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 Post subject: 2* at 7.9 cal/cm2?
PostPosted: Wed Mar 25, 2009 10:11 am 
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In the 09 Handbook, page 143, 2nd paragraph of the blue interpretation.

If an incident energy analysis is done rather that using Table 130.7(C)(9) and the result is 7.9 cal/cm2, the same PPE as shown in Exhibit 130.9 needs to be worn because the back of the head needs protection.

At 8.0 cal/cm2 we change to HRC 3.

So if using the analysis method, where exactly is 2* required - only at 7.9cals. Even if the face shield and balaclava are rated higher, to 9.5 ot 10.5 etc, I don't see in table c10 where you can use it above 8 cal.

Anyone explain. If I remember, 1584 didn't have a 2* level. So if you do your analysis under 1584 does 2* still come into play. I release the interpretation is not code, but asking opinion.


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PostPosted: Wed Mar 25, 2009 10:39 am 
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haze10 wrote:
Anyone explain. If I remember, 1584 didn't have a 2* level. So if you do your analysis under 1584 does 2* still come into play. I release the interpretation is not code, but asking opinion.


IEEE 1584 2002 doesn't have any HRC categories at all. You only get a distance (AFB) and an incident energy (cal/cm^2) at a given distance.

Table 130.7(C)(10) can only be used with table 130.7(C)(9).

You need to cover with FR rated clothing or equipment everything inside the AFB. If your IE is less than the rating of your balaclava, then you can use it.

If the AFB lies between your forehead and your ears, then you technically don't need to cover the back of your head with FR rated PPE.


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PostPosted: Wed Mar 25, 2009 7:42 pm 
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Vince,
Are you sure? The clothing Table doesn't include the option for balaclava and faceshield under the HRC category. It says 'hood' for HRC3.

What do you think that task is referencing.


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PostPosted: Thu Mar 26, 2009 5:45 am 
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haze10 wrote:
Vince,
Are you sure? The clothing Table doesn't include the option for balaclava and faceshield under the HRC category. It says 'hood' for HRC3.

What do you think that task is referencing.


Vince is correct, once you do the analysis you protect the worker with whatever PPE is rated for that (Or higher) Ei, you no longer use the tables or the HRC's.


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PostPosted: Thu Mar 26, 2009 5:45 am 
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haze10 wrote:
Vince,
Are you sure? The clothing Table doesn't include the option for balaclava and faceshield under the HRC category. It says 'hood' for HRC3.


You're missing a HRC number at the end of your second sentence, so I'll guess you meant 2*. If you meant something else, then please reply.

Table 130.7(C)(10) includes the option for balaclava and faceshield in Note 10, and the only reference to Note 10 is in HRC 2*. So if you're doing a task per Table 130.7(C)(9) rated 2*, then you have the choice of using a balaclava and faceshield instead of a hood.

Now, going back to your original question, Table 130.7(C)(10) is to be used only with Table 130.7(C)(9), not with a calculation from IEEE 1584-2002 (or another calculation method). If you use IEEE 1584-2002, forget about the HRC, so forget about using Tables 130.7(C)(10) and 130.7(C)(11). What article 130.

My interpretation of the second blue paragraph on page 143 of the 2009 Handbook is that if a calculation gives you 7.9 cal/cm^2 at a given working distance, then it's a given that the back of your head will lie inside the AFB (understand: will see more than 1.2 cal/cm^2) so it will need FR protection. Exhibit 130.9 shows you 2 ways of achieving that: balaclava and faceshield (130.9(a)), of hood (130.9(b)).


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PostPosted: Thu Mar 26, 2009 2:34 pm 
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Don't mean to be argumentative but...

If the 1584 analysis indicated 3.9 cal/cm2 at the working distance, would not you expect greater than 1.2 cal/cm2 at the back of your neck? Are they saying that with the average neck being 7 inches thick (mine is more) when you have 7.9 cals on the front you have 1.2 on the back?

I don't see where it says that the HRC categories in Table C10 are only for the Table C9. It says once the risk of C9 is determined to use the C10 Table.

I know Jim mentioned in another post about the possibility of wearing any rated garment as long as it met the IE, but I didn't think we were there yet. So an 1584 task at 9.0 cals requires the hood, even if you have a 10 cal rated balaclava and faceshield.

What am I still missing here.


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PostPosted: Fri Mar 27, 2009 6:37 am 
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haze10 wrote:
Don't mean to be argumentative but...

If the 1584 analysis indicated 3.9 cal/cm2 at the working distance, would not you expect greater than 1.2 cal/cm2 at the back of your neck? Are they saying that with the average neck being 7 inches thick (mine is more) when you have 7.9 cals on the front you have 1.2 on the back?


