API 510 Body of Knowledge 2026: Reference Editions and What Changed

September 2026 update: the new API 510 Body of Knowledge and effectivity sheet

Short answer: API has published a new API 510 Body of Knowledge and a new Publications Effectivity Sheet for the September 2026, January 2027 and May 2027 exam windows. The new BOK replaces the September 2025 BOK. The main changes: the ASME Boiler and Pressure Vessel Code reference moves to the 2025 Edition, API 510 now carries Errata 2 (2025), RP 577 adds Errata 1 (September 2025), and three RP 571 mechanisms become examinable. Those three are boiler water and steam condensate corrosion, high-temperature H2/H2S corrosion and naphthenic acid corrosion. Download both documents from the API 510 page on api.org for your own exam date.

This update was checked against API's published documents in October 2026. Where an older figure elsewhere on this page or in a study guide conflicts with API's current certification page, BOK or effectivity sheet, API's documents govern. API revises them for each window, so re-check them a few weeks before your exam.

Body of Knowledge vs effectivity sheet: what each one controls

The two documents do different jobs. The Body of Knowledge lists the topics, calculations and code sections the API 510 inspector should know, and the ones that are excluded. The Publications Effectivity Sheet names the exact edition, issue date and errata of each publication. API's certification page says exam questions are derived from the publications listed on the effectivity sheet.

The September 2026 BOK makes three rules explicit. First, questions use only information in the listed references, at the editions on the effectivity sheet. Second, questions can come from anywhere in a listed document unless the BOK excludes that part. Where only some sections are excluded, everything else in the document is in scope. Third, where the BOK points to a specific paragraph (its example is metal loss in API 510 paragraph 7.4), the reference is a study aid. It does not exclude the paragraphs around it.

The BOK also says something owners should note: some organisations and jurisdictions work to documents or editions other than those on the effectivity sheet, for example where a state rule has adopted an earlier edition. The exam is still based on the effectivity sheet editions. Keep your study set separate from the set your plant works to.

API 510 publications for September 2026, January and May

As listed on API's effectivity sheet for these three windows:

• API 510, 11th Edition (October 2022), with Errata 1 (March 2023) and Errata 2 (2025).
• API RP 571, 3rd Edition (March 2020). Limited to Section 2 (terms and definitions) and fifteen mechanisms: amine SCC, atmospheric corrosion, boiler water and steam condensate corrosion, brittle fracture, caustic corrosion, caustic SCC, chloride SCC, corrosion under insulation, erosion/erosion-corrosion, high-temperature H2/H2S corrosion, high-temperature hydrogen attack, hydrochloric acid corrosion, naphthenic acid corrosion, sulfidation, and wet H2S damage (blistering, HIC, SOHIC, SSC).
• API RP 572, 5th Edition (November 2023). The BOK includes Annexes A and B and excludes Annex C.
• API RP 576, 5th Edition (September 2024). The BOK excludes the annexes.
• API RP 577, 3rd Edition (October 2020), with Errata 1 (September 2025). Examined in full.
• API RP 578, 4th Edition (February 2023). Examined in full.
• ASME BPVC 2025 Edition: Section V Articles 1, 2, 6, 7 and 23 (SE-797 only); Section VIII Division 1 (U, UG, UW and UCS, and Mandatory Appendices 1-4, 6, 8 and 12); Section IX, welding only.
• ASME PCC-2 (2022). Limited to fourteen named articles, covering insert plates, external weld buildup, alternatives to PWHT, in-service welding, weld overlay, fillet-welded patches, Cr-Mo repair welding, hot taps, flaw excavation, flange repair, heat exchanger inspection and repair, pressure and tightness testing, and NDE in lieu of pressure testing.

API highlights recent changes in red on the sheet. In this window the red items are the three added RP 571 mechanisms, API 510 Errata 2, RP 577 Errata 1 and the 2025 ASME Code year. If your Section VIII and Section V tabs come from a 2023 Code set, re-tab them against the 2025 Edition before you practise open-book questions.

