Industrial seal self study guide - SKF.com

SEAL DESIGN GROUPS (cont.)
HSF
SBF
All rubber seals do not score the
bore after repeated installations
and extractions. This prevents
damage to the metal that can
cause bypass leakage (fig. 3z).
Slotted washer installed between
seals provides room for extra
lubrication when needed (fig. 3aa).
A
SBF
B
SBF and HSF
The SKF family of all-rubber seals includes metal inserted (SBF)
and fabric reinforced (HSF) products (fig. 3z). The fabric-reinforced
series is available as solid round or with an open joint (split). When
required by customers, they can be used interchangeably with all
rubber HS types and are often found in imported heavy industry
machinery. The inserted SBF type is an alternative to solid HS or
HSF all rubber seals that eliminates the need for a cover plate.
All-rubber seals do not score the bore even after repeated installations
and extractions. This prevents damage to the metal that can cause
bypass leakage. All rubber-seals accept rougher bore finishes, reducing
machining costs. They are especially helpful for split housings. They
resist corrosion and will not seize in the bore even years after assembly.
Multiple Split Seat Installation
When split seals are used in multiples, it is necessary to separate the
seals and provide extra lubrication between them. For the best results,
a slotted washer should be fabricated and installed between the seals
(fig. 3aa). SKF does not supply slotted washers.
For best performance, multiple split seals should have staggered
butt joints, for example: one joint at 10 o’clock, the other at 2 o’clock.
V-Rings
The V-Ring is an all-rubber seal that mounts directly on the shaft
by hand, and is then pushed axially against a counterface, housing,
bearing race or similar surface. Usually made of nitrile or flouroelastomers,
other compounds may be obtained on special orders.
Designed with a long flexible lip, it acts like a mechanical face
seal, or a flinger. The V-Ring can be used as the primary seal or
as a back-up seal, to retain lubricants or exclude contaminants. The
V-Ring, which has very high surface speed capabilities, can run without
lubrication. Minimal friction and heat buildup results in extended seal
life. V-Rings running over 1600 FPM (8.13 m/s) may require axial
support and radial retention at even higher velocities.
Its design is based on three components: The body, a conical
self-adjusting lip, and a hinge. The elastic body adheres to the rotating
shaft while the actual sealing occurs at the point of contact between
the conical lip and counterface. The counterface can be the end of a
bearing, washer, suitable steel stamping or even the back of an
oil seal case. The V-Ring’s flexible hinge causes the sealing lip to apply
very light contact pressure against the counterface. Generally, fine shaft
or countersurface preparation is not necessary.
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