An annular cover consisting of one or several parts, fixed to a ferrule or washer of the bearing and in contact with another ferrule or gasket or forming a narrow labyrinth gap to prevent leakage of lubricating oil and invasion of foreign objects. The sealing ring is a rubber ring with a circular cross section. Because its cross section is O-shaped, it is called an O-ring. It is the most widely used type of hydraulic and pneumatic transmission systems.

1. NBR nitrile rubber seal

It is suitable for use in petroleum-based hydraulic oil, glycol-based hydraulic oil, diester-based lubricating oil, gasoline, water, silicone grease, silicone oil and other media. It is currently the most versatile and lowest cost rubber seal. Not suitable for use in polar solvents such as ketones, ozone, nitrohydrocarbons, MEK and chloroform. The general temperature range is -40~120 °C.

2. HNBR hydrogenated nitrile rubber sealing ring

It has excellent corrosion resistance, tear resistance and compression set resistance, and is resistant to ozone, sunlight and weather. Better wear resistance than nitrile rubber. Suitable for use in washing machines, automotive engine systems and refrigeration systems using the new environmentally friendly refrigerant R134a. Not recommended for use in alcohols, esters or aromatic solutions. The general temperature range is -40~150 °C.

3. SIL silicone rubber seal

It has excellent heat resistance, cold resistance, ozone resistance and weather resistance. Has good insulation properties. However, the tensile strength is inferior to that of 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 water bottles and water dispensers. Not recommended for most concentrated solvents, oils, concentrated acids and sodium hydroxide. The general temperature range is -55~250 °C.

4. VITON fluorocarbon rubber seal

High temperature resistance is superior to silicone rubber, with excellent weather resistance, ozone resistance and chemical resistance, and poor cold resistance. It is resistant to most oils and solvents, especially acids, aliphatic hydrocarbons, aromatic hydrocarbons and animal and vegetable oils. Suitable for sealing requirements in diesel engines, fuel systems and chemical plants. It is not recommended for use in ketones, low molecular weight esters and mixtures containing nitrates. The general temperature range is -20~250 °C.

5. FLS fluorosilicone rubber seal

Its properties combine the advantages of fluorocarbon rubber and silicone rubber, and are excellent in oil resistance, solvent resistance, fuel oil resistance and high and low temperature resistance. It is resistant to attack by oxygen-containing compounds, aromatic-containing solvents, and chlorine-containing solvents. Generally used in aviation, aerospace and military applications. Manufacturers of rubber foamed coils are not recommended to be exposed to ketones and brake fluids. The general temperature range is -50~200 °C.

6. EPDM EPDM rubber seal

Has good weather resistance, ozone resistance, water resistance and chemical resistance. It can be used in alcohols and ketones, and it can also be used for sealing in high temperature water vapor environment. Suitable for use in sanitary equipment, automotive radiators and automotive brake systems. Not recommended for food use or exposure to mineral oil. The general temperature range is -55~150 °C.

7. CR neoprene seal

It is especially 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, but it has a large amount of expansion in mineral oil with low aniline point. It is easy to crystallize and harden at low temperatures. Applicable to all kinds of environments exposed to the atmosphere, sunlight, ozone and various flame-resistant and chemical-resistant sealing parts. It is not recommended for use in chemicals such as strong acids, nitrohydrocarbons, esters, chloroforms and ketones. The general temperature range is -55~120 °C.

8. IIR butyl rubber seal

It has excellent air tightness, good heat resistance, sunlight resistance, ozone resistance and good insulation performance. It has good resistance to polar solvents such as alcohols, ketones and esters and can be exposed to animal and vegetable oils or oxidizable oxides. Suitable for chemical resistant or vacuum equipment. It is not recommended for use with petroleum solvents, kerosene or aromatics. The general temperature range is -50~110 °C.

9. ACM acrylate rubber seal

It has excellent resistance to oil, high temperature resistance and weather resistance, but mechanical strength, compression set and water resistance are slightly poor. Generally used in automotive transmission systems and power steering systems. Not suitable for use in hot water, brake fluid, and phosphate esters. Typical operating temperatures range from -25 to 170 °C.

10. NR natural rubber seal

Rubber products have good wear resistance, elasticity, tear strength and elongation. However, it is easy to age in the air, becomes sticky when exposed to heat, easily swells and dissolves in mineral oil or gasoline, and is alkali-resistant but not resistant to strong acid. It is suitable for use in liquids such as automobile brake oil and ethanol with hydroxide ions. The general temperature range is -20~100 °C.

11. PU polyurethane rubber seal

The mechanical properties of polyurethane rubber are very good, and the wear resistance and high pressure resistance are far superior to other rubbers. Aging resistance, ozone resistance, and oil resistance are also quite good, but high temperature is easily hydrolyzed. Generally used for high pressure and wear resistant sealing parts, such as hydraulic cylinders. The general temperature range is -45~90 °C.

12. Metal rubber seals

Made of stainless steel wire, it does not contain any rubber components and has strong use characteristics. For example: keep working under high vacuum, high and low temperature, strong radiation, and various corrosive environments. The skin of the sealing ring is made of different materials such as stainless steel, copper, PTFE, etc. according to the application. The coated metal rubber member is used as the core, which has the advantages of high sealing strength, good effect and reusability. The seal core is made of different wire diameters and densities and is suitable for different pressure applications. The general use range is -80~800 °C. Such a seal is expensive because of its high cost. However, good performance and a wide range of use environments have been recognized by people.

Reprinted from the network