O-rings are one of the most common seals used in equipment design because they are reliable and have simple mounting requirement. While these type of seals are often inexpensive, their failure can lead to significant amount of loss in production, downtime and maintenance costs.
Therefore, it is important to look out for early warning signs and understand the various types of common O-Ring failure to prevent any unwanted damage or cost during critical operation.
Here are 5 of the most common reasons why O-Ring fails, the type of typical damage and the recommended corrective actions:
O-Ring surface peeled off or nibbled off at the opposite
side of pressure, often only on part the circumference.
- Material overflow on one side, also temporary
- High/pulsating pressure (Hardware expands or contracts)
- Sharp groove edges
- Radial clearance is too large
Examples of Extrusion
- Back-up rings
- Different seal profile
- Decrease clearance
- High-modulus/hardness elastomer
- Proper gland design
O-Ring surface nibbled off
Spiral marks or tears in the O-Ring surface.
- Irregular rolling/sliding of the O-Ring because of
- High surface roughness due to missing or wrong lubricant
- Out-of-round hardware
- Mounting error
Examples of Twisting/Spiraling
- Careful installation
- Other seal profile
- Change hardware or working conditions
Spiral marks on O-Ring surface
3. Permanent Distortion
Distorted O-Ring, usually flattened on one side or both sides.
- Inadequate material quality
- Insufficient state of curing
- Contact with incompatible media/thermal overload
- Wrong groove lay-out
Example of Permanent Distortion
- Correct material selection (medium, compression set)
- Right groove lay-out
- Reduction of working temperature
(Left) Obvious flattened O-Ring on both sides, axial, material thermal overcharged
(Right) O-Ring with cracks
4. Ozone Cracking
Cracks vertical to the direction of tension (stretched O-Rings)
and shows signs of premature ageing.
- Stretching, time and temperature
- High ozone concentration
Examples of Ozone Cracking
- Select ozone resistant materials
- Change of storage conditions
Flattening on one side of the O-Ring cross section and the area
of abrasion is smooth and shiny with loose particles.
- Wrong surface roughness
- Abrasive media
- Insufficient lubrication
- High, pulsating pressure with static use
- Dynamic motion
- Poor elastomer surface finish
Examples of Abrasion
- Improve surface roughness
- Reduced squeeze or friction
- Avoid system contamination
- Consider internally lubed elastomers
- Eliminate abrasive components
Abrasion area appears to be smooth and shiny
Interested in knowing more about O-Rings?