Platinum Mine Workers’ Exposure to Dust Particles Emitted at Mine Waste Rock Crusher Plants in Limpopo, South Africa

The South African mining industry is one of the largest producers of platinum (Pt) in the world. Workers in this industry are exposed to significant amounts of dust, and this dust consists of particles sizes that can penetrate deep inside the respiratory region. A cross-sectional study was conducted to evaluate dust exposure risk at two Pt mine waste rock crusher plants (Facility A and B) in Limpopo, South Africa. Workers’ demographic and occupational information was collected through a structured questionnaire, a walk-through observation on facilities’ processes, and static dust sampling for the collection of inhalable and respirable dust particles using the National Institute for Occupational Safety and Health (NIOH) 7602 and the Methods for Determination of Hazardous Substance (MDHS) 14/4 as guidelines. Only 79% of Pt mine workers, used their respiratory protective equipment (RPE), sixty-five percent were exposed to work shifts exceeding the recommended eight hours and 8.8% had been employed for more than ten years. The mean time-weighted average (TWA) dust concentrations between Facility A and B showed a significant difference (p < 0.026). The Pt mine’s inhalable concentrations (range 0.03–2.2 mg/m3) were higher than the respirable concentrations (range 0.02–0.7 mg/m3), however were all below the respective international and local occupational exposure limits (OELs). The Pt mine’s respirable crystalline silica (SiO2) quartz levels were all found below the detectable limit (<0.01 mg/m3). The Pt miners had increased health risks due to accumulated low levels of dust exposure and lack of usage of RPE. It is recommended that an improved dust control program be put in place which includes, but is not limited to, stockpile enclosures, tire stops with water sprays, and education on the importance of RPE usage.

Correlation between hardness and abrasive wear of grinding balls

The grinding ball is manufactured by the Algerian Foundries (ALFET – Tiaret). It is used by the cement industry to transform the rock into fine, used in the cement manufacture. This product undergoes very frequent wear. This wear occurs in various forms (abrasion wear and impact wear) and each has a varying impact on this product life. Abrasion wear is the result of friction between many surfaces (rock, crusher shielding and balls between them), between which a sliding contact occurs, and causes a metal wrenching and a mechanical disintegration of these surfaces. The impact wear is the result of the shock between these surfaces (rock, crusher shielding and balls) and the ball that hits these surfaces from multiple angles, causes their disintegration. Generally, wear resistance improves when hardness increases and a very hard material is more resistant to wear because it less risk to seize in presence of particles abrasive and it opposes their penetration in its surface layer. Wear is estimated, in this work, by the mass loss of the heat-treated balls. A correlation between the hardness and abrasive wear of the balls is established in this work.

Effects of Higher Percentage of Stone Dust Used as a Fine Aggregate in Concrete and Variation of Strength due to the Variation of Cement Content and W/C Ratio

– Sustainability and Unavailability play an important role while we choose material for manufacturing of concrete. Nowadays, both Central and State Govt. have taken legal action on the extraction of sand from the river bed due to the bad impacts on the river like changes the shape, slope of the bed and also in the channel morphology. Due to the implementation of this type of law, legal sand quarries did not able to make balance with the rapid growth of the construction industry. That’s why, to make profit and supply extra needs of sand to the concrete industry “Sand Mafias” involved into the illegal trades of the sand. To counteract these sorts of socio-economic problems, we have to go for an alternative fine aggregate. Though it may not be possible to replace fully, we have to concentrate on the sand being replaced by the high percentage of alternative fine aggregate. Stone dust is a by-product from rock crusher and it can be recycled by using it in the concrete and maintained the sustainability. As stone dust has acceptable properties of fine aggregate sand with regard to shape and texture, it can be thought of as an alternate fine aggregate but research is needed on the extent of sand replacement by stone dust. The present study is done keeping in mind the use of stone dust as high as possible. That’s why two Design Mix have been designed M20 and M25. For M20 grade of concrete sand has been replaced by stone dust 25%, 30% and 35% by volume and the basic strength properties of concrete have been investigated for the above replacements like compressive strength, flexural strength, split tensile strength etc. In case of M25 grade of concrete 30%, 40% and 50% replacement of sand have been done and variation cement content and water-cement ratio has been done by comparing the target mean strength of M25 grade of concrete.

Rock Moving Operation Using a Rod-Shaped Manipulator

At the working front in a quarry, a hydraulic breaker is used to break large rocks into suitable sizes before they are fed into a rock crusher machine. The purpose of this study is to automate the rock breaking operation using a hydraulic breaker. In rock breaking operations, because the range of motion of hydraulic breakers suitable for breaking rocks is limited, the operator of a hydraulic breaker has to use a chisel, which is located at the top of the hydraulic hammer, to bring large rocks closer before they are broken. In this paper, we describe an approach, using stereo vision, to recognize the positions and shapes of large rocks and the automation of rock moving operations. For rock recognition and rock moving experiments, we set up a scaled down experimental environment in a laboratory and use small rocks and a robotic manipulator in the experiments.

Gyro Rock Crusher and Asphalt Plant Sound Power Levels

Sound power levels including the distribution into octaves from a large 149 kW (200 horsepower) gyro rock crusher and separate asphalt plant are presented. These NIST-traceable data are needed for estimating sound pressure levels at large distances (such as occurs on adjoining property to a quarry) where atmospheric attenuation may be significant for the higher frequencies. Included are examples of the computed A-weighted sound pressure levels at a distance from the source, including atmospheric attenuation. Substantial low-frequency sound power levels are noted which are greatly reduced in the far-field A-weighted sound pressure level calculations.