You’ve probably come across numerous o-rings in your lifetime, whether you knew it or not. From cars to cameras, these little doughnut shaped parts are instantly forgettable but endlessly useful. They are probably one of the biggest revolutions in mechanical engineering to date, allowing us to develop new machinery, better products and safer working environments. So, what are o rings used for, and why are they so popular? Let’s find out.
Why are o rings used?
O rings have some amazing properties which makes them a crucial component of many precision-engineered devices. Their natural propensity to return to their original shape when the cross-section has pressure exerted on it means they are one of the most economical and reliable methods of making a strong seal possible.
The other reason o rings are so commonly used is down to the wide range of materials they can be made from. The majority of o rings are made from elastomers, which are a type of elastic polymer, but there are a huge variety of these elastomers available, each with different strengths, weaknesses and tolerances. The application that the o ring is destined for will determine which type of material is most suitable, for example:
High and low temperatures: Silicone and fluorosilicone can cope with temperatures as low as -100°C. Cryogenic operations will require a seal that can cope with low temperatures such as the NES Astra Seal®. For very high temperatures, FFKM works at up to 316°C
Chemical compatibility: Viton™, also known as FKM/FPM, o rings are resistant to many chemicals and work at high temperatures too
Hot water and steam: Ethylene propylene o rings (EPDM) are resistant to steam and hot water, as well as to alcohol, strong alkalis and fluids found in automotive applications
Grease and hydraulic fluids: Buna-N o rings, also known as nitrile o rings, are best to use where there is a lot of grease or hydraulic fluid around
As you can see, for pretty much any application you can think of, there will be an o ring which can handle that environment. This means they are useful in a huge range of applications, from appliances found around the home to gigantic machines used in manufacturing and even in the space shuttle!