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 Post subject: >40 cal. Label
PostPosted: Fri Mar 02, 2018 6:45 am 

Joined: Wed Jul 12, 2017 6:06 am
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Since the 40 calorie reference has been eliminated in 2018 70E, what information should be on the label for calculations that result in greater than 40 calories? Currently we produce a label that states DANGER DO NOT WORK ON WHILE ENERGIZED NO SAFE PPE EXISTS! The label still has incident energy and working distance. Does this mean you can now work on stuff > 40 calories? We have been training people for over ten years that you cannot work on anything greater than 40 calories.


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 Post subject: Re: >40 cal. Label
PostPosted: Fri Mar 02, 2018 9:15 am 
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ewbengineering wrote:
We have been training people for over ten years that you cannot work on anything greater than 40 calories.


NFPA70E has never actually treated above 40 calories any differently than lower number. It has always been up to the employer to determine the proper PPE. But, because the 'task tables' and PPE selection tables in NFPA70E only went as high 40 calories, most companies, and instructors, chose that level as their cutoff point.

Personally, I have never liked the practice of calling >40 calories as 'Dangerous' as that implies that lower values are not dangerous. I kind of like using 'Prohibited' instead.


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 Post subject: Re: >40 cal. Label
PostPosted: Fri Mar 02, 2018 12:49 pm 

Joined: Wed Jul 12, 2017 6:06 am
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In 70E 2015 there was a reference in 130.7 Information note #3 that if the IE exceeded 40 calories, greater emphasis may be needed with respect to de-energizing the equipment. That and the table not going above 40 cal is why most folks make the cutoff at 40 cal. It appears the note in 130.7 has been removed in the 2018 version. So should the labels still say PROHIBITED or should they have something different?


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 Post subject: Re: >40 cal. Label
PostPosted: Fri Mar 02, 2018 5:05 pm 
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There are arc flash suits well over ATPV 100 so it's not a real limit. The only idiots producing "danger" labels were the software vendors. According to ANSI Z35 which is the safety sign standard all arc flash labels must be warning, not danger. Those labels violate the label standard. So does NEC shock hazard labels though.

70E only stated greater emphasis, not what it should be. So it was removed like prohibited approach boundaries because it was extraneous.

You should recognize that SOME work can and must occur above the level at which PPE is available for use no matter how high. It's a matter of establishing that. Maybe 12 xal/cm2 makes more sense for some or 100 cal/cm2 for others. It's important to discuss what work CAN be done at that point and workarounds to do it safely instead of putting stupid tags up that leave no options available.


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 Post subject: Re: >40 cal. Label
PostPosted: Sun Mar 04, 2018 10:12 am 
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ewbengineering wrote:
In 70E 2015 there was a reference in 130.7 Information note #3 that if the IE exceeded 40 calories, greater emphasis may be needed with respect to de-energizing the equipment. That and the table not going above 40 cal is why most folks make the cutoff at 40 cal. It appears the note in 130.7 has been removed in the 2018 version. So should the labels still say PROHIBITED or should they have something different?


The Prohibited value, if used, should be a choice made by each employer as they create and update their Electrical Safe Work Practices program.

My guess is that '40 cal' will still be a common cut-off point.


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 Post subject: Re: >40 cal. Label
PostPosted: Mon Mar 05, 2018 8:24 am 

Joined: Mon Dec 07, 2015 9:45 am
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Location: Massachusetts
I was of the understanding that OSHA had placed the >40cal level in the Dangerous, do not work on live level?


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 Post subject: Re: >40 cal. Label
PostPosted: Mon Mar 05, 2018 9:05 am 
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Location: Lima, OH
OSHA provides no guidance with respect to arc flash label content.


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 Post subject: Re: >40 cal. Label
PostPosted: Mon Mar 05, 2018 11:27 am 
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Hi All

Greetings from the Great White North. I agree with Paul's comments particularly the last paragraph where it is referenced that work may have to be done on equipment that has a greater than 40 cal/cm2 rating. If in fact 40 cal/cm2 is our number?? Cn we look at defining the work? If it is racking or switching can one consider remote? As these devices seem to becoming more popular out there. For verification of presence or absence of voltage 70E, 2018 indicates that a PESD can be used. In this case the worker does not have to open a door to check for power

Thanks

Len


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 Post subject: Re: >40 cal. Label
PostPosted: Tue Mar 06, 2018 9:40 am 
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I must again point out the paradox in prohibiting energized work at any level. Since it must be considered energized until tested, the testing itself is considered energized work. Such a rule prohibits all work.


