teflon on cl1 div1

[Fulthrotl]

I can't remember if it was an OZ-G or Appleton catalog, but it showed at the fittings the threads are considered an explosion exhaust component, allowing the gas to cool and exit without being an ignition source.

yeah, it's all about dwell time. the pipe is sufficient to contain the explosion,
and the threads and covers are designed to allow the gases to cool below
the ignition point of the surrounding atmosphere. 5 full turns on a coupling,
fitting, or threaded cover is sufficient, even if the fitting is not tight.

the appelton guy was demonstrating with propane in a display, and
a 4" round box with a threaded cover still contained the explosion with only
two full threads of engagement. a bolted flange cover, such as a disconnect
needs to have the flange faces clean and free of grease or dings, and the
bolts must be torqued to specification.... more inherently troublesome than
a threaded cover. the criteria for flatness on bolted flanges is .003" with a
feeler gage. if the thinnest gage goes between the flanges, it's time for a
trip to the machine shop. blanchard grinding is the quickest and easiest way
to renew the surfaces.

 

[Rockyd]

Hey Fulthrotl,

Pretty cool that the gasses cooled sufficiently in only two threads. gives a 250% safety factor over the NEC's minimum for safety. Always makes me leary the first time to a site, till you can do a walk around to see who did what kind of work prior to my arrival. Some work is outstanding, other make me want to run from the processing area...

It's a bit tough to explain what happened if ever there is that incident where someone tried "to let the smoke out" of a C1D1 area