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 Post subject: As NEEDED! When to wear face shields if the hazard is below
PostPosted: Tue Mar 07, 2017 9:22 am 
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This is a follow up to my question about how you interpret the note found in Table H3(b) for when the arc flash hazard is less than 1.2 calories. The note says to wear a face shield as needed. Have any of you come up with some sort of guide or idea about what the NFPA 70E Table H3(b) means? This sounds like when NFPA says to use "increased emphasis on de-energizing" when the arc flash hazard exceeds 40 calories.

Any examples with your answers would be appreciated. BTW, I asked NFPA to explain what they mean. If I get an answer, I'll post it.
Thanks,


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 Post subject: Re: As NEEDED! When to wear face shields if the hazard is b
PostPosted: Mon Mar 13, 2017 9:15 am 
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AN (As Needed) usually means just that. When the AF energy is 1.2 Cal/cm2 or less, then a Face Shield is not required. However, you may need an face shield if you are working on batteries. A face shield would protect the face should a battery cell explode. This is one example and I am sure that there are others out there.

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 Post subject: Re: As NEEDED! When to wear face shields if the hazard is b
PostPosted: Mon Mar 13, 2017 11:06 am 
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Also, if a work procedure required a worker's face to get closer than the standard 18" working distance a face shield may be required.


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 Post subject: Re: As NEEDED! When to wear face shields if the hazard is b
PostPosted: Mon Mar 13, 2017 11:20 am 
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Hello All,
I got a reply from NFPA on the "as needed" question. They said to refer to 110.1 G for risk analysis. I can sort of understand them pointing to that part of the Standard, but it seems like a stretch to put the statement about face shields in Table H3(b).


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 Post subject: Re: As NEEDED! When to wear face shields if the hazard is b
PostPosted: Mon Mar 13, 2017 11:27 am 
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RogerF wrote:
Also, if a work procedure required a worker's face to get closer than the standard 18" working distance a face shield may be required.


That is true, if you work closer that 18", then the arc flash will be higher. The person would have to recalculate the energy at this closer working distance to determine if the energy is greater than 1.2 Cal/cm2. If it is greater, then arc-rated balaclava will need to be worn as well. However, both the arc flash face shield and balaclava hood can be replaced by wearing and Arc Flash Hood.

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 Post subject: Re: As NEEDED! When to wear face shields if the hazard is b
PostPosted: Tue Mar 14, 2017 11:19 am 
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The working distance is a bit tricky because ergonomic studies show 15" is kind of the "ideal" distance from the area your hands are at to the chest area. Then there was some sort of hand waving about the distance projected upwards towards the chest/face area away from the plane where your hands are at (roughly bench height). And it's the distance from the potential location of the ARC at the rear of the enclosure, NOT from the face of the enclosure. In most cases such as MCC's that are nominally about 20" deep, 18" is roughly to the plane of the front door. So it's kind of unusual to be less than 18" under most circumstances with MCC's for instance. But I'm a maintenance guy. I can't tell you how many times I've had to stand on my head, wiggle my body back into a hole/corner somewhere, etc. The problem then becomes...how can you develop any kind of rules where you aren't spending your entire time trying to figure out what you can and can't do and how...so how do we deviate from the "standard distance" without getting into a huge morasse where the work rules become impossible?


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