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Do you/clients/company still use 40 cal/cm^2 as the cut off for energized work?
Yes
Not anymore
Never used it
Depends
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 Post subject: Do you still use 40 cal/cm2 as the cutoff for energized work
PostPosted: Sun Feb 07, 2021 10:51 am 
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Joined: Mon Sep 17, 2007 5:00 pm
Posts: 1561
Location: Scottsdale, Arizona
The 2018 Edition of NFPA 70E eliminated the reference to de-energizing above 40 cal/cm^2.

That value of incident energy often triggered RED DANGER labels and energized work was prohibited. (although with few exceptions, energized work should always be avoided)

The justification for removal of this informational note was that all work should always be performed under electrically safe work condition not just above 40 cal/cm^2

When this change occurred in the 2018 edition, a question was raised: Would people still use 40 cal/cm^2 as the cutoff for not performing energized work.

Here is this week’s question:

Do you/clients/company still use 40 cal/cm^2 as the cut off for energized work?

Yes
Not anymore
Never used it
Depends

Please give us your thoughts - what do you use as a cutoff?


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 Post subject: Re: Do you still use 40 cal/cm2 as the cutoff for energized
PostPosted: Tue Feb 09, 2021 6:57 pm 

Joined: Fri Jul 10, 2009 10:14 am
Posts: 30
Location: West Central, OH
We drew a line at the 40 as it needed to be somewhere.


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 Post subject: Re: Do you still use 40 cal/cm2 as the cutoff for energized
PostPosted: Thu Feb 11, 2021 9:44 am 

Joined: Thu Feb 11, 2021 7:17 am
Posts: 2
Depends on the work to be performed.
Simply crossing the Arc Flash Boundary doesn't necessitate arc flash PPE. The other consideration (IAW 1910.269 Appendix E) is the "probability that an arc will occur".
For example, when performing thermal imaging, there is a reasonable argument regarding acceptable risk if there is no evidence of damage, the equipment is maintained, the technician remains outside of the MAD (yes I know it's a shock boundary), can not reach or fall into the MAD while holding conductive objects, etc.
Otherwise, if the risk of arc exists, then yes, we won't conduct work within the arc flash boundary when the calculated incident energy exceeds 40 cal/cm2 and the circuit parts are both energized and exposed.


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 Post subject: Re: Do you still use 40 cal/cm2 as the cutoff for energized
PostPosted: Wed Feb 17, 2021 6:33 am 
In Brazil, the safety standard NBR 16384 still considers that "no safe PPE exists for IE > 40cal/cm²".

Also, many companies in their internal standards consider the same, mostly because of the 130.7(C)(15)(c) table, even though they require analysis of incident energy.

I see that many companies and professionals here are not updated with the last standards of arc flash and use wrong or mixed up concepts.


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 Post subject: Re: Do you still use 40 cal/cm2 as the cutoff for energized
PostPosted: Wed Feb 17, 2021 8:08 am 

Joined: Thu Feb 11, 2021 7:17 am
Posts: 2
Cool.
NFPA 70E doesn't apply to power generation. It's more aligned with Subpart S and applies to power utilization.


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