Modern Mining March 2024

contaminated product or the need to stop the screen three to four times a day for a thorough cleaning. Each cleaning stops production completely for any where from 20 to 30 minutes. Depending on the severity of the blinding or pegging issue, if a chain is needed to vibrate the material off the screen, not only do producers need to figure in the cost of shut down, but also the cost of the added wear and potential damage to the screen media. If cleanings must occur four times a day, they result in upwards of two hours of lost production every week. With one ton of coal priced at approximately $30 and 250 tons processed an hour, that translates to $15 000 of lost production each week, or more than $60 000 per month. Over the course of an average year, a coal mine is effectively leaving in excess of $720 000 on the table. Alternative screen media offer a more efficient solution to overcoming the blinding and pegging issue. While traditional woven wire cloth relies solely on the vibration of the screen box to create the fre quency needed to stratify the material, high vibration screens are designed in a manner that allows each wire to vibrate independently, enhancing the overall effectiveness and allowing the screen to self-clean. The high frequency vibration produced by the screen wires virtually eliminates blinding and pegging and erases the need to prewash the coal or shutdown the machines for cleaning. In turn, eliminating that step can also reduce water use and costs leading to a more sustainable overall process. To further reduce the chance of material buildup, the high-vibration screens offer customizations using stainless steel wire. While the porous nature of stan dard wire might attract the coal powder, allowing it to build up and eventually close off the entire opening, the stainless-steel wire combined with high vibration effectively eliminates the chance of material buildup.

plethora of specification requirements. This provides coal mines with the capacity to meet specifications and capitalise on the products or specifications that provide the highest profit margins. 2. Blinding & pegging The lightweight and relatively soft properties of coal lead to the production of many fines that stick to the surface of the screen causing issues with blind ing. Though running the coal through a wash plant before screening may reduce the fines, the added moisture – even 5% – leads to equally troubling issues with blinding. Whether from the sticky fines or the moisture laden slime, blinding and pegging present a major problem to the quality and quantity of the final screened product. Left unchecked, blind ing and pegging lead to incomplete screening and

Predictive vibration analysis detects miniscule changes in baseline operation before the effects are seen in screening performance and output.

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March 2024  MODERN MINING  27