An arc occurs when flowing current leaves its intended conductor, traveling through air to another conductor or to the ground. The resulting flashover can cause fire, damage to property, severe burns, and even death to individuals within close proximity. Circumstances that can create arc occurrences include electrical equipment malfunction and failure (spontaneous arc) and failure to take proper precautions when working on energized circuits (inadvertent arc). Accordingly, fall protection equipment for affected workers must reflect specific needs.
OSHA 29 CFR 1910.269, Electric Power Generation, Transmission, and Distribution Final Rule is a recently released update of a 40-year-old standard, and all requirements are now in effect. This standard intends to reduce the number of injuries and falls from heights related to arc flash exposure within the electric utility industry and other facilities that are subject to similar potential hazards. Significant changes within these new requirements include up-to-date fall protection and positioning requirements for tower and other structural climbing, as well as elimination of an exception for free-climbing hazards.
Certain aspects concerning fall protection PPE of non-regulatory ASTM (American Society for Testing and Materials) F887-11 Standard for Personal Climbing Equipment have been employed in creating this final rule. Arc flash (AF) rated designation for PPE requires that products resist high heat and maintain necessary structural integrity. Brief, relevant sections of the final rule are quoted here directly and are italicized within; please visit www.osha.gov/dsg/power_generation/ to review OSHA CFR 1910.269 in full.
Electrical Arc Hazard Protection: OSHA 1910.269(L)(8)
Employers are now required to assess their workplaces to determine those workers who are exposed to electrical arc hazards. In addition, the standard now provides requirements for arc flash-rated fall protection equipment. Equipment rated as such is not, however, intended to prevent all injuries, but is intended to mitigate the impact of arc flash, should one occur.
A common example of a potential arc hazard exposure concerns bucket truck workers in close proximity to power lines. Exposure may potentially result in burn injuries to workers due to melted webbing and compromised fall arrest capability, unless the equipment can withstand arc flash.
• Employers must estimate incident heat energy of arc hazards to which workers would be exposed, and must provide those workers with protective clothing and other protective equipment with an arc rating greater than or equal to the estimated heat energy.
• Employers must ensure that employees who are exposed to electric arc hazards do not wear clothing that can melt onto skin or ignite and continue to burn when exposed to arc flash.
Controlled Product Testing: ASTM F887
In order for fall protection to be ASTM F887-certified, the harness or lanyard must self-extinguish within five seconds after being subjected to an arc flash of 40 cal/cm2 and cannot melt or drip. Webbing must have 7,000-lb. tensile strength. ASTM F887 outlines performance requirements of personal protective equipment for arc flash resistance. Arc flash ratings assigned to PPE reflect at least minimum arc resistance performance criteria. Testing parameters must consider arc exposure, heat transmission variability and convective and radiant energy.
Fall arrest equipment must pass a drop test after arc exposure with heat energy of 40±5 cal/cm2, if workers using the equipment are exposed to electrical arc hazards. The harness must maintain its integrity after undergoing the ANSI Z359 dynamic drop test using a 282 lb. test torso.
Arc flash-rated eye/face protection products such as faceshields, safety spectacles and goggles are subject to ASTM F2178-2008 testing methods involving generation of heat flux values from 84 to 25 120 kW/m2 [2 to 600 cal/cm2s]. Arc flash-rated (AF) products are designed to resist heat from an electrical arc flash.
Minimum Approach Distances: OSHA 1910.269(L)(3)
To help safeguard unprotected workers from hazardous close proximity to energized lines and equipment, the standard provides newly updated determination methods. Concerning voltages higher than 72.5 kilovolts, employers must determine maximum anticipated per-unit transient overvoltage, phase to ground, through an engineering analysis, or assume maximum anticipated per-unit transient overvoltage, phase-to-ground, in accordance with Table R-9 or Table V-8, [of the standard] respectively.
Conductivity, a separate safety concern from that of arc flash protection, is worth mentioning as the concept can cause confusion for users of arc flash fall protection equipment. Arc flash products are designed to resist high heat and energy; conductivity concerns a product’s ability to conduct electricity. Typically, methods used to reduce personal protective equipment conductivity involve PVC-coated hardware designed to insulate metal hardware away from workers. However, this practice may not eliminate all risk; OSHA and ASTM F887 do not address electrical conductivity of fall protection equipment as no formal test method exists. Exposed metal components such as D-rings and buckles used on arc flash fall arrest equipment are still commonly used.
Approach distance requirements from energized lines and equipment for unprotected workers have been revised in the final rule. Mechanical equipment must be insulated for voltages involved, and positioned so that uninsulated portions cannot approach lines or equipment any closer than minimum approach distances specified in the standard.
Solutions are available for those who work on utility job sites and within industrial and other facilities where arc flash-related potential hazards may exist. Arc flash-rated head, eye, face and fall protection products are the smartest course of action and in many cases are now required for employees who are determined to be at risk.
Sources and Resources
• OSHA CFR 1910.269: www.osha.gov/dsg/power_generation/
• Understanding Arc Flash, Workplace Safety Awareness Council
•Department of Health & Human Services, Arc Flash Awareness, NIOSH Publication No. 2007–116D
• OSHA 1910.269 Appendix E – Protection from Flames and Electric Arcs for guidance as to estimating available heat energy.
• Training Requirements in OSHA Standards and Training Guidelines, Voluntary Training Guidelines, Section III.