By Joseph DuCarme, mechanical engineer, NIOSH
Severe injuries and fatalities occur every year when a miner is struck or pinned by mobile mining equipment such as continuous mining machines, shuttle cars and scoops. The Mine Safety and Health Administration (MSHA) estimates that since 1984, 73 fatalities of this type have occurred that may have been prevented through the use of proximity detection technology. During 2013, MSHA plans to finalize a regulation that would require the use of proximity detection systems on continuous mining machines and to publish a proposed regulation related to proximity detection systems for underground coal haulage equipment.
The National Institute for Occupational Safety and Health (NIOSH) has been a leader in the development and testing of proximity detection technology since its introduction to the industry. Most recently, NIOSH researchers have developed the Intelligent Proximity Detection System, which is designed to provide intelligent protection by disabling only potentially hazardous machine motions. This system is built using off-the-shelf proximity detection hardware along with software developed by NIOSH researchers.
Signals from multiple magnetic field generators are measured by a wearable device on the miner’s belt. Based on the measured strength of these signals, a model of each of the magnetic shells is created and the position of the miner is determined as the intersection of these shells. The positions of all miners in the area are continuously tracked and compared to pre-defined safety zones around the machine. When a miner intrudes into one of these zones, the machine functions associated with that zone are disabled, but safe machine functions are allowed to continue. Laboratory evaluations have quantified the accuracy and robustness of the system with respect to environmental variables including the presence of metallic objects and coal near the mining machine as well as with respect to operational variables such as the posture of the miner.
In addition, human-subject testing has been used to investigate the incorporation of a visual warning system mounted on the mining machine as well as the impact of proximity detection on the ability of experienced continuous mining machine operators to perform simple machine operation tasks. The results of this research indicate that the Intelligent Proximity Detection System is capable of maintaining an accuracy near 1 foot with regard to the environmental and operational variables tested, that the incorporation of a visual warning system significantly improves the ability of people to identify when and why a proximity detection event has occurred, and finally that the Intelligent Proximity Detection System has significantly less impact on an experienced operator’s ability to perform mining tasks. These results will be presented along with an overview of all NIOSH research in proximity detection.
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