Tag Archives: screens

Trollope Mining Services boosting southern African reputation with Metso hybrid crushers and screens

Comminution of minerals, Mining equipment, Mining services, , , , , , , ,

Amid growing demand for its crushing and screening services, Trollope Mining Services, one of the largest open-pit mining contractors in Africa, has continued to increase its fleet of Metso machines from Pilot Crushtec, the South Africa-based company says.

With nearly 500 pieces of equipment in its fleet, Trollope has over the years established itself as the go-to contractor in the open-pit mining sector in southern Africa, it says. Currently operating in South Africa, Namibia and Botswana, the company has also previously executed projects in the Democratic Republic of the Congo and Guinea. The company operates across commodities including but not limited to coal, platinum, copper, andalusite, gold, phosphate, lithium, iron ore, manganese, diamonds and limestone.

To establish itself as a total solutions provider in the mining contracting fraternity, Trollope Mining Services added a crushing and screening division to its business in 2016. Managing Director, Guy Hopkins, says that in the past three years the division has seen exponential growth on the back of some major projects, necessitating an expansion of the crushing and screening fleet.

Following the fleet expansion program, Trollope Mining Services now operates a total of 15 machines. Of note is that the whole fleet is made up of only Metso machines.

“We prefer Metso machines because of our experience with the equipment,” Hopkins says. “Fundamentally, the design and build quality of these machines are unmatched. Our buying decision is also influenced by the technological evolution of the Metso offering, which allows us to run ‘hands off’ operations. Apart from improved efficiencies, technology paves the way for improved safety on mining sites.”

Of its 15 Metso machines, six are dual-powered units, making Trollope Mining Services the biggest operator of Metso hybrid crushers and screens in southern Africa, confirms Charl Marais, Sales Manager at Pilot Crushtec. The dual-power fleet comprises two Lokotrack® LT120E™ jaw crushers, a Lokotrack LT330D™ cone crusher and three Lokotrack ST2.8E™ scalping screens. These were expressly purchased for a project in the Northern Cape Province of South Africa.

With their ability to have both electricity and diesel as power sources, Marais says dual-power solutions provide the best of both worlds – significant fuel savings and a marked reduction in carbon emissions. “Significant cost reduction is achieved when the machines are connected to the grid,” he explains.

Hopkins added: “Given the high cost of diesel, dual-powered solutions help reduce operating costs for our customers. In our experience, the cost of running bi-power machines off the grid is 1/20 the cost of running them off a diesel engine. There is therefore a major cost benefit for our customers’ operations.”

Apart from the Metso build quality, Hopkins says the aftermarket support from Pilot Crushtec is crucial to ensuring high uptime.

“In all our buying decisions, having a partner that we can trust for the long term is fundamental,” he said. “Pilot Crushtec plays a crucial role in supporting us with all the necessary spares and technical expertise to keep our Metso machines running.”

Sandvik’s first South Africa-manufactured screen destined for gold mine in northeast Africa

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Sandvik Rock Processing says it has marked a significant step in its expansion across Africa with the successful completion of its first South African-manufactured screen package.

This milestone project was undertaken at the company’s Spartan facility in Johannesburg, which already produces the Kwatani and Schenck products as part of Sandvik’s screening solutions offering. The capability to also produce the Sandvik original screen range signals a new phase in Sandvik’s African presence and growth, the OEM says.

Riaan Steinmann, Europe, Middle East and Africa Operation Director Screening Solutions at Sandvik Rock Processing, says the achievement is a testament to the facility’s local design and engineering prowess. He emphasises the South African facility’s capability to build high-quality vibrating screens from raw materials, which also includes a range of exciter gearboxes using locally procured castings.

This innovative approach enables the company to maintain strict quality control and facilitates shorter delivery times for its customers, thereby improving the customer experience significantly, Sandvik said.

The screen package that marks this milestone was specifically ordered by a gold mining client located in northeast Africa. It includes a vibrating grizzly screen with a motor-driven exciter, five feeders and two custom-engineered feed-in chutes.

Steinmann praised the facility’s streamlined processes and the benefits of local procurement, which collectively allowed the project to be successfully completed within an impressive timeframe of three months.

