Improved roller bearing design offers extended operating periods and greater reliability for high pressure grinding rolls
A. Bierlein, M. Stützlein, Schaeffler Technologies AG & Co. KG, Schweinfurt, Germany
Schaeffler has completely revised its 241 series of spherical roller bearings from a bore diameter of 500 mm upwards with the aim of extending the roller presses’ operating periods and increasing their reliability. The design process for the new bearings also took the typical wear mechanisms that occur in the cement and mining industries into consideration. The result of these design modifications is an increase in load rating and, thanks to the logarithmic rolling element profiling, a significant increase in operating life when contamination with hard and abrasive particles from the production occurs. This article describes the wear mechanism in the presence of contamination and the resulting changes in the roller bearing’s load distribution based on the relationship between osculation and pressure distribution. In spherical roller bearings, abrasive wear caused by hard particles causes the maximum pressure to shift from the rolling element center to the rolling element ends, a phenomenon that is designated as “edge running”. Logarithmic profiling of the roller ends that has been specially adapted to this abrasive wear means that this edge running does not occur until a much later point in time. Wear to the bearing can then take place over a longer period. Cement mill operators thus benefit from longer mill operating periods and reduced numbers of unplanned production downtimes. The new contact geometry also generates less frictional power. Further features made it possible to increase the load ratings, which are determined using a certified method, by 15 % and thus extend the bearings’ nominal rating life. To prevent the ingress of foreign particles into the bearing to the greatest extent possible, a new seal has also been developed that is integrated into the bearing while leaving the design envelope unchanged. Spherical roller bearings in high pressure grinding rolls on which a high level of wear is detected can thus easily be replaced by the equivalent sealed variant.
Summary CEMENT INTERNATIONAL 04/2019 pp 36-41
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