Mike Darby
Darby Electric Co., Inc.
Anderson, South Carolina 
Management Services Committee Member

We should start with this: What exactly is an arc flash study?

An arc flash study must be conducted in order to comply with the National Fire Protection Association (NFPA) Standard 70E. Beginning with the fault current available from your utility service, the fault energy available at your various electrical cabinets is calculated based upon fuse and circuit breaker ratings, wire sizes, and lengths of the circuits. Labels are created and applied to the equipment to identify the hazard classification ratings. The hazard classification ratings determine what level of Personal Protective Equipment (PPE) is required in order to service the equipment. Requirements may vary from essentially nothing, to safety glasses with long sleeves, up to a complete “spacesuit” for proper protection. You can do it yourself if you are qualified, but there are some benefits to working with an experienced professional.

Once you have labeled the equipment and identified the hazard classification ratings, you should establish safety procedures regarding those markings, train all workers and document that training, and provide and keep the necessary PPE in good condition.

“Safety drives excellence”
Deep down in your heart you really care about your fellow employees and you do not want anyone to be injured. Arc flash injuries can maim and kill. SAFETY has to be our number one priority.

Problems with safety will lead to problems with insurance costs, followed shortly by problems with profitability. So, SAFETY affects the viability of your business in the future. Recently, I heard a particularly safety-conscious service center owner state that “Safety drives excellence.” He is definitely onto a really good philosophy. Working in a safe manner requires that you think about the job at hand and plan ahead to avoid problems. Isn’t that the essence of any well-run operation?

An extra measure of insurance
Think of an arc flash hazard analysis as a helpful means of planning ahead. It won’t be cheap, but the cost will be far less than the cost of a burn or electrocution injury. The avoided costs could be enormous, so you could also think of the study as an extra measure of insurance.

We recently hired a professional engineer to conduct a study in our service center. We collected the system data ourselves to save on engineering labor costs. In the process of collecting fuse ratings, wire sizes, and length of cabling, we found some unusual conditions that required correction. Here are some examples:

• a disconnect that had not been opened in so many years that it was no longer operable;
• temporary wiring that was too small to be protected by the upstream fuses;
• motor lead wire pulled inside a short conduit run - probably because it was “handy” at the time the extra outlet was needed.

If you have an older service center, a study will help you gain a better understanding of how your facility is wired and where you can shut off the power in the event of a problem. This will be particularly useful if you purchased a facility built by others and don’t have an “old hand” on your staff who knows the function of every disconnect in the shop. We found a power feed that jumped over to another building and then immediately returned “from whence it came.” It seemed confusing until we figured out that the utility feed had been moved in the mid 80’s from  a pole mounted service between two buildings to a pad mounted service that was farther away.

After calculating the hazard levels, our engineer was able to show us that changing two of our disconnects from standard “one-time” fuses to class RK1 fuses would reduce the arc flash hazard rating on 18 additional devices downstream. This alone was worth the cost of hiring him.

Shows a good faith effort
For those of us in the U.S., conformance with standard NFPA 70E will demonstrate that you have made a good faith effort to comply with OSHA requirements. While OSHA does not normally enforce consensus standards, our professional engineer stated that OSHA sometimes enforces them under the general duty clause.

The three following excerpts are from an arc-flash hazard interpretation letter on OSHA’s Web site (osha.gov):

[1]    A requirement to mark equipment with flash hazard warnings was not included in the 1981 Subpart S revision. However, paragraph (e) of §1910.303 requires employers to mark electrical equipment with descriptive markings, including the equipment's voltage, current, wattage, or other ratings as necessary. OSHA believes that this information, along with the training requirements for qualified persons, will provide employees the necessary information to protect themselves from arc-flash hazards.

[2]    A violation of the General Duty Clause, Section 5(a)(1) of the Act, exists if an employer has failed to furnish a workplace that is free from recognized hazards causing or likely to cause death or serious physical injury. The General Duty Clause is not used to enforce the provisions of consensus standards, although such standards are sometimes used as evidence of hazard recognition and the availability of feasible means of abatement.

[3]    Arc-flash hazards are also addressed in §1910.335(a)(1)(v), Safeguards for personal protection, which requires that personal protective Equipment (PPE) for the eyes and face be worn whenever there is danger of injury to the eyes or face from electric arcs or flashes or from flying objects resulting from an electrical explosion. In addition, paragraph (a)(2)(ii) of §1910.335 requires, in pertinent part, the use of protective shields, barriers, or insulating equipment "to protect each employee from shocks, burns, or other electrically related injuries while that employee is working . . . where dangerous electric heating or arcing might occur" (emphasis added). The §1910.335(a) (2)(ii) safeguard selected — shield, barrier, or insulating material — must fully protect employees from electric shock, the blast, and arc-flash burn hazards associated with the incident energy exposure for the specific task to be performed.

Conclusion
The boldface words above are underlined for extra attention.

The word “however” tells you that what was stated previously may not be the full story.

The word “fully” is a legal gotcha. It may require lots of expensive legal arguing to take place as “billable hours” before a definition can be agreed upon.

In order to fully protect anyone from the “incident energy exposure,” you are going to have to figure out exactly what the incident energy level is. If an OSHA inspector asks you how the incident energy exposure of a given piece of equipment was determined, an arc flash hazard study can provide you with the answer.

Categories: Safety

Tags: Safety Arc flash

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