When two or more tanks are installed concurrently in the same location for the same purchase :-

spot radiographs to be taken is based on each tanks footage of the welds;

spot radiographs may be omitted in tank # 2 if no defects were found in tank # 1;

spot radiographs may be taken based on the aggregate footage of the welds of the same type and thickness;

spot radiographs to be taken be based on the aggregate footage of the welds regardless of weld type and thicknesss;