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Thread: External seals required or not?

  1. #1
    Join Date
    Nov 2017
    Location
    Denver, CO, USA
    Posts
    10

    External seals required or not?

    Have a bunch of Rosemount series 3051 pressure transmitters in a C1 D2 space, here is the URL to the unit specs and approvals:

    http://www2.emersonprocess.com/sitea...-0100-4001.pdf

    In the above document, the section for the 3051C series contains a page of approvals, attached here (hope this works):
    3051C Approvals.pdf

    The units do not specifically say "Factory Sealed" or "No External Seal Required" or suchlike, as many other devices do. But I've been told these generally do not require sealing, and want to make sure I understand why, if true.

    If not marked as above, 2017 NEC has an exception d. to 501.15 (A) (1) (1), copied below. This is the only reference I can find to nonincendive and/or intrinsically safe in the Art. 501 sealing sections.

    d. The switch, circuit breaker, fuse, relay, or resistor is part of a nonincendive
    circuit.

    Does this, because it is called out as nonincendive and intrinsically safe in its approvals, allow the omission of an external seal?

    I checked Art 504, Intrinsically Safe Apparatus, and found this, regarding sealing:

    504.70 Sealing. Conduits and cables that are required to be
    sealed by 501.15, 502.15, 505.16, and 506.16 shall be sealed to
    minimize the passage of gases, vapors, or dusts. Such seals shall
    not be required to be explosionproof or flameproof but shall
    be identified for the purpose of minimizing passage of gases,
    vapors, or dusts under normal operating conditions and shall
    be accessible.
    Exception: Seals shall not be required for enclosures that contain only
    intrinsically safe apparatus, except as required by 501.17.


    501.17 Process Sealing. This section shall apply to process connected
    equipment, which includes, but is not limited to,
    canned pumps, submersible pumps, flow, pressure, temperature,
    or analysis measurement instruments.

    The documentation appears to show all manner of sealing, which I unfortunately do not understand completely. I think 501.17 requires the equipment/instrument to be adequately sealed against the entry of process chemicals/fluids etc., which it would seem (and I would hope) has been done adequately.

    What do you think, is this enough info to determine that these do not require external seals? I am certain I must have missed other stuff, any help would be appreciated...

  2. #2
    Join Date
    Apr 2004
    Location
    Mission Viejo, CA
    Posts
    5,238
    You are potentially dealing with two Sections of Code: 501.15(F)(1) and 501.17.

    The relevant clauses are:
    501.15(F) Drainage.
    (1) Control Equipment. Where there is a probability that
    liquid or other condensed vapor may be trapped within
    enclosures for control equipment or at any point in the
    raceway system, approved means shall be provided to prevent
    accumulation or to permit periodic draining of such
    liquid or condensed vapor.
    501.17 Process Sealing. This section shall apply to process connected
    equipment, which includes, but is not limited to,
    canned pumps, submersible pumps, flow, pressure, temperature,
    or analysis measurement instruments. A process seal is a
    device to prevent the migration of process fluids from the
    designed containment into the external electrical system.

    Process-connected electrical equipment that incorporates a
    single process seal, such as a single compression seal, diaphragm,
    or tube to prevent flammable or combustible fluid"
    from entering a conduit or cable system capable of transmitting fluids,
    shall be provided with an additional means to mitigate
    a single process seal failure, The additional means may
    include, but is not limited to, the following:
    ...
    Process-connected electrical equipment that does not
    rely on a single process seal or is listed and marked "single
    seal" or "dual seal" shall not be required to be provided
    with an additional means of sealing.

    Informational Note: For construction and testing requirements
    for process sealing for listed and marked single seal,
    dual seal, or secondary seal equipment, refer to ANSI/ISA-
    12.27.01-2011, Requirements for Process Sealing Between
    Electrical Systems and Flammable or Combustible Process
    Fluids.
    Without being listed and marked "single seal" or "dual seal", the instrument requires an external seal.

    Before 2011 Section 501.17 was largely part of Section 501.15(F)

    BTW Article 501 doesn't mention Intrinsically Safe anywhere.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  3. #3
    Join Date
    Jul 2015
    Location
    Soldotna, AK, USA
    Posts
    125
    Quote Originally Posted by Schmoleskin View Post

    The units do not specifically say "Factory Sealed" or "No External Seal Required" or suchlike, as many other devices do. But I've been told these generally do not require sealing, and want to make sure I understand why, if true.

