Unfortunately, there are occasions where O-rings, in particular, fail.
The failure of these seals is not simply due to one factor, but various factors that can occur across a range of applications – hence why locating the exact cause of such problems is just that, a problem.
Some of the most common areas when investigating seal failure covers hardware failure, installation of the seal, temperature exposure and fluctuations, pressure analysis, how long the seal has been within the application itself, and more.
The answers to these fundamental questions, allow for a bigger picture to be obtained, identifying key facts, and eliminating certain areas as you work through your analysis.
In this post, we look at the most common types of O-ring failures, as well as O-ring replacements and some key troubleshooting solutions.
Types of failures and their solution
Abrasion
Abrasions are tears and cracks in the O-ring, which ultimately makes the sealing defective.
Abrasion typically occurs in dynamic applications, where there is repetitive contact between the O-ring and the housing.
Poor lubrication can also add to this wear and tear, increasing the risks of cracks and breaks.
To help, ensure you use the correct lubrication for the sealing system you have in place.
Also, opting for the correct surface finish can help eliminate the risk of abrasion, as well as certain contaminants being reduced through the use of scraper or wiper rings.
Failure with compression sets
When working with elastomer seals, it is often found that the compression set will be the most common cause of failure, i.e., the seal can no longer return to its original state.
The leading causes of compression set failure include:
- Fluid incompatibility
- Poor makeup of the material
- Temperature exposure is above given range
- Improper gland
The solution is to choose low compression set elastomer materials, as well as those providing higher temperature capabilities.
You should also check that over-compression is not occurring.
Installation Damage
Unfortunately, O-rings can become damaged during installation, where cutting and notching has occurred and is apparent on the seals surface.
Using dirty or poorly lubricated seals, incorrect sizes, or twisted O-rings can also all result in a bad “fit.”
These, among many other reasons, is why installation should be carried out with care. Preventing cuts and scratches to the surface can be done by covering sharp edges, ensuring the right lubrication, and that the hardware has suitable lead-in chamfer aids.
Failure with extrusion
This relates to the pressure load that the seal is exposed to, causing the O-ring to have a chipped appearance. Shaving also occurs where the surface of the O-ring has peeled off (however, this is only found in the most severe cases).
When the O-ring is exposed to high pressure and high stresses, it forces the material into a gap, known as the clearance gap, creating the process that is known as extrusion.
Gland overfill is another common example of extrusion – when the O-ring begins to deform from compression of the seal, and it fills the entire gap/area, receding over into what is known as the extrusion gap.
In these instances, face seals will perform better than radial seals; however, if you are using radial seals, you can omit the clearance gap altogether by installing backup rings where necessary.
Spiral failure
Spiral failures are mostly found in dynamic reciprocating O-ring appliances. Spiral failure is also known to occur during installation.
The good news is, spiral failure, unlike others, is easy to identify. However, there will still be an underlying root cause for this failure, and it is this root cause that can prove hard to find.
Reasons for spiral failure can include:
- Poor lubrication
- Friction
- Eccentric components
- Uneven finish to surfaces
- Sideloading
- Installation errors
- And more.
In these instances, we’d recommend a harder O-ring material to be used. You could even consider different seal profiles, such as quad rings and D-seals.
T-seals, however, provide the most robust solution, and they can fit existing O-ring grooves with ease.
At Specialist Sealing Products (SSP), we can help.
We provide a vast range of seals and gaskets, from a wide range of materials, helping us to find the perfect solution for you and your application, always.
Call us today on 01535 274 776 and see how we can help you.
Read the next article: O Ring Replacement
