DIY compressed air dryer
Now that we in the southern hemisphere (Oz) are getting into the winter cycle it's become apparent that the air dryer/filter on my air compressor isn't taking out as much moisture vapour as I would like, and running my new air needle gun sees it spewing out quite a bit of moisture from the exhaust.
So I was wondering if there's a cheap and easy way to trap the moisture.
I have a separate schrader dryer on the compressor, but it looks like I need more for this sort of continuous air flow.
Anyone made their own?
I was wondering if a car air conditioner condensor in the air line would be helpful to get the dew point down and get the trap working better.
The aftercooler/ heat exchangers i've used are basically a long coiled tube with fins and a fan above a separating trap. If yours will handle the pressure, it will probably work.
Aftercoolers takes about 75% of the moisture out, refrigerated dryers take out the rest to below dew point so as things warm back up in the lines, the small amount of water is in gasseous suspension going through things.
If your dryer is mounted right at the compressor outlet, it's not effective; the air coming off the compressor is hot, & capable of holding the water in a gaseous state, thus it can't be 'separated' from the airflow. I have 'southern-engineered' a separator from an old ice chest & a coil of copper tubing, with my water separator/dryer on the downstream side. I only ice it down when I'm painting something. It actually works ok with just water in the box for the small amount of air I use in my shop. Regarding the air conditioner condenser, I know a guy who did the very thing, mounted a box fan to it. The key is getting the stuff some distance from the compressor itself.
This topic has been brought up before. Try the search feature.
I constructed my own "air dryer," which is really just the overhead air distribution header for my garage, after looking at a link in a previous discussion. The link was to one of the major air compressor/compressed air equipment suppliers.
A simple description of the set-up involves (after the vertical run from the compressor to the ceiling) just slanting the air lines a bit so the water that condenses in the lines flows with the air flow direction until it hits a drain leg. Using tees or crosses, your tap for the air comes off the top vertical leg, water drains into the bottom vertical leg.
I used 1-inch copper water line (sweat fittings and threaded copper pipe). Works great. Never had a drop of moisture in my bead blasting cabinet.
I used a small transmission cooler right after the pump. It helped so the filter could catch liquid water. BTW is a compressor supposed to pull air over the pump or push it. My compressor was bought used and I am not sure if they connencted the motor right. Since it is splash lube not sure if it matters or not.
My understanding is that the correct drive direction draws air past the cylinder (s). I have run them the other way and it doesn't seem to make them run much hotter.
My original thought was to mount an air con condensor (they run at 160 psi) on the drive belt enclosure and use the fan to push air trough it, but then I gave that idea away as the air flow would be warm.
Then I talked to a guy at the engineering shop and he suggested running the air line into a long length of steel water pipe with a drain off and then into the separator.
So that's what I'm going to do. I have plenty of 1/2 - 3/4" water pipe and fittings, so I will run it vertically up to the roof of the garage and back down (U shaped) and put a tap on the bottom of each column to drain them.
I will then drill and tap a connector about a quarter the way up each pipe for inlet and outlet. That will give me about 30 feet of pipe for cooling with collector space at the bottom.
The bridge at the top of the pipes will be restricted down so that I get a pressure differential there as well as at the inlet fitting - so each column should condense water out.
The separator is too close at present. I will leave it on the tank but run a return line back to it from the pipe fixture with snap on connectors.
I recon it should work OK.
Today's project :-)
An R134a car air conditioner condensor can run over 350 PSI when it's hot out. Most car A/C relief valves are set at >450 PSI. You will have plenty of pressure margin.
Originally Posted by nearnexus
-I live in a desert where the humidity is usually well less than 50%---so water hasn't been much of an issue for me----although I used to have to drain my water traps daily.
-I port & polish cylinder heads using air die grinders----and that means my air compressor works a lot and builds a lot of heat so I wanted a way to make my compressor more efficient so I did the story in this link.
-Having had this supercharger in use now for about two years----along with the cooling fans I mentioned----I can say that water is now virtually a none issue.
-My belief is that if you can keep the air from getting super hot you are much more likely to NOT get the water separating out of the air.
-Maybe my story might give you some things to think about and help you to analyze why you are getting the water.
I have mentioned this before, but I saw a clever intercooler arrangement in a shop. the air line from the intercooler went into a 55 gallon drum of water in a loft, the drum had a float valve in it, and fed the flush toilets, so every time a toilet flushed it brought som cool water into the drum, this would work especially well if you had women working in your shop, they love to flush, and flush, all day long.
The drum just had a coil of 1/2 plastic hose stuffed in the bottom, nothing fancy. I bought the compressor, so I know this in detail. The air line was tapped into the orginal intercooler, so the air was first cooled there, then into the drum. However they also should had run the air thru the drum between the compressor and the tank.
Built the air dryer
Well I got the air dryer together after cutting a few threads in some 1/2 - 1 inch galv water pipe.
It's basically as I mentioned earlier. I'm pushing the air from the tank through two vertical ten foot lengths of steel house hold water pipe joined at the top, with a riser pipe comming of the middle of the second pipe for the outlet. It's a big "U" shaped length of pipe basically.
I will post a photo of it when I get the last few brackets done.
It works fantastically well.
Where as the air hammer was spewing out streams of moisture from the exhaust ports, there is now nothing. No sign of moisture at all. Quite amazing.
Incredible what a longish length of cold steel pipe with a couple of pressure differential points in it will do.
So there you go. Dead simple.
I have used a domestic air conditioner coil as the interstage coolers of a 3 stage compressor, they worked great @ 60 and 400 psi then I used a domestic refrigerator coil as the final stage cooler @ 2300 psi, water traps between each stage 22 CFM FAD. R22 AC coils can handle over 400 psi as the over pressure cut off is usually set somewhere around this pressure.
A cooler between the compressor and tank removes most of the moisture, I use a brazed plate heat exchanger but I have cold water available, when doing critical stuff I turn on a refrigerated dryer but most of the time it is unnecessary.
Here's the simple air cooler/dryer as described previously.
The air from compressor goes into left pipe and returns from the riser on the right pipe back to the separator/regulator on the compressor.
The left pipe has a 5 foot long perforated metal strip in it to aid cooling and condensation.
Both pipes are about ten foot high and joined at the top with air hose.
Each pipe has a drain at the bottom.
Works well - totally fixed the moisture problem.
The picture didn't make it so try it again.
The link below gives a larger view.