The company spent two years developing its MVT (matched velocity technology) Sizer and last year started testing a prototype. By the middle of this year nearly a dozen of the machines had been sold. Primary, second and tertiary sizers capable of handling feed sizes as large as 1500mm and outputting product as small as 25mm were designed in Australia using the latest 3D parametric modelling and finite element analysis systems.

According to OSA manager, crushing projects, Gary Everson, this produced machines that are robust, reliable and maintenance-friendly. “The sizer can be fitted with wheels to allow roll-out for maintenance,” he said. “Almost all maintenance is carried out from the top and rolls can be removed without disturbing the main frame.

“A range of roll configurations are available, with innovative materials to enhance the life of wear tips, provide good top size control and maintain consistent product size over time.”

OSA has a worldwide patent pending on the MVT design, conceived as a way of minimising fines generation in coal processing applications. Everson said extensive tests carried out by Queensland's Julius Kruttschnitt Mineral Research Centre on behalf of the manufacturer had shown matching roll speed to the velocity of particles entering the sizer could reduce fines by 200% or more. This in turn reduced dust levels and the moisture content of saleable coal, and favourably impacted washery costs.

The throughput range of the MVT Sizer machines is 100-10,000 tonnes per hour, making them suitable for the full range of coal preparation duties.

OSA has also conducted successful trials with the sizer on limestone and nickel ores. Everson said the company believed there was a market for the machine range in the hard-rock mining sector.

About 20% of machines sold to date have been exported - principally to the US market - and Everson said he was confident of growing the export business. China, South Africa and Europe were among other high-potential overseas markets.