Rules of Thumb

Exploring Common Causes of O-Ring Failure

O-Rings are vital to sealing applications, and their failure can lead to system downtime and safety risks. In this blog, we address the most common reasons behind o-ring failures and offer practical solutions. From compression set issues to chemical attacks and temperature variations, we explore the challenges o-rings face and provide insights to ensure these seals perform reliably in your applications. By the end of this guide, you’ll be well-equipped to prevent o-ring failures and maintain system integrity1. Compression Set:

1. Compression Set

Problem Sources:

  • Selection of an elastomer with poor compression set properties.
  • Low heat resistance.
  • Excessive swelling of o-ring in system fluid.
  • Too much squeeze.
  • Incomplete curing during production.
  • High operating temperature.

Possible Solutions:

  • Select a low set elastomer with better compression set properties.
  • Choose an o-ring material resistant to both operating and friction-generated heat.
  • Verify compatibility of o-ring material and system chemicals.
  • Reduce squeeze if possible.
  • Inspect o-rings for quality prior to installation.
  • Use a higher temperature-rated material.

2. Weather or Ozone Cracking

Problem Source:

  • Ozone breaking down polymer chains.
  • Higher concentrations around electronics. Also, in atmospheric air. 

Possible Solution:

  • Employ o-ring elastomers that are resistant to ozone attack

3. Installation Damage

Problem Sources:

  • Sharp edges on mating components of the o-ring gland.
  • Sharp threads over which the o-ring must pass during assembly.
  • Insufficient lead-in chamfer.
  • Oversized o-ring ID on the piston.
  • Undersized o-ring ID on the rod.
  • Twisting or pinching of the o-ring during installation.
  • Lack of lubrication during installation.

Suggested Solutions:

  • Break all sharp edges.
  • Cover threads with tubes or tape during o-ring installation.
  • Provide a 15-20° lead-in chamfer.
  • Use lubrication during the installation process.
  • Ensure correct sizing of o-rings.

4. Incorrect O-Ring Size

Suggested Solution:

  • Ensure that o-rings have the correct dimensions to prevent incomplete seals. You can use tools like Apple Rubber’s O-Ring Gland Calculator or consult their engineering department to simplify the process of finding and ordering the exact o-rings you need.

5. Chemical Exposure

Problem Source:

  • Exposure to harsh chemicals and solvents that can degrade the o-ring material over time.

Possible Solutions:

  • Select o-ring materials that are compatible with the chemicals and fluids in the system.
  • Consider using chemically resistant elastomers like Viton for applications involving aggressive chemicals.
  • Implement regular inspections and replacements when necessary to prevent degradation over time.

6. Excessive Temperature Variations

Problem Source:

  • Rapid and extreme temperature fluctuations can cause o-rings to expand and contract, leading to material fatigue and reduced sealing effectiveness.
  • High temperature can cause plasticizers to come out and additional cross linking which will make the rubber harder and more brittle. 
  • Low temperatures pass glass transitions of the rubber can cause excessive compression set. 

Possible Solutions:

  • Choose o-ring materials with a wide temperature range suitable for the application.
  • Implement temperature controls or insulation to minimize rapid temperature changes in the system.
  • Use backup rings or additional support components to reduce the stress on o-rings in high-temperature variations.

Preventing o-ring failures is essential to maintain the integrity of seals in various applications. Proper material selection, installation procedures, and quality control are key to ensuring o-rings perform as intended.