With so many different o rings available and in a range of chemical compound materials to suit various applications and their environmental conditions, it’s important to understand that these differences will cause the o ring to operate differently in varying temperatures.
This means that not only must you take into account chemical compatibility and mechanical properties, but also how the seal performs at specific temperatures, particularly low temperatures.
In this post, we look at the best industrial O-rings suitable for low-temperature applications, along with their mechanical and chemical properties.
Low temperature o rings
You will often find that most o rings will fail at low temperatures as the rubber of the o ring loses its elasticity as the temperature lowers, making the compression set visibly reduced – the low temperature within the application hinders the o ring material from returning to its original size after compression.
When this reaction happens, it means you can no longer rely on the seal to provide a secure sealing solution.
This means it can be vital to know how much of the o ring material will fail to return to its original state after compression, as this will affect sealing performance.
When compression begins to fail, especially at low temperatures, this can lead to seal leakage and overall O-ring failure.
What are low temperature o rings?
Low temperature o rings are able to withstand temperature drops, not lose their elasticity, and maintain their compression set.
The lower the compression set, the better the seal’s resistance to dynamic and static pressure under which the seal is placed.
However, at very low temperatures, the seal material can harden, making it less likely to deform under pressure and leading to leaks.
The good news is that there are set tests which allow you to check the material’s performance at set temperatures, these include:
- Brittleness – can the o ring withstand breaking when bent at a certain temperature?
- Temperature retraction – can the material return to its original state?
- Compression set – what happens to the o ring when the material is exposed to low temperatures?
What is the best low temperature o ring?
Nitrile o rings – with an operable temperature range of -45 degrees Celsius to 120 degrees Celsius, nitrile is a low-cost o ring sealing solution that performs well at low temperatures and is both oil and chemical-resistant. However, it is important to note that nitrile o rings will shrink at extremely low temperatures and, because of this, will lose some chemical resistance.
HNBR o rings – able to operate between -50 degrees Celsius and 150, HNBR o rings have superior mechanical properties compared to NBR, helping to prevent extrusion and wear. However, HNBR o rings do lose some of their flexibility at low temperatures, and it is not a material that is recommended for use with hydrocarbons or strong acids.
Silicone o rings – with a temperature range suitable for -55 degrees Celsius up to 200 degrees, silicone o rings also come as fluorinated, with operating temperatures ranging from -60 to 230, and also compound o rings with a temperature range from -100 to 230. Silicone o ring types have a high level of resistance to low temperatures and can be prone to wear. However, silicone o rings can have little chemical compatibility; they have poor tear strength and wear resistance, often making them unsuitable for dynamic applications.
FFKM o rings – providing great all-round levels of resistance, FFKM o rings can operate at temperatures from -42 degrees Celsius to 220 degrees Celsius. FFKM also offers a high level of chemical resistance, making it a suitable sealant in petrochemical, food processing, and pharmaceutical applications. However, this is one of the most expensive o rings on the market.
PTFE o rings – offering incredibly low temperature and chemical resistance, PTFE o rings can operate under -200 to 250 degrees Celsius. Offering low-friction properties, this o-ring is tough and abrasion-resistant. However, due to its little to no compression set, it can dent easily.
FEP/PFA encapsulated o rings – able to handle temperatures ranging from -60 to 260 degrees Celsius. This type of o ring elastomer is suitable for a range of applications, as the material is used as a protective casing placed over standard o rings. FEP encapsulated seals are adaptable to a range of environmental demands.
Astra seals – these seals are among the best o-rings for low-temperature applications, as they don’t contain any rubber at all. This o-ring features 302 stainless steel ribbon with an FEP-encapsulated casing, an operating range of -250 degrees Celsius to 260 degrees Celsius, and maintains its compression set in all low-temperature applications. However, it should be noted that this type of seal is primarily suited to axial, non-stretch applications.
O ring suppliers UK
Many of the o rings we supply at SSP already support low-temperature applications; however, for anything lower than -25, you should consider NBR, HNBR, FEP encapsulated, and more.
Our team can help.
Answering your seal and gasket questions and putting your mind at ease that the seal you choose will perform to the highest standards, if you’re looking for O-ring suppliers Leeds, look no further.
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