Secret to moisture removal from compressed air:

Cool the air to let the moisture condense out!

This can be accomplished in several ways. Commercial air compressors use a refrigerated chiller to dehumidify the air. It is a basic rule of Physics that when you compress a gas it heats up, which is why the outlet and head of the compressor get so hot. When a gas expands it cools down which is why that air nozzle streams with moisture both from the compressed air and also from the ambient air just like that cold beer gets wet on the outside.

We can use these properties to our advantage in an air system. No not the beer!

Replace that short little piece of copper tube coming out of the compressor into the tank with a nice long loop or several loops of copper tubing. You guys that run a "still" know how to do this (LOL). This loop of tubing radiates more heat than any other part of the system. On large commercial compressors they use finned tubing for this purpose. You typically see this tube covered with dust and grease in a shop because they don't do preventative maintenance. When the air leaves this tube and enters the main tank it expands and cools. This is the first point where we want to see the moisture condense out of the air. Some commercial compressors have a moisture trap on the line at this point which is nothing more than a piece of metal cooled by this incoming air blast and conduction back to the tank walls so that the air flows over it forming drops of water just like on the outside of that beer.

Use a large main tank on your compressor, this gives the air extra time to cool and allows the moisture to condense out on the inside of the air tank walls. Remember to drain the tank! See the other posts about putting a reservoir pipe on the bottom of the tank.

Use a coalescing filter on the outlet of the tank. These are special filters that use the properties of gas expansion to cool the air and condense the moisture out of the air. You have to drain these too unless you get an auto drain type.

Keep your hoses clean, dry, and oil free. See the inline lubricator post.

If this still is not enough...

Use a secondary surge tank with an inlet and outlet at different points. Restrict the inlet fitting slightly to get another pressure drop at the inlet just like the main tank so you condense more moisture. Put another coalescing filter on the surge tank outlet.

Run a loop into your shop adult beverage storage device and mount another coalescing filter on the outside on the outlet side of the loop. Remember to slant the line down to the filter to provide drainage.

Try getting your compressor inlet above water level.

Happy Dry Air!

-Eric

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over!

 

My father applied the same principal as above. He took 50ft of 1/2" copper tubing to make a coil. He made a rack to attach to the handle area of his Craftsman compressor to hold the coil. The "high end" of the coil is tied to the pump, the low end to the tank. Just before the copper tubing goes into the tank, he has a filter to take out the dirt, oil, and water. The globe on the filter leaks the water out because it is broke, but doesn't lose any air. Since he built this set up, he drained the tank once and NOTHING came out . This set up takes the water out of paint spaying and seems to preserve the life of air tools (which get lubed regularly).

Remeber, all you need is the tubing, fittings, filter, and rack. No water and you don't have that little piece of tubing that gets almost to the molten metal stage.

I'm doing this to my new compressor this weekend.

Chris
72 F-100 stepside
About to be 289 V-8, auto, power steering, disc brakes