While selecting an O-ring to your application, a great deal of importance must be put on the fabric from the seal used. Since an effective sealing action is tremendously dependent on the health of your O-ring, it is crucial 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 a variety of factors, but two of the most critical factors are definitely the operating temperature range that O ring are exposed to as well as the different chemicals they might be open to. Some additional factors that play a role in selecting an O-ring material include effectiveness against tearing and abrasion, and sunlight or aging. Because most O-ring materials react differently to diverse environments and also chemicals, each material possesses its own positives and negatives.
Just about the most common materials utilized to make O-rings is nitrile rubber or Buna-N, that is a synthetic rubber copolymer. This product has excellent potential to deal with water, hydraulic fluids, solvents, oils and other petroleum products. This feature, coupled with its operating temperature array of between -65 degrees F to 275 degrees F, has made nitrile rubber probably the most commonly used elastomers to create O-ring seals. However, this product is equipped with its limitations; nitrile is normally not advised for applications where it might be open to sunlight and ozone, along with certain chemicals, such as ketones, esters, and aromatic hydrocarbons. Furthermore, its inclination towards ozone also will make it necessary that nitrile rubber seals are not stored near electric motors that normally generate ozone. Its high potential to deal with petroleum products and reasonable resistance to temperature has triggered Nitrile rubber O-rings becoming the very first option for various applications inside the automobile industry.
Silicone rubbers are an accumulation of elastomeric polymers made out of silicon, hydrogen, oxygen, and carbon. Silicones generally have poor resistance to abrasion and tearing, as well as low tensile strength plus high co-efficient of friction – features that can make them unsuitable for dynamic sealing applications. However, its exceptional potential to deal with extreme temperatures, which range from as low as -150 degrees F to up to 500 degrees F, causes it to be perfect for applications where seals are exposed to high dry heats, like in automotive components and cookware.
Viton(r) can be another synthetic rubber popular for making O-ring seals, which is a kind of FKM elastomer. This elastomer’s excellent resistance to solvents and oils, as well as its resistance to broad operating temperature ranges, has made it a common for use in many applications. Though its operating temperature ranges from -10 to 400 degrees F, seals produced from this material are recognized to withstand temperatures as much as 600 degrees F in short times. This blend of properties makes Viton an excellent choice for high temperature applications along with applications in contact with a number of different fluids. One application which has adopted Viton O-rings is Deep-sea diving, the location where the O-ring seals are being used in the diver’s air tank. However, though Viton is compatible with most hydrocarbons, it can be generally not works with ketones and organic acids.
One fluoropolymer commonly used to produce O-rings is PTFE, or Teflon(r), as it is commonly known. PTFE is probably the most chemically inert materials used to make O-rings and extremely immune to oils, solvents, bases, acids, steam, and various other chemicals. Its unparalleled resistance to 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 popular O-ring materials, which translates into inefficient sealing. One other major disadvantage of this product 98dexipky its poor cold flow characteristics under constant strain. Still, its chemical resistance and low coefficient of friction makes it a well known sealing option in lots of valves along with other applications.
Neoprene is an additional synthetic rubber that is regularly employed to make O-ring seals. This elastomer is resistant against animal and vegetable fats, in addition to most oils and solvents. However, O-ring seals created from this material are typically not advised for applications that involve exposure to ketones, esters, aromatic hydrocarbons, and powerful oxidizing acids.
Currently, natural rubber O-rings are rarely used due to coming of synthetic elastomers, like Nitrile rubber and Viton. Natural rubber can be utilized with animal oils, vegetable oils, and many oxidizing chemicals. However, it is not necessarily suitable for use with oils, petroleum solvents, aromatic hydrocarbons, and also in applications that demand exposure to sunlight or ozone.
These listed materials are generally used elastomers for creating O-rings, but many other materials, including Kalrez, will also be used in certain special applications. Kalrez is an ideal replacement for Viton in applications which may have operating temperatures as high as 500 degrees F. Similarly, there are various other elastomers utilized for specific sealing purposes. No matter what the material you decide on for your personal application, care must be taken to ensure its compatibility with operating temperatures, fluids, and environment.
The criticality of picking the best material for your application is immediately apparent when we consider the reason for Space Shuttle Challenger disaster. This tragedy was caused by the failure of an O-ring that lost its elasticity and have become brittle on account of an unexpected drop in ambient temperature. Though most O-ring failures may not cause the loss in life at par with this disaster, there is not any denying the definite economic loss the effect of a failed machine or device.