remember, "Willie, The Actor" Sullivan, a bank robber of some notarity.
>
>When asked, "Willie, why do you rob banks?"
>
>He answered, "Because that's where they keep the money."
>
>Why put a dryer after the compressor, because that is where the water is.
>
>Lew
If you dry the air going into the compressor, you'll have dry air in
the storage tank. The compressor doesn't create water.
Swingman wrote:
| I moved the drain plug to the end of a 3' length of air hose on my
| small vertical, where it is much more accessible.
|
| The air hose holds quite a bit of water that would otherwise be in
| the tank, and, unlike the tank, is rustproof ... and gravity does
| the work.
|
| It is a simple matter to open the cock slightly every other day or
| so and let the water in the hose squirt out, and draining the tank
| this way doesn't even cause the compressor to cycle on.
Great idea - consider it stolen :-)
Thanks!
--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/
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....
"CW" <[email protected]> wrote in message
news:[email protected]...
> Hot weather work apparel. Just what any well dressed Texan needs.
> http://www.utilikilts.com/store/custom_product.php?products_id=19
>
Leon wrote:
| "Morris Dovey" <[email protected]> wrote in message
| news:[email protected]...
|| Swingman wrote:
||
||| Yeah, we really do need a good isothermal shop compressor on the
||| market.
||
|| I'd be happy to settle for an adiabatic discussion...
|
| Would that theory be economically possible in this situation?
In theory, yes - but (as we all know) in theory there is no difference
between theory and reality, but in reality there is... :-|
--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/Absorber.html
Doug Miller wrote:
> In article <[email protected]>, "Leon" <[email protected]> wrote:
>
>
>> You are on the right track.
>> Actually the compressed air does not create the condensation. It is the
>> heat generated from compressing the humid air that causes the condensation.
>>
>
> Incorrect. It is *exactly* the compression that causes the condensation: water
> that is vapor at ambient pressure can be condensed into liquid by increasing
> the pressure.
After reading your post, it reminded me of the fact that in order to
bottle liquid oxygen, they have to cool *and* put it under high pressure
to get it to condense to a liquid, but I never would have thought to
apply this principle to an everyday compressor. Good info.
"Leon" <[email protected]> wrote in message
news:[email protected]...
>
>> 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.
>
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.
"Doug" <[email protected]> wrote in message
news:[email protected]...
> On Apr 26, 7:57 pm, lwhaley <[email protected]> wrote:
> > On Apr 26, 6:50 pm, "Buck Turgidson" <[email protected]> wrote:
> >
> > > Partially out of laziness, inertia, procrastination, and partially
because I
> > > use it several times a month, I leave my Porter Cable air compressor
full.
> > > Does this do longterm harm to the machine?
> >
> > no
>
> I've been led to believe that the compressed air will create moisture/
> condensation in the unit which obviously can do damage. I usually try
> to remember to bleed mine.
>
Close but not quite. It's the act of compressing the air that causes the
water build up in the tank. Drain it before you use it and you'll find
yourself well enough protected in practical terms, for the life of the
compressor.
--
-Mike-
[email protected]
On Fri, 27 Apr 2007 17:51:18 GMT, [email protected] (Doug Miller)
wrote:
>In article <[email protected]>, "Mortimer Schnerd, RN" <mschnerdatcarolina.rr.com> wrote:
>>Doug Miller wrote:
>>>> 1. Compressor takes in outside air, which typically has water vapor
>>>> in it, and packs it into the tank, thus raising the pressure.
>>>
>>> And thus condensing the water vapor into liquid. End of story.
>>
>>
>>Only supersaturated air will condense upon compression. Normally, it won't
>>happen.
>
>Incorrect. Consider that pressures of 135psig ( = 150psia, or 10 atmospheres)
>are common even in small portable compressors.
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.
"Edwin Pawlowski" <[email protected]> wrote in message
news:[email protected]...
>
> "Swingman" <[email protected]> wrote in message
>> RCH's are being unnecessarily split on this subject ... it matters not
>> that
>> you blame death by gunshot on the gun, the shooter, or the trauma from
>> the
>> bullet, you're still dead.
>
> Yes, but it is either split hairs this morning or go out and clean up the
> yard.
>
ROTFLMAO..... At least you and I know what we are talking about.. ;~) LOL
Buck Turgidson wrote:
> Partially out of laziness, inertia, procrastination, and partially because I
> use it several times a month, I leave my Porter Cable air compressor full.
> Does this do longterm harm to the machine?
>
I leave my own compressor full, and know of some that have been full
for 15 years. <G>
"Lowell Holmes" <[email protected]> wrote in message
news:4SwYh.58$IJ3.30@trnddc07...
>
> "Leon" <[email protected]> wrote in message
> news:[email protected]...
>>
>>> 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.
>>
> 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.
>
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.
Doug Miller wrote:
>> 1. Compressor takes in outside air, which typically has water vapor
>> in it, and packs it into the tank, thus raising the pressure.
>
> And thus condensing the water vapor into liquid. End of story.
Only supersaturated air will condense upon compression. Normally, it won't
happen.
>> 2. As you let air out of the tank, the pressure drops. This cools the
>> air (as p goes down, do does T).
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.
>> 3. Cold air holds less moisture so liquid water condenses from the
>> water vapor and collects in the tank.