Exactly the same as you: if your face is inside the AFB (which is the distance where the IE is 1.2 cal/cm^2), then most probably the back of your neck is inside too, so it needs covering.

haze10 wrote:
I don't see where it says that the HRC categories in Table C10 are only for the Table C9. It says once the risk of C9 is determined to use the C10 Table.


NFPA 70E-2009 130.3(B):
Quote:
Protective Clothing and Other Personal Protective Equipment (PPE) for Application with an Arc Flash Hazard Analysis
Where it has been determined that work will be performed within the Arc Flash Protection Boundary identified by 130.3(A), one of the following methods shall be used for selection of protective clothing and other personal protective equipment:
(1) Incident Energy Analysis. [...] Arc-Rated FR clothing and other personal protective equipment (PPE) shall be used by the employee based on the incident energy exposure associated with the specific task. [...]
(2) Hazard/Risk Categories. The requirements of 130.7(C)(9), 130.7(C)(10), and 130.7(C)(11) shall be permitted to be used for the selection and use of personal and other protective equipment.


You select either (1) or (2). If (1), the FR rating of your equipment must be greater than the IE. If (2), then you are permitted to use 130.3(C)(9 to 11).
Note that permission is not in (1).

NFPA 70E-2009 130.3(C)(10):
Quote:
Protective Clothing and Personal Protective Equipment Matrix
Once the Hazard/Risk Category has been identified from Table 130.7(C)(9) (including associated notes) and the requirements of 130.7(C)(9), Table 130.3(C)(10) shall be used to determine the required PPE for the task. [...]


You can't use Table 130.3(C)(10) by itself, it must be used with 130.3(C)(9) and Table 130.3(C)(9).

haze10 wrote:
I know Jim mentioned in another post about the possibility of wearing any rated garment as long as it met the IE, but I didn't think we were there yet. So an 1584 task at 9.0 cals requires the hood, even if you have a 10 cal rated balaclava and faceshield.

What am I still missing here.


I understand the method (1) (calculation of IE) as exactly that: rating > IE.


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PostPosted: Fri Mar 27, 2009 7:57 am 
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Vincent,
Are you then saying that the balaclava is required for all IE > than 1.2 cal/cm2. If so, why is the handbook referencing 7.9 cal/cm2.

If the 'front' is 1.2 cals exactly, then anything further away from the 'front' like the 'back' of your neck is less than 1.2 cals and doesn't need protection.

So is the handbook saying that when the working distance (the 'front' of the chest and face) is 7.9 cal/cm2 only at that level and higher you need the balaclava? You seem to be saying at anytime the back of the neck is greater than 1.2 cal/cm2. But all calcs are done to the 'front'. So is it that at 7.9 in the 'front' you have 1.2 (based upon average neck thickness) in the 'back' (and greater of course).

Sorry, but I just find this very confusing.


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PostPosted: Tue Mar 31, 2009 10:39 am 
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HRC and labels

I have a question relating to this about labeling.

The way I read 2009 130.3(C) is that HRC should not be on the labels after a study has been completed. Just the incident energy or level of PPE (which I assume would be a description of the PPE related to the calories).

Can someone break this down for me? Thanks.


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PostPosted: Fri Apr 03, 2009 10:37 am 
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Here's the thing. Everyone is somewhat right. (I'm not saying I have all the answers, just trying to play mediator). Vince is right in the fact is that when it comes to HRC method or IE analysis method you can choose which to use. To say that table 130.7(C)(10) only applies to Table 130.7(C)(9) is not the whole truth. Yes it does apply to that table, but it also applies to a corresponding Cal/cm2. Some people use this as a simplifed way to understand what PPE to where at a piece of equipment. If you are doing a detailed AFHA you can reference the HRC tables to correspond to your calculated IE, there is nothing wrong with that.

Now on the subject of the 2* this is where the HRC tables gets confusing. First of all 2* can either use a balaclava or flash suit hood. If you are using the table method for you AFHA Table 130.7(C)(9), than you can rightfully separate 2's and 2*'s. However if you are doing a detailed AFHA, and using the HRC approach for PPE selection, than you only have the option of 2* to choose from for anything >4cal, <8cal. Rember the table method is not based on IE it is based upon TASKS this is why no clear IE is assigned to 2*.

Bottom line pick a method for analysis
  • Detailed method calculating IE
  • Table method using only HRC based upon TASKS
Pick how you are going to choose PPE
  • IE analysis - PPE must at a minimum meet calculated IE
  • HRC - Based upon Table method of AFHA involving TASKS
  • HRC - involving calculated IE that corresponds to an HRC #

Finally be consistent with your approach you have chosen!!

