By Jack Smith
Safety lockout/tagout center.
The intention of NFPA 70E: Standards for Electrical Safety in the Workplace is to protect workers from electric shock and arc flash hazards. The current version is the 2009 Edition, which supersedes the 2004 Edition. The 2012 Edition will be released in September, 2011. As we look forward to that release, it’s worthwhile to refresh our understanding of the current standard. The scope of the changes from the 2004 Edition to the 2009 Edition is too extensive for this article. However, some of the most noteworthy are included here.
The 2009 Edition includes a subtle but significant change to the definition of arc flash. It says arc flash is “a dangerous condition associated with the possible release of energy caused by an electric arc.” Adding the word “possible,” to the standard recognizes the potential for the hazard and emphasizes that workers should be protected from it.
The 2009 Edition clarifies that NFPA 70E applies not just to installation or construction, but to any work around electricity. Other clarifications and additions include:
Article 130.7 covers PPE required when working near energized electrical conductors. The 2009 Edition differentiates arc rated PPE from fire resistant PPE. The 2012 Edition will replace the term “fire resistant” with the term “arc rated.” Arc-rated PPE must withstand the forces of an arc event. PPE must be arc-rated as well as fire resistant.
In the 2009 Edition, when the Hazard Risk Category (HRC) tables in Article 130.7 are used in lieu of an incident energy analysis, HRC 1 requires a face shield, long pants, and shirt. These must be flame resistant with a minimum arc-rating of 4 cal/cm². HRC 2* now allows either an arc-rated flash-suit hood or a face shield with a minimum arc rating of 8 cal/cm2 and balaclava. The 2012 Edition will eliminate the HRC 2* category.
Hair nets and beard nets must be arc rated as well as fire resistant and non-melting. Hearing protection is required for all categories as well. However, hearing protection must be inserts for HRC 1 through HRC 4 because ear muffs could melt.
Article 120 covers the requirements for establishing an electrically safe work condition. De-energizing electrical circuits removes shock, electrocution, and arc flash hazards from equipment/conductors to be inspected or repaired. However, Article 120 also includes the requirement to verify that these circuits have actually been de-energized by performing voltage checks and wearing PPE appropriate to the potential calculated incident energy level or HRC. Article 120 also requires a lockout/tagout procedure. The most significant change to this part of the 2009 Edition is the addition of three requirements that address complex lockout/tagout:
Annex G provides a sample lockout/tagout procedure.
Energized Work Permit
The Energized Electrical Work Permit provides a means for electrical workers to assess work to be performed and the potential hazards involved with completing the intended tasks so they can protect themselves. While previous versions of NFPA 70E have been somewhat unclear on how employers and employees should comply, the 2009 Edition includes additional guidance on developing a work permit program. A flow chart has been added to the 2009 Edition to accompany the sample work permit in Annex J.
The 2009 Edition allows visual inspections without having to complete a work permit as long as the Restricted Approach Boundary is not crossed. De-energizing circuits that operate at less than 50 V is not required. Consequently, neither is a work permit.
As long as the appropriate safe work practices and PPE are used, a work permit is not required when “qualified” persons perform tasks such as voltage measurement, testing, and troubleshooting within the Limited Approach Boundary. The change allows “unqualified” employees to perform visual inspections and thermal imaging tasks as long as they are accompanied by a “qualified” employee.
This doesn’t mean that only electrical workers have competence or that thermographers or inspectors do not. Within the context of electrical safety, however, three important standards define “qualified electrical worker.” The National Electrical Code (NEC) (NFPA 70), OSHA standard 1910, and the 2009 Edition of NFPA 70E delineate the differences between qualified and unqualified workers.
Essentially, a qualified worker is one who has skills and knowledge related to the construction and operation of the electrical equipment and installations, and has received safety training to recognize and avoid the standards involved. The keys here are skill, knowledge, and safety training. Determining worker qualification has more to do with the task than it does with the individual. Workers may be qualified to do some tasks but unqualified to do others.
NFPA 70E defines the approach and protection boundaries applicable to electrical safety near energized equipment. Defining worker qualification is very important when discussing these approach and protection boundaries. Although the NFPA 70E approach and protection boundary definitions are not repeated in this article, their brief descriptions follow:
Flash Protection Boundary - is an imaginary limit at a distance from energized components within which a person could receive a second-degree burn if an arc flash occurs. Workers must wear appropriate PPE while within this boundary. The Flash Protection Boundary must be calculated for the specific application for systems that operate at potentials higher than 600 V. The default boundary for systems that operate at 600 V or less is 4.0 feet.
Limited Approach Boundary - is an approach limit at a distance from energized components within which a shock hazard exists. Unqualified persons must be advised of possible hazards and must be escorted. NFPA 70E previously called this boundary “working near.”
Restricted Approach Boundary - is an approach limit at a distance from energized components within which there is an increased risk of shock for personnel due to electrical arc-over and inadvertent movement. Appropriate PPE must be worn. Unqualified workers are not allowed.
Prohibited Approach Boundary - is an approach limit at a distance from energized components within which work is considered the same as coming in contact with the energized components. It’s also considered a shock protection-type boundary and must not be crossed without the appropriate PPE and written authorization in the form of a signed Energized Electrical Work Permit. Safe work practices must be followed by qualified workers.
No one has ever been shocked or electrocuted by coming into contact with components and circuits that are completely de-energized. No one has been exposed to hazardous arc energy by coming into contact with de-energized circuits. No power, no risk. However, until you have verified that circuits have been de-energized, use safe work practices, appropriate PPE, insulated tools, the right measurement tools with the correct Category rating, and above all, common sense.
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