Part of the expanding PassProfessor catalog: this guide covers API’s API 510 Pressure Vessel Inspector examination as API publishes it — 170 questions (140 scored, 30 unidentified pretest) in a 7.5-hour Prometric day, 110 closed-book and 60 open-book, passed at a scaled score of 400 on the 200 to 500 scale, and built to the effectivity pins for September 2026 to May 2027. PassProfessor’s companion practice program is in the works.
The program is in the works, built on the published Body of Knowledge for this examination. Join the notify list and we will email you when enrollment opens — then use this guide to plan your preparation area by area.
The API 510 credential is the pressure vessel inspector’s authorization: it certifies that an inspector can inspect, rate, repair, and rerate in-service pressure vessels under the API 510 code and the reference publications API pins to the examination. This guide does the planning work in the open: it states the examination’s verified facts, lists the pinned editions that define the current cycle, walks the Body of Knowledge area by area with a preparation method for each area, explains scoring in API’s own terms, and ends with a study plan. Everything factual in it comes from API’s published materials recorded in this guide’s internal sources section; where those materials direct candidates to confirm a current detail — a fee, a window date — the guide says so rather than printing an unverified figure.
Which examination is this?
This page covers one credential only: the API 510 Pressure Vessel Inspector certification, administered by the American Petroleum Institute (API) through its Individual Certification Programs (ICP). It is not a guide to API 570 (piping) or API 653 (storage tanks): each API program has its own Body of Knowledge and its own pinned editions, and confusing them is a real preparation error — the damage-mechanism list, the repair-article list, and several editions differ between programs, and this guide prints only this program’s. It is also built to one cycle only: the Body of Knowledge and effectivity sheet for the September 2026, January 2027, and May 2027 examinations. The September 2026 window has run; the remaining windows under this cycle are January 2027 and May 2027.
The real exam at a glance
| Fact of record | Detail |
|---|---|
| Credential | API 510 Pressure Vessel Inspector, administered by API’s Individual Certification Programs (ICP); the program is ANSI-accredited under ISO/IEC 17024 |
| Format | 170 questions: 140 scored and 30 unidentified pretest questions that do not affect the score. 110 closed-book questions and 60 open-book questions |
| The exam day | 7.5 hours in total: a short tutorial, 165 minutes (2.75 hours) closed-book, a 45-minute lunch break, and 225 minutes (3.75 hours) open-book — 390 minutes of testing time |
| Delivery | Computer-based at Prometric test centers, in person only. API states expressly that the API 510 examination is not available for remote testing |
| References on the day | Papers, notes, and books are not allowed in the test center. During the open-book part only, PDF documents of the pertinent codes and standards are provided on the exam computer, limited to the sections listed on the effectivity sheet. A calculator, scratch paper, and pencil are provided |
| Item formats | The majority of questions are multiple-choice, single-answer. API is gradually adding Alternative Item Types — such as drag and drop, ordered response, multiple response, and matching — into its examinations |
| Scoring | Prometric reports a scaled score on a scale from 200 to 500. The passing scaled score is 400, as API publishes it. Score reports show the converted scaled score, not the number of questions answered correctly |
| Eligibility | Education plus pressure-vessel experience acquired within the last 10 years, documented on the application and verified by API. No training course is required to sit the exam |
| Current cycle | Body of Knowledge and effectivity sheet for the September 2026, January 2027, and May 2027 examinations. Confirm current window dates and all fees at api.org when you apply |
| Application | Apply through API’s ICP Portal. An application is valid for 6 months from the first exam date requested. After approval, API issues an Exam Authorization with an Eligibility ID and the candidate books a Prometric seat inside the approved window |
| Examination fee | Confirm the current fee on API’s ICP Schedules & Fees page at api.org when you apply. This page prints no fee figure |
| Keeping the credential | Certification runs in 3-year terms, with work, continuing professional development, and a 6-year web quiz — see the recertification section below |
Which editions does the current cycle pin?
The effectivity sheet is the examination’s reading list with the editions fixed. For the September 2026 to May 2027 cycle, API pins the following — transcribed from the effectivity sheet itself, and the editions the companion practice program is built to:
- API 510, Pressure Vessel Inspection Code, 11th Edition (October 2022), Errata 1 (March 2023) and Errata 2 (2025).
