Weba Chute systems solves wet plant screening inefficiencies at Sierra Leone Iron Ore mine

Weba Chute Systems, globally recognised for its expertise in dry bulk materials handling, has once again demonstrated the versatility of its engineering capability by resolving complex transfer point challenges in the wet plant of an iron ore mine in Sierra Leone.

The mine had been battling persistent screening inefficiencies that were significantly affecting plant performance. According to Dewald Tintinger, Technical Director at Weba Chute Systems, the root cause was traced back to poor chute design rather than screen performance.

“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.”

Because of this uneven loading, only a limited portion of the available screening area was being used effectively. The bias loading combined with excessive material velocity significantly reduced separation efficiency and overall throughput. While the application involved wet material, Tintinger notes that the underlying principles remain consistent across different material types.

“Whether chutes are designed for dry material or slurry, the core issue is understanding material flow behaviour,” he says. “Our scientific understanding of material flow, combined with years of practical experience, was critical in identifying a suitable solution. The presence of water, however, added complexity when predicting exact flow behaviour within the constraints of the existing transfer layout.”

To remove uncertainty and refine the design concept, Weba Chute Systems employed Discrete Element Modelling (DEM). This advanced simulation technology enabled engineers to analyse screen loading profiles, material distribution, impact points and flow velocities before finalising the chute geometry. By visualising how the material would behave across the screen decks, the team was able to optimise the design with precision.

The final chute redesign incorporated several critical engineering features to deliver a controlled, evenly distributed feed at significantly lower velocities. A key requirement was ensuring equal mass flow to both screens. Due to the rotational dynamics of the mill feeding the circuit, discharge was naturally biased, producing a 60/40 split between the screens.

To correct this imbalance, Weba Chute Systems introduced a manually adjustable valve, allowing operators to fine-tune the split to an even 50/50 distribution. The valve also provides operational flexibility by enabling 100% of the feed to be diverted to either screen during maintenance, supporting improved plant availability and uptime.

Further innovation came in the form of additional diverter gates and the installation of a flood box above each screen. This configuration allows slurry and water to accumulate before overflowing evenly across the full width of the screen decks. Instead of striking the screens in a concentrated, high-energy stream, the material now spreads uniformly.

“This ensured not only even distribution across the screens but also a substantially lower discharge velocity,” Tintinger says. “The reduced velocity increases screening time which directly contributes to improved screening efficiency.”

Collaboration was a defining element of the project’s success. Weba Chute Systems worked closely with screen OEM Sandvik Rock Processing and the mine’s plant team to diagnose the issue and implement a coordinated solution.

“It was a detailed and constructive process with all three parties contributing experience and critical thinking,” Tintinger explains. “Each of us made targeted changes within our respective areas ensuring that the chute redesign, operating practices and screening configuration were aligned to the same performance objective.”

Another significant aspect of the project was the customer’s requirement to fabricate key chute components locally in Sierra Leone to meet tight scheduling constraints. Weba Chute Systems supported this approach by enabling on-site manufacturing in accordance with its engineering specifications, while also providing quality control oversight, installation guidance and commissioning support.

“This hands-on approach reflects our philosophy of taking responsibility for outcomes not just designs,” Tintinger says. “A solution only truly succeeds once it has been implemented and proven under stable operating conditions.”

As with all its projects, Weba Chute Systems began the process with a physical site visit to the remote operation. Observing plant conditions firsthand allowed the engineering team to fully understand the factors influencing chute performance and to develop a solution tailored to the realities of the operating environment.

By combining scientific material flow analysis, advanced DEM modelling and practical field experience, Weba Chute Systems has delivered a measurable improvement in wet plant screening efficiency.