O-RINGS & X-RINGS
OVERVIEW
Both O-rings and X-rings are often referred to by the collective term “seals.”
Sigma Seals & Gaskets’ experienced engineers will custom tailor a seal to fit your exact requirements, and manufacture 1 or 1,000 seals to your specifications that same day.
O-rings are sized to the SAE standard AS568, which is known as a dash number. Metric O-rings are sized to the actual measured inside diameter. Custom sizes can be developed to suit your applications.
Design Considerations
During operation, the O-ring or X-ring is seated in a specially shaped groove (gland) at the interface between two rigid components. When the components are forced closer together, the seal is compressed against the walls of the gland and creates a plug. If a pressure differential occurs across the gland, then the seal is compressed against the low-pressure side of the gland. If the pressure difference is too great, then the seal will extrude into the narrow gap between the walls of the gland, and the seal will fail.
In dynamic applications, a seal can also fail by abrasion against the walls of the gland. In such situations, the walls should be polished to prolong the life of the seal.
For maximum seal longevity, the seal must be constructed from the correct elastomer for the particular application. Sigma Seals & Gaskets can build seals from elastomers that tolerate high or low temperatures, high or low pressures, dynamic applications, and corrosive environments. If you are unsure which material would be best, ask us—we can help you select the right material for your situation.
O-Rings
Provide a simple and effective seal that can be used for thousands of applications. O-rings are manufactured in an array of materials to match any design needs.
X-Rings
Quad Seals allow for a narrower gland over standard O-rings. These are well suited for use on high and pulsating pressure applications and can a wide variety of static and dynamic sealing applications.
| Material | Temperature Range (°F)* | Comments and Typical Uses |
|---|---|---|
| Nitrile (Buna-N, NBR) | -20 to 212 | Highly resistant to abrasion and tearing. Nitrile is the most commonly used elastomer for sealing applications, and it is the material of choice for petroleum applications. |
| Hydrogenated nitrile (HNBR) | -20 to 300 | Compared to nitrile, HNBR has better chemical resistance, better heat resistance, and better resistance to seal extrusion. |
| Ethylene-propylene (EPDM) | -60 to 250 | Very resistant to ozone. |
| Neoprene | -40 to 250 | Resists both weathering and exposure to petroleum oils. |
| Butyl (isobutylene, IIR) | -50 to 250 | Extremely low gas permeability; resists a diverse range of chemicals. Useful in applications requiring an air-tight seal. |
| Viton® (fluorocarbon, fluoroelastomer) | -15 to 400 | Better resistance to chemicals and high temperatures than most other elastomers. |
| Silicone (VMQ, PVMQ) | -150 to 400 | Excellent tolerance for temperature extremes, and high resistance to compression set. |
| Fluorosilicone (FVMQ, FK) | -75 to 400 | Tolerant to temperature extremes, and resists degradation by fuel and oils. Primarily used where resistance to hot, dry conditions is required. |
| FFKM (perfluoroelastomer) | -15 to 600 | Highly resistant to many chemicals, and outstanding resistance to high temperatures. |
| PTFE | -400 to 450 | Highly resistant to many chemicals, and can function over a very wide temperature range. Also resists weathering. |
* Temperature ranges given here are approximate; the values relevant to any particular situation depend upon the application. If in doubt, ask us—we will help you design a backup ring to meet the temperature tolerance needs of your system.
Applications
- High or low temperatures
- High or low pressures
- Static or dynamic systems
- Corrosive environments
Benefits
• Both types of seals provide a simple, inexpensive, and effective plug for many applications
• A wide variety of forms and sizes fabricated from custom materials to meet the exact needs of the application
• X-rings are ideal for dynamic and extreme pressure applications
• O-rings with back up rings increase the effective pressure range of the O-ring
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QUALITY GUARANTEE
Sigma Seals & Gaskets specializes in quality elastomeric products. With over 100 years of engineering expertise we are dedicated to offering the highest quality elastomeric products as well as other products. For your custom quality product design or reverse engineering, our exemplary service and efficient production ensures prompt deliveries coupled with outstanding service.