An O-ring is a simple but critical sealing element with a circular cross-section, shaped like a ring. Despite its simple geometry, choosing the wrong material or size can lead to leakage, premature wear, or complete failure in a system.
How Does an O-Ring Work?
When placed between two surfaces, an O-ring is slightly compressed, and this compression provides the seal. It can be used in static applications (between fixed parts) and dynamic applications (between moving parts, such as pistons), though each case involves different design and material requirements.
Choosing the Right Size
- Correctly determining the inner diameter, outer diameter, and cross-section (cord diameter)
- Ensuring the compression ratio suits the application
- Making sure the gland design is compatible with the O-ring size
- Conforming to standard size series (such as AS568) for easier sourcing
Material Selection Considerations
O-ring material should be chosen based on the application’s temperature range, the fluids it will be exposed to (oil, water, chemicals, gas), and pressure conditions. NBR is commonly preferred for oil applications, EPDM for water and weathering, and FKM for applications requiring high temperature and chemical resistance.
Common Causes of Failure
- Chemical or heat damage due to incorrect material selection
- Incorrect sizing or compression ratio
- Mechanical damage during installation (cutting, scratching)
- Loss of sealing due to compression set
Alpin Rubber produces O-rings and custom sealing elements across a range of materials and sizes suited to its customers’ application conditions.