As heavy bulk materials pass from station to station in a minerals processing plant, processing equipment is stretched to the limits of its capabilities. The wear rate of components, typically in chutes and hoppers is very high.
The cost of replacing worn down consumables makes up a substantial proportion of the total maintenance expenses, so anything that can be done to reduce wear and increase equipment lifetime will have a significant impact on operating cost. The right choice of wear protection can contribute significantly to reducing maintenance costs and equipment downtime.
Current practice for wear protection usually involves wear liners or panels, which are bolted or welded onto the equipment. Different wear liners are applied in different situations, depending on factors such as type of ore, drop height, material lump-size distribution, and angle of impact. Each wear liner has its own advantages and disadvantages. Common types include hard-metal liners, heavy-duty rubber or rubber/ceramic composite liners, each with their own strength and weakness:
High in density, metallic wear liners are heavy – up to 40 percent heavier than ceramic. The hardest metals are particularly expensive and difficult to work with. Furthermore, they have significant limitations when operating in either of the temperature extremes. While hardness is reduced at higher temperatures, impact strength is reduced at lower temperatures.
Ceramic wear liners can be difficult to attach to existing chute work, requiring special adhesives or suspension within an elastomeric matrix. They can also detach easily from the substrate if surface preparation is poor or if the adhesives and elastomers are incorrectly prepared. They are extremely difficult to cut and cannot be bent or formed.
Such challenges have had a significant impact on maintenance procedures and costs. A general issue facing the industry is the loss in production time because of wear liners frequently needing to be replaced and the time it takes to install new liners.
A typical example could be for material of a common ore, such as gold, copper or nickel, with a hard impact velocity of more than 7 m/s. In such a situation, the wear liner may have an average lifetime of one or two months at most. The replacement procedure can take a whole shift, putting the process flow on pause for several hours resulting in significant production losses.
With units of wear liners weighing anywhere between 20 and 40 kg apiece, safety is also a concern. A special lifting mechanism is often needed in addition to the scaffolding, allowing maintenance personnel to safely access the installation points.
Composite structure of steel and ceramic components
FLSmidth has developed a new wear liner solution specifically to address the challenges of operating crushing equipment, particularly related to wear liner longevity and installation time as well as the safety of personnel involved.
A unique composite structure of steel and ceramic components, FerroCer® Impact provides the advantages of both ceramic and metallic materials. Combining the superior abrasion resistance of a ceramic with the strength, toughness and malleability of a metal, it handles hard and abrasive materials in medium to high impact applications.
Traditional metallic liners wear down too quickly and ceramic liners tend to crack or disintegrate. FerroCer Impact has been shown to increase wear resistance by a factor of up to 15 times compared with traditional wear solutions, depending on the ore type and application. This allows minerals processing plants to achieve a total cost of ownership less than half that of other liners.
FerroCer Impact panels are lighter and less bulky than traditional metallic liners. Each panel comprises a number of ceramic inserts enclosed within a matrix of cast metal. The matrix protects the more vulnerable side faces of the inserts and ensures that only the wear face of the ceramic is exposed to material impact.
The tapered geometry of the ceramic inserts and corresponding holes within the matrix act to wedge the inserts within the matrix and prevent material particles and fluids from causing them to be ejected from the matrix.
This design also enables the remaining wear life of the ceramic inserts to be visually assessed. As the exposed surface of the insert is progressively worn away, its area and face width increase. There is a direct correlation between an insert’s face width and height so that the one can be readily calculated from the other.
Ease of installation
The panels’ low weight (approximately five kilograms) and compact shape make them quick and easy to install using nothing more than standard hand tools. FerroCer Impact can be installed in chutes, hoppers, bins, guides, deflector plates or any place where bulk material is conveyed in a mine or minerals processing plant.
In one nickel processing plant, the FerroCer Impact panels were installed in a conveyor discharge chute downline from the primary crusher unit where the material drops six meters from one conveyor belt down to another one. The hardness of the nickel ore is approximately five on the Mohs scale. After installation, the plant has until now operated for 319 days (and still running), and it operated at full production of 900 mtph with lump sizes of up to 250mm in diameter. This was a big step up from the previous liner, which had lasted less than three weeks on average.
On a different site, FerroCer Impact panels were installed in a chute downstream from the primary crusher of a gold mine where the drop height is two meters and the lump size up to 400mm in diameter. The previous liner type, consisting of heavy-duty rubber bars, typically lasted no longer than six weeks. After the first 17 weeks in operation, the wear measurements taken on site indicate that the new FerroCer panels will last at least another 80 weeks, making them at least 10 times better than the previous liner solution.
Low total cost of ownership
Chutes and hoppers are amongst the most heavily threatened pieces of equipment in the industry. Like conveyor belts, solid handling equipment is exposed to extensive erosion and abrasion from excavated materials of varying sizes. The impact, trajectory and volume with which some of the material is transported through the chutes and hoppers can have detrimental effects on their structure. This can leave equipment affected by cracks, holes and wall thickness loss as a result. By extending service life FerroCer Impact answers an important need in the minerals processing industry. It combines long wear life, ease of installation and affordable pricing to achieve a total cost of ownership which is less than half that of other liners. Its low replacement rate results in greatly reduced lost production time for mines.