Industrial seal self study guide - SKF.com

V-Ring excludes contaminants,
prevents them from entering
bearing cavity (fig. 4a).
Non-spring-loaded HM seal is a
cost-effective design for grease
retention. Note that the lip faces the
lube in this application (fig. 4b).
Chapter 4—
Seal Applications
Seal Selection by Application
When selecting a seal for a specific application, it is important to know
what the seal is supposed to do and what operating conditions are
present. Common types of applications and seal designs recommended
for them are covered below.
Seals for Contaminant Exclusion
In steel mill or work roll applications, an abundance of contaminants—
scale, water spray, abrasive particles—are usually present. The seal’s
primary function is to exclude contaminants and prevent them from
entering the bearing cavity.
A back-up excluder seal, such as a V-Ring, is recommended (fig 4a).
The V-Ring can function as the primary seal or, in applications where
there is excessive contamination, it can provide protection for the
primary sealing element, increasing its life and reliability.
The V-Ring is designed to exclude dust, mud, water and most
contaminants, and can handle pressures up to 10 psi/.07 MPa (static)
or 3-5 psi/.02-.03MPa (dynamic). An all-rubber design, it stretches (up
to 2-1/2 times its diameter) over the shaft, easing installation.
As the seal rotates with the shaft, centrifugal force provides a “flinger”
effect, keeping out dust, mud, water and most contaminants. Exclusion
seals can be installed axially against any suitable counterface (bearing,
other seal, pillow block, bearing assembly or other housing). They
generally do not require lube for normal operating conditions.
Seals for Grease Retention
Grease lubricated applications, such as electric motors or small trailer
wheels, are generally easier to seal than oil lubricated applications.
When cost is also a factor, a non-spring loaded seal such as an HM
design, is usually the most cost-effective design for grease retention.
(fig. 4b).
The HM seal design retains grease at shaft speeds up to 2000 fpm,
(10.16 m/s) and handles pressure up to 3 psi/.02 MPa. It should be
installed with the lip facing the grease, except in applications where
grease purge is desired. In “purge”-type applications, the lip should
face away from the grease lube.
In grease retention applications where contaminants are present,
a V-Ring can also be installed as a back-up excluder.
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