- API RP 571, Damage Mechanisms Affecting Fixed Equipment in the Refining Industry, 3rd Edition (March 2020) — only Section 2 (Terms and Definitions) and fifteen listed mechanisms: amine stress corrosion cracking; atmospheric corrosion; boiler water and steam condensate corrosion; brittle fracture; caustic corrosion; caustic stress corrosion cracking; chloride stress corrosion cracking; corrosion under insulation; erosion and erosion-corrosion; high-temperature hydrogen/hydrogen sulfide corrosion; high-temperature hydrogen attack; hydrochloric acid corrosion; naphthenic acid corrosion; sulfidation; and wet hydrogen sulfide damage (blistering, hydrogen-induced cracking, stress-oriented hydrogen-induced cracking, and sulfide stress cracking). No other RP 571 mechanism is in scope.
- API RP 572, Inspection Practices for Pressure Vessels, 5th Edition (November 2023) — the whole document including Annexes A and B; Annex C is excluded.
- API RP 576, Inspection of Pressure-relieving Devices, 5th Edition (September 2024) — the whole document except its annexes.
- API RP 577, Welding Processes, Inspection, and Metallurgy, 3rd Edition (October 2020), Errata 1 (September 2025).
- API RP 578, Material Verification Program for New and Existing Assets, 4th Edition (February 2023).
- ASME Boiler and Pressure Vessel Code, 2025 Edition — limited to Section V, Nondestructive Examination, Articles 1, 2, 6, 7, and 23 (Section SE-797 only); Section VIII, Division 1 — Introduction (U), UG, UW, UCS, and Appendices 1–4, 6, 8, and 12; and Section IX, welding only.
- ASME PCC-2, Repair of Pressure Equipment and Piping, 2022 — only Articles 101, 201, 202, 209, 210, 211, 212, 215, 216, 304, 305, 312, 501, and 502, each with its appendices.
Three of these pins rolled forward from the previous cycle: the ASME BPVC moved from the 2023 Edition to the 2025 Edition; API 510 gained Errata 2; and API RP 577 gained Errata 1. The Body of Knowledge’s topic list is effectively unchanged — it is the editions underneath it that moved. Answers that differ between editions, or before and after either errata, key to the current pinned text, regardless of which edition a candidate’s workplace still uses. The scope limits matter as much as the editions: API 510’s Section 9 and Appendix E are excluded; brazing is not covered, because the Section IX scope here is welding only; and the examination scope excludes acoustic emission, eddy current, and motion radiography.
Who can take this exam, and what does it certify?
Qualification combines education with pressure-vessel experience acquired within the last 10 years while employed by, or under contract with, an authorized inspection agency as defined in API 510; it must be documented on the application, and API verifies it after submission. As API publishes the table: a bachelor’s degree or higher in engineering or technology — or 3 or more years of military service in a technical role — requires 1 year of supervision or performance of API 510 inspection activities. A 2-year degree or certificate in engineering or technology — or 2 years of military service in a technical role — requires 2 years of design, fabrication, repair, operation, or inspection of pressure vessels, including 1 inspection year. A high school diploma or equivalent requires 3 years on the same terms. With no formal education, 5 or more years are required, including the same inspection year. No training course is required, and API does not endorse test-preparation classes. Candidates whose applications are marked unqualified must submit a new application. The credential is awarded by API alone; PassProfessor does not certify inspectors and does not enrol candidates for the official examination — candidates apply through API’s ICP Portal and sit at Prometric.
What makes this test demanding?
Three features make this examination harder than a single-code test. First, the two-part structure: 110 closed-book questions test what an inspector is expected to know cold — intervals, responsibilities, inspection types, damage-mechanism recognition, welding and examination essentials, stated factors and rules — then, after a lunch break, 60 open-book questions test how well the same inspector can find and apply detailed information under time pressure, in a provided-PDF environment limited to the effectivity sheet’s sections. Second, the calculation load: corrosion rates, remaining life, intervals, joint efficiencies, static head, and required thickness are worked, not recalled, in both US customary and SI units. Third, the breadth of the pinned library, each publication included only to a stated depth that the candidate is responsible for knowing — the exclusions are part of the syllabus, because study time spent on excluded material is study time taken from tested material. Sustained practice that mixes closed-book recall, record review, and open-book-style application is therefore the centre of serious preparation, not an advanced extra.
