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 Post subject: PPE based on incident energy method
PostPosted: Tue Apr 26, 2016 6:57 am 
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I'm working through an incident energy calculation for my facility and therefore will not be utilizing the Arc Flash PPE Categories Method. I'm a bit confused about how the PPE levels are defined and about where to look to determine the exact assemble of clothing and protective equipment required if I go the incident calculations path. I can't use the PPE Categories Method or tables but are the categories the same regardless of whether the tables or actual calculations are performed? Specifically, I read Table 130.7(C)(16) to define PPE levels as follows:

0-4 Cals = PPE#1
4-8 Cals = PPE#2
8-25 Cals = PPE#3
25-40 Cals = PPE#4

As for what to wear, I want to use Table 130.7(C)(16) for determining the precise set of clothing & equipment required (since it nicely layouts the parts & pieces required) but this table is based on PPE Categories and NFPA 70E makes it clear that Table 130.7(C)(16) is NOT to be used if doing an incident energy calculation method. If I don't use that table how do I know what assemble is correct based on the calculation results?

Thanks in advance,
Brian


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 Post subject: Re: PPE based on incident energy method
PostPosted: Tue Apr 26, 2016 9:40 am 
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DMB5mil wrote:
I'm working through an incident energy calculation for my facility and therefore will not be utilizing the Arc Flash PPE Categories Method. I'm a bit confused about how the PPE levels are defined and about where to look to determine the exact assemble of clothing and protective equipment required if I go the incident calculations path. I can't use the PPE Categories Method or tables but are the categories the same regardless of whether the tables or actual calculations are performed? Specifically, I read Table 130.7(C)(16) to define PPE levels as follows:

0-4 Cals = PPE#1
4-8 Cals = PPE#2
8-25 Cals = PPE#3
25-40 Cals = PPE#4

As for what to wear, I want to use Table 130.7(C)(16) for determining the precise set of clothing & equipment required (since it nicely layouts the parts & pieces required) but this table is based on PPE Categories and NFPA 70E makes it clear that Table 130.7(C)(16) is NOT to be used if doing an incident energy calculation method. If I don't use that table how do I know what assemble is correct based on the calculation results?

Thanks in advance,
Brian


Use Annex H. Note that there is a TIA out there for 70E-2015 that harmonizes the table you referred to and Annex H.

No need to use "categories" and the way you've written it is not correct. It's:
PPE 1 = 0-4 cal/cm2
PPE 2 = 0-8 cal/cm2
PPE 3 = 0-25 cal/cm2
PPE 4 = 0-40 cal/cm2

So note right off that PPE 4 will work for anything below 40 cal/cm2 for instance.

BUT I suggest you don't even bother with these values for two reasons.

First and foremost, you will need to use the lowest ATPV of the clothing ensemble that you select. Typically treated cotton pants run around 10-12 cal/cm2 or higher while treated cotton button down shirts run around 9-12 cal/cm2. Knit shirts run closer to 6-8 cal/cm2, and very little available gets down below that. So automatically except for the face shield consideration there is very little value in the PPE 1 category and you can crank the PPE 2 rating up higher. I would suggest that you try to stay as much as possible in this range because this is all single layer PPE. Single layer PPE does not add to heat load of the user any worse than standard industrial workwear and it is considerably more comfortable from a dexterity point of view. Annex H allows you to go as high as 12 cal/cm2 with appropriately rated PPE without getting into multilayer flash suit territory.

With PPE 3 there are two options available in this range. The first one is to not bother if you are purchasing multilayer flash suits. There is little practical difference between PPE 3 and PPE 4 so most users opt to simply skip PPE 3 altogether. The second and more interesting option is considering using an ensemble of clothing. For instance quite often you can put on a pair of coveralls or some other second layer as long as it is a tested combination and hit somewhere around 15-35 cal/cm2 without a multilayer flash suit and this combination will be a little more comfortable and less expensive than keeping something separate around. If you are going to have to supply winter clothing or rain suits, then just check with the manufacturers to ensure that you are using a rated combination. This will retain most of the single layer advantages and works much better than expected (would exceed for instance 8 cal shirt + 8 cal jacket) because the layer of air trapped between the two layers of clothing adds to the ATPV.

Finally if you have a lot of "high cal" areas you may want to consider 100 cal/cm2 suits. These are obviously expensive and heavy and visibility through the face shield is terrible but it's available. The alternative is to stop and switch to procedures that minimize or eliminate exposure at a point below 40 cal/cm2. In practice I have found that the percentage of additional buses is often a very small minority that get added to the "no PPE available" category if you take this approach. So before going too far with this, get a list of busses together that exceed 25 cal/cm2. Take a good hard look at what they are, where they are, if there are ways to reduce the values, if there are alternatives to working on them energized, etc. Pay particular attention to anything over 15 kV or extremely high fault current because all the software packages out there produce fictional (Lee based) values but is provably invalid.


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 Post subject: Re: PPE based on incident energy method
PostPosted: Tue Apr 26, 2016 10:33 am 
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Thank you!

