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 Post subject: 70E 2105 addition
PostPosted: Thu Jul 10, 2014 10:26 am 
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Location: Westminster, MD
Per the attached changes document, there is to be an addition to the allowance of Energized Electrical Work - 130.2(A)(4) Normal Operation, stating that Normal operation of electric equipment shall be permitted when equipment is: properly installed and maintained, and doors and covers are on, and there's no evidence of impending failure.
This is consistent with Square D Tech Bulletin 0100DB0804R11/09 which lists four styles of Square D gear that can be operated with PPE 0 under normal circumstances.

My question to the group:
Is this 70E Normal operation note allowing the work to be done in PPE 0? The "work" being operation of a circuit breaker or a disconnect switch. That's what Square D's document does, for their gear, with similar restrictions.
I hope this is the case, because then it would be okay to operate a disconnect switch without PPE. But then the question becomes at what incident energy level is this prohibited??!!

Opinions are welcomed.


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 Post subject: Re: 70E 2105 addition
PostPosted: Fri Jul 11, 2014 7:31 am 
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To even further complicate things, Category 0 is being eliminated in 2015. There is also a simple Yes/No table regarding whether PPE is even required. I too am interested in other opinions.


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 Post subject: Re: 70E 2105 addition
PostPosted: Fri Jul 11, 2014 8:14 pm 
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Category 0 is not eliminated. It becomes the minimum required PPE for qualified personnel. The "no" cases for qualified personnel are the same as "category 0". For unqualified personnel, the definition of an arc flash hazard in 2012 edition indicates that the cases described as " no PPE required" in 2012 edition are notarc flash hazards but since it vaguely alludes to "interacting in such a way as to cause an arc" but does not define what this means, the 2015 edition defines it. So as the table states, no arc flash PPE is required. Nothing is changing except that the definition of interacting is further defined via the new tables. The old tables contain quite a bit of silliness. For instance, some tasks have category 0, 2, and 4 ratings on the same equipment, but the incident energy does not change. The only thing changing is the task, and that is where either it is low risk and does not require PPE, or it does and "reduced" PPE is the same result as no PPE. When you look at it this way it becomes obvious that if the incident energy calls for PPE 1, it does not matter if the PPE is 0 or "-1" (meltable clothing). The result is the same..not adequate protection if an arc flash occurs but the issue is not incident energy any more but likelihood in the first place. A meteor can hit anyone at any time and kill them dead, but the likelihood is so low that we don't use meteor shields at work, at least on the Earth's surface.

Following this argument then, there is no upper limit on incident energy because we are no longer requiring PPE.

The qualified personnel default "category 0" requirement captures cases such as most equipment under 250 volts where arcs certainly occur but where typically the incident energy is well under 1.2 cal. In these cases the minimal hazard is made worse if meltable clothing sticks to the skin or molten droplets hit it. For similar reasons OSHA is pretty much mandating 4 cal PPE for distribution gear. Several counter arguments were made recommending a nonmeltable PPE standard but OSHA would not budge unless all hazards are under 2 cal. It also avoids other issues. The mine where I work has gone to high visibility PPE required, but almost all of it melts. The arc rated shirts are very expensive, so we have to keep reminding guys to either wear vests that they can take off or strip the shirt off when putting on arc rated PPE.

In addition the new requirement states that if you do the engineering analysis, IEEE 1584 is not enough. It requires a risk analysis, just like any other safety analysis. So if you look at say IEEE 493 which gives arcing fault failure rates for disconnects, it becomes clear that no PPE should be required as the average incident rate as given by ESFI is about 1:100,000 arc flash incidents per year, and disconnect arcing rates are well below that threshold for average condition and maintenance. Condition is going to be a big deal, too.


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 Post subject: Re: 70E 2105 addition
PostPosted: Mon Jul 14, 2014 6:34 am 
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It is entirely possible that new arc-resistant designs can be operated without concern for PPE. Are the Square D units mentioned of that design or traditional design? I take issue with the committee allowing operation of a switch without PPE, when the equipment is not arc-resistant design. One of the major caveats is properly maintained. How is a worker who operates the switch to know all of those conditions exist? Many people are familiar with a video produced by Dow Chemical when grounding jumpers were mistakenly left in place and the worker throwing the switch was protected from injury because he was wearing the proper PPE. An arc is always initiated when switching occurs. Properly designed and maintained devices will contain and extinguish the arc. If there is something wrong within the protective device or if there is a condition external to the device that will initiate an arc there is a dangerous condition that could lead to injury. Traditional switchgear will not maintain its integrity under arcing conditions, depending on the level of energy generated. That comes back to the idea that it does make a difference what the incident energy may be at a specific location. The higher the energy the more severe the event when and if the doors blow open and energy escapes. It seems like we are abandoning the concept of protecting against worst case events in favor of operating convenience.


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 Post subject: Re: 70E 2105 addition
PostPosted: Mon Jul 14, 2014 7:49 am 
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rdj wrote:
... when grounding jumpers were mistakenly left in place and the worker throwing the switch was protected from injury because he was wearing the proper PPE...


The referenced document does not consider the operation of a switch as being normal if there has been 'work done on the equipment or conductors', such as installing grounds. They recommend that these situations be treated as 'equipment in unknown condition' and appropriate PPE be used.

Risk assessments are required by NFPA70E.


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 Post subject: Re: 70E 2105 addition
PostPosted: Mon Jul 14, 2014 8:16 pm 
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OSHA's new 1910.269 subpart V contains far better criteria to evaluate equipment condition than a vague definition in 70E and referencing 70B. I'm using their criteria. 70E doesn't even make sense when it refers to closed doors in what is effectively an arc flash table and not shock protection.

IEEE 493 shows that most breakers arcing faults are less likely than the likelihood of an arcing fault in general as published by ESFI (1:100,000/year) except drawout breakers which 493 data and at least one mention by ABB gives an order of magnitude higher failure rates due to the drawout mechanism failing during insertion or removal. Disconnect switch arcing fault rates are down around 10^-12...far below anyone's risk criteria.

I fail to see the relevance of arc resistant gear. The group most likely to be injured, by far, are maintenance and construction workers...guys working on the equipment with the doors open, precisely when arc resistant gear does nothing but cost extra money. All other arc flash mitigation methods, including proper maintenance, work equally well for all work, not just normal operation. I'd rqther spend the substantiqlly higher cost on mitigation techniques that the ct the personnel most likely to be injured. Well' been buying gear for years that protects the nonmaintenance worker. Lets try an approach that attacks the most likely injuries instead of nibbling around the edges.


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