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ekstra   ara
 Post subject: Live Work
PostPosted: Thu May 12, 2011 7:17 am 
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Joined: Thu Feb 24, 2011 3:36 am
Posts: 13
Hello All,

If you are working in a panel, do you have to de-energize the incoming electrical wires if they are protected by an arc flash guard?

Thank you


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PostPosted: Mon May 16, 2011 5:45 am 
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Joined: Tue Feb 24, 2009 7:05 am
Posts: 252
What do you call "arc flash guard"? A plastic shock guard, or a 1/2" bolted piece of steel?


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PostPosted: Mon May 16, 2011 6:21 am 
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Arc Flash guard

Plastic shock guard

Thanks


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PostPosted: Mon May 16, 2011 8:06 am 
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Joined: Mon Mar 29, 2010 11:52 am
Posts: 110
Location: Yankton SD/ Lead SD
A "plastic shock guard" is not an "arc flash guard". I would de-energize.


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PostPosted: Mon May 16, 2011 9:05 am 
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Thank you. I agree with de-energizing.

Another question:

What is the reason I give my electricans on why the plastic shock guard is not enough protection? They insist they can not cause an arc with the guard.

Thanks again


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PostPosted: Mon May 16, 2011 9:52 am 
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Joined: Wed Oct 29, 2008 6:06 am
Posts: 136
Location: Michigan
Line Side of Disconnect

There is an [url="http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=INTERPRETATIONS&p_id=25438"]OSHA letter of interpretation[/url] on this subject; while this letter pre-dates the new definition of the AFPB in the '09 edition of 70E, it still works for meeting the requirements of lockout and shock protection.

For the purposes of lockout and shock protection, we allow an electrical panel to be considered de-energized, even though there is voltage to one side of the open disconnect, if the design of the equipment is of finger-safe construction. The design must prevent, through physical guarding, accidental contact of an associate or conductive objects with energized parts. If the panel does not prevent accidental contact, the panel must be de-energized at an upstream/lockable disconnect.

We had a guarding initiative a while back and ordered a bunch of new line side terminal guards for the Allen Bradley 1494 series D and newer disconnects (part# 1495-N80, N81 & N82 - the old style terminal guards were insufficient). This enabled us to not require rubber insulating gloves inside the panel or lockout at the bus switch and our standard daily wear (HRC 0) meets the PPE requirements for the arc flash hazard in these panels.


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PostPosted: Mon May 16, 2011 10:08 am 
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Thank you for the help


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PostPosted: Fri May 20, 2011 5:36 am 
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A question regarding A King's response:
Does an employee have to wear PPE when working in a panel that is verified to be de-energized, but has a live guarded supply side?

Thanks for the help


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PostPosted: Mon May 23, 2011 7:51 am 
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Joined: Wed Oct 29, 2008 6:06 am
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Location: Michigan
The 2004 definition the AFPB was defined as "a distance from exposed live parts" - no arc flash or shock protection PPE was required for the situation being discussed then. However, the 2009 definition of the AFPB is now defined as "a distance from a perspective arc source" - meaning that although there is no shock hazard, an arc flash hazard still could be present.

A plastic guard will not protect you if an arc flash event occurs; however, it may prevent accidental contact from causing an arc flash incident, but this is not the only way an arc flash event can be triggered... (failure of insulating materials, dust, impurities, corrosion, mechanical malfunction, over-voltages across narrow gaps, etc.).

The panels in which we implemented a more robust line side terminal guard all fell into HRC 0 and the AFPB is small. So yes, our standard daily wear is appropriate PPE for this arc flash hazard (long-sleeved, non-melting, flammable clothing), but we do not require gloves or lockout at the bus due to the finger-safe construction of the line side terminal guards. We feel that both the probability and severity of injury from arc flash in these panels is too low to warrant use of leather gloves in this situation and rubber gloves are not required since there is no shock hazard.

In a panel with a higher IE, that may be another story...


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