Modern Quarrying Q1 2020

Eugene Preis, MD of ERG Industries.

through the drill hole. Typically, the loss of explosive energy through stemming ejection reduces the performance of the blast. The fundamental theory promoting the use of blast-improvement and containment plugs is that they could improve the effectiveness of stemming material in the blasthole. As a result, this would better contain the explosive energy within the rock mass and yield a more controlled and efficient blast. Enter Varistem Varistem is now available in Africa through ERG Industrial – excluding a few countries like Zimbabwe and Congo, due to US trade restrictions. The plugs is said to contain blast energy for longer, resulting in a range of benefits depending on how it is incorporated into the blast design. fragmentation and micro-fractures, with more tonnage processed at less cost. “Following ore body fractures created by the explosive shock waves, the Varistem improves expanding gas containment. The greater the gas containment time within the ore mass fractures, the better the fragmentation. Getting your fragmentation right is substantially cheaper than having to do secondary blasting or mechanical breakage,” he says. In some cases, Varistem has achieved up to a 25% increase in fragmentation, which in turn reduces crushing costs and increases crusher throughput. Independent studies also show that the Varistem can Preis says maximum blast containment means greater

Plugs work by creating an additional blocking effect within the drill hole when blast energy is released, directing more energy into the block and less energy upwards out of the drill hole.

KEY TAKEAWAYS

ERG Industrial secured the distribution rights for the Varistem stemming plug range from United States company, MOCAP in June 2019

Independent studies show that the Varistem can increase blast pattern spread by 10% or more, with the same fragmentation for major savings in drilling and explosive costs (between 11–12% reduction in direct costs achieved during recent trials)

Air-decking with the Varistem allows shorter stemming heights, while also reducing the explosives column height, to dramatically minimise over-sized cap rock from a common 10% oversize, down to a 2% oversize

There are several secondary cost savings which result from increased fragmentation – easier rock removal, less secondary breakage costs, increased truck capacity, less wear on crushing and grinding equipment

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QUARTER 1 - 2020 MODERN QUARRYING