May 2014

Going places

New conveyor designs stand out in a traditional field

By Eavan Moore

When miners look to assemble a conveyor system, the majority tend to stick with the tried and true. For projects that need to move major tonnages, conveyor systems are being pushed to new dimensions, getting bigger and more powerful. But for operations cursed with steep and demanding terrain, and for miners seeking more efficient transportation, some new design developments could challenge traditional systems.

When it comes to satisfying his customers’ top needs, Derek Lawrence, sales manager of B.I.D. Bulk Material Handling Systems, says modern belt conveyor technology is most in demand. “A lot of times, their primary concerns are capital cost and delivery. Since they’ve proven reliable, conventional systems are often chosen,” says Lawrence.

In the last 20 years, information technology has had an enormous influence on basic conveyor system design, according to Steve Davis, technical director for materials handling at Worley Parsons Canada. Computing power and modelling software, and a better understanding of material properties has allowed engineers, for instance, to design more precise, lighter weight, cost-effective conveyor systems for higher capacities. These same advances have also provided designs that better handle practical problems like controlling material flow onto belts or minimizing dust creation and material spillage.

“Transfer chutes have improved phenomenally in the last 20 years,” explains Davis. “Our ability to manage material and airflow in chutes, along with improved wear resistance and belt cleaning, and better skirt systems allows us to have a series of conveyors in line and be able to more or less guarantee that the transfer between those conveyors is going to work out 100 per cent of the time.”

Heavyweight belts

More recently, the mining megaprojects under development have been catalysts for new capabilities in conveyor components. Higher production levels and higher waste-to-ore ratios put more demands on conveyor systems, says Patrick Dronsky, manager of the material handling department at AMEC. A conveyor at one of the biggest mines under development might move 20,000 tonnes per hour. That has driven the adoption of more powerful drives, stronger belts and bigger overall systems.

Gearless conveyor drives become economically competitive with conventional conveyor drives (with gearboxes) at about 2.5 megawatts (MW). A few large South American mines have ordered gearless drives for their new conveyor systems. Glencore installed two 3.8-MW Siemens gearless drives on a 6.5-kilometre conveyor at its Antapaccay copper mine in Peru. Conventional drives could do the same job, but generally with higher cost and more maintenance requirements. By eliminating the gearbox and connecting a synchronous motor directly to the drive pulley, gearless drives add efficiency.

Drives don’t do all the heavy lifting: as systems ramp up capacity, the belt needs to be stronger, too. Davis says companies like ContiTech and Veyance have developed belts with strength ratings of ST10,000. At that strength, one belt could potentially handle a load that might previously have required three separate flights of lower strength belts. “This is significant because each transfer and drive costs money to install and to operate, so if one long belt can be used instead of three shorter belts in a line, money will be saved all around,” explains Davis. Until a few years ago, the strongest belt available was rated and proven at ST7,800.

While the larger conveyors address the question of capacity, they run up against traditional limitations. For instance, even the biggest conveyor belts cannot carry run-of-mine sizing of a metre or more. That could be a problem if more mines turn to in-pit conveying, as Davis suspects they will. Conveyors also require cleared land along their route and only moderately steep slopes. Providing solutions to these niches though could be accomplished by a couple of new designs that break the mould.

Rail-Veyor: rethinking the mine

Rail-Veyor represents a fundamentally different option for bulk material handling. It is an all-electric troughed light rail system that integrates with, or replaces, trucks and conveyors with a continuous haulage system. Rail-Veyor can handle development debris or run-of-mine ore, emits no diesel particulates and has less rolling resistance than electric conveyor systems. According to Pat Fantin, vice-president, technical, the system’s operating costs are 20 per cent lower than conveyers and it also has fewer wearable moving parts.

The system can transport larger lump unsized ore and it also addresses the problems associated with transfer points. “Once the Rail-Veyor system is loaded, there are no transfer points and it can run continuously to the final destination,” says Fantin.

Its first Canadian installation, serving a near surface ore body at Vale’s Copper Cliff operation, provided a test of how the technology can be integrated into a re-engineered mining process. After finding the system doubled its development-advance rate, Vale now has plans to install it in two more mines in Brazil. Rail-Veyor compares its systems to a Lego set, with components that combine to create customizable solutions. Using the experience gained during the Vale project, Rail-Veyor has changed some components to make a lighter and modular system that can be more easily manufactured and installed.

