Screening inefficiencies at a wet iron ore plant in Sierra Leone were resolved by redesigning a poorly performing transfer chute to deliver evenly distributed, lower velocity feed across twin screens, says  dry bulk materials handling specialist Weba Chute Systems.

Weba Chute Systems technical director Dewald Tintinger explains that the mine was experiencing screening inefficiencies that were undermining overall plant performance and that the problems were traced back to poor chute design.

“Material was not being fed optimally onto the centre of the screens, causing around 80% of the material to run to one side of the two screens at extremely high velocities,” Tintinger explains. “Under these poor screening conditions wet sluggish material flooded the conveyor belt, resulting in excessive spillage and frequent plant downtime for cleaning.”

Tintinger notes that while the application involved wet material, the fundamental challenge was familiar, stating: “Whether chutes are designed for dry material or slurry, the core issue is understanding material flow behaviour.”

The company employed discrete element modelling, or DME, which enabled a detailed assessment of screen loading profiles and material distribution, allowing for the visualisation of impact points, velocities and flow patterns across the screen decks before finalising the chute geometry.

The final design incorporated key engineering features aimed at delivering an even controlled feed at significantly lower velocities. This included ensuring that both screens received the same mass flow as well as the introduction of additional diverter gates and a flood box positioned above each screen.

In addition, Weba Chute Systems highlights its collaboration with the screen original-equipment manufacturer, Sandvik Rock Processing, and the mine’s plant team to diagnose the problem and develop a coordinated solution.

“It was a detailed and constructive process with all three parties contributing experience and critical thinking,” Tintinger explains.

Another aspect of the project was the customer’s requirement to fabricate key chute components locally in Sierra Leone to meet a tight schedule. Weba Chute Systems says that, in order to meet this stipulation, it enabled on-site manufacturing in line with its design specifications while also providing quality control oversight, installation assistance and commissioning support.