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 Post subject: Six questions about Arc Flash Compliance and Analysis
PostPosted: Thu Apr 24, 2008 12:53 pm 
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Here are six questions about Arc Flash Compliance and Analysis. Please comment.

1. Is PPE required to pull a simple disconnect switch to de-energize an enclosure with the cover closed?

2. After an enclosure is de-energized by pulling the disconnect, is PPE required to test and verify the absence of voltage?

3. Pulling the disconnect switch on an enclosure de-energizes all the downstream circuits inside the enclosure. The incoming power to the switch contacts are still live. Therefore, Is the enclosure considered to be still energized or is it de-energized? How do other companies handle this problem?

4. Are gloves required for Hazard Categories 0 and 1? NFPA 70E Table 130.7(C)(10) is not clear regarding use of gloves for Hazard Categories 0 and 1. Are gloves required for shock hazard, even if they are not required for Arc Flash Hazard? If so, what type of gloves are acceptable for shock hazards?

5. Installing or replacing Bus Plugs on an energized Busway. I assume this is an example of live work requiring a work permit. Some people may disagree. Please provide clarification.

6. Do you know how other companies handle 480 Volt arc welders for their Arc Flash Study? We have a significant number which may affect our results.


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PostPosted: Thu May 08, 2008 2:03 pm 
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Joined: Thu Jan 10, 2008 8:49 pm
Posts: 480
Location: New England
I'll take a stab at some of them.


1. Is PPE required to pull a simple disconnect switch to de-energize an enclosure with the cover closed?

NO, Arc Flash is about working on or near exposed live parts. Behind closed metal covers nothing if required. However, some areas of the PPE risk table have PPE requirements for working with covers in place. But I think the general consensus is that behind a metal cover, Arc Flash does not apply.

2. After an enclosure is de-energized by pulling the disconnect, is PPE required to test and verify the absence of voltage?

I would say YES. Disconnects sometimes fail and the blades do not fully open and disconnect. You should never assume power is off until its verified with a voltmeter. The assumption has to be that power is present until proved otherwise, so you need PPE for the verification.

3. Pulling the disconnect switch on an enclosure de-energizes all the downstream circuits inside the enclosure. The incoming power to the switch contacts are still live. Therefore, Is the enclosure considered to be still energized or is it de-energized? How do other companies handle this problem?

This depends on the distances but under most conditions I would say it is live. If you could install a isolation barrier and guard around the incoming lugs then you could make an arguement for no PPE. The concern here is that you could inadvertantly touch the live lugs. If you are working outside of the Restricted Approach, if I remember 12"@480V then you could do the work without PPE. But voltage checking to verify disconnect worked would be in PPE.

4. Are gloves required for Hazard Categories 0 and 1? NFPA 70E Table 130.7(C)(10) is not clear regarding use of gloves for Hazard Categories 0 and 1. Are gloves required for shock hazard, even if they are not required for Arc Flash Hazard? If so, what type of gloves are acceptable for shock hazards?
NFPA only goes down to Class 0 (1000V) gloves but I think ANSI and OSHA recognize Class 00 (500V) gloves. I think 500V is as low as it goes. There is also an allowance to work with gloves one class higher than required without the leathers, but then the gloves have to be tested before being used again. I also remember gloves being required within the Restricted Approach barrier, you can check the table for the distances.


5. Installing or replacing Bus Plugs on an energized Busway. I assume this is an example of live work requiring a work permit. Some people may disagree. Please provide clarification.

NFPA doesn't give you tasks for needing the Live Work. It provides allowance for long term standing permits (NFPA uses the example of 3 months) for routine live work. This would be part of your training policy. You decide what is routine versus what isn't. For example, I require permits for 1) hands or tools touching live bus 250V or greater, 2) inserting or removing MCC buckets or switchgear breakers, 4) all work above 601V. But we can do without permits (or use our standing permit) change fuses, voltage checks, install remove snap in breakers, land wires to "off' breakers and MCCs. You need a policy and to define when the permit is needed. I use 12 months for my standing permit duration, and then we require a refresher course for the electricians.

6. Do you know how other companies handle 480 Volt arc welders for their Arc Flash Study? We have a significant number which may affect our results.

Are you talking about the actual arc created when welding. If yes, then Arc Flash doesn't apply. Arc Flash is about preventing accidental injury caused by arc flashes from electric shorts, not from welding. Follow your normal wleding safety guidelines.

Message me if you want to go over anything specific or if I can help you with you getting your program started.


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PostPosted: Mon Jun 02, 2008 1:02 pm 
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Joined: Mon Jun 02, 2008 11:58 am
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Location: Charlotte, NC
OK, here are some other answers

Arc Flash Don wrote:
Here are six questions about Arc Flash Compliance and Analysis. Please comment.

1. Is PPE required to pull a simple disconnect switch to de-energize an enclosure with the cover closed?

Depends on the amp-cycles and class of switch, yes you need PPE, what level depends on the switch type and system charteristics. Unless it is arc rated switchgear, then no PPE required.

2. After an enclosure is de-energized by pulling the disconnect, is PPE required to test and verify the absence of voltage?

Yes, and the meter needs to be verified on a know live source, and possibly protective grounds installed, then you can relax PPE.

3. Pulling the disconnect switch on an enclosure de-energizes all the downstream circuits inside the enclosure. The incoming power to the switch contacts are still live. Therefore, Is the enclosure considered to be still energized or is it de-energized? How do other companies handle this problem?

Haze answered this pretty well, this is being discussed by 70E task force right now, newer equipment is being made with "arc safe" barriers for the live parts, but jury is out on how to handle older equipment. You can use arc flash suppression blankets for this.

4. Are gloves required for Hazard Categories 0 and 1? NFPA 70E Table 130.7(C)(10) is not clear regarding use of gloves for Hazard Categories 0 and 1. Are gloves required for shock hazard, even if they are not required for Arc Flash Hazard? If so, what type of gloves are acceptable for shock hazards?

Table 130.7(C)(10) has nothing to do with shock hazards, rubber gloves rated for the voltage levelk involved are always required when crossing the RAB.

5. Installing or replacing Bus Plugs on an energized Busway. I assume this is an example of live work requiring a work permit. Some people may disagree. Please provide clarification.

Not live work, treated just as racking in a circuit breaker, but as you know is more difficult and has higher risks involved, expect to see bus plugs added top the tables for 2009 revision (See ROP on NFPA website for details)

6. Do you know how other companies handle 480 Volt arc welders for their Arc Flash Study? We have a significant number which may affect our results.
Depends on the saftware you are using




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