With the AIP (Asset Impro vement Programme), NSK has developed a service aimed at increasing roller bearing lifetime in operation. A case study from the quarrying and mining industry shows how this can lead to successes and lower costs. A quarry operator approached the NSK engineers, because the casing bearings on a vibrating screen frequently failed. Bearing failures were detected after an average of 440 hours of operation, that is after around two months. It was soon established that the damage was caused by the extremely severe environment. Besides wetness and high mechanical stresses, wear was accelerated by the bearings sometimes being covered completely with sand, which then ingressed into the bearings and damaged the races and balls. The premature failure was all the more exasperating because the bearings were difficult to access so that replacement took a long time. The need for replacement parts, cost of installation and downtime led to additional costs of around 3300 € per year for just this one installation.
The NSK engineers looked at the environmental conditions and proposed replacement of the roller bearing with Self-Lube® Triple Lip Seals (Fig.). These seals provide maximum protection in applications with the highest degrees of contamination. The Triple Lip seal consists of a one-piece moulded nitrile seal with three sealing lips, bonded to a protective steel outer pressing, which is robustly secured in the outer ring of the bearing. This is supplied pre-lubricated and sealed and is also equipped with a re-lubrication system. The outstanding sealing efficiency of the triple lip seals is demonstrated in this typical application. The new casing bearings have been in use without failure for nineteen months since their installation and have now completed 4400 hours of operation. That corresponds to ten times the lifetime of the original bearing. This reduces the estimated costs for maintenance and servicing of the bearing to 330 €, and the operator can save 2970 € a year.