Conveyor system technology evolves to meet the changing bulk materials handling needs of the industry
Conveyors have been a part of global industrial activity for more than a century, and their use in various mining applications has grown exponentially over roughly the same time frame. Driven by a bedrock economic mandate to move more material at a faster rate—and preferably at steadily lower cost per ton—the global mining industry has leaned heavily on bulk materials handling technology to meet its production and product-delivery targets. Conveyor-system vendors have, in turn, implemented the latest advances in automation, power transmission and real-time condition monitoring to provide increasingly capable, powerful and flexible systems.
State-of-the-art belt conveyors can accommodate long distances, steep gradients and tight curves, allowing precise matching of performance to the particular task and topography. Many system suppliers, such as Beumer Group, offer both open troughed configurations for high throughput, and enclosed ‘pipe’ belts for products that need protection from environmental factors. (Photo courtesy of Beumer Group)
The growing sophistication of conveyor control systems and variable speed drives offers improved fine-tuning of startup sequences and operational speeds, allowing mines to more closely match belt throughput to upstream conditions and processes, while saving energy and reducing unnecessary mechanical wear. The ability to adjust conveyor performance to meet evolving requirements as a mine passes through its startup phase to maturity, without need of major system upgrades or modifications—and while cutting maintenance costs and extending component service life—offers a powerful incentive for increased industry investment in new, large-scale conveyor technology. And, based on examples described below involving two major producers—Vale and Codelco—that incentive appears to be effective.
Industry suppliers are also steadily introducing new, more specialized bulk handling products that give mine operators a wider range of options to meet site-specific chall
enges. These range from pipe conveyors that can eliminate dust and spillage, to high-angle belt or bucket systems. At the end of the conveyor run, new self-powered and highly maneuverable feeders and conveyor units provide increased mobility and flexibility in stockpile and loading applications at lower capital costs when compared with traditional stationary equipment.
Trading Trucks for Belts
Vale, the world’s largest iron ore producer, announced in early July that it had obtained the installation environmental license for its S11D iron ore development project in the Carajás region of Brazil. Following issuance of the license, Vale’s board of directors approved full development of the S11D project. The project has a nominal capacity of 90 million metric tons per year (mt/y) of iron ore and is the largest mine development project in Vale’s history.
According to the company, a conventional truck/shovel mining operation of this size would require roughly 100 haulage trucks. Instead, by using a “truckless” approach that employs in-pit crushing and conveying, Vale said it will reduce both its diesel fuel consumption and its annual CO2 emissions from the operation by 77%.
The use of a conveyor system allows the processing plant to be built on pasture land outside the forest where the mine is located, reducing the operation’s deforestation impact.
A worker checks rolls of conveyor belting onsite at Vale’s S11D iron ore project in Brazil. The mine, which ranks as the largest mine development project in the company’s history, will use 37 km of belting in a large-scale IPCC mining operation. (Photo courtesy of Vale)
Vale awarded SKM a $74-million implementation contract for engineering the in-pit crushing and conveying (IPCC) system at S11D. In all, 37 km of conveyor belts will be installed within the mining area, including branches that will connect to the main trunk line feeding the processing plant. The maximum distance between the ore collection point and plant will be 15 km. The system will use shovels to feed mobile crushers that will in turn feed the belts. The mine’s primary equipment will be powered exclusively by electricity. Only crawler tractors, motor graders and other auxiliary machines will run on diesel.
The site challenges are enormous: Inside the pit, 2,000-mt mobile mining machines and 2-km-long conveyors will be moving with and around each other, while also working around the drilling, blasting and mining operations. When installed, the system’s transfer conveyors will run through rugged terrain, dropping 400 m in elevation from the pit to the dumps over a distance of 4 km while carrying 9,000 mt/h—a volume that SKM equates to having two family-size sedans dropping off the terminal point of the belts every second.
Going Gearless at El Teniente
Earlier this year, Chilean state-owned copper producer Codelco announced that it planned to spend more than $5 billion in capital expenditures during 2013, up from almost $4.2 billion in 2012. Approximately $2.29 billion of the 2013 total will go toward three major development projects: $1.155 billion for the new Ministro Hales mine, $716 million for new mine level development at El Teniente, and $417 million for the Chuquicamata underground project.
At the El Teniente expansion project, work on a new mine level during 2013 will focus on mine development and excavation of the two primary access tunnels—one for use by employee transport buses and the other for the ore conveyor belt, a service track, and an alternative emergency exit.
The new level is scheduled to produce 137,000 mt/d of ore and 430,000 mt/y of fine copper, maintaining existing capacity at the mine. An option remains open for later expansion to 180,000 mt/d. The project will extend mine life at El Teniente by 50 years following startup in 2017.
