Part of the expanding PassProfessor catalog: the API 653 Aboveground Storage Tank Inspector examination is API’s aboveground storage tank credential — 170 questions in a 7.5-hour day at a Prometric test center, split between a closed-book part and an open-book part, passed at a scaled score of 400 on the published 200 to 500 scale. PassProfessor’s API 653 program is in the works, built to the effectivity pins for the March 2027 to November 2027 cycle.
The API 653 credential is the tank inspector’s authorization: it certifies that an inspector can inspect, repair, alter, and reconstruct aboveground storage tanks under the API 653 standard and the publications API pins to the examination. PassProfessor’s API 653 program is in the works as part of the expanding PassProfessor catalog, built on API’s published Body of Knowledge and Publications Effectivity Sheet for the March 2027, July 2027, and November 2027 examinations, and organized around what that Body of Knowledge tests — tank integrity calculations, welding and examination review, damage mechanisms, cathodic protection and linings, foundations and settlement, and the standard itself.
Which examination is this?
This page covers one credential only: the API 653 Aboveground Storage Tank Inspector certification, administered by the American Petroleum Institute (API) through its Individual Certification Programs (ICP). It is not preparation for API 510 (pressure vessels) or API 570 (piping): each API program has its own Body of Knowledge and pinned editions, stated here and in the companion guide, and this program’s library is the tank library — the construction standard, tank inspection practices, and cathodic protection and lining practices the other two programs do not carry. It is built to the 2027 cycle only: the pinned editions below govern the March, July, and November 2027 sittings, not the November 2026 sitting, which tests to the prior cycle’s pins.
What will the program cover?
1,500 original practice questions. The program holds 1,500 original practice questions across the nine areas of the blueprint below, written from scratch against API’s published Body of Knowledge and effectivity sheet. None is an actual examination item, a recalled item, or another provider’s material, and no question asks you to recite a clause, paragraph, or table number: the practice tests applying the pinned publications to inspection data, records, and situations.
An explanation for every question. Every practice question carries an explanation — an explanation for every question in the bank — so a miss teaches the rule, the computation, or the record feature behind the answer.
Results you can read by area. Practice is organized by the blueprint’s areas, so a thin area shows while there is still time to repair it, instead of hiding inside an overall score.
Timed practice at the real sitting’s shape. Sustained timed practice modelled on the real sitting trains pacing.
One disclosure belongs at the front: API publishes no weighting for this examination. The nine areas below and their counts are a PassProfessor allocation — never API’s weighting.
What are the verified facts of the real exam?
| Fact of record | Detail |
|---|---|
| Credential | API 653 Aboveground Storage Tank 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. 110 closed-book questions and 60 open-book questions |
| The exam day | 7.5 hours in total: a short tutorial, 165 minutes closed-book, a 45-minute lunch break, and 225 minutes open-book — 390 minutes of testing time |
| Delivery | Computer-based at Prometric test centers, in person only. API states expressly that this 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 effectivity sheet’s sections |
| 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. Reports show the scaled score, not the number answered correctly |
| Eligibility | Education plus tank experience acquired within the last 10 years, documented and verified by API — see the eligibility section below. No training course is required |
| Current cycle | Body of Knowledge and effectivity sheet for the March 2027, July 2027, and November 2027 examinations. Confirm window dates and all fees at api.org |
| 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; the candidate books a Prometric seat in 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 — see below |
How does the practice map to the Body of Knowledge?
API’s Body of Knowledge has five sections: calculations and tabular evaluations for thickness measurements, weld sizes, and tank integrity; welding on atmospheric tanks; nondestructive examination; practical knowledge — general; and practical knowledge — specific.
| Practice area | Practice questions |
|---|---|
| Thickness, Intervals and Tank Integrity Calculations | 320 |
| API 653 Inspection, Repair, Alteration and Reconstruction | 240 |
| Nondestructive Examination | 170 |
| Welding Procedure and Qualification Evaluation | 150 |
| Damage Mechanisms (API RP 571) | 140 |
| Inspection Practices and Pressure/Vacuum Relief | 140 |
| Foundations, Settlement and Practical Knowledge | 140 |
| Cathodic Protection and Tank Bottom Linings | 110 |
| Welding Processes and Metallurgy (API RP 577) | 90 |
| Total | 1,500 |
What do the thickness, interval, and tank integrity calculations cover?