Calculation scope: what the 2026- BOK expects you to work

The BOK frames calculation questions around existing vessels, not new design, and limits them to internal pressure loading. Candidates are expected to use both US customary and SI units. In summary, the inspector should be able to:

• Take inspection data and determine internal and external inspection intervals. That means calculating metal loss, corrosion rate, remaining corrosion allowance, remaining life and the next inspection interval under API 510. The BOK warns that these formulas and the interval rules may be tested closed-book.
• Determine weld joint efficiency from the joint category, the radiography marking on the nameplate and the Section VIII joint efficiency table. This includes the seamless-section and welded-pipe cases.
• Account for static head (based on a specific gravity of 1.0), tell vessel MAWP apart from vessel-part MAWP, and work out total pressure on a part.
• Calculate required thickness and part MAWP for cylindrical and spherical shells and for ellipsoidal and hemispherical heads. The Appendix 1 outside-diameter formula for cylinders may be used. Non-standard head formulas are not required.
• Adjust hydrostatic and pneumatic test pressures for temperature, and know the test precautions and steps.
• Apply impact test requirements and determine impact-test exemption from minimum metal temperature.
• Check fillet weld throat-to-leg conversions and required weld sizes at openings. Nozzle reinforcement is tested as concepts: replacing the strength removed, and the limits of reinforcement.

External pressure is knowledge only. The BOK says candidates should understand the external pressure rules but will not be asked to calculate them.

What the BOK says you will not be tested on

The exclusions list is the fastest way to cut study time, and many candidates never read it. The September 2026 BOK lists 22 ASME engineering topics outside the exam. Among them are thickness for wind, earthquake and other secondary loads; flange, ligament, tubesheet, stayed-head and lifting-lug calculations; relief valve sizing; proof testing; Zick analysis; cryogenic vessels below -50°F; jacketed, dimpled and non-metallic vessels; acoustic emission, eddy current and motion radiography NDE requirements; a list of Section VIII parts (UF, UB, UNF, UHA, UCI, UCL, UCD, UHT, ULW, ULT, UHX and UIG); Code Cases and interpretations; and pressure vessels for human occupancy. API 510 Section 9 (natural resource vessels) and Appendix E are excluded as well.

The welding review is tightly bounded. It covers a WPS with its single supporting PQR and a WPQ, using SMAW, GTAW, GMAW or SAW only, one process and one filler metal per document. Base metals are limited to P-No. 1, 3, 4, 5 and 8. Supplementary essential variables, dissimilar base metals and thicknesses, corrosion-resistant overlay, hardfacing and buttered dissimilar metal welds are all excluded. Brazing is not covered. Where API 510 and Section VIII both have welding rules, the BOK notes that API 510 takes precedence.

NDE scope: where API 510 stops and the NDE technician starts

The NDE content is limited to these Section V articles:

• Article 1: scope, use as a referenced code, owner and subcontractor responsibilities, calibration, the inspection vs examination definitions, and records.
• Article 2: radiography. Marking, IQI selection and placement, density, backscatter control and location markers.
• Article 6: liquid penetrant, including two mandatory appendices.
• Article 7: magnetic particle, yoke and prod techniques only.
• Article 23, SE-797 only: manual contact pulse-echo thickness measurement.

It also covers the general NDE rules in Section VIII Division 1 and in API 510.

The ultrasonic content is therefore thickness measurement, not angle-beam flaw detection, sizing or phased array. That matters in two directions. An ASNT Level II UT, MT, PT or RT technician moving towards API 510 already knows the practical side and mainly needs code literacy: responsibilities, procedure content and records. An owner should not read an API 510 certificate as evidence of weld-UT competence. That comes from ASNT qualification under the employer's written practice, plus performance demonstration where the owner specifies it. Our guide to ASNT Level III vs API QUTE covers that boundary.

Exam format as API currently publishes it

API's API 510 certification page describes the exam this way. It runs 7.5 hours: a short tutorial, 2.75 hours for the closed-book portion, a 45-minute lunch and 3.75 hours for the open-book portion. It has 170 questions, of which 140 are scored. The remaining 30 are pretest questions that do not affect your score. 110 questions are closed-book and 60 are open-book. The page says the exam is delivered in person at designated Prometric test centres, and that only the effectivity-listed sections are available for the open-book portion. API's API 570 and API 653 pages describe the same 170/140 and 110/60 structure.

