Cryogenic seal

Cryogenic seals provide a mechanical containment mechanism for materials held at cryogenic temperatures, such as cryogenic fluids. Various techniques, including soldering and welding are available for creating seals; however, specialized materials and processes are necessary to hermetically entrap cryogenic constituents under vacuum-tight conditions. Most commonly used are liquid helium and liquid nitrogen, which boil at very low temperatures, below −153 °C (120 K), as well as hydrocarbons with low freezing points and refrigerating mixtures.[1][2] Pure indium wire or solder preform washers are accepted as the most reliable low temperature sealing materials. When correctly formed, indium will afford leak rates of less than 4.0x10 -9 mbar- liter/sec.[3] Alternative cryogenic seal materials include silicone grease conical seals, and Pb/Sn (lead-tin) wire seals.[4]

History

Fundamental cryogenic processing began in the 1940s, albeit primitive. Steel cutting tools were immersed in liquid nitrogen to enhance their service life.

Mechanical processes utilizing cryogenics were documented well in the 1950s and by the 1980s cryogenic fluids began to be considered for storage and use in modern devices.

Today, cryogenic seals are a necessity in high-tech commercial, medical, and military applications to encapsulate the cryogenic fluids critical for device resolution and function.[5]

Applications

Applications which utilize cryogenic seals include:[6]

Indium seals

Advantages

Advantages of indium cryogenic seals:

Disadvantages

Process information for indium seals

Reliability testing

Types

Manufacturers

External links

References

This article is issued from Wikipedia - version of the 2/16/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.