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Thread: Class 1 Div 1 or Class 1 Div 2

  1. #1
    Join Date
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    Class 1 Div 1 or Class 1 Div 2

    Our company designs sensors used to measure different gaseous components. Typically, we design enclosed sample panels to condition the samples in order to measure them. Our analyzers are explosion-proof but we typically contain our sample conditioning panels inside a NEMA4X enclosure. My question is this: if the gases flowing through the sample conditioning system are combustible, is the inside of our enclosure Division 1 or Division 2? I ask because I want to make sure we are sealing our conduit correctly and in the correct locations.

    My confusion comes from the NEC definitions of Div 1 vs Div 2.

    500.5(B)(1)(2): In which ignitible concentrations of such flammable gases,flammable liquid–produced vapors, or combustible liquids above
    their flash points may exist frequently because of repair or
    maintenance operations or because of leakage,

    vs.

    500.5(B)(2)(1): In which volatile flammable gases, flammable liquid–producedvapors, or combustible liquid–produced vapors are handled,
    processed, or used, but in which the liquids, vapors, or gases
    will normally be confined within closed containers or closed
    systems from which they can escape only in case of accidental
    rupture or breakdown of such containers or systems or in case
    of abnormal operation of equipment,


    What is the difference here between leakage and abnormal operation of equipment? Aren't valves and fittings only supposed to leak under "abnormal operation of equipment?"

    Apologies for the long post, any input would be extremely helpful.

  2. #2
    Join Date
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    Placerville, CA, USA
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    Some components may in fact have a measurable leakage during normal operation. Like some valves while they are being operated. If they do not, then they would only leak under abnormal conditions.
    The manufacturer should be able to tell you authoritatively.

    Sent from my XT1585 using Tapatalk

  3. #3
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    If that is the case then the inside of our cabinet would be classified as a Div 2 environment, correct?

  4. #4
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    Quote Originally Posted by rusty6 View Post
    If that is the case then the inside of our cabinet would be classified as a Div 2 environment, correct?
    The API RP-500, while not code, but a recommended practice in article 10.16 states that if the panel is inadequately ventilated, it should be CID1. Some analyzer companies seem to agree, but Spectra Sensor for one classifies their analyzers CID2 with no ventilation or purging.

  5. #5
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    That would be my take, but this is not my area of expertise.

    Sent from my XT1585 using Tapatalk

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