SKF Cooper split roller bearings and bearing units

1 Overview, selection and application recommendations Sealing The purpose of a seal is to retain lubricant and prevent any contaminants from entering a controlled environment. Seal selection criteria Seals for bearing applications should provide maximum protection with a minimum amount of friction and wear, under the pre- vailing operating conditions. Because bear- ing performance and service life are so closely tied to the effectiveness and cleanli- ness of the lubricant, the seal is a key component. Many factors must be considered when selecting the most suitable seal for a par- ticular bearing-shaft-housing system. These include: • the contaminant type: particles or fluid or both • the circumferential speed at the seal lip • the shaft arrangement: horizontal or vertical • available space • seal friction and the resulting temperature increase • environmental influences • cost Seal types SKF offers a variety of sealing solutions for split roller bearing units ( table 7 , page 17 ). Custom seals and seals of non-standard materials are also available on request. Aluminium triple labyrinth seals Aluminium triple labyrinth seals have O-rings which compress against the shaft and cause the seal to rotate with the shaft ( fig. 15 ). The amount of compression is designed so that the shaft moves through the seal when axial expansion occurs in non-locating bearings. Alignment feature The cartridges in split bearing units have a spherical outer surface that fits into a con- forming surface in the housing in the form of a ball and socket joint. If any shaft misalign- ment is present, the cartridge, seals, and bearing stay together, maintaining the seals on an axis parallel to the shaft ( fig. 16 ). Without this feature, contact between the seal and the shaft is lost on one side when even small amounts of misalignment occur, and sometimes a gap may open. On the other side, the seal presses heavily against the shaft and wears quickly. As a result, the sealing effectiveness is compromised. With up to 2,5° permissible misalignment of the housings, extremely close tolerances can be maintained between the housing and the shaft resulting in an effective sealing element. Fig. 16 Alignment feature Fig. 15 Labyrinth seals Seal remains parallel to the shaft 16