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 Post subject: Use of Table 130.7 (C)(A)(a)
PostPosted: Fri May 01, 2015 9:39 am 
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Can you use Table 130.7 (C)(A)(a) if you use the IE method? 130.7 (15) infers you cannot. However, I don't understand the logic behind saying it's ok to not use PPE under one method (table) but required for another (IE), even though the actual operation is the same (ie opening a CB)


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 Post subject: Re: Use of Table 130.7 (C)(A)(a)
PostPosted: Fri May 01, 2015 3:11 pm 
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Litespeed wrote:
Can you use Table 130.7 (C)(A)(a) if you use the IE method? 130.7 (15) infers you cannot. However, I don't understand the logic behind saying it's ok to not use PPE under one method (table) but required for another (IE), even though the actual operation is the same (ie opening a CB)


There are two methods. Method 1 is the table method which uses the risk table you are referring to, the equipment table, and the PPE table.

Method 2, the "incident energy method" requires a risk assessment, a hazard assessment, and a PPE assessment. Many users were mistakenly only doing the hazard assessment because that's what the standard said to use. They missed the other two items entirely. The hazard assessment was always there not only in OSHA and similar regulations but it is also obscurely bured inside the definition of an arc flash hazard. The correct PPE analysis should involve your vendor(s) but in reality the guidance is given in Annex H, just as the hazard assessment is in Annex D, and an INCOMPLETE risk assessmen methodt is given in Annex F.

In reality comparing Annex H to the table shows they are the same thing except that Annex H is in terms of incident energy and the table is in PPE levels (previously H/RC levels). There is a little more flexibility in Annex H though. Annex D gives a partial list of various incident energy analysis methods including the most popular one, IEEE 1584. Finally the risk assessment method given in Annex F is not only incomplete but appears to be based on ANSI B11.TR3 which is for moving machinery and not really a good fit for arc flash hazards at all. And its incomplete. To see what I mean, try using it. You'll get a list of 4 values and you'll have all kinds of questions about the vague definitions (no help given) and if you look at the example, you can add them up to get a score, but then it just ends. There is no guidance on using it.

That all being said, the risk assessment MUST be done if you do a hazard assessment using say IEEE 1584. There is simply no guidance in 70E. The extent of your risk assessment can be that you simply adopt the risk table and use that. There is nothing wrong with it at all. OSHA just requires you to document what you do, and this is a fine way to go about it. I have two issues with the table as it stands though:
1. It gets hung up on the idea that medium voltage gear is somehow different and less safe than low voltage equipment. I'll grant that it is different but due to design and in actual practice, it is impossible to claim that it is less safe. Quite the contrary in fact.
2. It talks about whether equipment is in eminent danger of failure but gives no guidance as to how to go about doing this. In this regard even though it's for utilities, OSHA 1910.269 annex is much better. In fact you could just as easily adopt OSHA 1910.269's table for non-utility scenarios and there's nothing wrong with it.

I highly suggest that to meet OSHA's requirements for risk assessments and PPE (which is where the risk asessment requirement comes from), consider either adopting one of the two tables just mentioned outright or using one of the available risk assessment methodologies so that you are using a documented approach. In that regard, the CCPS LOPA method is the best fit for electrical hazards in general because it is designed to handle low likelihood "freak" failures that result in extreme catastrophic results (serious injuries or death), and it's generalized enough to use it for anything including electrical hazards. All other risk assessment codes that I'm aware of fail to meet one or more of these criteria.


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 Post subject: Re: Use of Table 130.7 (C)(A)(a)
PostPosted: Mon May 04, 2015 9:10 am 
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Paul,

Thanks for your input. I agree with you on Annex F - total unusable.


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