That *is* correct.
--
Mortimer Schnerd, RN
mschnerdatcarolina.rr.com
In article <[email protected]>, SWDeveloper <[email protected]> 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.
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.
--
Regards,
Doug Miller (alphageek at milmac dot com)
It's time to throw all their damned tea in the harbor again.
In article <[email protected]>, "Leon" <[email protected]> wrote:
>
>
>> Doug Miller wrote:
>>> In article <[email protected]>, "Leon"
>>> <[email protected]> wrote:
>>>
>>>
>>>> You are on the right track.
>>>> Actually the compressed air does not create the condensation. It is
>>>> the heat generated from compressing the humid air that causes the
>>>> condensation.
>>>
>>> Incorrect. It is *exactly* the compression that causes the condensation:
>>> water that is vapor at ambient pressure can be condensed into liquid by
>>> increasing the pressure.
>
>So Doug, I suspect you believe it is the pressure from "your firm grip" on
>a glass of ice water that causes the warm humid air surrounding the glass to
>cause condensation on the cool side of the glass.
Of course not. Vapor condenses as a result of being compressed, or cooled, or
both -- but never as a result of being heated. Warm humid air surrounding a
glass of ice water produces condensation on the side of the glass because the
temperature of the surface of the glass is below the dew point. The water
vapor condenses because it is cooled.
--
Regards,
Doug Miller (alphageek at milmac dot com)
It's time to throw all their damned tea in the harbor again.
"Robatoy" <[email protected]> wrote in message
news:[email protected]...
>>
>> > 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.
>>
>> 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.
>
> 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.
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. ;~)
>>Have you ever wondered why portable air tanks seldom if ever have no
>> bleeder valve for releasing water?
>
> I had never given that any thought... but I think that's related to
> duty-cycle.. just not enough air going through to matter.
That's probably ture too.
In article <[email protected]>, "Leon" <[email protected]> wrote:
>You are on the right track.
>Actually the compressed air does not create the condensation. It is the
>heat generated from compressing the humid air that causes the condensation.
Incorrect. It is *exactly* the compression that causes the condensation: water
that is vapor at ambient pressure can be condensed into liquid by increasing
the pressure.
Increasing temperature *cannot* cause condensation; quite the opposite, in
fact.
>Take a glass of ice water out into a hot humid place and you will get
>condensation on the outside of the glass.
Yes, that's because the warm water vapor in the air is being *cooled* by the
cold glass, and condenses onto it. Condensation is the result of a decrease in
temperature (that's why dew appears overnight, not in the middle of the day)
or by an increase in pressure.
>Once a compressor has stopped
>running and cools the condensation stops.
Again incorrect. As long as the pressure remains high, the vapor will remain
condensed.
>The longer the compressor runs
>and the more heat generated the greater the condensation.
Once again incorrect. It's the pressure, not the heat, that condenses the
vapor.
> Soooo, if you let the compressor cool and bleed off just the excess
>condensation there should be no more water build up when the compressor sets
>idle.
Still off the mark.
>Typically however, no one remembers to return to the compressor to bleed the
>condensation after the compressor has cooled. Bleeding is a good practice
>and total bleeding insures that you don't have to stand around waiting for
>all the water to blow out.
>Typically also, the faster and fewer times a compressor cycles the less
>build up of condensation you will get regardless of the volume being
>compressed.
Nonsense. The amount of condensation depends on the amount and humidity of the
air being drawn into the compressor, and the pressure to which it is
compressed. Nothing more. It has absolutely no relation to the compressor duty
cycle.
>If you fill an empty tank form a cool compressor tank that is not running,
>there will be no condensation generated.
That's because you're *reducing* the pressure. It has nothing to do with the
temperature.
--
Regards,
Doug Miller (alphageek at milmac dot com)
It's time to throw all their damned tea in the harbor again.
"Lew Hodgett" <[email protected]> wrote in message
news:[email protected]...
> Too_Many_Tools wrote:
>
>> On a related question... why are air dryers placed after the
>> compressor and not before it?
>
> Remember, "Willie, The Actor" Sullivan, a bank robber of some notarity.
No, not all. Mr. Sullivan never robbed banks. Willie Sutton did.
Real fact is, he did not make that statement but is from the mind of some
reporter. He did, however, enjoy robbing banks and said so.
"B A R R Y" wrote in message
> Robatoy wrote:
> > On Apr 27, 12:01 pm, B A R R Y wrote:
> >
> >> Must be bass players thinking alike...
> >>
> >
> > Oh noes...... two solos, duet style?
> >
> >
>
> We're going to get together and play "Big Bottom". <G>
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. :)
--
www.e-woodshop.net
Last update: 2/20/07
KarlC@ (the obvious)
"Leon" <[email protected]> wrote in message
news:%[email protected]...
>
> "Mike Marlow" <[email protected]> wrote in message
> news:[email protected]...
>
>>>
>>
>> Close but not quite. It's the act of compressing the air that causes the
>> water build up in the tank.
>
> It's the heat generated during compression that causes condensation to
> build up in the tank. Compress air with out changing the temperature and
> you have no condensation during that process.
It is actually the cooler tank and air lines that causes the vapor in the
heated air to condense. That is why large systems use refrigerated dryers.
