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 Post subject: Non-Standard Working Distances on Arc Flash Labels
PostPosted: Mon Jul 16, 2012 8:21 am 
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There are situations where increasing the working distance a few inches from the IEEE-1584 standard can mitigate the incident energy hazard. In the attached example, increasing the working distance from 18 inches to 22 inches “reduced” the hazard from over 40 cal/cm2 to exactly 40 cal/cm2. I’ve read posts in this forum where people mention non-standard working distances as a mitigation option, but I haven’t seen specific examples of the labels. I’m posting my proposed labeling scheme for your (constructive) feedback.

The attached example is for a building 800A main distribution panel. The top label shows that the location is “dangerous” and shouldn’t be worked on while energized at the standard working distance. The next label would be placed directly underneath the standard label. The purpose of the non-standard label is to indicate the non-standard-working-distance and the non-standard-hazard.

I recognize that some people will think this may not be a good idea (http://www.arcflashforum.com/threads/1204/#post-5996). I recognize that to safely use these labels there would need to be additional procedures for my facility’s electrical safety work practices program. I recognize that there are additional liability concerns when deviating from the IEEE 1584 standard working distance. I recognize that at some distance, it would be inappropriate to expect safe work to take place.

Expensive new equipment mitigation solutions are just not realistic for many existing facilities. These labels could be helpful and appropriate for hot stick situations. These labels could be helpful at locations with 40.5 cal/cm2 available. These labels are not the solution to all the world’s arc flash problems, but I believe they could be part of the solution for specific situations. I’ve seen plenty of standard arc flash label examples, how about sharing your “non-standard working distance label”? How about some feedback on my proposed label?


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PostPosted: Mon Jul 16, 2012 9:28 am 
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Woking distance is the choice of the study eng. The concern is how will the eng. explain his choice (to a jury of lay people!!) when he's on the witness stand in court.

Personally, I find it marginally acceptable but with raised eyebows. I'd want to hear the motivation & justifiction before passing judgement.

While 39.9 is workable technically, there are other issues to consider. Realize that incident energy a single number that represents two primary hazzards. Those being concussive and heat. They are lumped together in 1584 obviously but are quite different items. Consideration must be given to both. Especially when deviating from the standard.

Bill Swingle P.E.


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PostPosted: Mon Jul 16, 2012 10:03 am 
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Location: richmond, VA
I agree that working distance is the choice of the study eng. I would never choose a larger working distance just to make the numbers come out to my liking. If there is good sound reasoning to believe that the worker will be at a distance different then 18 inches, ( closer or farther) then by all means use that in the calculations.


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PostPosted: Mon Jul 16, 2012 10:13 am 
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Before you start to change the working distance, you must first realize what the working distance is. It is the distance from the worker's torso (chest) area to the source of the arc flash. The real question is, "If you increase the working distance, can the worker still perform the task(s)?". In many cases, the answer is no. The only thing that the worker may be able to do is look at the equipment from the increased distance (working distance).

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PostPosted: Mon Jul 16, 2012 10:40 am 
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Robertefuhr wrote:
Before you start to change the working distance, you must first realize what the working distance is. It is the distance from the worker's torso (chest) area to the source of the arc flash. The real question is, "If you increase the working distance, can the worker still perform the task(s)?". In many cases, the answer is no. The only thing that the worker may be able to do is look at the equipment from the increased distance (working distance).


For the sake of conversation, let's say we increase the working distance from 18 to 19 inches. We probably agree that the same tasks are possible. If a customer of yours requests a non-standard working distance, how do you handle this? Do you use your standard label (http://powerstudies.com/services_arcflash.htm) or do you alter it in someway to draw attention to the unusual working distance? Does your firm offer non-standard working distance labels?


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PostPosted: Mon Jul 16, 2012 10:45 am 
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We have performed over 500 arc flash studies. I can only think of one customer, and his six sites where we deviated and changed the working distance. We try to not do deviate from the IEEE 1584 Standard but if our client insists that we use nonstandard working distances, then we will comply with their request.

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PostPosted: Mon Jul 16, 2012 11:32 am 

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I've work for a power companies; we have done studies in plants and the distribution systems. We calculated up to 36 inches of working space. This is the shot Gun stick min. length where the hands approach the restricted area. We have completed some for 12 inches where 18 inches did not work. We do a lot of training and mostly dress to cat 2 levels with the exception of some breaker switching. We also use the NESC rules where they apply. 4-8-12 cats. (401) with Heat flux index values. We are ready to explain in detail our study, findings with documentation to back it up. (CYA) We also use SKM software. The assessment is necessary to calculate energy exposure or our know hazard but remember OSHA is the governing body. Yes, OSHA can incorporate by reference NFPA 70E but you better have your training completed. So do all your assessments put up all the labels do all the studies but without training its worthless. I've seen a lot of completed assessments where the employees did not know the difference between a limited approach boundary to a Prohibited boundary. So.. what is a non standard working distance? More then 16 or 18 inches used in the 1584 IEEE NO... it is where the work being performed with in adverted movement into the restricted boundary. So in other words if I have a 48" inch restricted boundary, I better have a tool or device (wand) where I don’t approach it and dress to that calculated occasion.