Tunneling equipment is in place at Codelco’s El Teniente mine for construction of an almost 9,000-m long conveyor path leading to the existing mill (right). In its final stage, the system will transport crushed ore at more than 12,000 mt/h, running at 6 m/sec.
Codelco awarded a contract for an essential part of the expansion project—a large-scale conveyor system to connect the new orebody to the processing facilities—to Tenova Mining & Minerals TAKRAF unit. In its final stage, the system will transport primary crushed copper ore at more than 12,000 mt/h. Running at 6 m/sec, the 2-m-wide belt conveyor system will carry ore almost 12 km to the plant. Three principal conveyors—one 9,000-m-long tunnel conveyor and two 1,000-m-long inclined conveyors—will feed the existing stockpile and in the future, a new stockpile.
TAKRAF said that, with an eye on current and future energy costs, Codelco determined that drive efficiency and conveyor running resistance were increasingly important system characteristics, and consequently selected gearless drives with high-efficiency variable speed control for the conveyor system. The gearless approach will allow the El Teniente operations to initially run the conveyor system at slower speeds to suit the lower conveying demands in the earlier years of production, thus saving power, reducing wear and providing additional savings in maintenance costs.
Controlled application of fluid coupling torque provides a smooth start-up to protect conveyor belts from stress damage, according to Voith Turbo. Shown here is a version of Voith’s TVVS fluid couplings; the company recently delivered 36 of these couplings for installation in an offshore iron ore distribution terminal in Malaysia.
Although gearless or direct drives are a proven technology that has been used in mills and hoists for years, it is a relatively new approach in conveyor design. TAKRAF, in partnership with ABB, said it has integrated features within gearless drive systems aimed at reducing maintenance work in the field to a minimum, allowing a faulty drive to be quickly removed and replaced, and then repaired in the shop, and allowing easy alignment once installed. Gearless drive units can transmit strong and sometime damaging force to conveyor components—a condition that has caused problems with pulleys in the past. However, TAKRAF maintains that the system design eliminates this risk and allows the use of standard pulleys throughout the system.
TAKRAF pointed out that the long tunnel conveyor is designed to minimize running resistance by ensuring accurate alignment through the use of special conveyor frames and low-resistance rubber compound for the belt. The two steep inclined conveyors, which in their final stage will both be equipped with four 2,500-kW drives, also presented some challenges involving maintenance of idler rolls along the conveyor run, most of which is enclosed in tunnels. TAKRAF developed a unique system to service these steep conveyors.
Manual handling of conveyor rolls, which can weight 45 kg or more, is difficult and carries a high risk of injury for maintenance personnel. The El Teniente system will employ a special maintenance cart equipped with a small service crane, which will run on rails along the entire conveyor length and straddle the belt. The crane is fitted with lifting frames, allowing the maintenance workers to guide the roll while its weight is handled by the crane. The cart can carry spare rolls, all required tools and up to four people.
The ABB drive system is designed to feed power back into the grid during electrical braking and regenerative operation. Beginning in the third quarter of 2013, ABB will deliver electrical equipment and new gearless drive technology (with 12, 2,500-kW/56 rpm motors) for the complete conveyor system. ABB will also provide E-houses with pre-installed equipment, air conditioning and liquid cooling for the ACS6000 drives and synchronous motors, along with its MCCP mining conveyor control program for main drive control and load sharing, and its 800xA Extended Automation System.
From Ship to Shore
Germany-based Beumer Maschinenfabrik noted that its curved belt conveyors are available in open troughed belt-conveyor configurations for higher throughputs and larger mass flows as well as larger curve radii, and in enclosed pipe conveyors for products that need protection from environmental factors.
Beumer said it is currently installing several pipe conveyors with a total length of about 3 km for transporting copper, lead and zinc concentrates at the port of Callao in Peru, scheduled for completion in 2014. In Malaysia, Beumer is equipping Vale’s new off-shore distribution center with 17 troughed belt conveyors with a total length of 12 km. The conveyors will transfer iron ore from super-size freighters to shore.
Samson Materials Handling’s new track-mounted MF0814T Material Feeder is self-propelled and operates via an integrated diesel power supply. The series is designed for heavy-duty applications involving continuous use.
Voith Turbo, a division of Voith GmbH, recently delivered 36 hydrodynamic fluid couplings to Beumer for the Malaysian project, where the couplings will be used in drives rated at 200 to 800 kW. The TVVS-type couplings supplied to Beumer, according to Voith, feature special TVVS designs to match the start-up and operating conditions of the drives.
Voith said the TVVS constant-filled fluid coupling is particularly suited for medium to long belt conveyors. Because of the mechanical separation of the motor and machine through the fluid coupling, the motor can run up to speed without load. The application of fluid coupling torque provides a smooth start-up to protect the belt from stress damage.