“Manufacturing screens in South Africa represents the same standard as those produced in Europe or India,” Steinmann says, underscoring the global quality benchmark. He also notes the multiple benefits including reduced shipping times and costs due to Southern African Development Community trade agreements. Moreover, he highlights the positive impact on the local economy through exports and increased capacity, leading to job creation.

“Importantly, we aim to serve not only the African continent but also other regions within the Sandvik Rock Processing group,” Steinmann concludes. “The successful execution of this first Sandvik screen package has not only underscored our position as a world-class manufacturer but also underlines our ambition to become Africa’s preferred screening solution partner.”

Tungsten West makes EPCM progress at Hemerdon as TOMRA XRT ore sorters hit the road

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Tungsten West has named Fairport Engineering Limited as its engineering, procurement and construction management (EPCM) contractor at the Hemerdon tungsten-tin project, in the UK, as well as confirmed it was soon expecting to receive seven X-ray Transmission (XRT) sensor-based ore sorters from TOMRA.

Since successfully listing on the AIM Market of the London Stock Exchange, Tungsten West has been advancing the development of Hemerdon, which is one of the most advanced mining projects in England and is expected to be a key future global supplier of tungsten and tin.

Hemerdon is, Tungsten West says, the third largest tungsten resource globally, as well as being a previously producing mine that was operational from 2015-2018. Tungsten West purchased the Hemerdon Mine in 2019, and has since completed a bankable feasibility study that demonstrated an extensive reserve of approximately 63.3 Mt at 0.18% W and 0.03% Sn, as well as 37.4 Mt of saleable aggregate material. The company estimates that the life of mine is currently 18.5 years with the opportunity to extend this through future investment.

On top of the ore sorters, Tungsten West said the rest of the long-lead items had been ordered and were scheduled for delivery within the company’s timetable. It plans to recommence mining this year.

The upgrade and refurbishment of the existing processing plant at Hemerdon is centred around the optimisation of the existing concentrator circuit as well as the introduction of a new crushing and screening circuit that will then feed into a new XRT ore sorting stage. These upgrades will streamline processing, minimise plant downtime and improve recovery rates, according to the company.

After significant test work, Tungsten West engaged TOMRA to supply the seven units that are required to treat the run of mine throughput. This consists of six duty and one standby units. Orders and deposits for these units were placed in 2021 and the units have now been delivered to the UK and await final transfer to Hemerdon where they will be installed in the front end of the processing plant.

On top of this, six new screens and 11 vibrating pan feeders have been ordered from Vibramech of South Africa at fixed prices. These will replace the existing large screens, which caused the low frequency issues, and were a key contributor to plant downtime under Wolf Minerals – the previous owner of Hemerdon. Delivery is expected in the June quarter of 2022.

Max Denning, Tungsten West CEO, said: “We are extremely pleased with progress at site, particularly the onboarding of Fairport Engineering to undertake the detailed design and construction of the project. We are looking forward to working with Fairport as we move towards restarting full production at Hemerdon, with a substantially improved processing route, through the introduction of XRT ore sorting and upgraded processing equipment. The company has assembled a strong projects and operations team, and we remain confident in our progress.”

FLSmidth improves water balance at Mozambique coal plant with thickener tech

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FLSmidth has been chosen as the preferred provider for four large bolted thickeners for a large mining customer in Mozambique.

Two of the thickeners are designed to reduce water load on the filters allowing for a drier filter product, while the other two thickeners recover water from the plant tailings.

The installation, which includes E-Volute™ feedwell technology for superior flow distribution, will contribute to achieving optimal water balance at the coal plant in Mozambique, FLSmidth says.

“The thickeners measure 45 m in diameter and will control the density of material to the belt filters, improving the plant’s output,” Howard Areington, FLSmidth’s General Manager for Projects and Account Sales in sub-Saharan Africa and the Middle East, says. “The design was based on the test work we conducted on the customer’s material, allowing us to determine the best thickener solution.”

He emphasised that a bolted thickener is quicker and safer to construct on site, saving on costs and improving quality control; both of these factors suited the project’s remote location.

