Tuesday, July 17, 2012

Compressed Air and PVC - A Deadly Combination

There aren't many subjects that get me on my soapbox but PVC compressed air piping is certainly one of them. I am surprised by the number of otherwise competent people who choose PVC thermoplastic pipe to  convey compressed air around their shop or garage. Take it from me - don't do it. PVC in compressed air service can explode like a bomb, sending shards of the pipe in all directions.

Some people believe that utilizing heavy wall PVC (or schedule 80, in pipe parlance) is the answer. Others think CPVC (a higher temperature thermoplastic) is a viable option. Neither are an acceptable alternative to proper compressed air piping. 

The reason that PVC is dangerous in compressed air is that the material undergoes a "rubber to glass" transition at low room temperatures. As the term implies, PVC material exhibits rubber-like characteristics that makes it useful as low pressure liquid piping. At lower temps, PVC starts to exhibit glass-like characteristics where it becomes brittle and, well, glass-like.

The shock of a compressor kicking on or even starting or stopping an air tool can sometimes be all that it takes to cause catastrophic failure of the PVC piping. 

I've seen the aftermath of a PVC pipe failure and it isn't pretty. A friend ran a line of PVC around the perimeter of his home shop and one winter evening about a year later it exploded. Sharp shards of PVC pipe were embedded in wall studs, roof decking and one even broke a window. Thankfully, no one was in the shop at the time.  

If you want compressed air piping, budget for a qualified plumber to install the system. They can guide you on material and layout (hose connections, valves, condensate legs, etc.) The peace of mind that a correctly-installed system brings is priceless.

Compressed air is an invaluable tool for your shop, but it does demand your respect. Pass the word and maybe save a life.

1 comment:

  1. Whew... Good article!!! I hope my iron pipe distribution system passes muster.


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