Increasing awareness that the electric arc flash hazard is uniquely different from the long recognized electric shock hazard is largely attributed to the evolution and publicity associated with NFPA70E, Standard for Electrical Safety in the Workplace. NFPA70E addresses administrative and personal protective equipment hazard control measures, but does not provide guidance in engineering control measures of elimination and substitution. In order to design a comprehensive arc flash hazards mitigation program, the safety professional must look beyond NFPA70E and consider guidance in safety management systems standards such as ANSI Z10, Occupational Health and Safety Management Systems.
This paper provides a roadmap for safety 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
The critical role of arc hazard assessments
Elements for sustainable performance
Measuring and monitoring quality and effectiveness.
Over the past 15 years, the evolution in regulations, codes and standards, as well as basic understanding of the arc hazard, has elevated the importance and priority of managing and mitigating this hazard in the workplace. This paper is intended to help safety professionals in managing this hazard through understanding and application of appropriate regulations and standards, implementing hazard assessments, evaluating mitigation options, reducing risks, and designing and implementing control measures to help assure an effective and sustainable program. It describes an approach that integrates the requirements for administrative controls and personal protective equipment in NFPA70E-2009 Standard for Electrical Safety in the Workplace with the proven safety management concepts and hazard control measures in ANSI Z10-2005, Safety and Occupational Safety Management Systems. This integration can help provide an effective and sustainable program to reduce or eliminate risk of injury from electric arcs.
The mitigation of electric arc flash hazards presents a difficult challenge for most safety professionals. The electric arc phenomenon is a complex hazard, and the mitigation standards and technology continue to evolve. Recognized standards offer different solutions, in particular with respect to the application of personal protective equipment. Some things are clear. OSHA regulations are very specific with regards to employers' responsibility to assess the workplace for hazards and enable employees to recognize and avoid these hazards, and implement mitigation and control measures to protect employees from these hazards. With regards to arc flash hazards, current language in OSHA regulations is not descriptive in arc hazard assessment and mitigation/control methods.
In an arc flash event, the incident energy, thermal energy transferred to a person's body, is measured in calories/cm2. Typical exposures in industrial and commercial power systems can range from 0 to well over 100 calories/cm2. Bare skin can suffer a 2nd degree burn when exposed to thermal energy of 1.2 calories/cm2 for one second duration.