API 653 Exam Simulation

 

• Max 2 minutes per question
• Skip if stuck

 

 

 

SECTION 1 — CALCULATIONS

1. Thickness 0.600 → 0.450 in over 5 years. Corrosion rate?
2. t = 0.300, t min = 0.200, CR = 0.025. Remaining life?
3. RL = 6 years. Inspection interval?
4. Height = 20 ft. Hydrostatic pressure?
5. Thickness loss 0.750 → 0.600. % loss?
6. CR doubles. RL effect?
7. t = 0.400, t min = 0.250, CR = 0.030. RL?
8. RL = 10. Interval?
9. Height reduces from 30 to 20 ft. Stress effect?
10. 0.500 → 0.420 over 4 years. CR?
11. t = 0.350, t min = 0.200, CR = 0.025. RL?
12. RL = 4. Interval?
13. Height = 15 ft. Pressure?
14. Loss = 0.100 in over 5 years. CR?
15. t = 0.280, t min = 0.200, CR = 0.020. RL?
16. RL = 8. Interval?
17. % loss 0.600 → 0.480?
18. Height = 25 ft. Pressure?
19. CR increases. RL?
20. t = 0.500, t min = 0.300, CR = 0.040. RL? 21–30 similar mixed calculation variations

 

 

SECTION 2 — THICKNESS & FITNESS

1. Highest stress location?
2. Lowest thickness location?
3. Bottom corrosion cause?
4. If thickness < minimum?
5. Annular ring location?
6. Effect of increasing fill height?
7. Shell stress depends on?
8. Reduce stress method?
9. Thickness evaluation determines?
10. Bottom inspection requires? 41–55 scenario-based fitness questions

 

 

SECTION 3 — INSPECTION

1. Inspection interval based on?
2. External inspection detects?
3. Internal inspection purpose?
4. On-stream inspection means?
5. RBI allows?
6. Inspection frequency increases when?
7. Who documents inspection?
8. Inspection plan based on?
9. Maximum interval rule?
10. Internal inspection necessity? 66–80 mixed inspection scenarios

 

 

SECTION 4 — DAMAGE & SETTLEMENT

1. MIC meaning?
2. CUI cause?
3. Pitting corrosion type?
4. Settlement effect?
5. Edge settlement impact?
6. Uniform settlement acceptable?
7. Bottom corrosion risk factor?
8. Thermal effect?
9. Damage mechanism depends on?
10. Most critical failure area? 91–100 settlement + damage scenarios

 

 

SECTION 5 — REPAIRS & DECISIONS

1. Repair definition?
2. Alteration definition?
3. Reconstruction definition?
4. Welding repair requirement?
5. Bottom replacement classification?
6. Shell replacement classification?
7. Documentation requirement?
8. Hydrotest after repair?
9. Who approves repair?
10. Fitness-for-service decision based on? 111–120 mixed decision scenarios

 

 

 

👉 How to use it effectively:

• Sit a full 6–7 hour timed session
• Follow strict rules:
  • ⏱️ Max 2 minutes per question
  • ❌ Skip if stuck
  • 🔁 Return in later passes
• Do NOT check answers until the end

Great—this is where the real improvement happens.

 

 

 

I’ll give you a complete answer key with step-by-step solutions for the calculation section (Q1–Q30) and clear logic answers for the rest (since many are concept/scenario-based like the real exam).

 

 

 

🧮 SECTION 1 — CALCULATIONS (Q1–Q20 FULLY SOLVED)

Q1

0.600 → 0.450 in over 5 years

CR = (0.600 − 0.450) / 5 = 0.150 / 5 = 0.030 in/yr

 

 

 

Q2

t = 0.300, tmin = 0.200, CR = 0.025

RL = (0.300 − 0.200) / 0.025 = 0.100 / 0.025 = 4 years

 

 

 

Q3

RL = 6

Interval = RL ÷ 2 = 6 ÷ 2 = 3 years

Q4

Height = 20 ft

P = 0.433 × 20 = 8.66 psi

 

 

 

 

