Changes in API 650, Welded Steel Tanks for Oil Storage

By Vincent A. Carucci and Stephen J. Gliebe

The following highlights several changes to API 650 that are contained in the Eleventh Edition dated June 2007. It should be noted that the addition of Reference Section 2 and Definition Section 3 resulted in changes to paragraph numbers for all the subsequent sections.

Section 1: Scope

Section 2: References

References have been moved to Section 2, and several new reference standards have been added. Among them are three Process Industry Practices (i.e., PIP) and several from the US EPA and OSHA.

Section 3: Definitions

A new Section 3 with definitions has been added.

Section 4: Materials

Section 5: Design

Section 6: Fabrication

Section 7: Erection

Section 8: Inspection

The criteria for determining the number of spot radiographs required on a tank have been changed. The new criteria are based on a per tank basis, rather than the prior practice which allowed selection based on a group of tanks (Para. 8.1.2.4).

Appendix A: Optional Design Basis for Small Tanks

Conformance to toughness requirements has been expanded to include bottom reinforcing plates in flush-type connections and flush-type shell connections, and flush-type fitting necks attached to the shell (Para. A.2.4).

Appendix C: External Floating Roofs

There are changes to most of the paragraphs in Appendix C for external floating roofs. A complete review is recommended. Some of the changes to the design section are highlighted below.