Engineering & Mining Journal

APR 2018

Engineering and Mining Journal - Whether the market is copper, gold, nickel, iron ore, lead/zinc, PGM, diamonds or other commodities, E&MJ takes the lead in projecting trends, following development and reporting on the most efficient operating pr

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Page 51 of 91

BLASTING 50 E&MJ • APRIL 2018 marketplace is oiling ANFO to 3-3.5% in an effort to save cost with about a 40% loss of energy to the unknowing miner. Emulsions should also be tested for nitrate content and to determine its to- tal sensitivity. The sensitivity can be in- directly tested by using a density testing method, however, the nitrate content is more difficult to determine. Best practice is to retain samples of explosives used on each blast and send them to an indepen- dent testing company should problems occur on a shot. Output Testing After testing of the inputs, outputs need to be ranked in order of importance and monitored, then correlated to the initial testing phase. In part one of the program, the inputs are not being purposefully var- ied, but instead randomly changing and being monitored. In part two, design in- puts such as burden, spacing, stemming, subdrill, timing, etc. are being purpose- fully varied with data collected to deter- mine how the outputs are affected. The first major output is the fragmen- tation of the blast. This can now be mon- itored with the use of a drone, crusher camera, or mobile device and the use of a fragmentation software. These systems develop a full fragmentation curve based on the data that is input. While the en- tire curve can be used and optimized; however, this is typically looked at as the P10, P50, and the P80, which allows for optimization of size and consistency of the material. The issue with using one of these instead of the three in optimization is that imagine a P50 of 24 in. is de- sired. This can be achieved with either all the material being 24 in. or close to 24 in. or 50% of 47-in. material and 50% of 1-in. material. Another method that can be employed if fragmentation systems are not available on-site is the boulder count, in which the operator of the loader will count how many boulders are found through the blast and the general location of those boulders. Another important characteristic is the muck pile configuration. Properly placed material will maximize fill fac- tors of the shovel/loader while maintain- ing ore position. One method to test this through the use of 3-D drone profiling of the muck pile. However, this develops a subjective view of the muck pile based on what the engineer or supervisor deems to be the best configuration. A less subjec- tive method is to employee systems like shovel cameras and monitor shovel per- formance and fill factors directly from the shovel to determine what optimal muck pile characteristics are and combine this with the muck pile 3-D profile. Through these systems, the fragmen- tation and muck pile orientation can be assessed to link to either the human and drilling errors or to the variables being optimized in the second stage of the six sigma process. It is always important to optimize one variable at a time through the blasting process and employee those knowledgeable in this area to determine what key variables are and how to best approach the optimization process. Conclusion The drilling and blasting program at a mine often receives little attention, even though it controls nearly every major func- tion and the ultimate success or failure of a site. Typically, mines are employing technology and methods in blasting pro- grams that date to the 1980s or earlier. In the meantime, systems like crushing, haulage, and processing have numerous innovation and are frequently targeted by capital expenditures; not considering that improvements in the blasting process could make much larger cost savings and production improvements to the site. The goal of Six Sigma Blasting is to develop a measuring system that can be used to analyze critical aspects of the drill and blast process. The first part of this is minimizing errors and inefficien- cies that are on-site and relating these to the blast performance. The second aspect of this is to then optimize the individual variables that are in the blasting process. It is important to understand that both of these processes assume that the blast design on-site is already reasonable and performing well. Through the use of Six Sigma Blast- ing mines can now begin to understand, improve and optimize their blasting programs with the use of 21 st centu- ry technology. Rules of thumb for blast design can now be replaced with engi- neered solutions that give optimal condi- tions for the rest of the mines activities and truly begin the mine-to-mill optimi- zation process. Calvin Konya is the founder of Precision Blasting Services (PBS) and Anthony Konya serves as project engineer for PBS. PBS is now offering continuing educa- tion online (see advertisement, p. 86). Figure 4—A device sitting on the bench tracks the borehole.

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