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Thread: Hazardous Lacation Seal Off

  1. #11
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    Quote Originally Posted by petersonra View Post
    seals are threaded. if you have one on the D1 side how come no hazardous gases can get into the conduit leading to the non-hazardous side?
    Yes, and not only that you can place a reducer in the seal.[Sections 501.15(A)(4) and 501.15(B)(2) (my idea BTW)] Remember, the seal is only to minimize, not prevent, the passage of flammables [Section 501.15 IN No.1] By the time all the packing and sealing compound in the seal is considered, minimizing passage in a properly installed seal is well covered. This has been confirmed by both manufactures and UL. Of course, a Division 2/unclassified seal doesn't have to be explosionproof in the first place, but there aren't supposed to be any flammables in the first place either under normal operating conditions.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  2. #12
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    Quote Originally Posted by MRKN View Post
    From what I can tell as long as the threaded fitting is below grade and therefore in an unclassified zone it's acceptable. The problem is when it's above grade and therefore in a hazardous area. So while I appreciate the humor in your comment I don't think it's quite accurate.
    In most cases a below grade seal is unacceptable [Section 501.15(C)(1)]
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  3. #13
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    Quote Originally Posted by MRKN View Post


    I see now, screwed fitting/threaded interface would fall under the definition of union/fitting/coupling in 501.15(A)(4). Thanks.

    Could you argue the orientation in which the seal is installed would still introduce a threaded interface for gases to be introduced into an unclassified area if the liberty was taken to install the seal on the 10' inside of the boundary?

    If you consider the seal, rather than the seal fitting, the fitting's orientation makes no difference.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  4. #14
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    Quote Originally Posted by rbalex View Post
    In most cases a below grade seal is unacceptable [Section 501.15(C)(1)]
    I'm referring to the nipple being below grade, not the seal. Having the nipple below grade would obviate his concern for an unreasonably large and unconventional piece of conduit by moving the threaded fitting into an unclassified area.

  5. #15
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    Quote Originally Posted by rbalex View Post
    If you consider the seal, rather than the seal fitting, the fitting's orientation makes no difference.
    My question was ultimately the same point that petersonra was making - having a threaded fitting on the nipple above grade is ostensibly the same risk as having the threaded fitting on one side of the seal. So from that perspective it seems a little silly. I suppose the idea being with the way the code is written is that allowing it only at the seal (where it is necessarily "minimized" as you have mentioned) does not allow an "unlimited" amount of additional threaded fittings, you'd of course end up with someone who would install 9 nipples back to back in the hazardous area between the seal and the "imaginary envelope"/boundary.

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