API 653 Aboveground Storage Tank
Inspector Examination Questions And
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Question 1
What is the minimum required thickness for a shell course in an aboveground
storage tank constructed to API 653, assuming the tank is in non-refrigerated
service and the minimum design metal temperature is above -20°F?
A) 0.100 inches
B) 0.125 inches
C) 0.1875 inches
D) 0.250 inches
Correct Answer: B) 0.125 inches
Rationale: API 653 Section 4.3.2.1 requires that the minimum shell thickness for
any shell course, excluding corrosion allowance, shall not be less than 0.125
inches for tanks in non-refrigerated service with a minimum design metal
temperature above -20°F. This ensures structural integrity against internal
pressure and external loads.
Question 2
According to API 653, what is the maximum allowable fill height for a tank that has
undergone a settlement evaluation?
A) The original design fill height
B) 90% of the original design fill height
,C) The height determined by the reduced shell thickness and settlement analysis
D) The height specified by the manufacturer
Correct Answer: C) The height determined by the reduced shell thickness and
settlement analysis
Rationale: API 653 Section 4.3.3.1 states that the maximum allowable fill height
must be recalculated based on the measured minimum shell thickness, corrosion
rates, and any settlement that affects the tank's structural stability. The fill
height must not exceed the value that maintains allowable stresses per API 650
design criteria.
Question 3
Which type of weld joint is most commonly used for vertical shell seams in
aboveground storage tanks according to API 653?
A) Lap joint
B) Butt joint with full penetration
C) Corner joint
D) Edge joint
Correct Answer: B) Butt joint with full penetration
Rationale: API 653 references API 650 for welding requirements. Butt joints with
full penetration are standard for vertical shell seams because they provide the
necessary strength, continuity, and resistance to cyclic loading. Lap joints are not
permitted for primary shell seams due to stress concentration concerns.
Question 4
When performing a thickness measurement survey on a tank shell, what is the
minimum number of readings per shell course required by API 653?
A) One reading per shell course
B) Two readings per shell course, 180 degrees apart
C) Four readings per shell course, 90 degrees apart
D) Eight readings per shell course, 45 degrees apart
,Correct Answer: C) Four readings per shell course, 90 degrees apart
Rationale: API 653 Section 4.3.1.1 requires a minimum of four thickness readings
per shell course, uniformly spaced around the circumference at approximately
90-degree intervals. Additional readings are required in areas of suspected
corrosion or pitting.
Question 5
What is the primary purpose of the hydrostatic test required after major repairs to
an aboveground storage tank?
A) To check for leaks only
B) To verify the structural integrity and leak-tightness of the tank
C) To test the foundation stability
D) To calibrate the level gauging system
Correct Answer: B) To verify the structural integrity and leak-tightness of the
tank
Rationale: API 653 Section 12.2.1 mandates hydrostatic testing after major
repairs to confirm that the tank can safely contain the product at design fill
height without leakage or excessive deformation. The test also validates weld
quality and shell stability under operational loads.
Question 6
According to API 653, what is the acceptance criteria for pitting corrosion on the
shell of an aboveground storage tank?
A) Pits deeper than 50% of the nominal thickness are unacceptable
B) Pits that reduce the remaining thickness below the minimum required
thickness are unacceptable
C) All pits must be filled by welding
D) Pits are acceptable if they do not leak during hydrotest
Correct Answer: B) Pits that reduce the remaining thickness below the minimum
required thickness are unacceptable
, Rationale: API 653 Section 4.3.4.1 specifies that pitting is acceptable provided
the remaining thickness in the pit area is at least the minimum required
thickness calculated per the design formulas. Isolated pits may be evaluated
individually, and if they penetrate below the minimum, they must be repaired or
the tank derated.
Question 7
What is the minimum distance from a tank shell to the property line for a new
aboveground storage tank containing flammable liquids?
A) 50 feet
B) 100 feet
C) 150 feet
D) Determined by NFPA 30 and local codes
Correct Answer: D) Determined by NFPA 30 and local codes
Rationale: API 653 does not set property line distances; it references NFPA 30
and applicable local regulations. Typically, distances vary based on tank size,
product type, and fire protection measures. The inspector must be familiar with
these referenced standards.
Question 8
In API 653, what does the term "remaining life" refer to for a tank component?
A) The total age of the tank since construction
B) The estimated time until the component thickness reaches the minimum
required thickness at the current corrosion rate
C) The warranty period provided by the manufacturer
D) The time until the next scheduled inspection
Correct Answer: B) The estimated time until the component thickness reaches
the minimum required thickness at the current corrosion rate
Rationale: API 653 Section 4.3.5 defines remaining life as the calculated time (in
years) based on the measured thickness, minimum required thickness, and
Inspector Examination Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A Instant Download
Question 1
What is the minimum required thickness for a shell course in an aboveground
storage tank constructed to API 653, assuming the tank is in non-refrigerated
service and the minimum design metal temperature is above -20°F?
