Tag Archives: screens

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

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.”

Schenck displays continental comminution offering with Peru copper contract

Schenck Process has won a contract to design manufacture, supply and commission vibrating screens and feeders for the greenfield Mina Justa copper project, in Peru.

The order will see Schenck business units on four continents combine to deliver seven banana screens (across three models), five diverging pan feeders and one grizzly feeder.

Mina Justa, owned by Minsur and Empresas Copec through holding company Cumbres Andinas, is slated to produce around 100,000 t/y of copper when fully ramped up.

The screens and feeder contract will see all design completed at Schenck’s vibrating equipment design centre in Sydney, Australia, manufacture and testing in the company’s Chinese plant, custom-made screen panels from the South Africa production facility and commissioning by the aftermarket services team in Chile. The project is being managed and coordinated by the Australia-based Project Management team, Schenck said.

The screens include several mechanical and operational improvements developed on a prototype vibrating screen now undergoing site testing at an iron ore mine in Western Australia, according to the company.

“The five larger screens feature laminated side plates to maintain structural integrity and reduce stress concentrations associated with the projected process tonnages,” Schenck explained. “Additionally, machined transition flanges are welded in a low stress area to the cross beams to actively reduce fatigue, and a unique spring removal system has been fitted to facilitate and reduce downtime during spring change-outs.”

The six feeders have been designed to account for site conditions and feature a more robust design. They are also equipped with exchangeable liners and an upgraded transition hopper to improve operational availability and performance, the company said.

Each of the vibrating feeders and screens for Mina Justa is equipped with CONiQ, the company’s proprietary continuous six-dimension condition monitoring system, to track and alert operators to abnormal operating conditions. Feeder control systems have been electronically aligned with the screen’s installation, Schenck added.

Project manager, Lauren Williams, said: “This is a truly international project and, from our point of view, it is the best way to give our customer the equipment that will deliver higher process efficiency and longer service life.

“Although based on standardised platform designs for screens and feeders, each unit has been subject to a customising process to meet site and processing capacity requirements. We are delivering an integrated package of screens and feeders to optimise availability and productivity and represent the best value for money.”

Multotec ready for the mineral processing test

Mineral processing specialist, Multotec used a recent media visit to talk up the testing facilities at the heart of its Technology Division.

The South Africa-based company can carry out a range of testwork with its specialised equipment in Spartan, Gauteng, according to Multotec Technology Manager, Faan Bornman.

“Much of our testwork comes from customers who are in the early stages of project development,” Bornman says.

“They need to understand more about how their minerals or material will separate under given conditions. Often there is not a mathematical model that can predict accurately what they can expect.”

Testwork can reduce project risk significantly, providing a solid foundation for the subsequent design and optimisation of process facilities, Multotec says, with Bornman noting that physical testwork is usually the best way of finding out how particles will behave in a process plant.

The equipment available to Multotec customers includes laboratory-scale wet high-intensity magnetic separators, cyclone rigs, filtration equipment, centrifuges, spiral rigs and a screening research rig. There is even capacity to test water purification methods on mine effluent.

“Extensive test work is especially relevant when a customer is wanting to mine and treat less traditional minerals like lithium or graphite,” Bornman says. “As demand grows for commodities like these, we have had customers bring samples to test how our equipment would perform. In these tests, we trial various methodologies and scientifically record and compare the results.”

The R&D laboratory prepares samples and conducts particle size analysis using equipment such as pressure filters, drying ovens, sieves, shakers, sizers and separating funnels. When chemical analysis is required, samples are sent to outside laboratories.

Bornman said his division also receives enquiries from existing customers when they face challenges: “We research the application of different methodologies to customer material, often leading to the development of a new product or improvements to our existing products,” he said.

“In addition to providing a solution for the customer, we are also able to contribute to the efficiency of the industry as a whole, with an updated and commercialised product.”

Screening

When it comes to tests on mineral screening, a test rig – located at Multotec’s Spartan headquarters – delivers two primary benefits, according to Chris Oldewage, Technology Manager at Multotec Manufacturing. First, it facilitates the in-house development process of screening media products. Second, it allows screening media to be tested against customer requirements to ensure the right solution is delivered.

