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 Post subject: Arc Flash Hazard Labels on Buss Drops?
PostPosted: Mon Nov 03, 2008 12:22 pm 
Sparks Level

Joined: Wed Oct 29, 2008 6:06 am
Posts: 136
Location: Michigan
We are just beginning an arc flash analysis and using EasyPower software to generate hazard labels. I work in a manufacturing facility and we have many 480 volt, 30 amp (and some 60 amp) buss drops. If we place an arc flash hazard label on the drop it will specify PPE category 0 which requires non-melting, flammable materials (i.e. untreated cotton).

All of our electrician’s uniforms are made of natural cotton; however, all of the other shop associate’s uniforms are not. Does this mean that nobody may plug and unplug these buss drops used for portable welders, conveyors and other secondary equipment unless we change the uniform policy for everyone? Is it even required to put arc flash hazard labels on 480 volt, 30 amp buss drops? The drops are a disconnecting means and are energized while plugging and unplugging.

According to NEC 110.16 I think perhaps not.
110.16 Flash Protection. Switchboards, panelboards, industrial control panels, and motor control centers in other than dwelling occupancies, that are likely to require examination, adjustment, servicing, or maintenance while energized, shall be field marked to warn qualified persons of potential electric arc flash hazards.

However FPN 1 refers you the NFPA 70-E which in states:
NFPA-70E 130.3 A flash hazard analysis shall be done in order to protect personnel from the possibility of being injured in an arc flash. The analysis shall determine the Flash Protection Boundary and the PPE people within the boundary shall use.
NFPA-70E 130.7(E) Safety signs, safety symbols, or accident prevention tags shall be used where necessary to warn employees about electrical hazards that might endanger them.


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PostPosted: Mon Nov 03, 2008 1:57 pm 
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Joined: Mon Jun 02, 2008 11:58 am
Posts: 1103
Location: Charlotte, NC
A King wrote:
The drops are a disconnecting means and are energized while plugging and unplugging.


Right, and there is an arc flash hazard for that task. This should be done only by qualified personel waering the proper PPE.


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PostPosted: Thu Nov 13, 2008 10:20 am 
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Joined: Wed Oct 29, 2008 6:06 am
Posts: 136
Location: Michigan
I'm not sure what you mean; right as in, the NEC does not include receptacles and buss drops in article 110.16 therefore a hazard label is not necessary? Or do you mean right as in, the NFPA-70E requires an analysis be done and labels used where there may be a hazard (meaning everything over 50V).

So if my fabricator is not a qualified electrical worker and he must bring his portable welder out to the production line he must call an electrician to plug it in for him because the receptacle specifies hazard/risk category 0?

I can not find a task for disconnecting 480V cord and plug connected equipment in the NPFA-70E Table 130.7(C)(9)(a).


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PostPosted: Thu Nov 13, 2008 8:39 pm 
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Joined: Thu Jan 10, 2008 8:49 pm
Posts: 498
Location: New England
If the welder is trained in how to install and remove the drops in the bus duct, and it is truely a plug and play setup, then you can just have the welder in the proper PPE. You would have to give him Arc Flash training. But you don't necessarily need an electrician.


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PostPosted: Sun Nov 16, 2008 3:25 am 
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Joined: Wed Oct 29, 2008 6:06 am
Posts: 136
Location: Michigan
The welder will not install and remove drops; just simply plug the male plug on his welder into the female connector from the buss drop and unplug it when he is done.

If I do an arc flash analysis and place a hazard label on the buss drop it will specify HRC 0 which means the fabricator must be in non-flammable clothing or call an electrician. I want to avoid this because there is a lot of secondary equipment which is cord and plug connected. Must there be an arc flash hazard label on this female plug?


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PostPosted: Mon Nov 17, 2008 9:00 am 
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Joined: Thu Oct 18, 2007 7:10 pm
Posts: 261
Location: NW USA
Are the 480V drops plugged in and disconnected hot? Some receptacles are not rated as disconnect devices and have an adjacent switch, others are rated as disconnect (i.e.: Meltric brand pin and sleeve) and have a interupting mechanism within.

There might be a concern about plugging in and disconnecting 480V circuits that are energized depending on the equipment.

Gary B


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PostPosted: Sun Aug 30, 2009 7:22 am 
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Joined: Sun Aug 16, 2009 8:42 am
Posts: 184
Location: Lawrenceburg KY
As the process may not create a significant arc flash to say if using a 30 amp current limiting fuse in the busway fused busplug switch.

I have seen several problems with the SO cord type material and a four prong welding plug hanging from your busway's fused switch. First, you should never use such a plug for any AC motor without using a special plug type as mentioned above.

I have 30 years field experience and have seen many issues with these type of so called welding receptacles.
1) Frequent maintenance checks should be made by disassembling both male and female plug and inspect the connections and the ground connection.
I had a plug several years ago in which the ground wire came off the welders plug. This may have been unnoticed for years not sure. But the problem was found when the person welding was electrocuted. He survived. The plugs ground was already unknowingly off, now one phase of 480v shorted to the ground wire inside the plug. This made the welder frame the same potential as an exposed 480v connection. The welder was leaning on a grounded part when he went to adjust the welder. That was the last thing he remembered.
I have seen many cases similar to this that created accidents. So beware.

Recently I see a person’s hand was lightly burned as he tried to get a portable part of equipment to work off such a plug. The plug was fed from a fused safety switch, however the equipment was not working and the operator was jerking on the plug and wiring when one 480v phase wire came off and grounded out on the plug while his hand was on the plug.

We inform equipment operators they must turn off the fused safety switch before plugging in the device. That does not always happen but that is our procedure.

I recommend install a fused safety switch at floor level for all 3 phase 480 volt service receptacles and install low peak fusing. And set up a good PM program for plug inspection. I would set up to inspect at least once a year.

I have seen a lot of accidents involving such plugs. Not as much AF hazard but shock hazard.

A lot depends on the type of plugs you’re using. But never plug in a three phase 480 plug in hot but if you must I would make a requirement to use a minimum of electrical rated gloves.


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