API 653 Aboveground Storage Tank
Inspector Certification Exam Prep Document
2026/2027 | Tank Inspection, Integrity
Management & Industry Codes | 100 Verified
Questions with Detailed Rationales
This exam contains verified questions drawn from actual API 653 certification content, covering
aboveground storage tank inspection, integrity assessment, repair and alteration, and applicable
industry codes. Questions reflect real inspection scenarios, code compliance challenges, and integrity
management decisions encountered by API 653 inspectors in the field.
Content Area Overview
API 653 Standards, Inspection Intervals & Evaluation Criteria – Covers scope of API 653, inspection
frequency requirements, thickness evaluation, settlement evaluation, corrosion rate calculation,
remaining life assessment, minimum acceptable thickness, hydrostatic testing, and fitness-for-service
evaluation.
Tank Integrity, Corrosion Assessment & NDE Methods – Addresses types of corrosion, corrosion rate
determination, corrosion control measures (cathodic protection, coatings, linings), and NDE method
selection (UT, MT, PT, RT, visual inspection, leak testing).
Repair, Alteration & Re-rating Procedures – Focuses on welding procedures and qualification per ASME
Section IX, repair design (bottom plates, shells, nozzles, roofs), re-rating based on reduced thickness,
and documentation requirements for repairs and alterations.
API 650, API 571, ASME & Industry Code Integration – Examines API 650 construction standards, API 571
damage mechanisms, ASME Section VIII and IX requirements, NBIC, and EPA/OSHA regulations
applicable to tank integrity management.
Section 1: API 653 Standards, Inspection Intervals & Evaluation Criteria – Questions 1–25
,Q1: Per API 653, what is the maximum interval for an external visual inspection of an aboveground
storage tank in service?
A. 2 years, regardless of tank condition or RBI assessment
B. 5 years, unless a risk-based inspection (RBI) program per API 580/581 justifies an extension
[CORRECT]
C. 10 years for tanks with cathodic protection systems in place
D. 3 years for all field-erected tanks and 5 years for shop-built tanks
Correct Answer: B
Rationale: The best answer is B. API 653 Section 6 establishes a default 5-year maximum for external
visual inspections, but the standard also recognizes RBI programs compliant with API 580/581 as a valid
basis for adjusting intervals based on probability and consequence of failure. This choice is correct
because it captures both the baseline requirement and the flexibility RBI provides, which is the approach
most facilities are moving toward in 2026.
Q2: A tank inspector is evaluating shell plate thickness data from an internal inspection. The nominal
thickness of the shell course is 0.375 inches, and the minimum required thickness (t_min) per API 653 is
0.218 inches. The current measured thickness at one location is 0.195 inches. What is the status of this
tank?
A. The tank is acceptable for continued service since the measured thickness is within 10% of t_min
B. The tank must be immediately taken out of service and the shell plate replaced
C. The tank is not acceptable for continued service at this location because the measured thickness is
below t_min [CORRECT]
D. The tank may continue in service if the corrosion rate is less than 5 mils per year
Correct Answer: C
Rationale: The best answer is C. API 653 is clear on this — if the measured thickness at any location falls
below the calculated minimum required thickness (t_min), that area is not acceptable for continued
service. This matches the code requirement that t_min represents the absolute floor for structural
integrity, and anything below it triggers repair, replacement, or re-rating. The other options either
misapply the 10% rule (which doesn't exist for this purpose) or confuse corrosion rate with the hard
t_min limit.
,Q3: Which of the following formulas is used to calculate the remaining corrosion allowance for a tank
bottom plate?
A. Remaining life = (Current thickness – t_min) ÷ Corrosion rate
B. Remaining life = (t_min – Current thickness) × Corrosion rate
C. Remaining life = (Current thickness – MRT) ÷ Corrosion rate, where MRT is the minimum remaining
thickness at the next inspection [CORRECT]
D. Remaining life = (Nominal thickness – Current thickness) ÷ Corrosion rate
Correct Answer: C
Rationale: The best answer is C. For tank bottom plates, API 653 Section 4.4.5 uses the minimum
remaining thickness (MRT) at the next inspection as the key threshold, not the general t_min used for
shells. The formula (Current thickness – MRT) ÷ Corrosion rate gives you the time until the bottom
reaches its MRT, which determines when the next internal inspection is due. This is a subtle but
important distinction from shell plate calculations, and it's one that trips up a lot of inspectors on the
exam.
Q4: A 120-foot diameter crude oil storage tank was last inspected internally 8 years ago. The corrosion
rate for the shell was determined to be 3 mils per year, and the remaining life was calculated at 12
years. The tank operates under normal atmospheric conditions with no significant process changes.
When is the next internal inspection due?
