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At
one time, automotive air conditioning systems relied
on R-12, a chlorofluorocarbon (CFC) refrigerant.
But because studies have shown that CFC’s
contribute to ozone depletion in the atmosphere,
a push was made in the 1990s to replace these CFC
refrigerants with hydrofluorocarbon (HFC) refrigerants.
R-12 was replaced by what is known as R-134a.
The
advent of R-134a, however, also necessitated the
use of different lubrication. This new lubrication,
in combination with higher operating temperatures,
forced seal designers to seek more resistant materials
for air conditioning seals. Hydrogenated
nitrile (HNBR) has proven itself effective
and has thus found wide use in automotive air conditioning
(AC) seals.
Some
older AC seals incorporated an O-ring for O.D. sealing. Figure
228 shows an example of this. Figure
229 shows a more modern design featuring
a bonded rubber
O.D. and fewer overall components. Both designs
feature a primary
lip made of HNBR and an exclusion lip made
of polytetrafluoroethylene
(PTFE).
AUTOMOTIVE
APPLICATIONS MAIN PAGE
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“Because
of the many ways in which shaft seals may be
configured, they are common in a wide variety
of automotive applications.”
Figures
228 & 229
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