Aggregates Manager Digital Magazine
Issue link: http://read.dmtmag.com/i/945822
AGGREGATES MANAGER / March 2018 33 EQUIPMENT MANAGEMENT T he primary gyratory design has been in operation for over a cen- tury and has evolved and proven to be a robust, reliable, and long-lasting piece of equipment when designed, op- erated, and maintained correctly. Gyratory crushers are compression crushers with a two-bearing design (spider and eccentric bearings). They are relatively slow with minimal moving components, and feature a large size, but relatively conservative, crushing kinematics. In short, they make for a relatively simple, reliable crusher. There are many best practices that have been learned throughout the life of this design, and some of these have mani- fested themselves in regular, preventive maintenance habits. All crushers are designed with a target power and force limit, and keeping the machine within these limits is a signifi cant factor in achieving long lasting, reliable operation. The power limit is given for a crusher and its throw/speed combination; exceeding that power limit and/or assuming an incorrect power limit can put stress and possible damage on drive components and bearings. (Not all crushers are the same, and even two 42-65 Allis Chalmers Superior gyratory crushers built in 1974 may not have the same power rating.) The force limit is sim- ilar to the power limit; however, it is not always proportional and is independent of throw and speed. Over-force conditions can be monitored by high power draw and/or dropping of the mainshaft during overload events; these events cause stress on bearings and structural components. The highest cost, regular maintenance item is replacement of the crusher mantle and concaves. It is important that the profi le of the mantle and concaves are matched to achieve desired open-side setting (OSS) while remaining within power/force limits. This is especially true when running multiple mantles of various size during the life of the concaves. Running with mismatched liners is a common cause of high power and force spikes — or the less noticeable force con- centrations — that will reduce component life. Furthermore, the liner profi les are designed for a specifi c OSS, and raising and lowering the mainshaft signifi cantly away from this setting can have the same effect of power/force overloads. It is rec- ommended to review the mantle/concaves in use periodically throughout the life of the plant to ensure the wear parts are Guidelines for Your Gyratory Use these best maintenance practices to ensure optimal performance and long life of your crusher. Regular inspection of upper and lower bushings, as well as oil analysis, will help protect the life of your gyratory.