This 2026 question bank prepares candidates for the API 653 Aboveground Storage Tank (AST) Inspector certification. Questions reference API 653 Tank Inspection, Repair, Alteration, and Reconstruction, API 650 Welded Tanks for Oil Storage, API RP 575 Inspection Practices for AST, API RP 577 Welding, API 571 Damage Mechanisms, API RP 651 Cathodic Protection, API RP 652 Linings for Tank Bottoms, and ASME BPVC V and IX.
\nFrom the API 653 program page on api.org (check it before you book; details change by exam window):
\nCorrect Answer: A
Explanation: API 653 (6.3.2.1) requires a visual external inspection by an authorized inspector at least every 5 years or RCA/4N years, whichever is less (RCA = remaining corrosion allowance of the shell, N = shell corrosion rate). Owner personnel also perform routine in-service inspections at intervals not exceeding one month.
Correct Answer: A
Explanation: API 653 (6.4) sets the first internal inspection at no more than 10 years after service begins, unless the safeguards in Table 6.1 (linings, cathodic protection, release prevention barrier, etc.) add credits, capped at 20 years without an RPB or 30 years with one. Subsequent intervals are calculated from bottom corrosion rates against the Table 4.4 minimum thickness, or set by an RBI assessment meeting the code's requirements; check the current edition (5th ed. with Addendum 4, 2025) for the limits that apply.
Correct Answer: A
Explanation: The product side and the underside both corrode, but underside (soil-side) corrosion is often the limiting factor for tank life. API RP 651 (cathodic protection) and API RP 652 (internal linings) are commonly applied to extend bottom life.
Correct Answer: A
Explanation: API 653 Section 4.4 sets minimum bottom plate thickness based on calculated corrosion rate, projected service interval, and whether the underside has release prevention barrier (RPB), cathodic protection, or lining. Table 4.4 minimums at the next inspection are 2.5 mm (0.10 in.) with no means to detect and contain a bottom leak, and 1.27 mm (0.05 in.) with such a means or with a reinforced lining over 0.05 in. per API RP 652.
Correct Answer: A
Explanation: API 653 Annex B provides methods to evaluate settlement: uniform (no shell distress), planar tilt (allowable based on H/D), edge settlement (between shell and bottom), out-of-plane (Fourier analysis to evaluate bending stresses).
Correct Answer: A
Explanation: API 653 uses the same 1-foot method (Eq. 4-1) and variable-design-point method (Section 4.3.3.2) as API 650 for required shell thickness, applied with measured thickness less FCA to determine fitness for continued service.
Correct Answer: A
Explanation: Floating roof external inspection per API 653 includes seals (primary, secondary), pontoon compartments (must be inspected internally), deck plates, drain hoses, anti-rotation devices, and emergency overflow drains. Pontoon flooding causes catastrophic sinking events.
Correct Answer: A
Explanation: A major alteration (e.g., shell height change, new nozzles in stressed areas, foundation rework) requires engineering review per API 653 Section 9, qualified procedures and welders per ASME IX, NDT per API 650 acceptance criteria, and hydrotest per Section 12.
Correct Answer: A
Explanation: MFL scanners cover large areas of tank floor rapidly during internal inspection, detecting product-side and underside metal loss. Suspect areas are then confirmed with UT prove-up. API 653 (4.4.4) notes that MFL is commonly used with UT confirmation, and Annex G can be used to qualify the examiners and procedures; reporting thresholds are set in the qualified procedure, not by a fixed percentage in the code.
Correct Answer: A
Explanation: ASTs are tested by filling with water to the maximum operating liquid level (or the design liquid level for new tanks). API 650 paragraph 7.3.6 provides hydrotest procedures. There is no pressure multiplier; full-head water test demonstrates the static-only loading.
Correct Answer: A
Explanation: Authorized inspectors are certified under the API ICP program, which requires education plus tank-related experience (e.g., BS + 1 year, 2-year degree + 2 years, high school + 3 years, no formal education + 5 years, each including 1 year in supervision or performance of inspection).
Correct Answer: A
Explanation: Bottom plate repairs include patch plates (lap-welded or butt-welded), overlay (build-up), or full plate replacement. API 653 Section 9 specifies size limits, weld details, and NDT (typically vacuum box testing on bottom welds).
Correct Answer: A
Explanation: API 650 Section 7.3.4 specifies the vacuum box method: apply soap solution, place box over weld, draw a partial vacuum (API 650 specifies about 3 to 5 psi / 21 to 35 kPa gauge; check the edition on the effectivity sheet). Bubble formation indicates a through-weld leak. Standard for tank bottom welds.
Correct Answer: A
Explanation: Temporary repairs (e.g., clamps, doublers) are allowed under API 653 with engineering review and a documented timeline for permanent repair, typically by the next turnaround.
Correct Answer: A
Explanation: Underside CP uses either sacrificial anodes (typically Mg or Zn) for small tanks or impressed current systems for larger tanks. Effectiveness measured at −850 mV (Cu/CuSO4 reference) per NACE SP0169 and API RP 651.
Correct Answer: A
Explanation: API 653 (6.3.3) sets the shell UT interval at a maximum of 5 years when the corrosion rate is not known; when it is known, the maximum is the lesser of RCA/2N years or 15 years. External UT can be done while the tank is in service.
Correct Answer: A
Explanation: Edge settlement (sometimes called dish-out) creates bending of the bottom plates near the shell, generating high secondary stresses at the chime weld. API 653 Annex B provides evaluation criteria based on length and depth.
