Preliminary Characterization of Respirable Rock Dust Generated from Cutting Potash in Laboratory Full-Scale Tests with Radial Picks at Different Stages of Wear

Airborne rock dust poses serious long-term health effects to workers in mining and tunneling underground rock environments. When inhaled, respirable crystalline silica particles commonly found in quartz and other minerals will scar sensitive lung tissue and cause irreversible lung diseases. Characteristics such as concentration, type of mineral, particle size, and particle shape can harm workers to various extents. Therefore, this study characterizes airborne rock dust particles that are released from mechanically cutting rock. Laboratory full scale linear cutting tests on samples of potash rock were performed with radial picks to generate dust and were collected with various instruments, including Dorr-Oliver cyclones. Three stages of pick wear were tested: new, moderately worn, and severely worn. Comparisons between different stages of pick wear to dust concentration, size distribution, and particle shape characteristics are drawn from this preliminary study using analytical methods, field-emission scanning electron microscope image capture techniques, and laser diffraction. Although further testing needs to be conducted to make viable and concrete conclusions, a review of the test results reveals a strong tendency in generated airborne and deposited dust to be linked to the bit tip wear, which was influenced by tip surface area geometry, such as a sharp tip, blunt tip, or undulating sharp tips. The moderately worn pick, or the pick with the bluntest tip, in these experiments released the highest concentration of dust. The moderately worn (bluntest) pick also generated particle shapes with the highest aspect ratio compared to the other two picks. Additionally, in terms of the particle size distributions, all the picks generated airborne particle size mean values between 0.7 and 1.2 µm in aerodynamic diameter. As for deposited particle size distributions, all the picks generated particles with the mode of particle aerodynamic diameter sizes at 13 µm. In the end, the results of this preliminary study paired with future testing can confirm and eventually provide the basis for optimum bit management and maintenance systems to control airborne dust exposures.