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 Post subject: Hazard Risk Category 0
PostPosted: Tue Feb 17, 2009 11:41 am 
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Please define the incident energy level associated with Hazard Risk Category 0. For example, does it include 0-1.2 cal/cm squared or is it 0 - 2.0 cal/cm squared?


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PostPosted: Tue Feb 17, 2009 3:00 pm 
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I understand it to be HRC 0 = 0 to 1.9 cal/cm2, HRC 1 = 2.0 to 3.9 cal/cm2...

The 1.2 cal/cm2 is the energy required for a 2nd degree burn.


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PostPosted: Fri Mar 06, 2009 7:50 am 
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Since I replyed to this post, I have been to 2 different training seminars on NFPA 70E updates. Both lecturers stated that the code had been changed to HRC 0 = 0 to 1.2 cal/cm2, but they were unable to prove this using the 70E handbook. The only thing they could find is 130.3(A)(2) which concerns AFB's with voltage levels above 600 volts (I am working with 600 volts and below). EasyPower also changed their library to reflect this same change to HRC 0 - 0 to 1.2 cal/cm2 as opposed to their previous issue of 0 to 2 cal/cm. What is the correct HRC 0 level? Am I overlooking it in 70E?


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PostPosted: Fri Mar 06, 2009 8:03 am 
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My understanding is that if Table 130.7(C)(9) tells you a task is HRC 0, then you shall wear the content of line HRC 0 in Table 130.7(C)(11):
Quote:
Nonmelting, flammable material (i.e., untreated cotton, wool, rayon, or silk, or blends of these materials) with a fabric weight at least 4.5 oz/yd^2

The last column of that table is the minimum arc rating of your PPE. Since HRC 0 doesn't mandate you to wear arc rated clothing, then it's a N/A.

Now, if you have done an incident energy calculation (Annex D, or via software), then use PPE with the correct arc rating, for all parts of your body inside the AFB.


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PostPosted: Fri Mar 06, 2009 1:45 pm 
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130.7(C)(5) says "Employees shall wear FR clothing wherever there is possible exposure to an electric arc flash above the threshold incident-energy level for a second degree burn [5 J/cm2 (1.2 cal/cm2)]." Table 130.7(C)(10) defines HRC 1 as the lowest category requiring FR clothing, and defines HRC 1 as going up to an Arc Rating of 4 cal/cm², so I would interprete the two rules as making HRC 1 go from 1.2 to 4 cal/cm².


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PostPosted: Mon Mar 09, 2009 1:52 pm 
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That answers it. Thanks for your help.


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