An O-ring is a mechanical gasket that is seated in a groove and held in place by compression. They are used between two mating parts to create an air tight or fluid tight seal. O-rings are one of the most common types of seals used in machine design. O-rings are constructed in a donut shape and are available in a wide range of materials and sizes (both metric and standard) for various applications.

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What types of materials are used in making O-Rings?

Because of the wide variety of applications O-rings are used in, a wide range of materials can be used in their construction. Some of the factors to be considered are temperature requirements, pressure requirements and chemical compatibility. Along with these considerations other factors such as critical applications and how much durability is required will also play a role in material selection. Most O-rings are made of some type of rubber, usually a synthetic compound. Some of the most common types used in industrial applications are Buna-N, Viton, Butyl rubber, Nitrile and Silicone Rubber. Thermoplastics are also sometimes used in the production of O-rings, the most common types being Polyurethane and Polyamides.

How are O-Rings used?

O-rings are primarily designed as a seal against air, gas or fluids. The O-ring is in place to keep a seal between two or more mated parts. Applications are used in a wide range of mechanical assemblies in almost every industrial and mechanical application. O-rings are made of flexible materials so they can be used, under the correct amount of installation pressure to withstand very large amounts of stress and internal pressure of the gas of fluid being contained. O-rings can also be used as a pivot point in a mechanical assembly provided they are properly lubricated.

How are O-Rings measured?

O-rings are measured in three critical dimensions. These are internal diameter, outside diameter and thickness. Each of these three dimensions must match exactly the mounting surface and application for the O-ring to function properly. Any slight deviation from the optimum dimensions will create a situation were the O-ring may leak or fail. Always insure you are using the correct size O-ring for each specific application.