A. Immediately, because the interval has already exceeded 5 years
B. In 4 years, because the maximum internal inspection interval is 20 years regardless of remaining life
C. In 12 years, based on the calculated remaining life, but not to exceed 20 years [CORRECT]
D. In 5 years, because API 653 mandates a 5-year internal inspection interval for all tanks
Correct Answer: C
Rationale: The best answer is C. API 653 ties internal inspection intervals to the calculated remaining life
of the tank components, with a hard ceiling of 20 years maximum between internal inspections. Since
the remaining life is 12 years and the tank conditions haven't changed significantly, 12 years is the
appropriate interval — but the inspector must also verify that this doesn't push the total interval beyond
20 years from the last internal inspection. This choice aligns with the code requirement that remaining
life drives the schedule, not arbitrary calendar dates.
, Q5: During an external inspection, an inspector notes measurable settlement at the tank foundation.
Which API document provides the primary methodology for evaluating tank settlement and determining
whether it is acceptable?
A. API 650, Annex E
B. API 653, Section 4.5, and API RP 579-1/ASME FFS-1 for detailed assessment [CORRECT]
C. API 571, Section 3 on mechanical damage mechanisms
D. ASME Section VIII, Division 1, Appendix 2
Correct Answer: B
Rationale: The best answer is B. API 653 Section 4.5 covers settlement evaluation for in-service tanks,
including the criteria for edge settlement, center settlement, and differential settlement around the
circumference. When the settlement exceeds API 653 limits or when a more detailed structural
assessment is needed, API 579-1/ASME FFS-1 provides the fitness-for-service methodology. This is the
standard two-step approach inspectors use in the field — API 653 for the initial screening, and FFS-1
when things get complicated.
Q6: A tank was constructed to API 650 and placed in service in 1995. The owner wants to apply API 653
for inspection and maintenance. What is the correct relationship between these two standards?
A. API 653 supersedes API 650 for all in-service tanks, and API 650 requirements no longer apply
B. API 653 governs inspection, repair, alteration, and reconstruction; API 650 governs original
construction, and API 653 takes precedence where conflicts arise [CORRECT]
C. API 650 governs all aspects of the tank for its entire life, and API 653 is only advisory
D. API 653 applies only to tanks built after 2000; older tanks must follow their original construction
standard
Correct Answer: B
Rationale: The best answer is B. API 653 was specifically written to cover tanks originally constructed
under API 650 (and its predecessor API 12C). The standard explicitly states that API 653 takes
precedence where conflicts exist between the two documents. API 650 remains the reference for
original design and construction, while API 653 governs what happens after the tank goes into service.
This is fundamental knowledge for any inspector — you need to know which standard applies to which
phase of the tank's life.
Inspector Certification Exam Prep Document
2026/2027 | Tank Inspection, Integrity
Management & Industry Codes | 100 Verified
Questions with Detailed Rationales
This exam contains verified questions drawn from actual API 653 certification content, covering
aboveground storage tank inspection, integrity assessment, repair and alteration, and applicable
industry codes. Questions reflect real inspection scenarios, code compliance challenges, and integrity
management decisions encountered by API 653 inspectors in the field.
Content Area Overview
API 653 Standards, Inspection Intervals & Evaluation Criteria – Covers scope of API 653, inspection
frequency requirements, thickness evaluation, settlement evaluation, corrosion rate calculation,
remaining life assessment, minimum acceptable thickness, hydrostatic testing, and fitness-for-service
evaluation.
Tank Integrity, Corrosion Assessment & NDE Methods – Addresses types of corrosion, corrosion rate
determination, corrosion control measures (cathodic protection, coatings, linings), and NDE method
selection (UT, MT, PT, RT, visual inspection, leak testing).
Repair, Alteration & Re-rating Procedures – Focuses on welding procedures and qualification per ASME
Section IX, repair design (bottom plates, shells, nozzles, roofs), re-rating based on reduced thickness,
and documentation requirements for repairs and alterations.
API 650, API 571, ASME & Industry Code Integration – Examines API 650 construction standards, API 571
damage mechanisms, ASME Section VIII and IX requirements, NBIC, and EPA/OSHA regulations
applicable to tank integrity management.
Section 1: API 653 Standards, Inspection Intervals & Evaluation Criteria – Questions 1–25
,Q1: Per API 653, what is the maximum interval for an external visual inspection of an aboveground
storage tank in service?
A. 2 years, regardless of tank condition or RBI assessment
B. 5 years, unless a risk-based inspection (RBI) program per API 580/581 justifies an extension
[CORRECT]
C. 10 years for tanks with cathodic protection systems in place
D. 3 years for all field-erected tanks and 5 years for shop-built tanks
Correct Answer: B
Rationale: The best answer is B. API 653 Section 6 establishes a default 5-year maximum for external
visual inspections, but the standard also recognizes RBI programs compliant with API 580/581 as a valid
basis for adjusting intervals based on probability and consequence of failure. This choice is correct
because it captures both the baseline requirement and the flexibility RBI provides, which is the approach
most facilities are moving toward in 2026.
