SKF - Industrial Shaft Seals

Metal face seals
Permissible operating
conditions
Depending on their design, metal face seals can
withstand different amounts of internal pressure.
It should, however, generally be maintained
below 0,25 MPa (35 psi). Other recommendations
regarding operating conditions for the
metal face seals, like temperature and speed,
are provided in table 1.
The chemical resistance of the nitrile and
fluoro rubber in general is dealt with in the
section Chemical resistance on page 35.
Permissible operating conditions
Operating
Recommended value
condition
Table 1
Temperature, max
Continuous operation
Nitrile rubber (NBR) –25 to +100 °C (–15 to +210 °F)
Fluoro rubber (FKM) –10 to +190 °C (15 to 375 °F)
Circumferential
speed, max
Continuous operation 1,8 m/s (350 ft/min)
Brief periods 3,8 m/s (750 ft/min)
Contaminants
Metal face seals are often used in heavily contaminated
environments, where mud packing
in the cavity between the housing, sealing rings
and Belleville washers can occur. Eventually, the
mud packing can cause the Belleville washers to
be pushed out of position, resulting in improper
face loads or mud being pumped past the
Belleville washers.
Contaminants can also cause abrasion to the
Belleville washers, which in turn causes deteri oration
of the elastomer. To minimize the risk of
seal failure due to this deterioriation, it is critical
to select a proper Belleville washer material for
the application in question.
Installing HDDF seals
General
Careful handling and installation of a metal face
seal is critical to avoid cutting or tearing of the
elastomeric Belleville washers or breaking the
metal sealing rings, both which can cause premature
seal failure and immediate leakage. It
is also vital to keep the sealing faces free from
contaminants like dirt or lint. Always carefully
observe installation instructions provided on
page 383.
Housing and seal preparation
All housing components contacting the Belleville
washers must be free from contaminants (oil,
grease, dust, lint particles etc.) when installing
the seal. SKF recommends using a non-petroleum
based solvent and a clean, lint-free wipe
to clean these components prior to installation.
All seal parts must be handled with care to
avoid damage or scoring.
Pressure, max
Continuous operation 0,25 MPa (35 psi)
Brief periods 0,35 MPa (50 psi)
382