BOTTOM COLD INSULATING LAYER IMPROVEMENT METHOD OF DOUBLE-SHELL CRYOGENIC TANK

摘要

PURPOSE:To make a cold insulant preservable without using any special storage vessel at the time of improvement by separating an inner tank bottom plate from a side plate of an inner tank, lifting it up to the specified height and tacking it temporarily, while making this bottom plate composable as a vessel for storing the cold insulant. CONSTITUTION:When a bottom cold insulating layer in a double-shell cryostat is improved, first of all, two manholes 16, 17 are opened, while an inner tank bottom plate 8 is separated from a side plate 11 forming a barrel part 9 of an inner tank 4. Next, the bottom plate 8 is slung up to the specified height position, and then a re-infrocer attached to the bottom plate 8 and the side plate 11 are welded and the bottom plate 8 is tacked temporarily. With this, a space S for improvement of the bottom cold insulating layer 4 is secured in the inner tank 4, while a vessel V for storing the cold insulant is partitioned off on the bottom plate 8. Then, the cold insulant 21 such as pearlite or the like of a side part cold insulating layer 15 is pumped up and, after being transferred onto the vessel V, a bottom part of the tank is cut off, forming a working port 22, thus improvement for the bottom part cold insulating layer 14 is performed.