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Thread: Traffic Signals operating at 110volts vs arc Flash!!!!!! who wants to talk?

  1. #1
    Join Date
    Feb 2018
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    Atlanta Georgia
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    Traffic Signals operating at 110volts vs arc Flash!!!!!! who wants to talk?

    Can anyone provide me factual evidence that an arc flash event has actually occurred within a traffic signal cabinet operating at 110volts and injured a certified traffic signal technician? I have 25 years in the field and have worked with 2 Dept. of Transportation agencies and have partnered with larger nearby agencies to have a total of 125years experience and no one has ever seen this occur within a signal cabinet. ARC FLASH not a simple case of a small tingle from touching a terminal strip. I have responses from Caltrans Cal. DOT, and Texas DOT that indicate they have never had an experience with ARC FLASH since their formation. I firmly believe this is a case of OSHA lumping everyone into one category and not understanding what traffic signal technicians actually do. Our wire coming from the meter is a 6awg stranded conductor terminating behind a lexan shield and then going directly into a breakered panel within our cabinet. We then convert to 14awg wiring from that point throughout our enclosure. If we are required to wear gloves and such we will no longer be able to feel the wiring that we are dealing with and that means we could potentially flash an intersection simply by trying to perform regular maintenance and thus be sued personally for any subsequent accidents that we cause. In Ga. we do NOT have sovereign immunity anymore meaning techs are sued first and foremost personally then the local govt. agency. I appreciate any answers I receive on this matte but please remember I am speaking about traffic signal technicians and the liabilities that wearing large gloves and such pose to them and face shields that will keep them from being able to adequately see areas within the cabinet and perform the JOB safely. my attached images show what a typical cabinet would look like that techs would have to trace individual wires on in order to troubleshoot and you can see with gloves that would prove nearly impossible. my examples are typically a before and after scenario..... they are NOT the exact same location

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  2. #2
    Join Date
    Dec 2007
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    I find it hard to believe there has never been an "arc flash". I do find it very likely that when there has been one the total incident energy level was low enough that there was little risk of severe injury to a worker.

    Arc flash and incidental contact are not the same thing either, your requirement to wear gloves probably is more for shock protection then arc flash protection. If you had high enough incident energy you would be wearing more then just gloves for arc flash protection.

  3. #3
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    Jun 2003
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    Hawthorne, New York NEC: 2014
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    I'm not sure exactly what you are asking. I've tried to read your post a few times, but without sentences, capitalization and paragraphs it's difficult to understand.

    What I assume you are asking is whether there have been any arc flash incidents involving traffic signal equipment. I would have to say probably yes, but they would have to be so small due to the 15 amp OCP that they would be inconsequential- if they would even qualify as an arc flash.

    Likely a problem with the #6 wiring to the main breaker however could be cause for concern, but you say that has a lexan cover.

    Other than that I'm not sure what you are asking. You wear gloves because you are working hot and there is a shock hazard. If you don't want to wear gloves, shut the cabinet down.

    -Hal

  4. #4
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    Dec 2012
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    Placerville, CA, USA
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    There is continuing controversy on the subject, but the majority opinion is that, in the absence of an unusual condition such as conductive material spray or melting of the metal of wires, it is not possible to have a classic arc flash at a voltage as low as 120 volt AC.
    There can be sparks and there can be local melting of wires and combustion of plastic or other materials, but no self-sustaining plasma cloud to carry an arc past the first half cycle.

  5. #5
    Join Date
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    Quote Originally Posted by GoldDigger View Post
    There is continuing controversy on the subject, but the majority opinion is that, in the absence of an unusual condition such as conductive material spray or melting of the metal of wires, it is not possible to have a classic arc flash at a voltage as low as 120 volt AC.
    There can be sparks and there can be local melting of wires and combustion of plastic or other materials, but no self-sustaining plasma cloud to carry an arc past the first half cycle.
    I agree with those that say 120 applications can't self sustain themselves.

    But do believe there is incident energy released even if only at low levels and for half a cycle, that incident energy may happen to be below certain specific PPE requirements though.

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