O-Rings and Back-up Rings

An O-ring is a donut-shaped ring made of molded, flexible material with a round cross-section that can be either solid or hollow.  These pliable rings are designed to be inserted into a groove, referred to as a gland, where they predictably re-form themselves to completely fill the gap in the cavity – creating the perfect seal.

Web Seal provides O-rings in all standard AS568 and metric sizes, and in more than 30 elastomer and fluoroplastic/PTFE (Teflon™) types.   You can also request custom sizes and unique compounds for your specific applications.

Back-up rings are used in high-pressure applications to prevent the O-ring from extruding. Glands can be designed to contain either one or two back-up rings.

• Rubber back-up rings are typically made from 90 durometer materials and are solid
• Teflon™(PTFE) back-up rings are manufactured to meet a variety of MIL-Specs (US Department of Defense) standards and are available in solid, split or spiral configurations
• Back-up rings can be installed on one or both sides of the flexible seal
• A wider gland is required to accommodate the extra seal material

When a standard O-ring cannot be used, a spliced O-ring is a workable solution in static applications. Custom O-rings are fabricated from extruded cord and then vulcanized to form the ID (inside diameter) size required.  This process allows for custom sizes other than a standard molded O-ring.  Web Seal can provide spliced O-rings from cord in standard and metric sizes, and can be round, rectangular or another custom shape, depending on your gland design. Typical cord stock material includes:

To order O-rings, you need to specify:

1. Size
   • ID (inner diameter)
   • OD (outer diameter)
2. Material
   • Elastomer (compound)
   • Durometer (hardness)

Example

Size:  2-210
Compound:  Nitrile 70 durometer

Click here for a list of standard O-Ring sizes.

Material selection depends on your application. Our Elastomer Materials page and our Additional Materials page provide excellent guidance for your material choice.  Every application comes with its own set of service and environmental conditions.  Typically, O-rings are made from an elastomeric composite with unique characteristics, but they can also be plastic or metallic.

Please also consult our O-Ring Material Temperature Guide when researching or specifying for your O-ring order.

And, of course, please call or email us if you need assistance with non-standard sizes or material options for your specific application.