plasma cutter air dryer

Dry Air Systems


This thing works wonders for us.

Reply to
ben carter
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You can apparently get a good effect in drying air by passing the air through a helical coil of copper tube immersed in a bucket of ice-and-water. Water will condense out of air at low temperature and remain in lowest region of pipe at that point, giving dry air emerging out of the helix.

This hint given to my by pneumatics shop I use. Apparently a customer does that frequently and is very happy. Would be useful if occasionally did moisture-affect process. Would be a bit of a pain to use all the time. I gather a lot of commercial drying systems for compressed air are an inbuilt refrigeration system.

Ice idea - would be even bigger effect if threw salt into bucket, as that would lower temperature even more, to -10C or less.

Richard Smith

ben carter wrote:

Reply to

It would get more water out, but that could backfire, due to frost buildup inside the coil. With icewater, the condensate can run downhill to a trap you provide for it at the bottom. If you were building the system for semi-constant use, you'd want a drain leg hanging off the bottom of the bucket (and unless you had a lot of free ice, you'd want to pick up an icechest or the like for use as the "bucket"). Could be set up relatively low-hassle, pretty good for a home shop where a full-on airdryer is far too costly.

You could also build something involving a refrigerator (rather than ice), if there's one leaving the premises because it's not the right color, rather than becasue it does not work well.

Reply to

Pure snake-oil.

So you take air, and blow it down a narrow pipe part-full of water. Then you expect the air to be _drier_ ?

There are several problems with this idea. One is simply the thermodynamics of it - too much air is flowing over too little surface at too high a temperature to condense effectively.

Secondly, there's no separation of condensate and flow. You need to do this, otherwise you simply shift the equilibrium a little. Your air might be drier, but it won't be dry.

If you want to dry air, do it the way that air driers always do it - drop the pressure by sudden expansion, and provide mechanical (spin or gravity) separation to take the condensate away afterwards.

A sealed drier can't possibly work either, unless you operate some sort of batch blow-down process.

Always remember to sprinkle the elephant-preventive dust when travelling by bus.

Forget it - still not cold enough. If you really want to do this (it's a common thing in vacuum systems) then use dry ice and a large surface baffle, like a louvred blind.

Reply to
Andy Dingley

The coiled tube in a bucket is not "pure snake-oil" but close. A refrigerant dryer has a regenerative heat exchanger that takes warm wet high pressure air and cools it. A refrigerator then finishes cooling the air to about 35 F (2 C) where the water that has condensed falls out and is remove via a drain. The cold saturated air now goes back through the regenerative heat exchanger to warm itself up and cool down the incoming air. The exiting air now has a dew point that is well below freezing, and will not condense in your torch, paint gun, etc. In your coil in a bucket system it will work if you need only a small amount of air for a very short time. As soon as the tubing fills with water it will carry over and go down the line as a slug of water. Also as the air coming out of the bucket is at about 32 F it may cool enough by expansion and dump what water it is carrying.

Reply to
Mike Swift

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