API 653 Aboveground Storage Tank Inspector
Certification Exam Questions And Correct
Answers (Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. What is the primary purpose of conducting a tank bottom
inspection?
To assess corrosion and structural integrity
Tank bottoms are prone to corrosion and leakage, so inspecting
them ensures safe operation.
2. Which type of inspection requires tank entry?
Internal inspection
Internal inspections allow direct examination of the tank shell,
floor, and roof for defects.
3. The minimum frequency for external tank shell inspections under
API 653 is:
Annually
Annual external inspections help detect external corrosion or
mechanical damage early.
4. When is a tank considered suitable for continued service without
repairs after an inspection?
When all measured thicknesses are within allowable limits
API 653 provides minimum thickness requirements to ensure
structural integrity.
,5. Which NDE method is commonly used to detect shell corrosion?
Ultrasonic testing (UT)
UT accurately measures wall thickness and identifies localized
corrosion.
6. What is the primary purpose of a hydrostatic test?
To verify the tank’s structural integrity under pressure
Filling the tank with water tests for leaks and ensures it can safely
hold the design volume.
7. Which part of the tank is most susceptible to corrosion?
Tank bottom near the shell (knuckle area)
The knuckle area often traps water and sludge, accelerating
corrosion.
8. How should tank settlement be monitored?
By measuring shell and foundation elevations
Monitoring settlement ensures the tank remains level, preventing
structural stress.
9. What is the recommended action when a tank shell exhibits local
thinning below minimum thickness?
Repair or replace the affected section
Operating a tank with inadequate shell thickness risks failure.
10. Which inspection is required after significant operational
changes?
Special inspection
Changes like increased operating temperature or pressure may
require evaluation for safety compliance.
, 11. What does “corrosion allowance” refer to?
Extra thickness provided during design to compensate for
expected corrosion
It ensures the tank remains safe over its expected service life
despite material loss.
12. When should a tank roof be inspected?
During internal inspections
Roof inspection identifies corrosion, deformation, or roof support
damage.
13. What is the purpose of the “floor-to-shell weld inspection”?
To detect cracking or corrosion at the weld joint
This joint is prone to stress concentration and corrosion from
water accumulation.
14. Which material is commonly used for API 653 tank
construction?
Carbon steel
Carbon steel provides adequate strength and corrosion resistance
when protected appropriately.
15. What is a common cause of tank bottom corrosion?
Water and sludge accumulation
Moisture at the bottom reacts with steel, causing pitting and
thinning.
16. How often should a tank undergo a comprehensive internal
inspection if it is in active service?
Every 5 years, or sooner based on previous findings
API 653 recommends intervals based on corrosion rates and tank
history.
Certification Exam Questions And Correct
Answers (Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. What is the primary purpose of conducting a tank bottom
inspection?
To assess corrosion and structural integrity
Tank bottoms are prone to corrosion and leakage, so inspecting
them ensures safe operation.
2. Which type of inspection requires tank entry?
Internal inspection
Internal inspections allow direct examination of the tank shell,
floor, and roof for defects.
3. The minimum frequency for external tank shell inspections under
API 653 is:
Annually
Annual external inspections help detect external corrosion or
mechanical damage early.
4. When is a tank considered suitable for continued service without
repairs after an inspection?
When all measured thicknesses are within allowable limits
API 653 provides minimum thickness requirements to ensure
structural integrity.
,5. Which NDE method is commonly used to detect shell corrosion?
Ultrasonic testing (UT)
UT accurately measures wall thickness and identifies localized
corrosion.
6. What is the primary purpose of a hydrostatic test?
To verify the tank’s structural integrity under pressure
Filling the tank with water tests for leaks and ensures it can safely
hold the design volume.
7. Which part of the tank is most susceptible to corrosion?
Tank bottom near the shell (knuckle area)
The knuckle area often traps water and sludge, accelerating
corrosion.
8. How should tank settlement be monitored?
By measuring shell and foundation elevations
Monitoring settlement ensures the tank remains level, preventing
structural stress.
9. What is the recommended action when a tank shell exhibits local
thinning below minimum thickness?
Repair or replace the affected section
Operating a tank with inadequate shell thickness risks failure.
10. Which inspection is required after significant operational
changes?
Special inspection
Changes like increased operating temperature or pressure may
require evaluation for safety compliance.
, 11. What does “corrosion allowance” refer to?
Extra thickness provided during design to compensate for
expected corrosion
It ensures the tank remains safe over its expected service life
despite material loss.
12. When should a tank roof be inspected?
During internal inspections
Roof inspection identifies corrosion, deformation, or roof support
damage.
13. What is the purpose of the “floor-to-shell weld inspection”?
To detect cracking or corrosion at the weld joint
This joint is prone to stress concentration and corrosion from
water accumulation.
14. Which material is commonly used for API 653 tank
construction?
Carbon steel
Carbon steel provides adequate strength and corrosion resistance
when protected appropriately.
15. What is a common cause of tank bottom corrosion?
Water and sludge accumulation
Moisture at the bottom reacts with steel, causing pitting and
thinning.
16. How often should a tank undergo a comprehensive internal
inspection if it is in active service?
Every 5 years, or sooner based on previous findings
API 653 recommends intervals based on corrosion rates and tank
history.
