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gasket seals
Polyurethane is generally the material of choice to create longevity in products due to its resistance to abrasion and performance in harsh environments. Components used in specialty seals and other sealing systems that were traditionally metallic in nature have largely been replaced with thermoplastic materials that offer greater resilience, improved frictional properties, improved resistance to wear, weathering and oxidation, and overall improved aesthetics.Rubber has its own unique array of available materials and associated properties, and can be produced in almost any conceivable configuration, including bonding to metal components and various application-specific seal systems. Rubber materials possess some physical properties that are superior to many plastics, and can provide several advantages, including compression set resistance, thermal conductivity, and resistance to fluid swell.
High performance o-rings are arguably one of the simplest yet most engineered, precise, and useful seal designs ever developed. Though tiny compared to other machine components, o-rings are one of the most common and important elements of machine design. They are available in various metric and inch standard sizes. Sizes are specified by the inside diameter and the cross section diameter (thickness).
In the United States the most common standard inch sizes are per SAE AS568B specification (i.e. AS568-214). ISO 3601-1:2008 contains the most commonly used standard sizes, both inch and metric, worldwide. The UK also has standards sizes known as BS sizes, typically ranging from BS001 to BS932. Several other size specifications also exist.
Successful o-ring joint design depends on rigid mechanical mounting that applies a predictable deformation to the o-ring. This introduces a calculated mechanical stress at the o-ring contacting surfaces. As long as the pressure of the fluid being contained does not exceed the contact stress of the rubber o-rings San Diego experts explain, leaking cannot occur. Fortunately, the pressure of the contained fluid transfers through the essentially incompressible o-ring material, and the contact stress rises with increasing pressure. For this reason, an o-ring can easily seal high pressure as long as it does not fail mechanically. The most common failure is extrusion through the mating parts.
Seals are designed to have a point contact between the o-ring and sealing faces. This allows a high local stress, able to contain high pressure, without exceeding the yield stress of the o-ring body. The flexible nature of o-ring materials accommodates imperfections in the mounting parts. But it is still important to maintain good surface finish of those mating parts, especially at low temperatures where the seal rubber reaches its glass transition temperature and becomes increasingly crystalline. Surface finish is also especially important in dynamic applications. A surface finish that is too rough will abrade the surface of the o-ring, and a surface that is too smooth will not allow the seal to be adequately lubricated by a fluid film. For additional information about sealing systems and machine components, please visit http://www.real-seal.com/ to learn more.
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