O-Rings
O-rings are circular elastomer seals with a round cross-section, fitted in a groove to seal static and dynamic joints. We supply standard metric and AS568 inch sizes and special sizes in NBR, FKM (Viton), EPDM, silicone and other compounds.
What it is
An O-ring seals by being squeezed in its groove; system pressure pushes it against the gap for a tighter seal. Size is defined by inner diameter and cross-section, and hardness by Shore A (commonly 70 or 90).
Material is chosen by fluid compatibility and temperature; back-up rings prevent extrusion at high pressures.
Typical applications
- Hydraulic and pneumatic fittings
- Pumps and valves
- Food and pharma equipment
- Automotive systems
- Enclosure and lid seals
Materials & grades
- NBR (nitrile)
- FKM (Viton)
- EPDM
- Silicone
- FFKM, PU, HNBR (specialist)
Points to consider
- Check fluid compatibility; EPDM must not contact mineral oils.
- Groove design determines squeeze and seal life.
- Use back-up rings above around 100 bar in dynamic service.
- Food-grade compounds need FDA compliance.
Frequently asked questions
How is an O-ring size specified?
By inner diameter and cross-section (for example 20 × 2.5 mm) or an AS568 dash number.
Which O-ring material should I use?
NBR for oils, FKM for high temperature and fuels, EPDM for water and steam, silicone for food and wide temperatures.
What is Shore A hardness?
A measure of rubber hardness; 70 Shore A is general purpose, 90 for high pressure.