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 Post subject: Re: >40 cal. Label
PostPosted: Tue Mar 06, 2018 3:32 pm 
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stevenal wrote:
I must again point out the paradox in prohibiting energized work at any level. Since it must be considered energized until tested, the testing itself is considered energized work. Such a rule prohibits all work.


Not quite. There is plenty of work that can be done without coming into contact with conductors, direct or otherwise, such as switching, reading values, etc.

Second, this is where 70E kind of falls apart. IEEE 516 which is what OSHA's shock protection rules are based off of has multiple methods for doing energized work safely while avoiding shock hazards including rubber glove, insulated platform, bare-hands/live-line, and insulated tool work. This is where they stop.

So the question to ask yourself is two fold. First can we take a voltage reading while controlling the shock hazard? OBviously the answer is yes because otherwise IEEE 516 wouldn't even exist. The next question is can we take voltage readings WITHOUT creating a situation where there is a potential to create an arc? Here is also where I would have to say yes. All decent quality meters these days come with tip covers that leave such a minimal amount of probe exposed that it is not possible (extremely remote risk) of bridging the contacts. Furthermore when you open MOST gear it is already reasonably well insulated so that it should not even be considered exposed when the doors are open. So either a shock hazard may exist or it doesn't (and we can use PPE to mitigate this) and also if we do it with the correct tools, no reasonable arcing fault potential exists so no arc flash hazard exists.

SO we can test for absence of voltage if we take necessary precautions.

Moving on to the other direction...what if for instance I have say a cord-and-plug circular saw? If I unplug it, is it still "live"? Do I really need to test for absence of voltage? In older editions of 70E the answer was no and I think most people assume if it's unplugged, it's dead. This is also how utilities do it...there needs to be a VISIBLE air gap. There is still stored charge potential but this is vastly less and the incident energy is not normally a big problem. This also applies to for instance the NEC rule about having a disconnect nearby a motor, etc. The complication comes in when it's not possible to positively identify which cable goes where. That's where we are really double protecting...we are both disconnecting AND testing to make sure the dsconnection procedures worked.

If you assume all live equipment is an arc flash waiting to happen and don't consider whether or not there is a reasonable possibility of the hazard occurring which is the approach some have taken, you paint yourself in a corner and there is no way out.

Note also that PESD's are acceptable by 70E but NOT by OSHA so they are not a solution for LOTO at least in the U.S.


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 Post subject: Re: >40 cal. Label
PostPosted: Wed Mar 07, 2018 10:44 am 

Joined: Mon Dec 07, 2015 9:45 am
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Location: Massachusetts
PaulEngr wrote:
The next question is can we take voltage readings WITHOUT creating a situation where there is a potential to create an arc? Here is also where I would have to say yes. All decent quality meters these days come with tip covers that leave such a minimal amount of probe exposed that it is not possible (extremely remote risk) of bridging the contacts. Furthermore when you open MOST gear it is already reasonably well insulated so that it should not even be considered exposed when the doors are open. So either a shock hazard may exist or it doesn't (and we can use PPE to mitigate this) and also if we do it with the correct tools, no reasonable arcing fault potential exists so no arc flash hazard exists.


There is definitely a danger with a lot of equipment, especially older equipment and some equipment designs that did not take into consideration arc flash dangers, where just the attempts to open the equipment present an arc flash hazard. So the personnel would not even get to the testing part, they'd still be in the preparing for testing stage, where the integrity of the equipment has been compromised but they have not begun testing. So an arc flash hazard exists, not because of improper tools or lack of PPE, but because the inherent design of that equipment does not take into account arc flash hazards.

This is the part where our electricians, test tech's, and field engineers voice their concerns with the work to be performed.


