Coal Age Magazine - For more than 100 years, Coal Age has been the magazine that readers can trust for guidance and insight on this important industry.
Issue link: https://coal.epubxp.com/i/1066352
December 2018 www.coalage.com 25 blasting continued derstanding of blasting caps is not un- derstood. Two cases are commonly seen from mines using these new caps, the first is that of a mine that purchases the caps and assigns the same design tim- ing as the previously used nonelectric caps. This mine is relying on the reduc- tion in cap scatter to better their blasts, which in many cases has the opposite effect. For example, when trying to op- timize ground vibrations, some mines will switch to an electronic cap because they have been told the reduction in cap scatter will reduce ground vibration. The shot is then loaded. The caps are pro- grammed for the same timing sequence as previous blasts and the ground vibra- tion is double or triple what is found on previous blasts. No, the geology has not changed from one blast to another — what has happened is that for holes on the same delay, the cap scatter or inac- curacy of the nonelectric caps had holes firing at different points in time, which led to less vibration. The second case is the mine that purchased the electronic detonators and, because they have the ability to be programmed to shoot very fast, are pro- grammed to shoot very fast. This func- tions off outdated theories that shock breakage is a major breakage mechanism and that extremely fast shooting, row to row, will lead to better fragmentation or better throw. They then find that rocks You Never Have To Settle For "Close Enough" With 4 major product lines, thousands of screen panel design options, and a range of specialized material compounds in polyurethane and rubber, we off er more screening solutions than anybody else. So we can hit your product spec. every time. Guaranteed! Combined with the fastest turnaround on non-stock orders and our industry-leading service and support, Polydeck is Your Trusted Screening Resource. 1790 Dewberry Rd., Spartanburg, SC 29307 Phone: 1 (864) 579-4594 / Fax: 1 (864) 579-4173 www.polydeckscreen.com Figure 7—Extremely poor, violent blast due to too fast row timing with substantial waste of energy.