The moisture is already in the air, compressing it concentrates it into a
smaller area.
<Tom Veatch> wrote in message
news:[email protected]...
> On Sun, 29 Apr 2007 05:11:22 GMT, Lew Hodgett
> <[email protected]> wrote:
>
> If you dry the air going into the compressor, you'll have dry air in
> the storage tank. The compressor doesn't create water.
Consider this. Given the proper sized compressor the amount of air being
dried on the "exhaust side" is much less than the air on the "in take" side.
The dryer would have to dry much faster on the intake side. Typically with
the correct sized compressor for the task at hand the exhaust side releases
air at a smaller CFM than the intake side. Additionally, the compressor
tank catches a majority of the water and lessens the work on the dryer.
Doug wrote:
> I've been led to believe that the compressed air will create moisture/
> condensation in the unit which obviously can do damage. I usually try
> to remember to bleed mine.
Compressed air doesn't create moisture; it only compresses what already exists
in the atmosphere that day. The process of compression creates heat, which will
allow more moisture to stay in the vaporous state. Later, as the tank cools
down, that vapor may well condense since cool air can't hold as much moisture as
warm air.
As a former scuba instructor, I'd always taught my students to never let a tank
run completely empty as positive air pressure kept moist ambient air from
entering the tank. However scuba air is MUCH drier than shop air. Given that
shop compressors don't usually filter out moisture as scuba compressors do, it's
a bad practice to just let that moist air sit in the storage vessel, rusting it
out over time.
Bottom line... it's probably better to dump the air when you're done... at least
for shop compressors.
--
Mortimer Schnerd, RN
mschnerdatcarolina.rr.com
"willshak" <[email protected]> wrote in message
news:[email protected]...
> 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.
Why do you drain under low pressure?
Doug's never wrong. Just ask him, he'll tell you.
"Mortimer Schnerd, RN" <mschnerdatcarolina.rr.com> wrote in message
news:[email protected]...
> Doug Miller wrote:
> >> 1. Compressor takes in outside air, which typically has water vapor
> >> in it, and packs it into the tank, thus raising the pressure.
> >
> > And thus condensing the water vapor into liquid. End of story.
>
>
> Only supersaturated air will condense upon compression. Normally, it
won't
> happen.
>
>
> >> 2. As you let air out of the tank, the pressure drops. This cools the
> >> air (as p goes down, do does T).
>
>
> 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.
>
>
> >> 3. Cold air holds less moisture so liquid water condenses from the
> >> water vapor and collects in the tank.
>
>
> That *is* correct.
>
>
>
> --
> Mortimer Schnerd, RN
> mschnerdatcarolina.rr.com
>
>
Edwin Pawlowski wrote:
> "B A R R Y" <[email protected]> wrote in message
>> What if it takes my compressor a week or two to drain down, so there's a
>> sizable change I might use the energy? If I have half left, I use half as
>> much enegery refilling the tank.
>
> But does it take more energy to fill the second half than the first half?
>
I'll never know, because I leave it full and switch it on when I need
it. Sometimes the motor starts, other times it doesn't.
I sleep well, too! <G>
Robatoy wrote:
> On Apr 27, 12:01 pm, B A R R Y <[email protected]> wrote:
>
>> Must be bass players thinking alike...
>>
>
> Oh noes...... two solos, duet style?
>
>
We're going to get together and play "Big Bottom". <G>
Buck Turgidson wrote:
> Partially out of laziness, inertia, procrastination, and partially because I
> use it several times a month, I leave my Porter Cable air compressor full.
> Does this do longterm harm to the machine?
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
"Leon" <[email protected]> writes:
>
>"DouginUtah" <[email protected]> wrote in message
>news:[email protected]...
>>I have a 2 HP, 20 gallon Craftsman compressor. I drain it about every five
>>years and never release the pressure at the end of the day.
>>
>> I have been using it since 1973.
>>
>> It was getting really hot when shingling so I changed the oil last fall.
>> Don't know if that helped--maybe I just slowed down a bit. :-)
>
>
>If you lived anywhere near the coast your compressor would have filled with
>water in a couple of years.
>
I think that depends both on 'how near' and 'which coast'.
scott
"Edwin Pawlowski"
"Leon" wrote in message
>
> >
> > "Mike Marlow" wrote in message
> >
> >
> >>>
> >>
> >> Close but not quite. It's the act of compressing the air that causes
the
> >> water build up in the tank.
> >
> > It's the heat generated during compression that causes condensation to
> > build up in the tank. Compress air with out changing the temperature
and
> > you have no condensation during that process.
>
> It is actually the cooler tank and air lines that causes the vapor in the
> heated air to condense. That is why large systems use refrigerated
dryers.
> The moisture is already in the air, compressing it concentrates it into a
> smaller area.
RCH's are being unnecessarily split on this subject ... it matters not that
you blame death by gunshot on the gun, the shooter, or the trauma from the
bullet, you're still dead.
All you guys should go back and review the components of the Ideal Gas Laws.
By the time you've compressed all the science contained therein into your
brain tanks, all the silly hot air on the subject will have evaporated. :)
--
www.e-woodshop.net
Last update: 2/20/07
KarlC@ (the obvious)
"B A R R Y" wrote in message
> If the compressor is full of water, will the water put out the fire
> after the ungrounded dust collector explosion?
