[Engineering][Knowledge]Requirement for bottom & annular plate welding seam distance

As per para.5.1.5.4.2 of API 650(12th ed),

5.1.5.4    Lap-Welded Bottom Joints
5.1.5.4.2    Three-plate laps in tank bottoms shall be at least 300 mm (12 in.) from each other, from the tank shell, and from joints between annular plates and the bottom. A three-plate lap is created where three plates come together and all plates are joined to one another by lap welds. A location where a pair of bottom plates are lap-welded to each other and are lapped onto an annular plate constitutes a three-plate lap, but lapping a single bottom plate onto a butt-welded annular plate splice does not constitute a three-plate lap weld since the two annular plates are not joined together by a lap weld. These lap joint connections to the butt-weld annular plate are illustrated in Figure 5.3d.



But, in case of weld seam between shell and annular plate, Minimum distance shall be kept as 300 mm.