What Are O-Rings?
An O-ring, also known as a packing, or a toric joint, is a gasket in the shape of a torus, or doughnut shape. It is a loop of elastomer with a round cross-section, designed to be seated in a groove and/or compressed during assembly between two or more parts, creating a seal. The O-Ring may be used in static or dynamic applications where there is relative motion between the parts and the O-Ring.
O-ring Specs & Certifications
- AS568 (2-XXX, 3-XXX, 5-XXX Sizes)
- FDA and USP Class VI
- Mil, AMS and NAS Spec
- NSF 51, NSF 61 and UL Listed
High-Temperature O-Rings Colors
O-rings are manufactured in standard or inch sizes, and metric sizes and can be made from almost any elastomer. The most commonly used is Buna (also called nitrile). Buna is used often because of its strong mechanical properties, resistance to lubricants and greases, and relatively low cost. Other elastomers are also used based on their resistance to certain chemicals or various high or low-temperature ranges, adding a myriad of design and application factors.
Elastomers that are used most commonly used, include:
- Viton (FKM)
- EPDM (EPR)
- Silicone (SiR)
- Highly Saturated Nitrile (HSN)
- PTFE (a generic compound of Teflon™, a trademark of The Chemours Company)
- PTFE Coated (PTFE coated, usually Silicone or Viton)
- PTFE Encapsulated (Usually Silicone or Viton covered with a PTFE tube)
- Kalrez, Chemraz, Simriz (FFKM)
- Aflaz (TFE/P)
- Custom compounds and formulations
High-temperature 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.
These are not the only elastomers available but are used most often. Elastomers can be compounded with different properties for different chemical capabilities, high or low-temperature gradients, hardness, and many other factors an O-Ring may encounter during its life cycle.
Types of O-Rings and related categories include: