Modern Mining May 2021

CRUSHING, MILLING AND SCREENING

for any mineral sizer or double-roll crusher in high tonnage applications. The replacement sizers were required to operate at 1 700 tph. We had to achieve this on the available footprint.” In the absence of red-line drawings of the build- ing or its structures, the MMD team recruited a service provider to create a 3D scan of the entire building. This was converted into an as-built, 3D Computer Aided Design (CAD) model. MMD then based its design on this model to ensure that the available footprint could accommodate the replace- ment equipment. “We had to design the machines specifically for the operating conditions,” says Koch. “The result was some 12 t heavier than the original machines, and we had to conduct a finite element analysis on the sup- porting structures.” After some minor modifications were made to the structure in the critical identified areas, installation of the MMD equipment could commence. “However,” says Koch, “there were only two 20 t overhead cranes available. Our primary sizer weighed about 150 t and the secondary around 78 t. We overcame this obstacle by shipping in the com- ponents and building the machines in situ.” He says the machines are currently running at 2 200 tph, with 98% passing 120 mm, whereas the previous installation produced -200 mm. The instal- lation was commissioned in 2018. “We recently changed out a set of shaft assem- blies and the client surpassed the million-tonne mark with just one set of components. We also designed bespoke gearboxes for them which, at the end of the day, added another product to our range.” Witbank Coal Mine In 2018, MMD was awarded a contract for the design, delivery, installation and commission- ing of a run-of-mine (RoM) primary sizing station, which included an MMD 1150 mineral sizer and an

existing data which does not necessarily represent the physics involved. “As wear properties differ from mineral to mineral, we marry the wear component with the mine-specific material, for an optimal match,” says Koch. “We gather various minerals from the mines and test them in a bespoke test bench against our wear materials to see where we can optimise component life.” The results of both the Vison Project, on-line con- dition monitoring and standardisation metrics can be used to create simulations that predict how rapidly the wear material will degrade, greatly increasing the company’s Opex estimation accuracy. Clients can also be alerted beforehand to order spares, for instance, and so ensure that unplanned downtime is minimised and that spares holdings are optimised. “The goal is to be in a position to offer a complete digital twin of our equipment to clients that are head- ing in this direction,” says Koch. Lafarge Limestone Quarry In 2017, MMD Africa commenced work on a brown- fields project at a limestone quarry in Calabar, Nigeria, where two mineral sizers by another sup- plier had to be replaced. According to Koch, the client directive was to improve the production ratios of the existing machines, which were producing sufficiently from a throughput point of view, but caused unacceptable levels of downtime. “The existing machines were situated in an enclosed cement building with space for primary and secondary machines only – there was no room for a tertiary machine in accordance with the process requirements.” He says the client’s requirement was to size mate- rial from lump sizes of 1,5 x 1,5 m down to -120 mm in two processes. “This is basically a 12:1 reduction, quite a stretch

The 500 tph max throughput NaviCore 500 mineral sizer is available on a rental basis.

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28  MODERN MINING  May 2021