While selecting an O-ring for your application, plenty of importance needs to be put on the information of your seal getting used. Since a proper sealing action is tremendously dependent on the fitness of your O-ring, it is important that an O-ring material be chosen to best suit the operating environment of your own application. Several of the common materials accustomed 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 determined by several different factors, but two of the more critical factors are definitely the operating temperature range that O ring are subjected to and also the different chemicals they could be in contact with. Some additional factors that are involved in picking an O-ring material include effectiveness against tearing and abrasion, and sunlight or aging. Since most O-ring materials react differently to diverse environments and also chemicals, each material features its own benefits and drawbacks.
One of the most common materials employed to make O-rings is nitrile rubber or Buna-N, which is a synthetic rubber copolymer. This material has excellent potential to deal with water, hydraulic fluids, solvents, oils and other petroleum products. This feature, along with its operating temperature selection of between -65 degrees F to 275 degrees F, has made nitrile rubber just about the most commonly used elastomers to create O-ring seals. However, this product is equipped with its limitations; nitrile is generally not advised for applications where it might be exposed to sunlight and ozone, as well as certain chemicals, such as ketones, esters, and aromatic hydrocarbons. Furthermore, its susceptibility to ozone also can make it necessary that nitrile rubber seals usually are not stored near electric motors that normally generate ozone. Its high resistance to petroleum products and reasonable potential to deal with temperature has led to Nitrile rubber O-rings becoming the first selection for various applications in the automobile industry.
Silicone rubbers are an accumulation of elastomeric polymers made out of silicon, hydrogen, oxygen, and carbon. Silicones generally have poor potential to deal with 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, starting from only -150 degrees F to up to 500 degrees F, will make it suitable for applications where seals are open to high dry heats, as in automotive components and cookware.
Viton(r) is another synthetic rubber popular to make O-ring seals, which is a form of FKM elastomer. This elastomer’s excellent effectiveness against solvents and oils, as well as its effectiveness against broad operating temperature ranges, has created it a well known to use in a number of applications. Though its operating temperature ranges from -10 to 400 degrees F, seals created from this material are known to withstand temperatures as much as 600 degrees F in short times. This combination of properties makes Viton a great choice for high temperature applications in addition to applications subjected to many different different fluids. A great application which has adopted Viton O-rings is Diving, the location where the O-ring seals are used in the diver’s air tank. However, though Viton is compatible with most hydrocarbons, it can be generally not suitable for ketones and organic acids.
One fluoropolymer frequently used to produce O-rings is PTFE, or Teflon(r), because it is commonly known. PTFE is one of the most chemically inert materials employed to make O-rings and intensely proof against oils, solvents, bases, acids, steam, and various other chemicals. Its unparalleled potential to deal with abrasion and tearing can make it perfect for dynamic sealing applications. However, you will find few drawbacks to using PTFE O-rings. The first is the inability to be compressed as effectively as other frequently used O-ring materials, which means inefficient sealing. Other major downside of this product 98dexipky its poor cold flow characteristics under constant strain. Still, its chemical resistance and low coefficient of friction makes it a favorite sealing option in several valves along with other applications.
Neoprene can be another synthetic rubber that is certainly regularly employed to make O-ring seals. This elastomer is resistant to animal and vegetable fats, and also most oils and solvents. However, O-ring seals created from this material are usually not recommended for applications that entail contact with ketones, esters, aromatic hydrocarbons, and robust oxidizing acids.
Presently, natural rubber O-rings are rarely used as a result of coming of synthetic elastomers, like Nitrile rubber and Viton. Natural rubber can be used with animal oils, vegetable oils, and most oxidizing chemicals. However, it is far from suitable for use with oils, petroleum solvents, aromatic hydrocarbons, and then in applications that demand being exposed to sunlight or ozone.
These listed materials are generally used elastomers to make O-rings, but many other materials, for example Kalrez, are also employed in certain special applications. Kalrez is a great replacement for Viton in applications who have operating temperatures as high as 500 degrees F. Similarly, there are many other elastomers utilized for specific sealing purposes. Regardless of the material you select for your personal application, care needs to be taken up ensure its compatibility with operating temperatures, fluids, and environment.
The criticality of choosing the best material to your application is straight away apparent if we consider the reason for Space Shuttle Challenger disaster. This tragedy was caused by the failure of any O-ring that lost its elasticity and have become brittle due to an unexpected drop in ambient temperature. Though most O-ring failures may well not result in the reduction in life at par with this particular disaster, there is absolutely no denying the definite economic loss caused by a failed machine or device.