Changes Contained in Addendum 2 of API 653, Tank Inspection, Repair,
Alteration and Reconstruction
By Vincent A. Carucci
This article highlights several of the changes to the Third Edition of
API 653 that are contained in Addendum 2 dated November 2005.
- Para. 1.1.1. The introduction was changed to delete the reference
to carbon and low alloy steel tanks. It now just references tanks that
were built to either API 650 or 12C, which was always its intent.
Deleting the explicit material reference now makes it clear that it is
intended to also apply API 653 to stainless steel tanks since API 650
now covers stainless steel tanks.
- Para. 3.1. Simplified the definition of “alteration” to “any work
that changes physical dimensions or configuration.”
- Paras. 3.21 through 3.25. Added definitions for as-built standard,
current applicable standard, major alteration or major repair,
recognized toughness, and unknown toughness.
- Para. 220.127.116.11. Added an explicit reference to API RP 579 as an
acceptable evaluation alternative to procedures that are contained in
- Para. 18.104.22.168. Adds an explicit statement that may accept existing
welds that are closer than API 650 limits if they are not being
modified or affected by repairs, provided that specified inspections
- Para. 4.3.10. Added explicit requirements for continued operation
of tanks that are in elevated temperature service, and for converting
tanks to operate at elevated temperature.
- Para. 5.3.8. Now explicitly recognizes that tanks constructed per
a recognized standard other than API 650 that has fracture toughness
rules (e.g., API 620) may be used per the current fracture toughness
rules of that standard.
- Para. 6.4.3. Adds
the presence or absence of a released prevention barrier under the
tank as an additional consideration in performing an RBI assessment.
- Para. 9.8.2. For new shell penetrations, a basis is provided for
determining required reinforcement area.
- Para. 9.8.3. Specifies when new penetrations must be prefabricated
into stress relieved insert plate assemblies.
- Para. 22.214.171.124. Requirements specified for leaving the upper half
of an existing reinforcing plate in place while replacing the lower
- Para. 126.96.36.199. When a bottom is replaced, requires that for
internal floating roofs with aluminum supports, stainless steel or
non-metallic spacers must be added to isolate supports from the carbon
- Para. 188.8.131.52. Considerations given when replacing bottom plates
in tanks that have cathodic protection or underbottom leak detection.
- New Appendix S. Covers requirements for existing stainless steel
tanks that were constructed per Appendix S of API 650. Only states
requirements that differ from the basic rules of API 653.