It is currently Fri Aug 12, 2022 2:44 am

Author Message

 Post subject: Flash boundary distancePosted: Mon Jun 15, 2009 5:52 pm

Joined: Thu Jun 11, 2009 12:38 pm
Posts: 33
Location: Kansas city
Jim,

In your article published in NEC digest in august 2007 "How to perform an arc-flash study in 12 step", you've recommended standardizing the flash boundary distance to six feet for live work. I can't seem to understand how can one work on a piece of equipment 6 feet away? (when I say work I mean racking in breakers or any other maintenance operation)
I know remote controlling of breaker racking is feasible at much larger distances. But I am sure this method of operation is pointless at just 6 feet.

I've learned quite a bit from this article and I appreciate your contribution. For those oblivious of the article, I've attached the links.

[url="http://www.brainfiller.com/documents/ArcFlashJimPhillipsPart1.pdf"]Part 1[/url]

[url="http://www.brainfiller.com/documents/ArcFlashJimPhillipsPart2.pdf"]Part2[/url]

[url="http://www.brainfiller.com/documents/ArcFlashJimPhillipsPart3.pdf"]Part 3[/url]

I welcome comments from other members as well.

Thank you,
Aleen

Top

 Post subject: Posted: Mon Jun 15, 2009 8:13 pm
 Arc Level

Joined: Wed Jun 04, 2008 9:17 am
Posts: 428
Location: Spartanburg, South Carolina
My interpretation is that if the calculated arc flash boundaries are all less than 6 feet, simplify by using 6 feet everywhere. This doesn't mean you can't work at a distance less than 6 feet, only that you are required to use appropriate PPE when you do.

For instance, at one piece of equipment, the IE at the working distance may be 7 cal/cmÂ² and the arc flash boundary 4 feet. At another piece of equipment, the IE may be 23 cal/cmÂ² and the arc flash boundary 5'-4". You would simplify by requiring PPE whenever you are interacting with either piece of equipment within 6' of it. On the first, you would use Cat 2 PPE (8 cal/cmÂ²) and on the second you would use Cat 3 PPE (25 cal/cmÂ²).

Top

 Post subject: Posted: Tue Jun 16, 2009 6:18 am

Joined: Thu Jun 11, 2009 12:38 pm
Posts: 33
Location: Kansas city
Now that makes sense. Thanks for the interpretation.

Aleen

Top

 Post subject: Posted: Tue Jun 16, 2009 6:28 am
 Sparks Level

Joined: Mon Nov 10, 2008 1:08 pm
Posts: 60
Location: Cincinnat, OH
The question begs a definition.......What exactly is the Arc-Flash Protection Boundary? When an arc flash hazard exists it is the approach boundary within which a person could receive a second degree burn if an arc flash were to occur. Right now this boundary is a calculated value and is different for every piece of equipment in a facility. By standardizing the boundary you are taking confusion out of when to put on PPE since it is the same distance at every piece of equipment.

Be careful though I would do an either or case....the boundary should be set to 6ft like suggested or farther if calculations lead to farther distances.

Top

 Post subject: Posted: Tue Jun 30, 2009 10:03 am

Joined: Fri Sep 05, 2008 8:10 am
Posts: 36
Not to hijack the thread.....but here goes.

Does anyone actually use the 4 different approach distances indicated in 70E. From my limited involvement with AF studies(<=480V) the arc flash boundary is much farther away from the equipment than the shock protection distances. Do people actually enter the arc flash boundary wearing the required AF PPE without shock protection as required by limited approach distance? If so, what does this gain?

Top

 Post subject: Posted: Wed Jul 01, 2009 7:11 am
 Plasma Level

Joined: Mon Sep 17, 2007 5:00 pm
Posts: 1662
Location: Scottsdale, Arizona
amohammed wrote:
Jim,

In your article published in NEC digest in august 2007 "How to perform an arc-flash study in 12 step", you've recommended standardizing the flash boundary distance to six feet for live work. I can't seem to understand how can one work on a piece of equipment 6 feet away? (when I say work I mean racking in breakers or any other maintenance operation)
I know remote controlling of breaker racking is feasible at much larger distances. But I am sure this method of operation is pointless at just 6 feet.

Wow, this thread slid right on by me - sorry. Here is what I meant by standardizng.

The Arc Flash Protection Boundary defines the minimum distance from a prospective arc flash where you need to wear PPE when an arc flash hazard exists. Over the years I have heard many people get excited about having different boundaries for each location based on the results of the arc flash calculation study. The concern is confusion.

Since the boundary applies more to those that are not properly protected, my take is if you are not performing the work and wearing appropriate PPE then just get out of the way. Splitting hairs over where the unprotected person must be i.e. 3 ft, 4ft, 5 ft, etc. makes this more complicated than it needs to be - just have the non protected people stay out of the way.

Of course there could be exceptions to this such as needing a helper close by but not standing within the AFPB. But.... if something goes wrong and the unprotected helper needs to rescue you during an arc flash, it could be quite bad.

What many people have been doing is adopting a standardized AFPB based on the largest (within reason) one from the study. This could mean 6 or 8 feet everywher. Combine this with using a 2 level PPE approach and you have a much simpler program. Again, the large AFPB should not affect the protected person doing work, it only affects the unprotected person by keeping them out of the way. Also keep in mind, we don't know everything (not even close) about how the arc flash acts. Last week I threw a bus bar (it was placed on the two stabs of a pad mounted transformer) about 20 feet with only 15 kA of arcing current at 480/277V. That's well beyond the AFPB.

Hope it helps!

_________________
Jim Phillips, P.E.
Brainfiller.com

Top

 Display posts from previous: All posts1 day7 days2 weeks1 month3 months6 months1 year Sort by AuthorPost timeSubject AscendingDescending
 Page 1 of 1 [ 6 posts ]

 All times are UTC - 7 hours

 You cannot post new topics in this forumYou cannot reply to topics in this forumYou cannot edit your posts in this forumYou cannot delete your posts in this forumYou cannot post attachments in this forum

 Jump to:  Select a forum ------------------ Forum Library / Articles The Lounge    Question of the Week - What Do You Think?    Arcflashforum.com Feedback and Announcements    Off Topic Discussions    News in Electrical Safety Arc Flash and Electrical Safety    General Discussion    Electrical Safety Practices    Equipment to Reduce Arc Flash Dangers    Personal Protective Equipment (PPE) Arc Flash Studies    General Discussion    Arc Flash Labels    Software for Arc Flash Studies    System Modeling and Calculations    NEW! Electrode Configuration Library – 2018 IEEE 1584 Codes and Standards    CSA Z462 Workplace Electrical Safety    EAWR Electricity at Work Regulations, HSE - Europe    OSHA CFR Title 29    IEEE 1584 - Arc-Flash Hazard Calculations    NFPA 70 - National Electrical Code - NEC (R)    NESC - ANSI C2 - National Electrical Safety Code    NFPA 70E - Electrical Safety in the Workplace    2015 NFPA 70E Share It Here    Arc Flash Photos    Your Stories    What's Wrong Here? by Joe Tedesco
© 2022 Arcflash Forum / Brainfiller, Inc. | P.O. Box 12024 | Scottsdale, AZ 85267 USA | 800-874-8883