The AfriSam Umlaas Road Quarry has taken proactive measures to enhance the accuracy of its final product sizing by adopting Multotec’s rubber screen panels in its tertiary screening application. This strategic move has enabled the site to address and rectify the challenges that were previously experienced with the use of woven wire mesh screening media.

Situated in KwaZulu-Natal, South Africa, operations at the open-pit mine focus on exposing tillite by drilling and blasting techniques, with the blasted rock transported to the crushing plant. The material is processed through crushing and screening to produce aggregate, and the final products are then sold to the construction and road-building industries.

Challenges with existing woven wire mesh screening media

However, the biggest challenge that the quarry faced for some time was the sizing accuracy of its final product, along with the limitations of its woven wire mesh screening media. Used in the tertiary section of the plant, the mesh would be prone to pegging and blinding and needed to be changed out regularly. Pegging occurs when product particles, usually close to the cut size, get stuck in the woven wire mesh, while blinding refers to aperture holes becoming clogged up with fines.

These issues resulted in out-of-specification particles entering the underflow and overflow product stream. The mine’s customers are particular about the specific size of the final product and typically test particle size distributions. If any out-of-specification particles are detected, the product is generally returned to the mine. The frequent need to change the woven wire mesh screen resulted in significant maintenance and material costs, as new mesh had to be purchased and installed, which also added financial costs to the mine in the form of production downtime. Additionally, the frequent change out of the woven wire mesh screen resulted in increased health and safety risks.

Rubber panels provide a practical screening solution

In search of a solution to the issues it was experiencing with its tertiary screening media, the quarry approached Multotec and adopted its rubber panels solution. The panels are designed to absorb impact, reduce pegging and blinding, as well as improve wear life in coarse and heavy-duty mineral processing applications.

“The adoption of Multotec’s rubber screening panels has resulted in significant benefits for the mine, including increased screening efficiency, reduced maintenance requirements, and improved lifespan and durability,” says Lance du Plooy of AfriSam Umlaas Road Quarry.

“This has directly contributed to improved product sizing accuracy and a noticeable drop in downtime associated with screen replacements.”

Since the rubber panels are a modular system, only worn-out panels need to be replaced, unlike the complete change-out required for woven wire mesh if any section of the screen becomes damaged. Multotec’s rubber screen panels also include injection moulded weir bars, which are cascaded along the screening deck to help the flow of product and spread it out over the complete deck. This prevents the product stream from constantly falling onto one area of the screen when the product is fed from a conveyor belt.

The weir bars aid in directing the material flow across the entire screening area, which is not possible with woven wire mesh. While not initially included with the panels, weir bars can be incorporated into the system. This delivers benefits such as enhancing the flow of the product stream to cascade smoothly across the entire deck. This further ensures optimal product distribution and easy maintenance, resulting in better screening efficiency. Additionally, because the rubber panels are a modular system, each panel can be changed individually, in a matter of minutes.

“Quarries and quarry product streams are known to be dusty with a lot of fines,” explains Pieter Uys, Business Development Manager at Multotec Manufacturing.

“By changing over to the correct rubber composition for the specific application, the Umlaas Road Quarry was able to increase production, reduce pegging, blinding, and fines build-up significantly. The transition to rubber panels not only optimises the screening process but also improves workplace safety and operational uptime.”

Operational benefits and advantages
The introduction of the rubber panels yielded immediate results, and the quarry experienced an improvement in the efficiency of correct product sizing, significantly reducing pegging, blinding or fines built up on the rubber panels, resulting in more quantities of sellable product.

“This has allowed the mine to ‘map out its deck’, meaning, solid panels could be installed in the impact areas and different aperture panels in different areas of the screen deck to ensure screening efficiency,” says Uys.

Uys further adds that the mine has also seen a significant decrease in downtime as the rubber panels have a longer lifespan and can handle much more abrasion than woven wire mesh.

These two factors combined have led to an increase in production and productivity, while lowering the cost of maintenance and materials. An unexpected benefit was noise reduction, as rubber panels are softer than woven wire mesh. This is an important improvement as like many other quarries, the Umlaas Road Quarry is located near a residential area. Not only has this improved the relationship between the mine and its neighbours, it has also helped the quarry to adhere to the legal requirements around noise pollution.