API 653 Body of Knowledge 2026 — Topics + Code Mapping + What Changed

API 653 Body of Knowledge 2026 — Official Outline + What Changed

The API 653 Body of Knowledge (BOK) and Publications Effectivity Sheet define what the API 653 Aboveground Storage Tank Inspector exam can test. The current set covers the March, July and November 2026 windows. This page summarises them; download the originals from the API 653 program page before you study.

Reference Publications and Editions (2026 windows)

Publication	Edition on the effectivity sheet	Exam scope
API Std 653, Tank Inspection, Repair, Alteration, and Reconstruction	5th edition, November 2014, Addendum 1 (April 2018), Addendum 2 (May 2020), Addendum 3 (November 2023), Errata 1 (March 2020), Errata 2 (February 2025)	Per BOK
API Std 650, Welded Tanks for Oil Storage	13th edition, March 2020, Errata 1 (January 2021)	Per BOK
API RP 571, Damage Mechanisms	3rd edition, March 2020	Section 2 plus 10 listed mechanisms (below)
API RP 575, Inspection Practices for Atmospheric and Low-Pressure Storage Tanks	5th edition, September 2024	Per BOK
API RP 576, Inspection of Pressure-relieving Devices	5th edition, September 2024	Sections 4.3.2 and 6.7 only
API RP 577, Welding Processes, Inspection, and Metallurgy	3rd edition, October 2020	Per BOK
API RP 651, Cathodic Protection of Aboveground Petroleum Storage Tanks	5th edition, August 2024	Per BOK
API RP 652, Lining of Aboveground Petroleum Storage Tank Bottoms	5th edition, May 2020	Per BOK
ASME BPVC Section V	2023 edition	Articles 1, 2, 6, 7 and 23 (SE-797 only)
ASME BPVC Section IX	2023 edition	Welding only

Note that the exam uses API 653 through Addendum 3 and API 650 13th edition, even though API 653 Addendum 4 (July 2025) and API 650 14th edition (August 2025) have since been published. Work to the exam editions for the exam, and to the current editions on the job.

RP 571 Mechanisms on the Exam

Section 2 (terms and definitions) and paragraphs 3.8 atmospheric corrosion, 3.11 brittle fracture, 3.14 caustic corrosion, 3.15 caustic SCC, 3.19 concentration cell corrosion, 3.22 CUI, 3.28 ethanol SCC, 3.45 MIC, 3.57 soil corrosion and 3.62 sulfuric acid corrosion.

What Changed on the Latest Effectivity Sheet

Items API highlights as updated include RP 571 paragraphs 3.19 (concentration cell corrosion) and 3.28 (ethanol SCC), RP 575 5th edition (September 2024), RP 576 5th edition with section 6.7, RP 651 5th edition (August 2024), and API 653 Errata 2 (February 2025).

Not on the API 653 BOK: API 579-1/ASME FFS-1 (fitness-for-service) and API RP 580/581 (risk-based inspection) are not listed reference documents for this exam. You should understand that the code allows RBI to set intervals and refers damage beyond its own rules to an FFS evaluation, but there are no FFS or RBI calculation sets to study. API does not publish percentage weightings by document; any "weight map" you see elsewhere is an estimate, not API data.

Atlantis NDT does not run API 653 exam-preparation courses, and does not provide RBI or FFS services. This page is a free, independent summary of API's published documents.

Exam Format (api.org)

• 170 multiple-choice questions, of which 140 are scored and 30 are unscored pretest items
• Closed-book part: 110 questions in 2.75 hours; open-book part: 60 questions in 3.75 hours, with the references provided electronically; about 7.5 hours in total including tutorial and a 45-minute break
• In person at Prometric test centers only (remote proctoring for API 510, 570 and 653 ended with the September 2024 window)
• Scaled scoring; API reports a scaled score rather than a fixed percent-correct pass mark
• Prometric emails a score report, typically within 24 hours; API posts final results to the ICP portal afterwards
• Certification lasts 3 years; recertification needs at least 20% of working time on inspection activities and 24 CPD hours, plus a web quiz every 6 years

Always confirm the format, fees and dates on the API 653 program page before you book.

Study Strategy

• Index API 653 and API 650 in the exam editions; most open-book questions come from these two
• Drill shell t-min, remaining corrosion allowance and interval calculations (RCA/4N external, RCA/2N or 15 years UT), bottom minimums from Table 4.4, settlement evaluation (Annex B), hydrotest exemption rules and brittle-fracture screening
• Learn the 10 RP 571 mechanisms, RP 651 CP criteria and RP 652 lining types
• Practise WPS/PQR review against ASME IX

Free practice: API 653 practice questions. Code guide: API 653 explained.

Frequently Asked Questions

Q1: Is API 653 Addendum 4 on the 2026 exam?

A: No. The 2026 effectivity sheet lists API 653 through Addendum 3 plus Errata 2.

Q2: Which API 650 edition is used?

A: The 13th edition (March 2020) with Errata 1.

Q3: Are RBI or FFS on the API 653 exam?

A: API RP 580/581 and API 579-1 are not reference documents; know how API 653 itself uses RBI for internal intervals.

Q4: Is the exam fully open-book?

A: No. 110 questions are closed-book and 60 open-book.

Q5: What is the pass mark?

A: A scaled score; API does not publish a percent-correct pass mark.

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