anyone knowledgeable about nec article 515?

I teach a class of electrical apprentices and would appreciate dialogue with someone on articles 511 through 516.

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I have done much work covered by those articles and also inspected to them. What do you want to know? Our Alaska pipeline, north slope oil company facilities, and pump stations have given most Alaskan electricians more than their share of explosion proof work.
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-------------------------------------------------------------------------------- Ideally, I'd like a live chat on this but...I teach a class of manufacturing plant electrical apprentices and I need some confirmation of my understanding of article 513.8 A and B and 513.9.
I believe that although 513.8 A requires wiring methods complying with Class I Div 1, it stops short of stating that underground locations are in fact class I Div 1. Having said that, if I have an underground installation in rigid conduit under the hanger floor, and it pops up into a non-hazardous area such as an area suitably cut off from the hangar per 513.3.B, is it crossing a boundary and therefore require a seal? It seems to me in the strict interpretation of the text that it would not be crossing a boundary.
Correct me if I'm wrong. Confirm if I'm right please.
Thanks. Dennis

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wrote:

In the 2005 code section 513-8(B) was modified and now reads:
"Uninterrupted raceways that are embedded in the hanger floor or buried beneath the the hanger floor shall be considered to be within the Class I location above the hanger floor, regardless of the point at which the raceway descends below or rises above the floor"
Sealing is required per 501.15 or 505.16.
Seems like your interpretation had been tried before and didn't pass code making committee muster...
E. Tappert
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