“The extent of welding in the construction of normal steel thickeners typically runs into kilometres,” Areington said. “By contrast, the amount of on-site welding required by a bolted thickener can be measured in metres.”

The E-Volute feedwell technology improves flow distribution, leading to lower flocculant consumption, better settling rates and improved overflow clarity for the optimal performance of the thickener, according to FLSmidth.

Despite the COVID-19 lockdown, good progress was made on the fabrication of the thickeners in South Africa, according to FLSmidth Project Manager, Kevin Kockott. This has been managed by leveraging FLSmidth’s global resources and the design teams’ ability to work remotely.

“Our local South African office collaborated closely with our engineering hub in Salt Lake City in the United States, ensuring that our engineering work on the project was able to continue without interruption,” Kockott said.

FLSmidth has been involved with this project for almost a decade and has provided a significant portion of the coal preparation equipment. To date, this has included reflux classifier technology, pumps, screens and feeders.

Weir Minerals wins large comminution order from Nigeria iron ore mine

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Two of the largest screens built by Weir Minerals Africa are being designed and manufactured in South Africa as part of a process solution for an iron ore mine in Nigeria.

According to Tiisetso Masekwameng, General Manager Comminution at Weir Minerals Africa, the flowsheet accepted by the customer includes equipment for screening, washing, and grinding supplied by Weir Minerals.

“Within our scope of work are the two largest Enduron® double-deck banana screens built by Weir Minerals,” Masekwameng says. “This is made possible by the depth of design expertise in our Separation Technology Group, an eight-strong team conducting research and development.”

Steven Hunter, Separation Technology Group Leader at Weir Minerals Africa, says the two 51 t Enduron double-deck banana (DBHG 43/97) screens (one pictured) for this project were built upon the designs of the existing Weir Minerals screens range. These large machines measure 4.3 m wide and 9.7 m long and can process 1,750 t/h.

“The customer’s production requirements demanded this considerable size, so we optimised the design by minimising mass without compromising structural integrity,” Hunter says. “We conducted extensive finite element analysis on the whole machine but focused on the main structural elements, ensuring that the units were fit-for-purpose while still being light enough to be driven by the exciters.”

The size of the units still demanded the design and manufacture of Weir Minerals Africa’s largest exciter yet – the Enduron LTX 10. With 120 t of excitation force (at maximum setting), these units will drive the screens at a stroke of 9.4 mm and a gravitational force of 4.6 G.

Hunter said the screens are ready to be fitted with Weir’s IIoT platform, Synertrex. “This allows the machines to be monitored remotely; the system can measure the machine’s performance and any deviations arising that may require proactive attention,” he explained.

The order for Nigeria also includes two Trio® jaw crushers, two Trio cone crushers, two large 2 m by 8 m Trio apron feeders, two Trio pan feeders, eight Enduron vibrating screens and an Enduron HPGR.

For the clay washing circuit, Weir Minerals Africa will supply the mine with a Trio twin-shaft blade mill and Trio twin-shaft coarse washers as well as Warman® slurry pumps.

Kwatani branching out from South Africa roots

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Vibrating screen and feeder specialist Kwatani says it is transitioning from equipment supplier to solutions provider, as it attracts customers from well beyond its South Africa headquarters.

According to Kwatani General Manager Sales and Service, Jan Schoepflin, the company’s strong in-house expertise and design capability – combined with the manufacturing quality it consistently achieves – ensures its customised solutions deliver optimal performance at the lowest possible lifecycle costs.

“Our recent orders show that our customer base in Southern Africa remains strong, while there is growing recognition of our cost-effective offerings in West Africa, East Africa and North Africa,” says Schoepflin. “At the same time, orders from countries like Canada and Russia indicate that our markets abroad continue to grow.”

Kwatani says it remains the market leader in the supply and servicing of vibrating screens and feeders on iron ore and manganese mines in South Africa’s Northern Cape province. It also counts platinum, coal, diamond and gold mines in its customer base. Its West Africa orders have been mainly to gold mines, and there is growing potential for gold mining in East Africa, Schoepflin says.

Over its four decades of operation, Kwatani has produced about 16,000 custom-designed screens, and is building, on average, 30 to 40 units a month in its ISO 9001:2015 certified facility close to OR Tambo International Airport in Johannesburg.

