API 653 RECERTIFICATION PRACTICE
EXAM 1 QUESTIONS AND CORRECT
ANSWERS (VERIFIED ANSWERS) PLUS
RATIONALES 2025
1. What is the maximum allowable settlement between shell courses before it
requires engineering evaluation?
A. 1/2 inch
B. 1 inch
C. 2 inches
D. 3 inches
– Differential settlement >2" may affect structural integrity and requires
evaluation.
2. What is the minimum remaining shell thickness before a tank must be taken
out of service?
A. 0.10 inches
B. 0.100 t_min
C. 0.050 inches
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,D. 0.500 inches
– Per API 653, minimum thickness must not fall below 0.100 × t_min.
3. How often must a visual external inspection be performed on an in-service
tank?
A. Every 5 years or per RBI
B. Every 10 years
C. Every year
D. Every 15 years
– API 653 recommends external inspections every 5 years unless RBI dictates
otherwise.
4. The minimum temperature for hot work on carbon steel is:
A. 32°F
B. 60°F
C. 100°F
D. No minimum
– 60°F prevents brittle fracture in carbon steel.
5. Magnetic particle testing is best used for:
A. Internal corrosion
B. Volumetric defects
C. Surface/subsurface cracks
D. Measuring shell thickness
– MT is ideal for detecting fine cracks.
6. When evaluating corrosion, what is the minimum thickness for the bottom
plate with a release prevention barrier (RPB)?
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, A. 0.050 inches
B. 0.050 inches uniformly
C. 0.100 inches
D. 0.200 inches
– With RPB, uniform thickness must not fall below 0.050 inches.
7. Who is responsible for authorizing repairs on a tank per API 653?
A. Welder
B. Inspector
C. Authorized Inspector
D. Contractor
– Only the Authorized Inspector can approve repairs.
8. What is the formula to calculate the minimum required thickness of a shell
course?
A. t = (H × G) / (2 × S)
B. t = (H × D × G) / (2 × S × E)
C. t = (2 × S × E) / (H × G)
D. t = D / 2t
– API 653 uses this pressure-stress-based formula.
9. What NDE method is mandatory after welding a bottom patch plate?
A. RT
B. MT or PT
C. UT
D. VT only
– Surface NDE (MT or PT) is mandatory on welded repairs.
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EXAM 1 QUESTIONS AND CORRECT
ANSWERS (VERIFIED ANSWERS) PLUS
RATIONALES 2025
1. What is the maximum allowable settlement between shell courses before it
requires engineering evaluation?
A. 1/2 inch
B. 1 inch
C. 2 inches
D. 3 inches
– Differential settlement >2" may affect structural integrity and requires
evaluation.
2. What is the minimum remaining shell thickness before a tank must be taken
out of service?
A. 0.10 inches
B. 0.100 t_min
C. 0.050 inches
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,D. 0.500 inches
– Per API 653, minimum thickness must not fall below 0.100 × t_min.
3. How often must a visual external inspection be performed on an in-service
tank?
A. Every 5 years or per RBI
B. Every 10 years
C. Every year
D. Every 15 years
– API 653 recommends external inspections every 5 years unless RBI dictates
otherwise.
4. The minimum temperature for hot work on carbon steel is:
A. 32°F
B. 60°F
C. 100°F
D. No minimum
– 60°F prevents brittle fracture in carbon steel.
5. Magnetic particle testing is best used for:
A. Internal corrosion
B. Volumetric defects
C. Surface/subsurface cracks
D. Measuring shell thickness
– MT is ideal for detecting fine cracks.
6. When evaluating corrosion, what is the minimum thickness for the bottom
plate with a release prevention barrier (RPB)?
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, A. 0.050 inches
B. 0.050 inches uniformly
C. 0.100 inches
D. 0.200 inches
– With RPB, uniform thickness must not fall below 0.050 inches.
7. Who is responsible for authorizing repairs on a tank per API 653?
A. Welder
B. Inspector
C. Authorized Inspector
D. Contractor
– Only the Authorized Inspector can approve repairs.
8. What is the formula to calculate the minimum required thickness of a shell
course?
A. t = (H × G) / (2 × S)
B. t = (H × D × G) / (2 × S × E)
C. t = (2 × S × E) / (H × G)
D. t = D / 2t
– API 653 uses this pressure-stress-based formula.
9. What NDE method is mandatory after welding a bottom patch plate?
A. RT
B. MT or PT
C. UT
D. VT only
– Surface NDE (MT or PT) is mandatory on welded repairs.
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