Compressed Air Dryer

Hello Everyone,
I am having problems with moisture in my compressed air supply. I would be
very interested in speaking to anyone who has constructed a compressed air
dryer. Links to any relevant web site would also be appreciated.
Bob Segrest
Reply to
Bob Segrest
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I have often wondered if a flow-through tank in the shop 'fridge would work. I guess it would depend on the flow rate.
Vaughn
Reply to
Vaughn Simon
Yes, it absolutely will work. A loose coil of copper tube will work even better.
I got a commercial refrigerated dryer that needed a new starting relay and a little Freon, and it works really well. I get NO water at all when paint spraying, or when running an air bearing spindle motor that requires dry air. The manufacturer (Zeks) has a web site with some pictures and info on what is in their patented design.
Jon
Reply to
Jon Elson
I thought about the tube idea, but how would you collect the water that you condense out of the compressed air?
Vaughn
Reply to
Vaughn Simon
A coalescing-type filter would do. The Zeks site might give some ideas on how to make the separator. Mostly, they have a big bunch of aluminum discs that have been punched to make "fingers", or something along that line, in a chamber that allows the air to swirl around a bit as it flows in the side and out the top. The water comes out the bottom.
Jon
Reply to
Jon Elson
Here's a simple one that I built. It hangs in a bucket of water, added ice helps. The fitting at the bottom is a drain for the condensate. Not perfect, but it works pretty good.
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Gary Brady
Reply to
Gary Brady
Industrial air dryers are designed with energy conservation in mind and use the cold, dry air exiting the cooling heat exchanger to precool the air coming from the compressor. You could probably make up a couple of"coil in coil" heat exchangers and use the condensing equipment from an old fridge to make up the dryer. Air flow should be generally downward with a tee at the bottom of the coil. A short length of pipe would lead to a float trap which would allow water to drip out but not air. It wouldn't be difficult to construct if you have some refrigeration experience and the basic refrigeration tools like a vac pump and a charging set.
Tom
Reply to
Tom Miller
You need a phase-changing substance in contact with the heat exchanger, like the boiling Freon in a commercial unit, or melting ice in a improvised design.
So no, cool air in a refrigerator doesn't work effectively, because it can't transfer much heat.
Reply to
Richard J Kinch
I've never been in any working enviornment that required air dryers AFAIK. A well-plumbed air system will generally deliver water-free air. I spent some years working in autobody shops and manufacturing plants where a lot of pneumatic cylinders were used in production equipment, and water wasn't a problem in any of them. That might not be much of a testimonial, with regards to plasma cutters or other completely dry air requirements though.
A bad setup example would be to use an undersized capacity air compressor running excessively, located across the shop with an air hose connected to it, running across a cool shop floor (where the moisture is obviously going to condense, and travel to the outlet).
A good system is made up of many properly placed components, but maybe most importantly having long metal pipe runs to the remote locations/user access, with the metal piping sloped back toward the receiver of the compressor, so the moisture in the air has a chance of condensing as the piping cools and the sloped runs can keep it traveling back to the air receiver. Adequate placement of drip legs and drains, along with installing the drops so that they take air from the top side of the sloped system piping runs, then having water and oil separator/filters at the outlet points, will all contribute to an almost trouble-free air supply.
WB .............
Reply to
Wild Bill
You are indeed correct.
But..on the other hand..in a manufacturing environment, which is cheaper..ripping out the exisiting system, or adding a chiller?
Gunner
"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.
Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner
Reply to
Gunner
Well, I can't think of a practical reason for removing an existing air delivery system.. the scap value wouldn't do much to offset the costs of removal.
Retrofitting a proper air system would be very expensive in many environments, but in a small shop it would be the most cost effective/practical approach to reduce or eliminate most moisture problems (but not guarantee absolutely dry air).
If a commercial chiller is needed, one should consider the additional energy costs required when it's in use. In industry, that's easy.. just reduce the employee benefits.
Un-common sense (as it is not so common anymore) should deter someone from installing a problematic system to begin with, and throwing technology and money at a mistake doesn't actually correct the problem. A condition that at best, can only be described as "better than it was" isn't much of an accomplishment.
I haven't torn one apart to see what's involved, but I would think that a refrigerated water cooler would be a good machine to adapt with a liquid-filled heat exchanger, to use for drying air. In addition to fabricating the heat exchanger, it would also need a means of draining off the water.
WB ..............
Reply to
Wild Bill
I found a cheap and very effective method after ruining a nice lacquer paint job on my brother's car.
Go to a HVAC shop and ask for a used but good AC evaporator, an "A" type. Just solder copper fittings on it and place between the compressor and your air/water separator. Works *great*! In this case I would actually plumb it so the condensant will run towards the separator/filter.
John
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Reply to
John Flanagan
Sounds like a great idea... I will give it a try.
i
Reply to
Ignoramus9179
I use it without a fan but if you've got a lot of water or use it for extended run times you might add a fan to help cooling. Even though the compressor tank gets hot I've never had the outlet of the evaporator get even noticably warm.
I've never had water in the line since I installed the coil. I actually scavanged it from my father who was having his AC replaced in his home.
John
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Reply to
John Flanagan
I think that I will use a fan. I have two decent fans. I would like to buy some evaporator from ebay actually, as calling these HVAC guys is usually a pain. Would a car evaporator be good?
That's very nice. I threw away a window A/C last year, perhaps I could have salvaged that coil.
i
Reply to
Ignoramus9179
I'd say you need something big bore, the house AC coil I got was 1/2" ID tubing. These coils I don't think are that expensive new ($120???) but I don't think it would be a problem calling the HVAC guys. I'm sure they have lots of them they'd like to get rid of one way or another.
I've posted a photo of the setup I use. Note the plumbing is so the coil drains towards the separator. I have an automatic dump valve in the bowl of the separator so I never have to deal with draining it. Now all I need is a valve for the tank itself!
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John
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Reply to
John Flanagan
Very nice, I am impressed. I am sick of moisture in the compressed air, myself.
i
Reply to
Ignoramus9179
I made one once:
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- GWE
John Flanagan wrote:
Reply to
Grant Erwin
I have been running a $300 HF dryer for ~year and a half, no worries
Reply to
yourname
Another way is to cool the air coming out of the compressor before it gets to the tank. That way you don't even have to worry about draining the tank. If you'll look at my setup here you can see what I'm talking about.
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As you can see I put the cooling lines between the compressor and the tank. It then enters into a cyclone tank which separates the water from the air before going up into the tank. I put the check valve to the tank after the separator tank so I can use a solenoid valve in the bottom of the separator tank to do the unloading. This in effect drains the separator every time the compressor shuts off.
I've yet to get any real water out of the drain valve of the tank in 1 1/2 years of running. I did get a little bit of mist once but that's it. The piping into the shop is 1 1/4" and I've got a main drop leg which all my current outlets get there air at. So far I might of gotten a couple table spoons of water out of this leg.
It would work even better with a good cooling coil but this was easy and fairly cheap for me at the time. A air conditioner condenser coil would work great for this since they're made for the high pressure side of a system and have a fan built in. The evaporator coil like you've got is good also and is smaller.
Wayne Cook Shamrock, TX
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Reply to
Wayne Cook

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