As outlined in a recent online Solid Ground article by Sandvik, the Mafube opencast coal mine in Witbank, a 50-50 joint venture between Anglo American and Exxaro Resources, was one of the first operations globally to invest in an automation ready DR412i blasthole rig in 2018, with which it is now getting impressive results.
Designed for dependable drilling in both soft and hard rock, the automation-ready Sandvik DR412i blasthole drill rig delivers high rotary power and feed force. Capable of drilling holes with a diameter of 216-311 mm (8.5-12.25 in) down to a maximum multi-pass depth of 75 m (246 ft), Sandvik DR412i can be fitted for both down-the-hole and rotary drilling and delivers greater penetration at lower operating costs. Its drill-to-depth feature enhances efficiency and productivity.
Mafube means “dawning of the new day” in Sesotho, and the aptly-named Mafube colliery in South Africa’s Witbank coalfield has indeed entered a new era. The 50-50 joint venture between Anglo American and Exxaro Resources commenced operation in 2007, producing high-quality thermal export coal and a lower-grade product for a nearby power station. Mafube produced 5.3 Mt of coal in 2019 and is targeting an increase to 5.8 Mt during 2020.
Mafube had depleted its Springboklaagte reserve by the end of 2018 and initiated a project to bring the nearby Nooitgedacht resource into production, thereby extending mine life to at least 2032. Following the procurement of equipment and the installation of a overland conve7 kmyor to move new ROM product to the washing plant at Springboklaagte for processing, the Nooitgedacht pit began producing mid-2018.
While many similar operations use draglines for overburden stripping, Mafube is among the few coal mines in the country to move its waste with rollover dozing. Overburden is bulldozed back into the first cut from the next cut, enabling the continuous rehabbing of mined-out areas while a modest truck and shovel fleet excavates the exposed coal.
Mafube Mining Manager Kennedy Botsheleng says drilling accuracy is essential for the operation. “All mining activities after drilling rely on accuracy of the drilled pattern,” he says. “If you don’t get the drilling right, you’re likely going to have a bad blast and then you don’t have a good cast. We move about 30 percent of the overburden material with cast blasting, and doze 70 percent of the remaining material to truck and shovel bench or doze to coal, depending on the depth of the coal. So drilling is very key to our operation.”
Sandvik Driller’s Office software enables Mafube to wirelessly transfer drill plans to Sandvik DR412i and further improves accuracy, hole quality and fragmentation. “The planner sends the plan to the drill from his office, which is very lekker for him,” Botsheleng says. “Some days he even sends it from home. Accuracy is about 98%. Our surveyors can now be utilised more efficiently.”
Operating costs have been “way below budget” according to Botsheleng and the drill routinely finishes its benches ahead of schedule. “The maintainability is excellent and maintenance costs are highly competitive,” Botsheleng says. “Utilisation is higher than previous drills we’ve operated.”
The new rig surpassed 5,000 engine hours in January 2020 and continues to impress mine management. “The records are there,” Botsheleng says. “The drill has drilled 1,000 metres a day. The machine was parked for two weeks because it has completed its area that’s been allocated. So the machine is doing very, very well. I mean, a thousand metres a day? You’d be stupid not to buy the drill.”