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Thread: Bolt Torque on Bus bars

  1. #11
    Join Date
    Dec 2011
    Location
    Ocala, Florida, USA
    Posts
    2,683
    Quote Originally Posted by JRumsey View Post
    Haha...unfortunately, I am the switchgear manufacturer. I am being questioned on our current torquing process and its values versus the bolt manufacturers standard torquing values. The people who created our current charts are long gone (along with the reasoning behind the values). I am hesitant to just use bolt manufacturers values since the bus bar will heat up and expand; I don't think this is considered in the bolt manufacturers values.
    I wouldn't change them without reason. Standard torque values for bolts as I understand them are specific to the bolts and the nuts. It has to do with how much the metal is stretched and stressed vs. the hold value. Take the heads on a care. The torque is very specific to the application. The bolts are specifically made to act a certain way to the required torque pressure on the head in the correct order. If standard torquing were all that was required for a bus connection then why would Belleville washers even be necessary?


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  2. #12
    Join Date
    Jul 2003
    Location
    New Jersey
    Posts
    25,802
    Here's the table that we are currently using.

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    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  3. #13
    Join Date
    Jul 2006
    Location
    San Francisco Bay Area, CA, USA
    Posts
    8,006
    Published torque values for the bolts themselves are the MAXIMUMS that should ever be used, but that's not to say they can be used at lower values. The values that you actually use are all application specific. I would go by the industry standards. ANSI C37 has a section on switchgear bolt torque, NETA (National Electrical Testing Assoc.) has a chart for when you don't know the original manufacturer's values.
    http://tegg.teggpro.com/teggforms/2001netatables.pdf
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