While selecting an O-ring to your application, lots of importance should be put on the material from the seal being used. Since a proper sealing action is extremely influenced by the fitness of your O-ring, it is important that an O-ring material be chosen to work best with the operating environment of your 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 dependent on a variety of factors, but two of the very critical factors are the operating temperature range that O ring are put through and the different chemicals they can be open to. Some additional factors that be involved in your selection of an O-ring material include resistance to tearing and abrasion, and sunlight or aging. As most O-ring materials react differently to diverse environments as well as chemicals, each material has its own pros and cons.
One of the more common materials employed to make O-rings is nitrile rubber or Buna-N, that is a synthetic rubber copolymer. This material has excellent potential to deal with water, hydraulic fluids, solvents, oils and also other petroleum products. This feature, coupled with its operating temperature array of between -65 degrees F to 275 degrees F, makes nitrile rubber just about the most popular elastomers to help make O-ring seals. However, this product is equipped with its limitations; nitrile is normally not advised for applications where it will be open to sunlight and ozone, as well as certain chemicals, which include ketones, esters, and aromatic hydrocarbons. Furthermore, its susceptibility to ozone also makes it 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 potential to deal with temperature has resulted in Nitrile rubber O-rings becoming the very first choice for various applications inside the automobile industry.
Silicone rubbers are a selection of elastomeric polymers created from silicon, hydrogen, oxygen, and carbon. Silicones usually have poor resistance to abrasion and tearing, as well as low tensile strength plus high co-efficient of friction – features which make them unsuitable for dynamic sealing applications. However, its exceptional effectiveness against extreme temperatures, including as little 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 commonly used for making O-ring seals, which is a kind of FKM elastomer. This elastomer’s excellent effectiveness against solvents and oils, as well as its potential to deal with broad operating temperature ranges, made it a well known to use in several applications. Though its operating temperature ranges from -10 to 400 degrees F, seals made from this material are known to withstand temperatures up to 600 degrees F for brief times. This mix of properties makes Viton an ideal selection for high temperature applications as well as applications subjected to a variety of different fluids. One application that has adopted Viton O-rings is SCUBA diving, where the O-ring seals are employed within 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 widely used to produce O-rings is PTFE, or Teflon(r), because it is commonly known. PTFE is probably the most chemically inert materials accustomed to make O-rings and really resistant to oils, solvents, bases, acids, steam, as well as other chemicals. Its unparalleled resistance to abrasion and tearing will make it suitable for dynamic sealing applications. However, there are few drawbacks to using PTFE O-rings. The first one is lack of ability to be compressed as effectively as other frequently used O-ring materials, which results in inefficient sealing. Other major drawback to this product 98dexipky its poor cold flow characteristics under constant strain. Still, its chemical resistance and low coefficient of friction has made it a favorite sealing option in numerous valves and other applications.
Neoprene is another synthetic rubber that may be regularly accustomed to make O-ring seals. This elastomer is proof against animal and vegetable fats, in addition to most oils and solvents. However, O-ring seals made out of this material are typically not suggested for applications which entail contact with ketones, esters, aromatic hydrocarbons, and powerful oxidizing acids.
At present, natural rubber O-rings are rarely used as a result of introduction of synthetic elastomers, like Nitrile rubber and Viton. Natural rubber may be used with animal oils, vegetable oils, and the majority of oxidizing chemicals. However, it is far from suitable for use with oils, petroleum solvents, aromatic hydrocarbons, and also in applications that demand exposure to sunlight or ozone.
These listed materials are commonly used elastomers for producing O-rings, but other materials, including Kalrez, will also be used in certain special applications. Kalrez is an ideal replacement for Viton in applications which have operating temperatures as much as 500 degrees F. Similarly, there are various other elastomers utilized for specific sealing purposes. No matter what the material you select for your application, care needs to be taken to ensure its compatibility with operating temperatures, fluids, and environment.
The criticality of determing the best material for your application is immediately apparent whenever we consider the reason for Space Shuttle Challenger disaster. This tragedy was a result of the failure of your O-ring that lost its elasticity and have become brittle because of an unexpected drop in ambient temperature. Though most O-ring failures might not exactly result in the loss of life at par using this disaster, there is not any denying the definite economic loss caused by a failed machine or device.