"The 15 hp compressor feeds a small plant. An industrial hose of about 6 ft connects to PVC pipe from that point. The PVC pipe is swelling and bursting because of excessive heat from the compressor. I need trouble shooting tips."
PVC pipe is not "pressure pipe" as it pertains to the pressures seen in compressed air systems.
The pressure rating of plastic pipe is predicated on the temperature of the area in which the pipe is to be installed. The burst or fail pressure of plastic pipe falls dramatically as the tempeature rises. Hotter temperatures means that the pipe wall cannot handle the pressure and will fail, much like the PVC the visitor writes about.
Do your workers and your liability insurance folks a favor, and remove all plastic pressure pipe (unless the manufacturer says you can use it) completely! Fast!
I am not a supporter of black pipe. Since it is low cost though, that is the pipe of choice for many folks to use for their air mains. You will need to have some expertise in using threading equipment to install it, it is quite heavy to use, and in time, with the amount of water that a typical air compressor puts into the air mains flooding the black pipe, it will not be long before the pipe is rusting, pitting and scaling. This means that you will need effective air preparation equipment installed downstream from the black pipe to remove all the crud that it will, eventually, put into the air stream.
There are some air main systems that use aluminum piping. I perceive these to be the highest cost air main material, though the systems lend themselves to a more easier system than that of black pipe.
There are a number of plastic tubes available that are built to handle typical compressed air plumbing; polyethylene and urethane are a couple. They typically are small in diameter, and are meant to plumb compressed air from a manifold or air main to the point of use; air tools, valves etc. They typically are sized up to 1/2" O.D., and as such, are not large enough for plant air mains.
Please see the site map page on this site, under plumbing, for more information about installing compressed air lines.