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 Post subject: Arc Flash PPE Category Table.
PostPosted: Sun May 31, 2015 11:06 pm 
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As NFPA 70E, 2015, for the incident energy 1.3 to 12 cal/cm2. PPE Level 3 is mentioned, and for 12.1 to 40 cal/cm2 level 4 is mentioned. Is that right?
I did the arc flash assessment for our facility in last year as per NFPA 70E method having 0 to 4 category level, and now it has changed.
If it is correct then whether I have to use level 3 PPE for 1.3 or 1.4 cal/cm2 incident energy? or I have to use level 1 PPE as similar to earlier study.
And if it is not correct then what is the actual PPE Levels??


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 Post subject: Re: Arc Flash PPE Category Table.
PostPosted: Mon Jun 01, 2015 4:22 am 
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yograj.s wrote:
I did the arc flash assessment for our facility in last year ....


Did you make your assessment using the Task Tables, in NFPA70E, or did you perform calculations to determine the incident energy?


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 Post subject: Re: Arc Flash PPE Category Table.
PostPosted: Mon Jun 01, 2015 5:06 am 
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We have performed the calculations for incident energy first, then by using PPE table for incident energy, we have decided categories.
Like 1.2 to 4 - category-1
4 to 8 - category-2
8 to 25- category- 3
and 25 to 40 - category- 4..


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 Post subject: Re: Arc Flash PPE Category Table.
PostPosted: Mon Jun 01, 2015 8:32 am 
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The 2015 70E actually states that you can no longer use the PPE tables 130.7((C)(16) to select your level of PPE if you have performed an analysis and have the incident energy levels. If you do it as an internal table that is fine, but you cannot refer to the 70E's tables as a reference for the PPE. Instead you need to purchase PPE that protects you for the incident energy values that were found during your studies. Article 130.5(C) is very specific in stating that.
Our electrical safety team just had a 4 hour debate on how to change this internally. We are changing our labels to state that our techs need to wear Arc Rated clothing, head and neck Protection, Leather Boots, and Gloves and taking the reference to an HRC category off. During our training of the techs we are teaching them what PPE to put on based on the incident energy levels.
Hope this helps!


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 Post subject: Re: Arc Flash PPE Category Table.
PostPosted: Mon Jun 01, 2015 9:53 pm 
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As per my knowledge, formulas for the incident energy has not changed in NFPA'15. So Calculated incident energy will be same as per old and new revision of NFPA.
If one of my panel having 2 cal/cm2 IE then what is the PPE level as per '15 standard?
We are using PTW 32 V 7.0.4.0 which is modified as per NFPA'15 table.


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 Post subject: Re: Arc Flash PPE Category Table.
PostPosted: Tue Jun 02, 2015 3:47 am 
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[quote="yograj.s"If one of my panel having 2 cal/cm2 IE then what is the PPE level as per '15 standard? [/quote]

NFPA 70E-2015 contains Informative Annex H which provides guidance on selecting PPE based on incident energy levels.

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 Post subject: Re: Arc Flash PPE Category Table.
PostPosted: Tue Jun 02, 2015 5:19 am 
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yograj.s wrote:
As per my knowledge, formulas for the incident energy has not changed in NFPA'15. So Calculated incident energy will be same as per old and new revision of NFPA.
If one of my panel having 2 cal/cm2 IE then what is the PPE level as per '15 standard?
We are using PTW 32 V 7.0.4.0 which is modified as per NFPA'15 table.


As per 70E-2012 if you use the table method, you get an H/RC value based on a combination of task and equipment which then specifies PPE based on the third table. As per 70E-2015 you first determine whether or not PPE is required as per the task table. Then you determine the PPE level as per the equipment table, and finally the PPE requires as per the PPE table. The PPE table itself is identical in both versions but term has changed from H/RC to PPE to reflect the fact that the risk (Hazard/Risk Level) is now separately determined via the task table instead of mixing them.

If you are using the incident energy method then as per 70E-2012 you must determine the hazard via some kind of engineered approach. Several calculation methods are given in Annex D including the most popular, IEEE 1584. Then you must determine the risk based on the task. This is somewhat hidden inside the definition of an arc flash hazard in 70E-2012. In 70E-2015 it explicitly states that you must do a risk assessment which requires determination of both the magnitude of the hazard (incident energy analysis) AND the likelihood that an arc will occur (the risk analysis). Although there are lots of methodologies for doing the risk assessment, Annex F is not one of them because it is broken. If you don't believe me then turn to Annex F and attempt to do it. I have been suggesting the CCPS LOPA method because it is the most appropriate for arc flash hazards. Finally using the incident energy method you need to determine PPE. For this, turn to Annex H. Note that Annex H is ALMOST like the PPE table for H/RC or PPE levels. But it is different in that it recognizes that a face shield and balaclava for instance combined with roughly 12 oz. FR shirts and pants or coveralls can get all the way to a 12 ATPV whereas the table method rounds off at 8 ATPV before getting into the multilayer flash suit.

