Industrial shaft seals

gab.ru Берг АБ bergab@ya.ru Тел. (495)-228-06-21,
Industrial
факс
shaft seals
(495) 22
Lubrication
In order for a radial shaft seal to be able to
seal efficiently over a long period it is
necessary to lubricate the sealing lip. This
prevents actual lip counter surface contact and
reduces friction as well as wear to the lip and
counter surface. Dry running of sealing lips
made of standard materials should be avoided
at all costs. Because of this, the counter
surface should be coated with a suitable
lubricant when the seal is being installed, so
that the sealing lip is lubricated right from the
beginning.
The medium being sealed is not only
intended to lubricate the seal but also
transport the heat generated by friction in the
lip/counter surface contact. Thus, the medium
must be able to reach the sealing lip in
sufficient quantities from the very beginning.
In applications where the seal has to retain
oil or grease, lip lubrication is not normally a
problem. Some rolling bearings, e.g. angular
contact ball bearings, taper roller bearings and
spherical roller thrust bearings, as well as
gears, have a pumping action by virtue of their
design. This means that the sealing lip can
either be starved of lubricant or be subjected
to excessive quantities of lubricant. In both
cases steps need to be taken at the design
stage in order to ensure that lubricant actually
reaches the contact, or that excess quantities
are removed.
Where lubricant starvation has to be prevented,
lubrication ducts can be provided.
Where there is too much lubricant, a flinger
can be installed between bearing and seal.
When lubricants are not being sealed,
grease or oil must be supplied separately so
that the lip can be lubricated. In exceptional
cases and where seals with a secondary (dust)
lip or two sealing lips are used it may be
sufficient to provide an initial fill of grease
between the two lips.
Lubrication of paired arrangements
If two radial shaft seals are to be mounted in
a common housing bore either in tandem or in
a back-to-back arrangement, care must be
taken to see that neither of the sealing lips can
run dry at any time. To eliminate any risk of
dry running, the free space between the seals
or sealing lips should be filled with a suitable
lubricating grease.
To guarantee lubricant supply to the sealing
lips in operation and to prevent dry running,
the use of a spacer ring between the two seals
is recommended. This ring should be provided
with lubrication holes or an annular groove
and lubrication holes (fig 44), so that grease
can be supplied to the space between the
sealing lips, e.g. via a grease nipple.
gab.ru Берг АБ bergab@ya.ru Тел. (495)-228-06-21, факс (495) 67 22
Fig 44