When it comes to 'cranking up to PPE 2' to simplify PPE required for any locations with energies in the 0-8 cals, I had a question.

If my arc flash label says 'Minimum AR rating of 8 Cals' does that mean that all level PPE#2 clothing + protective equipment is required? If the calculations I come up with indicate only a 3.0 Cal incident energy but we have standardized on minimum 8 Cal AR does that mean all the clothing & equipment that comes with 8 Cal or PPE#2 assemblies must be worn & used? Put it another way - is it unreasonable or not appropriate to require min. 8 Cal AR PPE but only require PPE#1 clothing items and protective equipment? That way we standardize on the performance of the clothing & equipment but don't force particular items to be used (i.e. a balaclava) if the energy calcs don't demand it.

If I label for min 8 Cal AR rating but I don't want to force the use of a balaclava (required per Table 130.7(C)(16) for PPE#2) when the calcs show lower than 4 cals would the use of the balaclava be mandatory?

Sorry for splitting hairs but before I discuss PPE standards with management I want to understand what I'm allowed to recommend vs. what makes the most sense & is general acceptable practice, etc.


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 Post subject: Re: PPE based on incident energy method
PostPosted: Tue Apr 26, 2016 11:51 am 
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"Minimum AR rating of 8 Cals" means that every piece of PPE (clothing and equipment) has to have an ATPV of at least 8 cal/cm2. Shirt, pants, balaclava, face shield, and you wear your hard hat, your safety boots, and rubber gloves (or arc rated leather gloves.

In my facility, I prefer to put the actual incident energy value up. Then, if the incident energy is 10.6 cal, I can wear all PPE that meets 10.6 cal, rather than having to wear all clothing that meets 25 cal.


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 Post subject: Re: PPE based on incident energy method
PostPosted: Tue Apr 26, 2016 12:20 pm 
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Thanks Guys,

I understand better the PPE levels and can see how rounding up will simplify labeling. I'm wondering if I must stick to the prescribed set of clothing & protection items for PPE#1, PPE#2, etc. if I am rounding up to keep to a few standardized AR thresholds.

For example - if I want to label all my panelboards at 120/208V which are fed by <125KVA transformers with '8 Cal AR PPE Required' can I also allow the electricians at those panels to wear only those specific clothing & equipment items required within the PPE#1 category (hence they don't have to wear a balaclava)? In this case, even though the label says 8 Cal (implying the full set of PPE#2 clothing and equipment should be used ) I wouldn't require a balaclava since it is not required of PPE#1 clothing per Table 130.7(C)(16).

Perhaps I'm talking myself in circles and confusing the issue more.


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 Post subject: Re: PPE based on incident energy method
PostPosted: Tue Apr 26, 2016 12:42 pm 
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DMB5mil wrote:
Thanks Guys,

I understand better the PPE levels and can see how rounding up will simplify labeling. I'm wondering if I must stick to the prescribed set of clothing & protection items for PPE#1, PPE#2, etc. if I am rounding up to keep to a few standardized AR thresholds.

For example - if I want to label all my panelboards at 120/208V which are fed by <125KVA transformers with '8 Cal AR PPE Required' can I also allow the electricians at those panels to wear only those specific clothing & equipment items required within the PPE#1 category (hence they don't have to wear a balaclava)? In this case, even though the label says 8 Cal (implying the full set of PPE#2 clothing and equipment should be used ) I wouldn't require a balaclava since it is not required of PPE#1 clothing per Table 130.7(C)(16).

Perhaps I'm talking myself in circles and confusing the issue more.


Personally I've never agreed with the "no balaclava at 4 cal" rule. 4 calories to the back of the head is still going to do a lot of damage. Also, the tables don't apply unless you are actually using the tables. Making up your own categories based on IE calculations makes you ineligible to then use the tables to determine PPE needs.

If you want to have a "no balaclava level" than you should make a level that doesn't go over 4.


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 Post subject: Re: PPE based on incident energy method
PostPosted: Wed Apr 27, 2016 12:52 pm 
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DMB5mil wrote:
Thanks Guys,

I understand better the PPE levels and can see how rounding up will simplify labeling. I'm wondering if I must stick to the prescribed set of clothing & protection items for PPE#1, PPE#2, etc. if I am rounding up to keep to a few standardized AR thresholds.

For example - if I want to label all my panelboards at 120/208V which are fed by <125KVA transformers with '8 Cal AR PPE Required' can I also allow the electricians at those panels to wear only those specific clothing & equipment items required within the PPE#1 category (hence they don't have to wear a balaclava)? In this case, even though the label says 8 Cal (implying the full set of PPE#2 clothing and equipment should be used ) I wouldn't require a balaclava since it is not required of PPE#1 clothing per Table 130.7(C)(16).

Perhaps I'm talking myself in circles and confusing the issue more.


