When it comes to forces able to deteriorate mechanical components, one of the most destructive is heat. Because of this, it is especially important to make components for such applications from compounds that can withstand a high temperature. O-rings are mechanical gaskets shaped like doughnuts, made from an elastomer loop with round cross-sections that are designed to fit into a groove. They allow compression between two or more parts during assembly, forming a seal at that point. O-rings can be used in applications both where there is motion between the O-ring and other components or where other parts remain stationary. O-rings are an especially important mechanical component, necessary in a broad array of mechanical applications, so heat-resistant O-rings must be fabricated from materials that can withstand heat well.
Best Heat-Resistant O-Rings
High-temperature O-rings are generally categorized as those that can withstand temperatures of 150°C (302°F) or more. This limits what materials can be used, with certain materials offering advantages depending on the application. The best O-ring for high-temperature applications is determined by a variety of factors, such as how well it resists deformation or deals with excessive friction. The presence of chemicals in an application will also limit what materials are used for fabricating heat-resistant O-rings, as certain materials offer more chemical-resistance than others.
7 Advantages of High-Temperature O-Rings by Material
The following types of materials for heat-resistant O-rings provide the following benefits:
Fluoroelastomer (FKM) Heat-Resistant O-Rings
Widely used as a sealant, FLM withstands heat up to 204°C (400°F) and works well for applications that expose this material to various fuels, lubricants and oils at a high temperature. O-rings made from FLM offer resistance to transmission fluid, engine oil, carbon-based fuels and other engine fluids, along with silicone oils, mineral oil, halogenated hydrocarbons, chemicals, and most acids. FLM heat-resistant O-rings also resist permeation and compression set, a characteristic of certain foams that cause them to return to their former thickness. However, FLM O-rings have no or limited resistance to steam or heated water, liver acids called ketones that break down fat in the body, ammonia-based organic compounds known as amines, low-molecular organic compounds called esters like those found in essential oils, and oxygen-based organic compounds known as ethers.
Polytetrafluoroethylene (PTFE) Heat-Resistant O-Rings
O-rings made from PTFE handle temperatures up to 250°C (482°F), along with offering resistance to all known acids, alkalis, and solvents. These O-rings deal with extreme cold as well and are capable of withstanding temperatures of -200°C (-328°F). An inflexible thermoplastic polymer, O-rings made from PTFE can be easily recycled by melting and resetting the material into a different shape. Its wide temperature range makes high-temperature O-rings made from PTFE extraordinarily versatile, though due to the hardness of the material they dent relatively easily.
Perfluoroelastomer (FFKM) Heat-Resistant O-Rings
Essentially a mixture of PTFE and FKM, FFKM O-rings operate well in temperatures ranging from 230-330°C (446-626°F). As elastomeric polymers, FFKM resists both chemicals and environments with high temperatures, as well as conditions involving high-pressure and potential for explosive decompression. O-rings made from FFKM come in a number of different grades, depending on the application, and are widely used to handle pharmaceutical ingredients, hydrogen sulfite gas, and harsh cleaning agents.
Hydrogenated Nitrile (HNBR) Heat-Resistant O-Rings
The high-temperature O-rings made from HBNR can withstand is only 140°C (284°F), though it does make these components capable of working with automotive fuels, gases, and oils. However, HBNR O-rings are not appropriate for use with strong acids or chlorinated hydrocarbons, which include insecticides like DDT. O-rings made from the material offer excellent resistance to abrasion, compression set, and wear, making them particularly reliable for numerous applications where durability is key. HNBR was developed for greater compatibility and to increase temperature resistance with newer automotive fuels. Being more robust and degrading only minimally at high temperatures, O-rings made from HNBR also offer specific chemical and physical resistances depending on their exact formulation.
Tetrafluoroethylene and Propylene (TFE/P) Heat-Resistant O-Rings
TFE/P O-rings handle most chemicals used as automotive sealants and can withstand high-temperature environments. A copolymer of both tetrafluoroethylene and propylene, TFE/P has a fluorine content of approximately 54 percent. Unique due to its resistance to phosphate esters, petroleum products, and steam, it also displays properties similar to that of ethylene propylene and fluorocarbons when it comes to compatibility with media. However, TFE/P has substandard compression set resistance compared to typical fluorocarbons when exposed to high temperatures. O-rings made from TFE/P operate well between -5-204°C (25-400°F), with better chemical resistance among a wide range of additives and fluids used in motor vehicles, including brake fluids, engine coolants gear lubricants, power-steering fluid, and transmission fluid, along with resisting corrosion, mineral oil, and silicone-based lubricants. TFE/P O-rings offer an ideal component for applications involving heat transfer media that transform solar power into heat, acids, amines, and bases, along with steam and hot water at temperatures reaching as high as 170°C (340°F).
Silicone Heat-Resistant O-Rings
Silicone O-rings operate well between -84-232°C (-120-450°F), with some types of silicone able to handle temperatures as high as 300°C (572°F) or as low as -115 (175°F) for shorter periods. Commonly used when the risk of exposure to weathering, ultraviolet (UV) light, and ozone is high, silicone O-rings do not work well for applications involving chemicals, hot water, or other specific uses. Sometimes used in fuel injection ports exposed to high temperatures, O-rings made from silicone work well in applications involving petroleum-based fluids, steam, and water. However, silicone O-rings offer inferior resistance to tears and abrasions, along with lower tensile strength, so they are better for applications where they remain stationary.
Fluorinated Ethylene Propylene (FEP) Heat-Resistant O-Rings
In the same family of polymers as PTFE, FEP O-rings are used for similar applications and also offer resistance to chemicals as well as heat, though provide greater flexibility. Working best in temperatures under 204°C (400°F), high-temperature O-rings made from FEP work effectively in static applications when exposed to aggressive media. Widely used in the aerospace, automotive, and electronics industries, silicone O-rings are key components in cooling systems, pressure cleaners, and water processing machines.
Applications for High-Temperature O-Rings
Equipment exposed to extreme temperatures requires robust components be used, including for O-rings. Such O-rings help contain heated and highly-pressurized fluids such as fuel or lubricants within all manner of equipment. Heat-resistant O-rings are used in many industries, from chemical processing to oil and grass drilling, and in applications as diverse as rockets to racecars.
Applications for high-temperature O-rings include:
- Refrigerators and other cooling equipment
- Pressurized waterjet cutters
- Piping used for transport within petroleum refineries and drilling operations
- Pharmaceutical manufacturing
- Medical equipment
- Manufacturing equipment
- Laboratory equipment
- Hydraulic equipment
- Food and beverage processing
- Engines in motor vehicles
- Chemical processing
- Aircraft and spacecraft