F3 IMG 0768 A panoramic, fish-eye view of the now-completed C2 conveyor system at Grupo Mexico’s Buena Vista mine in Mexico, with the Q4 conveyor under construction next to it. Tenova TAKRAF USA designed and supplied 21 conveyors needed for the mine’s Concentrator II project.

E&MJ looks at how the latest advances in conveyor-system technologies are being applied to solve common, potentially costly material transport challenges

By Russell A. Carter, Managing Editor

Flexibility has never been a strong selling point for conveyors when a project owner is pondering a decision to go with an overland conveyor system or a truck/shovel (T/S) setup—and it’s a valid issue for any operation that will, for instance, have relatively short-lived, widely separated active mining areas throughout the life of mine. However, as recent developments illustrate, the true flexibility of overland conveyor systems is in their ability to solve specific material transport problems that would have T/S equipment spinning its wheels. These problems range from operating in rugged, steep terrain with hard-to-negotiate features such as rivers or canyons, to visibility issues and other environmental conditions that inhibit truck traffic, and to the availability of equipment, drivers, maintenance workers and fuel supplies needed to support a large fleet of haul trucks.

The fact is that conveyors have become tougher and more reliable, longer, more efficient—and yes—more flexible when it comes to handling troublesome materials or terrain. Perhaps most importantly, bulk materials-handling equipment designers, suppliers and engineering consultants are becoming increasingly adept at finding ways to apply the latest technology to solve material transport challenges facing both project owners and existing mine operators. E&MJ looked for recent examples of conveyor-system successes and had no problem finding them.

As mines continue to drive the demand for bigger and faster conveyor systems, bulk material handling design firms will need to assess their approach to all aspects of the project. One notable, large-capacity project is at Buena Vista in Sonora, Mexico, owned by Grupo Mexico. Upon final commissioning of the Concentrator II (CII) project this year, the mine is expected to produce approximately 700,000 metric tons (mt) of copper concentrate annually. E&MJ spoke with the USA office of bulk material handling firm Tenova TAKRAF regarding the company’s design process for this and other large-capacity projects.

For projects like Concentrator II at Buena Vista, a design firm must have a thorough understanding and experience of how to manage a large throughput of material in order to support the client from concept to completion,” explained Thomas Gramling, executive vice president of Tenova TAKRAF USA. “Specifically in the early planning phase, the company’s inherent knowledge, background, and expertise tie directly into helping the client maximize operational efficiency while minimizing costs. The company must have the know-how to bring as much efficiency and economy of scale as possible.”

The Concentrator II conveyor system comprises 18-in. plant conveyors designed to handle 2,000 to 12,000 mt/h and three overland conveyors capable of handling up to 8,000 mt/h, powered by more than 20,000 hp (15,000 kW). Ranging from 120 m to 3.6 km in length, the 21 conveyors span a total of 8.4 km. Approximately 3,300 mt of steel, 10,000 idler sets, 110 pulleys, and 18 km of belt were integrated into the system.

“Designing large throughput equipment means we sometimes have to take new approaches to conveyor dynamics and refine our chute and hopper design elements,” said Gramling. He noted that, “when Tenova TAKRAF started planning the Concentrator design for the long, high-speed conveyor system, we pulled together our engineers from across the globe who specialize in projects transporting large throughput.”

Looking ahead, the company is providing design and supply of a large capacity regenerative conveyor system for Quebalix IV at the Buena Vista mine. Two 3-km-long overland conveyors will deliver coarse copper ore downhill to the leach pad at 12,000 mt/h. The conveyor will use the largest size of a new class of gearbox rated at 2,700 kW. Instead of incorporating multiple types of drives, both conveyors are standardized to the new class of gearbox.

Pipe conveyors have been around for decades, but one would be hard pressed to find any at hard rock mines. The reason is simple: lump size. Pipe conveyors typically have a maximum diameter of 600 mm, and, as a rule, the pipe’s diameter should be at least four times the maximum lump size, but drill and blast mining operations regularly create lumps more than 150 mm.

