Why Do O-Rings Fail?

To define simply, o-rings are simple yet critical components in the shape of ‘o’ that are used to create a seal between two surfaces to prevent leakages. 

However, like any mechanical component, they can fail at times for various reasons. It’s very important for users to understand this because knowing the cause makes it easier to change the design/seal material to ensure its longevity and effectiveness.  

In the list below, we identify various types of o-rings failures and how they can be prevented before they result in costly losses: 

1. 1. Design Failure 

WHAT No visual damage. Performance failure. 
WHY Incorrect groove or gland design. Improper sizing. Incorrect tolerances. Hardware damage or misalignment. Improper mating surface finishes. 
HOW TO PREVENT Proper groove dimensions. Appropriate tolerances. Optimising the size or gland design for the particular application. 

2. 2. Abrasion 

WHAT Light scratches. Deep cuts. Cropped surface.
WHY Dynamic environments. Repetitive friction. Excessive temperature. Inadequate lubrication. 
HOW TO PREVENT Maintain proper lubrication. Eliminating abrasive elements. 

3. 3. Chemical Degradation 

WHAT Cracks. Blisters. Stains. Discoloration. Hardening. Swelling.
WHY Incompatibility with the chemical environment. High temperature. Excessive pressure. 
HOW TO PREVENT Use the right o-ring material that is highly resistant against specific chemicals within the application. Regular monitoring. 

4. 4. Plasma Degradation

WHAT Discoloration. Powdered residue on the surface. Erosion in the exposed areas. 
WHY Chemical reactivity of the plasma. Ion bombardment. Electron bombardment. Improper gland design. Incompatible material. 
HOW TO PREVENT Plasma compatible elastomer and compound. Minimise exposed area. Be careful of the gland design. 

5. 5. Compression Set 

WHAT Failure to return to its original shape. Permanent deformation. 
WHY High temperatures. Stress. Tight groove. Excessive compression. Incompletely cured elastomer. Elastomer with high compression set. 
HOW TO PREVENT Higher durometer. Higher operating temperature. Proper o-ring groove design. Backup rings. Low compression set elastomer. Material compatibility. Use appropriate compression levels. 

6. 6. Over Compression 

WHAT Parallel flat surfaces. Circumferential splits within the flattened surfaces. 
WHY Improper design. Excessive compression. Not resistant to thermal or chemical volume changes. 
HOW TO PREVENT  Proper gland design. Right response to chemical and thermal environments. 

7. 7. Explosive Decompression 

WHAT  Blisters. Pits. Pocks. 
WHY  Rapid pressure changes. Elastomer with low hardness. 
HOW TO PREVENT  Elastomer with higher hardness. Slower release of pressure. ED resistant material. 

8. 8. Installation Damage 

WHAT Indentations on the outer edge of the o-ring surface. 
WHY Improper lubrication. Installation in applications with sharp edges. Size too big or small to fit in its groove. 
HOW TO PREVENT Taping sharp edges. Lubrication. Proper elastomer sizing. Proper gland design. 

9. 9. Extrusion 

WHAT Nibbled or ragged edges receiving lower pressures. 
WHY High pressure. Excessive clearances. Excessive gland fill. Irregular clearance gaps. Sharp gland edges. Unsuitable dimensions. Improper material. 
HOW TO PREVENT Higher durometer. Use of backup rings. Decrease clearances. Use of harder seal material. Proper gland design. Decrease sharp edges of the gland. Appropriate gland design. 

10. 10. Outgassing 

WHAT No visible difference. Slight reduction in cross-sectional size in rare cases. 
WHY Low plasticized elastomer. High vacuum levels. Improperly cured elastomer. 
HOW TO PREVENT  Right material. Proper temperature ranges. Avoid plasticized elastomers. Post-cured seals. 

11. 11. Rapid Gas Decompression 

WHAT Cracks. Blisters. Deep cuts. Might blow out entirely in the worst-case scenario. 
WHY Exposure to gas at high pressures and temperatures for an extended amount of time. 
HOW TO PREVENT Use Rapid Gas Decompression (RGD) o-rings. 

12. 12. Spiral Failure 

WHAT Deep cuts or marks spiralling around the outer surface. 
WHY Tight installation. High friction. Inadequate lubrication. Inconsistent surface. Excessive gland width. 
HOW TO PREVENT  Higher durometer. Using x-rings. Correct installation procedures. Internally lubed elastomers. Proper gland design. Use of polymer backup rings. 

13. 13. Thermal Degradation 

WHAT Rounded cracks along the surface. Softening. 
WHY High temperature. Thermal properties of the elastomer. 
HOW TO PREVENT Elastomer with enhanced thermal stability. 

14. 14. Thermal Extrusion 

WHAT Nibbled or ruffled edges. Extrusion on the lower-pressure side of the o ring. 
WHY Higher temperature. 
HOW TO PREVENT Proper groove design. Resistance of material to high temperature. 

15. 15. UV Degradation 

WHAT Discoloration. Cracking and breaking in some cases. 
WHY Exposure to UV rays for prolonged period of time 
HOW TO PREVENT Using EPDM o-rings and Viton® o-rings in black color. 

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