Modern Quarrying Q3 2019

A Cat 329D excavator loads articulated haulers in the pit.

AT THE QUARRY FACE

downtime,” says Pretorius. The BDM plant currently produces between 1 000 and 1 500 tonnes of material per day. The Ag Lime plant produces about 450 tonnes a day of agricultural lime, excluding construction-related aggregates, which are typically produced per order. In terms of overall production, metallurgical dolomite constitutes about 70% of the total offtake per month. Construction aggregates and agricultural lime make up the remaining 30%. Belt weighing scales As part of its technology revolution, SPH Kundalila has installed real-time belt weighing scales, which give exact tonnages of material passing selected belts in real time. These have been installed on the metallur- gical dolomite product belt, the Ag Lime belt and on the out loading belt. A key feature of the belt weighing scales is that they are now GPRS- enabled, which allows them to send information to a server. Management can see, in real time, the exact tonnages passing through each belt, anytime and from anywhere. With this software, one can also download pdf documents and do Excel exports of the production figures. “The technology takes guesswork out of the production equation, which makes it easier in terms of production planning. This is

system is that you get slippage on the belts, especially during cold mornings when the belts are wet,” explains Pretorius. Another key intervention was to change the plant setup. Pretorius explains that previously the plant was an old linear system which ran in a straight line with a ‘scorpion’ belt setup. A scorpion setup comprises two belts running against each other all the time. “We had a lot of complications with the setup, which resulted in breakdowns and downtime,” says Pretorius. To get rid of the linear setup, the Sandvik H3000 EC cone crusher was rearranged from its usual middle position in the plant, and was moved up the line. “We put in three new belts and a hopper feeder and moved the cone out of the line it was previously located. The hopper was installed to regulate the feed rate of the cone to keep it at choke feed level. Previously, it was fed directly by the screen and you couldn’t choke it. With the hopper feeder, we can regulate the feed to keep it at a constant level,” explains Pretorius. Pretorius notes that a combination of these changes has resulted in about 20% increase in production. “We are now able to produce more, mainly because of the hopper feeder, which has created a bit more capacity. Production has also increased because we have very little

Several interventions, including a recent plant upgrade and the adoption of three major technologies – a drone system, an innovative dust suppression system and real-time belt weighing scales – have ushered in new levels of efficiency. Plant upgrade Bridgetown Dolomite Quarry runs two processing plants – the main BDM plant which produces metallurgical dolomite and the Ag Lime plant, which produces -2 mm agricultural lime and several selected aggregate sizes for the construction sector. In 2016, a decision was made to upgrade the main BDM plant. A key feature of the plant upgrade was the replacement of the old Svedala screen with the new Sandvik SF 1843 screen. “With the old screen it took us a couple of hours to replace screen media. With the new Sandvik SF 1843, it takes us less than an hour to do the same job. This is proof enough that new technology has its advantages,” says Louis Pretorius, site manager at Bridgetown Dolomite Mine. As part of the upgrade, the Sandvik H3000 EC cone crusher was also completely refurbished. “We also replaced our V-belt and pulley- driven gearboxes on the plant. We now operate a gearbox and a motor directly without the need for pulleys. A major shortcoming of the V-belt

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MODERN QUARRYING QUARTER 3 - 2019