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Thread: Class1 Div1 Explosion proof enclosure / conduit and 2" flange seals

  1. #1
    Join Date
    Dec 2016

    Class1 Div1 Explosion proof enclosure / conduit and 2" flange seals

    Hi Mike and Forum Community,
    Thank you for all your wonderful insight I have been following your web page for years. Currently I am working on a custom explosion proof enclosure, where the customer requires 2 holes be put into the enclosure. 1 for the conduit, which seems pretty straight forward, and another 2” hole where a circular flange will be mounted/ inserted into enclosure. The electrical connections happen inside enclosure and on the face of the flange.

    Reading through article 501 it is unclear if this is possible and or acceptable (2" flange seal). Would I follow the same rules for mounting the 2 inch flange as i would for the threaded conduit?
    1. Use threaded conduit at least 6 threads deep… therefore the mounting screws (explosion proof) 6 threads deep is ok?
    2. Use sealing compound. Use sealing compound around screws and in-between flange and enclosure?

    Or should I for-go the flange and modify the unit to be attached to a threaded 2" attachment and then use the 6 thread deep with thread sealant for this application?

    Any insight or another article I could read regarding how to properly do this would be greatly appreciated.
    Thank you in advance!

  2. #2
    Join Date
    Apr 2004
    Mission Viejo, CA
    I’m not a manufacturer, but penetrating an explosionproof enclosure with non-electrical systems is certainly possible. However, it takes more than just putting a flange on the outside. In any case, the enclosure must be NRTL certified and it would be best to consult with one to obtain their “blessing”.
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

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