Ask the Experts

Ask the Experts: How Can Compression Set Cause a Seal to Fail?

Sometimes an elastomeric material fails to return to its original size after release from a constant compressive load.  The amount of material that fails to return to its original size is called a compression set.  This type of failure is common to both static and dynamic seals.  Compression set failure produces flat surfaces on both sides of the O-ring’s cross-section, which reduces its sealing potential.

Curious as to what causes compression set failure?  Wonder no more.
Causes include:

• Selection of elastomer with poor compression set properties
• Low heat resistance of the material
• Excessive swelling of material in system fluid
• Too much squeeze to achieve the seal
• Incomplete curing (vulcanization) of O-ring material during production

Experiencing these problems? Here are some suggested solutions:

• Employing a low set elastomer
• Specifying an O-ring material that resists both operating and friction generated heat
• Checking the material compatibility with system fluid and chemicals
• If possible, try reducing O-ring squeeze
• Inspecting O-rings for correct physical properties

When you’re designing for sealing applications, formulas can act as a guide for calculating minimum and maximum O-ring compression.  If you’re still stuck, contact our online expert for additional design assistance.