SKF roller bearing units are available with different sealing solutions.
Table 1 provides an overview of the characteristics and suitability of each sealing solution. Details are provided in the following text. This information should be used as a guideline and does not substitute for testing a seal in its application.
TriGard seals (fig. 1) are standard with inch roller bearing units. These acrylonitrile-butadiene rubber (NBR) seals have the outside surface and seal lips vulcanized to a sheet steel insert. The seal consists of two lips that make contact with the mounting collar or bearing inner ring, and a third, non-contact lip, to protect the seal lips from coarse contaminants. The rubber coated outside circumference secures the seal in the housing and enhances the sealing effect.
As labyrinth seals do not generate friction, bearing units fitted with these seals are capable of relatively high speed operation.
For SKF ConCentra units, the labyrinth is created with three sheet steel rings (fig. 2). Two rings are fixed to the mounting collar or back-up collar and rotate with the shaft to act as flingers. The third ring is secured in the housing bore.
For collar-mount units, the labyrinth is created with two sheet steel rings (fig. 3). One ring is pressed onto the extended inner ring and rotates with the shaft, acting as a flinger. The other ring is secured in the housing bore.
Radial shaft seals (garter spring seals)
Collar-mount units can be supplied with radial shaft seals on both sides, on request (fig. 4). The seals are made of acrylonitrile-butadiene rubber (NBR) and have no metal reinforcement. They sit firmly in the housing bore providing a static seal. The spring-loaded seal lip provides a dynamic seal against the inner ring shoulder.
Bearing units mounted at the end of a shaft should have an end plug (end cover) (fig. 5). End plugs for units up to 2 15/16 inches are plastic, while larger sizes are steel. Bearing units with end plugs are identified by the designation suffix Y. For information about the permissible length of the shaft end, contact the SKF application engineering service.