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Condensation

Von Kryoleitung abtropfendes Kondensationswasser
Seeping condensation water
Preventive measures:
  • Only use dewars with separated exhaust and safety valve lines.
  • Do not leave dewars open to atmosphere.
  • Equip exhaust lines to atmosphere with nonreturn valves.
  • Perform a leaktest before evacuating cryogen baths with emphasis on leaks by which air might be sucked into the cold part of the apparatus.
Unwanted condensation or freezing can also lead to:
In some cryogenic processes e.g. in cryopumps and in cryotraps condensation of gases is used purposeful. However, if uncontrolled condensation takes places, it may present a danger. The most imminent danger caused by condensation is the:
Freeze-up of exhaust pipes

of dewars by air and/or air moisture. The plugging causes a pressure build-up which may lead to the bursting of the dewar.
Die unerwünschte Kondensation oder unerwünschtes Einfrieren kann auch folgende Auswirkungen haben:
 
Mechanical damage
  • by ice accretion on valves, turbines etc.,
  • by dripping condensate at cryogenic temperatures or
  • by water condensate
Pressure build-up by desorption
See previous page.
 
Formation of explosive mixtures
  • Condensation of air or oxygen on combustible liquids or materials can create from flammable up to explosive mixtures. One example is the condensation of air or oxygen
  • in the insulation material of transferlines,
  • within a liquid hydrogen tank or
  • on the active charcoal of a cryogenic adsorber [15].
Important! - Air condensate is a strong promoter of combustion as it can have an oxygen concentration of up to 50%. This is due to the higher boiling point of oxygen.
 
 
Preventive measures against condensation and its consequences
  • Purge and evacuate all equipment thoroughly before operation.
  • Operate installations at slight overpressure in order to avoid impurities from entering through leaks.
  • Wherever possible - do use vacuum insulation.

Otherways - do use incombustible insulation material and use vapour locks