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Murray & Roberts Cementation Showcases Design Innovation and Capabilities with IVANPLATS' NO.2 Headframe
Sunday, 1 November 2015
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.
Design 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 Mtpa operation. 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 hoisting 6 Mtpa 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 considerable concrete structure – 100.5 metres in height. The lined shaft will be 10 metres in diameter. The headframe will house all equipment necessary for sinking and operating the shaft thereby reducing the surface footprint.
The No. 2 shaft will be sunk to a depth of 1 080 metres and will accommodate two “high mass, high speed” 40 t skips running at 18 metres per second, Genis emphasises. It will also be capable of conveying 225 persons in a single deck using a cage and counter 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. He believes that Murray & Roberts Cementation’s shaft sinking and mining expertise contributed towards securing the contract.
Ivanplats expects to start early works for the No. 2 shaft in 2015, including the box cut and hitch foundation civil works. The box cut designs are complete and the contract for the early engineering works for the winding equipment 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 unobtrusive lighting and have also implemented design initiatives to reduce noise and dust levels. The overall aesthetic look also had to be considered and subsequently we have designed a simple headframe with fluted features using concrete throughout,” he continues.
The “limited real estate” necessitated that the two tower-mounted Koepe winding systems be positioned about 82 metres above ground. Additionally, a single drum auxiliary winder is mounted at a lower elevation in the headframe.
“Working at these heights with heavy concrete and steel loads presents significant constructability challenges,” principal engineer 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 reviewing 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 conditioning) system to cool the winding equipment and pressurise the upper three levels.
“Our headframe design provides Ivanplats with pre-sinking flexibility from either the collar or lower level, enabling a fast transition into actual shaft sinking,” says Jan Vermaak, Murray & Roberts Cementation mine engineering manager.
A purpose designed sinking headgear is not required for the initial sinking phases. “We have incorporated start-up sinking arrangements 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 sinking to permanent will be minimised,” says Bethel. This equates to cost and time savings for the project.
Designing complex structures such as the Platreef headframe are generally considered challenging but thanks to Murray & Roberts Cementation’s employment of Bentley software – the task was simplified and the risks associated with design drawings across multiple in-house disciplines reduced.
The Bentley ProStructures software easily allows structural engineers, detailers and fabricators to create 3D models for both concrete and steel and automatically creates documentation, details, and schedules. The open working environment and programming interface supports standardisation within a single model which ensures cohesive interconnectivity and interfacing between mechanical, electrical and piping designers while still working independently of each other.
The software features assisted Murray & Roberts in performing thorough risk assessments and drastically reducing the number of drawings generated, minimising the potential for error.