<VV> Air compressor distribution lines

Frank DuVal 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.
>Marc Sheridan
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.

Frank DuVal

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