MechChem Africa January-February 2022

Dust control vital to miners’ health Dust has long been a health hazard in mines where metals and metalloids are carried in atmospheric dust, exposing workers to toxic contaminants. Izak Potgieter of Weba Chute Systems makes the argument for implementing dust control measures, particularly around conveyor transfer chutes.

tions and material type. “The lump size of the material being moved is usually a key factor affecting dust levels,” he says. “To un- derstand the levels of dust being produced, data on the size and material type needs to be collected and analysed.” The speed of conveyor belts will also affect the dust levels, Potgieter says, de- pending on the tonnage per hour travelling through the chute. Reducing the dangers of dust in this environment requires bet- ter flow control of the moving material, including velocity and impact on convey- ors and in chutes. Weba chute systems are engineered for optimal control of the material flow, which inherently reduces dust levels. “We develop bespoke solutions for transfer points based on years of re- search and development, ensuring that mine employees are protected from ex- cessive exposure to this health hazard,” Potgieter concludes. www.webachutes .com

The Occupational Health and Safety (OSH) Act specifies certain dust exposure limits, and mines can measure and control dust.

Multotec’s hammer samplers allowtwocon- secutive samples to be taken fromthe prod - uct stream in quick succession, ensuring accurate results for themine and customer. “Asinglesample increment cannot simply be divided into roughly two equal parts,” says Refilwe Makgae, senior application engineer at Multotec. “This can result in up to five of the nine sampling errors occurring in a single step.” Sheemphasises that eachconsecutive in- crement must instead be carefully diverted to its ownbin, so that successive increments D ust, particularly the smal ler particle range of around 0.3 μm, has a serious impact on human health, says Izak Potgieter of Weba Chute Systems. Dust from minerals such as coal, silica and other finely powdered materials can all damage the lungs and air passages. “The Occupational Health and Safety (OSH) Act therefore specifies certain dust exposure limits, requiring mines to measure and control dust to ensure that levels are managed,” says Potgieter. “Health and safety officers must monitor this on a regular basis as part of their compliance standards.” He notes that dust is often generated during the transportation of minerals on conveyors and through transfer chutes. Measuring dust at these sources can be done using a handheld dust meter, which can typi-

cally gather the data required in 30 second intervals with 0.003 split seconds per mea- surement. Thedata fromthisprocess can then be profiled into a scatter plot, considering factors such as lump size, belt speed, relative humidity, wet-bulb temperature, wind condi-

The speed of conveyor belts will also affect the dust levels depending on the tonnage per hour travelling through the chute.

High-precision, accurate sampling for mines and their customers

donot contaminateeachother.Multotechas therefore developed a reliable flopper gate that is easy to operate and gives feedback about the flopper positioning. “This ensures that agoodseal is achieved, preventing sample cross-contamination,” saysMakgae. “For existingoperationswhere this new requirement is imposed, this inno- vation can be easily retrofitted.” She notes that high levels of precision in sampling can only be achieved with fine design tolerances for each application. For this purpose, Multotec has developed soft-

ware integration mod- els across AutoCAD Inventor and pro- gramming code to automate parts of the design. The process

uses pre-programmed design logic and interpolates from the company’s data library, which covers a worldwide footprint of over 800 ham- mer samplers in the field. www.multotec.com

20 ¦ MechChem Africa • January-February 2022