My recommendation isn't just to round up but suggesting that the levels in the table (1.2/4/8/25/40) are not ideal in the real world and that a different set of levels is perhaps more appropriate. Here is what I mean by an alternative that matches Annex H:

1. Up to 1.2 cal/cm2...nothing required. As in nothing. That includes the "exception" from IEEE 1584. This is as per the current (2015) version of 70E. The reason by the way that nonmelting clothing and any other "H/RC 0" requirements disappeared is that even untreated materials have a pretty good ATPV.
2. Up to 4 cal/cm2...arc rated shirts and pants or an arc rated coverall plus the other "stuff" on the list (ear plugs, hard hat, etc.). Frankly it doesn't matter what the arc rating is because you won't find any PPE with an ATPV that low. This means that the worker may be wearing an ATPV 10 shirt and ATPV 12 pants but since the face is underprotected we go by the lowest rating.
3. Up to somewhere around 8-12 cal/cm2...arc rated shirts and pants or alternatively a coverall plus the balaclava. Pick whichever level you feel most comfortable supporting from a vendor point of view, the higher the better. This would again go by the LOWEST ATPV of the PPE that are supplied. The table in 70E suggests ATPV 8 but frankly you won't find very much that is that low. A 12 oz./yd2 woven work shirt will usually be 10-12 cal/cm2 and denim jeans or duck pants will typically be at least 12+ ATPV while lighter duty twill pants are usually at least 8-10 cal/cm2.
4. Above 12 cal/cm2 a full hood is required and replaces the face shield and balaclava but nothing else. In addition the available PPE is going to be multilayer in nature. However if you make sure to specify and use a tested combination such as an arc rated shirt+pants and a set of coveralls or say the same shirt/pants plus arc rated rainwear or the same shirt/pants plus arc rated winter wear (overalls and jacket) even though individually these components may only have an ATPV of say 10-12, the combination quite often will be somewhere in the neighborhood of ATPV 20-35. I have not yet seen a combination that hits ATPV 40. So if you already issue and specify rainwear or winter outerwear or supply coveralls in addition to or in lieu of shirts and pants, you can use the rated combination to achieve an ATPV in the same range as PPE 3/4, especially if you eschew going any higher than this tested combination.

Finally when it comes to gloves, Arcwear has tested several brands and varieties of leather gloves as well as rubber gloves. What they found is that almost all the rubber gloves are at least ATPV 40 in combination with leather protectors. Similarly they found that leather gloves are at least ATPV 12. This is the reason that 70E lists these two types of gloves. Note that there is NO ATPV rating in this case...it's either a leather or rubber glove (with leather protectors) or it's not. There are cotton mittens on the market that are actually arc rated with an ATPV rating but there are three problems with them. First they offer no shock protection so they are not a replacement for rubber gloves (when required). Second they are soiled much more easily than leather gloves and at the price, they are definitely not disposable. Finally they really don't offer much abrasion resistance. So there's little reason to recommend them except for some switching situations.

And don't get too hung up on the glove issue. Try this...take an incident energy rating and change the working distance down to hand distance...say 2.5 cm (1 inch). What happens to the incident energy? Yep...sky high. This is where two things become obvious. The first one is that IEEE 1584 (and 70E) are not really intended to prevent injuries with PPE. In fact IEEE 1584 is designed around a 95% confidence interval of preventing a 2nd degree or more severe burn but ONLY in the most vulnerable part of the body...the face and chest area. There is no guarantee whatsoever that it will prevent a serious injury, only that a fatality is pretty unlikely.

And second and more importantly it highlights a more fundamental issue. The hierarchy of controls in 70E states that PPE is the last resort for protecting workers against hazards. Everything else (LOTO, EEWP's, maintaining equipment as per chapter 2) is designed around preventing workers from being exposed to hazards...lowering the risk. PPE NEVER prevents exposure to a hazard. It merely lowers the injury caused by the hazard. AND especially when it comes to voltage rated gloves and shock protection, PPE can and does fail so using it does not in any way prevent injuries at all. It MAY lessen the shock or arc flash to a tolerable level but it doesn't do anything to prevent the hazard in the first place. In fact given that all PPE is cumbersome and reduces visibility, decreases dexterity, increases risks to heat stroke, and has a tendency to cause workers to think they are superman and can take unnecessary risks, it becomes obvious why PPE is the worst solution available and not the best and should never be the first solution.


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 Post subject: Re: PPE based on incident energy method
PostPosted: Thu Apr 28, 2016 4:54 am 
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We (at the last two places I have worked) buy a 12 cal light jacket for each worker, and make sure that their face shield and balaclavas are rated for at least 12 cal. I find you often end up with lots of things in the 8 to 12 cal range.


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 Post subject: Re: PPE based on incident energy method
PostPosted: Thu Apr 28, 2016 1:26 pm 
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Thanks Guys. PaulEngr - I greatly appreciate you delving in so deep into the theory & thought process behind all of the subjects involved. Very interesting, complex, and timely discussion.

As an engineer I find electricity fascinating - would never have guessed the process of protecting a person from electricity can be fascinating in its own right!


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