Whatever the bearing arrangement, it consists not only of the bearings but includes associated components. Besides shafts and housings these associated components include the sealing, the performance of which is vital to the cleanliness of the lubricant and the overall service life of the bearing arrangement. For the designer, this means that bearing and sealing arrangement should be viewed as an integrated system and should be treated as such.
Where seals for rolling bearings are concerned, a distinction is made between seals that are integral with the bearing and those that are positioned outside the bearing and are separate from it. Sealed bearings are generally used for arrangements where a sufficiently effective external seal cannot be provided because there is inadequate space or for cost reasons.