200+ Free API 510 Practice Questions

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Question 1

Score: 0/0

A pressure vessel TML measured 0.625 in. four years ago now reads 0.565 in. after 4 years in service. What corrosion rate should the inspector use from these data?

0.015 in./year

0.24 in./year

-0.015 in./year

0.141 in./year

to track

2026 Statistics

Key Facts: API 510 Exam

170

Total Questions

140 scored + 30 pretest

110 / 60

Closed / Open Book

API 510 exam page

550 / 750

Scaled Passing Score

API 510 exam page

$875 / $1,125

2026 Exam Fee

API schedules & fees

1-5+ years

Experience Pathways

Depends on education

3 years

Certification Term

API recertification cycle

As of March 12, 2026, API's current API 510 cycle still uses the September 5, 2025 Body of Knowledge and Publications Effectivity Sheet for the September 2025, January 2026, and May 2026 exam windows. The exam remains a 170-question in-person CBT with 110 closed-book questions, 60 open-book questions, and a 550-out-of-750 scaled passing score. API's current schedules-and-fees page lists 2026 pricing at $875 for API members and $1,125 for nonmembers. API publishes the official domains through the BOK, but it does not publish a public percentage-by-domain blueprint, so the percentages below are practice-weighted estimates based on the current BOK emphasis.

Sample API 510 Practice Questions

Try these sample questions to test your API 510 exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 200+ question experience with AI tutoring.

1A pressure vessel TML measured 0.625 in. four years ago now reads 0.565 in. after 4 years in service. What corrosion rate should the inspector use from these data?

A.0.015 in./year

B.0.24 in./year

C.-0.015 in./year

D.0.141 in./year

Explanation: Corrosion rate is thickness loss divided by elapsed time. The loss here is 0.06 in., so 0.06 / 4 = 0.015 in./year. A common error is multiplying by years or using the current thickness itself instead of the metal lost.

2A vessel shell TML measured 0.750 in. at the previous inspection and 0.690 in. 6 years later. If the required thickness is 0.510 in., what is the remaining life based on the measured corrosion rate?

A.9 years

B.18 years

C.24 years

D.1.1 years

Explanation: First calculate the corrosion rate from the two readings: (0.750 - 0.690) / 6 = 0.01 in./year. Remaining life is then (t_actual - t_required) / corrosion rate = (0.690 - 0.510) / 0.01 = 18 years. API 510-style questions often test whether you separate corrosion-rate and remaining-life calculations instead of jumping straight to an interval answer.

3When selecting thickness measurement locations on a vessel, which area normally deserves special attention because corrosion can accelerate there?

A.A uniformly dry area well above the normal liquid level

B.The shell area near a liquid-vapor interface or known water draw-off zone

C.A randomly chosen point on each shell course only

D.The nameplate bracket because it is always the thinnest section

Explanation: Inspectors place TMLs where corrosion is expected to be greatest, not where access is merely easiest. Liquid-vapor interfaces, water accumulation zones, injection or impingement areas, and other process-specific hotspots are higher-value locations than random shell points.

4Which statement best describes when an on-stream inspection may be used instead of an internal inspection?

A.Whenever the vessel contains a hazardous process fluid

B.Only when the vessel has never been repaired

C.When the vessel’s condition and service allow the inspector to evaluate integrity adequately without opening it

D.Only when the owner wants to avoid downtime regardless of risk

Explanation: API 510 allows on-stream inspection only when the vessel condition, service, and inspection methods provide enough information to judge continued integrity without entering the vessel. It is not an automatic downtime-saving substitute, and the inspector still needs enough data to make a technically sound decision.

5Which change is most likely to be classified as an alteration rather than a repair under API 510?

A.Replacing a gasket with the same specification

B.Installing a new nozzle that changes the pressure-containing configuration

C.Grinding and blending a minor surface indication without changing design

D.Repacking an existing valve

Explanation: An alteration changes the pressure-containing boundary or otherwise affects design details beyond simple restoration in kind. Adding a new nozzle changes the vessel configuration and usually requires design review and code-based evaluation, while the other choices are routine maintenance or repair activities.

6A vessel will be pressure tested at 325 psi, but the installed pressure-relief device is set at 250 psi. What is the normal inspection concern before the test starts?