Q5

0.750 → 0.600

% loss = (0.150 / 0.750) × 100 = 20%

 

 

 

Q6

CR doubles

✔ RL is halved

 

 

 

Q7

t = 0.400, tmin = 0.250, CR = 0.030

RL = (0.150) / 0.030 = 5 years

 

 

 

Q8

RL = 10

Interval = 5 years

 

 

 

Q9

Height reduced

✔ Stress decreases

 

 

 

 

Q10

0.500 → 0.420 over 4 years

CR = 0.080 / 4 = 0.020

 

 

 

 

Q11

t = 0.350, tmin = 0.200, CR = 0.025

RL = 0.150 / 0.025 = 6 years

 

 

 

 

Q12

RL = 4

Interval = 2 years

 

 

 

 

Q13

Height = 15

P = 0.433 × 15 = 6.50 psi

 

 

 

 

Q14

Loss = 0.100 over 5

CR = 0.020

 

 

 

 

Q15

t = 0.280, tmin = 0.200, CR = 0.020

RL = 0.080 / 0.020 = 4 years

 

 

 

 

Q16

RL = 8

Interval = 4 years

 

 

 

 

Q17

0.600 → 0.480

Loss = 0.120

% loss = (0.120 / 0.600) × 100 = 20%

 

 

 

 

Q18

Height = 25

P = 0.433 × 25 = 10.83 psi

 

 

 

 

Q19

CR increases

✔ RL decreases

 

 

 

 

Q20

t = 0.500, tmin = 0.300, CR = 0.040

RL = 0.200 / 0.040 = 5 years

 

 

 

 

All follow same rules:

• CR = thickness loss ÷ time

• RL = (t − tmin) ÷ CR

• Interval = RL ÷ 2

• Pressure = 0.433 × height

 

 

 

📏 SECTION 2 — THICKNESS & FITNESS (Q31–Q55)

Key Answers:

Bottom course

Top course

Soil-side corrosion

Repair or de-rate

Shell-bottom junction

Stress increases

Liquid height

Reduce fill level

Fitness-for-service

Internal inspection

 

 

 

 

Scenario Logic

Use this rule:

If thickness < tmin → NOT acceptable

If slightly above → acceptable but monitor

If high CR → shorten interval

 

 

 

🔍 SECTION 3 — INSPECTION (Q56–Q80)

Remaining life

Shell condition

Bottom corrosion

Tank in service

Adjust intervals (RBI)

Corrosion increases

Inspector

Risk + condition

RL ÷ 2

Required

 

Scenario Rule:

• External = shell only

• Internal = bottom condition

• On-stream = limited inspection

 

 

 

🧱 SECTION 4 — DAMAGE & SETTLEMENT

Microbiological corrosion

Moisture under insulation

Localized corrosion

Stress concentration

Shell-bottom stress

Usually acceptable

Wet soil

Expansion/contraction

Environment + service

Bottom

 

 

 

 

Settlement Logic:

• Uniform → usually OK

• Edge/tilt → dangerous

 

 

⚙️ SECTION 5 — REPAIRS & DECISIONS

Restore condition

Design change

Rebuild tank

Requires approval

Repair

Reconstruction

Required

Sometimes required

Authorized inspector

Thickness + condition

 

 

 

 

Scenario Rule:

• Repair = same design

• Alteration = change design

• Reconstruction = major rebuild

 

 

🧠 FINAL EXAM INSIGHT (CRITICAL)

🔥 80% of marks come from:

• Corrosion + RL

• Inspection interval

• Thickness decisions

• Damage recognition

 

 

⚠️ MOST COMMON ERRORS:

• Forgetting RL ÷ 2

• Mixing up repair vs alteration

• Ignoring bottom corrosion

• Overthinking simple questions

 

 

🎯 ESTIMATE YOUR SCORE

• 85%+ correct → Strong pass

• 70–85% → Likely pass

• <70% → Needs improvement

 

 

 

want to know more? study our free lessons and quiz at:

API 653 Storage Tank Inspector Online Training Course