Evaluation of Noise Controls for Longwall Cutting Drums

The National Institute for Occupational Safety and Health (NIOSH) conducted research to develop noise controls for longwall mining systems to reduce the noise exposure of the longwall operators. Previous research determined that the dominant sound radiating components on a longwall shearer are the two cutting drums used to extract coal. Therefore, NIOSH developed numerical models of these drums to predict their dynamic and acoustic response. Upon validation, these models were used to explore various noise control options including force isolation, increasing structural damping, and increasing the stiffness of the vanes. Analysis of the viability of these three options with an OEM determined that the most practical solution was the increase of stiffness by adding gussets and increasing the thickness on the outer most helical vane plates. The Boundary Element models of the drums predicted that these structural modifications would yield a 3 dB reduction in the overall radiated sound. Thus, a set of modified drums were built and tested at a collaborating mine. Results from this test show noise reduction across the entire frequency spectrum with overall noise reductions of around 3 dB. Therefore, these results show that modeling can be successfully used to develop noise controls in these applications.