The computational core: corrosion rates, remaining life, remaining allowance, and inspection intervals; joint efficiencies, read from joint types and radiography extent; maximum fill height; existing and reconstructed shell minimum thickness; corroded-area and pitting evaluation; bottom plate minimum remaining thickness and operating period, and settlement calculations; and weld sizes for openings, hot tap spacing, and patch plates. Questions are oriented to existing tanks, in both unit systems — and the current Body of Knowledge expects some table values to be answered closed-book, from the starred tables. The Body of Knowledge fences whole families out — venting, structural, and cathodic-protection design calculations among them — and the practice stays inside the same boundary.
Remaining life is the hinge number: most interval and repair decisions turn on computing it correctly.
What does the API 653 standard area cover?
The standard itself, applied: how inspection is organized and its types and planning; external and internal inspection, intervals, and suitability for service; repairs and alterations across foundations, shell, bottoms, nozzles, roofs, seals, and hot taps; reconstruction, change of service, nameplate, and record requirements; hydrostatic, leak, and pneumatic testing; and the API 650 construction knowledge an inspector of existing tanks must command.
A tank is judged as a system: shell, bottom, and settlement findings on the same tank change each other’s meaning.
What does nondestructive examination cover?
The methods the pinned Section V articles govern for this program: the general requirements article; radiographic examination as applied to tank butt welds; liquid penetrant examination, including its mandatory appendix named for this program; magnetic particle examination, limited to yoke and prod techniques with two named paragraphs excluded; ultrasonic thickness measurement; and the general requirements in API 650 and API 653. This program’s article set is its own — no visual-examination article and no leak-testing article — and the practice follows it exactly.
Match the method to the discontinuity and the material: a sound method for the wrong condition is the distractor.
What does welding procedure and qualification evaluation cover?
Reading welding records as an inspector reviews them before a repair is approved — under this program’s deliberately narrow limits: the two processes the Body of Knowledge names for record review, one base-metal group, one process per record set, and no heat-treatment requirements on any examination record. Alongside sit the essential and nonessential variables, the mechanical tests a qualification requires, and the general welding requirements in API 650 and API 653.
A record can be complete, signed, and still wrong: the deciding feature is usually a variable that outruns its supporting qualification.
What do damage mechanisms cover?
API RP 571 as the effectivity sheet pins it for this program: the terms and definitions section, and ten named mechanisms only — atmospheric corrosion; brittle fracture; caustic corrosion; caustic stress corrosion cracking; concentration cell corrosion; corrosion under insulation; ethanol stress corrosion cracking; microbiologically influenced corrosion; soil corrosion; and sulfuric acid corrosion. This list is this program’s own, and it changed recently: mechanisms study lists still teach for this examination — chloride stress corrosion cracking, mechanical fatigue, and sour water corrosion among them — are not on the current list, while concentration cell corrosion and ethanol stress corrosion cracking are pinned here and on neither neighbouring program’s list.
Mechanism items turn on the combination: material, environment, temperature, and stress together.
What do inspection practices and pressure/vacuum relief cover?
API RP 575, inspection practices for atmospheric and low-pressure storage tanks, across the whole document; and weight-loaded pressure and vacuum vents on tanks, in the two pinned sections of API RP 576 only — how tanks and their venting devices are examined in the field.
A tank’s vent is part of its integrity case, not an accessory: vent findings carry shell-finding weight.
What do foundations, settlement, and practical knowledge cover?
The ground and the structure together: tank foundations, distortions, and settlement evaluation in practice; materials, fabrication problems, and brittle fracture risk; roofs, seals, appurtenances, and auxiliary equipment evaluation; and inspection safety, tools, leak checks, and causes of deterioration.
Settlement is read as a pattern, not a number: where the tank has moved decides its meaning.
What do cathodic protection and tank bottom linings cover?
API RP 651, cathodic protection of aboveground petroleum storage tanks, in its pinned sections only — the design of cathodic protection systems and interference-current content are expressly outside this examination — and API RP 652, lining of aboveground tank bottoms, across the whole document.
Soil-side corrosion is the failure the inspector cannot see directly: this area tests the evidence that stands in for sight.
What do welding processes and metallurgy cover?
API RP 577, welding processes, inspection, and metallurgy, across the whole document as pinned for the current cycle, including its errata — and the supporting knowledge around it: filler metal selection, terminology, symbols, and radiographic reporting.
Process knowledge is what lets an inspector read a weld.
