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-   -   inexpensive filter/dryer (http://www.hotrodders.com/forum/inexpensive-filter-dryer-190713.html)

vintagecar 01-13-2011 10:27 PM

inexpensive filter/dryer
 
I had started an air line thread and it got down to discussing what sort desiccant dryer/filter I could use on a budget, it was suggested to start a new thread specifically on that- can't disagree.

The Devilbiss QC3 was suggested, and found it around $150 online. Are there other suggestions that might be a bit cheaper/better or is that sort of the one for light painting use.

35WINDOW 01-14-2011 08:04 AM

I use one of these, plus good Water Traps, Air Filters and an in-line dessicant. My Air Lines are about 30' from my Compressor with lots of drops and rises-


http://www.sjdiscounttools.com/jlmm60.html


http://www.harborfreight.com/media/c...image_4209.jpg

DanielC 01-14-2011 09:09 AM

This is about as cheap as you can get.
I have an extra tank, the same size as the tank on my 3 HP compressor, 20 gallon.
I run a hose from the regulated out on the compressor, to a water trap/ filter mounted on the second tank. The air inlet on the second tank is on the top, pointing down, in the center. The air out to the paint gun is on one end of the second tank. I have a pressure gauge on the gun, that has a built in restrictor.

I use a $79.00 HVLP gun, from Home Depot.

This is how I set it up for painting. Regulate the air out of the compressor down to about 40 PSI, and put the second tank close to what I am painting. Adjust the pressure at the gun down to what I want, with the trigger pulled.

This setup allows me to paint more or less continuously, with a HVLP gun, and an old 3 hp Craftsman compressor. The compressor cycles on and off when I am painting, and spends more time off, rather than on.

This is my theory on why it works. We all know the air inside the compressor tank is hot, and has (non condensed) water vapor in it. When the hot air goes through the regulator, the pressure is reduced, and if you paid attention in high school chemistry, you know that allows the volume to increase, and the temperature to drop. The drop in pressure, and temperature causes the water vapor to condense in the air hose going to the second tank. The air also continues to cool a little more in that hose. The water trap can then catch the condensed water, and hold it. Any water that gets past the water trap, simply falls into the bottom of the second 20 gallon. Because the volume inside the second tank so large, compared to the air hose, there is no way any water in the second tank could be blown up to the outlet of that tank. The water just stays in the second tank.

It has been suggested that I move the regulator to after the second tank, because I would have more high pressure compressed air. Although that is true, the air in the second tank would be hotter, and still be holding on to the water vapor. The air has to cool for the water vapor to condense, and be trapped. The air expansion at the compressor mounted regulator cools the air, and a lot of the water vapor then condenses out before it gets to the filter/ water trap, and into the second tank.

001mustang 01-14-2011 10:54 AM

+1 .

Some how DanielC stayed awake that day in chemistry class.

oldred 01-14-2011 11:18 AM

That system with the second tank is what we used to call a "Thump tank" and it does indeed work quite well. Another common setup I have seen uses a large pipe set vertically or, as was often done, a large drive shaft was used. This does work quite well and does for the reasons described just keep the "Thump tank" on regulated pressure.


BTW shouldn't be Physics class?

DanielC 01-14-2011 11:26 AM

Gas laws = chemistry, or maybe physics, I do not know. I remember in the chemistry class I took in my first term of community college, on one page of the textbook, there was a diagram of the pressures inside the cylinder, of an engine, during the four stroke cycle.
By the way, knowing Algebra comes in real handy when you are figuring out the compression ratios of an engine.

matts37chev 01-14-2011 11:39 AM

we are talking about getting water out of air
so that would be - oceanography :P :P

001mustang 01-14-2011 11:43 AM

Quote:

Originally Posted by oldred
That system with the second tank is what we used to call a "Thump tank" and it does indeed work quite well. Another common setup I have seen uses a large pipe set vertically or, as was often done, a large drive shaft was used. This does work quite well and does for the reasons described just keep the "Thump tank" on regulated pressure.

Interesting. That drive shaft or large pipe "Thump tank" would be easy to wall mount and get out of the way.

DanielC 01-14-2011 11:59 AM

"we are talking about getting water out of air
so that would be - oceanography "

No, that is meteorology. The weather.

001mustang 01-14-2011 12:14 PM

Good point.

Maybe we should be surfing the Weather Chanel forum in our quest to remove water from air lines.

oldred 01-14-2011 12:42 PM

Maybe I came across the wrong way about the physics, I was just joking but after going back and re-reading that I can see it does not look that way, sorry about that. :spank:

001mustang 01-14-2011 01:45 PM

Are you saying I fell asleep in chemistry class, physics, oceanography, meterology...or ....all of the above.

matts37chev 01-14-2011 01:46 PM

Quote:

Originally Posted by 001mustang
Are you saying I fell asleep in chemistry class, physics, oceanography, meterology...or ....all of the above.

just home ec. :P

DanielC 01-14-2011 02:35 PM

Oldred, I took absolutely no offense. It is all interrelated.

I hope maybe some young, still in school person reads this, and maybe figures out that some of these educational opportunities we give them can actually apply to being a gearhead.

matts37chev 01-14-2011 02:41 PM

3 Attachment(s)
i dont do a ton of painting, but i do some and have never had a problem.

all i have is a water separator at the compressor with over sized pipe on both sides of it, so the air slows down as it goes through it.

then in to 1/2 pipe that goes into a tee (with a drain in the bottom) up and across the top of the garage and back down to drain/outlets.

from there it goes up to another water separator/filter and reel.

again, i have never had a problem, but i am going to get some disposable dryer/filters for use at the gun for cheap insurance :thumbup:


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