Stacking the odds

The main challenge faced in build ing mining infrastructure in the Pilbara is the remoteness of the region.

To deliver and then construct a fifty metre high iron ore stacker at Rio Tinto’s Mesa A Mine, the task seemed considerable.

At the height of a fifteen storey building, the machine weighs 250 tonnes and is one of the largest stack ers of its type in the world and can be seen from ten kilometers away.

For the creation and erection of the machine, Tenova SPA and SEMF created a joint venture responsible for the stacker’s design and fabrication.

In the space of 16 months the machine was completed, from incep tion to delivery and construction.

Tenova SEMF project manager James Manners puts this down to four key factors – that design through to fabrication was carried out in 3D, the pre-ordering of steel prior to comple tion of detailed design, the trial assem bly of major components in a work shop, and the correct sequencing of the components delivery.

The use of 3D technology to design and detail the stacker “enabled the design team to get the complex geom etry of the machine right the first time and allowed the fabricators to base the construction off of the 3D model,” SEMF engineer Bob Dunbabin said.

Using 3D modeling significantly reduced the turnaround time from design to delivery.

This allowed for the pre-ordering of the steel required to fabricate the stacker, cutting down on long lead times.

Following the fabrication of the stacker, trial assembly of the major components were carried out in the workshops, enabling the Tenova SEMF joint venture to examine a number of different ways to pre-assemble the structure for the quickest and easiest method of erection while eliminating potential construction problems.

“Usually stacker alignment is diffi cult in the final assembly stage, espe cially for one of the size of Mesa A, however we were able to achieve align ment to within 4mm without any adjustments,” Dubabin said.

While not only reducing time on site, the pre-assembly process also reduced OH&S risks.

Once the trial assembly stage was completed the stacker was then disman tled and sent by truck to the Mesa A mine.

The correct sequencing of the trucks carrying the stacker compo nents was another major factor in its quick construction.

It was vital Tenova SEMF matched component delivery to the end erec tion sequence of the iron ore stacker, which was difficult due to the complex ity and size of the project which required twenty trailer loads of components driven to the remote North West region of Western Australia, Manners said.

“Getting it right was important as crane rental costs are so high and delays caused by small errors can end up costing contractors thousands in unnec essary expenses,” Manners added.

HWE Mining, who had overall responsibility for design and construc tion of the mine, pre-assembled the machine on the ground into large compo nents, which minimised work at heights, further reducing OH&S risks.

Assembly of the stacker on site took two weeks, “had assembly of the Mesa A stacker happened in a more piecemeal way it would have taken significantly longer to create and erect,” Manners said.


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