Method for checking the leakproofness of a leakproof and thermally insulating tank for storing a fluid

A floating or onshore storage installation for a liquefied gas at a temperature at which the gas is liquified comprising:

• a tank at the temperature at which the gas is liquified comprising a carrier structure which has an inner hull and an outer hull, the space between the inner hull and the outer hull being referred to as the confined space, a primary sealing membrane which is intended to be in contact with the liquefied gas at the temperature at which the gas is liquified contained in the tank, and a secondary sealing membrane which is arranged between the primary sealing membrane and the inner hull, the space between the primary sealing membrane and the secondary sealing membrane is referred to as the primary space and the space between the secondary sealing membrane and the inner hull is referred to as the secondary space, the primary space and the secondary space comprising insulating materials, the primary space comprising a primary gas inlet and a primary gas outlet, the secondary space comprising a secondary gas inlet and a secondary gas outlet, the primary sealing membrane resting directly on the insulating materials contained in the primary space and the secondary sealing membrane resting directly on the insulating materials contained in the secondary space,
• an inert gas reservoir which is arranged in order to inject the inert gas into the primary space,
• an injection device for injecting the inert gas of the inert gas reservoir via the primary gas inlet, and thus placing the primary space under pressure relative to the secondary space,
• a suction device which is connected to the secondary gas outlet in order to generate a pressure lower than atmospheric pressure in the secondary space,
• a device for measuring the temperature of the outer surface of the inner hull,
• a system for displaying the temperature measurements in order to locate a sealing defect of the secondary sealing membrane in the form of a cold spot on the outer surface of the inner hull.