Some mineral sands operations, on the other hand, have found pipe conveyors to be an ideal solution to many of their biggest conveying challenges. Pipe conveyors resemble trough conveyors at the loading and discharge ends, but between the two material transfer points, idler rollers transition the belt into a tube, virtually eliminating material loss and helping to meet strict environmental regulations. Pipe conveyors can negotiate tighter curves and take steeper inclines and declines than conventional trough conveyors, with fewer transfer points.

As a case in point, in 2000, Richards Bay Minerals commissioned CKIT, a South African designer of pipe conveyors, to develop a material handling system to transfer ilmenite, zircon, and rutile from a sand dune quarry to a nearby stockyard at the Kusasa Terminal in Richards Bay, South Africa. The site featured narrow passes, difficult terrain, and limited maintenance access, plus the surrounding area was environmentally sensitive and necessitated a spill-free design to protect against the mine’s mildly radioactive materials.

CKIT’s initial solution featured a single pipe conveyor nearly 900 m long. The conveyor’s closed design allowed for triangular galleries, which helped overcome access problems by being equipped with a maintenance trolley instead of walkways—a change that also saved weight, improved balance, and cut construction costs on the length of the conveyor. In addition, that weight savings allowed for smaller trestle footprints. And because the mine produced small lump sizes and pipe conveyors can accommodate high bulk densities, the pipe diameter was kept small and the belt rating low, which dramatically reduced the cost of belting for the project.

In the years that followed, CKIT designed two additional pipe conveyors for the project, each 600 m long, to relieve congestion in the processing area.

Richards Bay exemplifies the potential of this technology, and while it isn’t a particularly new project, it has new relevance in North America, where adoption of pipe conveyors has been slow due to the decades-old perception that they carry high capital costs. In fact, industry experts suggest that recent design improvements have made pipe conveyors cost-competitive with trough conveyors when even a single transfer point is eliminated. Plus, pipe conveyors are effectively the only kind of conveyor capable of eliminating dust and spillage and negotiating some topographically challenging areas. They can now be built in excess of 10 km in length and operate at 5,000 t/h.

But only a handful of companies have experience designing pipe conveyors and even fewer operate in the United States or Canada. So, earlier this year, Wolf Point Engineers & Contractors, a full-service engineering, procurement, and construction services provider based in Chicago, entered into a strategic alliance with CKIT to offer EPC pipe conveyor systems to customers in North America. Wolf Point was founded in 2013 by former senior managers in Roberts & Schaefer Co.’s Chicago office, and, as a division of North Alabama Fabricating Co., or NAFCO, it claims to be the only engineering and construction firm to offer in-house steel fabricating and detailing.

The smaller physical-space requirements of a pipe conveyor, along with its ability to negotiate difficult terrain, provide economic advantages to mineral sands producer Richards Bay Minerals.The smaller physical-space requirements of a pipe conveyor, along with its ability to negotiate difficult terrain, provide economic advantages to mineral sands producer Richards Bay Minerals.

France-based RBL-REI has delivered a number of overland conveyor systems since it was founded in the mid-70s, often applying its Curvoduc conveyor technology to installations that require multiple horizontal and vertical curves. In April, RBL-REI commissioned a 1.5-km-long conveyor at Hochschild Mining’s Inmaculada gold-silver mine in the Peruvian Andes. An 800-m-long horizontal curve allows the conveyor to avoid a rugged rocky hill and an archeological zone, and discharges ore at a plant stockpile directly from the crushing station. This design was selected by the customer instead of another proposed solution that would have needed two straight conveyors, because the RBL-REI approach avoided excessive lead times—mostly from permitting delays that would have been encountered with a system that couldn’t conveniently avoid the archeological site, but also because it provided superior capex and opex figures due to the elimination of transfer towers.

