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Tuesday, June 4, 2013

Here is your warning of the nerdy DIY situation to follow this paragraph.  
You see, I love learning and if there is a problem with something I do regularly, I will try to fix that problem instead of dealing with it in continual frustration.  This applies to my relationships with people and also in the more physically literal sense.  What does that mean?  Get ready for a photo journey.  This is nerdy engineering-type stuff, you have been warned.

I use an HVLP gun for wood/furniture finishing on a regular basis.  
That would be this:
It sprays paint...Which I hope you were able to deduce on your own accord without me telling you that.

This is an air compressor used to compress the air you need in order to spray the paint out of the HVLP gun:
Yes, the air compressor is dirty.  It lives outside and outside is notoriously dirty if you are unaware of that little fact (Hey, you learned something. No?  OK.).

My problem with using my gun to spray a proper finish in the warmer months is a little occurrence we call "humidity".  The more humid the air is outside, the more likely you are to get water in the airlines that go to your paint gun.  Putting a water catch in the air line does nothing to help because of condensation.

When the air compressor starts pulling air from outside to compress it into the large tank below it, the outside air is full of moisture (of course).  The actual compressor assembly is similar in operation to a gasoline engine and the air that passes through it can get as hot as 230*F.  The problem is that the compressor pumps this very hot air into a sixty-gallon tank directly below it that is generally under 70*F.  When hot air meets substantially cooler air, you get condensation.  This is the same principle behind the making of liquor in a distillery, if you have ever seen how that works.  Some of this condensation falls to the bottom of the compressor tank, but most of it just floats around and comes out of the air lines and into whatever tool you are using at the moment.

In my case, the condensation was coming out of my HVLP gun and since water does not mix with lacquer or oil-based paints, the finish would have water drops (cat eyes) in it or solidified paint would come out the end of the gun, ruining the finish on the piece I was working on enough that I would have to start over.

I had to do something and took to the internet to find an air dryer system which would remove the condensation, but they are very expensive.  But I did find a guy who posted a write-up about building an air-dryer from scratch for a small, portable air compressor and figured I could design something similar to use on a commercial air compressor at the shop.  

I will give credit where such is due when I find that write-up again.  I cannot find it for the life of me right now.

The trick to removing the water from compressed air is to catch it all before it gets into the air tank.  So, the compressed air needs to be free of water and clean before it makes it into the air line.

I used this:
That is a condenser coil from an air conditioning unit.  I was going to take a video of how I acquired it, but the way I went about that was illegal.  It involved an old air conditioner at the edge of a forest, some tin snips, and copious amounts of R134a going into the atmosphere.  But I did not document that event with pictures, so it may or may not have happened (but it did).  If you do not know what a condenser coil is, it is a long piece of copper tubing run back and forth in a grid, similar to a car's radiator.

My uncle and I made those brackets out of aluminum:

The idea behind using a condenser coil is to unhook the air compressor itself from the air tank below it and run the hot air out of the compressor, through the condenser coil in order to cool it off before it reaches the tank.

We bought some stuff to make that happen:

The air compressor lives in a little roofed area outside, so I built a mount out of 2x4's to attach the condenser coil to:

And did some plumbing with my uncles to get all of that sorted:
If you look at the original picture of the air compressor I posted, there was a single copper pipe going from the compressor head, into the tank.  That is how the 230*F air hit the 70*F air and created the water.  The rearward piece of copper tubing goes from the head to the top of the condenser coil. 
You can see it here:

So, the hot air comes out of the compressor head, goes into a copper pipe that is attached to the top of the condenser.  When the air comes out the bottom of the condenser, the water has separated from the air, so if that is going back into the air tank, the water is still in the system, right? Nope.

My uncle made the little box you see on the right:
Yes, he made it.  My uncle is a welder and built that small air tank out of raw steel and then threaded a hole in the top for a pressure gauge, threaded another hole towards the bottom face for the separated air/water mix to enter when it leaves the condenser, threaded another hole towards the top of the face for cool air to leave the small tank and go into the big tank, and threaded one more hole at the bottom for a petcock.  

So, the condensed air/water goes into the bottom of that small tank and all of the heavy water falls to the bottom.   The cool, clean air rises upward to the other copper line that then pumps it into the main, sixty gallon tank, free of water and completely cooled down.  Does that make sense?  

After pressurizing the system, nothing leaked and the compressor was running much cooler and quieter.  After a few cycles, I drained the water from the small black tank (that's what the petcock at the bottom is for) and about a quarter cup of water came out.  Some water was also still making it into the main tank, so, today, my uncle and I put a fan behind the condenser:
I wired it directly into the pressure switch on the air compressor so it will turn on automatically only when the compressor fires off to re-pressurize the system (which is the only time it needs to).  
After installing the high-powered fan and letting the system cycle on twice, there is not a drop of water in the main air tank and I drained about half a cup of water out of the small, black catch tank.  Most importantly, there is no water in the air line that feeds my HVLP gun.

My dad and uncles helped with my idea immensely and even though there were a few moments of them saying "This had better work." they all put a huge effort into it.  I am a car guy, so I understand the method and science behind it, but when it comes to flaring copper pipe and that sort of thing, I could not have done it without their help (and Cecil's welding skills.  I suck majorly at welding).  

Why would I come up with this idea when you can buy a kit right off the shelf and just install it?  Those kits start at around $1000 and go up from there.  The materials in this build cost less than $100.  A little time, a little learning, and a lot of family bonding (mostly bickering and uncertainty) and you can really surprise yourself with what can be accomplished.  And if it did not work, we could always make it into a still for moonshine, right?

Do not let anyone tell you that you are unintelligent for any reason, because if you run with an idea and have great people backing you up, anything is possible.  

Even fabricating a potentially deadly bomb out of an air compressor and some copper...



Grace and Peace,
-Drew

Facebook: http://www.facebook.com/drew.silvers
YouTube: http://www.youtube.com/drewcoustic
Email: drewcoustic@gmail.com

The lyrics in the title of this blog are from this song:

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