OCCUPATIONAL SAFETY AND HEALTH

Occupational safety and health

Occupational safety and health

Implementing an Arc Flash Management Plan

Mitigating electric arc flash hazards presents a difficult challenge to most SH&E professionals. Electric arcs are a complex hazard, and the mitigation standards and technology continue to evolve. Recognized standards offer different solutions, particularly with respect to the application of PPE. Some things are clear. OSHA regulations are specific with regard to employers' responsibility to assess the workplace for hazards and enable employees to recognize and avoid these hazards, and to implement controls to protect employees from these hazards. However, current language in OSHA regulations is not descriptive with regard to arc hazard assessment and mitigation /control.

In an arc flash event, the incident energy (thermal energy transferred to a person's body) is measured in calories/ cm^sup 2^. Typical exposures in industrial and commercial power systems can range from 0 to well above 100 calories/ cm^sup 2^. Bare skin can suffer a second-degree burn when exposed to thermal energy of 1.2 calories/ cm^sup 2^ for 1 second duration (NFPA 70E-2009). Depending on total skin area burned and the underlying health of the injured, even seconddegree burns can be fatal.

Flammable clothing typically can ignite or melt if exposed to thermal energy greater than 4.5 calories/cm^sup 2^. Clothing ignition or molten synthetic materials on the skin can cause even more serious injuries than the direct exposure to bare skin since the duration of the burning or melting is many times longer than the arcevent itself.

The goal of arc flash hazard mitigation is to prevent exposures greater than these values, and to protect against injury in those situations where the hazard cannot be reduced to these levels. Currently, NFPA 7OE provides the most comprehensive guidance for general industry to accomplish OSHA objectives relative to electrical hazards.

In support of the requirements in NFPA 7OE, Institute of Electrical and Electronics Engineers (IEEE) Standard 1584, Guide for Performing Arc Flash Hazard Calculations, provides the technical basis and methods for analyzing electric power systems and quantifying thermal hazards from electric arcs. However, direct use of the standard requires a high degree of knowledge in power systems engineering. Although several arc hazard analysis software programs can make this task easier, using them does not eliminate the need for the user to be knowledgeable in power system design.

Analysis of the key points in the article

This article provides a road map for SH&E professionals to aid planning, design and implementation of a comprehensive and effective arc flash hazards mitigation program, from initial assessment to program audit. It addresses essential elements of planning and continuous improvement including:

interim measures to help protect workers while designing a permanent program;

relevant standards to consider when designing the program;

critical role of arc hazard assessments;

elements for sustainable performance;

measuring and monitoring the program's overall quality and effectiveness.

As with any workplace hazard, a mitigation program can range from minimum compliance to one based on continuous improvement, utilizing state-of the-art technology and methods. While NFPA 7OE provides several options, especially with regard to the application of ...