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All
I am a mechanical engineer with many years of piping system design. I think
you will find that the reason none of the standard PVC pipe catalogs list
ratings for air is that the manufacturers specifically don't want the pipe
used for pneumatic systems. The problem is one of brittle failure and
sending sharp shrapnel flying thru the shop.
That being said, I did use PVC in my personal shop with a bunch of safety
precautions. First off the compressor is in an attic space and the
regulator is set at about 110 psi. I used about 20 feet of copper first
sort of as an aftercooler followed by a moisture trap. Then, the pipe is
routed around in the attic space inside the insulation. The temperature
stays fairly constant, between about 50 and 80 F. If I do have a problem,
it's upstairs and I am down, effectively shielded by the attic space.
Finally, I used 1/2 inch, Sch 40 which is rated at 600 psi, giving me a
safety factor of well over 5. I feel safe with my system, and have never
had any problems in the last 15 years since I installed it.
The rated pressure on PVC pipe goes down as the temperature increases and
the size increases. 1 1/4 schedule 40 is rated at 370 PSI at 73.4 degrees.
Using that with a working pressure of up to 175 gives a safety factor of
just over 2. I wouldn't do it. A 100 foot length of pipe at 175 psi or
about 12 atmospheres stores a tremendous amount of energy.
Jim Norlin
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