Datasheet

© Freudenberg Simrit GmbH & Co. KG | Technical Manual 2007 565
Technical Principles | O-Rings and Static Seals
Further Technical Notes
Fitting
The entire system should be cleansed of dirt and
processing residue prior to fitting of the ISC O-Rings.
ISC O-Rings should not be pulled over sharp edges,
crooked shafts, threads, grooves, etc. It is recommend-
able to cover the sharp transitions when mounting in
order to avoid damage.
The ISC O-Ring may not be positioned distorted – twist-
ed – in the mounting groove. A brief elastic expansion
is permissible when mounting. The ring must, however,
be allowed time to return to its original shape after fit-
ting. Caution is urged during the fitting of piston or shaft
seals with an outside diameter of less than 10 mm due
to the greater relative expansion.
The use of a pilot shaft or a mounting sleeve is recom-
mended.
Elongation and compression
The permanent elastic expansion should not exceed
6%, as otherwise too great of a diminution and a too
extreme of a flattening out of the ISC O-Ring cross-sec-
tion will occur → Diagram 3.
The compression of the ISC O-Ring should not exceed
3%, as otherwise there is a danger of the ring warping
and shearing off when mounting.
The stated values for elongation and compression are
theoretical values that are not always adhered to in
practical applications. Especially with greater elonga-
tions, the ISC O-Ring installation space must be modi-
fied accordingly in order to adequately allow for cross-
sectional changing of shape under pressure.
Fig. 11
Forces required for a cross-sectional shape
change under pressure
The values stated in → Diagram 4 can be applied to
other materials from Simrit, according to the Shore
hardness, for an estimation of the order of magnitude.
The necessary force for changing shape depends on
the material hardness. Utilising the same material,
it rises linearly with increases in ring thickness.
The values are to be viewed as reference values,
according to which the overall force to be used for the
static fitting of ISC O-Rings can be determined. They
should not, however, be used to determine the frictional
forces for the dynamic pressurising of ISC O-Rings.
(The effects of the environmental conditions such as
tolerances, temperatures and coefficient of friction are
too great to be able to make a definitive statement.)