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Class I, Division I Seal-Off Controversy

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    Class I, Division I Seal-Off Controversy

    I need your help as soon as possible.
    We have a dilemma at our current job site with installation of seal-off’s in a gas production facility at our present job site. The situation is that it is common practice to install a short within 18", a run from the seal-off, to a GUAC conduit body, on to a hazard rated union, and on to an instrument; in all, does not exceed the 18 inch maximum requirement as per NEC Art. 501.15(A)(1)(2) and 501.15(A)(3) See attached picture.
    With understanding that in NEC Art. 501.15(A)(3) first states that two or more enclosures basically have to have a seal-off within 18" of each other of not more than 36" in a conduit run and goes on to state "or run of conduit shall be considered sufficient if the seal is located not more than 450 mm (18 in) from the enclosure." Until now, our past customers in the Class I, Division I environment, ruled this installation acceptable and within guidelines.
    The reasoning on this is so that if the instrument needs to be replaced, that you can access conductors from the GUAC without damaging them. In addition, the instrument could be easily replaced without shortened or damaging branch circuit conductors, prevent possible seal-off damage and make termination readily accessible. Unfortunately, although this installation is common practice here in the gas and oil fields, the customer wages different to say that this installation is not legal.
    Please advise.
    Regards, Scooter Hoffman
    Click image for larger version

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    #2
    read carefully what the last paragraph of 501.15 (A) (2) says.
    Bob

    Comment


      #3
      These are not intrinsically safe circuits?

      Comment


        #4
        Violation if a seal is required, adding the extra volume of guac adds more to the possible explosion pressure on that seal. Its like going over 18". 501.15(A)(1) last paragraph after (1)&(2)

        Also, that liquidtight isn't legal, if c1d1 like you say

        Comment


          #5
          Prior to the 2017 code, conduit bodies of the same trade size as the conduit were permitted between the enclosure that requires sealing and the seal fitting.
          2014 501.15(A)(1) ... Only explosionproof unions, couplings, reducers, elbows, capped elbows, and conduit bodies similar to L, T, and Cross types that are not larger than the trade size of the conduit shall be permitted between the sealing fitting and the explosionproof enclosure.
          That permission to install conduit bodies between the enclosure and the seal was removed in the 2017 edition of the code.
          2017 501.15(A)(1) ...Only explosionproof unions, couplings, reducers, elbows, and capped elbows that are not larger than the trade size of the conduit shall be permitted between the sealing fitting and the explosionproof enclosure.
          Don, Illinois
          (All code citations are 2017 unless otherwise noted)

          Comment


            #6
            Thanks for clarifying

            Thanks for your support. I have read several forums relating to this issue and like the other fella's noticed in the 2017 that 'conduit bodies' was omitted compared to 2014 and not sure if it was intentional or error. It is what it is and thanks. Scooter

            Comment


              #7
              Originally posted by GHoffman View Post
              Thanks for your support. I have read several forums relating to this issue and like the other fella's noticed in the 2017 that 'conduit bodies' was omitted compared to 2014 and not sure if it was intentional or error. It is what it is and thanks. Scooter
              It was an intentional change. The panel statement on the revision said:
              Conduit bodies were removed from the list in (2) because they should not be allowed in this application due to the increased volume in the raceway system.
              Don, Illinois
              (All code citations are 2017 unless otherwise noted)

              Comment


                #8
                Picture clarification

                Pertaining to the attached picture, I received a call from the journeyman who installed the instrument and I need to clarify that the instrument was indeed in a c1d2 area. The problem that he has is that the instrument has external wiring much like a Murphy switch LS200. Problem in the field is most instruments having external wiring which have to have an immediate seal-off will have to require some sort of conduit body for terminating but with that would require a union (optional) and an additional seal-off on towards the raceway.
                So would it be: Instrument w/external wiring, seal-off, GUAC conduit body, c1d1 union, and 2nd seal-off?
                Am I right? Was hoping for more of a simpler scenario.
                Scooter

                Comment


                  #9
                  Originally posted by don_resqcapt19 View Post
                  It was an intentional change. The panel statement on the revision said:
                  What was the justification, other than it was someone's erroneous application of the precautionary principle? Did someone actually fill the section with an explosive mixture and spark it?

                  Comment


                    #10
                    Originally posted by GHoffman View Post
                    Pertaining to the attached picture, I received a call from the journeyman who installed the instrument and I need to clarify that the instrument was indeed in a c1d2 area. The problem that he has is that the instrument has external wiring much like a Murphy switch LS200. Problem in the field is most instruments having external wiring which have to have an immediate seal-off will have to require some sort of conduit body for terminating but with that would require a union (optional) and an additional seal-off on towards the raceway.
                    So would it be: Instrument w/external wiring, seal-off, GUAC conduit body, c1d1 union, and 2nd seal-off?
                    Am I right? Was hoping for more of a simpler scenario.
                    Scooter
                    why would you need a second seal, unless you are talking about the boundary seal?

                    eta: and why do you need an XP conduit body to make the splice in?
                    Last edited by petersonra; 02-11-19, 04:02 PM.
                    Bob

                    Comment


                      #11
                      If sealtight is an approved wiring method in this location, I am dubious of the seal requirement.

                      Comment


                        #12
                        Originally posted by gadfly56 View Post
                        What was the justification, other than it was someone's erroneous application of the precautionary principle? Did someone actually fill the section with an explosive mixture and spark it?
                        Adding a guac is creating a bigger bomb by volume, its like putting your seal at 6' instead of 18". Enclosures and seals have limits to the explosion they can contain.

                        Comment


                          #13
                          Originally posted by GHoffman View Post
                          Pertaining to the attached picture, I received a call from the journeyman who installed the instrument and I need to clarify that the instrument was indeed in a c1d2 area. The problem that he has is that the instrument has external wiring much like a Murphy switch LS200. Problem in the field is most instruments having external wiring which have to have an immediate seal-off will have to require some sort of conduit body for terminating but with that would require a union (optional) and an additional seal-off on towards the raceway.
                          So would it be: Instrument w/external wiring, seal-off, GUAC conduit body, c1d1 union, and 2nd seal-off?
                          Am I right? Was hoping for more of a simpler scenario.
                          Scooter
                          501 is not that long of a section to read and analyze, c1d1 and c1d2 are night and day different, you are mixing some parts together. If splices stay below auto ig temp they don't need seals. The best way for you to have a better understanding is to read and analyze the sections, we honestly might just confuse you more. After you do that then ask remaining questions if any, just my suggestion. If instrument needs seal off you need one between it and guac per 17'nec anyway , if terms are below 80% ait in guac then you don't need sealoff between liquidtught and guac
                          Last edited by Wire-Smith; 02-11-19, 08:22 PM.

                          Comment


                            #14
                            Originally posted by Wire-Smith View Post
                            Adding a guac is creating a bigger bomb by volume, its like putting your seal at 6' instead of 18". Enclosures and seals have limits to the explosion they can contain.
                            So, the answer to my question is "NO".

                            Comment


                              #15
                              Originally posted by gadfly56 View Post
                              So, the answer to my question is "NO".
                              I think your question is based on a false pretense that it should be considered safe until proven unsafe, while in the industry we do it the opposite way, things have to be proven safe in the lab before we use them in public. I am guessing they never tested the different variations of the application, only 18" of multiple nipples. The guacs may blow the cover off when you get a combination like a big enclosure and a 1/2" conduit and guac, or those small instrument seals may blow with a big guac.

                              Comment

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