I haven't read the article, but I have quite a bit of experience
installing copper air systems. My personal system is 3/4" and over
200 ft of tubing (shop is 38x26). I've read the advice from TP Tools
that says you should only use black iron but respectfully disagree.
Their concern is that a soldered joint might separate under pressure -
the soldered surface area is over 1" sq. I have yet to have one come
apart at 125 or 175 psi and I've been running them for years. Note:
Use a flexible connection between any air system and the compressor to
isolate compressor vibration from the piping system.

When air is compressed the temperature rises (aka PV=nRT) and so does
the amount of entrained water vapor. The purpose of a long run
between the compressor and the outlet is to provide air travel
distance allowing the heated air to cool. As the air cools the water
vapor condenses. Copper is an excellent conductor and is perfect for
this purpose. The piping should be running slightly uphill away from
the compressor allowing the water to run back away from the outlet.
Usually drops are provided in the piping system to catch water with
valves at the bottom to drain the system. Think of the anti-water
hammer risers in your home, but in reverse - pointing down instead of
up. The system I installed in my shop has 7 such drains plumbed out
through the walls so I can just crack the valves and drain each
collection point.

The copper coil you reference is probably in the system to add cooling
distance in a relatively small amount of space. A coil can also be
placed inside a refrigerator or in an ice chest to provide a larger
temperature differential to speed condensation. This is also how
commercial air drying systems work - they are heat exchangers removing
the heat from the high pressure compressed air side and dumping it
into the environment. A coil also works well to "sling" the water out
of the air stream as it condenses - takes advantage of angular
velocity.

Any air system should have a water separator and a filter at the end
of the stream. No matter the pipe selected you will get particles in
the compressed air that can contaminate your air tools, especially
painting.

Ryan Reid
Systems Engineer

On Sat, 15 Jan 2005 21:13:54 GMT, "John Hall"
wrote:

Just got the Dec/Jan Copy . In the article titled"Shop compressed air for in
house tire service" The author describes in detail a coil of copper tube he
installed in his air line, but doesn't tell us why. Am I missing something?
Is it obvious why? All I can see is it adds volume to the system and might
be a good way to camoflage a still from the revenuers.

Anybody have any ideas?

John