The outline, area by area
API’s Body of Knowledge has five sections: thickness measurements, inspection intervals and vessel integrity; welding procedure and qualification evaluation; nondestructive examination; practical knowledge — general; and practical knowledge — specific, publication by publication. API publishes no weighting for this examination — no percentage or question count per topic. The nine areas below divide the practice bank; their counts are a PassProfessor allocation, set in proportion to the Body of Knowledge’s emphasis, and they are never API’s weighting.
| Practice area | Practice questions |
|---|---|
| Thickness, Intervals and Vessel Integrity Calculations | 320 |
| API 510 Inspection, Rating, Repair and Alteration | 210 |
| Welding Procedure and Qualification Evaluation | 180 |
| Nondestructive Examination | 170 |
| Damage Mechanisms (API RP 571) | 170 |
| Inspection Practices and Pressure-Relieving Devices | 120 |
| Materials, Fabrication and Practical Knowledge | 120 |
| Repair Methods (ASME PCC-2) | 110 |
| Welding Processes, Metallurgy and Material Verification | 100 |
| Total | 1,500 |
What do the thickness, interval, and integrity calculations cover?
Corrosion rates, metal loss, remaining corrosion allowance and remaining life; inspection interval determination, internal and external; joint efficiencies, including weld joint categories and the radiography basis read from nameplate markings and the joint-efficiency table; static head, and the difference between a part’s maximum allowable working pressure and the vessel’s; required thickness and maximum allowable working pressure for cylindrical and spherical shells and for ellipsoidal and hemispherical heads under internal pressure, including corrosion-allowance compensation and the outside-diameter cylinder formula; pressure-test pressures, including temperature compensation; and impact-testing requirements and minimum design metal temperature exemptions. Calculation questions are oriented to existing vessels under internal pressure, in both unit systems.
How should you prepare for the calculations? Work them, in both unit systems, until the sequence is automatic: establish the corrosion rate, derive remaining life, and let the interval follow. Practise the closed-book factors the Body of Knowledge makes knowledge in themselves — the static-head conversion and the fillet-weld throat conversion among them — and keep the excluded families out of your drilling: external-pressure calculations and nozzle-reinforcement calculations are treated as rules and key concepts only, and relief-valve sizing calculations are not a tested family at all.
Remaining life is the hinge number: most interval and repair decisions on the examination turn on computing it correctly from the corrosion rate and the remaining allowance, in the units the stem gives.
What does the API 510 code area cover?
The code itself, applied: how inspection is organized, the certification requirements behind the credential, and the types of inspection; inspection planning, interval questions, records, and reports; repairs and alterations to pressure vessels; rerating; pressure testing after a repair, alteration, or rerating; and corrosion and minimum-thickness evaluation in applied situations.
How should you prepare for the API 510 code area? Study it as decisions, not as text: given this finding, this history, and this vessel, what does the code require next — inspect, repair, alter, rerate, test, or return to service — and who is responsible for each step? The area rewards candidates who can run the code’s logic forward from a described situation.
Where API 510 and ASME Section VIII rules overlap on welding, API 510 takes precedence — record-review items key accordingly, and so does the practice.
What does welding procedure and qualification evaluation cover?
Welding procedure specifications, procedure qualification records, and welder performance qualifications checked for compliance; essential and nonessential variables and the mechanical tests a procedure qualification requires; welder qualification, processes, filler metals, and base-metal limits; and the general welding requirements in ASME Section VIII and API 510. Examination record review is bounded: the common arc processes — shielded metal arc, gas tungsten arc, gas metal arc, and submerged arc — one process per record set, one filler metal per process, a single supporting qualification record, on a defined set of base-metal groups, with no dissimilar-metal or dissimilar-thickness joints and no overlay, hard-facing, or buttering. Editorial record content — revision levels, company names, record numbers and dates, laboratory names — is not the knowledge, though certification of a qualification record by signature and date is.
How should you prepare for welding qualification? Practise reading records against the variables: cover the record, name the essential variables the described weld engages, then check. The skill is spotting the one change that outruns the supporting qualification.
