Changes in API 653, Tank Repair, Alteration, and Reconstruction

By Vincent A. Carucci

Two addenda have been issued for the Fourth Edition of API 653 since it was published in April 2009. Addendum 1 was issued August 2010, and Addendum 2 was issued January 2012. The following highlights several of the changes that were made and is not all inclusive. Refer to API 653 for complete information.

Section 2: Referenced Publications

Several new references were added:

• API RP 580, “Risk Based Inspection”
• API RP 2009, “Safe Welding, Cutting, and Hot Work Practices in the Petroleum and Petrochemical Industries”
• NACE RP 0205-2005, “Recommended Practice for the Design, Fabrication, and Inspection of Tanks for the Storage of Petroleum Refining Alkylation Unit Spent Sulfuric Acid at Ambient Temperature”
• ANSI/AWS Z49-1, “Safety in Welding and Cutting and Allied Processes”

Section 3: Definitions

A definition for “door sheet” has been added. It is a plate (or plates) cut from the tank shell to create a temporary access opening. It is to be reinstalled or replaced after work is complete.

Section 4: Suitability for Service

• Para. 4.2.4.2 has been changed to require that the effects of partial vacuum be evaluated per API 650 Appendix V instead of API 620. API 620 was previously used as the evaluation basis before Appendix V was added to API 650.
• Para. 4.3.8 clarifies that the condition of tank shell welds shall be evaluated using criteria contained in API 653, the as-built standard, or by performing a fitness-for-service assessment.
• Paras. 4.4.6.2 and 4.4.6.3 clarifies that the required annular plate thickness from the referenced table in API 650 may be determined from interpolation using the calculated shell stress.

Section 6: Inspection

Significant changes were made to Para. 6.4.2 covering internal inspection intervals in Addendum 1 and again in Addendum 2.

• For existing tanks, tank owner/operators shall review the internal inspection interval and be in compliance with this section within 5 years from the date of first publication (Fourth Edition, Addendum 2, January 2012). This answers that commonly asked question.
• Initial and subsequent internal inspection intervals may be determined considering any leak prevention, detection, corrosion mitigation, or leak containment safeguards incorporated in the tank design and installation. For example, the initial inspection interval may be longer if an internal lining or cathodic protection system is installed. An example contained in API 653 shows that the maximum initial inspection interval for a 1/4 in. bottom with a fiberglass lining and release prevention barrier is 25 years. Refer to API 653 for details.
• Para. 6.4.2 also permits initial and subsequent internal inspection intervals to be determined using RBI procedures per API RP 580 and additional requirements contained in API 653 considering likelihood and consequence factors. Refer to API 653 for details.

Section 9: Tank Repair and Alteration

• Para. 9.2.4, Door Sheet Installation. This is a new paragraph, hence the need to define what a “door sheet” is in Section 3. It has seven sub-paragraphs and four new figures associated with it. Details are provided for door sheets made in riveted seam tanks, lap welded seam tanks, and butt welded seam tanks (e.g., minimum spacing required between new door sheet welds and existing shell seams). Before Addendum 2, API 653 did not have any detail requirements specifically for door sheets.
• Para. 9.10.1.2g is new. It defines minimum weld spacing requirements for when a tombstone bottom patch plate is installed in the critical zone if the tank shell plate is of unknown toughness. This is also addressed in Figure 9.13.

Section 13: Marking and Recordkeeping

Para. 13.1.2 is new and provides nameplate requirements for tanks that currently do not have nameplates. Two situations are covered:

• Replacement Nameplate. Information required by the as built standard to complete the nameplate is available and traceable to the tank.
• Assessment Nameplate. Information required by the as built standard to complete the nameplate is not available. In this case, information that was used in the assessment of the tank for its suitability must be identified.

Refer to API 653 for details.

Annex F: NDE Requirements Summary

Para. F.2.3 has been modified to require the examiner’s employer to determine and certify that each visual examiner meets API 650 requirements.

Annex X: Duplex Stainless Steel Storage Tanks

Added to correspond to tanks constructed per API 650, Appendix X.