So remember...if you use the table method, you use tables. If you use calculations, you use an engineered approach. And you CANNOT mix them. At least according to the standard.

That is not to say that you can't locally ADOPT parts of the tabular method after doing an analysis of it as the basis for your determineation.


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 Post subject: Re: Arc Flash PPE Category Table.
PostPosted: Thu Jun 11, 2015 1:53 am 
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Where can I get NFPA 70E standard? Can anyone share the link?


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 Post subject: Re: Arc Flash PPE Category Table.
PostPosted: Thu Jun 11, 2015 2:25 pm 
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yograj.s wrote:
Where can I get NFPA 70E standard? Can anyone share the link?


www.nfpa.org. You can view standards for free. You can't print or search from that interface so it can be slow going. You can also order paper or PDF versions from their web site. Often with many NFPA standards there may be a "handbook" version as well. This one contains a lot more supplemental material that helps explain the text of the standard more clearly. The handbooks contain the complete Code but also contain nearly double the amount of documentation explaining the intent, giving examples, etc., where the Code is not clear.


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 Post subject: Re: Arc Flash PPE Category Table.
PostPosted: Thu Jun 18, 2015 8:21 am 
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all great questions and great answers. really helped clear this up for me. i asked a while back but was still a little fuzzy


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 Post subject: Re: Arc Flash PPE Category Table.
PostPosted: Mon Aug 17, 2015 12:15 pm 
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Again, I just don't know how to define the maximum clear time by using table method. The fault current can be low or much lower in a lot of situation.

How can you say that clear time is the maximum?


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 Post subject: Re: Arc Flash PPE Category Table.
PostPosted: Tue Aug 18, 2015 7:54 am 
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Noah wrote:
Again, I just don't know how to define the maximum clear time by using table method. The fault current can be low or much lower in a lot of situation.

How can you say that clear time is the maximum?


The maximum clear time is taken from the time current curve for the specific protective device that would be clearing the fault. This would be the upstream device for the equipment being worked on.

Knowing the manufacturers name, device model number and trip settings, you need get the specific TCC from the manufacturer. Then you take the fault current and see what the trip time is on the curve. Then you can determine if you meet both parameters for using the table.

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 Post subject: Re: Arc Flash PPE Category Table.
PostPosted: Tue Aug 18, 2015 8:25 am 
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The fault current you obtained from analysis is the value based on very low impedance in the system, therefore it should be the highest one and cause the minimum clearing time when that occurs. How do you know that clearing time is the maximum value since the lower current will be longer clearing time for the device.

By the way, anyone can share how do you provide arc flash risk assessment in addition to the arc flash analysis which is for selection of the PPE mainly. Do you include this assessment in your new study project?


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 Post subject: Re: Arc Flash PPE Category Table.
PostPosted: Tue Aug 18, 2015 4:37 pm 
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Noah wrote:
The fault current you obtained from analysis is the value based on very low impedance in the system, therefore it should be the highest one and cause the minimum clearing time when that occurs. How do you know that clearing time is the maximum value since the lower current will be longer clearing time for the device.


Short answer: You don't but the tables are at best a guide that tries to fit all. The committee tried to provide something that could help as many people won't do a study, so I think they did not want to publish something that says to protect employees and not give some sort of tool to guide people to some PPE.

I think it was DuPont that did a study of arc flash incidents in their plants and determined injuries due to burns from an incident:

