Rock Products

MAR 2013

Rock Products is the aggregates industry's leading source for market analysis and technology solutions, delivering critical content focusing on aggregates-processing equipment; operational efficiencies; management best practices; comprehensive market

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Page 62 of 99

MAINTENANCE WEAR PARTS The feed material may contain hard quartz and/or silicates with hardnesses ranging from 600���1,250 HV. As the hard��� ness of the feed material exceeds that of the carbides in the iron, it slowly gouges and thus removes iron, until it meets the ceramic constituent. Because the ceramic is 1.5���2 times as hard as the abrasive feed material, it fortifies the iron and greatly impedes the ability of the quartz and silicates to gouge and remove iron. Over time the ceramic material will wear, but just as a shark replaces its teeth, Si���Tec com��� posites expose fresh ceramic to once again fortify the high��� chrome iron. The combination of two durable constituents results in a composite, which is longer lasting than either of the com��� posite constituents individually. This is proven with field data collected by an operator running vertical shaft impact (VSI) crushers outfitted with Si���Tec impeller shoes. In VSI crusher applications, ceramic composites resist wear from impact and sliding abrasion of rock as it is dropped through the feed chute on to a rotating table covered with a protec��� tive feed disc and is hurled centripetally by the impeller shoes to crash into surrounding wear parts. Tests were run with both unfortified high���chrome iron and Si���Tec high���chrome iron/ceramic composite shoes. The data measured impeller shoe wear life in terms of hours of operation for a specific feed size and material. As in many crusher processes, a jaw crusher was used as the primary crusher. Following the jaw, the output is screened to control feed size into the VSI. In this example, the feed is very hard and thus highly abrasive to high��� chrome iron. Four separate batches were run using four unique impeller shoe sets. The first batch was crushed using an unfortified high��� chrome iron shoe. The next three batches were crushed using composite shoes each with a unique ceramic profile, Gen I, II or III (see Table 1). The differences between these three iterations are the locations of the ceramic con��� stituent. The design iterations are the result of introducing an initial ceramic profile, studying the resulting wear pat��� tern and then designing successive ceramic profiles to bet��� ter fortify the iron and optimize wear life. the unfortified high���chrome iron shoes. The image below (Figure 2) shows an example of each of the iterations after crushing operations were completed. The unfortified shoe (shown on left) has a narrow wear pattern associated with focused erosion deep into the body of the shoe. At this point, production was stopped so that the shoe could be replaced to avoid damage to the shoe brackets. In this very abrasive application, the unfortified shoe was re��� moved after four hours of operation. The three shoes to the right in the picture were fortified with successive iterations of Si���Tec ceramic composites. While all three have wider wear patterns than the first, the most impressive is the right���most shoe, Gen III. After 15 hours of crushing, this shoe has the widest and shallowest wear pattern, and as a result, the longest wear life. The iron/ceramic composites wear longer, which translates to longer wear life and fewer change outs. Further, there is a commercial comparison based not simply on the cost per impeller shoe, but shoe cost per hour of operation. This analysis is shown in Figure 3 (page 62). When taking in to account the longer wear life and cost of the ceramic com��� posite shoes, an analysis of the shoe cost per operation hour shows a significant advantage associated with the use of Si���Tec wear parts. While results are likely to vary with feed type, feed size and machine configuration, in this application, the relative shoe cost per hour of operation of the Si���Tec Gen III is one���third that of the unfortified high���chrome iron. Conclusion Si���Tec Ceramic Composites are very effective at resisting wear in impact crusher applications where the wear com��� ponents are exposed to medium impact loading and intense sliding abrasion. It is the addition of ceramic material to the high���chrome iron that fortifies the metal matrix against the abrasive silicates and quartz feed. Figure 2 The additional hours of crushing are the result of a more uniform wear pattern with the Si���Tec composites than with Table 1 Si���Tec Gen I 10 Si���Tec Gen II 12 Si���Tec Gen III 15 Si-Tec�� Gen III 4 Si-Tec�� Gen II High���chrome iron Si-Tec�� Gen I HOURS OF OPERATION Standard IMPELLER SHOE ITERATION ROCKproducts ��� MARCH 2013 61

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