Single direction angular contact thrust ball bearings can be supplied with an integral non-contact seal fitted on each side (designation suffix 2RZ, fig. 1
). The seals form an extremely narrow gap with the inner ring shoulder and therefore speed capability is not compromised.
Double direction angular contact thrust ball bearings are sealed as standard. They can be supplied with a contact seal (designation suffix 2RS, fig. 2
) or a non-contact seal (designation suffix 2RZ, fig. 3
) fitted on each side. Non-contact seals form an extremely narrow gap with the inner ring shoulder and therefore speed capability is not compromised.
The various seals are made of an oil- and wear-resistant NBR and are reinforced with sheet steel. The permissible operating temperature for seals made of NBR is –40 to +100 °C (–40 to +210 °F)
. Temperatures up to 120 °C (250 °F)
can be tolerated for brief periods. For additional information about the materials, refer to Seal materials
Cartridge units are protected on both sides with laminar rings (fig. 4) to prevent both the ingress of contaminants and the egress of grease. These seals do not limit the attainable speed for the single direction angular contact thrust ball bearings within the unit.
Sealed bearings are filled as standard with a high-quality, low-viscosity grease that has a lithium soap thickener and either a mixed ester/PAO base oil (for single direction bearings and cartridge units) or an ester base oil (for double direction bearings). The quantity of grease fills ~ 25 to 35% of the free space in the bearing. The temperature range for the greases are:
–40 to +120 °C (–40 to +250 °F) for single direction bearings
–55 to +110 °C (–65 to +230 °F) for double direction bearings
Under normal operating conditions, the service life of the initial fill will outlast the bearing. If double direction bearings have to accommodate heavy loads and run for long periods at high speeds, relubrication may be necessary. When relubricating, the grease should be applied slowly while the bearing is rotating at normal operating temperature. Excessive pressure should be avoided as this could damage the seals.
Sealed bearings should not be washed or heated to temperatures above 80 °C (175 °F). If a sealed bearing is to be heated for mounting, an induction heater must be used and the bearing should be fitted immediately.