Ozone Rubber Deterioration
O Rings are amongst the most commonly used seals. They come in a wide selection of tough materials, serving a wide range of industries including Pharmaceutical, Food & Beverage, Chemical Processing, Petrochemical and many more. They provide a high-quality seal and reliability for many different fields and are adequate for the most exigent applications.
Due to O Rings being so popular, a lot of the time you may not even realise they are there until one starts to break and consequently leak. Ozone exposure is one of the reasons why this could happen. It is extremely important to be aware of how ozone damage occurs and what steps you should take to prevent it.
Why ozone causes O Ring cracks?
O Ring malfunction can be connected to a number of causes, however its primarily exposure to oxygen particles that leads to cracks in elastomer O Rings. Exposure to oxygen is unavoidable as it’s in the air we breathe. Generally, oxygen particles join up in pairs to form dioxygen. This makes up the vast majority of the oxygen in the atmosphere. Sometimes, however, oxygen particles form groups of three, this creates the ozone substance.
In the stratosphere, ozone is exceptionally valuable and shields us from harmful sun rays. From close range, however, it can cause health issues and even in smallest density can lead to elastomer O Ring cracking. Ozone density in the stratosphere is anywhere within two and eight parts per million (in the troposphere, concentrations are above 75 parts per billion).
Majority of elastomers are polymers which comprise of single units linked together in a long chain. In instance if the polymer chain develops a weak spot due to exposure to ozone, the elastomer O Ring can crack and consequently expand over time until the damage can be noticed by the naked eye.
Ozone cracking (ozonolysis) occurs primarily with O Rings made from Nitrile (NBR).
How to prevent ozone damage to O Rings?
For the purpose of preventing ozone damage, it is important to store and install O Rings appropriately.
In industrial applications, the main cause of O Ring cracking (ozonolysis) is exposure to:
- Ultraviolet light
- Electrical arcing
- Electromagnetic fields
Suggestions for storing O Rings
Firstly, inspect the storage area for any ozone generating equipment that could cause O Ring damage.
- Keep O Rings away from ultraviolet light – direct sunlight and fluorescent light bulbs
- Do not store O Rings within 6 feet (2 meters) of an electric motor or other potential source of electrical arcs
- Do not store O Rings in a stretched state – ozone damage will generally only occur to a stretched O Ring
(If O Rings must be stored in a stretched state, store them in an airtight bag until ready to use).
To view our Storage and Shelf Life of elastomers guide, click here.
Suggestions for installing O Rings
- Install O Rings into the mating part within 24 hours of installing the O Ring fitting
- When assembling, wet the O Rings with a grease to protect them from ozone
EPDM O Rings are used in numerous industries. This is due to the EPDM’s remarkable resistance to UV and ozone, steam and oxygenated solvents.
If you would like further information about how to correctly install a seal, view our Guide to Seal Installation.
To see what other factors cause O Ring failure, view our O Ring Failure Guide.
E & OE.