The mechanical contractor was Competitive Construction Services (CCS) of Vanderbijlpark, Gauteng. The project was completed Lost Time Injury (LTI) free due to the close working relationship between the professional team and a strong focus on health and safety. “We were contracted to remove an old mill weighing 225 t, with a radius of 31 m, and to replace it with a new one weighing 170 t,” Grant Parker, project manager at Johnson Crane Hire, says. The successful completion of the project marked the culmination of two years of detailed planning and engineering.
Johnson Crane Hire had a 250 t crawler crane on site at the Selous Metallurgical Complex since the beginning of September 2014, which was used to assemble the new mill. These components weighed about 60 t to 70 t each. “We then brought in a LR 1600/2 600 t crawler crane from Europe to take off the gears and remove the old mill and install the new one, as we were concerned our LR 1750 Liebherr crawler crane was not going to finish on time at a project at Nacala in Mozambique,” Parker explains.
Johnson Crane Hire had a tight window from 29 September to 22 October 2014 to complete the heavy lift project, which was when the Selous Metallurgical Complex had a shutdown period. The 600 t crawler crane completed the lift on 13 October, well within the timeframe. “The entire project went off very smoothly and we managed to hand the new mill over ahead of time. It was a tremendous team effort in conjunction with our client as well as the mechanical installation crew,” Parker comments.
Kurt Domain, project engineer at FLSmidth, explains that as the OEM, FLSmidth supplied the replacement shell of the new semi-autogenous grinding mill in sections for assembly on-site. “At the point where it was ready for installation, the complete mill was lifted by the 600 t crane directly into its final position. We worked very closely with the Johnson Crane Hire team during this process.”
Domain comments that what differentiated this project was the fact that the mill shell was essentially preassembled on site and then lifted into place as a single unit. “Normally what we do is simply build the shell on the foundations, where the bearings are located. However, in this instance we had to adopt a modular approach in order to cater for the production and thus time constraints. This meant a great degree of upfront planning was involved.”
Parker adds that the use of the 600 t crawler crane in particular not only reduced the downtime at Selous, but also contributed to greater safety on site. “FLSmidth is an established client of ours and we have done work for them in the past, as we have for Zimplats, with which we have a very good relationship. In fact, our 250 t crawler crane went straight onto another job at the Ngezi concentrator for Zimplats.
Parker says that the 600 t crawler crane was dispatched to Johnson Crane Hire’s Vanderbijlpark facility to be tested, with additional luffing, before embarking on its next project.
“We comply fully with industry safety standards and perform comprehensive risk assessments before each lift. Training is provided both externally and at the Johnson Crane Hire training centre to ensure that our operators are up to date on the latest technology,” Parker says.
Zimplats Holdings Limited is 87% owned by Implats. At present it operates four shallow mechanised underground mines and a concentrator at Ngezi. The Selous Metallurgical Complex, located some 77 km north of the mine, comprises a concentrator and a smelter. Zimplats’ Phase 2 expansion project remains on schedule, and is expected to increase production to 270 000 ounces of platinum in matte in 2015.