A.Increase the PRD set pressure permanently to match the test pressure

B.Leave the PRD untouched because spring valves automatically reseat after a hydrotest

C.Protect or remove the PRD so the test does not lift it unintentionally

D.Disable all vents so the vessel reaches pressure faster

Explanation: If test pressure exceeds the relief-device setting, the valve may lift during the test unless it is protected appropriately. Inspectors want the device removed, blinded, or otherwise safeguarded according to the approved test plan, not permanently reset. A hydrotest is not a reason to casually change overpressure protection settings.

7For an existing cylindrical shell under internal pressure, use t = PR / (SE - 0.6P). If P = 285 psi, inside radius R = 24 in., allowable stress S = 20000 psi, and joint efficiency E = 0.85, what required thickness is indicated before adding any corrosion allowance?

A.0.406 in.

B.0.402 in.

C.0.398 in.

D.0.413 in.

Explanation: Using the provided internal-pressure shell formula, the denominator is SE - 0.6P = 17000 - 171 = 16829. Required thickness is therefore (285 × 24) / 16829 = 0.406 in. API 510 calculation questions usually reward plugging the values into the correct existing-vessel formula and then handling corrosion allowance separately.

8Use the cylindrical-shell MAWP form P = SEt / (R + 0.6t). If allowable stress S = 20000 psi, joint efficiency E = 0.85, measured thickness t = 0.520 in., and inside radius R = 24 in., what MAWP is indicated before subtracting future corrosion?

A.363.6 psi

B.368.3 psi

C.776.5 psi

D.427.8 psi

Explanation: Substitute directly into the stated MAWP formula for a cylindrical shell. The numerator is SEt = 8840, and the denominator is R + 0.6t = 24.312. That gives 363.6 psi. The wrong choices reflect common mistakes such as dropping joint efficiency or ignoring the 0.6t term.

9A site falls under a jurisdiction that has adopted pressure-equipment rules different from the owner-user’s internal practice. For inspection compliance, what should the inspector recognize first?

A.The owner-user rules always override local requirements

B.The governing jurisdiction can control the applicable requirements for the vessel

C.API 510 automatically cancels all jurisdictional authority

D.Only ASME Section VIII matters once the vessel is in service

Explanation: API 510 is often used within owner-user programs, but jurisdictional requirements can still govern inspection, repair, or operational decisions. A competent inspector first determines what legal or regulatory authority applies before assuming an internal practice controls.

10A vessel shell TML measured 0.580 in. at the previous inspection and 0.540 in. 5 years later. If the required thickness is 0.420 in., what is the remaining life based on the measured corrosion rate?

A.7.5 years

B.15 years

C.20 years

D.0.6 years

Explanation: First calculate the corrosion rate from the two readings: (0.580 - 0.540) / 5 = 0.008 in./year. Remaining life is then (t_actual - t_required) / corrosion rate = (0.540 - 0.420) / 0.008 = 15 years. API 510-style questions often test whether you separate corrosion-rate and remaining-life calculations instead of jumping straight to an interval answer.

About the API 510 Exam

API 510 is the flagship API Individual Certification Program for pressure vessel inspectors working with in-service fixed equipment. The exam tests inspection planning, corrosion and damage assessment, ASME/API code application, repairs and rerating, pressure testing, and fitness-for-service judgment for pressure vessels in refining and petrochemical service.

Assessment

170 multiple-choice questions: 110 closed-book + 60 open-book (140 scored + 30 pretest)

Time Limit

7.5-hour exam day (2.75 hours closed-book, 45-minute lunch, 3.75 hours open-book)

Passing Score

550 scaled score out of 750

Exam Fee

$875 API member / $1,125 nonmember (American Petroleum Institute (API) / Prometric)

API 510 Exam Content Outline

28% practice weight

Inspection Scope, Planning, and Data Evaluation

Code scope, jurisdiction, records review, TML/CML selection, interval setting, remaining-life calculations, on-stream/nonintrusive inspection, and choosing appropriate examination methods.

22% practice weight

Damage Mechanisms and Corrosion Assessment

Internal, external, and localized corrosion; CUI; high-temperature damage; cracking mechanisms from API RP 571; and interpreting deterioration patterns to plan inspection or mitigation.

22% practice weight

Design, Materials, and Fabrication Rules

MAWP and required-thickness calculations, joint efficiency, materials and toughness, PMI, welding/PWHT rules, flanges and bolting, linings, refractory, and key ASME Section VIII/IX concepts used in API 510 work.