Hope this helps!


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PostPosted: Fri Apr 03, 2009 10:38 am 
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Don't_wanna_burn wrote:
I have a question relating to this about labeling.

The way I read 2009 130.3(C) is that HRC should not be on the labels after a study has been completed. Just the incident energy or level of PPE (which I assume would be a description of the PPE related to the calories).

Can someone break this down for me? Thanks.


This means you either list the calculated IE or give an HRC the the IE falls into. Either one of these will allow for proper PPE selection.


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PostPosted: Fri Apr 03, 2009 6:46 pm 
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That was a good common sense interpretation. I could agree with you regarding the Balaclava from 4 to 8 cals, although I don't see this in the code.
I also still can't understand this sentence, ..."If an incident energy analysis is done rather that using Table 130.7(C)(9) and the result is 7.9 cal/cm2, the same PPE as shown in Exhibit 130.9 needs to be worn because the back of the head needs protection."

It doesn't say 'below, or above' it says equal to and equal to only 7.9. Not 7.8 and not 4.0.


Do you think it is say 7.9 to the limit of the balaclava (ie 10.1)?

Not trying to be stubborn, but I want to understand this. Maybe its a typo, like they did with the 240V equal and above rule.


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PostPosted: Fri Apr 03, 2009 8:22 pm 
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Regarding the HRC categories 2 and 2*,the tables regarding tasking such as voltage testing placing in HRC 2* because they feel the worker may be working in different positions more prone to exposure of places on the head not protected by the faceshield .An example being turned to read a meter.I have read that being at an angle to a flash or blast with a faceshield funnels the blast in on the face.Still some injury with a balacalava,but not with the hood.


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PostPosted: Sat Apr 04, 2009 5:26 pm 
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I can understand the rational for the balaclava, thats not a problem. But I can't understand why the 7.9cal reference, and only equal to 7.9. Maybe I'm not alone as no one has really addressed this reference with a response specific and that makes sense.


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PostPosted: Sat Apr 04, 2009 6:51 pm 
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You certainly aren't alone on the 7.9 cal reference Haze.My understanding for HRC 2* would be 4-8 cal/cm2.I will be happier when the industry moves from HRCs to IE.


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PostPosted: Mon Apr 06, 2009 6:18 am 
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haze10 wrote:
I also still can't understand this sentence, ..."If an incident energy analysis is done rather that using Table 130.7(C)(9) and the result is 7.9 cal/cm2, the same PPE as shown in Exhibit 130.9 needs to be worn because the back of the head needs protection."

It doesn't say 'below, or above' it says equal to and equal to only 7.9. Not 7.8 and not 4.0.


Do you think it is say 7.9 to the limit of the balaclava (ie 10.1)?


I see what you are talking about now. I don't think this is giving any type of restrications on the balaclava, it is good up to manufacturers testing and labeling. But to say it is only needed once you hit the 7.9 mark is a bit strange. Maybe that is the way to delineate between 2 and 2* when using the IE method. Up to 7.9cal just a face shield is acceptable any higher than you must add the addition of a balaclava or flash suit hood. I think that is what it is trying to get at. I still say if you are using the 2* for everything between 4 and 8 cal. you will be fine.

The book is intermingling the IE method with the HRC method this is why it only mentions 7.9. It is referring to the HRC method os 2* which is only good up to 8cals. if it starts at 7.9 this would be the only IE in the category. After that it moves into a level 3 using the HRC method. Using the IE method strictly you would wear a face shield only up to 7.8cals at 7.9 and higher (depending on the manufacturers cal rating) you would use the balaclave and face shield combo until you exceed the manufacturers rating then you would switch to a flash suit hood.

Rambled a little there sorry.


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PostPosted: Mon Apr 06, 2009 1:31 pm 
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haze10 wrote:
I also still can't understand this sentence, ..."If an incident energy analysis is done rather that using Table 130.7(C)(9) and the result is 7.9 cal/cm2, the same PPE as shown in Exhibit 130.9 needs to be worn because the back of the head needs protection."

It doesn't say 'below, or above' it says equal to and equal to only 7.9. Not 7.8 and not 4.0.


Do you think it is say 7.9 to the limit of the balaclava (ie 10.1)?



It is not a limit, just an example. 7.9 was chosen for this example since it puts our guy within the HRC 2/2* category (above 4 and less than or equal to 8) and footnote 10 of 130.7(C)(10) is satisfied. The author could have also chosen 7.8 or 4.457.

