Many factors can create an environment conducive to an arc flash in high-voltage equipment. An arc flash occurs when an electric current follows a path through the air instead of through a conductor. Released convective, radiant, and mechanical energy can cause burns, damage hearing, hurl tools through the air, and release dangerous fumes. Arc flashes start and end in seconds, leaving little or no time to respond.
National and International Standards Address Arc Flash Safety
OSHA(standard 29CFR1910), the National Fire Protection Association (NFPA 70 and 70E) and the National Electric Code (NEC Article 110.16) ASTM International (ASTM F1506, ASTM F1959), and the International Electrotechnical Commission (IEC 61482-2, IEC 61482-1-1 Method A, and IEC 61482-1-1 Method B) address arc flash safety through standards.
Three European Standard Organizations (ESOs) approve and ratify European Standards (ENs) that apply to a wide array of technical operations. A European Standard automatically becomes the national standard for the 34 member countries. The EN407 rating for gloves lists six performance levels for protection against thermal hazards. High numbers on the performance level scale indicate the best test results.
ARC Flash Ratings Provide Valuable Information
An arc rating (AR) defines the insulating capability of the material against an arc flash and references the Arc Thermal Performance Value (ATVP) and the Energy Breakdown Threshold (EBT) of fibers. The ATPV rates the capability of woven fabric clothing to absorb maximum heat energy in calories per centimeter. The rating describes the ability of PPE to lessen 2nd-degree burn injuries. The EBT measures the capability of fabrics to resist breaking open when exposed to high thermal energy.
The NFPAuses a 0-4 scale based on the amount of energy delivered to a point at a specified distance from an arc flash to determine the Hazard Risk Category (HRC). Labels on arc-resistant FR garments show a tracking code, the manufacturer’s name, care instructions, the arc rating, the Hazard Risk Category and a statement that the clothing meets the ASTM 1506 standard.
Follow Arc-Flash Rules
Recognizing and avoiding arc flash hazards occurs by adhering to the standards. Follow these rules:
- Allow only qualified workers to install, examine, troubleshoot or repair equipment in an arc flash hazard area
- Wear arc-rated PPE
- Use insulated tools
- Install warning signs and barriers
- Establish and observing arc flash boundaries
- Shut the circuit down before maintenance and use standard lock-out/tag-out procedures.
Insulated tools protect workers repairing equipment near an arc flash hazard. The tools must meet arc insulation standards for specific voltage levels. Clearly visible permanent signs and labels warn qualified workers about the potential of an arc flash before they begin troubleshooting or maintaining the system.
Barriers separate adjacent areas from exposed live circuits, slow the progress of an arc through equipment, and prevent arcs from moving beyond the area. Flash protection boundaries establish the distance from the potential arc flash, the qualifications of workers within each boundary and PPE choices. OSHA provides equipment voltage information and charts that assist with setting the approach boundaries.
Shutting down equipment and verifying that all parts have powered down eliminates the possibility of arc flash. Along with shutting down the equipment, use grounding devices to eliminate the risk of induced or stored voltages. Standard lock-out/tag-out procedures warn other workers about energizing equipment while under maintenance.
Armor Guys Offers Arc-Rated Gloves
In the past, Flame Resistant (FR) jackets, pants, shirts, coveralls, jackets, boots, insulating gloves and other PPE stood as the gold standard for arc flash protection. However, because arc flash accidents can cause a broad range of injuries, the NFPA changed the specifications for arc-rated PPE. Although all arc-rated PPE is flame resistant, not all flame-resistant PPE is arc rated.
Arc-Rated (AR) flame resistant PPE resists ignition and protects against extreme heat. Protective gear for arc flash also includes eye and face protection and respiratory protection when working in potential arc flash areas.
Thick rubber insulated gloves continue to protect workers from arc flash hazards. Yet, many workers prefer gloves that provide dexterity and flexibility as well as insulating protection. Specific aramid-coated gloves provide the protection and dexterity needed for close work on systems that present an arc flash hazard.
For example, Armor Guys offers its arc-flash tested BASETEK02-051® and 02-052 gloves that have an ATPV level 4 rating with an ATPV that equals 51 Cal/cm2. The lightweight, flame-resistant gloves combine high tensile strength with excellent cut and abrasion resistance.