Date: Tue, 29 Dec 1998 10:04:50 -0800
From: Douglas Shook <shook@usc.edu>
Subject: Re: Compressor air-lines and tank draining...
Stan Fickes wrote:
> Before I do something stupid in my shop, would someone please explain to me
> the problem with copper pipe for air? I understand the problem with PVC, but
> copper SEEMS like it should work... And it's much easier to work with than
> black iron. I keep trying to look at the archives, but my ISP has been
> having problems for the last week...
Stan,
I personally do not believe there is any problem with using copper, but
the "word" was that copper will "work harden" from the
expansion/contraction/pounding from the air, but I have not seen any
articles to support this.
As I said in the other post, I used the thick wall copper (can't
remember the coding) for underground burial. I know this falls under
the "I've washing my hands in acetone for 20 years and have had no
problems" type of heuristical advice, but it has been fine, as well I
think it should. The ratings clearly are high enough for air. I have
only had my shop piped in copper for the last two years or so, so I
cannot give you a 20 year testimonial.
When I see and hear the type of pounding/water hammering that my copper
water lines take every time the sprinkler valves snap open and close, I
cannot understand how the relatively very gradual increase and decrease
in pressure along the air lines could be a problem.
I made a "radiator," of sorts, out of 3/4" cooper between the
compressor pump head and the tank, and it is surviving just fine, too
(if any part suffers from heat, vibration, constant changes in pressure
each time the piston rises in the cylinder), it would be the radiator.
Most compressors come from the factory with some sort of copper lines as
after-coolers or inter-coolers (between the cylinders on two stage
pumps).
I advocate the use of copper for a variety of reasons:
- best thermal conductance for condensing water
- clean (no rust or flake in the lines)
- easy, fast to install and modify
- no threading
- much lighter than iron (running lines overhead)
- will not shatter/send shrapnel under pressure like standard pvc
- affordable (fittings, valves, etc.)
- reliable
The only problem I have had with copper is that when I initially made
the radiator, the solder would melt and blow out under sustained
operation. A shop talk lister suggest using silver solder, and it cured
the problem (this is only an issue if you are sweating in copper between
the pump head and the tank).
I don't know if anybody responded to the question regarding blowing out
the condensation from the tank, but short of putting in an automatic
valve, I just plumbed a 90 degree elbow, some 3/8" brass pipe to extend
out from underneath the tank and fitted a water spout. I put a small
can under the valve. Before starting for the day, I just open the valve
for a second or two to blow the water out of the tank into the can.
I always leave the tank pressurized, and generally do not need to dump
the can as the water will evaporate by the next day unless I am doing
blasting or other sustained operation.
good luck,
doug
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