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Rubber O Rings
An O-ring, also known as a packing, or a toric joint, is a mechanical gasket in the shape of a torus; it is a loop of elastomer with a round cross-section, designed to be seated in a groove and compressed during assembly between two or more parts, creating a seal at the interface.

The O-ring may be used in static applications or in dynamic applications where there is relative motion between the parts and the O-ring. Dynamic examples include rotating pump shafts and hydraulic cylinder pistons. Static applications of O-rings may include fluid or gas sealing applications in which: (1) The O-ring is compressed resulting in zero clearance, (2) The O-ring material is vulcanized solid such that it is impermeable to the fluid or gas, and (3) The O-ring material is resistant to degradation by the fluid or gas.

O-rings are one of the most common seals used in machine design because they are inexpensive, easy to make, reliable and have simple mounting requirements. They have been tested to seal up to 5000 psi (35 megapascals) of pressure. The maximum recommended pressure of an O-ring seal depends on the seal hardness and gland clearance.

O-ring selection is based on chemical compatibility, application temperature, sealing pressure, lubrication requirements, durometer, size and cost.
  • Synthetic rubbers - Thermosets
  • Butadiene rubber (BR)
  • Butyl rubber (IIR)
  • Chlorosulfonated polyethylene (CSM)
  • Epichlorohydrin rubber(ECH, ECO)
  • Ethylene propylene diene monomer (EPDM): good resistance to hot water and steam, detergents, caustic potash solutions, sodium hydroxide solutions, silicone oils and greases, many polar solvents and many diluted acids and chemicals. Special formulations are excellent for use with glycol-based brake fluids. Unsuitable for use with mineral oil products: lubricants, oils, or fuels. Peroxide-cured compounds are suitable for higher temperatures.

Varieties and Materials
Although O-rings are typically circular, different shapes are used for various applications including squares, X-shapes and others. O-Rings are produced using a variety of manufacturing techniques like extrusion, compression molding, injection molding, transfer molding or machining. Depending on the application, they can be made from a plethora of materials: nitrile rubber, silicone, polyurethane, neoprene, fluorocarbon as well as other elastomers. O-Ring design considers quality, quantity, cost, application temperature, sealing pressure, chemical compatibility, movement, action, lubrication and other requirements.
Common O-Ring Applications
In industries like passenger automotive, heavy duty trucking, and aerospace, severe conditions call for high performance products. Chemical exposure, extreme temperatures and vibration are all factors that affect elastomer selection for O-Rings. Custom compounds have been produced to meet strict OEM and Tier 1 specifications and are continually refined to adhere to biofuel and emissions requirements.

In the medical field syringe, pump, filtration and connectors require specialty FDA grade O-Rings.

Oil, Gas & Industrial
Valves, gas pumps, fittings, dispensers and storage tanks need sealing solutions that can withstand extreme temperatures, noxious chemicals, and high compression. Specialty compounds like peroxide and triazine-cured perfluoroelastomers assure heat and chemical resistance.

Semiconductor processing and dust protection in consumer electronics call for O-Rings to be manufactured in clean environments. Particulate and contaminant-free O-Rings are available in a wide range of compounds.

Food & Beverage
Specialty 3A sanitary, NSF-61 and water service O-Rings and seals are ideal for the food processing, beverage dispensing and water filtration markets.

Advantages of O rings
They seal over a wide range of pressure, temperature and tolerance.
  • Ease of service, no smearing or retightening.
  • No critical torque on tightening, therefore unlikely to cause structural damage.
  • O-rings normally require very little room and are light in weight.
  • In many cases an O-ring can be reused, an advantage over non-elastic flat seals and crush-type gaskets.
  • The duration of life in the correct application corresponds to the normal aging period of the O-ring material.
  • O-ring failure is normally gradual and easily identified.
  • Where differing amounts of compression effect the seal function (as with flat gaskets), an O-ring is not effected because metal to metal contact is generally allowed for.
  • They are cost-effective.