A record can be complete, signed, and still wrong: the deciding feature is usually a variable that changed beyond what the supporting qualification covers.
What does nondestructive examination cover?
The general requirements article of Section V; radiographic examination; liquid penetrant examination, including its mandatory appendices named in the Body of Knowledge; magnetic particle examination, limited to the yoke and prod techniques; ultrasonic thickness measurement under the SE-797 section; and the general nondestructive examination requirements carried in ASME Section VIII and API 510.
How should you prepare for nondestructive examination? Learn each method as a pairing of capability and limit: what it finds, what it cannot find, what it requires of the surface and the material, and which article’s rules govern its acceptance on this examination. Method-selection items punish candidates who know procedures but not limits.
Match the method to the discontinuity and the material: an option naming a sound method for the wrong condition is the distractor the examination favours.
What do damage mechanisms cover?
API RP 571’s terms and definitions section, and the fifteen mechanisms listed in the pinned-editions section above — no others. The list is this program’s own: mechanisms that appear on other API programs’ lists but not on this one are out of scope here, and the reverse is equally true.
How should you prepare for damage mechanisms? Study each mechanism as a four-part signature — susceptible materials, the environment that drives it, the temperature and stress conditions it needs, and where the damage appears — because examination items present three or four of those features and ask the candidate to complete the identification, or present the mechanism and ask where an inspector looks for it.
Mechanism items turn on the combination: material, environment, temperature, and stress together name the mechanism; any one of them alone does not.
What do inspection practices and pressure-relieving devices cover?
API RP 572, inspection practices for pressure vessels — the whole document including Annexes A and B, with Annex C excluded — and API RP 576, inspection of pressure-relieving devices, the whole document except its annexes.
How should you prepare for inspection practices and relief devices? Prepare in the field’s order: what is examined, in what sequence, with what evidence recorded, and what finding triggers what action. Relief-device content deserves deliberate time — candidates under-prepare it because it feels peripheral, and the Body of Knowledge does not treat it that way.
A relief device is part of the vessel’s integrity case, not an accessory: inspection findings on the device carry the same weight as findings on the shell.
What do materials, fabrication, and practical knowledge cover?
Types of process corrosion and deterioration; modes of mechanical, thermal, and high-temperature deterioration; pressure vessel materials and fabrication problems; the ASME Section VIII construction requirements — the general requirements, the carbon-steel requirements, and the listed appendices — that underlie inspection decisions; welding on pressure vessels in general practice; and maintenance inspection safety practices.
How should you prepare for practical knowledge? Connect every finding to its cause and its consequence: the same measured wall loss supports different decisions depending on the deterioration mode behind it, and the examination’s practical items are built on exactly that difference.
Practical items reward the candidate who connects the finding to the cause: the same wall loss reads differently depending on the deterioration mode behind it.
What do repair methods cover?
ASME PCC-2’s fourteen listed articles for this program, each with its appendices: scope and organization and repair concepts; insert plates, external weld buildup, weld overlay, and fillet-welded patches; alternatives to postweld heat treatment, in-service welding, and welded hot taps; chromium-molybdenum repair welding and flaw excavation and weld repair; flange repair and conversion and shell-and-tube heat exchanger repair; and pressure and tightness testing, including nondestructive examination in lieu of a pressure test. Articles outside the list are not on this examination.
How should you prepare for repair methods? Prepare by situation: for each article, hold the damage it addresses, the conditions it requires, and the verification it demands afterwards. Examination items describe a repair situation and ask which method fits — or which condition rules a method out.
The repair question is never only whether a method exists: it is whether the method fits this vessel, this damage, and these conditions.
What do welding processes, metallurgy, and material verification cover?
API RP 577 across the whole document as pinned — welding processes, inspection, and metallurgy — and API RP 578 across the whole document: the material verification program for new and existing assets, including positive material identification practice and program requirements.
How should you prepare for welding processes and material verification? Keep the two halves distinct in your notes: process and metallurgy knowledge on one side, verification-program discipline on the other. Items in this area often hinge on whether a described step belongs to the welding process itself or to the verification program surrounding the material.
A material verification failure is an integrity failure found early: the practice treats identification questions with the same seriousness as thickness questions.
