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WEAR PROTECTION 36 E&MJ; • FEBRUARY 2018 www.e-mj.com Plan Before Buying Apart from selecting the best anti-wear material for a specific site need, another effective ploy is to identify a type or brand of equipment intentionally designed to be wear-resistant. Case in point, as il- lustrated by process equipment supplier Weir Minerals: Centrifugal pump impeller vanes are designed to meet the incoming flow and accelerate the fluid. A problem occurs when the slurry approaches the impeller of the slurry pumps, as there is an abrupt change in flow direction. The small, fine particles follow the fluid as it transitions from the pipe into the impeller, but the large particles do not. They continue to move in a straight line, impacting the vane-leading edge as the slurry moves through the impeller. The high relative velocity between the rotating vane and the incoming particles results in leading-edge wear on the impeller. Loss of vane length due to impacting of the large particles results in a loss of pump performance. Eventually the pump will no longer be able to generate the head and flow required for the duty and the impel- ler will need to be replaced. After experts at Weir Minerals wit- nessed this problem repeatedly in mineral processing plants, and wanted to improve the wear performance of its Warman mill circuit pumps, a company engineering team devised an innovative solution to decrease the impact wear on the vane leading edge — the Warman throatbush with pre-swirl vanes. The pre-swirl vanes change the flow of the slurry, swirling it in an counterclock- wise direction, with the rotation of the im- peller, before it enters the impeller. This induced rotation of the incoming flow reduces the relative velocity between the impeller vanes and the slurry. Pre-swirl vanes at the bottom of the throatbush are positioned with a greater angle of twist than those elsewhere on the throatbush. This is to provide the larger particles with a greater tangential veloci- ty. Varying the pre-swirl angle in this way ensures that the relative velocity between the large particles and the vane-leading edge is minimized while at the same time maintaining the correct impingement an- gle of the fluid on to the vane. Elsewhere, conveyor equipment sup- plier ASGCO recently added Semi-Ceram- ic Pulley Lagging to their pulley lagging product line. The addition of Semi-Ceram- ic Lagging allows the company to offer a product range that provides customers with a choice between full ceramic coverage for a high-tension drive pulley, as well as less than full (40%) coverage with for smaller pulleys, non-drive pulleys and bend pul- leys. The new lagging product, according to the company, provides a solution when conventional rubber lagging wears prema- turely. ASGCO explained that the ceramic tiles are embedded in rubber on all sides and separated by a horizontal groove for channeling water and dirt, and a unique backing method provides exceptional bonding for rubber-to-metal applications. Plan After Buying Eventually, even the toughest wear com- ponents become damaged or reach the effective end of their service lives and re- quire replacement. When it comes time to perform a planned shutdown, the stakes can be high, with significant dollars linked to each minute of downtime. Coordinating all the resources, equipment, tools and parts to keep everything on track can be challenging for even the most experienced team. Metso recently listed four key ac- tions that need to be considered. Baseline Performance – Assessing shut- down performance and understanding where delays occur is critical. With so much going on during a planned shutdown, it is not realistic to catch and record every improvement opportunity. But what if one could record an entire shutdown and then review it to find every delay? It can be done if one has the right tools and expertise. A lean production tool called Single Minute Exchange of Dies (SMED) or time and mo- tion analysis, frequently used by mining companies, uses time-lapse video sequenc- es to examine repetitive tasks, such as mill and crusher relining. Cameras are strategi- cally positioned to capture the entire pro- cess. Maintenance and reline experts then analyze the video sequences to highlight issues and recommend improvements. Evaluate Tools – Maintenance on crushing and grinding equipment can be hazardous to crews without the proper tooling. Having the right tools that can facilitate maintenance while improving safety is another important element to maximize performance. Observations from shutdown crews or data collected from a formal SMED analysis are used to develop special tooling that will save time and mit- igate safety risks. The customized tools listed below can be a better solution: • Customized concave setting fixtures for gyratory crushers • Special liner lifting devices for Vertimills • Concave removal trays for crushers • Custom work platforms, stands and ladders Plan, Share and Execute – Small plan- ning adjustments can make the difference between a successful changeover and one that runs hours over schedule. Planning is about making sure that all resources, parts, and tools are available to execute work in a safe and optimal manner. This includes having the right checklists on hand such as pre-planning, tools and previous shutdown checklists. Prior to execution, sharing the plan with the entire team can help raise and solve any unanswered questions. A plan is only useful if everyone is on the same page. Executing the plan is easiest when everyone knows what needs to be done ahead of time. When last minute decisions are eliminated, safety risks and delays are minimized. Review to Improve – Even after a suc- cessful shutdown has been completed, it doesn't end there. One of the most im- portant things to do once the shutdown is completed is to take a step back and once again assess performance by holding a post mortem analysis. Did everything go according to plan? Were there any new safety concerns? How did the shutdown compare to the last one? Were there other unforeseen delays or other issues? In some cases, new problems and possible solu- tions can be easily identified. In other cas- es, another SMED analysis may need to be done. In any event, holding a post mortem to assess performance and set targets for the next shutdown is often a neglected step, but if done right can be served as a cornerstone to continuous improvement. Weir Minerals now includes these pre-swirl vanes in its Warman pump throatbush to reduce internal impact wear.