Arc Flash Studies - Questions on 2018 NFPA 70E

[mshields]

Two questions on Arc Flash studies: Per the 2018 NFPA 70E, is it no longer the case that labels must have PPE levels 0-4.

And, can one neglect doing 208Y/120V panelboards fed via a certain size dry type transformer; say e.g. 112kVA or less and just state that these may be assumed to have an incident energy level such that Level 0 PPE will always suffice?

 

[petersonra]

I thought they got rid of level 0 altogether.

 

[wbdvt]

I am answering this based on your lead in stating Arc Flash Studies. If you read NFPA 70E-2018 Art 130.5(H)(3), it states that the label must contain either the available incident energy or the arc flash PPE category from the tables. However, Article 130.5(F) states that arc rated PPE shall be selected based on either an incident energy analysis or the arc flash PPE category method from the tables. Therefore, since an incident energy analysis (arc flash study) has been done, the label needs to have the incident energy level.

The 112kVA transformer and voltage exemption was from IEEE 1584-2002 which has been superseded and voided by IEEE 1584-2018. IEEE 1584-2018 now states that "Sustainable arcs are possible but less likely in three-phase systems operating at 240 V nominal or less with an available short-circuit current less than 2000 A."

 

[jim dungar]

I thought they got rid of level 0 altogether.

They did for those using the 'task tables'. For those using calculations NFPA70E describes to levels of PPE. 12 and 40 cal/cm^2.
However, there is also a provision for companies to have their own Site Specific requirements, so many companies continue to include 0, 1, 2, 3, and 4 as PPE categories because that is how their employees were trained.

 

[paulengr]

They basically eliminated PPE requirements under 1.2 cal/cm2. The task tables annoyingly just start at category 1. NESC and OSHA for utilities start at 2 cal/cm2 and have a minimum PPE of 4 cal.

Realistically though there are some knit shirts down to about 6 cal and some very thick work shirts and most jeans are up around 12 cal. Above that it’s multiple layers. So it really doesn’t make sense to have more than a 3 level system with none required, a shirt and pants level, and a winter overalls and jacket level with a hood. 25 cal and 4 cal levels are stupid...almost no difference from higher levels.


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[paulengr]

They basically eliminated PPE requirements under 1.2 cal/cm2. The task tables annoyingly just start at category 1. NESC and OSHA for utilities start at 2 cal/cm2 and have a minimum PPE of 4 cal.

Realistically though there are some knit shirts down to about 6 cal and some very thick work shirts and most jeans are up around 12 cal. Above that it’s multiple layers. So it really doesn’t make sense to have more than a 3 level system with none required, a shirt and pants level, and a winter overalls and jacket level with a hood. 25 cal and 4 cal levels are stupid...almost no difference from higher levels.

 

[milldrone]

Realistically though there are some knit shirts down to about 6 cal and some very thick work shirts and most jeans are up around 12 cal. Above that it’s multiple layers.

Paul,
I'm always looking to improve our situation. It appears you practice the multiple layers solution. Does you solution cause any confusion especially during the summer when your personnel are not wearing winter gear?

So it really doesn’t make sense to have more than a 3 level system with none required, a shirt and pants level, and a winter overalls and jacket level with a hood. 25 cal and 4 cal levels are stupid...almost no difference from higher levels.


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[paulengr]

No. Let’s be clear here. A 40 cal suit that you get from Oberon, Salisbury, etc., is essentially an FR set of insulated overalls and jacket. You can of course actually buy insulated winter PPE with say a 40 cal rating. You’d just have to add the hood to it. No confusion at all. I’d wear the 40 ATPV overalls and jacket I carry on the truck in winter but they are purposely thin for “summer” use and uncomfortably cold in winter.

Layering is another option. It is allowed but must be a tested combination. All of the testing in North America is done by E-Hazard. If the customer agrees they publish the combination and several manufacturers also publish the combinations they have tested. Surprisingly it’s better than expected. So for instance a 12 cal coverall over an 8 cal shirt will be far higher than 20 cals (8+12), often 25-35. Tested combinations generally exceed what you expect because the air trapped between layers is additional insulation. The nice option here is you might want to supply “everyday” 10 cal work uniforms with a balaclava and face shield for normal low level situations to be used with leather or rubber gloves. Then throw on the winter jacket and bibs or a similar rain suit to step up to say 35+ cal to save on PPE that has to be supplied. You can’t realistically work all day in a 40 cal suit even in temperature controlled spaces except cold storage,

The way to understand PPE is that the FR treatment just prevents it from continuing to burn after heat is removed. The insulative value (ATPV) is all due to the insulative value of the material. Published tests on untreated cotton shirt material reach 8-10 ATPV before it bursts into flame...same as Westex treated cotton. 70E states that single layer PPE can reach a maximum of 12 ATPV which we see with heavy materials like denim and cotton duck used in pants and overalls. To get higher ratings requires more layers either as a composite PPE like what “40 cal suits” are made of or else DIY tested combinations of layering,



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[Hv&Lv]

They basically eliminated PPE requirements under 1.2 cal/cm2. The task tables annoyingly just start at category 1. NESC and OSHA for utilities start at 2 cal/cm2 and have a minimum PPE of 4 cal.

Realistically though there are some knit shirts down to about 6 cal and some very thick work shirts and most jeans are up around 12 cal. Above that it’s multiple layers. So it really doesn’t make sense to have more than a 3 level system with none required, a shirt and pants level, and a winter overalls and jacket level with a hood. 25 cal and 4 cal levels are stupid...almost no difference from higher levels.


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We wear cat 2 clothing as part of our uniform in our utility.
heck, I’m wearing a category 2 long sleeve T shirt now...

cat 2, 8 cal

 

[paulengr]

We wear cat 2 clothing as part of our uniform in our utility.
heck, I’m wearing a category 2 long sleeve T shirt now...

cat 2, 8 cal

OSHA and NESC allow down to 4 cal but even a knit long sleeve Henley style “lineman’s shirt” on the market is 6 cal. A lot of true “T-shirts” are in this range. I have never seen any PPE that is actually category 1 or even close. It would have to be unbelievably thin to get that low. The lowest rating for button down work shirts is 8.6. Most are around 10. Pants run 10-13. That makes all typical button down shirts and pants “category 2”.



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[Hv&Lv]

OSHA and NESC allow down to 4 cal but even a knit long sleeve Henley style “lineman’s shirt” on the market is 6 cal. A lot of true “T-shirts” are in this range. I have never seen any PPE that is actually category 1 or even close. It would have to be unbelievably thin to get that low. The lowest rating for button down work shirts is 8.6. Most are around 10. Pants run 10-13. That makes all typical button down shirts and pants “category 2”.



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We used to wear cat 1. I still have some of them. Can’t wear them on the job.
yes, they are incredibly thin.
my ariat Henley style t shirt is cat 2