New mill grinds down costs and boosts efficiency at Savage River

Mill upgrade to improve output efficiency

Grange Resources Limited owns and operates Australia’s largest integrated iron ore mining and pellet production facility and is the country’s oldest magnetite producer. Located 100km southwest of Burnie in north western Tasmania, are the company’s Savage River mine and concentrator.

Grange’s concentrator at Savage River houses two Hardinge AG mills that were originally installed in the late 1960s. By 2005, maintenance personnel noticed cracks starting to appear in their shells and cones. The mills required ongoing repairs that resulted in plant downtime and there was always the risk of a catastrophic failure.

With the mine’s operation expected to extend until at least 2034, Grange’s management team decided that in order to ensure concentrator reliability and to improve output efficiency, these mills would need to be upgraded.

“Our engineering team had done a great job of extending the mill’s 20-year design life to over 45 years. So while there is no doubt that the mill was at the end of its life, we mainly needed better reliability and efficiency,” notes Tim Dunbabin, Grange Resources’ Senior Project Engineer.

Grange Resources’ Engineering Superintendent, Wayne Peck explains further: “Starting from the pit, right through to the end of the ship loader, our customers’ requirements are our focus – ‘from mine to metal’ as we say. Reliability of supply depends on the performance of our personnel and the processing equipment they use; remaining price competitive depends on keeping our costs in check. Energy is our biggest cost, and an area where even small changes can have a big impact.”

Energy efficiency achieved: Grinding more with same power

In 2011, Grange Resources Limited awarded Metso a EUR 5.7 million contract to engineer, supply, install, and commission the first of two planned new mills.

How was it done?

The project scope involved increasing the production volume with a new rotating element that would accommodate a charge weight of 344 tonnes, but with the requirement to use the existing footprint and some of the components from the original 1966 mill, adding a lot of complexity to the design.

The original mill was based on a single shell design, and although it had lasted more than 45 years, the new design had to be stronger to ensure trouble-free operation beyond the mine’s expected lifespan of 2034.

So in the first instance, Metso’s new design replaced the single cone-shell with a two-piece structure that was 3.6 meters wide (distance from feed to discharge) and featured long-life Polymet rubber liners.

Wayne Peck cites Metso’s ability to offer a complete package as a key deciding factor. “While we were familiar with Metso’s capabilities, for me the main decision lay in the overall package. Although other suppliers had the elements of good expertise or comprehensive equipment supply, when we looked at Metso we had the whole project covered. If we had an issue, we would only need to direct questions to one point of contact.”

Wayne Peck also highlights how close inter-company teamwork maximised efficiency and cost reductions. He says, “Working so closely together on the project meant that Metso could assist us to look at the design of the project as a whole, and to not just consider the quickest or lowest cost solution, but to look at improving quality and throughput, reducing running costs, and overall long-term maintenance.