How is API 510 scored?
API publishes the standard as a scaled score. Prometric uses a scale from 200 to 500 for API’s Individual Certification Programs examinations, and the passing scaled score for the API 510 examination is 400. A scaled score is not a percentage of questions answered correctly, and API publishes no percentage pass mark, no raw pass mark, and no number-correct threshold. API’s equating process adjusts for differences in difficulty between forms, so the number of correct answers corresponding to the passing scaled score may differ slightly from form to form while the scaled standard represents the same minimum knowledge. Score reports show the converted scaled score, not the number answered correctly; reports are emailed by Prometric within 24 hours of testing, and results upload to the ICP Portal within 3 business days. API will not disclose or return the contents of a failed examination. The practical consequence: there is no published percentage to aim practice at. Aim instead at breadth and reliability — consistently strong practice across all nine areas, in both styles — because the scaled standard is a fixed level of minimum knowledge, not a curve.
How do inspectors keep the credential?
Certification is valid for a 3-year term. At each recertification the inspector shows two things: work — a minimum of one fifth of working time over the most recent 3-year period spent performing or supervising pressure vessel inspection activities as described in API 510 (inspectors not actively engaged must take the full examination again); and continuing professional development — 24 CPD hours per 3-year cycle, relevant to inspection and mechanical integrity, spread across at least two activity categories, with proof uploaded to the ICP Portal. Recertification is applied for online in the ICP Portal, from 90 days before expiry through a 90-day grace period after it; late fees apply after expiry, and an inspector who has not applied by the end of the grace period must take a full examination again. Every 6 years the inspector must also pass an online, open-book web quiz on changes to the relevant codes: 25 questions in 4 hours, which may be paused up to three times, available in the same window around expiry; failing it once allows a retake, and failing a second time ends recertification. The web quiz is scoped by a separate recertification effectivity sheet — a different document from the examination effectivity sheet this guide builds to. Since June 2025, API issues its ICP certifications digitally.
An honest note on format
Every PassProfessor practice question is a single-answer, four-option item. The real examination’s majority format is also multiple-choice, single-answer — but API is gradually adding Alternative Item Types (drag and drop, ordered response, multiple response, and matching), the real sitting splits into closed-book and open-book parts, and the open-book part runs in Prometric’s provided-PDF environment, limited to the effectivity sheet’s sections. Practice here does not reproduce that environment, those item types, or the two-part sitting. It builds the knowledge and calculation skills the Body of Knowledge requires. Practice results are a study gauge — a way to see which areas are thin while there is time to repair them — not a prediction of a scaled score, and no practice percentage converts into one.
How should you read your practice results?
An overall practice score is the least useful number a candidate owns. The useful reading is by area: which areas are secure, which are inconsistent — right on recall, wrong on record review or calculation — and which are simply thin. Each pattern has a different repair. A secure area needs only maintenance in mixed practice. An inconsistent area usually means one skill inside it is lagging — a calculation family, a record feature, a mechanism signature — and needs slower, worked practice on that skill. A thin area needs study in the pinned publication before drilling, because drilling untaught material rehearses guessing. Revisit each repaired area after a gap of several days, in mixed practice, so retention — not recognition of recently seen material — carries the result. Read the two examination styles separately as well: the repair for closed-book weakness is familiarity work; for open-book-style weakness it is document-navigation and multi-step application work.
A study plan that follows the outline
- Start with the calculations. Thickness, intervals, and vessel integrity carry the practice bank’s largest allocation because the Body of Knowledge’s required skills are densest there — and calculation fluency, once built, supports the code, repair, and practical areas that use its results.
- Take the API 510 code area next, then work area by area, drilling as you go. Take each area’s practice after studying it and repair misunderstandings while the material is fresh.
- Read results by area, not just by score. A single overall figure hides the thin area; on a two-part examination it also hides which sitting style — closed-book or open-book — is costing you.
- Hold the pinned editions open beside you for open-book-style work. Practise finding and applying, not only remembering: know which publication, and which part of it, answers each kind of question, within the effectivity sheet’s stated limits.
- Finish with full simulations. Sit timed practice at the real sitting’s total testing time, in both styles, so retrieval mixes areas the way the real day does — and confirm your window dates and fees at api.org as you apply.
