An annular cover composed of one or several parts is fixed on one ring or washer of the bearing and contacts with another ring or washer or forms a narrow labyrinth gap to prevent leakage of lubricating oil and invasion of foreign objects. The seal ring is a
rubber ring with a circular cross-section. Because its cross-section is O-shaped, it is called an O-shaped seal ring. 1. NBR nitrile rubber sealing ring: Suitable for use in petroleum-based hydraulic oil, glycol-based hydraulic oil, diester-based lubricants, gasoline, water, silicone grease, silicone oil and other media It is the most widely used and lowest cost rubber seal. Not suitable for polar solvents, such as ketones, ozone, nitro hydrocarbons, MEK and chloroform. The general operating temperature range is -40 to 120 ℃. 2. HNBR hydrogenated nitrile rubber sealing ring: It has excellent anti-corrosion, anti-tear and anti-compression deformation characteristics, good resistance to ozone, sunlight and weather. Better wear resistance than nitrile rubber. It is suitable for washing machinery and automobile engine system. Not recommended for use in alcohols, esters or aromatic solutions. The general use temperature range is -40 ~ 150 ℃. 3. SIL silicone rubber sealing ring: It has excellent heat resistance, cold resistance, ozone resistance and atmospheric aging resistance. Has good insulation properties. However, the tensile strength is inferior to ordinary rubber and does not have oil resistance. Suitable for household appliances such as electric water heaters, electric irons, microwave ovens, etc. It is also suitable for all kinds of articles that come into contact with the human body, such as kettles and water dispensers. Not recommended for use in most concentrated solvents, oils, concentrated acids and sodium hydroxide. The general temperature range is -55～250 ℃. 4. VITON fluorine rubber sealing ring: High temperature resistance is better than silicone rubber, has excellent weather resistance, ozone resistance and chemical resistance, poor cold resistance. Resistant to most oils and solvents, especially acids, aliphatic hydrocarbons, aromatic hydrocarbons and animal and vegetable oils. Suitable for sealing requirements of diesel engines, fuel systems and chemical plants. Not recommended for ketones, low molecular weight esters and nitrate-containing mixtures. The general use temperature range is -20 ~ 250 ℃. 5. FLS fluorine silicone rubber sealing ring: Its performance combines the advantages of fluororubber and silicone rubber, and it is excellent in oil resistance, solvent resistance, fuel oil resistance, and high and low temperature resistance. Can resist the erosion of oxygen-containing compounds, aromatic hydrocarbon-containing solvents and chlorine-containing solvents. The general use temperature range is －50～200 ℃. 6. EPDM EPDM rubber sealing ring: It has good weather resistance, ozone resistance, water resistance and chemical resistance. It can be used for alcohols and ketones, and can also be used for sealing in high temperature water vapor environment. The general temperature range is -55～150 ℃. 7. CR neoprene sealing ring: It is particularly resistant to sunlight and weather. It is not afraid of refrigerants such as dichlorodifluoromethane and ammonia. It is resistant to dilute acid and silicone grease-based lubricants, but it has a large expansion in mineral oil with a low aniline point. It is easy to crystallize and harden at low temperature. It is suitable for all kinds of environments that are exposed to the atmosphere, sunlight, ozone, and various sealing links that are resistant to fire and chemical corrosion. Not recommended for use in chemicals with strong acids, nitro hydrocarbons, esters, chloroform and ketones. The general temperature range is -55～120 ℃. 8. IIR butyl rubber sealing ring: It has particularly good air tightness, heat resistance, sunlight resistance, ozone resistance, and good insulation performance; it has good resistance to polar solvents such as alcohol, ketone, and ester, and can be exposed to animal and vegetable oils or oxidizable materials. Suitable for chemical resistant or vacuum equipment. Not recommended for use with petroleum solvents, kerosene or aromatic hydrocarbons. The general use temperature range is －50～110 ℃. 9. ACM acrylic rubber sealing ring: It has excellent resistance to oil products, high temperature resistance and weather resistance, but its mechanical strength, compression deformation rate and water resistance are slightly worse. Generally used in automobile transmission system and power steering system. Not suitable for hot water, brake fluid, phosphate ester. The general use temperature range is -25 ~ 170 ℃. 10. NR natural rubber sealing ring: Rubber products have good wear resistance, elasticity, tear strength and elongation. But it is easy to aging in the air, it becomes sticky in heat, it swells and dissolves in mineral oil or gasoline, and it is resistant to alkali but not strong acid. It is suitable for use in liquids with hydroxide ions such as automobile brake fluid and ethanol. The general use temperature range is -20 ~ 100 ℃. 11. PU polyurethane rubber sealing ring: The mechanical properties of polyurethane rubber are very good, and its wear resistance and high pressure resistance are far superior to other rubbers. The aging resistance, ozone resistance and oil resistance are also quite good, but high temperature is easy to hydrolyze. Generally used for high-pressure, wear-resistant sealing links. The general temperature range is -45～90 ℃.