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 Post subject: Re: >40 cal. Label
PostPosted: Mon Mar 12, 2018 7:58 am 

Joined: Wed Jul 12, 2017 6:06 am
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Good discussion! I guess the closest response I have seen as an answer to my question is that the cutoff should be left to the employer. I was under the impression that the 40 cal reference was because in testing it was determined that the elements of the arc blast may not be survivable if it was above 40 calories. We recognize you can wear a 100 cal suit but at that level it isn't a burn issue as much as a blast issue that causes the problems. To Paul's point if everything was always right and in a perfect world we wouldn't be doing this work. We all know in reality equipment isn't always maintained properly, equipment can fail, Technicians can use the wrong type meter etc, and we want everyone to go home safe at the end of the day. So what would your >40 cal/cm2 label say?


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 Post subject: Re: >40 cal. Label
PostPosted: Mon Mar 12, 2018 6:19 pm 
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ewbengineering wrote:
Good discussion! I guess the closest response I have seen as an answer to my question is that the cutoff should be left to the employer. I was under the impression that the 40 cal reference was because in testing it was determined that the elements of the arc blast may not be survivable if it was above 40 calories. We recognize you can wear a 100 cal suit but at that level it isn't a burn issue as much as a blast issue that causes the problems. To Paul's point if everything was always right and in a perfect world we wouldn't be doing this work. We all know in reality equipment isn't always maintained properly, equipment can fail, Technicians can use the wrong type meter etc, and we want everyone to go home safe at the end of the day. So what would your >40 cal/cm2 label say?


Arc blast has nothing to do with it. There has been quite a bit of open dialog about this from those who were "there" in the early (1990's editions) days of NFPA 70E development. The best explanation I've heard is that at that time they adapted welder's greens (the so-called "pickle suits") for use for arc flash. At that time the best available material was limited to 40 cal/cm2. So this makes a lot of historical sense.

As to arc blast, there is no explanation for where this pure myth/rumor came from. Simply put, nobody has ever done an accident investigation due to an arcing fault where the victim suffered blunt force trauma similar to an explosion. The highest pressures recorded from arcing faults on equipment get up to around 10 PSI maximum, and the threshold for potential fatalities is somewhere between 20 and 100 PSI, and that 10 PSI has only been recorded inside an enclosure when it is pressurizing, not once it blows open. This is only with purposely sealed containers. The vast majority of electrical enclosures aren't really sealed very well so this pressure level simply doesn't happen. There's also an argument dealing with copper vapor that turns out not to be valid according to recent experiments by Hugh Hoagland's group. I've done some theoretical calculations (posted in the articles section) that show that even with the worst case measured scenarios the arc blast pressure by the time it reaches a typical working distance is possibly enough to blow out someone's ear drums but that's it. Also the cases documented by Neal et al in a long laundry list of about 55 arc flash incidents (the most comprehensive list out there) include at least one case where the individuals were exposed to an estimated 80 cal/cm2 incident energy but were nowhere near that level of PPE and suffered relatively minor injuries. That's not to say that just wearing any PPE is sufficient regardless of the incident energy, or that there is something wrong with the calculations, but that just because incident energy is higher than the PPE, it has a pretty good probability that it will still work anyways. This lends credence to the idea that some PPE is better than nothing.

As to what to put on the label...just post the incident energy at the working distance and the arc flash boundary and leave it at that. This is what is in NFPA 70E. If you go down the route of listing PPE and the PPE changes either because of local plant decisions or because 70E changes in some way, it invalidates some or all of the labels.

Not only that but according to ANSI Z535 the signal word "DANGER" is specifically reserved for cases where there is an imminent danger of an injury. Basically if you don't take specific precautions against it, a serious injury or fatality WILL be the result. The signal word "WARNING" is for when death or serious injury might happen. So the correct word for all arc flash labels following ANSI Z535 standards is WARNING, never DANGER. OSHA references ANSI Z535 as does 70E and NEC. So for instance a cover over a hatch that allows access to a spinning blade would use the word "DANGER" but an arc flash hazard would use the lesser word "WARNING". Between about 1 in 10 and 1 in 20 cases of arc flash turns into fatalities and there's not much of a pattern to it. Arc flash injury rates according to ESFI data are about half as frequent as electrocutions (about 1 in 100,000 workers per year) so it hardly qualifies as a common or frequent accident. It's just that if an injury does occur, it's pretty much a guaranteed trip straight to a burn unit or the morgue.


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