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| A mobile crane working near power lines |
Background
During the 1990's, approximately 20% of all electrocutions in the mining industry resulted from high-reaching mobile equipment, such as cranes, dump trucks, and drill rigs, coming in contact with overhead power lines. In these accidents, 56% of the injured miners were unaware of the shock hazard and contacted both the equipment and ground simultaneously after a power line contact had occurred. An overhead power line contact alarm was developed to supplement existing proximity warning systems. While not designed to prevent all related injuries, a contact alarm can warn workers when a piece of mobile equipment becomes energized by a power line. Two manufacturers plan to supplement their proximity warning alarm systems with contact alarm technology.
Proximity warning systems, advertised as having the capability of alerting operators when they approach too close to a power line, have been commercially available for 30 years. Such systems have not found widespread acceptance due to perceived performance deficiencies and, in part, to a lack of regulatory requirements. The only known comprehensive study of power line proximity warning systems was published by the U.S. Bureau of Mines in 1982. It documented some serious performance limitations. Proximity warning system manufacturers claim to have substantially improved product performance since then. Recent OSHA efforts are underway to improve the 29CFR Crane and Derrick Standard. The proposed language allows the use of proximity warning alarm systems as a means of maintaining OSHA's (and MSHA's) required clearance distances from power lines, provided such systems are approved by a nationally recognized testing laboratory. To allow approval by a third-party testing laboratory, objective performance data must exist from which to develop a standard for use by such laboratories. NIOSH-sponsored work will provide technical data for such a national standard.
Potential Outcome
An American National Standards Institute (ANSI) standard that sets minimum performance and operational criteria for power line proximity alarms is anticipated by 2010. Building on past and current NIOSH power line proximity research, the standard will allow the use of power line proximity warning alarms to protect workers against accidental contact between power lines and high-reaching mobile equipment. The technology can also be applied to reduce power-line-related electrical injuries in the construction industry. Based on an estimated worldwide market of 45,000 proximity warning systems, the overall potential impact on the reduction of power line contact accidents is high.