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Comparison of respirable dust characteristics from full-scale cutting tests with conical picks at three stages of wear
Slouka, Syd
Slouka, Syd
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2023
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Abstract
In environments where mechanical excavation systems break rock, airborne rock dust is generated and could pose respiratory health threats to workers. These environments include mining and civil applications with roadheaders, continuous miners, or similar machines used in underground operations. Therefore, this study aims to compare the characteristics of rock dust generated by conical pick cutters at various wear conditions. With supplemental experiments, the results can aid future evaluations of proper bit management, dust suppression, and control systems.
The work conducted under this study included full-scale laboratory cutting of concrete, limestone, and sandstone samples. Three symmetrically worn conical picks cut each sample at a new, moderately worn, and fully worn stage of wear. Equipment collected airborne dust samples and fines during and after cutting for qualitative and quantitative characteristics. Analysis of collected dust revealed the dust's characteristics, including the concentrations, silica contents, particle size distributions, and particle shapes.
Findings indicated that the dust generated in the cutting process increases as the pick tip wears. With a superimposed circle at the pick tip, further analyses show that as the tip radius increased by one millimeter during excavation, the dust generation at the pick increased by an average of 50 mg/m3 for all the samples. Furthermore, analysis of the cutting forces and specific energy of cutting (the amount of energy used to excavate a unit volume of rock) show that as the pick radius (mm) increases, the concentration (mg/m3) of dust per specific energy (kW-hr/m3) increases linearly. The correlation between dust and specific energy showed an average increase of 3.0 [(mg/m3) / (kW-hr/m3)] / mm of tip radiusin the rock samples tested. In terms of silica, the silica content is a function of mineralogy, and all the rock types contained traces of quartz.
The airborne respirable particle size distributions insignificantly shifted between pick wear. The fines size distributions slightly increased as the pick wear level increased. However, the differences are also deemed insignificant and, therefore, are negligible. Finally, the pick wear does not influence change in the particle shapes. All the picks consistently generated suspended respirable particles with similar particle shapes that are slightly oval with mostly smooth edges.
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