Continuing its recent success in providing large split roller bearings for use in ball mills, Revolvo has won an order from a cement plant in Thailand to supply two large split roller bearings worth a total of £40,000. One is a standard 850mm bore unit, and the second, a special 849mm bore bearing to cope with an undersize shaft. Revolvo won the order because of its willingness to manufacture the special size bearing, and for the overall design of its SRB unit, with a brass instead of aluminium cage, which was considered more durable in the demanding conditions.
The SRB bearings are being used in a ball mill to crush limestone; the rock actually being fed through the bore of the bearings. The two SRB are replacement units for aluminium- caged split roller bearings which have been failing for some time. The problem with replacing these units has been the issue of an undersized shaft. Both bearing shafts should be 850mm but, due to wear and tear, one shaft is undersize at 849mm. This fact meant that the user either had to replace the shaft completely, a mammoth and costly undertaking, or find a supplier who would manufacture a special replacement bearing. The company searched widely for such a supplier, but it was only a chance logging- on to the Revolvo website that brought a solution.
In addition to its standard sizes, Revolvo manufactures larger, non-catalogue bearings in sizes up to 1500 mm. These "special" bearings are used extensively in process and extraction industries worldwide. Revolvo is able to produce these bearings due its turning capacity up to 1.8m and its new grinding capability to 1.5metres.
In common with all Revolvo´s SRB bearings the Thailand units are being supplied with machined brass cages. Revolvo´s cage design has CNC bored pockets that are optimised to give very accurate roller guidance, which prevents skewing, a condition that can lead to edge loading on the bearing and reduced bearing life.
In addition to providing excellent roller guidance, the Brass cage also allows operation at higher temperatures up to 140oC without problems, and operating speeds up to 25% higher, as long as thrust loads are within design limits. Overall, Brass is one the best cage materials as it absorbs lubricant and performs well in aggressive environments where lubrication is marginal.
The ability of SRB split roller bearings to perform reliably in aggressive cement applications is enhanced by the performance of the sealing systems available to protect the cartridge bearing units. Revolvo has developed a special labyrinth seal to exclude the fine, abrasive & hygroscopic cement dust, which is such a problem for equipment such as screw conveyors in cement plants. This solution provides much improved bearing reliability, and longer life with greatly reduced levels of maintenance.
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