How is API 653 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 653 examination is 400. A scaled score is not a percentage, and API publishes no percentage pass mark, no raw pass mark, and no number-correct threshold. API’s equating process adjusts for form difficulty, so the number of correct answers corresponding to 400 may differ slightly between forms.
Who can take this exam, and what does it certify?
Qualification combines education with experience related to aboveground storage tanks, acquired within the last 10 years while employed by, or under contract with, an authorized inspection agency as defined in API 653; 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 API 653 inspection activity. 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, construction, repair, operation, or inspection of aboveground storage tanks, including 1 inspection year. A high school diploma requires 3 years on the same terms; with no formal education, 5 or more years, including the same inspection year. No training course is required, and API does not endorse test-preparation classes. The credential is awarded by API alone; PassProfessor does not certify inspectors and does not enrol candidates for the official examination.
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 aboveground storage tank inspection activities as described in API 653 (inspectors not actively engaged must take the full examination again); and continuing professional development — 24 CPD hours per cycle, relevant to inspection and mechanical integrity, across at least two activity categories, with proof uploaded to the Portal. Every 6 years the inspector must also pass an online, open-book web quiz on code changes: 25 questions in 4 hours, which may be paused up to three times, available from 90 days before expiry through a 90-day grace period after it. Recertification is applied for online in the ICP Portal in the same window.
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 — including, under the current Body of Knowledge, values from the starred tables — then 60 open-book questions test how well the same inspector can find and apply detailed information under time pressure, in a provided-PDF environment. Second, the calculation load: corrosion rates, remaining life, shell and bottom evaluations, fill height, and settlement are worked, not recalled, in both unit systems. Third, the breadth of the pinned library — two API standards, five recommended practices, and two ASME documents — each included only to a stated depth, several carrying no counterpart in the other API programs.
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, the sitting splits into two parts, and the open-book part runs in Prometric’s provided-PDF environment, which practice here does not reproduce. Practice builds the knowledge and calculation skills the Body of Knowledge requires; it does not reproduce the examination’s delivery. Practice results are a study gauge.
How should you use this page while the program is in the works?
- Join the notify list today. Enrollment is not open yet, and the notify list is how you hear the moment it is. While you wait, read the exam guide — it walks the Body of Knowledge area by area and sets out the pinned editions in full.
- Confirm your eligibility window now. The table above decides who may sit; check your documented experience against it early.
- When the program opens, survey every area first. Early practice should touch each area, so your first picture of yourself is honest.
- Drill the area that costs you. Let results, not preferences, set the next block of study.
- Finish with timed, mixed practice. Sit full timed practice at the real sitting’s pace, in both styles.
Frequently asked questions
How many questions are on the API 653 exam, and how long is it? 170 questions in a 7.5-hour day: 140 scored and 30 unidentified pretest questions, split into 110 closed-book questions in 165 minutes and 60 open-book questions in 225 minutes, with a 45-minute lunch break.
What score passes the API 653 exam? A scaled score of 400 on Prometric’s 200 to 500 scale, as API publishes it. A scaled score is not a percentage; API publishes no percentage pass mark and no number-correct threshold.
Can I take the API 653 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. During the open-book part only, PDF documents of the pertinent codes and standards are provided on the exam computer, limited to the effectivity sheet’s sections.
Which editions does the current exam test? The editions pinned on the effectivity sheet for the March 2027 to November 2027 cycle — including API Standard 650, 14th Edition, and the ASME BPVC 2025 Edition. Those pins govern the 2027 sittings; the November 2026 sitting tests to the prior cycle’s pins.
Does API publish how the exam is weighted by topic? No. API publishes no weighting, percentage, or per-topic question count. The area counts on this page are a PassProfessor allocation of the practice bank — they are not API’s weighting.
What experience do I need to qualify? Education plus tank experience acquired within the last 10 years with an authorized inspection agency, documented and verified by API: from 1 year with an engineering or technology degree, up to 5 or more years with no formal education.
Are these the real exam questions? No. Every question in the program is an original PassProfessor practice question written to API’s published Body of Knowledge.
Does the practice match the real exam’s format exactly? No, and this page 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 added gradually, and splits into two parts in Prometric’s PDF environment.
What does the exam cost? Confirm the current fee on API’s ICP Schedules & Fees page at api.org when you apply.
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). This program is examination preparation only: the details on this page are drawn from the official sources recorded in the companion guide 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; this program confers no credential.