1. No AR PPE - 100%
2. PPE from tables in NFPA 70E - 50%
3. PPE from actual study - 0%

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 Post subject: Re: Arc Flash PPE Category Table.
PostPosted: Wed Aug 19, 2015 6:17 pm 
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Close. The majority of the data came from Dupont. Nothing = 10%. Tables = 50%. IEEE 1584 = 100%. So far I am not aware of any case where PPE selected using the IEEE 1584 method and NFPA 1959 failed to protect. Numerically, IEEE 1584 itself predicts a 90-95% success rate. There are three reasons I believe it may be YEARS before IEEE 1584 "fails":
1. Although ASTM 1959 fits the pass/fail data to a sigmoidal curve to predict the 50% failure point (as reported by ATPV), in reality the raw data tells a different story. Most materials either entirely pass or entirely fail at a point roughly 0.5 to 1.0 cal/cm^2 away from the ATPV regardless of what the sigmoidal curve predicts.
2. Very few incident energy results from IEEE 1584 will exactly match the ATPV on the PPE. Thus in the vast majority of cases, workers are overprotected by a large margin (not within 0.5 to 1 cal/cm^2 of the ATPV). So these cases are essentially 100% protection.
3. The vast majority of arc flash incidents are never reported if nothing bad happenss. We've seen incident rates drop to almost half over the past 10-15 years. The three contributors to this will be the rise in EEWP usage reducing exposures, increased use of arc rated PPE, and perhaps better maintenance practices? Out of the three it would not be inconceivable that only use of arc rated PPE has caused nearly the entire change. Thus with rates cut in half it would seem that at most, workers are using arc rated PPE 50% of the time. At worst it makes no difference but again, no reported cases of failure of the PPE that I am aware of.


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 Post subject: Re: Arc Flash PPE Category Table.
PostPosted: Fri Aug 21, 2015 5:34 am 
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What will be the major difference in Arc Flash Labels comparing NFPA 70E Rev 12 & 15?

we have used IE Calculations as per NFPA 12. labels having 3 major things as AF Category, IE, and PPE Description.

As per latest revision, we have only cancelled AF category from the labels and changed the PPE Description. Is it Ok? or should we do any more changes?


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 Post subject: Re: Arc Flash PPE Category Table.
PostPosted: Wed Aug 26, 2015 6:37 pm 
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Making it clear that "PPE category" can't be used with incident energy is really the only "change" to a label. This has been required for a while but again, not clear. The reasoning behind this is now rather moot though because as of the 2015 edition, the mixing of hazard and risk is gone.

The other major glaring error that I've seen with labels in general, and this goes for even the requirements in NFPA 70 (NEC), is requiring following ANSI Z535 for labelling. There are three places where this gets seriously botched. The first one is, how many labels have you seen with the diamond shape around the word "DANGER" for instance or anything else other than a simple rectangle/block of color? These labels are following the OLD standard which is now deprecated and yet even with new equipment, that's about all you will see. You have to go out of your way to find actual NFPA Z535 compliant labels in the Brady catalog.

Second, and more glaring, is misuse of the key words "DANGER" and "WARNING" and this is no more clear than when it comes to the silly way that arc flash labels are done. The signal word DANGER is only to be used when there is an immediate danger to life or a serious life altering injury. In contrast, the signal word "WARNING" applies when it's still a death/life altering injury case but where something else has to happen or the worker has to do something to get themselves into trouble. An example of the "DANGER" label would be access to a wood chipper or the inside of a large industrial fan. In contrast simply removing a cover to electrical equipment, or operating it, or doing pretty much any other task where a label would be appropriate, to where there is a risk but not an immediate danger to life, is simply a WARNING, not DANGER. Yet the DANGER label is required in several places in NEC inappropriately and even more ridiculous, it is used quite frequently on arc flash labels over 40 cal/cm^2 as if it is a given that even getting close to equipment over 40 cal/cm^2 is instant death. Wrong, wrong, wrong.

The third and final problem is that the labels are supposed to describe the hazard and what steps to take to avoid it. A classic example is "DANGER -- HIGH VOLTAGE -- KEEP OUT". What's missing here? It doesn't indicate what the specific hazard actually is. High voltage describes the system but no the hazard. Arc flash labels do the opposite...describe various details about the hazard but fail to describe what to do to avoid it. Neither one is ANSI Z535 compliant, and neither are probably 99% of the other labels out there.

A fourth, frequently REQUIRED violation as of the 2014 edition of NEC, is that no more than 3 specific labels/hazards are allowed per task. As of the 2014 edition on main breakers on switchgear with any grounding other than solidly grounded systems and/or with main-tie-main arrangements, a half dozen or more labels are now required by Code. So it's not that it just seems like NEC-2014 is ridiculous with the new label requirements...it actually is ridiculous and impossible to follow the regulation which simultaneously requires adherence to the current edition of ANSI Z535 AND having labels for just about anything and everything.


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 Post subject: Re: Arc Flash PPE Category Table.
PostPosted: Thu Aug 27, 2015 4:17 am 
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The only thing I would add is that Danger is on some labels that contain both Arc Flash AND Shock hazard. It takes very little current to cause death or other serious injury.

