Ashton Seals are delighted to be able supply Astra Seals®. Created by an Aerospace Engineer to combat the harsh environments associated with liquid oxygen and the problems associated in sealing other cold media, such as liquid nitrogen and hydrogen, the Astra Seal® copes perfectly with the extreme low temperatures which make most O-Rings brittle, which in turn leads to failure.
Comprising 302 stainless flat wound ribbon springs encapsulated in either a FEP or PFA Teflon™ jacket to form an O-Ring, Astra Seals® span a temperature range from -250˚C to +260˚C (-420F to +500F).
Astra Seals® have been successfully used in several space shuttle/rocket launches and a multitude of other demanding applications by organisations such as Boeing, NASA and Lockheed.
The Ashtons team has experience of working with businesses across a
diverse range of industries which use cryogenic processes as part of their
operation. These include:
- Aerospace and defence
- Chemical processing
- Energy and power
- Food and beverage
- Pharmaceutical applications
In these types of operations, a cryogenic gasket will be necessary in
order to ensure that safe and reliable performance is achieved.
Why are specialist cryogenic seals necessary?
There are a number of reasons to choose a specialist seal over a standard
seal in these types of low temperature operations. These include:
- Protection of dangerous cryogenic fluids: Depending on the type being used, cryogenic liquids can burn, can
cause asphyxiation and can be toxic. Some materials can be a risk of fire
and explosion too, which makes suitable protection and containment an
absolute necessity.
- Conventional O-Rings may fail: In many cases, the working temperature of the application will be
too low for standard O-Rings to function properly. Very cold temperatures
can lead to some elastomers reaching a glass transition state (Tg), which
causes it to become less flexible and more brittle, risking failure.
- Contraction needs to be accounted for: Expansion and contraction which occurs naturally as temperatures
change can cause O-Rings to become unseated, risking cracking, leaks and
failure occurring.
- Cold set must be avoided: In applications where cryogenic operations work alongside higher
temperature operations, the risk of stresses on the O-Ring being unable to
relax at low temperatures is high when the wrong type of seal is used.
Known as ‘cold set’, this will create an unviable seal, leading to leakage
and failure.
In cryogenic operations, the right choice of seal is crucial. The choice
will depend on the operating temperature. For example, neoprene and nitrile may
fail at temperatures below -40°C, and silicone and fluorosilicone by -100°C.
Cryogenic operations are much lower even than this, so for operations working
at extreme low temperatures, speak to our Technical Department on 01226 273700.