Page 80 - Occupational Health & Safety, September 2019

ELECTRICAL SAFETY
Three Benefits of Using AR/FR Base Layers for Arc Flash Protection
Appropriate base layers for electrical workers are a useful element in an AR/FR garment system.
BY SCOTT FRANCIS
Arc-rated (AR), flame-resistant (FR) gar- ments are a vital part of any thermal hazard mitigation personal protective equipment (PPE) program, and within the electrical industry, is a mainstay for safety managers. Yet, the garments must be worn—and worn correctly—to achieve the highest level of protection against arc flashes. Daily wear garments, as opposed to task- based garments, are worn throughout the workday and can help alleviate some of the human error con- sequence concerns surrounding PPE. Keeping this in mind, it is helpful to utilize all resources when creat- ing a system that best protects your workers and pro- vides the greatest level of compliance and comfort in the process.
Appropriate base layers for electrical workers are a useful element in an AR/FR garment system. As a multi-functional garment, AR/FR base layers have a wide variety of both performance and protection ap- plications, making the base layers a versatile addition to your safety program. In this article, we will analyze three key benefits of arc-rated base layers.
Meet and Exceed Consensus Standards
A typical streetwear base layer is usually constructed from popular manmade fabrics like acetate, nylon, polypropylene or spandex. These fabrics underneath AR/FR fabrics pose a serious concern for those seek- ing arc flash protection. When exposed to the extreme temperatures of an arc flash, these types of fibers will melt and can severely damage the wearer’s skin. A key function of AR/FR fabrics is that they will not only self-extinguish when a thermal source, like a flame, is removed; they will also provide some insulation from the heat source to help reduce second- and third-de- gree body burns. These melting fibers jeopardize heat source insulation by transferring heat to the skin. The molten polymers stick to the skin, causing additional skin damage and longer recovery times.
To comply with the NFPA 70E consensus stan- dard, base layers worn with AR/FR garments may be made of natural fibers so long as they are used within a comprehensive system. These flammable but non- melting textiles must be covered by appropriate AR/ FR garments completely to prevent ignition. By considering an AR/FR base layer, you can meet the
NFPA 70E requirement and provide an added layer of flame resistant, arc rated protection.
Assist in Achieving Required Arc Ratings
AR/FR base layers can contribute to the arc rating of a complete AR/FR PPE system. Determining the total arc rating number for a clothing system can be accom- plished in one of two ways:
■ One AR/FR layer in a clothing system: If the outer layer of your AR/FR system has an arc rating greater than the incident energy, or meets the nec- essary PPE category arc rating criteria, your AR/FR system is appropriate for that task—with or without natural, non-melting fiber base layers.
Remember, the outermost layer of the system must be arc-rated and flame-resistant. Non-FR outer layers will likely ignite and continue to burn once the arc flash event is over, and an AR/FR base layer will be of little help as the flammable outer layer continues to burn.
■ Multiple AR/FR layers: If a combination of AR/FR layers is needed to achieve a higher level of arc flash protection, the arc rating for the complete layered clothing system needs to be tested via ASTM F-1959 in a qualified lab.
Contrary to belief, you cannot simply “add” the layers together to arrive at the combined arc rating. For example, an 8 cal/cm2 shirt and 12 cal/cm2 jacket does not necessarily translate to a 20 cal/cm2 total system arc rating. The arc thermal performance value (ATPV) or the Energy Breakopen Threshold (EBT), which are types of arc ratings, must be determined in accordance with the ASTM F-1959 test method. If your layered system has not been formally tested with this protocol, then the highest arc rating of the indi- vidual garment layers determines the total system arc rating according to NFPA 70E.
When looking to assess the total arc rating of an AR/FR system, you may be able to reference manu- facturer reports. ASTM F-1959 is a standardized fabric test method, and often either the fabric or gar- ment manufacturers can provide layered system test results to confirm the combined arc rating of mul- tiple AR/FR pieces. If the layered system in question has not yet been determined, then you can ask the manufacturer to perform the test at a qualified arc rating test laboratory.
76 Occupational Health & Safety | SEPTEMBER 2019
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