An Electical Arc-Flash Hazard Analysis Primer: Reducing Arc-Flash Hazard Exposures Through Engineering Controls

Abstract

The problem of electrical workers being injured or killed by electrical arcs and blasts is one of the most significant safety issues in the industry today. Accident data reveals that over 2,000 people are severely burned annually by electrical arc blasts on the job (1) and many others receive less severe burns that still result in significant pain and suffering to the victim. The purpose of this presentation is to provide an overview of the arc-flash hazard analysis (AFHA) process and general guidance for those organizations wishing to integrate AFHA into their overall electrical safety program. The electric utility industry was the first non-academic group to study arc-flash hazards (AFH) when they noted that electrical workers often received the most severe burns from their clothing igniting and continuing to burn long after the initiating arc had extinguished. In particular, man-made fibers such as polyester, nylon, and rayon were known to melt and stick to the worker’s skin following an AF, and this resulted in burns many times worse than had the injured worker been wearing no clothing at all (2). Subsequent studies were performed by private organizations and they impacted both the engineering and safe work practices associated with industrial plant operations. The primary standards or studies included: • IEEE 1584 Guide for Performing Arc-Flash Hazard Calculations • NFPA 70E Standard for Electrical Safety in the Workplace • OSHA 29 CFR 1910.269: Electrical Power Generation, Transmission, and Distribution Standard Of these documents, the IEEE 1584 Guide was most influential to engineers because it provided formulas for calculating incident energy levels, arc-flash protection boundaries, and a host of other important variables necessary to evaluate AFH in the work place. The term ‘incident energy’ refers to the amount of heat concentrated per unit-area of the skin. Incident energy is measured in calories per square centimeter (cal/cm2) of skin surface area. For reference, a value of 1.2 cal/cm2 will result in a second-degree burn of human skin (3). The principal reason why AFHA is necessary is that studies revealed that electrical arcs are somewhat unpredictable events (4), and there were many cases where seemingly innocuous energy sources (small transformers) produced incident energy levels that far exceeded the limitations of flame resistant (FR) clothing or other forms of personal protective equipment. It became obvious that the best method for protecting employees from AFH would be to evaluate the hazard level and then mitigate it through the use of engineering controls. Paper published with permission.