As I read 130.7(10) in the 09 70e it states -- This clothing and equipment shall be used when working within the Arc Flash Protection Boundary.

Per 130.3(A)(1) -- Voltage levels between 50 & 600v --the AFPB is 4' if you meet the clearing time and fault current criteria.

In a "normal" building where we know the fault current is below is below 50kA how often is it that the clearing time is above 2 cycles? thus increasing the AFPB?

We are doing our best to use this safety program but if I can get my guys out of the AFPB by as much footage as possible then my PPE requirement questions go down a lot.

Unless I am totally missing something. Thanks for any input.

You have no PPE requirements once you are outside the AFPB. As far as the clearing times in your system, there are a lot of variables which can play into that time.

Also, if you do an actual arc flash hazard analysis of your system, you may find that your hazards are lower than what is in the tables or it may higher.

A lot to be said for remote operation.

A lot. Many MCCB's are faster than 2 cycles but the opening time for most vacuum interrupters and SF6 is 3 cycles. And neither includes the speed of the trip unit. If you are instantaneously tripping, then you pay attention to this "ultimate speed". But if your current is below this, there is almost no way you are tripping in less than 2 cycles even if you have an MCCB. So I would say based on your statement alone, in a "normal" building, the chances are slim to none that you meet this criteria as stated. You may want to go back and reread carefully. You also should get copies of the TCC's and work out a real example for equipment that you have. And most importantly, remember that cable/bus impedance is important for this. You can't just do the quick and dirty "transformer impedance is all that matters" assumption that works OK for calculating SCCR. Doing the calculations by hand is the reason most folks have given up and paid either for someone else to do it or bought a power system analysis software package.



That's also the reason for the EEWP rule...don't do it live if you don't have to.

You can't automatically drop the PPE by the way if you are out of the AFPB. Remember shock hazards are independent of arc flash hazards and may require PPE. If you are still within the approach boundaries for shock, PPE may still be required. This includes if you are outside the approach boundaries physically but the TOOLS are within the restricted or prohibited approach boundary. 70E is kind of silly in that they don't really recognize insulated tool work very well. They push for rubber glove work only which is silly and not recommended at some voltages (69 kV and over) since the gloves aren't rated that high. At some point it would be nice if they would clarify that there are 4 work methods for shock hazards (de-energized, insulated tools, rubber glove, live-line, bare-hands) and not be so hung up on gloving everyone and everything. They don't even do a good job of describing when/where coverup or sleeves are required.

In our facility, they have done the hazard analysis, and most of our panels are HRC 0 with a flash hazard boundary usually from 4 inches to 9 or 10 inches depending on the panel. Our company issues Fire resistant clothing rated up to HRC 2, which we wear all the time. We also always wear electrically rated hardhats . Safety glasses and earplugs are also always required. We have been issued gloves for shock protection also. We are a food plant and are required to wear hairnets and beardnets. We have just recently been issued the fire resistant hairnets and beardnets and I have a question about there use. Except for the hairnets and beardnets we already wear all the ppe needed for the HRC 0 panels. If my flash hazard boundary is 9 inches, and I keep my head out of that zone, do I need to put on the fire resistant hairnets and beardnets, or can I keep on the ones I wear now ?

Why don't you want to wear the AR hairnets and beardnets all the time? I wear them when I work in a FDA regulated facility and I don't find them any different than the regular ones. Why risk forgetting to change to AR ones when needed? Especially in an emergency situation. Why not consider them part of the HRC 2 company issued clothing?

There is no arc flash protection boundary that I am aware of that is based on meltable fabric. OSHA rightly forbids the wearing of these fabrics.

Many polymers melt at temperatures as low as around 135 F. If they melt and stick to the skin, they transfer much more heat to the skin than the original arc. This causes a much more severe burn than the arc flash itself. Nonmeltable fibers such as cotton and wool char instead of melting, which is relatively harmless. The draft 2015 edition of 70E now requires nonmeltable clothing for basically everything as a bare minimum for this reason and only introduces arc resistant PPE if the arc flash hazard gets over 1.2 cal.

[media=youtube]h10ALIpD0R4[/media] I have heard that meltable hair nets were involved here.