The car’s O-rings are damaged for several reasons. This short guide provides details of some of the most common damage methods (there are others, but this article does not cover them).
Visual indications: The contact faces of the o-ring have a scratched surface, and where the wear was greater, there were deeper tears and even ruptures.
Causes: Often found in dynamic applications, abrasion occurs under conditions of repeated contact between the surface of the o-ring and the housing, leading to excessive friction between the two. Improper lubrication or improper finishing of the metal surface can exacerbate the risk, as they can allow abrasive contaminants to infiltrate the sealing system.
Solution: Ensuring proper lubrication of the sealing system is important. Infiltration of contaminants can be reduced by using scrapers.
The chemical attack
Visual indications: Depending on the chemical to be sealed, the o-ring may show some signs, including blisters, cracks, a change in hardness, or discoloration.
Causes: Some chemicals can react with certain elastomers. This often leads to increased reticular density, resulting in a hard, brittle material with a reduced ability to provide a reaction force. And the breaking of the polymer chain is possible, leading to a decrease in strength. Sometimes the reticular density may decrease, resulting in a softer and stickier material, which leads to loss of initial shape and integrity.
Solution: Choosing the right elastomer material is vital to ensure that the gasket is compatible with the application environment. The chemical attack is accelerated at high temperatures and when the elastomeric gaskets are subjected to stress due to excessive stretching or compression and mechanical conditions. Check the thermal compatibility of the main types of elastomers using our online guide.
Visual indications: The o-ring seems larger than its initial dimensions. This appears to occur along with the entire gasket or in certain places that have been subjected to the chemical environment.
Causes: The chemical medium’s penetration causes swelling into the elastomer due to the chemical similarity between the compound and the medium. The increased volume of the gasket can lead to gasket filling, extrusion, and loss of tightness. Chemical swelling can also lead to loss of physical properties, such as breaking strength.
Solutions: Use an elastomeric sealing material with proven resistance to the chemical environment. Check the chemical compatibility of the main types of elastomers.
Modification by compression
Visual indications: The cross-section of the o-ring becomes less circular, with flattened surfaces, taking the channel’s shape or gasket. The O-ring has taken a permanent shape, meaning it cannot return to its original shape after removing the deforming factor. This is quantified as a percentage loss in compression compared to the initial compression applied.
Solution: Selecting elastomers with low compression change and/or high-temperature efficiency will help extend the gasket’s life. The gasket pattern should be checked to ensure that the o-ring is not overcompressed. Cold modification can be reduced using a more flexible polymeric structure reflected in a lower glass transition temperature.
Extrusion and pinching
Visual indications: The edges of the low-pressure ring have a pinched, chipped, or lacy appearance. A leveling can occur in extreme cases where the surface of the ring seems to be peeled.
Causes: High stresses, usually the result of high pressure forcing the material into intersections, lead to extrusion. High-pressure pulses can cause the gaps between the contact surfaces to close and open. This can cause the ring to be caught between the edges of the contact surfaces, leading to physical damage to the gasket’s surface, often called pinching.
Solution: A harder material can help and the use of safety devices that can reduce gaps.