“Our reputation has been built on prioritising what our customers need, and doing business with integrity and trust,” Schoepflin says. “This means delivering on what we promise and making sure that customers achieve the expected value from our products.”

The company’s solution focus is underpinned by its significant and ongoing investment in local skills, ensuring that its designs leverage strong mechanical and metallurgical engineering expertise, according to Schoepflin.

“This confidence in our products allows us to offer a process guarantee to customers, to deliver the tonnage, throughput and fractions that they expect,” he says. “Depending on which country our customers operate in, they may also have different industry and quality standards/certification expectations and we work closely with them to understand these clearly and meet their requirements.”

Schoepflin also emphasises the company’s service capabilities, which include its local service centres closer to customers, and its support partners in other countries.

“The careful selection of these partners is vital to meet customers’ stringent technical expectations,” Schoepflin says. “In some countries, our partners can also manufacture components according to our drawings and specifications, should there be an urgent requirement from a customer.”

Kwatani collaborating with EPCMs, miners on bespoke screening options

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Mineral process plant designs are favouring higher-capacity vibrating screens and a more holistic approach to plant optimisation, according to screen specialist Kwatani.

“These trends hold great potential for the mining sector, and Kwatani has been at the forefront of technologies driving this direction,” Annelize van der Walt, Kwatani’s Business Development Manager for Mining and Minerals, says.

Vibrating screens are essentially the “glue” that integrates various unit processes, from bulk materials handling to optimally liberated comminution and pre-concentration, according to the company.

“Larger, engineered-for-tonnage screens are growing in popularity, as they reduce the number of processing modules and hence the level of infrastructure required, especially on mega-projects,” van der Walt says. “Higher capacity is becoming the new design standard for greenfields projects.”

There is also an ever-greater demand for reliability and uptime in these mission-critical machines, as well as an expectation of longer lifespans. All this requires bespoke solutions that address site-specific conditions, van der Walt says, while leveraging digital technology for real-time monitoring and control.

“Kwatani’s metallurgists and engineers use their extensive on-site experience and in-house laboratory facilities to innovate from our proven technologies,” she says. “A cornerstone of our philosophy is close collaboration with engineering, procurement and construction management contractors and end-customers to customise solutions, from concept to construction, commissioning and operation.”

Annelize van der Walt, Kwatani’s Business Development Manager for Mining and Minerals

Specific conditions include waterless beneficiation in arid Mauritania, where Kwatani’s screens operate completely dry in an iron ore plant. In South Africa and Botswana, meanwhile, the company has retrofitted dewatering screens to reduce water consumption, while increasing output by 40% with the same footprint.

“We also recently designed screens for exceptional ore characteristics in a precious metal beneficiation facility in Canada,” she said. “This required a high level of customisation, not only in the screening media but in the mechanical design.”

Remote mine locations – which are difficult to access for maintenance and replacement purposes – also guide the design parameters. In a recent project, Kwatani innovated by selecting special hard-wearing materials for the construction of the screening equipment. The design included components that would provide early warning of wear.

Embracing a more holistic plant design approach, customers often invite Kwatani to participate in optimising the screening side of their chosen beneficiation technology, van der Walt says. A different screening approach would be taken, for instance, in a dry pre-concentration application than in wet dense medium separation.

“This holistic approach is also facilitating greater synergy between original equipment manufacturers,” she says. “This is a very positive trend, allowing us to consider the impact of different equipment on the performance of each – from mineral processing apparatus to transfer chutes.”

Underpinning Kwatani’s responsiveness to customer’s specific needs is its ongoing research and development.

“Our R&D unit is currently working on projects to suit our designs to novel crushing and grinding technologies, which are changing the whole approach to the process flow of future plants,” van der Walt says. “These are significant innovations for the mining sector, and we are excited to be at the forefront with our evolving screen designs.”

Kwatani is incorporating digital technologies to facilitate remote monitoring and control of its vibrating screens. It is also piloting a service app for mobile phones, which helps operations predict their maintenance needs more accurately. The app also helps to drive down the total cost of ownership by gathering data that can be used in future design improvements.