Yabbut, that depends upon whether the HP rating of the compressor is correct
for its voltage, whether the circuit ampacity is properly sized for start up
voltage, with NEC approved and properly sized conductors attached to a
circuit breaker, of sufficient ampacity, in a properly grounded, or properly
ungrounded, sub panel.
But hey, look on the bright side ... the BIG question has been answered!
Whether or not that damp spot on the shop floor is actually from rising sea
levels due to human induced global warming, the shop dog not being let out,
or water leaking from the compressor tank?
Gee ... just think, now that we know how/why it got there on a molecular
level, we don't have to worry about that no more!
--
www.e-woodshop.net
Last update: 2/20/07
KarlC@ (the obvious)
"DouginUtah" <[email protected]> wrote in message
news:[email protected]...
>I have a 2 HP, 20 gallon Craftsman compressor. I drain it about every five
>years and never release the pressure at the end of the day.
>
> I have been using it since 1973.
>
> It was getting really hot when shingling so I changed the oil last fall.
> Don't know if that helped--maybe I just slowed down a bit. :-)
If you lived anywhere near the coast your compressor would have filled with
water in a couple of years.
"B A R R Y" wrote in message
> Doug wrote:
> >
> > I've been led to believe that the compressed air will create moisture/
> > condensation in the unit which obviously can do damage. I usually try
> > to remember to bleed mine.
>
> Removing water is totally different than letting out the pressure.
Ditto ...
I moved the drain plug to the end of a 3' length of air hose on my small
vertical, where it is much more accessible.
The air hose holds quite a bit of water that would otherwise be in the tank,
and, unlike the tank, is rustproof ... and gravity does the work.
It is a simple matter to open the cock slightly every other day or so and
let the water in the hose squirt out, and draining the tank this way doesn't
even cause the compressor to cycle on.
--
www.e-woodshop.net
Last update: 2/20/07
KarlC@ (the obvious)
In article <%[email protected]>, "Leon" <[email protected]> wrote:
>
>"Mike Marlow" <[email protected]> wrote in message
>news:[email protected]...
>
>>>
>>
>> Close but not quite. It's the act of compressing the air that causes the
>> water build up in the tank.
>
>It's the heat generated during compression that causes condensation to build
>up in the tank. Compress air with out changing the temperature and you have
>no condensation during that process.
This is simply false. Heating causes *evaporation*, not condensation.
Vapor condenses into liquid when it is either compressed, or cooled, or both.
But *never* when heated unless simultaneously compressed by an even greater
factor.
--
Regards,
Doug Miller (alphageek at milmac dot com)
It's time to throw all their damned tea in the harbor again.
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" <[email protected]> wrote in message
news:[email protected]...
> Partially out of laziness, inertia, procrastination, and partially because
> I use it several times a month, I leave my Porter Cable air compressor
> full. Does this do longterm harm to the machine?
>
Hot weather work apparel. Just what any well dressed Texan needs.
http://www.utilikilts.com/store/custom_product.php?products_id=19
"Leon" <[email protected]> wrote in message
news:[email protected]...
>
> 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.
>
"Doug" <[email protected]> wrote in message
news:[email protected]...
> On Apr 26, 7:57 pm, lwhaley <[email protected]> wrote:
>> On Apr 26, 6:50 pm, "Buck Turgidson" <[email protected]> wrote:
>>
>> > Partially out of laziness, inertia, procrastination, and partially
>> > because I
>> > use it several times a month, I leave my Porter Cable air compressor
>> > full.
>> > Does this do longterm harm to the machine?
>>
>> no
>
> I've been led to believe that the compressed air will create moisture/
> condensation in the unit which obviously can do damage. I usually try
> to remember to bleed mine.
>
You are on the right track.
Actually the compressed air does not create the condensation. It is the
heat generated from compressing the humid air that causes the condensation.
Take a glass of ice water out into a hot humid place and you will get
condensation on the outside of the glass. Once a compressor has stopped
running and cools the condensation stops. The longer the compressor runs
and the more heat generated the greater the condensation.
Soooo, if you let the compressor cool and bleed off just the excess
condensation there should be no more water build up when the compressor sets
idle.
Typically however, no one remembers to return to the compressor to bleed the
condensation after the compressor has cooled. Bleeding is a good practice
and total bleeding insures that you don't have to stand around waiting for
all the water to blow out.
Typically also, the faster and fewer times a compressor cycles the less
build up of condensation you will get regardless of the volume being
compressed.
If you fill an empty tank form a cool compressor tank that is not running,
there will be no condensation generated.
"Robatoy" <[email protected]> wrote in message
news:[email protected]...
>
> 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.
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?
In article <[email protected]>, "Leon" <[email protected]> wrote:
>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
You just can't *stand* it when I point out a mistake you made, can you?
Grow up, why dontcha?
Andy Dingley wrote:
>
> However if we've got a leak, or we're leaving it for a long time such
> that we're _not_ going to benefit from that stored energy, then good
> practice is to not leave it lying around.
Sounds pretty anal to me.
> There's also the
> risk of leaving the compressor powered up (and leaking), which is just
> a sizable waste of energy.
Agreed on that one.