“The ongoing research and development behind our screening media products give the industry opportunities to optimise efficiencies and recoveries,” Oldewage says. “However, changing anything on a plant brings risk of unexpected downtime. Our screening test rig can considerably reduce operational risks by proving any changes before they are implemented on site.”

In the controlled environment provided by the screening test rig, customers can view the actual performance of screening media products with material from their mining operations, Multotec says, with the company’s testing protocols generating the data necessary for detailed process analysis. This facilitates well-informed subsequent decisions, the company said.

The screening rig is made up of three test platforms: a vibrating screen, a sieve bend and a static drain screen platform. The vibrating screen can conduct classification tests, wet and dry dewatering tests, product development tests and plant screen simulations. The static drain screen and sieve bend screening test platforms are wet classification, drainage and dewatering tests.

Multotec Process Engineer, PJ Pieters, said accurate scaling of a customer’s on-mine process is vital for achieving representative and relevant test results.

“We gather a range of key data from customers on our test work questionnaire,” Pieters said. “This includes their material tonnages, volumes of water, screen sizes in operation and aperture sizes on panels among other information.”

This ensures sample sizes are representative and the tests accurately reflect what is taking place in the mine’s processes. Tests, meanwhile, are conducted in triplicate runs to ensure a sound scientific basis for the findings.

Oldewage said: “By removing the risk that mines face in trying new solutions, our testing capability smooths the way for valuable innovation to improve screening performance.”

The screening test facility at Multotec also includes a small Lucotec screen and a small wedgewire trommel screen, both for small-scale verification test work.

Cyclones

Multotec’s large scale cyclone rig, meanwhile, can test the performance of a range of cyclone sizes, up to 450 mm diameter. Tests related to classification, desliming and dewatering, as well as dense medium separation using density tracers, can be conducted.

Among the benefits to customers is the ability to test large volumes of samples, as the rig includes a 1,750 litre sump and a 6/4 pump, Multotec said. Flexibility is provided by a variable speed drive connected to the pump, to vary the flow rates as required by the cyclone size.

Dry samples usually need to be blended before testing, and wet samples may need to be dried before blending. The resulting samples from the test must also be scientifically prepared for particle size and chemical analysis. The precision at each stage is vital, as bulk samples as large as 200 kg may need to be reduced to as little as 100 g.

The rig’s infrastructure also includes two Multotec vezin samplers, which are compliant with the highest design standards to provide reliable samples, according to Multotec. “These help to minimise the common errors of manual sampling and ensure that the integrity of the sample is retained,” the company says.

In addition to using the test rig to analyses the customer’s process flowsheet – with Multotec engineers identifying where its range of classification and other products can add value – the company also uses the cyclone test rig for its own product development.

“This on-going process has resulted in a range of cyclones that are lighter, more cost effective, environmentally-friendly and energy efficient,” the company said. “They all contribute to helping customers lower their cost per tonne in a low footprint, sustainable plant operation.”

Spirals

Multotec says its spiral test rig has been adapted in response to the industry’s need to re-treat chrome dumps and upgrade ultra-fine chrome.

Again, located at the company’s headquarters in Spartan, the rig allows eight to 10 different spirals to be erected at a time.

Jeantelle Rust, R&D Engineer at Multotec Process Equipment, said: “With the drive to process tailings in the chrome sector, we have been running tests on a more compressed spiral with a reduced pitch. This reduces the velocity of the very fine particles.”

This configuration works particularly well when dealing with fine material, hence its application in tailings, Rust said. The spiral could offer a cost-efficient way of separating ultra-fine chrome material and recovering valuable product, according to the company.

Rust said: “Such a solution presents an attractive commercial proposition to industry and will also address environmental concerns presented by tailings dumps.”

Using a “mouth-organ product box”, the material being tested on the spiral rig is split into eight product fractions, not just the usual three for product, middlings and tailings. This helps optimise the mass balance for reporting purposes, according to the company.

