Doubts regarding the repair approach for the bottom ring plate of large storage tanks based on API653

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Dear teachers: For large storage tanks with a capacity of several thousand cubic meters, the areas subject to severe corrosion are mostly found along the lower edge of the wall plates in the bottom ring. For instance, if the entire area within 300 mm above the bottom plate is severely corroded, referring to Chapter 9 of API653 on the repair and replacement of storage tanks, the standards only provide guidelines for local repairs; they do not address situations involving such extensive damage. There are no instructions regarding methods such as 1) cutting out and replacing the entire section, 2) applying patch plates around the entire area, or 3) using a diagonal support skirt structure extending 300 mm upward – where the distance between the bottom of this support and the outer edge of the edge plate does not meet the minimum requirement of 50 mm. In cases where the strength can be ensured through calculations, but no suitable support point is specified in the standards, the mechanical calculations can still be satisfactory. Also, with the methods for points 2 and 3, corrosion protection on the inner side is a major issue. Due to corrosion in the lower part, the entire tank has to be discarded, which is too costly economically; I would like to hear everyone’s opinions on this