The fact that screening can be a bottleneck in aggregate production is no exaggeration. Cases of quarries operating with high rates of poor product-sizing accuracy and contamination of materials in their screens are not uncommon, as are stoppages and costs related to frequent changes of screening media. According to Pieter Uys, business development manager at Multotec, these challenges are in most cases due to the fact that operations are using the wrong screening media in the incorrect applications.
Uys stresses that there is a place in the market for every type of screening media, but it is important to carefully consider the key variables that should influence the choice of screening media for the application at hand. With so many elements that can influence effectiveness, quarry operators, working closely with their solutions providers, should carefully deliberate on the best choice for their operation.
A case in point is a KwaZulu-Natal-based quarry which, in close collaboration with Multotec, successfully replaced woven wire mesh screening media with Multotec’s rubber screen panels. The switch was aimed at addressing several challenges experienced with the use of woven wire mesh screening media in the quarry’s tertiary screening area.
The challenge
The main challenges for the quarry were the sizing accuracy of the final product and the frequent need to change the woven wire mesh screening media in the plant’s tertiary section. The woven wire mesh, explains Uys, was prone to pegging and blinding, leading to out-of-specification particles entering the product stream. Pegging occurs when particles get stuck in the mesh, while blinding is as a result of aperture holes becoming clogged with fines.
“Given that it is a tertiary screening application, there were bound to be fines in the product stream, which led to pegging and blinding, which in turn negatively affected the efficiency of the screening process,” explains Uys. “The pegging and blinding challenge also led to product inconsistency, which was a major setback for the client, especially considering that quarries by their nature have to adhere to strict product specifications. With blinded screening media, there are more fines carrying over and it also means that particles that were supposed to report to the undersize now report to the oversize, thus negatively affecting the screening efficiency.”
In addition, the quarrying company also struggled with the short lifespan of the woven wire mesh in this application. Apart from the obvious cost implications, frequent mesh changes also resulted in unnecessary maintenance downtime. Given the bulky nature of woven wire mesh, the deck replacement process was labour-intensive and posed a significant safety risk.
The solution
After careful evaluation of the challenges at hand, a Multotec sales engineer found that the customer would be better served by Multotec rubber panels, designed to absorb impact, reduce pegging and blinding, as well as to improve wear life in coarse and heavy duty applications.
“Available in a wide range of apertures for various applications, Multotec’s rubber screening panels are ideal for applications with high impact areas and abrasion. Our rubber panels are highly impact-resistant and have a long lifespan, thus ensuring optimal total cost of ownership for the customer,” says Uys.
In addition, the modular nature and fastening systems of the Multotec rubber panels allow for the replacement of only worn-out panels, instead of a complete change-out of the entire deck required for woven wire mesh. The replacement of a selected number of panels is quick and easy, which eliminates unnecessary downtime and the need for several personnel to change the mesh. This in turn also reduces the safety risk related to mesh changes.
In this specific case Multotec also supplied panels that include injection-moulded weir bars that regulate product flow across the entire deck, enhancing screening efficiency. “We also supplied the client with a specific rubber that is soft enough to avoid pegging and blinding. With these particular rubber panels, the screening area stays open and clean, which results in effective and efficient screening,” explains Uys.
The result
The immediate results of going the Multotec rubber panels route were significant. These included improved product sizing, reduced pegging and blinding and improved production of more sellable material.
“One of the major outcomes is that the sizing is much more accurate. Additionally, the rubber panels’ longer lifespan and greater abrasion resistance have resulted in reduced downtime and maintenance costs,” says Uys.
Another added benefit is that the quarry can now ‘map out its deck’ with solid panels in impact areas and different aperture panels elsewhere, ensuring efficient screening. “An unexpected benefit was the reduction of noise, which has improved the relationship with nearby communities and helps the quarry adhere to noise pollution regulations,” concludes Uys.
