While selecting an O-ring for the application, lots of importance needs to be added to the fabric of the seal getting used. Since an appropriate sealing action is extremely reliant on the health of your O-ring, it is essential that an O-ring material be chosen to best suit the operating environment of your application. A number 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 reliant on several different factors, but two of the very most critical factors are the operating temperature range that O ring are subjected to and the different chemicals they may be exposed to. Some additional factors that be involved in the selection of an O-ring material include potential to deal with tearing and abrasion, and sunlight or aging. Since the majority O-ring materials react differently to diverse environments as well as chemicals, each material possesses its own positives and negatives.
Just about the most common materials accustomed to make O-rings is nitrile rubber or Buna-N, which is actually a synthetic rubber copolymer. This material has excellent potential to deal with water, hydraulic fluids, solvents, oils along with other petroleum products. This feature, coupled with its operating temperature range of between -65 degrees F to 275 degrees F, made nitrile rubber one of the most popular elastomers to help make O-ring seals. However, this material is equipped with its limitations; nitrile is normally not recommended for applications where it could be exposed to sunlight and ozone, in addition to certain chemicals, such as ketones, esters, and aromatic hydrocarbons. Furthermore, its susceptibility to ozone also causes it to be necessary that nitrile rubber seals will not be stored near electric motors that normally generate ozone. Its high potential to deal with petroleum products and reasonable effectiveness against temperature has led to Nitrile rubber O-rings becoming the 1st option for various applications within the automobile industry.
Silicone rubbers are a selection of elastomeric polymers made out of silicon, hydrogen, oxygen, and carbon. Silicones normally have poor resistance to abrasion and tearing, and also low tensile strength plus high co-efficient of friction – features that make them unsuitable for dynamic sealing applications. However, its exceptional effectiveness against extreme temperatures, which range from as little as -150 degrees F to as much as 500 degrees F, causes it to be perfect for applications where seals are subjected to high dry heats, like in automotive components and cookware.
Viton(r) is an additional synthetic rubber commonly used for making O-ring seals, which is a form of FKM elastomer. This elastomer’s excellent effectiveness against solvents and oils, as well as its resistance to broad operating temperature ranges, has created it a well known to be used in many applications. Though its operating temperature ranges from -10 to 400 degrees F, seals made out of this material are acknowledged to withstand temperatures as much as 600 degrees F in short times. This blend of properties makes Viton an ideal choice for high temperature applications along with applications in contact with a variety of different fluids. One application that has adopted Viton O-rings is Diving, the location where the O-ring seals are being used from the diver’s air tank. However, though Viton is compatible with most hydrocarbons, it really is generally not appropriate for ketones and organic acids.
One fluoropolymer popular to manufacture 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 intensely immune to oils, solvents, bases, acids, steam, as well as other chemicals. Its unparalleled potential to deal with abrasion and tearing will make it ideal for dynamic sealing applications. However, you will find few drawbacks to using PTFE O-rings. The first one could be the inability to be compressed as effectively as other popular O-ring materials, which means inefficient sealing. Another major disadvantage of this product 98dexipky its poor cold flow characteristics under constant strain. Still, its chemical resistance and low coefficient of friction made it a popular sealing option in numerous valves and other applications.
Neoprene is another synthetic rubber that is certainly regularly used to make O-ring seals. This elastomer is resistant against animal and vegetable fats, and also most oils and solvents. However, O-ring seals produced from this material are often not suggested for applications that entail contact with ketones, esters, aromatic hydrocarbons, and strong oxidizing acids.
Presently, natural rubber O-rings are rarely used due to development of synthetic elastomers, like Nitrile rubber and Viton. Natural rubber works extremely well with animal oils, vegetable oils, and the majority of oxidizing chemicals. However, it is far from recommended for use with oils, petroleum solvents, aromatic hydrocarbons, and then in applications that demand being exposed to sunlight or ozone.
These listed materials are typically used elastomers for making O-rings, but other materials, such as Kalrez, may also be used in certain special applications. Kalrez is an ideal alternative to Viton in applications that have operating temperatures up to 500 degrees F. Similarly, there are various other elastomers utilized for specific sealing purposes. Regardless of the material you choose to your application, care needs to be taken up ensure its compatibility with operating temperatures, fluids, and environment.
The criticality of picking the best material for the application is immediately apparent once we consider the cause of Space Shuttle Challenger disaster. This tragedy was caused by the failure of the O-ring that lost its elasticity and became brittle due to an unexpected drop in ambient temperature. Though most O-ring failures might not lead to the loss of life at par using this type of disaster, there is not any denying the definite economic loss caused by a failed machine or device.