Electrical arc flash and shock hazards have been recognized as particularly dangerous and fairly frequent occurrences that put the lives and health of electrical workers at significant risk. Statistics indicate that based on hospitalization records, 5-10 arc flash accidents that involve a fatality or serious injury to an employee occur every day in the United States.
Those incidents most often occur when personnel are required (or choose) to work on electrical equipment while it is in an electrically energized condition. In an effort to reduce these incidents, the National Fire Protection Association’s NFPA 70E® standard was published, and OSHA cites it as a definitive resource for employee electrical safety in the workplace.
NFPA 70E 2004 Article 130.1 (Justification for Work) is very clear that one of the fundamental requirements for safe electrical work practices in any facility is to place all equipment in an electrically safe work condition (i.e., lockout/tagout) before personnel works on or near the equipment, unless the circumstances meet certain conditions for exemption from that rule that are clearly outlined in NFPA 70E 2004 Article 130.1(A) (3). The arc flash and shock hazards are only present when electrical equipment is energized, and that includes the steps of performing the lockout/tagout process up to and including the point that the equipment has been verified to be in an electrically safe work condition, meaning it has been verified as not energized.
Arc flash accidents result in devastating consequences to the workers involved and their families and are also very costly to the employer and its insurers. The average cost of a single survived accident can easily reach $8-10 million in direct and indirect costs. Legal settlements almost always involve citations of deficiencies in the employer’s safety program as a causative factor leading to the accident.
A critical element of compliance with electrical safety standards requires building owners and management to complete a flash hazard analysis on the facility’s electrical distribution system (see NFPA 70E 2004 Article 130.3 Standard for Electrical Safety in the Workplace). These engineering studies are quite complex, and often require the services of outside engineering resources to complete properly and accurately.
A flash-hazard analysis comprises three different electrical system studies --
- a short circuit study,
- a protective device time-current coordination study,
- and finally, the flash-hazard analysis itself.
The analysis provides, among other things, a detailed assessment of the potential energy at each point in the system that would be released in the event of an arcing fault within the equipment. This potential arc flash energy must be calculated at each point in the system so that workers may be adequately protected, using properly rated personal protective equipment (PPE) whenever conditions require that work be performed on the electrical equipment while it is in an electrically energized condition. This potential incident energy is measured in calories per square centimeter or joules per square centimeter, which defines the flame-resistant (FR) protective level of the PPE that the worker must wear. (Illustrated, the minimum PPE requirements of NFPA 70E-2004 Hazard Risk Category 4 include protection like an Oberon Arc40™ coat, pants, and hood with hard cap. The worker is preparing to rack a Square D® Masterpact® circuit breaker from its cell. Photo copyright Oberon Company 2005.)
Tips for Success
Because these safety standards are very broadly implemented, there is a large demand in the market for qualified engineers who are competent in providing electrical system studies. This large market demand puts pressure on available resources, and as a result, many new companies have emerged to offer services to help meet the demand. These resources have widely ranging capabilities to perform this work properly.
The result of a poorly executed flash hazard analysis can in some respects be worse than none at all, since the output of the study will determine the appropriate level of PPE that a worker must use for protection. Incorrect values can suggest levels of PPE that will either overprotect or underprotect the worker, and that error may become the basis for increased safety risk exposure.
Thus, facility managers and procurement staff should fully understand how to properly qualify vendors with whom they may contract for flash hazard analysis. Why? Performing a flash hazard analysis is a complex task that requires considerable judgment and knowledge. This work should only be performed by a licensed professional electrical engineer who is familiar with electrical distribution system design, and the techniques of performing the complex calculations required. While some facilities may have staff engineers who are capable of performing this work, many do not. Facilities faced with the prospect of purchasing a flash-hazard analysis often do not fully understand the process itself as well as what differentiates a high-quality analysis from the rest.
Request a customer list: Facility managers should ensure that prospective vendors are adequately qualified to perform the work. Asking for a list of other customers that the vendor has provided similar work for, and samples of the final flash-hazard analyses, is crucial. The analyses should be professionally presented, with data in tabular format, and should include a list of prioritized recommendations for correcting such things as code violations, over-dutied equipment, and unacceptable incident energy conditions found during the analysis.
Include time-current coordination study: Making sure the vendor will include the time-current coordination study in the scope of the analysis is also key. Many vendors omit this step in an attempt to be more competitive price-wise. However, the information from the time coordination study is critical in order to determine strategies to reduce any high incident energy conditions that will be found.
Remedying high incident energy conditions: Prospective vendors should also be able to suggest ways to reduce high incident energy conditions that are found. Many techniques are available using engineering controls to retrofit the equipment in the system. Facility managers should query the prospective vendor on what options they can offer to lower unacceptable risk hazard levels.
Equipment labeling options: Another key consideration: For safety reasons, many companies are choosing to label equipment with the specific values determined in the flash-hazard analysis. The current standards do not require labeling the equipment with specific values, but it is a good practice for workplace safety. Asking the prospective vendor about options for labeling equipment with this information is important. Labeling should comply with the latest ANSI Z535.4 standards.
Electrical safety training: Finally, facility managers should confirm that the prospective vendor offers electrical safety training for plant maintenance workers, which is required for them to be considered “qualified persons” by NFPA 70E 2004 definition. While such training is not part of the arc flash hazard analysis, it is a critical requirement for compliance to the safety standards.
An arc flash analysis is crucial for personnel safety in an industrial manufacturing plant, so the choice of a vendor for arc hazard analyses should be undertaken as carefully and with the same due diligence as applied to any vendor.
Many well-qualified commercial resources are available to do this work, as well as some that are not capable of performing these system studies well. Since your choice will ultimately determine the future safety of your electrical workers, it must be approached carefully and with a thorough understanding of what the return on investment will be.