Why do O-rings fail?

There are a number of reasons why O-rings can fail. Understanding what risks are posed to your sealing components and how to identify and mitigate these is essential in quickly understanding possible failures and reducing downtime.

Elastomer sealing experts, Precision Polymer Engineering (PPE) explore five of the most common failure modes that their engineers come across

Abrasion

In cases of abrasion the O-ring may appear to have a grazed surface. With excessive wear there could be deep lacerations and breaking.

The cause is common in dynamic application where abrasion can results from excessive repeat rubbing and friction between the component surface and the housing.

The risk can be increased by improper lubrication, the surface finish of the metalwork surrounding the component and in some cases, when abrasive contaminants have compromised the seal.

In order to better avoid abrasion, the correct lubrication for the sealing system is important and materials with improved abrasion resistance.

Wiper and scraper rings can reduce the abrasive contaminants from damaging the seal.

Chemical Attack

Chemical attack can show as a number of signs including blisters, cracking, increased hardness, discolouration or change in consistency.

Unless the sealant has experienced a severe case of chemical attack, it may not be always be visibly identifiable and could require physical measurement.

If an elastomer material isn’t compatible with its environment, the chemical media can attack the rubber and change it’s cross-linking properties.

Additional cross links will cause it to become hard and brittle and less cross links will create a tacky and soft elastomer.

Correct elastomer material selection is vital to ensure your sealing components are compatible with application media. Elevated temperatures, excessive stretch and squeezing can speed up the process of chemical attack and can be best prevented with the use of elastomers with high temperature tolerance such as Perlast perfluorolastomers (FFKM).

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