SAG MILLING – Gearless drive system from ABB

WESTERN AUSTRALIA - Five years in storage have failed to affect the performance of the ABB gearless drive on a SAG...
WESTERN AUSTRALIA - Five years in storage have failed to affect the performance of the ABB gearless drive on a SAG mill at the St. Ives gold mine belonging to GOLD FIELDS of South Africa.

The mill was originally ordered in May 1997, but shortly before the manufacturing was completed, the then-owner of St. Ives gold mine, WESTERN MINING CORP., put development on hold. The equipment was stored in a warehouse on the Rotterdam docks.

In December 2001, Gold Fields acquired the St. Ives project near Kalgoorlie, and only in 2003 did the new owner decide to go ahead with the project and to install the 36-ft SAG mill and its 13.5-MW gearless mill drive at St. Ives.

The pre-commissioned containerized E-house, which includes the complete power and control electronics for the mill and the ring motor, was transported back to Switzerland, where it was fully re-tested. The Gold Field's engineer attending these tests was positively surprised by the test results, which showed that after more than five years in the warehouse the material was still like brand new. Only a few updates were made and some additional items were installed.

The transformers and the ring motor itself were shipped directly to Australia. ABB made various recommendations for pre-installation tests on these major components, which were performed by ABB specialists on site, but also for system upgrades that were developed over the last five years and customized for St. Ives.

This proactive approach led to the installation, implementation of improvements and commissioning being realized with a minimum of resources and time. This was only possible because of the good co-operation between the parties involvedGold Fields, its consultant and ABB. Find a local ABB contact at

For the year ending June 30, 2004, the St. Ives mill treated 6.74 million tonnes of ore and recovered 543,000 oz of gold at a total cash cost of US$297. Underground, pit and stockpiled mineral resources are 97.3 million tonnes grading 2.5 g/t Au or 7.68 million oz of gold.


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