While selecting an O-ring for your personal application, lots of importance should be put on the content of the seal being utilized. Since an effective sealing action is extremely determined by the health of your O-ring, it is vital that an O-ring material be chosen to best suit the operating environment of your application. Several of the common materials used to make O-rings are nitrile rubber or Buna-N, Viton(r), silicone rubber, neoprene, and PTFE or Teflon(r).
Choosing an O-ring material is dependent on a variety of factors, but two of the very most critical factors will be the operating temperature range that O ring are put through and also the different chemicals they can be in contact with. Some additional factors that be a factor in selecting an O-ring material include resistance to tearing and abrasion, and sunlight or aging. Since the majority O-ring materials react differently to diverse environments and also chemicals, each material possesses its own pros and cons.
Just about the most common materials employed to make O-rings is nitrile rubber or Buna-N, that is a synthetic rubber copolymer. This product has excellent resistance to water, hydraulic fluids, solvents, oils and also other petroleum products. This feature, in conjunction with its operating temperature variety of between -65 degrees F to 275 degrees F, has made nitrile rubber one of the most widely used elastomers to produce O-ring seals. However, this material comes with its limitations; nitrile is usually not recommended for applications where it could be subjected to sunlight and ozone, in addition to certain chemicals, including ketones, esters, and aromatic hydrocarbons. Furthermore, its susceptibility to ozone also makes it necessary that nitrile rubber seals usually are not stored near electric motors that normally generate ozone. Its high effectiveness against petroleum products and reasonable effectiveness against temperature has led to Nitrile rubber O-rings becoming the 1st option for various applications from the automobile industry.
Silicone rubbers are a collection of elastomeric polymers made from silicon, hydrogen, oxygen, and carbon. Silicones have poor resistance to abrasion and tearing, along with low tensile strength plus high co-efficient of friction – features that will make them unsuitable for dynamic sealing applications. However, its exceptional resistance to extreme temperatures, which range from as little as -150 degrees F to as high as 500 degrees F, causes it to be perfect for applications where seals are exposed to high dry heats, as with automotive components and cookware.
Viton(r) is yet another synthetic rubber frequently used for making O-ring seals, which is a form of FKM elastomer. This elastomer’s excellent resistance to solvents and oils, as well as its resistance to broad operating temperature ranges, made it a well known for use in many applications. Though its operating temperature ranges from -10 to 400 degrees F, seals produced from this product are acknowledged to withstand temperatures as high as 600 degrees F for brief times. This mixture of properties makes Viton an excellent option for high temperature applications as well as applications in contact with various different fluids. A great application containing adopted Viton O-rings is SCUBA diving, where the O-ring seals are being used inside the diver’s air tank. However, though Viton works with most hydrocarbons, it is generally not works with ketones and organic acids.
One fluoropolymer commonly used to produce O-rings is PTFE, or Teflon(r), since it is commonly known. PTFE is probably the most chemically inert materials used to make O-rings and very proof against oils, solvents, bases, acids, steam, and various other chemicals. Its unparalleled effectiveness against abrasion and tearing will make it perfect for dynamic sealing applications. However, you will find few drawbacks to using PTFE O-rings. The first is lack of ability to be compressed as effectively as other commonly used O-ring materials, which translates into inefficient sealing. Another major downside of this material 98dexipky its poor cold flow characteristics under constant strain. Still, its chemical resistance and low coefficient of friction made it a favorite sealing option in many valves and also other applications.
Neoprene is another synthetic rubber which is regularly employed to make O-ring seals. This elastomer is resistant against animal and vegetable fats, as well as most oils and solvents. However, O-ring seals made out of this material are generally not suggested for applications that involve being exposed to ketones, esters, aromatic hydrocarbons, and robust oxidizing acids.
At the moment, natural rubber O-rings are rarely used as a result of coming of synthetic elastomers, including Nitrile rubber and Viton. Natural rubber can be utilized with animal oils, vegetable oils, and many oxidizing chemicals. However, it is not necessarily appropriate for use with oils, petroleum solvents, aromatic hydrocarbons, and in applications that demand contact with sunlight or ozone.
These listed materials are normally used elastomers to make O-rings, but many other materials, such as Kalrez, may also be found in certain special applications. Kalrez is a great replacement for Viton in applications which have operating temperatures as high as 500 degrees F. Similarly, there are numerous other elastomers used for specific sealing purposes. No matter what the material you select for your personal application, care needs to be delivered to ensure its compatibility with operating temperatures, fluids, and environment.
The criticality of picking the best material for your personal application is immediately apparent once we consider the reason for Space Shuttle Challenger disaster. This tragedy was caused by the failure of your O-ring that lost its elasticity and have become brittle as a result of an unexpected drop in ambient temperature. Though most O-ring failures may well not cause the loss of life at par with this disaster, there is absolutely no denying the definite economic loss the effect of a failed machine or device.