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SHIELDS AND SEALS
A
shield (non-contact) or seal (contact) is often installed to retain
lubricant and to prevent contamination from entering the bearing
raceways. These are available in a variety of materials and
configurations. Standard shield and seal configurations are called
out in the individual bearing tables on pages 46-57. Please contact
a SWC bearing engineer to discuss any special
requirements.
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| SHIELDS AND SEAL
TYPES |
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Z TYPE
SHIELD This is the most common
type of shield. It is non-removable, being permanently staked to the
bearing outer race with a small gap of approximately .005 inches
between the inside diameter of the shield and the bearing inner
ring. Since there is no contact with the inner ring, the torque and
speed limitations are virtually unaffected and the performance of
the bearing is almost identical to that of an open bearing. Standard
material is 300 series stainless steel. Plastic fixed shields are
also available on a limited basis. Most SWC shielded bearings
have metal Z type shields.
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Single
Shield - Code Z
Double Shield - Code ZZ |
ZS TYPE
SHIELD The ZS shield is identical
to the fixed Z type shield, except that it is retained by an
external snap wire that locates in a groove inside the rim of the
bearing outer race. This is only an advantage if the user needs to
remove the shield after manufacture of the
bearing.
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Single
Shield - Code ZS
Double Shield - Code
ZZS
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TS TYPE
SEAL The TS type seal is made
from glass-reinforced teflon. It is retained by an external snap
wire to the bearing outer ring, but also lightly contacts the inner
race land. This gives a high degree of protection from
contamination, with a modest increase in
torque.
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Single
Seal - Code TS
Double Seal - Code TTS
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D TYPE
SEAL The D type seal consists of
a molded Buna-N rubber lip seal with a steel insert. This provides
maximum protection to the bearing against outside contamination.
However, the high pressure of the lip seal itself results in greatly
increased torque and friction losses that can cause heat build-up in
higher speed applications. The seal material itself is rated to a
maximum of 250
°F. This type of seal is only available for
larger-sized bearings (R3 and above)
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Single
Seal - Code D
Double Seal - Code DD |
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