Introduction
O-ring failure can have expensive and severe consequences. If you want to ensure optimal performance of your design under all possible circumstances, it is important that you acquaint yourself with the most common reasons for O-ring failure.
Common Failures
Abrasion
Abrasion is an O-ring failure that is common in dynamic applications. This is due to repetitive contact and, ultimately, friction between the O-ring surface and housing groove. There are mainly two reasons for abrasion, namely insufficient lubrication and an improper surface finish. Abrasion can be detected by looking at the sliding contact faces of the O-ring. If it has a grazed surface, you may be running the risk of abrasion.
Chemical Attack
If the O-ring’s main elastomer is incompatible with the application media, the O-ring may fail due to a chemical attack. Chemical attacks can be worsened by extreme temperatures and if the O-ring is under stress. A chemical attack on the O-ring can be detected by looking for blisters, cracking, and discolouration on the in the O-ring.
Chemical Swell
When the O-ring’s elastomer allows ingress of chemical media, the O-ring can swell and lose its sealing ability. It can also lose its tensile strength. Like a chemical attack, this failure is due to lacking compatibility with the chemical media. Monitor the size of the O-ring and compare its current size to its original size to determine if there is chemical swelling.
Compression Set
This is when the circular cross-section of the O-ring becomes less circular and flattened on the sides to increase in temperature. If the O-ring’s elastomer is not compatible with extreme fluctuations in temperature, it can diminish the O-ring’s sealing ability as it doesn’t revert to its original shape when the temperature goes back to normal.
Installation Damage
O-rings that are damaged to careless or improper installation can result in failure. Incorrect sizing, cuts on the surface of the elastomer, dirt, or twisted O-ring, can result in lacking sealing ability. Installation damage can be caused in many different ways, and it can also happen if the O-ring is the correct size for the design.
Solution
There is no one solution for common O-ring failures. Failure may be due to many different circumstances and conditions. There are, however, overlapping causes of O-ring shortcomings that one should take note of.
Incompatibility with chemical media can cause an entire array of common-ring failures. If the material or elastomer of the O-ring is not compatible with the chemical media, it can reduce the O-ring’s sealing integrity. The chemical media or operating fluid may also ingress into the elastomer. To prevent this, make sure that chemical media and elastomer are compatible with each other.
The O-ring’s ability to cope with extreme temperatures is also important to prevent a number of common O-ring failures. If the sealing properties of an O-ring’s elastomer change under different temperatures are can also lead to failure. This is especially important when it comes to aircraft or vehicles that travel or flies in extreme circumstances.