J&B electrical services.


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PostPosted: Mon Jul 16, 2012 11:48 am 
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Joe,
What did your label look like for the facilities with unusual working distances? How did you call attention to the unusual distance? Did you use your standard label and simply change the working distance?


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PostPosted: Mon Jul 16, 2012 12:43 pm 

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Location: Camp hill Pa
There are somethings where it mightbe approiate. For example the equipment is considered live until Tested. With long probes a person can check for voltage presnce with a close approach. Also I note that at one transit company, some DC high current switches that have handles for hand operation, are instead operated with hooksticks by persons standing 8 or more feet away.


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PostPosted: Mon Jul 16, 2012 1:14 pm 

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MattB wrote:
Joe,
What did your label look like for the facilities with unusual working distances? How did you call attention to the unusual distance? Did you use your standard label and simply change the working distance?
We used the Blue labels instead of the orange. This gave everyone notice that the so called standard measurement was not used. Our Blue labels indicated special conditions not just equation distances changes. I should of mentioned that. It has all the standard energy exposures boundaries.
We never get stuck on the so called standard distances. We train our guys to read the labels. Set boundaries and have a tailboard meeting stating those boundaries. This should be covered in the Energized Work Permitting and hazard risk assessment. I would not add more then 1 label, however you need a reason and documentation. The 18" is set from your hands holding a tool to your chest. So in other words your hand inadvertently moves into the restricted boundary but never the core of your body. So.. moving the boundary to get a lesser reading; I would not recommend it, Look at Engineering it out. Look at your upstream devices, What about remote racking or limiting fusing or shorten the time duration on the breaker. Label: Deenergize before servicing.

Example: I have a 6.9KVmotor application that needs megging, If I run the calculations at 18" it exposure is 45cals. We only have 40 cal suits. I use a hot stick 2 foot long. I can run the calculation at 32" The energy exposure at this distance is 24 cals. We verify the no voltage and meg. LOTO... On the procedures for megging it will have a 24"hot stick to verify the voltage.

Example: Some equipment have parallel feeds, So the label will state Isolation or splitting the feeds in the procedure. Some things we have to shut down to work on, its just a fact of life. We have run exposures over 100 cals.

I'm an out reach trainer of OSHA the CFR1910 and 1926, Your procedures for energized hot work permitting would be more important then the labels. OSHA doesn’t care that you use 10" or 20" just be ready to tell them why. Standardized practices carry a lot of weight. You need to have reasons or justifications. Not that you only have 40 cal suits... Its how you handle electrical safety program, Hazard risk evaluations or assessments to the know hazard. Every elect. task should have a procedure. What made the employee a competent qualified electrical worker. (TRAINING) U better have it and I suggest having it outsourced.

This has become a money game and people are playing and twisting the facts.


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PostPosted: Mon Jul 16, 2012 1:50 pm 
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Joe,
Thanks for the input, that sounds like wise advice.


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PostPosted: Mon Jul 16, 2012 8:56 pm 
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Location: Calgary, Alberta, Canada
There is no liability deviating from IEEE P1584 it is not adopted into law. You can change the default Working Distances, just need to make sure Qualified Electrical Workers maintain the WD to their face and torso when doing arc flash risk work on the equipment with the label with whatever WD is on it.

Changing the WD is a mitigation option.

Joe's comments are bang on, especially his last statement. Document what you do and why in your Electrical Safety Program!!

Regards;
Terry Becker, P.Eng.
Owner, ESPS Electrical Safety Program Solutions INC.


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PostPosted: Tue Jul 17, 2012 12:13 pm 

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Location: Baltimore, MD
I do not believe the working distances should be altered. In the real world, workers often ignore rules. Even if the official documented boundary is twenty inches, workers will approach within arm's length of the equipment to operate it. Aside from the moral argument, imagine trying to explain to a lay jury why you, the engineer, recommended a deviation from the accepted standard distance.


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PostPosted: Tue Jul 17, 2012 12:20 pm 
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Hurwitz wrote:
I do not believe the working distances should be altered. In the real world, workers often ignore rules. Even if the official documented boundary is twenty inches, workers will approach within arm's length of the equipment to operate it. Aside from the moral argument, imagine trying to explain to a lay jury why you, the engineer, recommended a deviation from the accepted standard distance.

In my view, hook-stick operations would be a very good reason to increase the working distances. It should be difficult to do the same operation without a hook-stick.
Also, for equipment where the default working distance is too high for whatever reason (rear access, etc.), but then it will increase the Ie, not reduce it.


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