Boundary Seals - Underground Transitions

[The_G_Man]

I have a case where my conduit run starts in a Class I, Div 2 area, travels underground (regarded as non classified area) and ends back in the same Class I, Div 2 area.

Technically I'm going through two area boundaries (from Div 2 to unclassified back to Div 2) and I would have to put seals within 10 ft of each transition. However, I fail to see how this is a realistic need. I don't mean to reinvent or debate the code but I believe that the intent of having seals is to prevent gas from using a conduit to migrate into an non hazardous area and in my case I just don't see how this can be a concern.

I can't find any undisputable code reference that permits me to NOT install seals at the two boundaries (most of the exceptions listed refer to scenarios that are almost the opposite of mine, such as unbroken metal conduit runs that start and end in non-hazardous location and pass through a Div 2 without any unions, couplings, boxes of fittings)

Does anyone have a code reference I can use to justify not using seals or shall I just bite the bullet and account for them?


Thank you all for your assistance!

 

[ptonsparky]

IMO, we would not want a fault in the conduit to result in problem at either end of it. I would seal both ends.

 

[petersonra]

I see it as crossing the D2 to unclassified boundary twice, thus the need for two seals.

I am inclined to agree it serves no useful purpose.

 

[rbalex]

The basic philosophy for seals is found in Section 501.15 IN No. 1.

In the OP application, a seal is required at each boundary; however, it is not required to be explosionproof. [Last sentence of 501.15(B)(2)]

While ptonsparky mentioned a condition where seals might be useful, that value is severely reduced since they aren't required to be explosionproof. [See above]

If both ends of the run were in the same Division 2 envelope, created by the same source throughout, the seals may be unnecessary (that is, basically useless) but this is currently not a recognized exception. Otherwise, a fire, and not necessarily an explosion, in one Division 2 location could be propagated to another Division 2 location through the raceway,