Engineering & Mining Journal

AUG 2017

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 39 of 99

BLASTING 38 E&MJ • AUGUST 2017 as the cut progresses, and ultimately the round progresses. Production Holes After all cut holes have fired, the produc- tion holes are the next to fire, and are considered to have a normal burden for the amount of explosives used. This is based on the burden used with respect to the production holes, and the change- over from cut holes to production holes is based on this burden. The normal burden for production holes can be calculated based on equation 4. Where: B = Burden (feet) SG e = Specific Gravity of Ex- plosive SG r = Specific Gravity of Rock d e = Diameter of Explosive (in.) Once the normal burden is reached, the production hole design can follow normal blasting practices for placement, design and timing. Modern Burn Cut Design Numerous arrangements of burn cuts ex- ist with the goal of optimizing either cost or face advance (production) in different room widths, rock types and explosive uses. Two different engineers have stud- ied various burn cuts and each tested more than 25 different burn cuts. The first one was Langfors, who studied burn rounds in more than a dozen rock types in Sweden with dozens of blasts in each for face advance of the round. The second was Bullock, who tested 29 different types of burn cuts over hundreds of blasts in the Missouri lead belt. Both authors came to the conclusion that the same pattern was the best one for maximizing face advance (shown in Figure 3). This round on average had a pull that achieved 92.3% of the to- tal face advance. This cut pattern is still used today at Doe Run lead mines. However, these were studied when dy- namite was the main explosive for under- ground blasting operations. Today, the use of ammonium nitrate-based explosives has changed the design process, introduc- ing a new problem that was not present with dynamite. The new ammonium ni- trate-based explosives (such as emulsions and even ANFO) can be dead-pressed, meaning they are densified from compres- sion of the borehole and their sensitivity reduced to the point that they will not initiate. They can also be precompressed, meaning they can be damaged and only release a fraction of the explosive's en- At GIW, our focus is on supporting you through the entire life cycle of your slurry systems. This includes working together to optimize your up time to increase productivity. How do we do this? We offer an entire business model under one roof. From research and design to aftermarket services we are your one stop shop for slurry pumps, cyclones and parts. This includes dedicated foundries for casting, machining and assembly and an on-site test facility to ensure optimal product performance. As the OEM, we offer services that others try to provide but can only copy. Whether you need mill discharge or cyclone feed pumps, new materials for your wear parts, or to upgrade your current slurry equipment to match your ever changing processing requirements, we have the answer. From concept to installation & beyond, your success is our priority GIW Industries, Inc. (A KSB Company) · R e s e a r c h & D e s i g n C o m m i s s i o n i n g S e r v i c e & R e p a i r O n - g o i n g S u p p o r t M a n u f a c t u r i n g E n g i n e e r i n g S t a r t u p T e s t i n g F u l l - s c a l e Figure 2 — Multiple layer burn round with burdens shown – MS delays used in first two layers and LP de- lays used in third and fourth layer for ease of loading.

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