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Posted by David Sherman [24.32.202.83] on Friday, December 11, 2009 at 18:34:31 :
In Reply to: Re: PEX pipe for air lines? posted by Ryan [76.164.144.129] on Friday, December 11, 2009 at 14:32:59 :
It seems strange that an air compressor could suck enough fumes out of shop air to form an explosive mix, and yet the guy working in the shop was still conscious and the air in the shop didn't explode.
Some years ago at one of the mines here they got the wrong kind of oil in the air compressor. I don't know if you've ever seen the air compressors they use in serious underground mines, but they're huge (thousands of HP sometimes), as are the receivers. In some cases, they actually mine a big cavern out underground and use it for the receiver. I believe this was one of the old Ingersoll 2-stage piston compressors that looks much like a horizontal steam engine with a big flywheel. Nowadays, they mostly use screw compressors. I don't remember the details, as told by an old-timer -- whether they switched vendors or the salesman convinced them to buy this new and improved oil, or the buyer found a cheaper source, or whatever -- but the new oil was not rated for air compressors and formed an explosive mist or vapor which blew a substantial portion of the compressor machinery and associated plumbing apart. We run a small (40 HP) screw compressor at the mine tour and it uses ATF for its lube.
Obviously pressure and temperature make an air/oil mix more explosive, as in a diesel engine. 120 psi in an air compressor is maybe half of the pressure in a diesel engine, but it's getting there. I'm not saying paint fumes couldn't explode in an air line as well, since they're also concentrated and pressurized, but I can also see a worn compressor that's blowing too much oil past its rings, if running long and hard with hot air getting into the lines, and maybe the wrong kind of oil, developing an explosive mixture.
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