Latest Kamoa-Kakula copper studies reaffirm project’s world-class status

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The latest economic studies on Ivanhoe Mines and Zijin Mining Group’s majority-owned Kamoa-Kakula project in the Democratic Republic of Congo have indicated the asset could become the world’s second largest copper mining complex.

First production at Kamoa-Kakula is less than a year away, but the project partners have continued with a series of economic studies that emphasise the world-class nature of the orebodies within their control.

The headline maker is the results of a preliminary economic assessment that has evaluated an integrated, multi-staged development to achieve a 19 Mt/y production rate at the mine, with peak annual copper production of more than 800,000 t.

At the same time, a prefeasibility study (PFS) has been carried out to look at mining 1.6 Mt/y from the Kansoko mine, in addition to 6 Mt/y already planned to be mined from Kakula, to fill a 7.6 Mt/y processing plant at Kakula.

A definitive feasibility study (DFS) has also evaluated the stage-one, 6 Mt/y plan at Kakula, which is currently being constructed and is less than a year away from producing first copper, according to Ivanhoe Co-Chair, Robert Friedland.

While the operation looks to have the scale of a world-class asset, it will also have top ranking ‘green’ credentials, according to Friedland.

“The Kakula mine has been designed to produce the world’s most environmentally-responsible copper, which is crucial for today’s new generation of environmentally- and socially-focused investors,” he said.

“Zijin shares our commitment to build the new mines at Kamoa-Kakula to industry-leading standards in terms of resource efficiency, water and energy usage, and minimising emissions. We are blessed with ultra-high copper grades in thick, shallow and flat-lying orebodies – allowing for large-scale, highly-productive, mechanised underground mining operations; and access to abundant clean, sustainable hydro electricity to power our mines – providing us with a distinct advantage in our goal to become the world’s ‘greenest’ copper miner and be among the world’s lowest greenhouse gas emitters per unit of copper produced.”

The project recently retained Hatch of Mississauga, Canada, to independently audit the greenhouse gas intensity metrics for the copper that will be produced at Kamoa-Kakula.

The Kamoa-Kakula Integrated Development Plan (IDP) 2020, as the companies refer to it, builds on the results of the previous studies announced in February 2019.

DFS to 6 Mt/y

The new DFS incorporates the advancement of development and construction activities to date, and has once again confirmed the outstanding economics of the first phase Kakula Mine, Ivanhoe said.

It evaluates the development of a stage one, 6 Mtpa underground mine and surface processing complex at the Kakula deposit with a capacity of 7.6 Mt/y, built in two modules of 3.8 Mt/y, with the first already under advanced construction (see photo). It comes with an internal rate of return of 77% and project payback period of 2.3 years.

The first module of 3.8 Mt/y commences production in the September quarter of 2021, and the second in the March quarter of 2023. The life-of-mine production scenario provides for 110 Mt to be mined at an average grade of 5.22% Cu, producing 8.5 Mt of high-grade copper concentrate.

The Kakula 2020 DFS mine access is via twin declines on the north side and a single decline on the south side of the deposit. One of the north declines will serve as the primary mine access, while the other decline is for the conveyor haulage system, which was recently commissioned.

The primary ore handling system will include a perimeter conveyor system connected to truck load-out points along the north side of the deposit. The perimeter conveyor system will terminate at the main conveyor decline.

The mining method for the Kakula deposit is primarily drift-and-fill using paste backfill (around 99%); with the exception of a room-and-pillar area close to the north declines, which will be mined in the early years of production. The paste backfill system will use a paste plant located on surface connected to a distribution system that includes a surface pipe network connected to bore holes located at each connection drive on the north side of the orebody, the company says.

The Kakula concentrator design incorporates a run-of-mine stockpile, followed by primary cone crushers operating in closed circuit with vibrating screens to produce 100% passing 50 mm material that is stockpiled.

At the end of August, the project’s pre-production surface ore stockpiles totalled an estimated 671,000 t grading 3.36% Cu, including 116,000 t of high-grade ore grading 6.08% Cu.

