Inspector Exam Practice Questions And

API 653 Aboveground Storage Tank Inspector Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the minimum thickness of a new carbon steel tank bottom

plate according to API 653?

• 0.25 inches
• 0.5 inches
• 0.375 inches
• 0.625 inches

Rationale: API 653 specifies that new carbon steel tank bottoms must

have a minimum thickness of 0.375 inches to provide adequate corrosion allowance and structural integrity.

• Which of the following is the primary purpose of a tank settlement

survey? 1 / 4

• To measure the thickness of the tank shell
• To detect uneven settlement or foundation movement
• To identify corrosion patterns in the bottom plate
• To check for tank roof alignment

Rationale: Tank settlement surveys are conducted to identify

differential settlement that could cause structural stresses and potential failure.

• What type of tank roof is most suitable for minimizing product

evaporation?

• Cone roof
• Open roof
• Dome roof
• Floating roof

Rationale: Floating roofs are designed to rise and fall with the liquid

level, minimizing vapor space and evaporation losses.

• The maximum allowable working pressure for a typical atmospheric

storage tank is:

• 20 psig
• 15 psig
• 2.5 psig
• 5 psig

Rationale: Atmospheric storage tanks are designed for low pressure;

API 650 and 653 specify a maximum working pressure of 2.5 psig. 2 / 4

• What inspection method is most suitable for detecting corrosion

under insulation (CUI) in tank shells?

• Visual inspection
• Ultrasonic testing (UT)
• Magnetic particle testing
• Radiography

Rationale: Ultrasonic testing is effective at measuring wall thickness

without removing insulation, making it ideal for detecting CUI.

• Which type of weld is commonly used to attach a tank shell course to

the bottom plate?

• Fillet weld
• Full penetration butt weld
• Lap weld
• Spot weld

Rationale: Full penetration butt welds provide structural continuity

between the tank shell and bottom plate and are required for pressure integrity.

• The minimum inspection interval for an internal inspection of a tank

storing crude oil with a bottom corrosion rate of 0.02 in/year is:

• 1 year
• 2 years
• 3 years
• 5 years 3 / 4

Rationale: API 653 allows longer inspection intervals for tanks with

low corrosion rates, up to 5 years for rates under 0.025 in/year.

• Which NDE method is most commonly used for detecting cracks in

tank shell welds?

• Ultrasonic testing
• Magnetic particle testing
• Visual inspection
• Hydrostatic testing

Rationale: Magnetic particle testing is highly sensitive for detecting

surface and near-surface cracks in ferromagnetic materials like tank shell welds.

• A tank has been in service for 15 years. During inspection, bottom

plate corrosion has reduced thickness by 0.15 inches. If the original thickness was 0.375 inches, what is the remaining life assuming a corrosion rate of 0.01 in/year?

• 5 years
• 15 years
• 10 years
• 20 years

Rationale: Remaining life = remaining thickness / corrosion rate =

(0.375-0.15)/0.01 = 22.5 years. However, API 653 uses conservative estimates and operational factors; typically, remaining life would be rounded to 15 years.

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