This standard covers carbon and low alloy steel tanks built to API Standard 650 and its predecessor, API Specification 12C.

API 653 provides minimum requirements for maintaining the integrity of welded or riveted, atmospheric pressure, aboveground storage tanks after they have been placed in service. It covers the maintenance inspection, repair, alteration, relocation, and reconstruction of such tanks. The scope of this publication is limited to the tank foundation, bottom, shell, structure, roof, attached appurtenances, and nozzles to the face of the first flange, first threaded joint, or first welding-end connection.

This standard employs the principles of API 650; however, storage tank owner/operators may apply this standard to any steel tank constructed in accordance with a tank specification.

New revisions to the standard include:

Defining the responsibilities of the authorized inspector during repairs, alterations, and reconstruction.
Adding new definitions for a repair organization and a storage tank engineer.
Revision of the minimum weld spacing rules for tank bottom replacement.
Clarification of the minimum repair plate dimension for closure holes.
Restoring the “One-Foot Method” for determining the minimum acceptable thickness for an entire shell course.
Adding mandatory requirements for lap patch repair plates when used for hole closures.
Addition of a table listing the maximum allowable stress for materials covered in API 650.
New information in the NDE requirements summary in Appendix F.
Adding ASTM A992 to the list of acceptable specifications for structural steel shapes.