Rail-Veyor has intrigued operators and garnered press around the world since it debuted, but still has only a handful of installations. “Using a Rail-Veyor system can fundamentally change the mining process,” says Fantin, adding that it can lower operating and capital costs when “mine planners integrate the system into their initial mine design.”

Often Rail-Veyor gets called in too late in the process. Well into building an underground mine in Africa that relied on conveyors and trucks, one client proposed transferring ore from truck, to ore pass, to Rail-Veyor. When a contact from Vale suggested that the company put in a spur to send the train directly to the level being mined, the client’s eyes lit up with the possibility, says Fantin, although it was recognized as too late to do so.

That is not to say the technology only suits new mines. The Vale experience in the Sudbury basin showed that an operating mine looking to transition to Rail-Veyor can do it by identifying the right transition point – when the long-term benefits outweigh new equipment costs, or when the mine naturally progresses to a new ore zone.

RopeCon: steep hills, low costs

For mines operating on hillier terrain, or that are removing ore from a pit of suitable geometry, rope-based conveyors can pick up the slack. Doppelmayr’s RopeCon, for one, suspends its load from a structural rope system.

RopeCon’s polyamide wheels run along continuous steel track ropes, bearing a conveyor belt with corrugated sidewalls for up to 20 kilometres. An inspection trolley runs overhead on a third set of ropes. “It effortlessly spans valleys and obstacles, thus enabling direct, short routes between two points,” says Stefanie Reis, part of the international sales team at Doppelmayr. “Being an elevated system, it also minimizes space requirements along the line.”

BeMo Tunnelling GmbH successfully used the first RopeCon on a civil works site in Tyrol, Austria, from 2002 to 2004. To get from the tunnel to the dump site, muck had to cross a road, a creek, and a railway line. A conventional conveyor belt would have been expensive and difficult to install, since support stanchions would need to be widely placed. RopeCon, on the other hand, only requires one support stanchion every 250 metres. The cost of using haul trucks would have been comparable, but BeMo opted for RopeCon because it seemed faster and more reliable, particularly during winter. The installed system was capable of conveying about 600 tonnes per hour. Maintenance – mainly regular greasing – took only a couple of hours out of the day for the one maintenance person on site.

The RopeCon system has also seen some uptake in the mining industry. Jamalco, a joint venture of Alcoa and the Jamaican government, went with RopeCon at its Mount Oliphant bauxite operation. The system, with its 6.8-kilometre long ContiTech belt, runs 3.4 kilometres to the St. Jago loading station. Both overland trucking and conventional conveyors were considered, but RopeCon had a smaller environmental footprint. The additional benefit has been savings in energy costs – US$1.5 million in the first four years alone. On its bauxite-loaded descent, RopeCon generates about 1,200 kilowatts of braking energy per hour, which goes back into the operation and is also fed into the Jamaican grid.

However, the system remains unique among Alcoa’s operations, as none of its other mines have the same steep terrain as Mount Oliphant. Another mining customer uses RopeCon in Papua New Guinea, but overall the market for suspended conveyors has been slow. The total cost of installation and operation for RopeCon becomes competitive with other conveying systems when the terrain gets rough or difficult, or when a low footprint is beneficial for environmental reasons or for crossing water and infrastructure. It is “a very well-engineered system, and I think that is reflected in the cost,” says WorleyParsons’s Davis. A similar cable system, Metso’s MRC Cable Belt conveyor, designed for long distance applications, has been around for more than 50 years.

Rail and rope systems also do not represent the sum total of innovation; other models just have not gained traction. B.I.D.’s Lawrence says air-supported belt conveyors and enclosed pipe belt conveyors have also been developed, but have no takers among his customers. Rulmeca motorized pulley drives, which enclose drive parts in a compact, sealed space, have also experienced limited success despite their advantages.

Users often prefer the components they have previously used and know to be reliable at low cost to newer, less familiar ideas. But for the users with specific problems or the willingness to test out new innovations, solutions are out there.

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