Arc Flash & Flame Resistant Clothing
NFPA 70E is the primary standard for electrical safety in the workplace. Published by the National Fire Protection Association, it serves as the authority in the U.S. on fire, electricity and building safety. The purpose of the standard is to provide a “practical safeguarding of employees during activities such as the installation, operation, maintenance, and demolition of electric conductors, electric equipment, signaling and communications conductors.” The U.S. Occupational Safety and Health Administration (OSHA) recognizes NFPA 70E as a generally accepted industry practice – often referencing it in citations. NFPA 70E does not have the power of a law, but is a voluntary consensus standard.
WHO IS COVERED BY NFPA 70E?
Electrical workers in all industries who work on or near energized parts or equipment that are capable of generating an arc flash. Examples would be electrical maintenance workers, machine operators and industrial electricians. Typical equipment would include high-voltage switching and grounding gear, panel boards, switchboards, motor control centers and starters, and transformers.
ROLE OF FRC (FLAME RESISTANT CLOTHING) IN MEETING NFPA 70E
NFPA 70E requires employers to conduct an arc flash hazard analysis to identify a worker’s potential exposure to arc-flash energy. The results of the analysis are then used to determining safe work practices, arc flash protection boundaries, and the appropriate level of personal protective equipment. Flame resistant clothing may be indicated.
For safe working practices, all equipment must be de-energized before being worked on unless the employer can demonstrate that de-energizing introduces hazards or creates problems due to equipment design or operational limitations. If de-energizing the equipment is impractical, the employer must establish a “flash protection boundary”. This is the minimum distance from an arc source where a person could receive a second-degree burn if an arc flash occurred. If the employee must perform electrical work within the flash protection boundary, the standard calls for wearing protective clothing as one measure of safety.
NFPA’S GUIDANCE ON DETERMINING RISK:
Perform an Incident Energy Analysis to determine the potential incident energy exposure of the worker. With the results of this analysis, the employer will select arc-rated flame-resistant clothing with an Arc Thermal Performance Value (ATPV), higher than the risk level. NFPA has established a table of common electrical job tasks, and a hazard category for each of these tasks. These are referred to as Hazard Risk Categories (HRC). The ATPV is a rating assigned to flame-resistant clothing noting the level of protection provided. The ATPV is expressed in calories per cm2 and represents the thermal exposure from an electric arc that will create a second-degree burn in human tissue.
PROTECTIVE CLOTHING CHART
|Hazard/Risk Category (HRC)||Required Minimum Arc Rating of PPE|
Published by the Institute of Electrical and Electronics Engineers (IEEE), The National Electrical Safety Code (NESC) offers guidance for workers during the installation, operation, or maintenance of electric supply and communication lines and associated equipment. The NESC, published by the Institute of Electrical and Electronic Engineers (IEEE) sets the minimum standards for safe working conditions. Although not a federal law (some states do make the NESC law), NESC is a voluntary consensus standard. However, some states have added these requirements, further increasing its application. OSHA cites the NESC in their utility industry comments. Arc-rated, flame resistant clothing was added as a safety requirement in the 2007 revision. The 2012 edition further updated this section. Arc-rated clothing was added for lower voltages. Tables denoting apparel requirements from 4 cal/cm² through 60 cal/cm² were included for the first time.
Who is covered by NESC?
NESC was formulated for the electrical utility industry and “covers the electric supply conductors and equipment, (including) electric supply stations, that are accessible only to qualified personnel.” NESC applies to all electric utility work performed at all public and private utilities, electric co-ops and municipalities.
Role of FRC (Flame Resistant Clothing) in meeting NESC
The NESC Rule 410A3 mandates the use of flame-resistant, arc-rated clothing for some tasks in the electrical utilities, and provides further guidance for implementation. A competent person will need to evaluate and assure compliance to the regulations. An assessment must be performed for potential exposure to an electric arc for employees who work on or near energized parts or equipment. In 2012, the rule added low voltage equipment to the >1000V equipment requirement from the earlier 2007 mandate. If the assessment indicates exposure greater than 2 cal/cm² exists, the worker is required to wear clothing or a clothing system that has an effective arc rating at least equal to the anticipated level of arc energy. Acetate, nylon, polyester, or polypropylene (unless arc rated in a blend) should not be worn when exposed to an electric arc or flame.
Tables 410 (1 – 3) illustrate the clothing to be worn and the effective arc ratings. These tables can be used in conjunction with an arc hazard analysis.
An exception is offered if the clothing creates additional (and greater) hazards than the potential exposure to the electric arc. In this instance, the clothing with an ATPV less than that required in the ruling can be selected. These exceptions require documentation, and are for unusual, and uncommon field requirements.
The U.S. Occupational Safety and Health Administration’s (OSHA) 29 CFR 1910.269 covers the operation and maintenance of electric power generation, control, transformation, transmission and distribution lines and equipment. Part (l) (6) (iii) states: “The employer shall ensure that each employee who is exposed to the hazards of flames or electric arc does not wear clothing that, when exposed to flames or electric arcs, could increase the extent of the injury that would be sustained by the employee”. This is the only current OSHA notation – and is brief in its statements. OSHA is re-working these segments, and is presumed to implement regulations similar to the NFPA 70E and NESC standards.