The 2 versus 2* HRC is not based on IE, but on the task per table 130.7(C)(9). If not using the table, there is no 2* category. Author seems to be making the point that the back of the head needs protection for any IE ove 1.2 per 130.7(C)(5). Not sure how this melds with Table 130.7(C)(10) HRC 1.

The limit of the balaclava is 8 if using the HRCs, or actual APTV is not.


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PostPosted: Wed Apr 08, 2009 9:19 am 
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Just when I thought 70E is as confusing as it could get, we have another issue to put on the pile. Everyone’s comments and input are great on this one. I think the subject paragraph in the “Blue Book” did mix the two methods of Tables C(9) / C(10) and the Arc Flash Calculation Study (IE Method).

Table Method:
130.7(C)(10) states: …Once the Hazard/Risk Category has been identified from Table 130.7(C)(9)… … Table 130.7(C)(10) shall be used to determine the required PPE for the task. I don’t think this was intended to require it’s use with the IE method but everyone uses it.

Category 2* references a balaclava / sock with arc rating of 8 cal/cm^ minimum. I believe 2* was never intended to be used with the IE method. It was an extra level of protection determined by the group that developed the HRC tables for a few specific tasks (like voltage testing).

The table method was based on many peoples “engineering judgment” not calculations. Since we have IEEE 1584 which is site / location specific, calculations are the preferred method if they can be done without breaking the bank$$ (which it could easily do and is creating a burden with many companies)

In Lieu of the calculation method, the tables can still be used but I think they can be confusing (as we see in this discussion thread).

IE Method:
The calculation method determines the incident energy – period. PPE > I.E.

The 5 categories (0 through 4) were based on PPE for HRCs from the tables but the HRC’s also correspond to I.E. levels. This is where the confusion lies. There is no 2* with the IE method.

Head, Face, Neck, Chin Protection NFPA 70E’s requirement
130.7(C)(3) Head, Face Neck and Chin Protection. Employees shall wear nonconductive protective equipment for the face, neck, and chin whenever there is a danger of injury from exposure to electric arcs or flashes or from flying objects resulting from electrical explosions.

The head face and neck need to be protected but no guidance is given on how to do this. No reference about the back of the head. Some PPE manufacturers have a hood with an air intake on the rear and blower that blows the air into the hood. I talked with one rep a while ago and questioned him about what would happen if the arc flash goes into the intake, the response was they did not see that as a problem since it was behind the person. Sounded more like a marketing answer – what if you are working sideways?

My personal opinion (which sometimes gets me into trouble) is that this is just another inconsistency / hole in 70E. If you play by the rules that any exposure above 1.2 cal/cm^2 needs protection, then a sock would be required for category 1 (oops there I go confusing HRC and IE) I mean required for incident energy above 1.2 cal/cm^2 which would include HRC 1 and 2 but 70E does not specifically say this so we are all left pondering (again) what the correct answer / interpretation is.

So… where does this leave it, I’m not sure there is a black and white answer on this one.

We’ll let the discussion continue!

_________________
Jim Phillips, P.E.
Brainfiller.com


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PostPosted: Thu Apr 09, 2009 11:28 am 
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I'm late to the gathering but it's a great discussion!

As someone who only owns the code book for 70E and not the handbook, the 7.9 cal/cm2 number was all new to me. I have been wondering how the 2* fit into the IE calculations as I am beginning to get my study part way done.

This raises the question - since it's in the blue text (what we really meant to say..) of the handbook only, how does this relate to "enforcible" rules? So far I've been using 8 cal/cm2 as the top of my HC2 and after that switching to HC4 (using the 0,2,4 plan). Do I now need to switch to 7.9 cal/cm2 for HC4? That's almost splitting hairs. In looking at this, I assumed that the faceshield, when used properly, was meant to protect the head area and back of the neck by deflecting the blast. I like Eldon's suggestion that the tables have to do with working position for specific tasks, but who knows....

I look forward to more comments on this.

TxEngr


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PostPosted: Thu Apr 09, 2009 5:36 pm 
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My information on HRC 2* comes from our Canadian version of NFPA70E 2009
edition which is our CSA Z462. The format of our standard is a bit different but the information was drafted directly from NFPA70E.There is a section in this forum,(not real active) for our standard.I am actually more familiar with NFPA70E as it has been around much longer.What is certain universally is the problems we all are wrestling with regarding interpretation as we endeavor to incorporate arc flash safety in our workplaces.I agree with Steven that the 7.9 cal/cm2 was an arbitrary value selected just under 8 cal/cm2 so as not to blur HRC2 with HRC3. HRC2* is definitely task specific when the normal calculated stance of working at normal arms length and posture does not apply.(eg: voltage testing)


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