The spiral test rig has also been used to evolve designs that deal with coarser material, Multotec said. “Customers were looking for a solution to the ‘beaching’ of coarse coal product on the spiral’s surface, for instance,” it explained.

Rust said: “We were able to modify the angles and diameter of the trough to address this challenge. Our ability to make small adjustments to the equipment, and to test material repeatedly at full scale, is the key to finding practical solutions.”

Multotec has also conducted research for producers of mineral sands where head grades were steadily dropping. This necessitated the treatment of larger tonnages, requiring higher capacity spirals.

“Space constraints on the customer’s site meant that adding spirals to their process was not an option,” Rust said.

“Wider spirals were thus tested for higher throughput, with different angles to minimise losses.”

 

Weir’s Trio feeders, crushers and screens up production at Pattison Sand

Weir Minerals has delivered a custom designed plant that has boosted production and increased the product range at a sand and aggregates miner in Iowa, US.

Family-owned Pattison Sand produces a diverse range of products, servicing several industries including infrastructure and construction.

Weir said: “After successfully using a number of Weir Minerals products at their site, Pattison Sand wanted a custom designed plant capable of producing more than seven materials: concrete stone, road rock and base material, asphalt stone, asphalt chips, railroad ballast and manufactured sand. This was a challenging demand considering most aggregates sites in the region typically focus on producing only a few products.”

Eric Jones, Global Service Director of Comminution Aftermarket for Weir Minerals, said when Pattison Sand presented the plan for their sand plant, the company’s integrated solutions team “worked with them to make it a reality”.

The facility, comprising both an underground and open-pit mine, is located on the Mississippi River. It processes highly abrasive materials and, combined with the physical diversity of the site, presented a number of technical and engineering challenges to Weir. On top of this, the company had three months to deliver and commission the plant.

Chance Harvey, Director of Engineering at Pattison Sand, said: “We develop these solutions with Weir Minerals through a lot of trials, successes and failures, and end up getting the results that we need to continue to survive in the marketplace.

“A lot of the options that other equipment manufacturers supply are standard and by the book. Weir Minerals has the ability to work with us to create solutions for our individual issues.”

The site has a unique rail loadout setup where product is dispatched to customers as soon as gradation and quality data is approved. This meant Pattison Sand needed an efficient, dependable plant to meet stringent delivery requirements.

Weir Minerals supplied a number of products to create two primary and secondary crushing stations at the operation. These included a Trio® TF5220 vibrating grizzly feeder, two Trio EF3603 pan feeders and two Trio TP450 cone crushers. Trio scalping, incline and wet incline screens, as well as a Trio TSW4432 fine material washer, were also supplied.

Full training and support was provided, with Weir Minerals regularly on site to help Pattison Sand optimise their entire process and achieve the desired result, Weir said.

It continued: “The flexibility of the custom built plant has allowed Pattison Sand to operate more efficiently, exceed production target and increase their product range.”

Since commissioning the plant, Pattison Sand has been able to produce 500-800 t/H of high-quality aggregate material, which equates to around 2.5 Mt/y of raw product. Four hoppers provide a loadout rate of 500 t/h enabling Pattison Sand to produce a diverse range of products and still meet demanding customer delivery schedules, Weir said.

Jones said: “When customers purchase Trio products they are buying years of experience from people within an organisation that is dedicated to the industry and its customers. We constantly strive to be closer to our customers. It’s not always perfect, but we work through projects together and are honest with each other. It’s that transparency and working with customers like Pattison Sand which really drives the end solution.”

Siebtechnik and Tema join together

Siebtechnik and Tema have decided to join up and create Siebtechnik Tema as a way of bolstering the new company’s brand identity in the markets for centrifuges, screening machines, and sampling and preparation systems and components.

The two firms already belong to the same group of companies which also includes South Africa-based Multotec.

The company said: “The main aim of this partnership is to ensure a common brand name as well as the finetuning of the worldwide sales and service structures with production sites and representative offices in Germany, the Netherlands, the US, Great Britain, France, Spain, China and Australia.”

Siebtechnik Tima produces mineral separation and screening equipment for the global coal and fertiliser industries, in addition to hammer- and hammer-impact mills, and channel conveyors.