What's the difference between arc-rated pants and arc-rated arc flash suit pants? (NFPA70E) 1

[Dvhez]

I'm reading Table 130.7(C)(15)(c) Personal Protective Equipment (PPE) from NFPA 70E (2018) and I can't undesrtand the difference between these two types of pants. Although I search on google they look the same to me.

Also, this table has some items with (AN, AR and SR) which means:

AN: As needed (optional)
AR: As required
SR: Selection required

English is not my native language so I can't differentiate which is more serious (as needed / as required / selection required).

Thanks!

 

[dpc]

"Flash suit" generally has a higher arc rating. Generally over 8 or 12 cal/cm2, a full arc suit with a hood is required, although layering is another option. A hood is always required for level #3 and #4 in this table. AN would be optional depending on situation. AR just means that the total arc rating must equal the category maximum (25 cal/cm2 or 40 cal/cm2). Layering of arc-rated clothing generally results in a higher rating (if TESTED - you cannot just add the cal/cm2). So you just have to be wearing arc-rated clothing with a total arc-rating equal to the maximum required. There is more than one way to achieve this. SR just mean you can use either goggles or safety glasses under the hood or face shield.

It's poorly written so we all struggle to understand what they are trying to tell us.

Also, this table is only intended to be used if using the Tables in NFPA 70E. If calculating incident energy, there's a different table (130.5.G)

Cheers,

Dave

 

[Dvhez]

Thanks dpc!. Much clearer. Also, can I use PPE categories for voltage levels over 15 kV? The Table 130.7(C)(15)(a) Arc-Flash PPE Categories for Alternating Current (ac) Systems onyl specifies equipment from 240 volts to 15 kV.

 

[dpc]

The PPE requirements would not change above 15 kV for the same incident energy. But the Tables in NFPA 70E used to determine the "Category" only go up to 15 kV, so there is no way to use the Tables to determine the cal/cm2. You can calculate it using the Lee equations (see Annex D of NFPA 70E) or refer to the table in the National Electric Safety Code (NESC). It covers higher voltages.