径向骨架油封-Turcon Radial oil seal
Rotary shaft lip seals are components designed in a ring
form, fitted between machine parts in relative rotation,
with the function of separating oil or grease from the
inside and dirt, dust, water etc. from the outside.
The rotary shaft seals are generally composed of an
elastomeric diaphragm, shaped in a “lip form“ and
reinforced with a co-vulcanized metal insert. The sealing
lip is energized with a “Garter Spring“.
The sealing lip design corresponds to the current state of
art and is based on many years of experience in a wide
range of application fields.
The sealing edge can either be ready molded or trimmed
by mechanical cutting.
The total radial force of the sealing lip is given by
elastomer pre-tension together with tensile spring force.
The former depends on the deformation and elasticity of
the rubber material, geometry of the sealing lip and
interference between shaft and seal.
Material
Spring steel SAE 1074, DIN 17223 is normally employed. If
resistance to corrosion is required stainless steel AISI 304,
DIN 1.4301 is used. Garter springs of bronze or similar
materials are not recommended, since they tend to fatigue
after long service life or as a result of exposure to high
temperatures. In special cases the garter spring can be
protected against fouling by means of a thin rubber hose.
Type and designations of materials
Nitrile rubber (NBR)
Acrylic rubber (ACM)
Silicone rubber (VMQ)
Fluorinated rubber (FKM)
Hydrogenated Nitrile rubber (HNBR)
Compound
The material selected must take into account
environmental conditions and function requirements.
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 ease of processing a
desirable feature. Trelleborg Sealing Solutions can supply
the optimum material for each application.
Nitrile Rubber (NBR)
Advantages:
- Good oil resistance
- Good heat resistance up to 100°C in oil
- High tensile strength (special compounds over 20 MPa)
- High elongation at break
- Low swelling in water
Limitations:
- Poor weather and ozone resistance
- Poor resistance against polar fluids (ester, ether, ketones
and aniline)
- Poor resistance against chlorinated hydrocarbons (carbon
tetrachloride, trichlorethylene)
- Poor resistance against aromatic fluids (e.g. benzene,
toluene)
Fluids, mineral oils and above all high-alloyed mineral oils
(hypoid oils) containing larger quantities of aromatic
hydrocarbons have a high swelling effect on NBRcompounds.
The swelling behavior can be improved by
increasing the acrylonitrile content.
However an inferior cold flexibility and resistance to
compression set must be accepted. The additives in highalloyed
oils can in certain cases cause an additional
interaction between the elastomer and the additive, thus
influencing the elasticity.
Hydrogenated Nitrile Rubber (HNBR)
Advantages:
- Good oil resistance, also in hypoid oils
- Good heat resistance, up to + 150 °C
- Good mechanical properties
- Good weather and ozone resistance
Limitations:
- Poor resistance against polar fluids (esters, ethers,
ketones and aniline)
- Poor resistance against chlorinated hydrocarbons (carbon
tetrachloride, trichlorethylene)
- Poor resistance against aromatic fluids (bensene, toluene)
Polyacrylic Rubber (ACM)
Advantages:
- Good resistance against oils and fuels (better than Nitrile
rubber)
- Heat resistance about 50 °C better than for Nitrile rubber,
150 °C in oil and 125 °C in air
- Good weather and ozone resistance
Limitations:
- Not usable in contact with water and water solutions,
even smaller quantities of water in oil
- Limited cold flexibility to about -20 °C, somewhat poorer
than normal NBR
- Limited tensile strength and tear resistance, especially
above 100 °C
- Poor wear resistance (considerably inferior compared to
NBR)
- Poor resistance against polar and aromatic fluids and
chlorinated hydrocarbons
Radial Oil Seal
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Fluorinated Rubber (FKM)
Advantages:
- The resistance against oils and fuels is better than for any
other rubber type
- The only highly elastic rubber material, which is resistant
to aromatic and chlorinated hydrocarbons
- Excellent heat resistance, the best one after silicone
rubber, up to 200°C
- Excellent weather and ozone resistance
- Excellent acid resistance (only inorganic acids, not
suitable for organic acids e.g. acetic acid)
Limitations:
- Limited cold flexibility, to approx.-20°C to -25°C
- Limited tensile and tear strength, especially above 100°C
- High compression set in hot water
- Poor resistance to polar solvents
Silicone Rubber (VMQ)
Advantages:
- Best heat resistance of all rubber types
- Best cold resistance of all rubber types
- Excellent weather and ozone resistance
- Resistant against aliphatic mineral oils and most grease
types
Limitations:
- Poor tensile and tear strength for standard compounds
- Poor wear resistance
- Poor resistance against aromatic oils and oxidized
mineral oils
- Poor diffusion resistance
Radial Oil Seal
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