What is an O-ring and what is it used for?
O-rings are all around us, and you’ve probably come across thousands in your lifetime without even realising. From beer to scuba gear, these little doughnut shaped parts are not particularly memorable, but infinitely useful. But what exactly is an O-ring, what’s it used for, and why are they so popular? Let’s find out.
What is an O-ring?
An O-ring (otherwise named a packing or a toric joint) is a mechanical gasket in the shape of a torus (a donut shape). The function of an O-ring is to seal the join of two pieces to ensure that no gas, air or liquid could pass through.
Why are O-rings used?
In very simple terms, an O-ring seal sits in a groove or channel between two surfaces that are going to be mated or pushed together. The O-ring connects these two parts, and becomes compressed in order to form a tight but dynamic seal.
What are O-rings used for?
O-rings are usually found in static and dynamic applications including pumps, connectors, cylinders and valves.They are an incredibly versatile solution to engineering applications.
For example, the valve stems in car engines usually use O-rings to stop oil from entering the combustion chamber. The O-ring creates an air and liquid tight joint between the valve stem and the valve guide. Without this, oil would leak into the valve guide and engine causing wastage and environmental damage.
What are O-rings made from?
Most O-rings are made from elastomers, of which there is a huge range, each having different strengths and weaknesses.
The material of the O-ring will be determined by what the O-ring is designed to do:
High and low temperatures:
Some Silicone and fluorosilicone are able to handle temperatures as cold as -100°C. and for very high temperatures, FFKM works at up to 316°C.
O-rings can be designed to be resistant to many chemicals at high and low temperatures.
Hot water and steam:
Ethylene propylene O-rings (EPDM) are designed to be resistant to steam and hot water, as well as alcohol, strong alkalis and fluids found in automotive applications and used primarily in engines and moving parts.
Grease and hydraulic fluids:
Buna-N O-rings (Nitrile) are used when there are greases and oils present.
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