What is compression set and how can it cause a seal to fail?

Compression set is the amount by which an elastomeric material fails to return to its original size after release from a constant compressive load. 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.

Causes of compression set failure may include:

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

Some suggested solutions include:

• 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
• Reducing O-ring squeeze if possible
• Inspecting O-rings for correct physical properties

Formulas act as a guide for calculating minimum and maximum O-ring compression when designing for sealing applications. (The formulas should be used as a guide only.) For additional design assistance, contact our on-line expert today.