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Thread: Conduit Sealing for IS or NI instruments

  1. #1
    Join Date
    Dec 2010
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    Conduit Sealing for IS or NI instruments

    The subject installation involves IS rated instruments that are physically located in a Class 1 Div 2 area. These instruments will be wired to a PLC panel that is outfitted with a Z-Purge system. The proposed wiring installation method is to run wiring between the PLC panel and the IS rated instruments. Can you advise as to which of the following methods are acceptable? If the answer is that none of the below are acceptable, then please suggest a solution that preferably avoids the needs for barriers.

    1. EYS fittings will be installed at the location for each IS instrument and similarly for the conduit exiting the PLC panel. The fittings would be poured/sealed. Does the Z-Purge on the PLC panel eliminate the need for the sealed fittings?

    2. IS Barriers are installed within the PLC panel for each IS instrument. No seals are used for the conduit and wiring.

    3. Z-Purge on the PLC panel is sufficient. Seals or IS Barriers are not needed.

    Thank you,
    KCCA

  2. #2
    Join Date
    Dec 2011
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    Ocala, Florida, USA
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    Quote Originally Posted by kcca View Post
    The subject installation involves IS rated instruments that are physically located in a Class 1 Div 2 area. These instruments will be wired to a PLC panel that is outfitted with a Z-Purge system. The proposed wiring installation method is to run wiring between the PLC panel and the IS rated instruments. Can you advise as to which of the following methods are acceptable? If the answer is that none of the below are acceptable, then please suggest a solution that preferably avoids the needs for barriers.

    1. EYS fittings will be installed at the location for each IS instrument and similarly for the conduit exiting the PLC panel. The fittings would be poured/sealed. Does the Z-Purge on the PLC panel eliminate the need for the sealed fittings?

    2. IS Barriers are installed within the PLC panel for each IS instrument. No seals are used for the conduit and wiring.

    3. Z-Purge on the PLC panel is sufficient. Seals or IS Barriers are not needed.

    Thank you,
    KCCA
    I assume from your post that the PLC panel is in the Class 1 Div 2 area. If so, then no seals are going to be required and in fact the wiring can be in FMC even. They probably want a seal at the PLC panel to block the purge gasses though.


    I know what I don't know, and I know where to go to find it!

  3. #3
    Join Date
    Apr 2004
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    Mission Viejo, CA
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    5,238
    Quote Originally Posted by kcca View Post
    The subject installation involves IS rated instruments that are physically located in a Class 1 Div 2 area. These instruments will be wired to a PLC panel that is outfitted with a Z-Purge system. The proposed wiring installation method is to run wiring between the PLC panel and the IS rated instruments. Can you advise as to which of the following methods are acceptable? If the answer is that none of the below are acceptable, then please suggest a solution that preferably avoids the needs for barriers.
    1. EYS fittings will be installed at the location for each IS instrument and similarly for the conduit exiting the PLC panel. The fittings would be poured/sealed. Does the Z-Purge on the PLC panel eliminate the need for the sealed fittings?

    2. IS Barriers are installed within the PLC panel for each IS instrument. No seals are used for the conduit and wiring.

    3. Z-Purge on the PLC panel is sufficient. Seals or IS Barriers are not needed.

    Thank you,
    KCCA
    I apologize for the late response, but the meds I’ve been on this last week could get me a AUI (Answering Under the Influence)

    I should make a few comments:

    1. Without a control drawing [Sections 501.10(B)(3) or 504.10(A)] you do not have an NI or IS System no matter how the instruments are rated.
    2. An EYS seal mandates it is an explosionproof seal under both Sections 110.3(B) and 501.15(C) since the compound is required under the EYS listing. An explosionproof seal for a non-explosionproof enclosure is worthless.
    3. Pressurizing the PLC does benefit the enclosure AND it does not require an explosionproof seal assuming the “boundary” is the PLC exterior. See the last sentence of Section 501.15(B) and its Exception No. 3. However, it does nothing for the instruments themselves.

    SO basically,
    · Pressurizing the PLC is fine
    · No seals are required for the PLC, but may be beneficial to maintain pressure.
    · The instruments will still need some recognized form of protection technique apart from pressurizing the PLC.
    · If you choose an NI or IS protection technique, you need a control drawing.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  4. #4
    Join Date
    Jan 2018
    Location
    Kentucky
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    7
    Quote Originally Posted by rbalex View Post
    I apologize for the late response, but the meds I’ve been on this last week could get me a AUI (Answering Under the Influence)

    I should make a few comments:

    1. Without a control drawing [Sections 501.10(B)(3) or 504.10(A)] you do not have an NI or IS System no matter how the instruments are rated.
    2. An EYS seal mandates it is an explosionproof seal under both Sections 110.3(B) and 501.15(C) since the compound is required under the EYS listing. An explosionproof seal for a non-explosionproof enclosure is worthless.
    3. Pressurizing the PLC does benefit the enclosure AND it does not require an explosionproof seal assuming the “boundary” is the PLC exterior. See the last sentence of Section 501.15(B) and its Exception No. 3. However, it does nothing for the instruments themselves.

    SO basically,
    · Pressurizing the PLC is fine
    · No seals are required for the PLC, but may be beneficial to maintain pressure.
    · The instruments will still need some recognized form of protection technique apart from pressurizing the PLC.
    · If you choose an NI or IS protection technique, you need a control drawing.
    The pressurized and purge system elimates need for seal in division 2 locations but you must have a compression seal or approved seal and a hazardous drain on outside of seal between conduit. Cannot use those aluminum drains. However there are some manufacture requirement require a union and fmc for this type of equipment. Please be careful. The fmc cannot be between drain and equiment. Therefore it defeats its purpose and the installation will look in professional. In this situation you will have to use class 1 division 1 rules here where the company is requiring a disconnecting means of equipment for maintenance. Here starting at equipment pressurised seal installed horsecock ( unofficial name to get actual name contact Crouse hinge) approved fittings like a ninety or straight think it will come with a yellow plastic piece instead of green for rigid approved fmc fittings, then install approved union must be rigid and explosion proof, predetermined length horsecock, another fitting then seal off with hazardous drain installed in explosion proof seal off fitting. After this you can go back to division two rules. So make sure you do the research first as to what the customer or manufacture requires on the let say ph indicator transmitter and then go from there. Be careful it can be costly to have to come back and cut out conduit on some of these instrument because cable is factor measured and calibrated in a lot of these situations. Hope I helped. A good tool is Crouse hinge hazard location pdf. It will give ya a definite answer for each control or instrument device in a class 1 division 2 location.

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