In addition, systems that use multiple motors can be switched on in a staggered sequence to limit the current demanded during the motor acceleration. This avoids grid overloading caused by simultaneous motor starts. In the most demanding belt conveyors, TVVS couplings are fitted with centrifugal force valves to further protect the electric grid; these valves control the filling and draining of the coupling working circuit, and thus the power transmission, as a function of the drive speed. The motor starts up virtually load-free, even in the event of voltage drops. The coupling torque is applied continuously and without shocks up to the required breakaway torque of the system.
The TVVS couplings can use water as the operating medium, if necessary. This environmentally friendly feature, said Voith, is particularly well-suited for use in the conveyors that transport iron ore over the ocean’s surface.
On Track for Heavy-duty Loading
Samson Materials Handling, now a part of the Germany-based Aumund Group, has introduced the latest variation of the Samson Material Feeder—the track-mounted MF0814T series. The company said the feeder’s concept was developed to serve the needs of mining customers who require a holding capacity of up to 50 tons combined with operational durability and accurate discharge control.
The series is designed for heavy-duty applications involving continuous use, including high-impact loading from articulated dump trucks and large loading shovels. Suitable for materials with bulk density up to 2.6 t/m3 and lump sizes up to 400 mm, typical materials would include limestone, coal and coke, raw slag, alternative fuels, clays and shale, and heavy ore types.
The MF0814T is self-propelled and operates via an integrated diesel power supply. With steering controlled through an umbilical control, the unit can be deployed quickly and independently, according to the company.
Another division of Aumond Group—Aumund Fördertechnik—announced in 2012 that it intended to focus more intently on the mining sector, and recently touted its new BW-L Twin-Chain bucket elevators as a product that can be well-suited for specific, customized mining applications.
Aumund offers five different chain sizes with bucket separations of 305 mm and 457 mm. The system, fitted with five-segment sprockets, comprises a chain with a small roller, a bulk material guide at the backs of the buckets, a toothed drive ring, a non-toothed tensioning ring and bucket connector plates. The bucket elevators are designed for speeds of 0.5 to 0.7 m/s and for a conveying capacity of 142 to 726 m3/h.
ContiTech’s Conveyor Belt Group displayed its new MegaPipe conveyor line at the bauma 2013 trade show held earlier this year in Munich, Germany. With an external diameter of up to 900 mm, the new MegaPipe line has double the capacity available from conventional closed-trough belts, according to the company. Its design permits the inclination angle of a closed-trough belt system to be increased by up to 45°, depending on the bulk material properties.
The group also showcased its Flexowell product line and Pocketlift steep-angle conveyor system, described as the only continuous conveyor systems available for lift heights of up to 700 m and capacities of up to 5,000 t/h. After acquiring the Flexowell and Pocketlift lines from Metso in 2010, ContiTech announced in September it had also acquired Metso’s industrial conveyor belt operations based in Helsinki, Finland. The transaction scope includes a production plant in Kalkku, Finland, where ContiTech will manufacture conveyor belts for mining as well as other industrial applications.
Radial Units for Remote Sites
Many mining projects lack adequate infrastructure to efficiently move the mined commodity from pit to terminal or port. As a consequence, according to Telestack, a U.K.-based supplier of mobile conveyor and feeder systems, mine operators often have to invest in costly infrastructure to facilitate transfer, loading and shipping.
Telestack said it has designed, manufactured and installed a variety of self-powered mobile conveyors and hopper/feeders that enable producers to stack and reclaim material at the mine; load it onto a rail car or truck for transfer to the port; unload, stack and reclaim it at the port; and finally, load a barge or ship.
A Telestack mobile radial conveyor at work in a stockpile operation.
The company exhibited its mobile radial telescopic conveyors at bauma Africa 2013, held September 18-21 in Johannesburg, South Africa. Telestack representatives said it has a number of these units already working in Africa, used for stockpiling/reclaiming at a pit or port and loading vessels at river terminals and sea ports. Vessels loaded range from barges up to baby cape-size ships, and stockpile capacities can be as high as 400,000 tons of ore with a standard system and even higher for customized applications, according to the company.
Telestack said its Rapid Deployment Solutions are currently handling a wide variety of materials from heavy ores, to coal to biomass, with transport rates of up to 3,500 tph, often in extreme conditions.
The product line’s mobile capabilities provide a less expensive alternative to mobile harbor cranes or stationary systems, said Telestack, and require significantly less civil engineering and infrastructure costs. The machines are designed for continuous loading operations, and can run on diesel hydraulic, power, diesel electric power via onboard generators, or from on-site power sources. Being self-powered, they can move around the mine or port unassisted, eliminating the need for other equipment to move them, and are claimed to be capable of easily linking into existing material handling systems.