Changes to API 650, Eleventh Edition
Welded Steel Tanks for Oil Storage

By Vincent A. Carucci

Two addenda have been issued for the Eleventh Edition of API 650 since it was published in June 2007. Addendum 1 was issued November 2008, and Addendum 2 was issued November 2009. The following highlights several of the changes that were made and is not all inclusive. Refer to API 650 for complete information.

Section 1: Scope

Section 2: References

The following additional references have been added:

Section 4: Materials

Section 5: Design

Section 10: Marking

Specific markings are now identified to be used depending on where thermal stress relief has been done.

Appendix AL: Aluminum Storage Tanks

A new Appendix AL has been added covering material, design, fabrication, erection and testing requirements for tanks constructed of aluminum and aluminum alloys.

Appendix B: Recommendations for Tank Foundations

A Para. B.6 has been added that identifies foundation considerations for tanks operating at elevated temperatures [ > 200°F (93°C)].

Appendix E: Seismic Design of Storage Tanks

Several of the formulas contained in this Appendix have been changed. Among them are those contained in Paras. E.4.5.1, E.4.6.1, E.4.6.2, E.6.1.4, E.6.2.1.1, and E.7.2.

Appendix EC: Commentary on Appendix E

This new appendix provides background information on the development of the requirements contained in Appendix E. It also includes several example problems that illustrate the application of the requirements.

Appendix F: Design of Tanks for Small Internal Pressures

Appendix G: Structurally Supported Aluminum Dome Roofs

Appendix H: Internal Floating Roofs

Appendix K: Sample Applications of Variable Design Point Method

There is now a second example that provides complete calculations for both the design and hydrotest calculations.

Appendix P: Allowable External Loads on Tank Shell Openings

Para. P.3 that provided an alternative procedure for evaluating external loads considering WRC Bulletin 297 was completely deleted.

Appendix S: Austenitic Stainless Steel Storage Tanks

Appendix SC: Stainless and Carbon Steel Mixed Materials Storage Tanks

This new appendix covers materials, design, fabrication, erection, and testing requirements for tanks constructed with stainless steel and carbon steel.

Appendix V: Design of Storage Tanks for External Pressure

Appendix X: Duplex Stainless Steel Storage Tanks

A new appendix has been added to cover materials, design, fabrication, erection, and testing requirements for tanks constructed of duplex stainless steels.

Appendix Y: API Monogram

A new appendix provides information on use of the API Monogram.