Design and wear of SAG mill shell liners at Brunswick mine
An AG/SAG mill was commissioned at the Brunswick mine concentrator in October 1998. This paper discusses the original shell top hat liner design for the bi-directional AG/SAG mill, observed liner wear, subsequent liner design modifications, and benefits.
The original liners were steel chrome-moly steel Norsteel with rubber grates and rubber-lined pulp lifters. The design was based on experiences of other AG/SAG mills and recommendations by the liner supplier, Norcast. Liner design modifications were made in an iterative fashion after observing the wear rate profile of the liners; over ten liner sets were implemented. Shell liner design improvements were supported by a design of experiment approach in conjunction with DEM charge motion simulations. Design optimization took into account lining costs and impacts on operating performance.
Liner measurements were performed on a monthly basis. Calculations of wear life were made and changes in the liner configuration undertaken as a result of the analyses to improve liner life and reduce scrap loss.
The team approach to the liner design improvement process is described, with emphasis on the application of the design of experiments. The liner wear history and mill operating performance are presented.
A structured methodology for measuring and analyzing liner wear was developed. This data was used in predicting liner life and scheduling maintenance. The historical data was used in design modifications and for determining the benefit of the design modifications.
The original shell liner design had a 15 degree face angle. With this design, the available power draw for new shell liners decreased by over 900 kW, restricting throughput for a period after installation of new liners. A simplified discrete element method (DEM) model was used to gain understanding of the control variables, such as mill speed and loading, in relation to physical parameters, such as lifter configuration, to find an optimized solution to the problem.
The DOE study developed a better understanding and contributed to the liner design modification to decrease the power drop with new shell liners with the installation of 25 degree face angle lifters. This design modification resulted in an improvement in power draw available and ore throughput in the plant.
Shell liner plate design, wear experience, and effect on liner life are discussed. The overall liner design process at Brunswick mine showed that:
With prudent modifications the amount of excess mass can be reduced.
Lifter height-to-spacing ratio significantly affects liner and lifter wear.
A wear profile program is essential to maximize liner life and reduce scrap loss.
Reduction from three to two shell liners per row decreased the liner change-out time.
Shell liner face angle design has a highly significant impact on the operation of the SAG mill.