Development of noise controls for longwall shearer cutting drums

Abstract

Noise-induced hearing loss is the second most pervasive disease in the mining industry. The exposure of miners to noise levels above the permissible exposure level results in hearing loss of approximately 80% of coal miners by retirement age. In addition, between 2002 and 2011, approximately 48% of longwall shearer operators were overexposed in coal mines in the United States. Previous research identified the two rotating cutting drums used by the longwall shearer to extract coal as the most significant sound-radiating components. In this context, the National Institute for Occupational Safety and Health conducted research to develop noise controls for longwall mining systems. To this end, structural and acoustic numerical models of a single cutting drum were developed to assess its dynamic and acoustic response, respectively. Once validated, these models were used to explore various noise control concepts including force isolation, varying structural damping and varying component stiffness. Upon multiple simulations, it was determined that structural modifications to increase the stiffness of the outer vane plates were the most practical and durable approach to reduce the sound radiated by the cutting drums. Furthermore, these modifications did not adversely affect the cutting performance, nor the loading ability of the drums. As a result, these structural modifications were implemented into an actual set of drums for evaluation purposes. Results from the underground evaluation, when the modified cutting drums were used under normal operation conditions, showed noise reduction across the entire frequency spectrum with an overall noise reduction of 3 dB in the sound pressure level at the operator location, confirming the validity of the developed noise controls.

Noise exposure assessment of non-coal mining workers in four provinces of China

“…The prediction results of the ISO 1999:2013 model were consistent with the development law of hearing loss. These jobs (excavation worker, mill operator, and crusher operator) were likely to have a high incidence of occupational hearing loss, which was consistent with the high noise exposure positions identified in other studies ( 20 , 21 ).…”

Prevalence of hearing loss among noise‐exposed workers within the Mining and Oil and Gas Extraction sectors, 2006‐2015

“…In addition to regulatory measures, successful noise‐reducing equipment and methods have been developed/identified within Mining. Engineering controls, such as modified tail sections of continuous mining machines, noise control packages for vibrating screens, applying noise barriers and absorptive treatments within talc processing plants, drill bit isolators for roof bolting machines, structural modifications to cutting drums of longwall shearers, and noise control packages for vibrating screens, have shown to decrease noise emitted by equipment, while also maintaining durability. A 2009 study found that new‐style haul truck cabs used in limestone mines were significantly quieter (65.1 dBA) than old‐style (84.8 dBA) and retro‐fitted cabs (84.9 dBA) with the windows closed .…”

“…Recently developed engineering controls have shown great promise in reducing equipment noise within mining . Incorporation and continued development of these technologies, both in Mining and OGE, is critical for reducing worker exposures, in addition to employing effective administrative controls.…”

Ecological Characteristics and Occupational Health Effects of Deep Mines in China: A Review

“…Among the main ecological hazards in mines, the impact of noise on occupational health is the secondmost important hazard after dust [27]. If miners are exposed to 85 dBA of high-intensity noise for long periods of time without protective equipment, they may lose their hearing and cause permanent occupational deafness [28].…”