Design
O-Ring Extrusion Calculator
Estimate extrusion risk from the combination of pressure, clearance gap, elastomer hardness and temperature.
Loading calculator…
Loading calculator…
Calculator guidance and result interpretation
What this calculator solves
Pressure pushes elastomer into the low-pressure clearance gap. This tool screens the gap-hardness-pressure combination and shows when support or a back-up ring should be considered.
When to use it
- •High-pressure hydraulic seals
- •Static and reciprocating radial glands
- •Tolerance and bore-expansion review
Input parameters
- Clearance gap
- Maximum diametral gap including machining tolerance, eccentricity and pressure expansion.
- Pressure
- Peak differential pressure, including spikes where relevant.
- Material state
- Hardness and temperature that determine resistance to being forced into the gap.
How to read the results
- The allowable-pressure estimate is a screening limit for the entered gap and hardness.
- Safety factor compares the estimated allowable pressure with the entered differential pressure.
- A high-risk result points to gap reduction, higher hardness or anti-extrusion support.
Engineering considerations
- Use the worst-case clearance, not only the nominal machining gap.
- Hot elastomers are generally less resistant to extrusion.
- Pressure cycling, edge geometry and dynamic wear can require more margin than a static screening curve.
Related tools and engineering resources
Frequently asked questions
What causes O-ring extrusion?
Differential pressure pushes the elastomer into a clearance gap. Risk increases as pressure and gap grow or material hardness falls.
When should I use a back-up ring?
Consider one when the required pressure cannot be supported by practical clearance and hardness, especially with pressure cycling or bidirectional pressure.