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STRENGTH OF PANEL COVER IN RELATION TO ARC BLAST

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    #16
    Any ASTM standard for metal sheet thickness?

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      #17
      Originally posted by bobby ocampo View Post
      Any table on Cal/cm2 of metal sheet?
      Arc flash PPE is rated in Arc Thermal Performance Value (ATPV) which is in the units of cal/cm2. Effectively, this is the amount of heat that can be absorbed by the PPE while allowing about 1.2 cal/cm2 to be transferred to the wearer.

      An ATPV rating is not applicable to a heat radiator like a steel panel.
      Just because you can, doesn't mean you should.

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        #18
        I have a GIF movie of an MCC feeder bucket blowing open and the door coming off, but apparently this site won't accept GIF movies.
        __________________________________________________ ____________________________
        Many people are shocked when they discover I am not a good electrician...

        I'm in California, ergo I am still stuck on the 2014 NEC... We'll get around to the 2017 code in around 2021.

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          #19
          Originally posted by Jraef View Post
          I have a GIF movie of an MCC feeder bucket blowing open and the door coming off, but apparently this site won't accept GIF movies.
          And you do not have anyplace to host it?

          Sent from my XT1585 using Tapatalk

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            #20
            Originally posted by Jraef View Post
            I have a GIF movie of an MCC feeder bucket blowing open and the door coming off...
            It sounds like the fasteners failed. Did the door turn into shrapnel?
            Just because you can, doesn't mean you should.

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              #21
              Originally posted by jim dungar View Post
              It sounds like the fasteners failed. Did the door turn into shrapnel?
              Door became a projectile, yes. The definition of shrapnel includes “... or other object thrown out by an explosion.”

              I was at work when I was trying to post that image, but we are restricted from accessing any image hosting sites. I’ll have to bring my PC home to try to post it or email it to myself first (I use my iPad at home but that image is not on my iPad).

              I got that image when I worked for Siemens during a training class on retrofitting new breakers into old switchgear and MCCs. It was used as a warning to us on the dangers of not paying attention to the available fault current. The image is a brand new Siemens breaker with too low of a fault rating put into an old MCC bucket and blowing apart under fault current stress, taking the door with it.
              __________________________________________________ ____________________________
              Many people are shocked when they discover I am not a good electrician...

              I'm in California, ergo I am still stuck on the 2014 NEC... We'll get around to the 2017 code in around 2021.

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                #22
                [QUOTE=Jraef;2005259The image is a brand new Siemens breaker with too low of a fault rating put into an old MCC bucket and blowing apart under fault current stress, taking the door with it.[/QUOTE]

                So it was an improperly applied (under rated) breaker that exploded, not simply a door failing during an arcing fault event.
                Just because you can, doesn't mean you should.

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                  #23
                  Originally posted by Jraef View Post
                  Different issues. An Arc Flash Suit protects you from being burned. What I mean by "no rating" is that if there is an arc BLAST inside of the equipment, a cover blowing open can become shrapnel and kill you, suit or no suit.

                  https://www.youtube.com/watch?time_c...&v=9lbiYAMsOEY
                  Action happens at around 1:50
                  These means that the equipment should have a rating. One is the strenght of the cover and another is the strength of the bolt of the cover. If there is an arc blast inside the enclosure, common sense will dictate that the cover strength should be sufficient to protect the person in front of the switchgear or motor control.

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                    #24
                    Originally posted by bobby ocampo View Post
                    These means that the equipment should have a rating. One is the strenght of the cover and another is the strength of the bolt of the cover. If there is an arc blast inside the enclosure, common sense will dictate that the cover strength should be sufficient to protect the person in front of the switchgear or motor control.
                    You would think so, but doors staying closed during an arc flash / blast event is actually NOT a requirement of the equipment design under UL, NEMA etc. The only place it becomes addressed is in the requirements for equipment that is specifically labeled as "Arc Resistant" and tested under ANSI C37.20 or the equivalent IEEE spec.
                    __________________________________________________ ____________________________
                    Many people are shocked when they discover I am not a good electrician...

                    I'm in California, ergo I am still stuck on the 2014 NEC... We'll get around to the 2017 code in around 2021.

                    Comment


                      #25
                      Originally posted by Jraef View Post
                      You would think so, but doors staying closed during an arc flash / blast event is actually NOT a requirement of the equipment design under UL, NEMA etc. The only place it becomes addressed is in the requirements for equipment that is specifically labeled as "Arc Resistant" and tested under ANSI C37.20 or the equivalent IEEE spec.
                      If it not a requirement then what is the use of having a cover or to have a thick cover in switchgears and motor controls?

                      If ANSI Requires it then there should be a rating for the thickness of the sheet. Otherwise how will they calculate the thickness that will pass the test as Arc Resistant?

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                        #26
                        Originally posted by Jraef View Post
                        Different issues. An Arc Flash Suit protects you from being burned. What I mean by "no rating" is that if there is an arc BLAST inside of the equipment, a cover blowing open can become shrapnel and kill you, suit or no suit.

                        https://www.youtube.com/watch?time_c...&v=9lbiYAMsOEY
                        Action happens at around 1:50
                        Whoa!

                        Wonder what went wrong.
                        Our comedian shamelessly joked about a blackout. Talk about dark humor.

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                          #27
                          Originally posted by bobby ocampo View Post
                          If it not a requirement then what is the use of having a cover or to have a thick cover in switchgears and motor controls?

                          If ANSI Requires it then there should be a rating for the thickness of the sheet. Otherwise how will they calculate the thickness that will pass the test as Arc Resistant?
                          You seem to only be reading half of Jraefs posts. There is an ANSI standard for arc rated switchgear, which requires special design elements to be able to re-direct the arc blast. If your gear is not specially designed to be arc resistant then it was not designed or tested to be able to contain an arc blast so you cannot assume the covers will contain the blast.

                          Here is an example on a job I was on a few years ago

                          Click image for larger version

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                            #28
                            And here is a good presentation on the subject

                            http://www.wmea.net/Technical%20Pape...n_May_2016.pdf

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                              #29
                              Originally posted by bobby ocampo View Post
                              If it not a requirement then what is the use of having a cover or to have a thick cover in switchgears and motor controls?
                              The cover is there to prevent access to internal components such as energized parts. The thickness of the cover has to door with its structural integrity. a 12"h x 15"w MCC bucket door does not need to be as thick as a 72"h x 36" wide switchgear door that will have components mounted on it.
                              Just because you can, doesn't mean you should.

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