DEVICE FOR INERTING A LIQUEFIED GAS STORAGE TANK FOR A SHIP FOR TRANSPORTING THIS GAS

A device for inerting a liquefied gas storage tank for a ship for transporting this gas, comprising: - a liquefied gas storage tank (1) insulated by a primary insulation space forming an inner casing around the tank, and a secondary insulation space forming an outer casing around the tank, each of the spaces comprising an insulator and being intended to be filled with an inert gas, said tank being arranged between two sealed partitions (2c) and above a tank bottom (2a), - a drainage box (20) situated under the tank, this box being linked to a passage (22) extending between the tank bottom and the outer casing such that fluids can flow by force of gravity from the tank bottom to the drainage box, - means for supplying nitrogen to the primary and secondary spaces, and/or for discharging nitrogen from these spaces, characterised in that said drainage box is in fluidic communication with said passage and said secondary space, and in that said means for supplying and/or discharging from said secondary space comprise a nitrogen line (30) that is connected to said drainage box such that the nitrogen supplying this space and/or discharged from this space flows through the drainage box.