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Have you/co-workers ever had to work closer to energizied equipment than the "working distance"?
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 Post subject: Being closer than the "working distance"
PostPosted: Sun May 20, 2012 12:08 pm 
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An arc flash calculation study requires calculating the incident energy at a specific working distance from the worker's face and chest to the prospective arc flash location. The working distance is typically listed on the arc flash label.

Here is this week's question:

Have you or your co-workers / clients ever had to work closer to energizied equipment than the "working distance"? (face and chest)
  • Yes
  • No
Stories about your own experiences are always welcome.

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PostPosted: Sun May 20, 2012 4:37 pm 
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This is a very good question. Although we try to minimize live work, when we do it, it is next to impossible to say we would never be closer than 18 inches or what ever distance was used in the study. A good example is connecting leads for testing. This not always easy with arms extended straight out to keep the correct distance.

I imagine we are not alone with this. Anyone else??


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PostPosted: Mon May 21, 2012 3:22 am 
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I would say that there is far more confusion about what the term "working distance" means than violators. Especially when we mark cabinets based on the upstream arc flash hazard potential where any work rarely needs to be done.


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PostPosted: Mon May 21, 2012 8:00 am 
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ANy one who has ever leaned in to read the (absurdly fine) print on a breaker has been closer than that. Any one who has connected any thing to equipment at the back of a cubiclel, has been closer than 18" from the front...


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PostPosted: Tue May 22, 2012 5:47 am 
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This is the issue I have with arc rated gloves, often I see them selected based on the Ei at the working distance when in fact they are much closer and therefore under protected.


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PostPosted: Tue May 22, 2012 12:56 pm 
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Zog wrote:
This is the issue I have with arc rated gloves, often I see them selected based on the Ei at the working distance when in fact they are much closer and therefore under protected.


What do you base the selection on? NFPA 70E only gives a general requirement to consider the higher Ei, but I find it hard to turn this into practical solution. Do you calculate for two working distances? Add a % on top of the regular ATPV?


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PostPosted: Wed May 23, 2012 11:07 am 
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Location: Roanoke Virginia area
brainfiller wrote:
An arc flash calculation study requires calculating the incident energy at a specific working distance from the worker's face and chest to the prospective arc flash location. The working distance is typically listed on the arc flash label.

Here is this week's question:

Have you or your co-workers / clients ever had to work closer to energizied equipment than the "working distance"? (face and chest)
  • Yes
  • No
Stories about your own experiences are always welcome.


Commissioning Drives, it is often required to reach beyond the drive front to get to some circuits on the back panel. This places the potential source of an Arc Flash incident at your chest and face. It is difficult to get older Field Engineers to keep in mind to maintain the "Working Distance" of 18" in our 480 Volt drive. Wearing PPE for the older FE's is a growing success... It is just a different mindset.


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PostPosted: Wed May 23, 2012 1:40 pm 
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jvrielink wrote:
What do you base the selection on? NFPA 70E only gives a general requirement to consider the higher Ei, but I find it hard to turn this into practical solution. Do you calculate for two working distances? Add a % on top of the regular ATPV?


Don't use them, we use rubber gloves with leather protectors


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PostPosted: Wed May 23, 2012 1:44 pm 
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Zog wrote:
Don't use them, we use rubber gloves with leather protectors
Our Field Engineers use PPE... My comment that the tasks required during commissioning brings your body closer than 18" (the design distance for effective PPE use) when reaching beyond the front of the drive cabinets... I did not intend to mean we were not using PPE...


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PostPosted: Thu May 24, 2012 8:46 am 
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Great comments everyone! I think this shows that although a working distance is needed to define the incident energy and/or protection, it is not always practical to adhear to. I hate to say it but in years past, I have had my face too close to energized parts on more than one occasion.

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