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 Post subject: Working Distance and Hands?
PostPosted: Sun Jul 22, 2007 8:36 am 
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It looks like the calculations are based on the body being some distance away from the arc. i.e. working distance. What about the hands and arms? It looks like this could be a problem since the incident energy becomes much worse the closer you get.


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PostPosted: Tue Jul 24, 2007 9:05 am 
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Yes you might not play the piano again. I understand the concern is survival and they have to draw the line somewhere. Incident energy varies as the inverse square of the distance from the arc so the closer you get, the problem grows exponentially. 70E just makes a statement about parts of the body closer to the arc might need additional protection and recommends leather glove protectors. Perhaps a PPE manufacturer such as Salisbury or Oberon might have something better.


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PostPosted: Sat Aug 11, 2007 4:33 pm 
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The distance issue is why remote racking of breakers is a good idea. I keeps you out of the "line of fire" in case there is an event while racking in the breaker. Same idea with hot sticks. Put as much distance between you and the potential arc flash source.


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PostPosted: Tue Nov 20, 2007 8:48 am 
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basspro91 wrote:
It looks like the calculations are based on the body being some distance away from the arc. i.e. working distance. What about the hands and arms? It looks like this could be a problem since the incident energy becomes much worse the closer you get.


It seems that most of the PPE, for which the calcs are designed, focuses on the body trunk and face etc. which would be at the working distance from arc source. The arc blast suits do not always include gloves and it seems leather gauntlet gloves are a common practice. By its own disclaimers the intent of NFPA is to reduce burns not eliminate them. I suspect that if working distance is measured to the hands (on 480V gear which often has exposed conductors near the front) the PPE will become very restrictive.

(just some observations and opinions)

Gary B


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PostPosted: Mon Jan 07, 2008 7:59 am 
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Good FR Gloves?

Does anyone have any experience with gloves that have a good FR rating and that allows you to do the work without making things too difficult? NFPA 70E references leather protectors etc. but have gloves gotten better?

Thanks!


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PostPosted: Mon Jun 02, 2008 8:30 pm 
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Greg Cross wrote:
Does anyone have any experience with gloves that have a good FR rating and that allows you to do the work without making things too difficult? NFPA 70E references leather protectors etc. but have gloves gotten better?

Thanks!


Rubber gloves with leather protection offer all the arc flash protection you would ever need, problem is there is not an ASTM standard for establishing a rating for rubber gloves and leather protectors because too much depends on the condition and cleanliness of the leather.

See Jims post in this section for more info on the estimated ATPV of rubber gloves alone.


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