16% practice weight

Repairs, Alterations, Rerating, and Mechanical Integrity

Who can authorize work, repair organization responsibilities, alteration versus repair decisions, rerating steps, nameplate/document updates, pressure-relieving-device considerations, and post-work documentation.

12% practice weight

Fitness-for-Service, RBI, and Pressure Testing

Using API 579-1/ASME FFS-1 concepts at the screening level, understanding when RBI can justify interval changes, and applying pressure or leak-test rules after repair or alteration.

How to Pass the API 510 Exam

What You Need to Know

Passing score: 550 scaled score out of 750
Assessment: 170 multiple-choice questions: 110 closed-book + 60 open-book (140 scored + 30 pretest)
Time limit: 7.5-hour exam day (2.75 hours closed-book, 45-minute lunch, 3.75 hours open-book)
Exam fee: $875 API member / $1,125 nonmember

Keys to Passing

Complete 500+ practice questions
Score 80%+ consistently before scheduling
Focus on highest-weighted sections
Use our AI tutor for tough concepts

API 510 Study Tips from Top Performers

1Memorize the interval, corrosion-rate, remaining-life, and required-thickness formulas well enough to work them closed-book under time pressure.

2Study the current effectivity sheet alongside the BOK so you know which references and sections are actually testable in the open-book portion.

3Build strong damage-mechanism recognition from API RP 571, especially corrosion under insulation, brittle fracture risk factors, high-temperature damage, and service-specific cracking mechanisms.

4Practice deciding whether a situation is a repair, an alteration, or a rerating because many API 510 questions hinge on that first classification step.

5Get comfortable navigating ASME Section VIII Division 1 for joint efficiency, required thickness, openings, and external-pressure logic without reading entire chapters during the exam.

6Do not treat open-book time as easy time. Speed comes from knowing where rules live before test day, not from searching cold under exam conditions.

7Review pressure-relieving-device responsibilities, documentation, and post-repair test decisions because these questions often blend API 510 judgment with repair and rerating scenarios.

8Use mixed sets after each study block so you can shift quickly from corrosion mechanisms to calculations to administrative code decisions the way the real exam does.

Frequently Asked Questions

How many questions are on the API 510 exam?

API states that the API 510 exam contains 170 multiple-choice questions, but only 140 are scored. The remaining 30 are pretest items that do not count toward your result. The exam is split into 110 closed-book questions and 60 open-book questions.

How long is the API 510 exam?

The official API 510 exam day is 7.5 hours long. API breaks that into a short tutorial, 2.75 hours for the closed-book portion, a 45-minute lunch break, and 3.75 hours for the open-book portion.

What score do I need to pass API 510?

API reports API 510 results on a 200 to 750 scaled-score scale, and 550 is the minimum passing score. Because the score is scaled, you should not think of it as a simple raw-percent cutoff. The safest prep target is to be consistently strong across inspection planning, corrosion, code calculations, and repair/rerating questions rather than chasing a guessed raw percentage.

What references are current for API 510 in 2026?

As of March 12, 2026, the current API 510 exam cycle still uses the September 2025 to May 2026 effectivity sheet. Core references include API 510 11th Edition, API RP 571 3rd Edition, API RP 572 4th Edition, API RP 576, API RP 577, API RP 578, ASME Section V, ASME Section VIII Division 1, ASME Section IX, and ASME PCC-2 in the sections listed on the official effectivity sheet.

Does API publish official domain percentages for API 510?

Not publicly. API publishes the official Body of Knowledge topics and the closed-book versus open-book split, but it does not publish a public percentage weighting for each knowledge domain the way some other exam bodies do. For study planning, use the current BOK to prioritize interval calculations, corrosion and damage mechanisms, code rules, and repair/rerating judgment.

Is remote testing available for API 510 in 2026?

No. API's program-updates page states that remote testing for core programs including API 510 was discontinued in September 2024, and the current API 510 exam page describes testing in Prometric computer testing centers. For current administrations, plan on an in-person exam.

What experience do I need to sit for API 510?

API uses education-and-experience pathways. Candidates with a BS or higher in engineering or technology, or 3+ years of military technical service, need 1 year of qualifying pressure-vessel inspection experience. Associate-degree or certificate pathways require 2 years, high school requires 3 years, and candidates with no formal education need 5 or more years, with at least 1 year involving supervision or performance of API 510-type inspection activities.