Sealing the bearings

The increasing use of closed-end bearings are obtained with integrated seals. Seals protect bearings from the ingress of foreign bodies on the track and the rolling elements, as well as serve to hold the mortgaged lifetime lubrication of the bearing, in the case where the re-lubrication of the bearing is not provided.
SNR bearings The company produces the following types of built-in seals: protective metal washers, metal-polymer and high integrity seal. The use of different types of seals depends on the operating conditions of the bearing assembly. The main factors to be considered when selecting a bearing with one or another type of seal, the following:

the maximum allowable rotation speed;
temperature control;
external influences (humidity, dust, corrosive environments, etc.);
the possibility or impossibility to supply additional lubrication (in hull uzlahvozmozhna supply additional lubrication).

Protective metal washers

Metal washers are installed in a groove on the outer ring of the bearing and fixed without deforming it. The washers are made from stamped sheet steel. Since the washers have no contact with the inner ring of the bearing, they practically do not affect the speed limit. But the protective properties of the metal washers are significantly inferior metal-polymer and highly integrated seals.

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Illustration: SNR

Protective metal washers

Standard protective metal washer in the bearing designation designated by letter Z. The bearings may be incorporated alone (Z), is installed on one side or two washers (ZZ) – on both sides.

Install only one protective washer is used when it is necessary to ensure the protection of the bearing from one side only, or there is a need peresmazyvaniya (supply additional lubrication). Two-way system – when the bearing securely zaschititot dirt and grease replacement is performed.

Labyrinth seals c protective metal washers

The seal is designed for the efficient retention of grease and ingress of foreign bodies, while providing a compact size. Such seals often consists of two closely spaced metal washers. Inner washer mounted on the outer ring of the bearing and holds the lubricant inside the bearing. The outer washer is mounted on the inner race ring and is reflective at the rotation casting body contaminants. According to the protective properties of the labyrinth seals surpass the standard protective metal washers, but inferior to other types of seals. Designed for operation at high temperatures, as an alternative to more expensive seals of heat-resistant polymers (for example, FPM).

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Illustration: SNR

Labyrinth seals c protective metal washers

Labyrinth seals with metal washers are mainly built into housing bearings.

Metallo-plastic seal with a sealing lip

Metal-polymer seals are installed in a groove on the outer ring of the bearing and there are fixed firmly without deforming the outer ring. They are made of different polymeric materials and reinforced with steel stamped rings.

Metal-polymer seals provide a high degree of protection against contamination of internal components and bearing grease. However, limiting speed and smoothness deteriorates due to contact friction seals that come into contact with the inner ring of the ring.

Standard seals in the bearing designation are designated RS letters. The bearings can be incorporated one (RS), installed on one side or two seals – on both sides of (2RS).

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Metallo-plastic seal with a sealing lip

Unilateral seal is used when it is necessary to ensure the protection of the bearing from one side only, or there is a need peresmazyvaniya (supply additional lubrication). Bilateral seal is used when the bearing is necessary to reliably protect and lubricant replacement is performed.

Metal-polymer seal with triple lip seals

This seal consists of a protective sheet steel washer, to which is attached by vulcanization triple lip seals butadenakrilnitrilnogo rubber. This design provides a reliable protection element bearings and lubrication laid down in the conditions of strong pollution. However, the rotational speed of the bearing due to a large contact friction seal edges is significantly reduced.

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Illustration: SNR

Metal-polymer seal with triple lip seals

Seals with triple sealing lip is mainly embedded in the housing bearings.

Highly seal

To meet the need for reliable protection of the bearing from a particularly stubborn dirt vysokintegrirovannye special seals have been developed without changing the external dimensions. These seals have a “batch” structure – inside a metal casing located trehkromochnoe polymeric seal. Special design and use of a special polymer material reduces the contact friction and increases the speed of rotation of the bearing. To improve the corrosion properties of the casing is made of stainless steel.

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Illustration: SNR

Highly seal

These seals provide a high degree of protection against pollution, while having a compact size and low contact friction. But due to the complex structure vysokointergirovannye seals have a relatively high price.

Application found mainly in the wheel bearing cars.

Comparison of the protective properties of the seals

Here is a comparison of protective properties embedded in bearings SNR seals.

Comparison of the protective properties of the seals

Sealing Comparison settings
Contact friction Dust Protection against moisture The rotational speed of the bearing
Protective metal washersNosatisfactorybadno effect
Labyrinth seals protective metal washersNogoodbadno effect
Metal-polymer seals with a sealing lipbiggreatgood70% of the limit speed of rotation
Metal-polymer seal with triple lip sealsgreatgreatgreatup to 500 rev / min
Highly sealbiggreatgreat50% of the limit speed of rotation

Sealing materials

Built bearing seals are generally made of polymer materials and stamped sheet metal. Type of material can depend on the series and size of the bearing, as well as the demands placed on them.
Metal protective washers are made of stamped steel sheet. To operate in normal conditions – of standard steel. In corrosive environments – from stainless steel.

Widely used in the manufacture of polymeric material embedded seal is a synthetic rubber based on nitrile rubber (NBR), which replaced the previously used neoprene polymers. Nitrile rubber is a copolymer of acrylonitrile and butadiene has good resistance to a larger number of environments:

most mineral oils and greases based on mineral oil;
conventional fuels: gasoline, diesel fuel and fuel oil;
animal and vegetable oils and fats;
hot water;
weak solutions of salt and acid.
The interval of allowable operating temperatures from -30 to +110 ° C. At higher temperatures the seals become hard and brittle.
For operation in a chemically active medium at high temperatures and applied fluoroelastomers based polymers. The seals of these materials stand to aging and ozone and have a very low permeability. They have extremely high wear resistance characteristics, even under adverse environmental conditions and can withstand temperatures up to +200 ° C.

Fluororubbers are resistant to almost all types of oils and hydraulic fluids, fuels and lubricants, acids and bases, as well as aromatic hydrocarbons, which cause damage to seals made from other materials.

The interval of allowable operating temperatures from -40 to +200 ° C. At higher temperatures (above 300 ° C) begin to release toxic fluororubbers fluorinated evaporation furthermore once heated to such high temperature seals dangerous even after cooling. Therefore, the heating above 300 ° C should be avoided.

Comparison of the properties of sealing materials

Option C inteticheskaya tires (NBR ) Fluoroelastomer ( VITON )
Heat Resistance110 ° C200 ° C
Low-temperature flexibility (max.)– 50 ° C– 50 ° C
Frictiono *o
wear resistancex **o
The aging of the action of the sunxo
The aging of the oxidationxo
Resistance to lubricants based on mineraloo
Resistance to lubricants based on syntheticxo
Resistant to chemicalsxo
Water resistanceoo

Note:

* O – good;

** X – bad.