Rotary Seals - Dilanda.it

Radial Oil Seal
Sealing element
Materials
The demands made on the material must take into account
the environmental conditions and the function of the seal.
Some of the requirements associated with environmental
considerations are:
- Good chemical resistance
- Good resistance to heat and low temperature
- Good resistance to ozone and weathering
The functional demands include:
- High resistance to wear
- Low friction
- Low compression set
- Good elasticity
In addition, cost considerations render good processability
a desirable feature. No material is available today which
satisfies all these requirements. The choice of materials is
therefore always a compromise between the relative
significances of the factors involved.
Type and designations of materials
Nitrile rubber
Acrylic rubber
Silicone rubber
Fluorinated rubber
Hydrogenated Nitrile rubber
(NBR)
(ACM)
(VMQ)
(FKM)
(HNBR)
A further development of the Nitrile rubber has led to the
so called hydrogenated Nitrile rubber (HNBR). The heat
and ozone resistance is significantly better. This material
can replace Acrylic rubber and in certain cases also
Fluorinated rubber. In order to satisfy the wide range of
demands made on seals, a special composition has been
developed for each type of rubber. Other compositions are
also available to meet some extreme requirements.
Table V
Material recommendations
Materials
for sealing common media
Acrylonitrile
Butadiene
Rubber
NBR
Fluoro carbon
Rubber
FKM
Material designation
Polyacrylate
Rubber
ACM
Material Abbreviation
Silicone
Rubber
VMQ
Hydrogenated
Acrylonitrile
Butadien Rubber
HNBR
N V A S H
Max. permissible constant temperature (°C)
Engine oils 100 170 125 150 130
Transmission oils 80 150 125 130 110
Mineral
fluids
Flame retardant
hydraulic fluids
(VDMA 24317)
(VDMA 24320)
Other media
Hypoid transmission oils 80 150 125 - - 110
ATF oils 100 170 125 - - 130
Hydraulic fluids (DIN 51524) 90 150 120 - - 130
Greases 90 - - - - - - 100
Oil-water emulsion 70 - - - - 60 70
Water-oil emulsion 70 - - - - 60 70
Aqueous solutions 70 - - - - - - 70
Water-free fluids - - 150 - - - - - -
Fuel oils 90 - - - - - - 100
Water 90 100 - - - - 100
Lyes 90 100 - - - - 100
Air 100 200 150 200 130
Due to the different configurations of the media, the
above-mentioned temperature ranges are for guidance
only. Depending on the medium, significant deviations may
occur.
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Edition April 2006
19