Modern Mining May 2019

CRUSHING, SCREENING AND MILLING

A Weba chute system being installed in a mill circuit. processing plants is another growing issue that chute design can help to address. As health and safety standards on mines continue to rise and compliance becomes tighter, there is greater pressure on mines to ensure cost effective dust mitigation strategies. Baller notes that while many service providers offer mines a range of dust sup- pression ‘add-ons’ or ‘band-aids’, the primary solution lies in good chute design. The company’s research has shown that levels of dust in the working area can be reduced by 70 % or more by scientifically controlling the flow of material and air at the transfer point. “We begin with understanding that material tends to aerate when it is in free- fall,” he says. “When it comes to an abrupt stop or changes direction suddenly – as occurs when the flow is uncontrolled – that air is forced out, creating dust.” If a mine limits its dust-reduction strate- gies at transfer points to only suppressing or extracting dust, he notes, it is missing a key underlying cause of the problem. In fact, where extraction fans are placed without material flow in mind, the result

may even exacerbate the prevalence of dust as the induced air flow could be moving counter to the material flow. “In one recent application, we assisted a power station in Wyoming in the US, where the dust levels at their transfer sta- tions were exceeding the compliance limits set by environmental authorities,” he said. “By redesigning the chutes, we were able to reduce dust levels by 78 %, bringing them well within regulations.” Such has been the success of Weba Chute Systems’ proprietary design solutions that half of its production is today destined for customers outside of South Africa, includ- ing markets as far afield as North America, South America and Russia. The company has supplied over 4 300 chutes into the global market over the decades, of which about 3 500 are still operational. The chutes from Weba Chute Systems are applied in soft and hard rock appli- cations and handle lump sizes from 1,4 metres weighing about two tonnes, right down to fines or powder. Throughput rates range from as little as 40 to 50 tonnes per hour up to 12 000 tonnes per hour, in all climates and conditions. 

May 2019  MODERN MINING  57