What if it takes my compressor a week or two to drain down, so there's a
sizable change I might use the energy? If I have half left, I use half
as much enegery refilling the tank.
"scouter3" <[email protected]> wrote in message
news:[email protected]...
> 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" <[email protected]> wrote in message
> news:[email protected]...
>> Partially out of laziness, inertia, procrastination, and partially
>> because I use it several times a month, I leave my Porter Cable air
>> compressor full. Does this do longterm harm to the machine?
>>
>
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.
"Swingman" <[email protected]> wrote in message
news:[email protected]...
>
> RCH's are being unnecessarily split on this subject ... it matters not
> that
> you blame death by gunshot on the gun, the shooter, or the trauma from the
> bullet, you're still dead.
Are you sure that dead horse is not going to get up??? What if I kick it a
couple more times? LOL
> All you guys should go back and review the components of the Ideal Gas
> Laws.
> By the time you've compressed all the science contained therein into your
> brain tanks, all the silly hot air on the subject will have evaporated. :)
Yeah, I'm sure there are more factors that come into play past the simple
fact that warm humid air meeting up with a cooler surface is going to cause
condensation.
>
> --
> www.e-woodshop.net
> Last update: 2/20/07
> KarlC@ (the obvious)
>
>
"Morris Dovey" <[email protected]> wrote in message
news:[email protected]...
> Swingman wrote:
>
> | Yeah, we really do need a good isothermal shop compressor on the
> | market.
>
> I'd be happy to settle for an adiabatic discussion...
Would that theory be economically possible in this situation?
Too_Many_Tools wrote:
> On a related question... why are air dryers placed after the
> compressor and not before it?
Remember, "Willie, The Actor" Sullivan, a bank robber of some notarity.
When asked, "Willie, why do you rob banks?"
He answered, "Because that's where they keep the money."
Why put a dryer after the compressor, because that is where the water is.
Lew
"Lew Hodgett" <[email protected]> wrote in message
news:[email protected]...
> Tom Veatch wrote:
>
>> But the question was which one would contain the most water "vapor".
>> So state change has to be considered.
>
> Use the general energy equation to develop the specific equation for the
> conditions at hand.
>
> It all drops out to yield pounds is pounds. Vapor, liquid, gas, who cares,
> it is still weight (Mass if you prefer).
>
> The whole thread got started in answer to a question about where to locate
> a dryer in a compressed air system.
>
> My smart ass response was "Where the water is" or something close, thus on
> the high pressure, not the low pressure side of the compressor.
>
> I stand by that statement.
>
> Lew
Lew:
Previously: "Question: Which container contains the most pounds of water
vapor? End of discussion."
Now: "Vapor, liquid, gas, who cares, it is still weight"
I wonder what debaters and lawyers do when called on an error. They
probably don't just admit it. They redefine the question.
todd
Tom Veatch wrote:
> But the question was which one would contain the most water "vapor".
> So state change has to be considered.
Use the general energy equation to develop the specific equation for
the conditions at hand.
It all drops out to yield pounds is pounds. Vapor, liquid, gas, who
cares, it is still weight (Mass if you prefer).
The whole thread got started in answer to a question about where to
locate a dryer in a compressed air system.
My smart ass response was "Where the water is" or something close,
thus on the high pressure, not the low pressure side of the compressor.
I stand by that statement.
Lew
On Mon, 30 Apr 2007 01:58:02 GMT, Lew Hodgett
<[email protected]> wrote:
>Not relevant, pounds is pounds
But the question was which one would contain the most water "vapor".
So state change has to be considered.
On Sun, 29 Apr 2007 23:24:57 GMT, Lew Hodgett
<[email protected]> wrote:
>
>Which container contains the most pounds of water vapor?
>
An interesting question. The obvious answer is that the second one
would contain 7.67 times as much water vapor. (Assuming 15psi
atmospheric pressure, 115/15 = 7.67). But that ignores state change.
Since I don't have the appropriate property tables memorized, do not
have copies near to hand, and am not inclined to try and find any for
this academic exercise, I will make some assumptions.
The question states that the final temperature is 70F in both cases.
Therefore, the H2O vapor pressure is the same in both cases. But, we
know the partial pressure of the H2O vapor in the first container is
less than the 70F vapor pressure since the air is not saturated, being
at only 50% RH.
Assuming that, since the air in the first container is at 70F and 50%
RH, the partial pressure of the vapor in the first container is 50% of
the H2O 70F vapor pressure. In that case, a 7.67 compression ratio
will increase the partial pressure of the vapor in the second
container to well above the H2O 70F vapor pressure and condensation
will occur as the compressed air cools to the 70F ambient temperature.
Most of the water will condense out leaving the air in the second
container saturated at 100% RH with a H2O partial pressure equal to
the 70F vapor pressure. This is double the assumed partial pressure in
the first container. So, if the assumption above is correct, the
second container will contain twice the mass of water vapor as the
first container with the remainder of the water condensed as liquid.
And, your point about lawyers, debaters, and crap stuck to the walls
is...?
"Leon" wrote in message
>
> "Mike Marlow" wrote in message
> > Close but not quite. It's the act of compressing the air that causes
the
> > water build up in the tank.
>
> It's the heat generated during compression that causes condensation to
build
> up in the tank. Compress air with out changing the temperature and you
have
> no condensation during that process.
