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Thread: PVC Coated Rigid in Class II

  1. #1
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    PVC Coated Rigid in Class II

    NEMA bulletin linked at end states "PVC -coated RMC, IMC or EMT are not intended for use in a Class II classified location due to the possibility of a static charge on the PVC coating."

    However, I see several manufacturers (RedDot, Clabond, etc) marketing their PVC Coated conduit offerings for Hazardous Locations including Class II dust locations and have found no other literature on this concern. I understand the static electric discharge concern but seems somewhat unrealisticand as the plastic coated metal pipe is bonded on both ends. I have reviewed NFPA 77 but the standard only adresses limiting plastic conduit used for fluid transfer and has no commentary in annex or standard on PVC coated conduit being restricted or recommended against in dust locations.

    Just looking for opinions, PVC coated rigid metal conduit in Class II Hazardous Locations - is there a real concern here?

    Thanks.

    https://www.nema.org/Technical/Docum...g%20Tubing.pdf

  2. #2
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    Quote Originally Posted by smoothops10 View Post
    NEMA bulletin linked at end states "PVC -coated RMC, IMC or EMT are not intended for use in a Class II classified location due to the possibility of a static charge on the PVC coating."

    However, I see several manufacturers (RedDot, Clabond, etc) marketing their PVC Coated conduit offerings for Hazardous Locations including Class II dust locations and have found no other literature on this concern. I understand the static electric discharge concern but seems somewhat unrealisticand as the plastic coated metal pipe is bonded on both ends. I have reviewed NFPA 77 but the standard only adresses limiting plastic conduit used for fluid transfer and has no commentary in annex or standard on PVC coated conduit being restricted or recommended against in dust locations.

    Just looking for opinions, PVC coated rigid metal conduit in Class II Hazardous Locations - is there a real concern here?

    Thanks.

    https://www.nema.org/Technical/Docum...g%20Tubing.pdf
    It may be that unmodified PVC exhibits enough propensity for static accumulation that it is not appropriate for class II locations.

    It seems possible that the listing standards would cover this.

    It also seems possible that slightly modified PVC would not have this issue.

    Why don't you send an email to someone like Robroy and ask them this specific question.
    Bob

  3. #3
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    Quote Originally Posted by smoothops10 View Post
    NEMA bulletin linked at end states "PVC -coated RMC, IMC or EMT are not intended for use in a Class II classified location due to the possibility of a static charge on the PVC coating."

    However, I see several manufacturers (RedDot, Clabond, etc) marketing their PVC Coated conduit offerings for Hazardous Locations including Class II dust locations and have found no other literature on this concern. I understand the static electric discharge concern but seems somewhat unrealisticand as the plastic coated metal pipe is bonded on both ends. I have reviewed NFPA 77 but the standard only adresses limiting plastic conduit used for fluid transfer and has no commentary in annex or standard on PVC coated conduit being restricted or recommended against in dust locations.

    Just looking for opinions, PVC coated rigid metal conduit in Class II Hazardous Locations - is there a real concern here?

    Thanks.

    https://www.nema.org/Technical/Docum...g%20Tubing.pdf
    While I would be loathe to ignore a NEMA document, in this case, in over fifty years working with classified locations, I've never come across such a restriction. It certainly is neither an NEC nor UL requirement. Since the original publishing date of the Bulletin is 2008, NEMA has had several opportunities to memorialize this in both the NEC and UL Standards. (I will confess, I've never used PVC coated raceway in a Class II environment.)

    I concur with Bob (petersonra), consult with an actual manufacturer for their experience.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  4. #4
    Join Date
    Jul 2017
    Location
    Alberta, Canada
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    Static electricity is not mentioned in the NEC, except in connection with electrostatic processes (spray booths, printing, etc.). So both non-metallic and plastic-coated metallic conduit should be technically OK.

    Also, the NEC specifically allows PVC and RTRC conduit in Class II, Division 2 locations (in certain circumstances). Hard to see how PVC-coated metal conduit could have a difficulty!

    Practically speaking - and without actually seeing the construction - I would think coated metallic conduit is almost certainly OK, regardless of if the underlying metallic conduit is bonded or not. The underlying metal will allow charge redistribution across the plastic coating, preventing localized charge accumulations that might results in a discharge.

    Non-metallic conduit is teeny bit riskier, but still probably OK, unless it's somehow in an area where it may get a lot of charge accumulation. This doesn't normally happen unless it's exposed to a lot of moving dust, like in a dust conveyance system, which would be pretty unusual.

    RBWH*, Europeans are / have been much more concerned with static and generally mandate all non-metallic materials in hazardous areas be antistatic, or otherwise proven safe. Not so here - the only such requirements I know of in North America are the ones we adopted from the European equipment standards as part of harmonization.


    [* RBWH = Risking Bob's wrath here (for providing non-USA-centric info for context)]

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