Mechanical Technology February 2016

⎪ Special report ⎪

extra on the offsite modular construction approach, R79-million was saved. The main reason? “The provisional and general budget virtually disappeared, because all the work was done offsite. Very few contactors had to be paid for travel, accommodation or material shipping costs to the site. In addition, the contingency budget went unspent, because there were no unexpected ad- ditional costs due to onsite issues. “And the knock on savings were outra- geous. We closed a site with running costs of R150-million per month five months early. As a result, 1.4-million tons of ore was put through the mine before it was due to open – and the capital expenditure for the development of Kolomela, which was about R8.4‑billion, was paid off in 24 months,” Jackson reveals. Pit dewatering at Kolomela is achieved via 16 boreholes that lower the surround- ing water table. “The water is fed into an eight-million litre water tank and it is then pumped 18 km as potable water to Beeshoek, into the Vaal Gamagara municipal intake at up to 1 500 m 3 /h. “While the mine had moved towards offsite modular designs with respect to its substations and MCCs, the pump house itself experienced civil delays. We had a fully functional MCC control room and all of the medium-voltage infrastructure onsite and operational, but the pump sta- tion building hadn’t been completed. So, while massively successful on the electri- From electrical to mechanical plant

cal side, we were still being hampered by delays on the civil and mechanical side,” Jackson says, adding, “the budget for the pump station building was originally in the order of R1.8-million, but it ended up costing well north of R4-million – and it was more than eight months late.” “Onsite construction of plant at re- mote mines is such an onerous thing. A project can be hampered by continuous delays, due to late deliveries of inputs, the wrong people being sent to site and a host of safety and security restrictions that make rapid progress impossible,” he explains. Following the success of Kolomela

Above: Based on its success at Kolomela, Efficient Engineering now builds fully functional e-houses, includ- ing the shells for the substations, motor control centres (MCCs) and control and instrumentation (C&I) rooms as single integrated modules, and fully equips them offsite. Left: A modular pump station was built by Efficient Power to pump and additional 1 800 m 3 /h at a 40 m head from the deepening pit. Centre: To accommodate pumps, decoupling vibration dampers and reinforced mountings carry the 35 t of trust down to the 3.0 t concrete mounting plinth below the ‘building’. Shuttering formwork and a steel reinforcement cage was also incorporated below each pump. Below: Built into the housing structure is an overhead crane to enable installation and servicing of the heavy pumps and piping systems.

Mechanical Technology — February 2016

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