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 Post subject: What maintenance procedures lead to an arc flash?
PostPosted: Fri Jan 13, 2012 8:58 am 
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Hello, everyone. I'm researching a short, introductory course on the hazards of arc flash (and electricity in general). We use virtual 3D sets and characters to illustrate safety concepts. We've modeled an MCC and I'm trying to determine what's a good maintenance/repair procedure I can show our "worker" doing that leads to the arc flash. I know there must be some very common maintenance procedures that are associated with an arc flash occurrence, but I haven't been able to find what those are. Any suggestions would be greatly appreciated!

And if there's any very specific examples of how the arc fault occurs (between what two parts) that would also be extra appreciated.

Here's a link to our virtual MCC if anyone is interested (still under construction and we are making some small changes to it at the moment.)

[url="https://twitter.com/#!/Better_Training/status/156410790147145730/photo/1"]https://twitter.com/#!/Better_Training/status/156410790147145730/photo/1[/url]


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PostPosted: Fri Jan 13, 2012 10:46 am 
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Bucket removal/insertion would be the most common task and cause of arc flash incidents in MCC's.

Case study 2 on this PPT covers one specific incident involving a MCC.
http://cbsarcsafe.com/downloads/EPRI-presentation-on-remote-racking-and-switching-for-arc-flash-mitigation.pdf


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PostPosted: Fri Jan 13, 2012 11:08 am 
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That's an idea. I'm currently thinking we'll show someone racking a breaker. Maybe your idea is better.

Regarding showing the racking of a breaker, I'm currently unsure whether you can show someone racking a breaker in a smaller, individual bucket, or whether it always would be done in a larger "switchgear" type of panel.


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PostPosted: Fri Jan 13, 2012 11:18 am 
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Zog wrote:
Bucket removal/insertion would be the most common task and cause of arc flash incidents in MCC's.

Case study 2 on this PPT covers one specific incident involving a MCC.
http://cbsarcsafe.com/downloads/EPRI-presentation-on-remote-racking-and-switching-for-arc-flash-mitigation.pdf


Oh, and thanks a lot for that pdf. Very good stuff!


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PostPosted: Fri Jan 13, 2012 6:42 pm 
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Dropping an uninsulated tool in an energized panel.

Inserting a circuit breaker into a panelboard while live.

Basically, any time you are making 'live" circuit changes intentionally or unintentionally.


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PostPosted: Tue Jan 17, 2012 4:58 pm 
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I know you should de-energize whenever possible, but I understand it's not always possible. Are there certain industries that are known for having to do a lot of live work? Do you know what some of those industries are?


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PostPosted: Wed Jan 18, 2012 4:55 pm 
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ConvergenceTraining wrote:
I know you should de-energize whenever possible, but I understand it's not always possible. Are there certain industries that are known for having to do a lot of live work? Do you know what some of those industries are?


Chemical plants like to incorrectly use the "continuous process" clause in 70E incorrectly. The term is meant to cover large systems where shutting down one component would fall under the greater hazard clause but the component under consideration which would by itself not invoke the greater hazard clause can invoke it indirectly.

Mining companies often have problems with both shock and arc flash incidents. The fatalities for the entire industry are documented in the U.S. There is a large prevalence of both environments where the equipment is frequently subject to mechanical damage, plus moisture and dust, and where medium and higher voltages are in routine use. So you have laborers routinely unplugging large P&L plugs operating at 4160 or 13.5 (or he infamous 995 V) who fail to shut off the disconnects. They can frequently get away with it because by law everything in an underground and/or coal mine must have a ground check circuit in place which shuts off power if they stupidly do so. Plus it is not uncommon to go into panels while live. Sometimes this is legitimate too. Underground mines MUST maintain ventilation and frequently dewatering. There is little leeway on this, but there are ways other than 100% live to achieve it and if pressed, they suddenly find ways to get there.

The whole utility industry frequently works on equipment live. They don't even have the "greater hazard" clause. The rules are written under almost the assumption that all work will be done live. The reason given is reference to an unknown, undocumented "greater hazard" of a customer.

Hospitals are also notorious for this.

Glass plants and coking plants have a problem where shutting down power can be disastrous. They are intentionally designed with redundancy well beyond double ended subs, usually with their own backup generators.

I'd lump steel mills and paper mills into this too but some do and some don't. It all depends on whether as with hospitals, whether production trumps safety or not since there is no absolute dire requirement for 24/7 operation.

An up and coming one is data centers. Telecoms also frequently work on everything live, whether or not it is low voltage.


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PostPosted: Thu Jan 19, 2012 11:03 am 
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Thanks again, Paul. Great, informative stuff. Do you have a personal or company website by chance?


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PostPosted: Fri Jan 20, 2012 4:34 am 
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ConvergenceTraining wrote:
Thanks again, Paul. Great, informative stuff. Do you have a personal or company website by chance?


No.

I'm not a full time safety consultant. I'm the electrical engineer for a large mine. It's nonunion so I carry my own tools, and I've also worked as an electrician for another mine in the past (small operation, electrical department size = 1).

This means that it is my responsibility to determine, articulate, and inspect safe work practices for electrical work. I don't do it alone (we have various intraplant and interplant groups, as well as participation in various professional groups).

I have to be able to not only have a thorough working knowledge of the subject matter from an engineering point of view but be able to articulate it to both unskilled and skilled craftsmen every day. Trust me, they don't care about the equations in IEEE 1584. It makes me come across as being better than them if I say "trust me, I work the equations and give you the answers. Never mind how I came up with them." This erodes me credibility. They want to have a working understanding of what they are doing, why they are doing it, and how to do it safely. Most of the guys I work with might be considered red necks, but red necks are not stupid.


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