The BOK explains how the two halves differ. The closed-book part tests everyday working familiarity with API 510 and its references. The open-book part tests detailed information an inspector should be able to find but would not usually memorise. Study to match: learn interval rules, corrosion rate and remaining life methods and the main definitions by heart, and practise finding tables, figures and acceptance criteria quickly in the effectivity editions.

How the API 510 sheet compares with API 570 and API 653

Candidates holding more than one certification, and employers sponsoring several, often assume the three programmes change together. They do not.

For the API 570 February and June 2027 windows, API has published a sheet with the same editions as its 2026 sheet. For API 653, the 2027 sheet changes API 650 to the 14th Edition, adds API 653 Addendum 4 (July 2025), moves RP 652 to the 6th Edition and moves ASME to 2025. That is a full book change from the 2026 windows.

Recertification uses a different effectivity sheet

Certified inspectors do not re-sit the full exam. API's page says API 510 certification runs for three years, with applications accepted 90 days before expiry and a 90-day grace period after. Renewal needs evidence that at least 20% of your time in the three-year period was spent performing or supervising pressure vessel inspection, plus 24 hours of continuing professional development relevant to inspection and mechanical integrity in each cycle. Every six years, inspectors take an online open-book quiz of 25 questions on code changes over the previous six years. You have four hours and can pause up to three times. Failing it twice means a new application and the full exam.

The quiz is based on a separate recertification effectivity sheet. API lists the API 510 version as valid from October 20, 2025. Do not prepare for the quiz from the initial-exam sheet.

Common mistakes with the 2026- documents

• Studying from an older BOK. The September 2025 BOK has been replaced for the September 2026 window onwards. Check the window dates printed at the top of whatever you are using.
• Keeping 2023 ASME tabs. The API 510 sheet now lists the 2025 Code.
• Skipping the new RP 571 mechanisms. Boiler water and condensate corrosion, high-temperature H2/H2S corrosion and naphthenic acid corrosion are now listed alongside the existing twelve.
• Assuming API 579 or API 580 is on the API 510 exam. Neither appears on the September 2026 effectivity sheet or BOK reference list. Fitness-for-service and risk-based inspection are separate engineering disciplines and separate API certifications.
• Treating paragraph references as limits. The BOK says listed paragraphs are aids, not exclusions.
• Using unauthorised copies. The sheet reminds candidates that API and ASME documents are copyrighted, and points to API's authorised redistributor.

How Atlantis supports API 510 candidates and programmes

Atlantis NDT does not run API 510 exam preparation or any API ICP course. For owners running API 510 programmes, our ASNT-certified technicians perform the NDE the code calls for under ASNT Level III oversight: UT thickness and CML surveys, corrosion mapping, PAUT, MT, PT and VT. We deliver results to the owner's API-certified inspector, who stays the inspector of record. See pressure vessel inspection services and NDE support for API 510 programmes. For technicians building the inspection experience API eligibility asks for, we train to ASNT SNT-TC-1A: NDT Level II training, ASNT certification and Level III training. Ask about ASNT training for your team or request NDE support for an API 510 programme. We reply within one business day.

More questions on the 2026 API 510 BOK

Which API 510 body of knowledge applies to exams in late 2026?

The BOK dated for September 2026, January 2027 and May 2027, which replaces the September 2025 BOK. Use it with the matching effectivity sheet.

Is the API 510 effectivity sheet for 2026 the same as the BOK?

No. The effectivity sheet lists editions and errata. The BOK lists topics, calculations and exclusions. You need both.

Which ASME edition is on the API 510 exam from September 2026?

The 2025 Edition of the ASME BPVC, limited to the Section V, VIII Division 1 and IX content listed on the sheet.

Are API 570 and API 653 on the same 2026 cycle?

No. API 570 publishes one sheet for 2026 and one for February and June 2027. API 653 publishes sheets for the March, July and November windows of each year. Their editions differ from API 510's.

Does Atlantis offer API 510 study material?

No. Use API's ICP pages for the BOK and effectivity sheet. Atlantis offers ASNT SNT-TC-1A NDT training and NDE inspection services. Talk to us about ASNT Level II UT training.