- The Body of Knowledge is the list of what can appear on the paper. It is not a syllabus with percentages.
- It is tied to a specific exam window, and it changes. The current one covers September 2026 to May 2027.
- Roughly eleven areas are examinable, weighted heavily towards the inspection code itself.
- The exclusions matter as much as the inclusions. Several whole sections are explicitly off the table.
- The topic list barely moved this cycle. What moved was which editions govern the answers.
What the Body of Knowledge actually is
It is a published list of what can appear on the exam, tied to specific exam dates. Nothing outside it is examinable, and anything inside it is fair game.
What it deliberately does not give you is a weighting. There is no official table saying calculations are worth twelve percent. That absence is why every prep provider quotes different numbers, and why you should treat any percentage you see, including ours further down, as an estimate rather than a fact.
Check which one applies to your exam date
This is the single most common mistake. More than one Body of Knowledge is published at any given time, because API posts the next cycle before the current one expires.
The current cycle covers the September 2026, January 2027 and May 2027 windows. If you sat in January or May 2026, you were on the previous one. Study material built for the wrong window will be right about the topics and wrong about some of the answers, and buying the wrong edition is one of the more expensive mistakes available.
The eleven areas, and roughly what they are worth
The examinable material breaks into about eleven areas. The percentages below are our own estimate, built from question frequency and the emphasis the Body of Knowledge places on each area. API publishes no official weighting, so treat these as a study guide rather than a specification.
The shape is the useful part. Nearly half the paper sits in the inspection code itself, and the next largest block is the calculations. Everything else is comparatively thin.
| Area | Roughly | What it covers |
|---|---|---|
| The inspection code | 45% | Intervals, evaluation of inspection data, repairs, alterations, rerating, records |
| Calculations | 12% | Corrosion rate, remaining life, intervals, MAWP, static head, hydrotest, weld sizes |
| Pressure vessel construction | 10% | Joints, materials, heads, openings, impact testing, pressure testing |
| Welding qualifications | 8% | Reviewing procedure and performance qualification records |
| Nondestructive examination | 7% | Radiography, penetrant, magnetic particle, ultrasonic thickness |
| Welding practice | 5% | Processes, inspection, metallurgy, common defects |
| Damage mechanisms | 5% | Fifteen named mechanisms, not the full catalogue |
| Pressure relieving devices | 3% | Inspection, testing and intervals |
| Inspection practices | 2% | Practical vessel inspection technique |
| Repairs | 2% | Named repair articles and their appendices |
| Material verification | 1% | Positive material identification programmes |
Closed book and open book are different exams
The Body of Knowledge marks which material you will have in front of you and which you must carry in your head. That distinction changes how you study each area far more than the topic weighting does.
The closed book half is 110 questions in 2 hours 45 minutes. It leans on the inspection code, damage mechanisms and welding practice, and it rewards recall at speed.
The open book half is 60 questions in 3 hours 45 minutes. This is where the calculations, the construction rules and the qualification reviews live. You have references on screen, but you have to know where to look before the clock beats you.
- Closed book: know it cold, because there is nothing to look at
- Open book: know where it lives, because reading time is the constraint
- The references are supplied as PDFs on the exam computer
- You cannot bring your own books or notes into the test centre
What is explicitly excluded
The exclusions are worth as much study time saved as the inclusions cost. Several substantial areas are ruled out entirely, and people routinely revise them anyway.
- Vessels in natural-resource service, an entire section of the inspection code
- One appendix of the inspection code
- External pressure calculations, though the rules themselves are examinable
- Relief device sizing, as opposed to relief device inspection
- Brazing
- Flanges, tubesheets, lifting lugs, wind and seismic loading
- Nozzle reinforcement arithmetic, though the concepts are examinable
- Advanced examination methods beyond the named articles
What changed for the 2026 to 2027 cycle
Comparing the current cycle against the previous one, the topic list is effectively unchanged. No new areas were added and none were dropped.
What did change is which editions govern the answers. Three construction and examination volumes rolled forward two years, and two correction notices joined the basis. There is no new edition of the inspection code itself.
That distinction matters more than it sounds. An unchanged topic list is exactly what makes people assume their old material is still fine. Coverage stayed the same; some of the answers did not.
Turning the list into a study plan
The Body of Knowledge is a checklist, not a curriculum. It tells you the boundary of the exam and nothing about how to get there.
The approach that works is to find your weak areas early rather than discovering them in week eleven. Sit something diagnostic in the first week, rank the eleven areas by how badly you did, then spend your time in proportion to the gap rather than in proportion to the topic weighting.
- Diagnose first, so you spend your effort where the gap actually is
- Weight your practice towards the code and the calculations, which carry over half the paper
- Do not over-revise the small areas just because they feel finishable
- Sit full timed mocks, because pacing is a separate skill from knowledge
- Re-test what you get wrong instead of rereading it