The crushed ore is fed to the high pressure grinding rolls operating in closed circuit with wet screening, at a product size of 80% (P80) passing 4.5 mm, which is gravity fed to the milling circuit.

The milling circuit incorporates two stages of ball milling in series in closed circuit with cyclone clusters for further size reduction and classification to a target grind size of 80% passing 53 micrometres (µm).

The milled slurry is pumped to the rougher and scavenger flotation circuit where the high-grade, or fast-floating rougher concentrate, and medium-grade, or slow-floating scavenger concentrate, are separated for further upgrading. The rougher concentrate is upgraded in the low entrainment high-grade cleaner stage to produce a high-grade concentrate.

The medium-grade or scavenger concentrate together with the tailings from the high-grade cleaner stage and the recycled scavenger recleaner tailings are combined and further upgraded in the scavenger cleaner circuit. The concentrate produced from the scavenger cleaner circuit, representing roughly 12% of the mill feed, is re-ground to a P80 of 10 µm prior to final cleaning in the low entrainment scavenger recleaner stage.

The scavenger recleaner concentrate is then combined with the high-grade cleaner concentrate to form final concentrate. The final concentrate is then thickened and pumped to the concentrate filter. Final filtered concentrate is then bagged for shipment to market.

The scavenger tailings and scavenger cleaner tailings are combined and thickened prior to being pumped to the backfill plant and/or to the tailings storage facility. Backfill will use approximately half of the tailings, with the remaining amount pumped to the tailings storage facility.

Based on extensive test work, the concentrator is expected to achieve an overall recovery of 85%, producing a very high-grade concentrate grading 57% copper. Kakula also benefits from having very low deleterious elements, including arsenic levels of 0.02%.

7.6 Mt/y PFS

The PFS evaluating mining 1.6 Mt/y from the Kansoko mine envisages an average annual production rate of 331,000 t of copper at a total cash cost of $1.23/lb copper for the first 10 years of operations, and annual copper production of up to 427,000 t by year four. This comes with an internal rate of return of 69% and project payback period of 2.5 years, according to Ivanhoe.

Development would see Kakula-Kansoko benefit from an ultra-high, average feed grade of 6.2% Cu over the first five years of operations, and 4.5% Cu on average over a 37-year mine life.

There are currently two mining crews at Kansoko, in addition to the 10 mining crews (three owner crews and seven contractor crews) currently at Kakula, with the ability to increase this number to fast-track the development of Kansoko, Ivanhoe said.

19 Mt/y option

The Kamoa-Kakula 2020 PEA presents initial production from Kakula at a rate of 6 Mt/y, followed by subsequent, separate underground mining operations at the nearby Kansoko, Kakula West and Kamoa North mines, along with the construction of a 1 Mt/y of concentrate direct-to-blister smelter. The smelter section of the study saw China Nerin Engineering act as the main engineering consultant with Outotec providing design and costing for propriety equipment.

The Kamoa North Area comprises five separate mines that will be developed as resources are mined out elsewhere to maintain the production rate at up to 19 Mt/y, with an overall life in excess of 40 years, Ivanhoe says.

For this integrated 19 Mt/y option, the PEA envisages $700 million in remaining initial capital costs, with future expansion at Kansoko, Kakula West and Kamoa North funded by cash flows from the Kakula mine, resulting in an internal rate of return of 56.2% and a payback period of 3.6 years.

This shows the potential for average annual production of 501,000 t of copper at a total cash cost of $1.07/lb copper during the first 10 years of operations and production of 805,000 t/y of copper by year eight, Ivanhoe said.

“At this future production rate, Kamoa-Kakula would rank as the world’s second largest copper mine,” the company said.

Kwatani screens and feeders tackle manganese ore in South Africa

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As a vital aspect of a plant expansion at a manganese mine in the Northern Cape of South Africa, Kwatani says it is supplying four heavy duty vibrating screens and 10 feeders to help boost throughput.

According to Kwatani CEO, Kim Schoepflin, this large-scale equipment is custom-designed and engineered for tonnage to meet the mine’s challenging operational requirements.

“Manganese ore is very demanding on vibrating screens as it has a high specific gravity and is also very abrasive,” Schoepflin says. “Our machines are engineered to perform the application’s duty requirement while being robust enough to deliver maximum uptime.”