The company is currently involved in a large sylvinite project for potash producer Uralkali in the Perm region of Russia. The system will connect a new mine to an existing plant, and will also return tailings from the processing plant to the mine for backfill. RBL-REI’s two-way system will transport ore at a rate of 2,500 mt/h and tailings on the return side at 900 mt/h, over a route that includes a number of horizontal and vertical curves. This project presents several design challenges, including the need for two carrying sides, several horizontal curves, operation at down to –45°C temperatures and design of structural steel and hooding to support as much as 300 kg/m of winter-time snow loading.

This isn’t the first time that RBL-REI has designed that type of setup; it installed a similar system in Australia, where it has been running for more than 20 years, and another in China.

In 2012, RBL-REI commissioned an 11-km-long system at the Koniambo nickel mine in New Caledonia. Koniambo Nickel SAS is a joint venture owned by Société Minière du Sud Pacifique SMSP (51%) and Glencore Xstrata (49%). The conveyor system links the mine, situated in a mountainous environment, with the process plant located on the shore of the island. It consists of two overland conveyors that negotiate 11 horizontal and 43 vertical curves. Because much of the route is downhill, the system was built to provide up to 500 kW of regenerative power to the mine’s power grid. This project, according to the company, was challenging because the layout combines horizontal and vertical curves at the same locations, which required detailed and accurate calculation to ensure belt stability in the curves.

RBL-REI built a curved conveyor system for the Inmaculada mine in Peru that bypasses a rocky hillside and avoids a sensitive archeological site. The system design also provided lower capex and opex.RBL-REI built a curved conveyor system for the Inmaculada mine in Peru that bypasses a rocky hillside and avoids a sensitive archeological site. The system design also provided lower capex and opex.

Choosing the right conveyor belt has a decisive influence on the operating costs of mining operations. Quality components and state-of-the-art technologies play a key role in the life of a mine conveyor system and make an ongoing contribution to efficiency—especially important in times of low commodity prices. Phoenix Conveyor Systems recently reported how a long-running installation of its Phoenocord St 6800 belt has fully met these requirements.

In 2015, Phoenix replaced a Phoenocord St 6800 belt at the El Abra mine in northern Chile after almost 20 years of continuous service. The steel cord belt, 20,000 m in length and 1,600 mm in width, began operation in June 1996 and has since transported about 900 million mt of tough copper ore.

The belt was originally designed for a service life of at least 17 years. Realizing this ambitious goal involved a number of special measures: A special notch- and abrasion-resistant rubber compound was developed for the belt covers, which also provided high tensile strength. The belt’s carrying and running side covers were equipped with special Phoenotec synthetic single-cord transverse reinforcement—an additional wear protection system that doubles the belt’s resistance to impact damage and ripping.

The belt has 82 steel cords integrated into it, each of which is 12.4 mm in diameter and provide an overall minimum breaking strength of 6,800 N/mm. The cover is 14 mm thick on the carrying side and 10 mm on the running side, bringing overall belt thickness to 36.4 mm. Eleven years after going into operation and having conveyed 500 million mt of ore, the belt was found to have lost only 2.7 mm of thickness to abrasion wear in certain sections and just 1.4 mm on average.

Phoenix Conveyor Systems recently replaced an overland conveyor belt at the El Abra mine that had operated reliably for almost 20 years, transporting an estimated 900 million mt of copper ore. Phoenix Conveyor Systems recently replaced an overland conveyor belt at the El Abra mine that had operated reliably for almost 20 years, transporting an estimated 900 million mt of copper ore.

Phoenix said a sophisticated process allowed the entire old belt to be replaced in a single operation that required only a few days of production down time. The new Phoenocord St 6800 belt is monitored by a Phoenoguard PX system, providing real-time information about its overall condition and the state of all of its components. Phoenoguard PX digitalizes the entire belt while it is in operation, recording all data and comparing it with target values. In addition to indicating detected damage on a computer screen, it provides a clear picture of any areas of concern. Changes in the belt condition that exceed certain tolerances are categorized as requiring one of three possible responses; this allows downtimes and production stops to be kept to a minimum. Problems detectable by the system include foreign objects, protruding cords, belt mistracking, abnormal cover wear, insufficient belt cleaning, and the condition of transverse cords and sensor loops.