An arc flash is a workplace hazard that may occur in an electrical installation whenever there is an insulation failure or short circuit. The arc generates a brilliant flash of light and ionized conductive plasma with temperatures in excess of 5000°C.
Arc flash hazards
An electric arc is a relatively rare but very dangerous condition. Personnel working on or near electrical equipment should take appropriate precautions and wear appropriately protective clothing.
Arc flash prevention (Workplace electrical safety)
Several workplace electrical safety consensus standards have been developed over the years to address this hazard.
NFPA 70E Standard for Electrical Safety in the Workplace, NFPA
NFPA 70E is the main electrical safety document for industrial applications and applies to work done by electricians, electrical technicians or plant staff that work on energized electrical equipment.
National Electrical Safety Code C2, IEEE (NESC)
The National Electrical Safety Code (NESC) is directed toward employees working in electric transmission, distribution or generation. This standard covers linemen and employees of electrical utilities.
Arc flash safety regulations (OSHA Standard 1910.269)
This regulation covers the operation and maintenance of electric power generation, control, transformation, transmission, and distribution lines and equipment.
The most recent OSHA revision has become a law as of July 10, 2014. The summary of most important changes is:
- All employers “shall make a reasonable estimate of the incident heat energy to which the employee would be exposed” by January 1, 2015.
- “Each employee who is exposed to hazards from flames or electric arcs must not wear clothing that could melt onto his or her skin or that could ignite and continue to burn when exposed to flames or the heat energy.” Compliance is required by October 31, 2014.
- Where electric arc hazards are present at an operating voltage above 600V and the incident energy estimate exceeds 2.0 cal/cm², “the outer layer of clothing worn by an employee must be flame resistant.”
- Where electric arc hazard is present, use “protective clothing and other protective equipment with an arc rating greater than or equal to the heat energy” whenever energy estimate exceeds 2.0 cal/cm². “This PPE shall cover the employee's entire body.”
Each of the above mentioned standards and regulations cover safe work practices and recommend using arc rated Personal Protective Equipment (PPE).
Standards for the certification of arc-rated clothing
Standard for Garments
- ASTM F1506, Standard Performance Specification for Flame Resistant Textile Materials for Wearing Apparel for Use by Electrical Workers Exposed to Momentary Electric Arc and Related Thermal Hazards
- ASTM F1891, Standard Specification for Arc and Flame Resistant Rainwear
Arc Rating Test Method
- ASTM F1959, Standard Test Method for Determining the Arc Rating of Materials for Clothing