craigwilliams wrote:
Thanks for the replies.
How about this specific scenario:
We are working inside a panel. All power is isolated except for a 120Vac circuit which takes power in and then it goes directly back out of the panel. It does not feed anything else inside the panel. This is feeding a safety critical load at this time that cannot be turned off. We need to change a component in the panel in an area that is within 2ft of the live circuit but has been verified as de-energized. The decision is made to completely cover the live circuit terminals with electrically rated insulated matting in a way that it cannot move while work is being performed. A full JSA and permit is written explaining the risk assessment.
We have two questions:
1. Does this meet with NFPA70E and OSHA standards for safe work?
2. Does the technician still need to wear arc flash PPE to perform the work? I would think that covering the exposed live conductor means it is no longer exposed and therefore not an arc flash hazard.
Thanks
First before we do anything when we are talking about lockout/tagout which appears to be where you are going, did you know that there are literally over a dozen lockout procedures in OSHA regulations? I'm not talking about simply individual rules but whole procedures! The most well known is the general LOTO procedure. This is in 1910, Subchapter J. Even though it does not apply for instance to construction, it is the most often referenced procedure and almost everyone thinks that it is the one and only LOTO procedure, and they are flat out wrong. Subchapter J specifically states that it is not for electrical work. There is one LOTO procedure for utilization equipment which falls under Subchapter S (1910.3xx) and four more that are in Subchapter R section 1910.369. Construction has just two sentences over in Article 1926 but that one really probably isn't even all that adequate by OSHA's own standards. So focusing on your situation, is the equipment you are dealing with utilization equipment? Or is it "generation, transmission, and distribution" equipment? Second is it continuous duty and interacts with the utility line power or is it strictly portable or emergency backup power such as backup generator that operates only exclusive to utility power? Don't be afraid to get confused on the answer to this question because when you look at the "scope" section of NEC (NFPA 70), 70E, and NESC (IEEE C2) never mind OSHA it is clear that nobody else is very good at defining the scope of what you are dealing with either.
Now why am I making this distinction? For the simple reason that we've got to make sure that we are following the right set of rules!! The prohibition against energized work exists ONLY in Subchapter S which applies only to utilization equipment. It does not exist for distribution equipment (1910.269). And they have 4 different LOTO procedures so make sure you pick the right one.
This is an important distinction. If you are working on distribution equipment, then you should be following 1910.269, NOT Subchapter S. And if you read the scope in 70E carefully at the very beginning, you will also find that 70E does not apply either. That's not to say that you can't use it as a guide,just that there are differences between the two rule sets.
Read this standard letter of interpretation from OSHA:
https://www.osha.gov/laws-regs/standard ... 2006-12-19"Therefore, to qualify for the exception found in Note 2 of §1910.333(a)(1), the employer must, on a case-by-case basis, determine if the orderly shutdown of the related equipment (including the panel) and processes would introduce additional or increased hazards. If so, then the employer may perform the work using the electrical safe work practices found in §§1910.331-1910.335, including, but not limited to, insulated tools, shields, barrier, and personal protective equipment. If the orderly shutdown of the related equipment and processes would not introduce additional or increased hazards, but merely alter or interrupt production, then the de-energization of the equipment would be considered feasible, and the exception found in Note 2 of §1910.333(a)(1) would not apply."
This goes beyond the mere statement of looking at the panel itself in question and this is where the term "continuous industrial processes" comes into play. Does the orderly shutdown of the RELATED equipment and processes introduce additional or increased hazards and not merely alter or interrupt production? You can't just stop at the panel itself and that's where this term (and its misuse) come from. I have spent many a late night at hospitals due to working on equipment that affects operating rooms and far too many weekends at large manufacturing plants for this reason. Switchgear guys work by flashlight more than they do by sunlight! You have to expand beyond your immediate surroundings. Your statement, "safety critical load
at this time that cannot be turned off" does not meet this criteria.
However the prohibition against energized work comes from Subchapter S, NOT 1910.269 which has no such prohibition. It is recognized that distribution equipment is different. It is generally difficult to get things shut down in an orderly manner. It is meant to be worked on while energized. Work procedures have been developed specifically for this purpose. So if you consider a UPS to be distribution equipment, then you probably should be working under 1910.269, not Subchapter S. And that means that you should be using NESC more than 70E and NEC. But there are a few other differences as well so don't just take this one section and run with it.
Next regardless of which rule set you follow when you do an electrical LOTO you MUST test for absence of voltage. A case can be made for certain procedures such as visually verifying that a generator is shut off or that a cord has been disconnected but most of the time this means doing a voltage test. Equipment is always considered to be POTENTIALLY live until you prove (via a test) that it is dead. So that means that the test for absence of voltage is ALWAYS energized work. There is also personal protective grounding if it is needed and that is also ALWAYS energized work. A third bit of energized work is if you are applying cover up., which is what you are talking about doing. This web site shows some nice pictures of cover up illustrating it:
https://www.osha.gov/SLTC/etools/electr ... pment.htmlSo getting back to your questions. First off, forget about 70E when it comes to shock protection. No matter how hard they try, they just can't get it right. Cover up is a standard practice. Even the OSHA letter of interpretation basically mentions it. It has been stricken from 70E because some on the committee think that this is strictly a lineman thing and has no place in a utilization standard, and they would be dead wrong. So rather than bother with that I'd suggest studying IEEE 516 which is the standard that 70E and OSHA actually reference and use as the guidance for shock protection.
In terms of shock protection there are three considerations. The first one is whether or not you are protected by distance. The key criteria for qualified workers (qualified means they are trained to do energized work) is the minimum approach boundary. For some goofy reason NFPA 70E renamed this term to the "restricted approach boundary". Same thing. The second boundary applies to unqualified personnel. This boundary exists but is never named in OSHA 1910.269 and elsewhere. It is called the limited approach boundary in 70E. It is generally either 3'6" or 10' for the voltages you are referring to based on whether or not the conductors are basically fixed or they can swing (overhead lines). Since you said you are 2 feet away, we're actually done here. No need for cover up at all because you are never crossing the minimum approach distance. A further consideration is whether or not equipment is exposed which means it is not insulated, guarded, or inaccessible such as behind a door or panel. If it is not exposed, then the approach boundaries are ZERO (they do not exist). Either way, you're already outside of that area.
If we work within the minimum approach distance, we need insulation. So either we insulate the tools such as working with meters with insulated probes or hot sticks, or we use insulation on ourselves (rubber gloves with leather protectors), or we insulate the equipment using cover up. If it's the latter we get the gloves out to put it on then we can take them off because after that, nothing is exposed.
When switching over to arc flash the key consideration is whether or not we can accidentally create an arc. If there is exposed equipment and we bring conductive objects into the minimum approach boundary, then it is generally ASSUMED that an arc is possible by accidentally contacting the energized parts. But if nothing is exposed then we have to consider any other way that this might happen accidentally and if not, we don't need arc flash PPE. The first table in 70E-2015 or -2018 covers this situation, and alternatively there is a table in Annex A of 1910.269 that I consider far more readable and better written than the long, complicated, and confusing table in 70E. If there is nothing exposed and no way to accidentally create an arc then arc flash PPE is not needed. Otherwise, it is.
Don't get caught in thinking EXPOSED = arc and and shock hazard and not EXPOSED = no arc flash or shock hazard. By way of example inserting an MCC bucket into an energized MCC (not that I condone this practice) is certainly an arc flash hazard and there have been more than one documented case of injury from this practice. However there isn't a shock hazard when doing this because the bus is behind the bucket where it can hardly be considered exposed.