Abrasive wear and its effects on process equipment is one of the primary causes of downtime in mining operations. The mining process usually involves a wide range of abrasion, impact and corrosion. Heavy duty equipment parts are often exposed to large stones, aggregates, sand and aggressive slurries that can damage and abrade even the hardest reinforced steel substrates. Preventive maintenance is very important because it restores the structural integrity of the equipment parts and ensures durability.
Furthermore such forward thinking can help alleviate the pressure mining companies are currently facing due the economic pressures facing the mining industry. Such economic times call for a more sustainable approach when it comes to operations through efficiency and reduced maintenance expenditures whenever possible.
According to a report by Steve Bowditch, equipment protection expert at Chesterton, advanced technologies allow mining companies to address various abrasions differently considering factors such as velocity and impact. Technologies like ceramics, reinforced epoxies, thermal spray metal systems and urethanes provides miners with high class service in high abrasive and corrosive applications.
To deliver long term protection from wear, abrasion and corrosion, epoxy-based wear-resistant coatings containing ceramic fillers can be applied to vulnerable metal surfaces to protect them and minimize planned and unplanned downtime. These coatings act as a sacrificial and renewable working surface that preserves the structural integrity of the base substrate and prevents mechanical attack, chemical degradation, and corrosion caused by abrasive particles, slurries and chemicals. These engineered coatings can be applied to worn equipment for restoration or to new equipment before it is placed into service.
Wearing compounds are two-part epoxy systems containing ceramic beads or ceramic powder, and silicon carbide. The epoxy-base polymer that adheres the ceramic material to the substrate is formulated to be extremely robust, offering excellent performance under high compression and high impact loads. These coatings cure in temperatures between 55°F and 90°F with cure time dependent on mass and temperature. As a result of the exothermic heat generated by the epoxy reaction during cure, the larger the mass, the faster the cure. Higher substrate and air temperatures will also result in accelerated cure.
Ceramic coatings resist harsh chemicals and withstand temperatures to 550°F. According to B.E.A. Jacobs, author of Design of Slurry Transport Systems, because ceramic is inert, it does not react with most materials that come in contact with metal components. Ceramic coatings resist harsh chemicals and withstand temperatures. The size of the ceramic material-powder or bead, used in the wear resistant coating directly corresponds to the size of the particulate that will ultimately damage metal components. For large particulates and stones, coatings with the largest available ceramic beads are most effective. For fine slurries or wastewater, fine powder ceramics are sufficient to inhibit damage.
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Application
Application is a very crucial part of the maintenance process. According to J. Adam Lyman an application engineer for Henkel Corporation, fast-set materials are used when equipment and parts need to return quickly to production. These compounds cure to functional strength in as little as three hours, often at lower temperatures than other ceramic coatings.
Brush-on coatings are self-leveling, low-viscosity materials that can be applied with brushes or rollers, or simply poured onto a substrate and allowed to coat the desired area. Brushable coatings will reduce friction on equipment like fluid pumps that carry small particulate slurries with very fine particles such as sand, metal chips or shells. These coatings can easily be applied to areas that are out of arm’s reach, for example the inside of pipes.
Sprayable coatings are low viscosity materials similar to brush-on materials that achieve just 0.5mm thickness. Using a spray gun equipped with an atomizing mix tip, these ultra-thin coatings can be applied overhead, used to cover large application areas or distributed onto hard-to reach, intricate and small-diameter components. Because these coatings are so thin and the ceramic powders used in them are so fine, they should not be exposed to high turbulence or impact. Fluids should contain no aggregates or slurries, although sand and fine particulates are acceptable. Excellent applications for sprayable ceramics coatings include augers, screens, grates, curved components, elbows and the insides of tanks and vessels.
Impact resistant coatings are specially formulated to absorb shock and withstand damage from medium to large sized aggregate such as rocks, coal and other substances falling onto or striking a substrate. These materials are often found protecting chutes at the end of conveyor belts.