Yeah, we really do need a good isothermal shop compressor on the market.
... until then we'll have to live with Charles's Law. ;)
--
www.e-woodshop.net
Last update: 2/20/07
KarlC@ (the obvious)
Tom Veatch wrote:
> Oops, no time for that now, I just remembered that my wife wants some
> bookshelves built.
First thing debaters and lawyers learn to do is use the facts, if you
have them.
If you don't, keep throwing crap on the wall and hope some of it sticks.
Given air at 0 PSIG, 70F, and 50% relative humidity and two (2), 10
cubic foot containers.
Container #1 is filled with 0 PSIG air and sealed.
Container #2 is filled with the same air, except compressed to 100 PSIG.
Question:
Which container contains the most pounds of water vapor?
End of discussion.
Lew
In article <[email protected]>, Lew Hodgett <[email protected]> wrote:
>Buck Turgidson wrote:
>> Partially out of laziness, inertia, procrastination, and partially because I
>> use it several times a month, I leave my Porter Cable air compressor full.
>> Does this do longterm harm to the machine?
>
>Yes and no.
>
>Typically, the smaller the compressor, the less efficient, and the
>more condensate it generates.
How does the efficiency of the compressor make any difference?
--
Regards,
Doug Miller (alphageek at milmac dot com)
It's time to throw all their damned tea in the harbor again.
On Thu, 26 Apr 2007 19:50:21 -0400, "Buck Turgidson"
<[email protected]> wrote:
>Partially out of laziness, inertia, procrastination, and partially because I
>use it several times a month, I leave my Porter Cable air compressor full.
>Does this do longterm harm to the machine?
>
Maybe. When you drain it do you see water? Water (and oxygen) will
rust the inside of the tank.
I have a 2 HP, 20 gallon Craftsman compressor. I drain it about every five
years and never release the pressure at the end of the day.
I have been using it since 1973.
It was getting really hot when shingling so I changed the oil last fall.
Don't know if that helped--maybe I just slowed down a bit. :-)
-Doug
=================
"Buck Turgidson" <[email protected]> wrote in message
news:[email protected]...
> Partially out of laziness, inertia, procrastination, and partially because
> I use it several times a month, I leave my Porter Cable air compressor
> full. Does this do longterm harm to the machine?
>
In article <[email protected]>,
Buck Turgidson <[email protected]> wrote:
>Partially out of laziness, inertia, procrastination, and partially because I
>use it several times a month, I leave my Porter Cable air compressor full.
>Does this do longterm harm to the machine?
>
>
Drain any condensation out after each use but there is no reason why the tank
can't be left pressurized.
--
Make it as simple as possible, but no simpler.
Larry Wasserman - Baltimore Maryland - lwasserm(a)sdf. lonestar. org
In article <[email protected]>, <Tom Veatch> wrote:
>On Sun, 29 Apr 2007 05:11:22 GMT, Lew Hodgett
><[email protected]> wrote:
>
>>Too_Many_Tools wrote:
>>
<...snipped...>
>>Why put a dryer after the compressor, because that is where the water is.
>>
>>Lew
>
>
>If you dry the air going into the compressor, you'll have dry air in
>the storage tank. The compressor doesn't create water.
If the humidity could be removed before the air was compressed, that would
be true. However, the air dryer, working on compressed air at say
150psi, has 10 times as much air in contact with its cooling fins
as it would with air at atmospheric pressure. These units work more
or less as dehumidfiers. To operate on the input side of a compressor
would just be much less efficient.
--
Often wrong, never in doubt.
Larry Wasserman - Baltimore Maryland - lwasserm(a)sdf. lonestar. org
On Sun, 29 Apr 2007 11:20:49 -0500, "Leon"
<[email protected]> wrote:
>
><Tom Veatch> wrote in message
>news:[email protected]...
>> On Sun, 29 Apr 2007 05:11:22 GMT, Lew Hodgett
>> <[email protected]> wrote:
>
>>
>> If you dry the air going into the compressor, you'll have dry air in
>> the storage tank. The compressor doesn't create water.
>
>Consider this. Given the proper sized compressor the amount of air being
>dried on the "exhaust side" is much less than the air on the "in take" side.
>The dryer would have to dry much faster on the intake side. Typically with
>the correct sized compressor for the task at hand the exhaust side releases
>air at a smaller CFM than the intake side. Additionally, the compressor
>tank catches a majority of the water and lessens the work on the dryer.
>
Not to mention, as I previously stated, the state change physics of
water is such that higher pressure at a given temperature in a closed
container forces the equilibrium point toward more condensation.
Assuming the temperature of the air entering the dryer is the same in
either case, the pressure upstream of the compressor is less than it
is downstream of the tank. Therefore, a given drying process located
downstream of the tank operates at higher pressure and condenses more
water from a given mass of air than it would if that same process were
operating upstream of the compressor. Repeat, that's assuming the
process occurs at the same temperature in both cases.
My comment "... The compressor doesn't create water." was directed at
a previous post that stated "That's where the water is." It is
patently obvious that a given mass of air contains the same amount of
water entering the compressor as it does exiting the compressor and
entering the storage tank. The compressor might add oil vapor to the
air but it doesn't add water.
