A seal is a type of device that joins systems together by preventing leakage, keeping out contamination, and containing pressure. There are many various different types of seals, such as diaphragm seals, plumbing seals, and gaskets. The semiconductor industry in particular uses a specialized type of seal called an o-ring.

An o-ring is a type of seal made from a piece of elastomer looped in a circle with a round, o-shaped cross-section. It is simple but one of the most highly critical precision components ever invented. Its design allows it to be seated in a groove so that it can be compressed during assembly between two or more parts. This creates a sale at the interface level.

Sometimes the joint of the o-ring is static or have a relative motion between the o-rings parts. This could be something along the lines of rotating pump shafts in conjunction with hydraulic cylinders or another such example. Therefore, these joints that involve motion normally require some type of lubricant in order to prevent and reduce wearing of the o-ring. Normally this is done with the fluid that is being sealed, but sometimes it may require a better lubricant.

O-rings are perhaps the most common of all seals used in machine design. This is because they are not only inexpensive but also reliable, have simple mounting requirements, and are easy to make. They also are very efficient and can seal up to tens of megapascals pressure.

O-rings require a rigid mechanical mounting in order for the seal to be effective. It must apply a predictable deformation to the o-ring so that it will seal everything correctly. This provides mechanical stress at the o-ring’s contacting surfaces. If the pressure of the fluid being contained does not exceed the contact stress of the o-ring, leaking will not occur and the seal will be successful.