The principle of water vapour condensing on a cold water mains pipe, is taken further by using liquid nitrogen to reduce the temperature to -196ºC (77K) where it is possible to condense gases and vapours that have a melting point above that.

The process of condensation bonds the gas or vapour to the cold surface thereby removing the gas or vapour from the mainstream gas, which must have a lower melting point.

The formation of condensate on a cold surface will remain located so long as the temperature remains below the temperature of the bonded gas or vapour. As large formations of condensate will reduce the effectiveness of the trap, it is therefore not recommended where there are large quantities of condensable gas or vapour.

Additionally, the cryogenic trap requires maintenance as the liquid nitrogen boils off, as any wide level of variation will cause some condensed matter to evaporate and return to the mainstream gas. Where there is a requirement for extended periods of use, it is recommended that a controlling device should maintain the liquid nitrogen level.

Glove Box Technology Ltd has design solutions for portable and integrated cryogenic traps.

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