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 Post subject: Plant Engineering "Arc Flash University"
PostPosted: Fri May 29, 2009 6:42 am 
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Joined: Fri May 29, 2009 6:23 am
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Location: Ontario, Canada
Has anyone participated in one of these webinars? There was one yesterday discussing the 2009 changes to NFPA 70E. Greg Foust from GE was the presenter. He made a couple of statements that I'm interested in getting some feedback on.

1. Door latches on equipment can't be counted on to hold the door closed during an Arc Flash Event.

2. Once you have done an Arc Flash study, you can still use the NFPA table to select PPE for work where all doors are securely closed and fastened. Greg stated that NFPA officials have indicated that Arc Flash calculations are based on exposed electrical hazards only.

I'm only paraphrasing here and don't mean to speak for someone else, just looking for opinions.

Statements 1 and 2 seem to contradict each other. I've read all I can find on this forum about what PPE is required for operating an MCC disconnect with doors closed. I tend to agree that the worker should wear the PPE identified on the Arc Flash label.

Does anyone care to add their two cents?


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PostPosted: Fri May 29, 2009 9:19 am 
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Location: Charlotte, NC
SueLIC wrote:

1. Door latches on equipment can't be counted on to hold the door closed during an Arc Flash Event.


Agreed

SueLIC wrote:
2. Once you have done an Arc Flash study, you can still use the NFPA table to select PPE for work where all doors are securely closed and fastened. Greg stated that NFPA officials have indicated that Arc Flash calculations are based on exposed electrical hazards only.


I disagree with this. Once you ID the hazard level with the analysis you cant use less PPE based on the task tables. Mixing of calcs and tables are a big no no as I understand.

SueLIC wrote:
Statements 1 and 2 seem to contradict each other. I've read all I can find on this forum about what PPE is required for operating an MCC disconnect with doors closed. I tend to agree that the worker should wear the PPE identified on the Arc Flash label.
I agree 100% on both points here.

SueLIC wrote:
Does anyone care to add their two cents?

I think that was 3 cents


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PostPosted: Fri May 29, 2009 11:22 am 
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Joined: Fri Jan 16, 2009 1:07 pm
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Location: North Florida
I 'attended' the same webinar and heard the same thing. I think his point is that in 70E, the 'rules' are written for exposed energized conductors. There are members of the committee (and others) that feel that, since the doors often will not fully hold back an arc flash, the rules should apply doors open or closed. But the application of 70E is for exposed energized conductors. Otherwise we could extrapolate that the cable insulation will not contain an arc flash and therefore we must label all cable and cable tray as to the hazard and wear PPE whenever we cross the arc flash boundary. Similarly, anyone entering an MCC room would need to be clad in FR PPE when performing a lockout. These are pretty much unworkable solutions and don't really provide the additional protection relative to the risk.

The table provides guidance for door closed activities such as switching activities and what the speaker was suggesting was that since the analysis was for exposed conductors, that the tables could be used for the other activities where the analysis did not apply. I personally think that this is a very good solution to the whole open/closed door issue.

That's my 2 cents worth.

TxEngr


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PostPosted: Tue Jun 02, 2009 1:58 pm 
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Since we cannot protect you against everything, protect you against the obivous. I know that doors do not hold by personal experience (one sending me to the hospital) but arc flash protection begins with prevention. Very little attention is paid to electrical equipment maintenance and almost every arc flash I have investigated involved some form of equipment/operator malfunction (leaving out the occasional snake or varmant).

Greg was technically correct in that is reads you can use either method but who would go to all the trouble to do an arc flash study (and expense) and then change methods unless they are trying to cut corners on PPE costs.

And indeed the study was done on the energy of exposed conductors, that is why 2009 addresses the openings in switchgear that are going to blow out during the arc flash. A LOT of 480 volt switchgear (ie old GE gear) has to have the doors open to rack and unrack the breaker.

Bottom line, unless management is fully involved in protecting employees from ARC Flash, the employee has to be the one to make sure that they stay safe. To do that requires training, equipment and common sense (and maybe the commitment to walk off the job if it is too dangerous)


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