‘O’ Rings & Related Products
The O-ring is the most common type of fluid seal. An O-ring’s simple design lends itself to a multitude of sealing uses, including static, reciprocal, oscillating, and dynamic applications at low speed and pressure. In elevated operating pressure environments, addition of a backup ring will greatly increase the extrusion resistance of an O-ring.
The most basic shape of an O-ring is a simple circular sealing torus, usually made from an elastomeric material. Beyond the standard O-ring, CBS can supply more advanced sealing designs such as Quad Rings®, which are specially designed for low pressure sealing. CBS also offers O-rings in advanced materials such as Viton®, Silicone®, and Teflon®.
There are several different standards to choose from when it comes to O-ring dimensions. The most popular is the AS568 standard for O-ring sizes and tolerances. Maintained by the Society of Automotive Engineers, this standard allows the user to choose from five different cross-sections with inside diameters ranging from 1/32″ to 26″. Tube fitting boss seals are included in AS568 as 900 series O-ring sizes, and are intended for use in MS33649 (now superseded by SAE-AS5202) straight thread tube fitings.
CBS offers a wide array of metric sizes, in both standard and non-standard dimensions. If an O-ring with special size or fluid resistance is required, CBS can provide custom O-rings, specially made to your demanding requirements.
Call us for your ‘O’ Ring or related product requirements.
Quad Rings® are four-lobed seals with a geometry that provides twice the number of sealing surfaces when compared to that of a standard O-ring. Thus, damage to any particular lobe will be much less likely to cause seal failure. Twice the number of sealing surfaces also allows a Quattro Seal to seal at lower pressures and/or less interference than would be feasible with an O-ring.
The four-lobed configuration also creates a more stable seal that reduces the likelihood of spiral twisting in reciprocal applications. This is because than rather than relying solely on squeeze to achieve a seal like an O-ring, a Quad Rings® employs both squeeze and deflection to affect a seal. Quad Rings® can be used in standard O-ring grooves or used in deeper Quad Rings® specific grooves, resulting in less friction and longer seal life. Quad Rings® grooves can also be narrower than O-ring grooves, as spiral failure is less of an issue.
Teflon® Encapsulated O-rings
Elastomeric, rubber O-rings suffer from high friction and limited resistance to aggressive chemicals and gas permeation. Solid Teflon® O-rings are rigid with no effective memory and high compression set. CHEM-RING Teflon Encapsulated O-rings combine the resilience and sealing force of an elastomer with the chemical resistance of Teflon®. This is accomplished by the use of an elastomeric core of silicone or Viton®, with a relatively thin encapsulation of Teflon® FEP or PFA polymer. This produces an elastomeric PTFE seal with maximum sealing capability.
FEP Encapsulated O-rings are solvent resistant and chemically inert (except for attack by alkaline metals, fluorine and some halogenated compounds at high temperatures) yet have an elastomeric memory near that of rubber O-rings. FEP polymer, also, has an extremely low coefficient of friction (.1 to .2) and very low permeability to gases, making CHEM-RINGS a virtually universal seal for use in hostile environments.
Extrusion failure is one of the most common types of O-ring failure. When the internal pressure of an application becomes too great, the O-ring will actually extrude into the clearance gap. This extrudate will quickly be nibbled away causing a loss of material, and once sufficient material is lost, seal failure will quickly follow.
There are three options to prevent this, the first of which is to reduce the clearances to lower the extrusion gap. This is obviously an expensive option, so a cheaper solution is to raise the durometer of the O-ring. Although, a higher durometer O-ring offers superior extrusion resistance, is often not feasible solution due to material availablilty, and to the fact that harder durometer materials have limited low pressure sealability. The last and best option is the addition of a backup ring. A backup ring is a ring of hard, extrusion resistant material such as high durometer nitrile, nylon, Hytrel, or PTFE. A back-up ring is designed to fit between the O-ring and the extrusion gap and prevent the extrusion of the O-ring.
While back-up rings are used in conjunction with O-rings in both static and dynamic sealing applications, the gland they fit in must be specially designed to fit both the O-ring and the back-up.
CBS offers O-ring kit assortments in numerous shapes and sizes. Materials offered range from standard compounds such as multipurpose nitrile (Buna-N) rubber, to more exotic materials such as Viton® (generically called fluorocarbon) and Teflon® (also called PTFE). All CBS O-ring kits come in sturdy plastic containers for easy keeping in your workshop.