    Think you answered your own question, if they do say no seal required and such I would say your safe following the simply written instructions. I find following the instructions to a T makes it really easy to answer why I did something. "Why you do that!" "The instructions said to..."

  4. #4

    Seals

    Quote Originally Posted by AKElectrician View Post
    Think you answered your own question, if they do say no seal required and such I would say your safe following the simply written instructions. I find following the instructions to a T makes it really easy to answer why I did something. "Why you do that!" "The instructions said to..."
    Post 41 is not entirely correct in that where State adopted code in part list exception either in part or full is permissive then all codes referenced where exceptions apply based on thoroughly AHJ published may trump all of the above discussion's to

  5. #5
    Join Date
    Nov 2017
    Location
    Denver, CO, USA
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    Cannot be argued, following directions... novel idea. Ok, I give.

    Quote Originally Posted by AKElectrician View Post
    Think you answered your own question, if they do say no seal required and such I would say your safe following the simply written instructions. I find following the instructions to a T makes it really easy to answer why I did something. "Why you do that!" "The instructions said to..."

  6. #6
    Conduit seals or cable seals typically prevent pressure piling. Typically in the State of AK the Alaska Administrative Code (AAC) has provisions for adoption and licensing and regulation purpose of AS 08.40.005-AS 08.40.200 if that assistance is not avalliable attorney of regulations might be able to clear up allowable interpretation of requirement.

  7. #7
    Join Date
    Apr 2004
    Location
    Mission Viejo, CA
    Posts
    5,238
    If you ignore the addict's non sequiturs, AKelectrician's advice is fine. However, both of them were referring to Section 501.15 seals. The discussion is about process seals (Section 501.17). It is conceivable a factory sealed device will not be suitable for a process seal and/or a process seal will not be suitable for a factory seal. They have two different purposes.

    As always, following the manufacturer's instructions is required [Section 110.3(B)]
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  8. #8
    Join Date
    Jul 2015
    Location
    Soldotna, AK, USA
    Posts
    125
    Quote Originally Posted by nec_addicted View Post
    Conduit seals or cable seals typically prevent pressure piling. Typically in the State of AK the Alaska Administrative Code (AAC) has provisions for adoption and licensing and regulation purpose of AS 08.40.005-AS 08.40.200 if that assistance is not avalliable attorney of regulations might be able to clear up allowable interpretation of requirement.
    "A person who knowingly violates AS 08.40.005 - 08.40.200, or who knowingly violates a valid regulation or order of the department or a minimum electrical standard established under AS 18.60.580 - 18.60.590 that was in effect at the time that the installation or repair was made, is guilty of a misdemeanor, and upon conviction is punishable by a fine of not more than $5,000."

    You lost me, I said follow the instructions. If you use a device and its arky sparky and flammable materials or explosive conditions are present you need a seal to keep the explosive materials/conditions out. Then when something does go wrong in the box or what have you the heat is contained and slowly released at a acceptable temperature, as to not let the explosive materials/conditions around it explode. So, unless the arky sparky device says I don't need a seal. Seal it. There are of course exemptions for splices and such that don't arky sparky in normal conditions. But you'd have to read the instructions that fit your requirements to answer what is or isn't allowed.

    At least thats what the simply written book I read said...

  9. #9

    External Process seals

    Rosemount 3051 series transmitters have limited availability for coplanar capillary specific external process seals since the original post did not mention 2051C or 2051T as are readily avaliable with coplanar accessories I did ignore 501.17 since it does not follow as an option for 3051 series.

  10. #10

    Process Seals

    Diaphram seals are as secondary process sealing are particularly effective in clean oxygen service but no flush option since that part of bleach plants in oxygen service on fourth stage before high density towers prior to the wet end of turbine line shaft driven machines. Other application in dirty service such as brown stock washing I would use process tees and staggered taps not orifice taps on process since typically diaphram seals as in 501.17 are mostly liquid level application direct mounted to a mating flange.

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