Apparatus and method for evacuating an insulated cryogenic hose

Abstract

A flexible cryogenic hose is comprised of an inner cryogenic tube surrounded by a concentric heat shield, a closed concentric chamber and an outer protective jacket. At normal ambient temperatures the chamber is completely filled with carbon dioxide gas. As cryogenic liquid is pumped through the inner cryogenic tube, heat is transferred from all structures within the hose, including in particular the carbon dioxide gas in the closed chamber, which runs the length of the cryogenic tube. As the carbon dioxide gas is cooled, it liquefies, thereby substantially evacuating the chamber. The chamber has sufficient structural rigidity to avoid collapse at normal atmospheric pressures. After the cryogenic hose is used, cryogenic flow ceases and the hose warms. In warming, carbon dioxide gas in the chamber gassifies and again refills the chamber. As a result, outgassing from flexible or plastic material from which the hose is made into the chamber, while it is evacuated, is substantially avoided even after repeated cycles of use. Materials particularly adapted for use in flexible hoses, which are normally unsuitable because of their outgassing characteristics for use in vacuum insulated hoses, now become satisfactory materials for use.