Modern Mining January 2019

DIAMONDS

planned. As Kemp told the media group: “We stopped the old plant on a pre-determined date and 21 days later started up the new one. Within a month, it was able to treat ROM mate- rial at design capacity. No processing took place over the three-week transition period. We did, however, stockpile the ore coming up from the mine, confident that we would be able to treat it in the new plant within the financial year – and that’s exactly what happened.” He added the old plant was still largely in place but would, over time, be dismantled and removed. Of course, it is almost a given that a plant of the sophistication of the new facility at Cullinan will have state-of-the art electrical and control systems and, as mentioned, this was provided via multiple contract packages by

have been deployed for primary recovery, re- concentration and final concentrate treatment of diamond-bearing ore. The XRL sorters have been selected due to their high efficiency in recovering Cullinan’s diamond profile, including Type II diamonds which are characterised by low luminescence levels under X-ray exposure. Kemp noted that Petra did look at the possibility of using XRT (X-ray transmission) sorters which have performed so successfully at the Karowe diamond mine in Botswana and at other opera- tions globally but said that extensive tests had shown XRL technology to be more effective on Cullinan ore. Construction of the plant took 35 months, a very creditable achievement given the scale

The 60 MVA, 88 kV/6,6 kV bulk electrical substation dedicated to Cullinan ensures secure energy supply to the mine and its operations.

The installation of all equipment and complete electrical construction scope was executed by Zest WEG Group’s construction busi- ness, EnI Electrical.

and complexity of the work and the ‘brownfield’ nature of the project. As Kemp remarked, many overseas visitors to the plant have expressed surprise at the short con- s t r uc t i on t ime f r ame . While Petra was largely responsible for the design, the execution was carried out by MDM Engineering with roughly 1 800 people being employed on site at the peak of construction. Commissioning was com- pleted in October 2017. The switchover from the old plant to the new facility was meticulously

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January 2019 _ MODERN MINING _ 41