You guys are making this too hard. It's just pV=nRT (ideal gas law).
Kevin
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.
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 Air withdrawn from the tank as the tools are used contains less water vapor than the air that was taken in, because some of the vapor remains behind in the tank as liquid.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.
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.
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.
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.
| 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 c*ck 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
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.
That's exactly what I did.
Why is that?
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 c*ck 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.
Ditto.
Thanks
Sooo who did it first? Who am I 'really' stealing this from?
Stay tuned. Film at 11.
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.
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.
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 c*ck, 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 c*ck. It will be at eye-height and the air pressure will push the water up the line to an awaiting plastic bottle.
Oh noes...... two solos, duet style?
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.
We're going to get together and play "Big Bottom".
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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