Answer:
This issue was logged under TFS-D73031, Opening under external pressure on Heat Exchanger in ASME VIII div.2: wrong calculation of allowable hoop compressive membrane stress of a cylinder.
This issue has been fixed in the AutoPIPE Vessel Maintenance Release 2 (v33.02.01.08) or higher. Please confirm / update your version of AutoPIPE Vessel to v 33.02.01.08 or higher.