SKF - Rolling Bearings

Design considerations
Mechanical seals
Mechanical seals († fig. 64) are used to seal
grease or oil lubricated applications where
speeds are relatively slow and operating conditions
difficult and arduous. They consist of
two sliding steel rings with finely finished sealing
surfaces and two plastic cup springs (Belleville
washers), which position the sliding
rings in the housing bore and provide the
neces sary preload force to the sealing surfaces.
There are no special demands on the
mating surfaces in the housing bore.
Other seals
Felt seals († fig. 65) are generally used with
grease lubrication. They are simple, costeffective
and can be used at circumferential
speeds of up to 4 m/s and at operating temperatures
up to 100 °C (205 °F). The counterface
should be ground to a surface roughness
R a ≤ 3,2 μm. The effectiveness of a felt seal
can be improved substantially by mounting a
simple labyrinth seal as a secondary seal. Before
being inserted in the housing groove, felt
seals should be soaked in oil at about 80 °C
(175 °F) prior to mounting.
Metal seals († fig. 66) are simple, costeffective
and space-saving seals for grease
lubricated bearings, particularly deep groove
ball bearings. The seals are clamped against
either the inner or outer ring and exert a resilient
axial pressure against the other ring. After
a certain running-in period, these seals become
non-contact seals by forming a very
narrow gap with the rotating ring.
For additional information about seals supplied
by SKF, refer to Power transmission seals
(† skf.com/seals).
Fig. 64
Fig. 65
Fig. 66
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