A) 0.100 inches
B) 0.125 inches
C) 0.1875 inches
D) 0.250 inches
Correct Answer: B) 0.125 inches
Rationale: API 653 Section 4.3.2.1 requires that the minimum shell thickness for
any shell course, excluding corrosion allowance, shall not be less than 0.125
inches for tanks in non-refrigerated service with a minimum design metal
temperature above -20°F. This ensures structural integrity against internal
pressure and external loads.
Question 2
According to API 653, what is the maximum allowable fill height for a tank that has
undergone a settlement evaluation?
A) The original design fill height
B) 90% of the original design fill height
,C) The height determined by the reduced shell thickness and settlement analysis
D) The height specified by the manufacturer
Correct Answer: C) The height determined by the reduced shell thickness and
settlement analysis
Rationale: API 653 Section 4.3.3.1 states that the maximum allowable fill height
must be recalculated based on the measured minimum shell thickness, corrosion
rates, and any settlement that affects the tank's structural stability. The fill
height must not exceed the value that maintains allowable stresses per API 650
design criteria.
Question 3
Which type of weld joint is most commonly used for vertical shell seams in
aboveground storage tanks according to API 653?
A) Lap joint
B) Butt joint with full penetration
C) Corner joint
D) Edge joint
Correct Answer: B) Butt joint with full penetration
Rationale: API 653 references API 650 for welding requirements. Butt joints with
full penetration are standard for vertical shell seams because they provide the
necessary strength, continuity, and resistance to cyclic loading. Lap joints are not
permitted for primary shell seams due to stress concentration concerns.
Question 4
When performing a thickness measurement survey on a tank shell, what is the
minimum number of readings per shell course required by API 653?
A) One reading per shell course
B) Two readings per shell course, 180 degrees apart
C) Four readings per shell course, 90 degrees apart
D) Eight readings per shell course, 45 degrees apart
,Correct Answer: C) Four readings per shell course, 90 degrees apart
Rationale: API 653 Section 4.3.1.1 requires a minimum of four thickness readings
per shell course, uniformly spaced around the circumference at approximately
90-degree intervals. Additional readings are required in areas of suspected
corrosion or pitting.
Question 5
What is the primary purpose of the hydrostatic test required after major repairs to
an aboveground storage tank?
A) To check for leaks only
B) To verify the structural integrity and leak-tightness of the tank
C) To test the foundation stability
D) To calibrate the level gauging system
Correct Answer: B) To verify the structural integrity and leak-tightness of the
tank
Rationale: API 653 Section 12.2.1 mandates hydrostatic testing after major
repairs to confirm that the tank can safely contain the product at design fill
height without leakage or excessive deformation. The test also validates weld
quality and shell stability under operational loads.
Question 6
According to API 653, what is the acceptance criteria for pitting corrosion on the
shell of an aboveground storage tank?
A) Pits deeper than 50% of the nominal thickness are unacceptable
B) Pits that reduce the remaining thickness below the minimum required
thickness are unacceptable
C) All pits must be filled by welding
D) Pits are acceptable if they do not leak during hydrotest
Correct Answer: B) Pits that reduce the remaining thickness below the minimum
required thickness are unacceptable
, Rationale: API 653 Section 4.3.4.1 specifies that pitting is acceptable provided
the remaining thickness in the pit area is at least the minimum required
thickness calculated per the design formulas. Isolated pits may be evaluated
individually, and if they penetrate below the minimum, they must be repaired or
the tank derated.
Question 7
What is the minimum distance from a tank shell to the property line for a new
aboveground storage tank containing flammable liquids?
A) 50 feet
B) 100 feet
C) 150 feet
D) Determined by NFPA 30 and local codes
Correct Answer: D) Determined by NFPA 30 and local codes
Rationale: API 653 does not set property line distances; it references NFPA 30
and applicable local regulations. Typically, distances vary based on tank size,
product type, and fire protection measures. The inspector must be familiar with
these referenced standards.
Question 8
In API 653, what does the term "remaining life" refer to for a tank component?
A) The total age of the tank since construction
B) The estimated time until the component thickness reaches the minimum
required thickness at the current corrosion rate
C) The warranty period provided by the manufacturer
D) The time until the next scheduled inspection
Correct Answer: B) The estimated time until the component thickness reaches
the minimum required thickness at the current corrosion rate
Rationale: API 653 Section 4.3.5 defines remaining life as the calculated time (in
years) based on the measured thickness, minimum required thickness, and