Q2: A tank inspector is evaluating shell plate thickness data from an internal inspection. The nominal
thickness of the shell course is 0.375 inches, and the minimum required thickness (t_min) per API 653 is
0.218 inches. The current measured thickness at one location is 0.195 inches. What is the status of this
tank?
A. The tank is acceptable for continued service since the measured thickness is within 10% of t_min
B. The tank must be immediately taken out of service and the shell plate replaced
C. The tank is not acceptable for continued service at this location because the measured thickness is
below t_min [CORRECT]
D. The tank may continue in service if the corrosion rate is less than 5 mils per year
Correct Answer: C
Rationale: The best answer is C. API 653 is clear on this — if the measured thickness at any location falls
below the calculated minimum required thickness (t_min), that area is not acceptable for continued
service. This matches the code requirement that t_min represents the absolute floor for structural
integrity, and anything below it triggers repair, replacement, or re-rating. The other options either
misapply the 10% rule (which doesn't exist for this purpose) or confuse corrosion rate with the hard
t_min limit.
,Q3: Which of the following formulas is used to calculate the remaining corrosion allowance for a tank
bottom plate?
A. Remaining life = (Current thickness – t_min) ÷ Corrosion rate
B. Remaining life = (t_min – Current thickness) × Corrosion rate
C. Remaining life = (Current thickness – MRT) ÷ Corrosion rate, where MRT is the minimum remaining
thickness at the next inspection [CORRECT]
D. Remaining life = (Nominal thickness – Current thickness) ÷ Corrosion rate
Correct Answer: C
Rationale: The best answer is C. For tank bottom plates, API 653 Section 4.4.5 uses the minimum
remaining thickness (MRT) at the next inspection as the key threshold, not the general t_min used for
shells. The formula (Current thickness – MRT) ÷ Corrosion rate gives you the time until the bottom
reaches its MRT, which determines when the next internal inspection is due. This is a subtle but
important distinction from shell plate calculations, and it's one that trips up a lot of inspectors on the
exam.
Q4: A 120-foot diameter crude oil storage tank was last inspected internally 8 years ago. The corrosion
rate for the shell was determined to be 3 mils per year, and the remaining life was calculated at 12
years. The tank operates under normal atmospheric conditions with no significant process changes.
When is the next internal inspection due?
A. Immediately, because the interval has already exceeded 5 years
B. In 4 years, because the maximum internal inspection interval is 20 years regardless of remaining life
C. In 12 years, based on the calculated remaining life, but not to exceed 20 years [CORRECT]
D. In 5 years, because API 653 mandates a 5-year internal inspection interval for all tanks
Correct Answer: C
Rationale: The best answer is C. API 653 ties internal inspection intervals to the calculated remaining life
of the tank components, with a hard ceiling of 20 years maximum between internal inspections. Since
the remaining life is 12 years and the tank conditions haven't changed significantly, 12 years is the
appropriate interval — but the inspector must also verify that this doesn't push the total interval beyond
20 years from the last internal inspection. This choice aligns with the code requirement that remaining
life drives the schedule, not arbitrary calendar dates.
, Q5: During an external inspection, an inspector notes measurable settlement at the tank foundation.
Which API document provides the primary methodology for evaluating tank settlement and determining
whether it is acceptable?
A. API 650, Annex E
B. API 653, Section 4.5, and API RP 579-1/ASME FFS-1 for detailed assessment [CORRECT]
C. API 571, Section 3 on mechanical damage mechanisms
D. ASME Section VIII, Division 1, Appendix 2
Correct Answer: B
Rationale: The best answer is B. API 653 Section 4.5 covers settlement evaluation for in-service tanks,
including the criteria for edge settlement, center settlement, and differential settlement around the
circumference. When the settlement exceeds API 653 limits or when a more detailed structural
assessment is needed, API 579-1/ASME FFS-1 provides the fitness-for-service methodology. This is the
standard two-step approach inspectors use in the field — API 653 for the initial screening, and FFS-1
when things get complicated.
Q6: A tank was constructed to API 650 and placed in service in 1995. The owner wants to apply API 653
for inspection and maintenance. What is the correct relationship between these two standards?
A. API 653 supersedes API 650 for all in-service tanks, and API 650 requirements no longer apply
B. API 653 governs inspection, repair, alteration, and reconstruction; API 650 governs original
construction, and API 653 takes precedence where conflicts arise [CORRECT]
C. API 650 governs all aspects of the tank for its entire life, and API 653 is only advisory
D. API 653 applies only to tanks built after 2000; older tanks must follow their original construction
standard
Correct Answer: B
Rationale: The best answer is B. API 653 was specifically written to cover tanks originally constructed
under API 650 (and its predecessor API 12C). The standard explicitly states that API 653 takes
precedence where conflicts exist between the two documents. API 650 remains the reference for
original design and construction, while API 653 governs what happens after the tank goes into service.
This is fundamental knowledge for any inspector — you need to know which standard applies to which
phase of the tank's life.