Technical discussion follows, skip it if you wish.
Atmospheric air is a mixture of gasses which includes some amount of
water vapor. The partial pressure of each gas in the mixture is
related to the total pressure in the same ratio as the number of
molecules of each gas is related to the total number of molecules in
the sample. For example, and using round numbers for convenience, if
the air contains 1% water vapor and is compressed to 100psi, the
partial pressure of the water is 1psi. At 200psi, the partial pressure
of the water is 2psi.
As the sample of gas is compressed, the partial pressure of the water
vapor increases in proportion to the increase in total pressure. At
any given temperature, water has a specific vapor pressure which
increases as the temperature increases. If the partial pressure of the
vapor is greater than the vapor pressure of the liquid at that
temperature, the rate of condensation will exceed the rate of
evaporation and the amount of vapor will decrease as the amount of
liquid increases. Net condensation will occur until the partial
pressure of the remaining vapor becomes equal to the vapor pressure of
the liquid. That is the equilibrium point where the rates of
condensation and evaporation are equal to each other.
From that point, isothermal compression causes net condensation and an
increase in the amount of liquid in the container. The reverse is true
for Isothermal expansion. Isobaric temperature increase drives net
evaporation. The amount of liquid reduces and the amount of vapor
increases until the partial pressure of the vapor again equals the
vapor pressure of the liquid. Likewise, isobaric temperature decrease
drives net condensation.
Everything that is correct in this thread follows from those basic
facts of physics.
Robatoy wrote:
> On Apr 27, 11:08 am, B A R R Y <[email protected]> wrote:
>> Swingman wrote:
>>
>>> I moved the drain plug to the end of a 3' length of air hose on my small
>>> vertical, where it is much more accessible.
>> That's exactly what I did.
>
> Sooo who did it first? Who am I 'really' stealing this from?
Swingman mentioned it first, but I don't know when he did it. I'll give
him credit for doing it first, 'cause he's older. <G>
I did it a few years ago. All you do is unscrew the drain valve, insert
a hose or threaded pipe w/ elbows, and screw the valve into the open
end, preferably in a more convenient location.
Must be bass players thinking alike...
Auto drain valves work in a similar manner. Each time the compressor
starts, it momentarily "burps" the water drain. There's really no
reason to completely drain the air to let out the water.
"Swingman" <[email protected]> wrote in message
news:[email protected]...
>
> 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.
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.
>
> 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
> KarlC@ (the obvious)
>
>
Tom Veatch wrote:
> On Thu, 26 Apr 2007 22:29:26 -0400, "Mortimer Schnerd, RN"
> <mschnerdatcarolina.rr.com> wrote:
>
>> Bottom line... it's probably better to dump the air when you're done... at
>> least for shop compressors.
>
>
> Or:
>
> http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=42221
>
> or something similar
Maximum pressure 100psi? Make it something similar...
--
Mortimer Schnerd, RN
mschnerdatcarolina.rr.com
"B A R R Y" <[email protected]> wrote in message
>
> What if it takes my compressor a week or two to drain down, so there's a
> sizable change I might use the energy? If I have half left, I use half as
> much enegery refilling the tank.
But does it take more energy to fill the second half than the first half?
In article <[email protected]>,
Doug <[email protected]> wrote:
> On Apr 26, 7:57 pm, lwhaley <[email protected]> wrote:
> > On Apr 26, 6:50 pm, "Buck Turgidson" <[email protected]> wrote:
> >
> > > Partially out of laziness, inertia, procrastination, and partially
> > > because I
> > > use it several times a month, I leave my Porter Cable air compressor
> > > full.
> > > Does this do longterm harm to the machine?
> >
> > no
>
> I've been led to believe that the compressed air will create moisture/
> condensation in the unit which obviously can do damage. I usually try
> to remember to bleed mine.
Porter Cable's instructions say to bleed it every day. I thought that
was a bit excessive, and left mine full for quite a while. The other
day, I emptied it, thinking some water might have built up. Indeed,
holding it up so the exhaust was at the bottom, a considerable amount of
water came out! Had to hold it over the sink. Perhaps I'll empty it like
that every few of weeks now.
--
Jedd Haas - Artist - New Orleans, LA
http://www.gallerytungsten.com
http://www.epsno.com
In article <[email protected]>, [email protected] wrote:
>You guys are making this too hard. It's just pV=nRT (ideal gas
>law).
So are you. :-)
>
>1. Compressor takes in outside air, which typically has water vapor
>in it, and packs it into the tank, thus raising the pressure.
And thus condensing the water vapor into liquid. End of story.
>
>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.
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)
It's time to throw all their damned tea in the harbor again.
Tom Veatch <firstname_lastname AT pixius dot net> wrote:
> >Bottom line... it's probably better to dump the air when you're
> >done... at least for shop compressors.
> Or:
> http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=42221
I bought one of these from HF, when I bought a new compressor
recently. I must have spent the better part of a day or so trying to
figure out a way to install this. The main problem I ran into is with
the air hose supplied and the compression fittings it uses.
Basically there weren't enough parts there to splice this device into
the system as they don't give you any additional compression fittings.
On my compressor, there's a solid copper line running between the
tank and the regulator. So I would need two more fittings to
rework things so that the automatic drain valve could be tee'd in
between the tank and the regulator.
