Tenova TAKRAF Africa (formerly Bateman Engineered Technologies) is putting the final pieces together in completing an order for the supply of a 5.5- x 2.75-m, hydraulically-driven SAG mill to Ontario Graphite, operators of the Kearney mine located in Kearney, Ontario, Canada, about 300 km north of Toronto. This is the largest confirmed graphite resource in North America.

“Tenova’s scope of work includes the engineering, manufacturing, shipping and technical assistance during erection of the SAG mill’s feed end, shell, discharge end, drive and main bearings, as well as all supporting equipment (lubrication and jacking systems),” said Tenova TAKRAF Engineer Pieter Van Der Walt. “The main hydraulic motor and rubber shell liners were outside Tenova TAKRAF’s commercial scope of supply, but inside its technical scope of supply.”

The mill is a conventional SAG (semi-autogenous grinding) mill in all ways apart from its drive assembly and, it is center-driven at the discharge end using a Hagglünds hydraulic motor and power pack. “To date, this is the largest hydraulic motor installed on a SAG mill, with 950 kW of power, torque of 1,200 kN.m (start-up) and 650 kN.m (operational), and speed of 13.86 rpm,” said Van Der Walt.

Since the mill had to be retrofitted to an existing foundation, a number of adaptations were required to maintain the mill centerline, as well as feed-end and discharge-end positions. Certain additions were required to anchor the main motor torque arm.

“Center-driving a mill at the discharge end brings significant challenges where the discharge of ground material is concerned,” Van Der Walt said. “The parts used to connect the motor to the mill trunnion have a dual function—to drive the mill and to discharge ground material. Exposure of structural parts to abrasive material must be avoided to ensure their integrity when exposed to high torsional loads during operation and, a special discharge/drive drum and protective liner were developed to counter possible abrasion.”

“The SAG mill is the final and most valuable piece of the processing puzzle for us,” said Jerry Janik, general manager of Ontario Graphite’s Kearney mine. “Delivery of the SAG mill marks a significant milestone in our path toward graphite production, and on top of the fact, that we’re reactivating a mine with already-proven resources and infrastructure, it gives us a tremendous advantage over any of our competitors.”

Tenova TAKRAF was awarded the contract to oversee shipping of all components to site. The Kearney mine is slated to begin production in 2013.