<VV> Air compressor distribution lines
corvairduval at cox.net
Mon Oct 31 08:21:02 EST 2005
>>Schedule 40 PVC!!!
> Never ever use PVC for compressed air!!! I can't remember where I heard it,
>but I remember the reasoning. If it fails, it shatters and sends sharp
>pieces at high velocity throughout your shop.
You may have seen the articles in trade publications for the auto repair
industry back in the mid 80's.
Yes, if there is a failure, the fact that compressed air is compressed (
125 psi for single stage compressor to 200 psi for two stage
compressor) and PVC pipe shatters (instead of break like metal pipe at
200 psi) you have a bomb hanging in your garage. Water or other liquid
compressed to 200psi is not compressed much, as it is non compressible.
Think brake system in the Corvair. When there is a failure, the pressure
drops immediately, so no bomb action. So PVC water pipe just leaks, not
explode. But, flexible plastic tubing is used in compressed air systems
in industry all the time. I guess the flexible nature of that plastic
tubing makes it less susceptible to shattering.
The failures 20 years ago with PVC compressed air systems were traced to
standard oil type compressors. The oil ridding along with the compressed
air was attacking the PVC pipe. If you have a PVC pipe rated for oil
duty then it will probably not break down. If you use an oilless
compressor then?? I would not recommend the use of PVC pipe based upon
these old failures. The only PVC installations I have seen pictures of
were homeowner installed systems, not auto repair or industrial
installations. I would recommend talking to local compressor dealers and
get their recommendation for the type of piping used in your area. Maybe
there are PVC types that are used in industry in your area.
As a benefit to us east coasters with humid air, the metal pipe helps
promote condensing of the water vapor out of the system, as metal has
more rapid heat transfer than PVC. You dry landers have no idea how much
water comes out of compressed air pipe here in VA in the summer.
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