O - rings (2) - Materials and Precautions
NBR:
Properties: It has good oil resistance, wear resistance and heat resistance. It shows excellent tolerance to fuel oils such as kerosene and light oil. It also has a certain degree of elasticity and mechanical strength.
Application Scenarios: It is widely used in various mechanical equipment and is often used for sealing in contact with oil - based media, such as hydraulic systems and automobile engines. However, it is not resistant to ozone, has a shorter lifespan when used outdoors, and has poor insulation performance.
Operating Temperature: Generally - 40℃ to 120℃.
SI/VMQ:
Properties: It has excellent heat resistance and cold resistance and can be used in a wide temperature range (- 50℃ to 200℃). It is not sensitive to alternating hot and cold conditions. It has good electrical insulation performance, excellent resistance to bacterial growth, and good hygienic performance. It has strong anti - ozone and anti - atmospheric aging performance, but its tensile strength is relatively low and it has no oil - proof property.
Application Scenarios: It is often used in industries with requirements for hygiene and temperature changes such as food, medical, and electronics, such as food - processing equipment, medical devices, and the sealing of electronic appliances.
Operating Temperature: - 50℃ to 200℃. Special - formula silicone rubber can be used at - 100℃ to 300℃.
EPDM:
Properties: It has excellent ozone resistance, weather resistance, and heat resistance (it can be used at - 45℃ to 130℃ for a long time). It has good tolerance to hot water, steam, organic fluids, and brake fluids (DOT4 and DOT5). It has good anti - aging performance and excellent insulation performance, but it is not oil - resistant and its tensile strength and wear resistance are relatively low.
Application Scenarios: It is often used in parts such as automobile radiators, braking systems, and door and window seals, as well as in equipment in outdoor environments or in contact with hot water and steam, such as the sealing of solar water heaters and hot - water pipes.
Operating Temperature: - 45℃ to 130℃ (vulcanized), - 50℃ to 150℃ (peroxide).
FKM:
Properties: It is one of the synthetic rubbers with the best oil resistance, chemical resistance, and heat resistance, and has a wide range of applications. It has good chemical stability and can resist the erosion of various strong acids, strong alkalis, and organic solvents. Its high - temperature resistance is outstanding and it can work at a relatively high temperature (- 15℃ to 200℃) for a long time. It has good mechanical properties and anti - aging performance, good ozone resistance and weather resistance, but its elasticity is relatively poor and the price is high.
Application Scenarios: It is suitable for high - temperature and strongly - corrosive chemical environments, such as the sealing parts of chemical equipment and aerospace fields, as well as the sealing parts in contact with strong acids and strong alkalis.
Operating Temperature: - 15℃ to 200℃. Special - formula products can be used at - 30℃ to 300℃.
Installation Precautions
1.Before installation, check whether the O - ring has defects such as flash and burrs and ensure that the size meets the design requirements.
2.Check whether the installation surface is flat and smooth and free of sharp edges and burrs.
3.Use tools without sharp edges for installation and avoid using sharp tools to scratch the O - ring.
4.During installation, avoid over - stretching the O - ring to prevent affecting its sealing performance.
Common Mistakes in Selecting O - rings
1.Ignoring Working Conditions: When selecting O - rings, factors such as temperature, pressure, and media in the working environment are not fully considered, which may lead to the selected material not meeting the usage requirements.
2.Overlooking Material Resistance: Insufficient understanding of the chemical resistance, temperature resistance, and anti - aging performance of the sealing ring material may lead to the selection of an unsuitable material in special working conditions.
3.Disregarding Hardness: Hardness has an important impact on the elasticity and pressure - resistance performance of O - rings. However, some users only focus on hardness and overlook its comprehensive impact on sealing performance.
4.Improper Size: The size of the selected O - ring does not match the sealing groove, which may lead to poor sealing, such as the wire diameter being too large or too small and the groove width being insufficient.
5.Installation Error: Incorrect installation may lead to the failure of the sealing ring, such as the sealing ring not being placed correctly in the groove or being damaged or distorted during installation.
6.Neglecting Material Compatibility: The compatibility between the O - ring material and the working medium is not considered, which may lead to chemical corrosion or other damages.
7.Using Out - of - date Standards: The O - ring standards used are out - of - date and do not meet the current design and manufacturing requirements.
