PPE

[Ray83]

We have arc flash ratings labeled on our switch gears and one of them say 40.38 cal. Should we buy a 50 cal? And anything pass 40 cal ( even if it's that .38 ) is that pretty much a major kaboom ?

 

[Fulthrotl]

We have arc flash ratings labeled on our switch gears and one of them say 40.38 cal. Should we buy a 50 cal? And anything pass 40 cal ( even if it's that .38 ) is that pretty much a major kaboom ?

40 cal. is the peak level breakpoint.

what i was told by the fellow who gave me my arc flash training
is that ppe levels above 40 calorie didn't accomplish much, as a
level much above 40 calorie will result in an explosion that will
kill you from the concussion.

if you are, for whatever reason, in a hot work situation with an
arc flash rating above 40, you really need to pause and rethink this.

 

[jim dungar]

what i was told by the fellow who gave me my arc flash training
is that ppe levels above 40 calorie didn't accomplish much, as a
level much above 40 calorie will result in an explosion that will
kill you from the concussion.

This type of 'fear statement' was commonly taught more than 10 years ago. However, the concussion force, arc blast, and the incident energy, arc flash, are not directly related.
It is very easy to have incident energy levels >40cal/cm^2 when the protective device does not clear due to relatively low arcing fault currents. This is why many people use a 2 sec cut off for their calculations.
Even levels <40cal/cm^2 can have an 'explosive force' which can produce shrapnel and concussions.

I believe the 40cal/cm^2 clothing 'limit' is likely to be removed in the 2018 edition of NFPA70E.

 

[wtucker]

A calorie is a measure of heat energy--in this case, heat energy at the arc. Energy of an arc in open air will be released omnidirectionally. An arc in a box will be contained until the box ruptures, producing a greater concussive wave, particularly when copper inside the box expands when it melts, possibly moving to its plasma phase.

 

[Fulthrotl]

I believe the 40cal/cm^2 clothing 'limit' is likely to be removed in the 2018 edition of NFPA70E.

granted that there was an applied fear factor in the training i was given,
and it was 10 years ago.

so then levels of protection may be calculated above 40 cal, and required?

note to self: if a level of protecting above 40 cal. is required, i don't need
a thicker suit. someone else needs a thicker suit.

 

[publicgood]

As noted by others, 70E pretty much tells you to de-energize above 40. Have you filled out an energized work permit for this to validate the need?

Is there a maintenance mode for arc energy reduction? Or access to the study software files to understand levels when the instantaneous is dialed all the way down?

 

[petersonra]

If you stood an extra inch farther away you'd probably be under 40 calories but I don't think you're allowed to take credit for that extra inch. I think at some point NFPA 70E is going to have to take practicality into account. I think NFPA is afraid of being sued so they are making it almost impossible to do anything.

 

[jim dungar]

I think at some point NFPA 70E is going to have to take practicality into account. I think NFPA is afraid of being sued so they are making it almost impossible to do anything.

NFPA70E-2015 says that a risk analysis (e.g. sanity check) must be performed to determine if the hazard will occur. After the risk analysis is done, steps be taken in order to mitigate the hazard. The very last thing to do is select appropriate PPE, partly because of limitations on it effectiveness.

An argument can likely be made that NFPA-70E wants to reduce, if not out right ban, energized work.

 

[publicgood]

An argument can likely be made that NFPA-70E wants to reduce, if not out right ban, energized work.

Agree. Really, the only live work that should be justifiable is IR scanning.

 

[jim dungar]

Agree. Really, the only live work that should be justifiable is IR scanning.

There is also some troubleshooting that requires energized equipment.

 

[publicgood]

There is also some troubleshooting that requires energized equipment.

Fair. Such as amp reading with clamp on meter.

 

[Coppersmith]

I carry hot gloves, helmet with face shield, and long sleeve FR shirt on the truck. All category 1. I put them on when I feel endangered such as when pulling a meter. If I have to wear category 2 and above, find yourself another boy. I'm not taking any chances this close to retirement.:happyno:

 

[Coppersmith]

I forgot to mention that I purposely wear a uniform shirt that is all cotton. It was extreme difficult to find a uniform shirt that wasn't some percentage of polyester which as we know will melt to your skin if you are exposed to an arc flash. Safety first. (My eyeglasses are safety rated, too)

 

[wtucker]

I think NFPA is afraid of being sued so they are making it almost impossible to do anything.

The great miracle of the United States is that anybody can sue anybody for anything. That's why NFPA includes this disclaimer:

"The NFPA disclaims liability for any personal injury, property or other damages of any nature whatsoever, whether special, indirect, consequential or compensatory, directly or indirectly resulting from the publication, use of, or reliance on NFPA Standards. The NFPA also makes no guaranty or warranty as to the accuracy or completeness of any information published herein."

Voluntary consensus standards (NFPA, ANSI, etc.) are one-size-fits-most "best practices," so they're conservative. Nothing stopping us from being more--or less--conservative, depending on specific circumstances.

 

[petersonra]

The great miracle of the United States is that anybody can sue anybody for anything. That's why NFPA includes this disclaimer:

"The NFPA disclaims liability for any personal injury, property or other damages of any nature whatsoever, whether special, indirect, consequential or compensatory, directly or indirectly resulting from the publication, use of, or reliance on NFPA Standards. The NFPA also makes no guaranty or warranty as to the accuracy or completeness of any information published herein."

Voluntary consensus standards (NFPA, ANSI, etc.) are one-size-fits-most "best practices," so they're conservative. Nothing stopping us from being more--or less--conservative, depending on specific circumstances.

You do understand that in court such a statement has little or no standing.

it is like those signs at the grocery store claiming the store is not responsible for damage caused by carts in the parking lot. It might be true, but it is not because they posted a sign disclaiming liability.

 

[zog]

We have arc flash ratings labeled on our switch gears and one of them say 40.38 cal. Should we buy a 50 cal? And anything pass 40 cal ( even if it's that .38 ) is that pretty much a major kaboom ?

Yep, big ba da boom. Instead of worrying about a better suit you should look at mitigation, usually very simple to do. I'm going to guess here and assume the main breaker for this gear does not have INST protection, in which case adding a maintenance switch is a simple solution.

 

[petersonra]

The other thing is that the arc blast is unpredictable, where as the IE is readily calculated, although the reality is that the IE calculation produces a worst case scenario that you might never come close to actually having.

One might think that the more IE you have the worse the arc blast will be, but it does not appear that is necessarily true.