Hello all. I am writing a paper for a class, and have read through the usual safety procedures and practices to reduce arc flash.

I remember several years ago at a seminar held by Lewellyn I think it was, where they said something to the effect of the highest incidence of serious arc flash incidents occurred during the opening and closing of an electrical panel or enclosure.

Does anyone know where i could verify this information or get more details? BOL data is way to vague.

Secondly, it seems to me that to reduce the danger from this particular phenomena, if one must open a live panel, one should do so in a manner that keeps the metal door between themselves and the interior wiring / energy potentials. and walk around to view the inside only after the panel/door is opened.

Any comments on this? I understand this is not a procedure to be used in lieu of proper PPE and procedures, but as an augment.

Finally, does anyone have other ideas like this that would contribute to reducing exposure to arc flash incidents not immediately caused by persons working on live panels, but rather arc flashes that occur despite good practice?

Lots of questions, I know, but i want to explore some ideas that may not have been adopted yet.

Thank you all!

John Sandow

I think what Lewellyn is referring to is opening and closing disconnects and breakers. This is a mechanical operation done by a person standing in front of the device. Mechanical devices can fail (springs and levers breaking, bolts falling out, etc) can result in short circuits and arc flashes or one phase that fails to open. Large panel covers that aren't hinged can slip when being removed and short a bus. I read a study, can't remember where, that molded case breakers have a higher probability of exploding if the asymmetrical current imbalances are large enough and the breaker AIC rating is too low during the first several cycles when being close. Maybe someone can comment further on this.

I have a question that I would like to get other's input on. I am in charge of instituting our electrical safety program. Arc Flash Protection as I understand must be a part of it, and we are preparing for it. I have been asked if there is a deadline for getting the arc flash protection procedures integrated? For example, panels labeled, PPE available, FR clothing, etc.

I'm not sure what you mean by a deadline. OSHA's general duty clause requires you to protect employees against recognized hazards, and that includes arc flash. Standards have been available for several years and OSHA began issuing fines for arc flash back in 2006. Labels have been required by NEC standards (which is a regulatory requirement in all 50 states) since the 2002 version. We're now at 2012. It could be said that the deadline for implementation if anything was probably right around 2004-2005.

I am in charge of organizing and managing Arc Flash and electrical safety. My question is "If the equipment is not part of a major process or life support equipment, do you think it is intended for all other situations to be de-energized or shut down to do the work?" OR "If the equipment is not part of a major process or life support, do you think you can work the equipment energized if, ie.........the panel is an I-line and the "hot" area such as buss bar is protected by barriers but still has a potential for exposure if an accident like droping screw etc were to happen or the limited approach boundary within the same panel is outside the area of work. For instance......installing conduit and wire in an energized panel............Would you consider that to be hazardous and require shutdown or allowable for energized work permit?

The "continuous industrial process" term is frequently misunderstood. OSHA has released a letter of interpretation on this. The intent is that effectively it means that IF the equipment is attached to something ELSE which would form a greater hazard such as if you are working on a lighting panel that also contains the control power for a fire pump. If you deem the possibility of an out of control fire a greater hazard than working on the equipment live, then this would be considered a justifiable reason for doing the work while energized. Note that in recent years even hospitals have been retreating from this stance.



Depends on the task. There are other reasons. For example, you can't test for the presence of voltage in a panel if you kill power to it. Troubleshooting tasks (speiifically voltage measurement) have an automatic exemption for this reason.

The limited approach boundary by the way applies for keeping unqualified personnel out of the area. The restricted approach boundary is where the prohibited approach boundary plus an inadvertent movement adder comes into play. I am perfectly comfortable with writing up an EEWP to state that I'm doing work within the limited approach boundary but outside the restricted approach boundary. After erecting barriers, I have eliminated all potential hazards so I would create an exposure to a potential hazard (though a small one) even in the act of de-energizing the panel. So working between the limited and restricted approach boundaries is almost always an automatic justification by the greater hazard rule. This rule comes frequently into play when you have large industrial panels which contain open starters mixed with control wiring where one part of the panel may be de-energized and the rest is not, or the classic example of working in a starter bucket in an MCC where you are landing motor leads...the motor leads are outside the restricted approach boundary (on the line side of the disconnect or breaker) but well within the limited approach boundary.

I would not normally allow installing conduit and wire into a panel unless you can again control exposure. For example drilling into a panel especially blindly is exceedingly dangerous unless you can control where the metal shavings go (magnetic drills are great for this) and where the drill goes when it penetrates (problem avoided for instance with a step drill bit). Fishing wire blindly is again extremely hazardous. BUT I couldn't say that you can't EVER do this in EVERY situation. There are plenty where the job can be done safely with little or no risk. But there are plenty of jobs where there is an unacceptable level of risk. Lots of plants though don't like the idea of shutting down for any reason. Look for that letter of interpretation by OSHA. It is highly enlightening. They plainly state that merely causing a production interruption is NOT an acceptable justification.