API510 Approved References List: What Codes You Need 2026

Why the Approved References List Is the Exam's Foundation

Every API 510 Pressure Vessel Inspector exam question is traceable to a specific clause, table, or figure inside one of the approved reference documents. The American Petroleum Institute publishes a Body of Knowledge (BOK) for each examination window, and the BOK maps every testable task to an exact reference. For September 2025 through May 2026 exam windows, that mapping is fixed. If a document is not on the approved list, it will not appear in the exam - and if a document is on the list, you should assume every major clause of it is fair game.

This is not a soft guideline. API's Individual Certification Programs administer the exam through Prometric test centers under strict conditions: in-person only, no remote option, and no personal materials allowed in the testing room. The "open book" experience is entirely digital - PDFs pre-loaded on the Prometric workstation. That single constraint changes everything about how you should prepare. You are not studying to understand concepts in the abstract. You are training to locate specific clauses inside specific PDFs within a 3.75-hour window while answering 60 code-application questions.

The Complete 2026 Approved References List

The following documents appear on the current API 510 BOK for the September 2025-May 2026 examination windows. Edition years matter; confirm each against the official BOK before your exam date.

This list is not exhaustive of every sub-reference or appendix; the BOK task list provides granular clause-level traceability. Use the table above as a planning framework, not a definitive substitute for reviewing the official BOK document.

Open-Book Mechanics: PDFs, Navigation, and Time Pressure

Understanding the exam structure is inseparable from understanding how to use your references. The total exam day is 7.5 hours: a tutorial session, a 2.75-hour closed-book portion, a 45-minute lunch break, and a 3.75-hour open-book portion. The open-book 60 questions come entirely from Domain 2 code-application tasks. At 3.75 hours for 60 questions, you have roughly 3.75 minutes per question - which sounds generous until you factor in PDF navigation, cross-referencing two documents simultaneously, and the cognitive load of locating a specific table while reading a scenario question.

For a detailed breakdown of how the 170 total questions (140 scored, 30 unscored pretest) are distributed across closed and open-book portions, and how the scaled scoring process works, see API510 Exam Question Format and Structure Explained 2026 - it covers the equating methodology and what "scaled passing score" actually means for your preparation strategy.

Which Reference Covers Which Exam Domain

Mastering ASME Section VIII Division 1: The Heaviest Hitter

No single reference document generates more open-book questions than ASME Section VIII Division 1. Its UG (General Requirements), UW (Welded Vessels), and UCS (Carbon and Low-Alloy Steel) subsections are directly cited in API 510 BOK tasks related to fitness-for-service assessments, MAWP calculations, and weld examination requirements.

The Formulas You Must Locate Instantly

Under UG-27, the required thickness for cylindrical shells under internal pressure is the most commonly tested calculation. Candidates must also navigate UG-37 for reinforcement of openings, and UG-99/UG-100 for hydrostatic and pneumatic test requirements. These are not formulas to memorize - they are clauses to locate and apply correctly under time pressure.

Bookmark - or thoroughly annotate your digital workflow for - the following areas of Section VIII Div. 1:

• UG-27: Thickness of shells under internal pressure
• UG-28: Thickness of heads and shells under external pressure
• UG-37: Reinforcement required for openings in shells and formed heads
• Table UCS-23: Maximum allowable stress values for carbon and low-alloy steels
• UW-11: Radiographic and ultrasonic examination requirements by weld joint category
• UG-99/UG-100: Standard hydrostatic and pneumatic pressure test requirements

API 510 Standard Itself: The Inspector's Primary Authority

The API 510 standard is the only document that spans both exam portions. Its definitions, inspection interval tables, and repair/alteration authorization requirements appear in Domain 1 closed-book questions, and its fitness-for-service criteria cross-reference into Domain 2 open-book scenarios.

High-Priority Sections Within API 510

• Section 5 (Inspection Practices): Types of inspection, thickness measurement techniques, corrosion rate calculations - heavily tested in closed-book
• Section 6 (Inspection Data Evaluation): Remaining life calculations, corrosion rate selection (short-term vs. long-term), next inspection date determination
• Section 7 (Inspection Interval): Risk-based inspection (RBI) methodology, maximum inspection intervals, external inspection requirements
• Section 8 (Repairs, Alterations, and Re-rating): Authorization requirements, temporary repairs, re-rating procedures - appears in both portions
• Section 9 (Pressure-Relieving Devices): Cross-references to API RP 576, inspection frequency triggers

Candidates who underestimate API 510 Section 6 in particular consistently report surprises on exam day. The remaining life and corrosion rate calculation questions require you to understand the logic of the formulas, not just their algebra. Practice applying them to scenario data before your exam window opens.

You can work through representative code-application scenarios tied to these exact sections at our API 510 practice test platform, where questions are organized by reference document and BOK task.

Supporting Codes You Cannot Ignore

API RP 571: Damage Mechanisms

This recommended practice is uniquely demanding because it is primarily a closed-book reference - yet it covers over 60 damage mechanisms across mechanical, metallurgical, and corrosion categories. The exam tests your ability to identify a mechanism from a described scenario: appearance of damage, operating conditions, affected materials, and inspection methods that detect it. You cannot look this up on exam day for closed-book questions. Every mechanism in the refining-focused chapters (high-temperature hydrogen attack, wet H2S damage, amine corrosion, sulfidation, carbonate cracking) is fair game.

ASME Section IX: Weld Qualification

Open-book questions from Section IX tend to focus on whether a proposed weld procedure is properly qualified. Essential variables - base metal P-Number groupings, filler metal F-Numbers, PWHT requirements, and position qualifications - are the most commonly tested topics. The QW-250 through QW-280 series of tables and the QW-450 series for welder performance qualification are the two clusters you must be able to navigate efficiently.

API RP 576 and Pressure-Relieving Devices

PRD inspection questions appear in both portions. Closed-book questions test inspection intervals, pop-test frequency triggers, and documentation standards from memory. Open-book questions may require you to cross-reference API 510 Section 9 with RP 576 to determine whether a specific valve condition requires immediate action or can be deferred to the next scheduled inspection.

Acquiring and Organizing Your References Before Exam Day

Where to Obtain the Documents

ASME standards (Section V, VIII Div. 1, and Section IX) are available through the ASME Digital Collection or as individual PDF purchases through asme.org. API standards and recommended practices are available through the API Publications Store at api.org, with member pricing available if your employer holds an API membership. NBIC Part 2 is available through the National Board of Boiler and Pressure Vessel Inspectors at nationalboard.org.

Critically: verify the exact edition year specified in the current BOK for each document before purchasing. API updates its reference editions periodically, and purchasing a current edition when the BOK cites a prior edition - or vice versa - creates mismatches between your study materials and the PDFs loaded on the Prometric workstation.

A Structured Reference-Learning Schedule

Candidates preparing for the API 510 should also familiarize themselves with the approved references list overview for additional context on how the BOK maps specific exam tasks to document clauses.

One Note on the Exam Fee Investment

At $875 for API members and $1,125 for non-members for initial certification - plus the cost of reference documents - this examination represents a significant financial and time commitment. Recertification carries fees of $745 (member) or $855 (non-member). The cost of acquiring all approved references is a necessary part of that investment. Attempting the exam with incomplete reference materials is a false economy: the open-book portion is explicitly designed to test your ability to use the complete document set, not work from memory alone.

Practice under realistic conditions using digital references from the start. Our API 510 practice questions are organized by BOK domain and reference document, helping you build the dual skill of code knowledge and navigation speed simultaneously.

Frequently Asked Questions