Arc flashes occurs as a result of a fault or short circuit condition that generates light and heat in the form of an electrical explosion. This may be a phase to phase fault or a phase to ground fault. Specific events that tend to cause arc flashes include the following:
The arc flash clothing required for various electrical equipment shall be determined by an arc flash risk assessment. The NFPA 70E allows for two methods of selecting PPE. The incident energy method is an engineering assessment utilizing the equations located in the IEEE 1584. The arc flash PPE category method utilizes Table 130.7(C)(15)(a). Please note that the arc flash PPE category method requires verification of available fault current and clearing times of overcurrent protective devices. The 2018 NFPA 70E addresses this in Article 130.5(F).
The Personal Protective Equipment (PPE) you will need depends on the Hazard/Risk Categories determined by the Arc Flash Hazard Analysis.
Based on the arc flash information provided by the engineering analysis, site specific level of PPE, per the NFPA 70E guideline, is determined for each applicable location. PPE requirements for workers can then be established once the incident energy is known for each panel location.
A. Protection of Electrical Workers
An arc flash event can occur while working on or near most energized equipment and can cause serious and significant injury to electrical workers – even death. According to the National Fire Protection Association:
• The majority of hospital admissions due to electrical accidents are from arc-flash burns, not from shocks
• Each year more than 2,000 people are admitted to burn centers with severe arc-flash burns
• Arc-flashes can and do kill at distances of 10 feet
The Arc Flash Hazard Analysis determines the extent of possible injury at the equipment and the appropriate personal protective equipment (PPE) to wear. In summary this analysis will provide:
• Flash Protection Boundary (FPB) for applicable electrical equipment
• The PPE that people shall use within the Flash Protection Boundary
B. Compliance with OSHA
Another reason is to ensure compliance with the Occupational Safety & Health Administration (OSHA) regulations pertaining to electrical safety. OSHA is currently the enforcement agency driving arc flash safety in the workplace. They have cited companies for not following their regulations and the guidelines provided in the National Fire Protection Association’s (NFPA) two consensus standards, the NFPA 70E: Standard for Electrical Safety in the Workplace and the NFPA 70: National Electrical Code® (NEC®).
In addition to citing specific OSHA regulations, OSHA will also cite the General Duty Clause for electrical citations.
C. General Duty Clause
Section 5(a)(1) states, “Each employer shall furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees.”
In a July 25, 2003 OSHA Standard Interpretation letter signed by Russell B. Swanson, Director, Directorate of Construction, it states, “With respect to the General Duty Clause, industry consensus standards may be evidence that a hazard is “recognized” and that there is a feasible means of correcting such a hazard.”
It further states that “Industry consensus standards, such as NFPA 70E, can be used by employers as guides to making the assessments and equipment selections required by the standard. Similarly, in OSHA enforcement actions, they can be used as evidence of whether the employer acted reasonably.
OSHA has often been referred to as the “Shall Do” part of this requirement. The NFPA 70E and the NEC® are often referred to as the “How To”, method to comply.
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