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 Post subject: 2* Hoods or Socks
PostPosted: Sat Jan 12, 2008 8:24 pm 
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2* calls for a 'switching hood' which usually start at Level 3. The hoods tend to fog, reduce the oxygen content under the hood, and are hot. Oberon is selling a 2* faceshield and face sock. NFPA 70E doesn't address this option but I think OSHa also makes allowance for industry norms. The electrician prefer the sock and faceshield a lot better. What do you think to it being equivalent.


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PostPosted: Mon Jan 14, 2008 5:59 am 
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Category 2* Switching Sock

The Report on Proposals 2008 for NFPA 70E seems to be ready to make a change regarding the sock. The proposed change to the foot notes of Table 130.7(C)(9) Hazard Risk Tables includes the following wording:

(c) 2* designation — means that a arc flash suit hood, or alternatively a face shield used in combination with a balaclava (sock hood) is required for this task in addition to the other Hazard/Risk Category 2 requirements of Table 130.7(C)(10). These components shall have a minimum arc rating of 8 cal/cm2

On it's present track, it looks like the sock will be "officially" allowed with the next version of 70E.

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PostPosted: Mon Jan 14, 2008 10:32 am 
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We have been using the sock. This seems to be another confusing point between NFPA 70E and the IEEE 1584 Calculations. It seems 70E has category 2* for the hazard risk tables and IEEE just has Category 1, 2, 3 etc. without the " * " for the calculated incident energy. What exactly is the incident energy associated with a category 2*? I don't think it has ever been published. These two groups really need to coordinate their efforts.


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PostPosted: Mon Jun 02, 2008 8:26 pm 
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Big Sparks wrote:
We have been using the sock. This seems to be another confusing point between NFPA 70E and the IEEE 1584 Calculations. It seems 70E has category 2* for the hazard risk tables and IEEE just has Category 1, 2, 3 etc. without the " * " for the calculated incident energy. What exactly is the incident energy associated with a category 2*? I don't think it has ever been published. These two groups really need to coordinate their efforts.


It is not an incident energy per say but more of a risk factor and assumed head postition. Look at the 2* tasks compared to the HRC 2 tasks and think about what position your head would be in to do that task. Ex. Closing a breaker, most people have been trained to stand to the side and turn your head away (Dont do this with a facesheild on, it makes it an arc scoop), now thik of where your head is to take voltage measurements, your head is closer to see where you are putting the probes, plus it is a natural position.

Too bas none of this is published in the actual standard, it would make everyones life easier IMO.


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PostPosted: Mon Jun 02, 2008 8:27 pm 
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brainfiller wrote:
The Report on Proposals 2008 for NFPA 70E seems to be ready to make a change regarding the sock. The proposed change to the foot notes of Table 130.7(C)(9) Hazard Risk Tables includes the following wording:

(c) 2* designation — means that a arc flash suit hood, or alternatively a face shield used in combination with a balaclava (sock hood) is required for this task in addition to the other Hazard/Risk Category 2 requirements of Table 130.7(C)(10). These components shall have a minimum arc rating of 8 cal/cm2

On it's present track, it looks like the sock will be "officially" allowed with the next version of 70E.


Jim, the reason the sock wasnt allowed in the 2004 70E is that the ASTM standards to which the socks are tested to wasnt published yet, thus no sock could achived the ATPV rating.


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PostPosted: Fri Jun 06, 2008 8:01 am 
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Zog - Correct! I just didn't mention the reason.

Similar situation with Arc Resistant Switchgear. It was not included in the hazard risk tables in 2004 since it was still evolving at the time the last 70 was being revised. It is now included in the 2009 version. This whole thing just keeps evolving.

Thanks for the input!

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PostPosted: Mon Jun 09, 2008 3:04 pm 
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Ok... all this is great fodder for debates... cat 2* or not to 2*.... sock or not to sock? What's happening to IEEE 1584 arc flash is the same thing that's happened (and continues to happen ) NEC. Too many people getting lost in technical verbiage, formulas and unrealistic text book situations. As example the 2008 NEC code has over 3000 amendment proposals. 3000....? Com'on??? Most of these are submitted by people or groups that have little or no idea except crunching numbers. Some are more interested in making a name for themselves by touting being an "expert" in the field because they can do the NEC (or IEEE) calculations and can put on a snake oil side show. Check out the internet for "Arc Flash Consultants" Wow... everybody is an expert doing the IEEE math. IEEE 1584 is morphing into the same as NEC... too many debates on the "Their" validly of hypothetical numbers. Bottom line is it makes no difference if the numbers calculate out to 4.001 or 5.2 cal/cm2, it's still Cat 2. 49" or 45" boundary... who cares about +/- 4 inches when getting hit in the face with 30,000 F molten metal? Forgotten is the human factor in the equation. The human factor is a power^ 100. Get away with it once and nothing happens is: "Ummm I'm Ok, no big deal". Continue this a few times and exponentially the laws of probability of getting cooked skyrocket. I guess what I'm saying is all the formulas, theories and posturing mean nothing until the human factor is included into the, "It's not going to happen to me" equation.


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PostPosted: Thu Jan 29, 2009 2:36 pm 
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If we are calculating incident energy, Category 2 means between 4 and 8 Cal/cm2, at 18, 24 or 36" working distance, for all plausible tasks.

Does this imply that for arc flash compliance using calculations, Category 2 incident energy maps to Category 2* PPE?

Regards.


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PostPosted: Wed Feb 11, 2009 10:02 am 
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My experience has been that the face shield will fly off when closing a switch, my left arm makes contact with the bottom of the face shield mid throw. The hood does not move.


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PostPosted: Sat Feb 28, 2009 7:37 pm 
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Just a correction on one of the threads above, HRC 2 starts at a minimum 8 cal/cm2, I think a lot of people don't read the top of the table.

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Terry Becker, P.Eng.
http://www.esps.ca


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