Modern Mining November 2015

PLATINUM

Design of high-tonnage headframe completed Murray & Roberts Cementation has demonstrated its high quality design and drawing capabilities having recently completed the design of Ivanplats’ mechanised, high tonnage Platreef No 2 shaft headframe. The design of a headframe of this magnitude is a first for the company and marks a huge milestone achievement, says Theo Genis, Murray & Roberts Cementation study manager.

D esign of the No 2 Shaft headframe for the first phase of Ivanplats’ Mokopane project commenced in 2014. The project, designed to produce 433 000 PGM ounces per annum, will ultimately be a 12 Mt/a opera- tion. Ivanplats is a wholly-owned subsidiary of Ivanhoe Mines. The design of the No 2 Shaft headframe was awarded in June 2014 to shaft-sinking expert Murray & Roberts Cementation. It will be the main production shaft, capable of hoist- ing 6 Mt/a of ore, and will also transport large mechanised equipment between surface and underground. By comparison with most steel-frame PGM headgears in South Africa, it will be a consider- able concrete structure – 100,5 m in height. The lined shaft will be 10 m in diameter. The head- frame will house all equipment necessary for sinking and operating the shaft thereby reduc- ing the surface footprint. The No 2 shaft will be sunk to a depth of 1 080 m and will accommodate two “high mass, high speed” 40-t skips running at 18 m/s, Genis says. It will also be capable of conveying 225 persons in a single deck using a cage and coun- ter weight arrangement. “This milestone achievement can largely be attributed to our Platreef project team, who dedicated themselves to delivering a functional quality design,” says Genis. Ivanplats expects to start early works for the No 2 shaft this year, including the boxcut and hitch foundation civil works. The boxcut designs are complete and the contract for the early engineering works for the winding equip- ment has been awarded to South Africa-based FLSmidth. The tall headframe will be located in close proximity to a number of communities, Genis notes. “As a result, we have incorporated unob- trusive lighting and have also implemented

design initiatives to reduce noise and dust lev- els. The overall aesthetic look also had to be considered and subsequently we have designed a simple headframe with fluted features using concrete throughout.” The “limited real estate” necessitated that the two tower-mounted Koepe winding sys- tems be positioned about 82 m above ground. Additionally, a single drum auxiliary winder is mounted at a lower elevation in the headframe. “Working at these heights with heavy con- crete and steel loads presents significant constructability challenges,” principal engi- neer Charles Bethel admits. To compensate for potential obstacles in this regard, Murray & Roberts Cementation established close ties with its infrastructure sister company and spent a significant portion of its time review- ing handling equipment and crane lifting arrangements. Time was allocated to power supply, cabling and piping layouts to ensure circuits which will be easy to install and maintain. Chiller plants located on the headframe roof will form a HVAC (heating, ventilating and air condition- ing) system to cool the winding equipment and pressurise the upper three levels. “Our headframe design provides Ivanplats with pre-sinking flexibility from either the col- lar or lower level, enabling a fast transition into actual shaft sinking,” says Jan Vermaak, Murray & Roberts Cementation mine engineer- ing manager. A purpose-designed sinking headgear is not required for the initial sinking phases. “We have incorporated start-up sinking arrange- ments into the main headframe. By mass, approximately 93 % of the steel required for the headframe will be permanent at the start of sinking, meaning the changeover from sink- ing to permanent will be minimised,” says Bethel. This equates to cost and time savings for the project. 

Murray & Roberts Cementa- tion has recently completed the design of Ivanplats’ mechanised, high tonnage Platreef No 2 shaft head- frame.

“Working at these heights with heavy concrete and steel loads presents significant constructability challenges.”

November 2015  MODERN MINING  35