Aggregates Manager Digital Magazine
Issue link: http://read.dmtmag.com/i/772143
AGGREGATES MANAGER / January 2017 27 tion is the movement of the rock," adds Johan Sjoberg, technical specialist in site automation. "Currently, there are a lot of yellow machines that move rock around and stockpile it." One particular problem is the use of large rigid-frame or articulated dump trucks to move aggregates from Point A to Point B for processing. Sometimes, the processing path is not straightforward, involving intermediate staging areas (and cost) to the overall operation. Then there's the human element. If production is foremost, truck operators may feel encouraged to speed back to the loading point, only to end up back in a queue behind other trucks, a situation that results in both additional idling and tire wear. Using today's machines to address these problems presents limited solu- tions, says Sunesson. Examining the entire site instead gave the research participants the opportunity to identify which activities add value, and which could be eliminated. "The aggregates business is a local business," Sunesson adds. "Our products are not competing on a global market, and it's very comfortable for us as quar- ry owners to use the haulers because we don't need any detailed planning to use them." Since the large haulers usual- ly have capacities above 50 tons, it makes it harder for quarry operators to incrementally increase or decrease their capacity, Sunesson says. "Often, you just want an additional 20 percent capacity, but when you add a new haul truck, you almost double your costs, which makes us sensitive to unplanned downtime," he says. Changing work place Electrifying a quarry could create a big leap in this industry, Sunesson says. "One challenge is that, in a quarry, the work place changes all the time. "Every time we blast, we move the face further away, and we create more space," he says. The resulting rock can be ap- proached one of two ways: either it can be moved to the crusher, or a mobile crusher can be moved to the rock. The Skanska quarry runs two shifts, which creates additional challenges to automation. In the morning, crushed rock is typically loaded by an excavator into rigid-frame dump trucks. In the afternoon shift, the morning operation continues, but additional rock is stock- piled, ensuring that aggregates are both ready to be loaded the next day and that there is a buffer against unplanned stops. "But this means that we're letting the material down twice and stockpiling it with a wheel loader," Sunesson says. "From a site perspective, that's a lot of waste." So, how to electrify a quarry? Flexibility had to remain key in whatever solution was devised, Volvo's Sjoberg says. Quarries change not only from day to day, but from shift to shift, which is one reason why diesel-powered ma- chines remain popular, since operators don't have to plan their daily path. One possibility was to have elec- tric-powered machines mimic diesel powered units. This strategy works fi ne for machines that don't move around much, such as the mobile crusher and Because of their high maneuverability, wheel loaders used in the Electric Site would be hybrid units.