One of the main objectives of the comminution process is to maximise throughput. With tonnages increasing, mines are looking at ways to increase circuit capacity at the lowest possible cost. General Kinematics’ SMT-SCREEN vibrating screen – supplied locally by IMS Engineering, South Africa’s leading comminution equipment supplier – can replace a brute force screen and provide up to a 40% increase in circuit capacity.
Etienne Swanapoel – National Sales Manager at IMS Engineering, explains that the STM-SCREEN is designed to fit within the existing space and rest on the existing screen footings, without overhauling existing support structures. “The STM-SCREEN should not require modifications to the existing structure because sub resonant, Two-Mass vibrating screens have far lower dynamic forces than equivalent size brute force screens,” he says.
Standard single deck and double deck machine sizes range from 1,4 to 5,4 m wide and 10 m long. All can be modified to mount on an existing screen footing. Purpose-built machines can be of any size required to replace an existing machine and feature hybrid decks and triple-deck configurations.
The large model STM-SCREEN, greater than 2,4 m wide, can be designed in a modular fashion so it can be dismantled in sections after test runs in the factory, shipped to distant locations and then reassembled at the mine site.
These Two-Mass vibrating screens are modifiable to accommodate higher tonnages and deeper material bed depths. Masses can be made heavier; motor HP increased and more springs added to the spring network to ensure that material is consistently stratified along the length of the screening surface at the constant design stroke amplitude.
“Machine stroke is maintained under full load to sustain designed material stratification and screen efficiency, whereas the stroke of brute force screens is dampened as the material load is increased and screening efficiency is negatively affected.
The STM-SCREEN typically retains material three to four times higher than the brute force screens in order to achieve higher screening efficiency. “Brute force screens accelerate material to thin the bed depth, limit material weight on the screen and retain the material for only 8-12 seconds,” explains Swanepoel.
For wet screening applications, the STM-SCREEN has significant de-watering advantages. Typically, the water spray is limited to the first two-thirds of the screen length, leaving just the final third for de-watering. “With greater material retention time on the STM-SCREEN, there is a corresponding increase in de-watering, allowing more excess water to be removed,” concludes Swanepoel.