ASTRA SEALS®

 

Ashton Seals are delighted to supply Astra Seals® through our supplier relationship.

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.