What Are the Different Types of O Rings?
An o-ring is a molded product placed between mechanical parts to create a seal for preventing fluid or gas leakage and keeping out contaminants. O-rings are available in a variety of properties and compositions to suit specific applications.
Silicone o rings provide a wide range of static performance including outstanding flex and fatigue life, strong ozone and UV radiation resistance and physiologically neutral and insulating properties. They also have excellent temperature tolerance.
Durability
Silicone o rings can resist harsh conditions including extreme cold, hot water, steam and petroleum fluids. They can operate in a temperature range of -84 degrees Celsius to 232 degrees Celsius and have been shown to hold up to temperatures as low as -175 degrees Celsius for short periods of time. They also have excellent resistance to ozone, weathering and dry heat. They have good tear and abrasion resistance but poor tensile strength, making them better for static rather than dynamic applications. Silicone is odorless, tasteless and non-toxic. There are also special formulations of silicone for use in food and beverage applications that require FDA-approved materials.
Generally, o rings made of silicone are used in industries such as automotive, aerospace, jewelry and food processing where the o-ring will be wedged between two moving pieces that require an o-ring seal to function. They are also commonly found in electrical, pneumatic and hydraulic applications.
Silicone is a versatile material that can be compression molded into custom o-ring geometries to offer better installation and fit in non-standard gland configurations. It can also be compounded to have a wide range of properties such as flame retardant, conductive or electrically resistant. It has good chemical resistance to engine and transmission oils (FVMQ), animal and vegetable fats, solvents, diluted salt solutions and ozone and UV radiation.
Heat Resistance
Silicone (VMQ) is a non-reactive elastomer that resists extreme temperatures and is capable of performing in high-temperature applications without deteriorating. It offers resistance to oxygen, ozone, UV light and has good chemical resistance. It has good resistance to mineral and vegetable oils, diluted salt solutions, and most common hydrocarbon fuels. However, silicone o-rings cannot be used in brake fluids, concentrated acids or superheated steam over 250 degrees.
Similarly, fluorosilicones (FVMQ) perform well in high-temperature applications and are resistant to UV radiation, ozone and weathering. They offer a wide operating temperature Silicone o rings range from -100° to 350°F but have poor hot air capabilities. They also have limited oil and fuel resistance.
Another popular choice for high-temperature o rings is FKM, which has strong carbon-fluorine bonds that give it great thermal and chemical resistance. Its abrasion and tear strength are better than silicone rubber and it can handle harsh chemicals and volatile liquids. It is not recommended for dynamic application due to its compression set and low tensile strength.
Lastly, neoprene has excellent thermal and chemical resistance and can be used for a wide range of applications. It withstands high temperatures and can be molded into complex geometries. It is FDA-approved and works well with many different types of chemicals. In addition, neoprene can be welded and vulcanized in applications where a permanent seal is required.
Temperature Range
Silicone o rings are highly flexible and remain pliable over a wide temperature range. They are also odorless and non-toxic. These qualities make them ideal for medical and food applications.
Like other silicone materials, they are FDA approved for use in contact with foods and drugs. They have good resistance to UV damage, corrosion and ozone. They are able to resist temperatures from -60°C to 225°C and some special varieties can even reach -100°C.
Another popular choice is Viton(r), which is an FKM synthetic fluoropolymer elastomer. Sometimes referred to as FPM, it is a robust material that works well in harsh environments. It is resistant to brutal atmospheric conditions, engine oil, brake fluid, diluted salt solutions, petroleum products and many chemicals and solvents.
It has very low compression set and a high shear strength, but it is not as good in low temperatures or with dynamic loads. Nitrile, which is another popular o-ring material, performs better in lower temperatures. It can handle temperatures down to -50°C, but full operation in these conditions will shorten the lifespan of the part significantly more than it would with normal usage. Nitrile is also an excellent material for systems that are sealed, protected from the elements and chemically aggressive substances.
Abrasion Resistance
Silicone o rings have very good abrasion resistance and are highly resistant to chemicals, solvents, oils and petroleum products. They resist UV damage and are non-toxic. They are able to work in temperatures of -60 degrees Celsius to 225 degrees Celsius, and special varieties can operate within a much larger range.
They also resist ozone, corona and are very well dielectrically stable. VMQ silicone O-rings are commonly used in Silicone O Rings – Supplier medical and food applications because they do not impart odor or taste to the seal material. These o-rings are extremely clean and can be compounded to be electrically resistant, conductive or flame retardant.
These o-rings are able to work with steam, water and petroleum fuels. However, because they have poor tear and abrasion resistance, they are not recommended for dynamic applications, but rather are best used for static applications.
Other elastomers are better suited for dynamic sealing situations because they have more well-rounded properties and exhibit higher levels of abrasion resistance, tear strength, tensile strength and wear resistance. These other types of O-rings include ethylene propylene, fluorosilicone and chloroprene. Buna-N, nitrile and Kalrez(r) rubber O-rings are also available in many different sizes and meet the requirements of a wide variety of industrial applications. Typical applications include hydraulic pressure, wheels, rolls and slurry parts. They are also a great choice for boilers, compressors and engines, refrigerators, heaters, pumps and valves.