Industrial seal self study guide - SKF.com

SEAL DESIGN GROUPS (cont.)
HDSB
HDSB seal has both a spring-loaded
and non-spring loaded lip (fig. 3n).
HDSB
HDSB is similar to HDSA in that it also has a non-spring loaded
auxiliary lip combined with a spring-loaded lip (fig. 3n). The chamfer
on the auxiliary lip of the HDSB faces away from the spring-loaded
lip, permitting easier shaft insertion from the back. This eliminates
the need to reverse the direction of the auxiliary lip when the shaft
enters the seal. However, HDSB may be less effective in contaminant
exclusion due to the direction of the auxiliary sealing element.
Two designs are available. HDSB1 and HDSB2 both have
Spring-Lock, while HDSB2 also has Spring-Kover.
HDSC
For maximum exclusion of
contaminants, HDCS seal has an
auxiliary lip on the spring side of
the spring-loaded lip (fig. 3o).
HDSD
For separating two fluids, HDSD
has opposing sealing elements in
a single shell (fig. 3p)
HDSE
Where back-up sealing action
is desired, HDSE’s two sealing
elements serve as two seals in
one (fig. 3q).
HDSC
HDSC (fig. 3o) is similar to HDSA, but with one exception. The auxiliary
lip is placed on the spring side of the spring-loaded lip and faces the
same direction, providing maximum exclusion of foreign materials.
This style is recommended when excluding foreign materials is more
important than retaining lubricants. When HDSC is installed, both
sealing elements point toward the material being excluded. HDSC
should not be used in oil lubricated systems.
HDSD
Type HDSD has two opposing sealing elements in a single shell
(fig. 3p). That makes this design ideal for separating two fluids in
applications where two individual seals are impractical. Both sealing
lips in HDSD1 have Spring-Lock, while each sealing lip in HDSD2 has
Spring-Lock and Spring-Kover. HDSD can also be used to retain and
exclude.
There must be ample lubrication between the two sealing elements.
Pack the cavity between the lips with grease, or optional drill lube holes
from the O.D. to the I.D. for lubrication for sealing elements can be
provided by SKF.
HDSE
HDSE has two sealing elements with both lips facing in the same
direction (fig. 3q). This design is recommended in applications where a
back-up seal is desired for retention or exclusion, but there is no room
for two seals. HDSE1 features Spring-Lock on both lips, while HDSE2
features both Spring-Lock and Spring-Kover. If installed to exclude,
grease lubrication should be used for the bearings.
Lubricating the back-up lip is very important, since it could easily run
dry. The primary lip usually stays well lubricated from the fluid being
retained. SKF can provide HDSE with pre-drilled lube holes on the O.D.
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