Correct Answer: A
Explanation: Fixed cone/dome roof internals: rafters, columns (lateral movement and base plates), top angle, deck plates (corrosion from acidic vapor space), and overflow/vent screens. RP 575 details fixed roof inspection.
Correct Answer: A
Explanation: Per API 650 Section 10, the nameplate identifies manufacturer, year built, design code edition, capacity, maximum operating liquid level, design metal temperature, specific gravity, and the API monogram. Original nameplates must be preserved on reconstruction.
Correct Answer: A
Explanation: Idle tanks may suffer from internal humidity corrosion, settlement, foundation issues, biological growth. API 653 requires a re-commissioning condition assessment per Section 6 prior to return to service.
Correct Answer: A
Explanation: RPB systems (e.g., HDPE liner, concrete pad with leak detection grooves) detect underside leaks and prevent soil/groundwater contamination. API 650 Annex I describes RPB designs; some jurisdictions and owner specifications require them, and API 653 gives internal-inspection interval credit for them.
Correct Answer: A
Explanation: Tank shell roundness is measured externally with optical or laser methods. Out-of-roundness beyond API 653 limits indicates uneven foundation settlement, wind buckling, vacuum collapse, or installation defects requiring engineering review.
Correct Answer: A
Explanation: External atmospheric corrosion accelerates in industrial atmospheres (SO2, NOx), coastal (chlorides), wet/dry cycles, and where paint has failed. Recoating intervals depend on environment severity. API RP 652 covers lining; API 575 covers coating inspection.
Correct Answer: A
Explanation: Nozzle reinforcement is calculated per API 650 Section 5.7.5 using area replacement rules. Reinforcement plates compensate for removed shell material. Low-type and regular-type nozzle details have prescribed reinforcement.
Correct Answer: A
Explanation: API 653 Section 12 specifies when hydrotest is mandatory after repair/alteration. Generally, replacement of significant shell plate areas, raising tank height, or modifying nozzles in critical zones requires hydrotest. Vacuum box testing is acceptable for bottom-only repairs.
Correct Answer: A
Explanation: Double bottom retrofit places a new bottom above the existing bottom with a small annular space (often filled with sand or instrumented for leak detection). This reduces downtime vs full bottom replacement. Engineering review for height/structural impact required.
Correct Answer: A
Explanation: Tank inspection NDT: VT (mandatory), UT thickness on shell/roof, MFL on floor, PT/MT on critical welds, vacuum box on bottom and annular welds, RT on shell butt welds. PEC for through-coating screening. Settlement survey by total station/laser.
Correct Answer: A
Explanation: Standard weld repair sequence per ASME IX and API 650/653: excavate defect (grinding or arc gouging), NDT to confirm full removal (typically MT or PT), weld per qualified WPS, post-repair NDT (VT plus MT/PT/RT/UT as specified).
Correct Answer: A
Explanation: Annular plates (the ring of thicker bottom plates beneath the shell) carry high stress from shell. API 653 sets annular plate minimum thickness at the next inspection from a table based on the first shell course thickness and its hydrotest/product stress, with an absolute floor of 0.10 in. (2.5 mm); check the current edition for the table values.
Correct Answer: A
Explanation: API 653 reporting and recordkeeping requirements (inspection reports in section 6 and records in section 13) cover: tank ID and history, measured thicknesses, settlement data, NDT records, deficiencies and recommendations, calculations, photos, and the certified inspector’s signature.
A: BS + 1 year, 2-year degree + 2 years, high school + 3 years, or no formal education + 5 years of tank-related experience, each including 1 year in supervision or performance of inspection. No NDT certification is required. Verify current API ICP requirements.
\nA: 510 = pressure vessels, 570 = piping, 653 = aboveground storage tanks. Stacking all three is common for refinery and terminal inspectors.
\nA: API 653 applies to API 650 / API 12 series welded storage tanks. Riveted tanks and bolted tanks have specific provisions; underground tanks are not in scope (governed by other codes).
\nA: First internal inspection within 10 years of service unless Table 6.1 safeguards add credit (capped at 20 years without an RPB, 30 years with one); thereafter based on bottom corrosion rates against the Table 4.4 minimum, or by an RBI assessment meeting API 653's requirements.
\nA: An API licensee monogram (API 650, 12F, 12D, etc.) certifies the tank was built to the applicable API standard by a licensed shop. Reconstruction work may also be monogrammed.
\nA: No. Atlantis NDT does not run API 653 exam-preparation courses. Our API 653 tank inspection support is ASNT Level III technical work on tank programmes, not exam coaching.
\nA: Floating roofs add seals, pontoons, drain hoses, anti-rotation, ladder/stairway, and roof drainage. Cone/dome roofs add rafters, columns, and vent design. Both inspected under API 653 Section 6 and RP 575.
\nA: API publishes exam statistics in its ICP status updates. The April 2024 update reported per-window pass rates for API 510, 570 and 653 ranging from roughly 45% to 72% between 2018 and early 2024, with a scaled pass point of 400. Check the latest API ICP statistics report rather than relying on third-party estimates.
\nA: No — uniform settlement is usually benign. Differential settlement (tilt, edge, out-of-plane) must be evaluated per API 653 Annex B against allowable limits. Engineering review for borderline cases.
\nA: API 653 is for storage tanks. ASME B31.3 covers process piping. API 510 covers pressure vessels (over 15 psig). API 570 covers in-service piping. Many terminal and refinery inspectors hold more than one of the three API inspector certifications.
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