Failure Pattern
Typical of high-pressure systems, extrusion and nibbling can be identified by the many small bites (nibbles) taken from the O-ring on the low-pressure (downstream) side.

Problem Sources

• Excessive clearances
• Excessive system pressure
• O-ring material too soft
• Degradation of O-ring by system fluid
• Irregular clearance gaps caused by eccentricity
• Improper machining of O-ring gland (sharp edges)
• O-ring size too large for gland

Suggested Solutions

• Decrease gland clearances by machining
• Use back-up rings to prevent extrusion
• Use harder O-ring material
• Re-check elastomer compatibility with system chemicals
• Increase rigidity and improve concentricity of metal components
• Break sharp edges of gland to a minimum radius of .005"
• Install proper size O-ring
• Consider a reinforced composite seal such as rubber-bonded-to-metal

O-RING RULE OF THUMB #11

Static seal cross-sections are generally compressed from 10% to 40%, whereas dynamic seals are from 10% to only 30%. » Learn More