I spent several hours trying to find more of those fittings locally,
but none of the hardware stores had them and HF itself does not
sell them. Perhaps a specialized industrial supply would have them,
but after spending a few hours trying to hunt stuff down, I gave
up and returned the device. The device itself probably works fine,
but you'd likely need to dig up some other type of way to splice
it into your system that uses some other type of fittings and hose.
It would be nice if they'd supply additional male and female
compression fittings with the device, even if that increased the
price of the device by a few bucks.
In the end, I found it's easy enough to just open the drain at the
bottom once a day and let it blow out the accumulated moisture.
--
If you want to reply via email, change the obvious words to numbers and
remove ".invalid".
B A R R Y <[email protected]> writes:
>Andy Dingley wrote:
>>
>> In general, no. However a machine that has a slow leak down somewhere
>> and is going to be switched off for long enough to empty itself is
>> usually best vented deliberately rather than being left to do it
>> inevitably itself (or just fix the leak!)
>
>Why is that?
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.)
In article <[email protected]>, "Mortimer Schnerd, RN" <mschnerdatcarolina.rr.com> wrote:
>Doug Miller wrote:
>>> 1. Compressor takes in outside air, which typically has water vapor
>>> in it, and packs it into the tank, thus raising the pressure.
>>
>> And thus condensing the water vapor into liquid. End of story.
>
>
>Only supersaturated air will condense upon compression. Normally, it won't
>happen.
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)
It's time to throw all their damned tea in the harbor again.
> Doug Miller wrote:
>> In article <[email protected]>, "Leon"
>> <[email protected]> wrote:
>>
>>
>>> You are on the right track.
>>> Actually the compressed air does not create the condensation. It is
>>> the heat generated from compressing the humid air that causes the
>>> condensation.
>>
>> Incorrect. It is *exactly* the compression that causes the condensation:
>> water that is vapor at ambient pressure can be condensed into liquid by
>> increasing the pressure.
So Doug, I suspect you believe it is the pressure from "your firm grip" on
a glass of ice water that causes the warm humid air surrounding the glass to
cause condensation on the cool side of the glass.
On Fri, 27 Apr 2007 16:31:35 GMT, "CW" <[email protected]> wrote:
>Doug's never wrong. Just ask him, he'll tell you.
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.
"Robatoy" wrote in message
> I have a headache now.... what walls?
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
KarlC@ (the obvious)
On Sun, 29 Apr 2007 17:16:20 -0400, "Edwin Pawlowski" <[email protected]>
wrote:
>
>That easy. Now try to explain where everything wrong in this thread came
>from. C'mon, I dare ya!
>
Oops, no time for that now, I just remembered that my wife wants some
bookshelves built.
I will say in response to the OP, if I can remember what the OP asked,
that there is no structural reason to completely depressurize the tank
after each use, and there is a theoretical reason to leave the tank
pressurized. Deep cyclic loading, i.e., full pressurization followed
by complete depressurization, induces fatigue damage to the vessel. In
a well designed and constructed tank, that damage is insignificant at
the pressures shop compressors usually develop and can be ignored. On
the other hand, it does no harm to the tank to leave it pressurized.
Static loading doesn't cause metal fatigue. If you want to avoid
cycling due to minor leakage and long periods of disuse, simply turn
off the compressor when you're done.
Draining condensation is another matter. That should be done
regularly, either manually or with an auto drain valve, whether or not
the tank is left pressurized.
Now, I hear those bookshelves calling!
On Fri, 27 Apr 2007 05:25:15 -0400, "Mortimer Schnerd, RN"
<mschnerdatcarolina.rr.com> wrote:
>
>Maximum pressure 100psi? Make it something similar...
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.
"Swingman" <[email protected]> wrote in message
news:[email protected]...
>
> Yeah, we really do need a good isothermal shop compressor on the market.
>
> ... until then we'll have to live with Charles's Law. ;)
Perhaps an electric blanket on the outside of the compressor. Then we could
worry about what to do with the condensation on the outside of the tank.
;~)
Larry W wrote:
> Drain any condensation out after each use but there is no reason why the tank
> can't be left pressurized.
You'll have to go back and drain it again after the tank cools down. There will
be more condensation as the cooler air can't hold as much moisture in its
gaseous state.
And as others have pointed out, there's draining condensation and there's
draining the tank completely. If you'll go back to drain the condensation after
the tank is cooled, there's no reason why you couldn't leave it pressurized. If
you're not willing to do that, you may well end up with rust eating the bottom
of your tank out over time.
--
Mortimer Schnerd, RN
mschnerdatcarolina.rr.com
"scouter3" <[email protected]> wrote in message
news:[email protected]...
> 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" <[email protected]> wrote in message
> news:[email protected]...
>> Partially out of laziness, inertia, procrastination, and partially
>> because I use it several times a month, I leave my Porter Cable air
>> compressor full. Does this do longterm harm to the machine?
>>
>
>
"Swingman" <[email protected]> wrote in message
> RCH's are being unnecessarily split on this subject ... it matters not
> that
> you blame death by gunshot on the gun, the shooter, or the trauma from the
> bullet, you're still dead.
Yes, but it is either split hairs this morning or go out and clean up the
yard.