Leaktight and thermally insulating vessel, and associated method for placing under vacuum

A method for evacuating an intermediate space in a sealed and thermally insulating tank (1, 111), wherein:

• the sealed and thermally insulating tank (1, 111) comprising an outer sealed wall (11, 110), an inner sealed wall (26,126) situated at a distance from an inner side of the outer sealed wall (11, 110) and defining an internal space (13) intended to contain the liquefied gas, and an intermediate space (30, 130) situated between the outer sealed wall (11, 110) and the inner sealed wall (26,126), the method comprising the steps of:
• replacing a gaseous phase present in the intermediate space (30, 130) with a replacement gaseous phase at a first temperature, the first temperature being greater than 273 K, the replacement gaseous phase being composed of one or more main chemical species, and one or more residual chemical species, the replacement of the gaseous phase comprising the step of injecting the replacement gaseous phase into the intermediate space (30, 130) at a first pressure, the first pressure in the intermediate space being less than 500 kPa absolute, in which the or each main chemical species is in the gaseous state at the first temperature and at a partial pressure lower than the first pressure, in which the or each main chemical species exhibits a saturating vapour pressure at any temperature lower than 126 K lower than the saturating vapour pressure of nitrogen at said temperature lower than 126 K, the temperature of the internal space (13) being greater than 273 K, then
• lowering the pressure in the intermediate space (30, 130) to an absolute pressure lower than a pressure threshold, and
• cooling the sealed and thermally insulating tank (1, 111) by injecting a fluid at a second temperature lower than 273K into the internal space (13) of the sealed and thermally insulating tank (1, 111),
• wherein the pressure threshold is lower than the triple point of said or each main chemical species, to make said or each main chemical species condense into solid phase upon the cooling of the sealed and thermally insulating tank (1, 111), and
• wherein the or each residual chemical species is at a partial pressure lower than 0.1 kPa.