Modern Mining September 2016


steel was fabricated by Louwill Engineering), are the girder beams, with a total mass of 50 tons, and the supporting columns and floor steel, with a total mass of 40 tons (excluding the floor decking and handrails). Says Wells: “The eight main girder beams have dimensions of 11 m in length and 1,5 m in height. They were taken underground in sections which then had to be spliced together, with each splice requiring 92 bolts. In fact, we had one employee totally dedicated to looking after the bolts and ensuring that none went missing! Similarly, the sixteen 10 m long columns sup- porting the feeder and chute levels also had to be spliced together. “We planned everything to the last detail, with the steel being laid out on the bank at surface and hard stamped and marked to allow us to get everything to the workplace in the right sequence with the right bolts and splic- ing plates. Everything was placed on sleds on surface to facilitate handling and taken down in the cage of the main shaft. Once under- ground, these sleds were towed by an LHD to the workplace.” Certain elements of the structure – for exam- ple, the floor grating and the vibrating feeder frame (which is independent of the rest of the structure) – were trial assembled on surface, again to reduce the chances of any unforeseen problems arising during installation. Highlighting some of the more interest- ing parts of the overall bunker project, Wells notes that the logistics of concrete supply were challenging. “Concrete pours which on sur- face would be routine become difficult when undertaken 200 m or more below surface,” he explains “We had to transfer the concrete – a pumpable mix supplied by Lafarge – from sur- face to 4 Seam level via large diameter drilled and cased aggregate holes and then distribute it using a positive displacement concrete pump. Alongside each aggregate hole, we needed a communication hole so that teams on sur- face and underground could liaise. The key was to avoid blockages in the aggregate holes – unblocking them could be very time consum- ing – and we were generally very successful in achieving this objective.” Although not within the scope of the origi- nal contract, the electrical and instrumentation (E&I) work for the bunker and box front – including the installation of a MCC panel – was undertaken by Murray & Roberts Cementation. “We both procured and installed the E&I sys- tem,” says Wells. “This is not normally part of our service offering but we were asked to take it on and the work went very well.’

Finally, Wells notes that the Impumelelo project was recently named as the best per- forming project within the Sasol Mining group, receiving the ‘Best Overall Performance of the Year’ Award for 2015 from Kobus Louw, Sasol Mining’s Vice President, Projects & Sigma. “The award recognises the achievements of the entire team responsible for designing and implementing Impumelelo including Sasol Mining itself, as well as the EPCM contractor – the RSV ENCO Hatch Goba Joint Venture – and the major contractors, notably Murray & Roberts Cementation and – in the case of mate- rials handling – ELB Engineering Services,” says Wells. “The bunker, of course, represents only part of the overall project but is neverthe- less a critical part of the mine’s infrastructure and we’re proud of the fact that we’ve been able to deliver it on time and within schedule – and, perhaps most importantly of all, with an excel-

The main shaft headgear at Impumelelo.

lent safety record.” Photos by Arthur Tassell

September 2016  MODERN MINING  25

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