Integral bearings seals
SKF supplies several bearing types capped with a seal or shield on one or both sides. These provide an economic and space-saving solution to many sealing problems. Bearings capped on both sides are supplied already greased and are generally considered virtually maintenance-free. Actual seal designs are described in detail in relevant product sections.
Bearings with shieldsBearings fitted with shields (fig. 1 and fig. 2) are used in applications where the operating conditions are dry and relatively clean. Shields are also used in applications where reduced friction is important due to speed or operating temperature considerations.
Shields form either a narrow gap toward the inner ring shoulder (fig. 1) or an effective labyrinth with a recess in the inner ring shoulder (fig. 2).
Bearings with contact sealsBearings with contact seals, referred to simply as seals, are preferred for arrangements where contamination is moderate and the presence of water or moisture cannot be ruled out, or where maximum bearing service life and minimum maintenance are required.
SKF has developed a variety of seal designs. Depending on the bearing type or size, the seal makes contact with:
For deep groove ball bearings, SKF has developed additional seal types:
- The SKF non-contact seal (fig. 9) forms an extremely narrow gap with the inner ring shoulder.
- The SKF low-friction seal (fig. 10, fig. 11) makes almost no contact with the inner ring, but provides very good low-friction operation.
- The SKF WAVE seal (fig. 12), a spring-loaded radial shaft seal designed for oil lubricated applications, is incorporated on one side of the bearing (→ ICOS oil sealed bearing units)
SKF bearing seals are generally made of an elastomeric compound that is vulcanized to a sheet steel reinforcement ring. Depending on the series, size and the application requirements, typical seal materials are:
- acrylonitrile-butadiene rubber (NBR)
- hydrogenated acrylonitrile-butadiene rubber (HNBR)
- fluoro rubber (FKM)
- polyurethane (PUR)
The selection of the appropriate seal material depends on the expected operating temperature and the lubricant that is applied. For permissible operating temperatures, refer to Seal materials.