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Arc flash

Arc flash label changes

What does the 2012 edition of the NFPA 70E standard require for arc flash labels?

January 1, 2012

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Responding is Danielle Zyvert, product specialist, Brady, Milwaukee, WI.

The 2012 edition of the NFPA 70E standard includes several new requirements for arc flash warning labels. Before you review your labels, do not forget to first conduct an arc flash hazard analysis. This analysis will help you determine the arc flash boundary for operating systems, the incident energy at the working distance and the personal protective equipment necessary for applications within the arc flash boundary.

After you have completed this analysis, it is time to review your labels and make sure they are up to date on the new labeling requirements outlined in the 2012 edition of NFPA 70E. (Note: Labels applied prior to Sept. 30, 2011, are acceptable if they contain the available incident energy or required level of PPE.) According to Article 130.5(C), all electrical equipment – including switchboards, panel boards, industrial control panels, and other units that require examination, adjustment, servicing or maintenance while energized – must be marked with a label.

Among the new labeling requirements:

1. Arc flash labels must include at least one of the following:

  • Available incident energy and the corresponding working distance. Incident energy is the amount of energy impressed on a surface, a certain distance away from the source that is generated during an electrical arc event.
  • Minimum arc rating of clothing. Arc-rated clothing indicates it has been tested for exposure to an electrical arc. This was formally expressed as flame resistant in previous NFPA editions.
  • Required level of PPE. Arc rating of PPE should correspond with the appropriate hazard level and incident energy present.
  • Highest hazard/risk category for the equipment. HRCs range from 0 to 4 and help indicate arc rating and appropriate PPE and clothing.

2. Nominal system voltage: This is the voltage assigned to a circuit or system for the purpose of conveniently designating its voltage class (i.e., a 12-volt battery, 24-volt system or a 480-volt electrical panel).

3. Arc flash boundary: The arc flash boundary identifies systems of 50 volts or greater where the distance at which the incident energy level equals 1.2 cal/cm2. This must be identified on a label because this incident energy distance can result in a second-degree burn if skin is unprotected.

In addition, arc flash labels can identify other important boundaries, including:

  • Limited approach boundary – Identifies the distance from the exposed energized electrical conductor or circuit part in which a shock hazard exists
  • Prohibited approach boundary – Identifies the distance from the exposed energized electrical conductor or circuit part in which work is considered the same as making contact with the electrical conductor or circuit part
  • Restricted approach boundary – Identifies the distance from the exposed energized electrical conductor or circuit part in which an increased risk of shock exists due to electrical arc-over combined with inadvertent movement for personnel working in close proximity

Editor’s Note: This article represents the independent views of the author and should not be construed as National Safety Council endorsements.

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