The units being supplied include a 3.6 m double-deck scalping screen, a 3 m double-deck screen, a 2.4 m screen and a 1.8 m dewatering screen. A local OEM that has designed and engineered vibrating screens for over four decades, Kwatani has built a reputation for world-class expertise and capability, it says.

“Customers choose us for our engineering track record – developing technology that can manage the tonnages they require,” Schoepflin says. “This means understanding each mine’s specific conditions, and then building a design to meet a range of complex mechanical and metallurgical factors.”

The order to the mine is being rolled out on time and on specification to the customer’s satisfaction, according to Kwatani COO, Kenny Mayhew-Ridgers.

“The efficiency and quality of our work process allows us to design, manufacture and deliver custom-designed screens in the same timeframes that other OEMs deliver standard models,” Mayhew-Ridgers said.

This is particularly demanding as custom-designed equipment undergo an intensive design process after being verified by rigorous finite element analysis in-house, Kwatani says. Prior to dispatch, all units endure intensive testing before being commissioned on a customer’s site. For this reason, Kwatani boasts its own in-house advanced testing facilities at its Kempton Park facility, in South Africa. Aligned to ISO 9001 standards, the testing protocols have been developed in-house with decades of experience. This allows full testing similar to cold commissioning, even before delivery to site.

Weba Chute Systems and Kwatani save the day at South Africa gold mine

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Weba Chute Systems and Kwatani have come together to design and install ore silo chutes at a South Africa gold mine to reduce mill wear and other processing challenges caused by the uncontrolled flow of mined material into the mills.

The solution from Weba and Kwatani, a leading local manufacture of vibrating screens and feeders, must also deal with frequent large-size material as the mine has no crushing stage before the milling circuit, Weba said.

According to Weba Chute Systems Technical Advisor, Alec Bond, the over-feeding of material through the existing manually operated chutes is causing regular “mill vomit” in the mine’s four mills. The inconsistent feed exacerbates wear on mill bearings as the material’s weight shifts forwards and backwards inside the mill.

The waves of material causing the “vomit” carry insufficiently milled material out of the mill, including large chunks of rock. This leads to problems for the downstream mineral processing facilities, including inefficient recovery in flotation cells and even blockages in pumps, according to Bond.

“The challenge starts with the existing chutes needing constant supervision and control by operators, being opened and closed with a chain block device,” he says. “Our solution was to design a robust, self-controlling chute and feeder system that would ensure an even flow of material into the mills.”

He explained that the mine’s existing system has no means of closing the silo outlet; any maintenance at the chute area requires the emptying of the silo and the stoppage of the mill. Each of the four silos has three outlet chutes.

Weba Chute Systems Designer, Wesley Hunkin, says: “We therefore added a spile bar arrangement which seals off the silo. The Weba chute, which is choke fed, is placed under this installation. This allows the feed rate to be controlled by the Kwatani feeder, which has been integrated into the chute design.”

The vibrating action of the feeder controls the tonnage and feed rate to the mill, keeping the flow constant. New mounting structures have been designed to accommodate each chute and feeder. There will also be civils works below the silo to provide a solid foundation that absorbs vibrations from the feeder, according to the companies.

A serious challenge is over-sized rocks in the ore feed, which can be up to 800 mm in size. This makes it important for chute designs to accommodate the worst-case scenario of chutes choking, says Hunkin.

He highlighted that the flow of material is also controlled to prevent direct impact onto the conveyor belt feeding the mills, and to ensure central loading onto the centre of the belt.

“If the material from the feeder is biased to the one side, our chute brings everything to the centre of the conveyor,” he says. “This enhances the consistency of material flow into the mill.”

Bond emphasised that the customer motivated for a concept change to address the challenges being experienced with the silo feed.

“Given our materials handling experience, design expertise and high-quality local manufacturing facility, we were able to work closely with the customer and with Kwatani to turn this new concept into reality,” he said.

“Our solution promises direct savings in terms of mill bearings, as well as less mill downtime. There will also be significant gains in terms of recovery rates in the plant if the flow and size of milled material can be improved.”