Industrial seal self study guide - SKF.com

HM14
SKF’s non-spring loaded designs (fig. 3a).
HDW1 CRW1 CRWA5
CRWA1
CRWHA1
HM21
FF G HD
TL
HMA
HMS4
SKF’s standard spring-loaded
designs are typically used to retain
oil and/or exclude dirt in higher
shaft speed applications (fig. 3b).
CHAPTER 3—
SEAL DESIGN GROUPS
Basic Design Groups
Seals with similar functional abilities are categorized into design
groups. Note that design codes are unique to each manufacturer,
and the ones listed below are codes used by SKF.
Non-Spring Loaded Seals
These seal designs are typically used for grease retention or dirt
exclusion in slower shaft speed applications.
The seals illustrated in fig. 3a, HM14 and HM21, are SKF’s standard
designs. Agricultural equipment and quarry conveyor systems are
typical uses. They can also be used as light-duty rod wipers. Other
designs include FF, G, HD, HMA and TL. The heavy-duty TL seal is
designed for severe conditions such as disc harrows. For maximum
dirt exclusion, they should be installed with the lip facing outward.
Non-spring loaded seals are not intended for lube oil retention.
Non-spring loaded seals, especially the HM design, are generally
less expensive than spring-loaded versions, and generally cost much
less than the assembled seals they replace. They also provide a good
level of performance when sealing grease.
Spring-Loaded Seals
These seal designs are typically used to retain oil and/or exclude
dirt in higher shaft speed applications (fig. 3b). SKF’s standard designs
include: single lip, dual-lips, and single and double shell designs.
The dual-lip design features a non-interference auxiliary lip for added
exclusion protection without the heat build-up associated by traditional
dual-lip designs. Typical applications include gearboxes, speed reducers,
transmissions, motors and drive systems. CRW5 and CRWA5 types
are designed for high pressure applications, up to 90 psi (.62 MPa).
For maximum dirt exclusion, they should be installed with the lip facing
outward. While this works well with grease, be aware of potentially
high levels of oil leakage. The large diameter seal HDW1 type is
designed for severe conditions.
Spring-loaded seals provide longer, more consistent service life
in radial applications than non-spring loaded designs, and better
sealability over a wide range of conditions. They also perform
exceptionally well in applications where there is shaft run-out
and shaft-to-bore misalignment.
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