Patch plates cannot be used in the critical zone if the tank operating temperature exceeds 200 F for carbon steel or 100 F for stainless steel. See Addendum 3 for additional requirements and limitations. Requirements were added that define the required offset of vertical shell joints. Several changes were made in weld inspection requirements. Bottom plate weld inspection requirements have been clarified.
Inspection is specified for patch plates located within the critical zone.
Some hydrotest requirements were modified. The section providing criteria for when a hydrotest can be waived has been completely revised and expanded. Significant changes were made in Appendix B covering tank settlement. A basis is also provided for using finite element analysis for settlement evaluation. The section on edge settlement evaluation was also completely rewritten and additional details provided.