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 Post subject: Re: Arc Flash PPE Category Table.
PostPosted: Fri Aug 28, 2015 11:51 am 
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If you follow table 4B and 4C to select the proper PPE from table 5, the maximum level is Category 4 up to 40 cal/cm2. However, if you follow incident energy analysis method to select the PPE from table H2 and H3, it seems there is no upper limits and you can get PPE for incident energy as high as 1000cal/cm2 if it exists.

Question 1. What PPE category will be for the task if it doesn't fall into table 4B and 4C?
Question 2. How can you define the category if the arc flash PPE is required by table 4A but not covered by table 4B and 4C?
Question 3. Why two methods give different range for the PPE level in terms of incident energy?


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 Post subject: Re: Arc Flash PPE Category Table.
PostPosted: Fri Aug 28, 2015 8:40 pm 
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Noah wrote:
If you follow table 4B and 4C to select the proper PPE from table 5, the maximum level is Category 4 up to 40 cal/cm2. However, if you follow incident energy analysis method to select the PPE from table H2 and H3, it seems there is no upper limits and you can get PPE for incident energy as high as 1000cal/cm2 if it exists.

Question 1. What PPE category will be for the task if it doesn't fall into table 4B and 4C?
Question 2. How can you define the category if the arc flash PPE is required by table 4A but not covered by table 4B and 4C?
Question 3. Why two methods give different range for the PPE level in terms of incident energy?


The "PPE level" is only defined as 1, 2, 3, or 4. There is no "category" for anything else. If you use tables H2 and H3, then you don't use a "PPE level" (category). But I have to asterisk this with something fairly obvious. A site can of course choose to create it's own "system" and that can be anything at all. As an example if you specify a face shield and balaclava for any work that requires arc rated shirts and pants and the minimum cal/cm^2 rating for the PPE on hand is 10 cal/cm^2 which it is for Indura Ultrasoft shirts then you can make "A" category these items. Then since for all practical terms there is little difference between a 25 cal/cm^2 and 40 cal/cm^2 multilayer flash suit, "B" can be the 40 cal/cm^2 flash suit. And if you use one of the over the top 100 cal/cm^2 flash suits, then this can be a "C" category. The letters A, B, and C have no meaning outside of site specific usage just as the numbers 1, 2, 3, and 4 have no meaning outside of the tables. If you use incident energy, the numbers in tables 4B and 4C have no meaning but then again, the equipment list in table 4B is pretty limited and there are lots of types of equipment that are not on the table, even if it's just an opening time limitation.

Second question...you don't. You must use the incident energy method and then you are using tables H2 and H3 and putting incident energy on the label and NOT a PPE level, unless again you defined a local value. This is pretty clear in the text...if it doesn't fit the table, you can't use the table.

As to why two different methods give two different results, that should be intuitively obvious but here goes. First, the table method in 70E relies for the most part on calculations done using IEEE 1584 using the extreme ccases (maximum arcing current, voltage, and opening time conditions given). So in effect it "rounds up". The Lee method relies on a theoretical "maximum power transfer" assumption that does not necessarily translate in the real world. For instance not all of the energy is converted into radiant heat. Some of the energy is converted into heating of the air inside the enclosure which gets converted into pressure in the form of an arc blast. Second the actual arcing current is not at the maximum power transfer point but is somewhat depending on voltage. Finallly the Neal equation was an early attempt to create an "IEEE 1584" like equation and represents one step in the development. IEEE 1584 eschews any theoretical basis and is purely empirical. ArcPro uses a completely different theoretical approach that is mostly appropriate for open air arcs so it necessarily has different results from IEEE 1584. ArcPro is also the basis of the tables in NESC rather than IEEE 1584 so once again, we see variability here. And the low voltage tables in NESC are based on actual measured values on real world equipment so they don't necessarily correspond to the "arc in a standardized box" so they do not necessarily represent the same conditions that the IEEE 1584 equation is based on but again it's a table so there is a certain amount of "rounding up" that is done.

The question is of course how to choose so here goes. First, use Lee only as a last resort and these days, that's pretty limited. Use actual testing whenever possible/practical as this is the best approach ultimately, so NESC values when they apply are better than any other method. Use test values for <250 V as the theoretical models fall down here and IEEE 1584 results are also suspiciously off. Use IEEE 1584 for 250 V to 15 kV. Use ArcPro above 15 kV. Hopefully the Wilkins model will eventually replace IEEE 1584 although in the end it is very close to the same result as IEEE 1584 except that since it is a time-based model, it can more accurately represent current limiting conditions.


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