Mining Publication: Improved Seat Reduces Jarring/Jolting for Operators of Low-Coal Shuttle Cars

Nearly one-third of the equipment operators in underground coal mines experience adverse levels of exposure to whole-body vibration (WBV). Shuttle cars are major sources of WBV exposure, with operators being exposed to WBV and shock when the shuttle car travels over rough mine floors characterized by numerous bumps, ruts and potholes. In low coal mines, seat suspension systems are difficult to design because of space restrictions. The seriousness of prolonged exposure to WBV and shock is demonstrated by their connection to cumulative back, neck and abdominal disorders. For underground-equipment operators in New South Wales, Australia, the number of back injuries caused by vehicle jarring is equal to the number of back injuries caused by overexertion. Moreover, a review of the shuttle-car injuries recorded in the Mine Safety and Health Administration's (MSHA's) database for 1997 is revealing. Of the injuries pertaining to the back, neck and head, 57 of 100 resulted directly from the jarring of the seated operator while driving the vehicle. This number translates to 25% of the total shuttle-car injuries in 1997 that were related to jolting/jarring of the operator. With input from underground shuttle-car operators, this study addressed a component of WBV that is germane to underground mining: high-energy impacts or shocks. Shuttle-car operators complained largely about the jolting and jarring they experienced when traveling over rough bottom. Thus, the research focused on a means for better isolating the shuttle-car operator from the jolts and jars caused largely by the high-level, low-frequency, terrain-induced impacts. The approach was to develop an improved seat that incorporated more ergonomic design features and that would use viscoelastic foam padding as the principal way of isolating the shuttle-car operator from shock impacts.