| 摘要 |
PROBLEM TO BE SOLVED: To easily and economically prevent corrosion in the back face of a bottom plate by filling the gap part between a foundation part to be mounted with the bottom plate of a flat bottom tank and supporting it and the back face of the bottom plate with an inert gas from a gas feed tube while air is exhausted from plural gas exhaust tubes and holding it to a sealed state. SOLUTION: The peripheral part on the back side of the bottom plate 3 of an existing or new flat bottom tank is mounted with one or more gas feed tubes 31 and plural gas exhaust tubes 33 at suitable intervals. The gas feed tube 31 is connected to an inert gas feeding source 32 by a rubber hose 37, a stop valve 34 is opened to feed an inert gas such as dry nitrogen or the like, and, moreover, a stop valve 36 of the exhaust tubes 33 is opened to exhaust air at the inside. At the time when the inert gas is sufficiently substituted for the exhausted air, the stop valves 34 and 36 are closed. In this way, the gap part between at least the vicinity part of the back face of the bottom plate in the foundation part where the bottom place of the flat bottom tank is placed and supported and the back face of the bottom plate is filled with the inert gas, and it is held to a sealed state.
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