Frequently asked questions
How many questions are on the API 510 exam, and how long is it? 170 questions in a 7.5-hour day: 140 scored and 30 unidentified pretest questions that do not affect the score, split into 110 closed-book questions in 165 minutes and 60 open-book questions in 225 minutes, with a 45-minute lunch break between the parts.
What score passes the API 510 exam? A scaled score of 400 on Prometric’s 200 to 500 scale, as API publishes it. A scaled score is not a percentage of questions answered correctly; API publishes no percentage pass mark and no number-correct threshold, and the number of correct answers corresponding to the passing scaled score may differ slightly between forms because of equating.
Can I take the API 510 exam from home? No. API states expressly that this examination is not available for remote testing; it is taken in person at a Prometric test center.
What references can I use during the exam? None of your own — papers, notes, and books are not allowed in the test center. During the open-book part only, PDF documents of the pertinent codes and standards are provided on the exam computer, limited to the specific sections listed on the effectivity sheet. A calculator, scratch paper, and pencil are provided.
Which editions does the current exam test? The editions pinned on the effectivity sheet for the September 2026 to May 2027 cycle: API 510, 11th Edition with Errata 1 and 2; RP 571, 3rd Edition, Section 2 and fifteen listed mechanisms only; RP 572, 5th Edition; RP 576, 5th Edition; RP 577, 3rd Edition with Errata 1; RP 578, 4th Edition; the ASME Boiler and Pressure Vessel Code, 2025 Edition, in the stated sections; and ASME PCC-2, 2022, in fourteen listed articles. This guide’s pinned-editions section gives the full list with every limit.
Does API publish how the exam is weighted by topic? No. API publishes no weighting, percentage, or per-topic question count for this examination. The area counts in this guide are a PassProfessor allocation of the practice bank, set in proportion to the Body of Knowledge’s emphasis — they are not API’s weighting.
What experience do I need to qualify? Education plus pressure-vessel experience acquired within the last 10 years with an authorized inspection agency, documented and verified by API: 1 year of inspection activity with an engineering or technology degree (or the military-service equivalent), rising through 2 and 3 years at the lower education levels, to 5 or more years with no formal education — in each case including 1 year supervising or performing API 510 inspection activities where the table requires it. The eligibility section above gives the full published table.
How often is the exam offered? In windows across the year — three windows a year on the published pattern. The current cycle covers the September 2026, January 2027, and May 2027 windows; the September 2026 window has run. Confirm the current window dates and application deadlines at api.org when you apply.
What does the exam cost? Confirm the current fee on API’s ICP Schedules & Fees page at api.org when you apply — fees are confirmed there at application time, and this guide prints no fee figure.
What happens if I do not pass? Your score report — emailed by Prometric within 24 hours — shows your converted scaled score, so you can see the distance from the passing standard. API will not disclose or return the contents of a failed examination. An application is valid for 6 months from the first exam date requested; sitting again outside that validity requires a new application.
How do I keep the credential once I earn it? Recertify every 3 years in the ICP Portal: show the published work requirement and 24 continuing professional development hours across at least two activity categories per cycle, and pass the online open-book web quiz on code changes every 6 years. The recertification section above gives the full published terms.
Are these the real exam questions? No. Every question in the companion program is an original PassProfessor practice question written to API’s published Body of Knowledge. API does not release its examination questions, and no provider can offer them.
Does the practice match the real exam’s format exactly? No, and this guide does not claim that it does. Practice items are single-answer, four-option questions in a single sitting; the real examination also includes Alternative Item Types being introduced gradually, and splits into closed-book and open-book parts in Prometric’s provided-PDF environment.
When will enrollment open? The program is in the works. Join the notify list on this page and we will email you when enrollment opens.
Disclaimer
PassProfessor is an independent exam-preparation provider; this program is not endorsed by, affiliated with, or sponsored by the American Petroleum Institute (API). API 510 is a certification program of the American Petroleum Institute. This program is examination preparation only: the details on this page are drawn from the official sources recorded in this guide’s internal sources section and are current as of November 2026; API’s official publications govern if anything here differs from them. The credential is awarded by API alone when its requirements are complete; this program confers no credential.