O-Rings
An O-ring is the foundational sealing element in countless static and dynamic applications. Performance Sealing Inc. (PSI) manufactures custom elastomeric O-rings engineered for extreme-demand environments — from cryogenic instrumentation and semiconductor processing to high-pressure hydraulics and turbine engines.
PSI O-rings are produced in a range of high-performance elastomer materials, with each formulation selected for its specific compatibility with temperature extremes, chemical media, and pressure requirements. Where standard O-rings fail, PSI engineers a solution.
How O-Rings Work
An O-ring is a doughnut-shaped ring made from a soft, flexible elastomer. When compressed between two mating surfaces in a machined groove, the elastomer deforms to fill microscopic surface imperfections, creating a barrier that blocks the passage of fluids or gases. The seal is created and maintained entirely by compression — no adhesives, no fasteners.
O-rings are used in both static applications (where neither mating surface moves) and dynamic applications including reciprocating, oscillatory, and slow-speed rotary motion.
O-Ring Materials
Material selection is the most critical factor in O-ring performance. PSI manufactures O-rings in the following elastomers:
FFKM (Perfluoroelastomer)
- Broadest chemical resistance of any elastomer — compatible with nearly all media
- Operating temperatures up to 600°F (315°C)
- Excellent plasma resistance for semiconductor and vacuum applications
- Near-zero outgassing for clean-room and analytical environments
FKM (Viton®)
- Superior fuel, oil, and hydrocarbon resistance
- High-temperature capability for aerospace and industrial service
- Excellent resistance to aggressive chemicals including acids and solvents
EPDM
- Outstanding resistance to steam, hot water, and ozone
- Preferred for applications with phosphate ester hydraulic fluids
- Good low-temperature flexibility
Nitrile (NBR)
- Standard choice for petroleum-based hydraulic oil and general industrial service
- Good abrasion resistance in dynamic applications
- Cost-effective for high-volume applications
Silicone
- Broad operating temperature range from -65°F to 450°F
- Low compression set for long-duration static sealing
- Preferred in food-grade and medical device applications
O-Ring Applications
PSI O-rings serve critical sealing functions across a wide range of industries and equipment types:
- Gas compressors
- Booster pumps
- Turbine engines
- HPLC instrumentation
- Relief valves and choke valves
- Aerospace and defense systems
- Medical devices and diagnostic equipment
- Semiconductor processing equipment
- Energy, oil, and gas production
O-Ring Limitations & When to Add a Back-Up Ring
Under standard operating conditions, an O-ring provides reliable, long-service sealing. However, when pressure is high enough to force the O-ring material into the gap between mating components — a process called extrusion — the O-ring is sheared or nibbled, leading to premature seal failure.
A back-up ring should be used alongside an O-ring in the following situations:
- System pressure exceeds 1,500 PSI (100 bar)
- Extrusion gaps are large due to manufacturing tolerances
- Elevated temperature softens the O-ring, lowering its resistance to extrusion
- Dynamic (reciprocating) motion causes repeated contact at the extrusion gap
In bidirectional pressure applications, a back-up ring on each side of the O-ring is required. PSI manufactures both O-rings and back-up rings and can engineer a complete sealing system for your application.
O-Ring FAQs
What is an O-ring and how does it work?
An O-ring is a doughnut-shaped elastomeric seal that creates a leak-proof barrier by compression. When installed in a groove and squeezed between two mating surfaces, the soft elastomer fills microscopic surface imperfections, blocking the passage of fluids or gases. O-rings are used in both static (non-moving) and dynamic (reciprocating, rotary) sealing applications.
What O-ring materials does Performance Sealing Inc. offer?
PSI manufactures O-rings in FFKM (perfluoroelastomer) for maximum chemical resistance, FKM (Viton®) for high-temperature fuel and oil service, EPDM for steam and water applications, nitrile (NBR) for general hydraulic and pneumatic service, and silicone for wide temperature range applications. Material selection is driven by media compatibility, temperature, and pressure requirements.
What is O-ring extrusion and how is it prevented?
O-ring extrusion occurs when system pressure forces the soft elastomer into the gap between mating components, causing the O-ring to be sheared or nibbled over time and leading to seal failure. Extrusion is prevented by installing a back-up ring — a hard PTFE or PEEK ring placed on the low-pressure side of the O-ring that physically blocks the extrusion gap.
What applications are PSI O-rings used in?
PSI O-rings are used in gas compressors, booster pumps, turbine engines, HPLC instrumentation, relief valves, and choke valves. Industries served include aerospace, medical, energy and oil and gas, semiconductor equipment, and general industrial equipment.
When does an O-ring need a back-up ring?
A back-up ring should be used alongside an O-ring when: system pressure exceeds 1,500 PSI; extrusion gaps are large; elevated temperature softens the elastomer; or the application involves dynamic (reciprocating) motion. In bidirectional pressure applications, a back-up ring on each side of the O-ring is required.
Contact our technical sales staff today to discuss your application's operating, hardware, and commercial conditions to develop the best-performing seal solution.
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