Industrial shaft seals

gab.ru Берг АБ bergab@ya.ru Тел. (495)-228-06-21,
Industrial
факс
shaft seals
(495) 22
Operating temperatures
Low as well as high temperatures influence the
effectiveness of seals. At low temperatures, the
sealing lip will lose its elasticity and become
hard and brittle. Sealing efficiency will
decrease and the seal will become more
susceptible to mechanical damage. The static
seal between the seal outside diameter and
the housing bore may also be affected if the
materials are different and shrink at different
rates. To avoid such problems when aluminium
alloy housings are used, for example, radial
shaft seals with an elastomeric outside
diameter are recommended.
Friction, the circumferential speed of the seal
lip, temperature, the viscosity of the medium
being sealed as well as the specific heat
transfer along the shaft all influence the
temperature at the sealing position and the
temperature between the lip and lubricant film
on the counterface. High temperatures
generally lead to a breakdown of the lubricant
film. Lack of lubrication is one of the most
common causes of premature seal failure.
For applications where temperatures are
continuously high, special high-temperature lip
materials should be used, e.g. SKF LongLife
seals of fluoro rubber (FPM) or
polytetrafluoro-ethylene (PTFE).
To illustrate the thermal resistance of the
various materials normally used by SKF, the
permissible operating temperature ranges are
shown in Diagram 3.
Diagram 3
Leather
Nitrile rubber
Duralip (X-NBR)
Duratemp (H-NBR)
Polyacrylate elastomer
Silicone rubber
Fluoro rubber
Polytetrafluoro-ethylene
-80
-60
-40
-20
0 +50 +100 +150 +200 +250
Temperature, °C
gab.ru Берг АБ bergab@ya.ru Тел. (495)-228-06-21, факс (495) 31 22