Top 20 API 570 calculation questions (exam-focused)
Here are 20 exam-focused API 570 calculation questions—these are the most tested numerical patterns you must master for the American Petroleum Institute API 570 Piping Inspector exam.
I’ve included answers + quick logic (so you can revise fast).
🔥 TOP 20 API 570 CALCULATION QUESTIONS
🔴 SECTION 1: CORROSION RATE (CR)
Initial thickness = 12 mm
Current thickness = 10 mm
Time = 5 years
CR = ?
👉 Answer:
CR = (12 − 10) / 5 = 0.4 mm/year
2. Initial = 15 mm, Current = 12 mm, Time = 3 years
👉 Answer:
CR = 1 mm/year
3. Initial = 20 mm, Current = 16 mm, Time = 8 years
👉 Answer:
CR = 0.5 mm/year
4. If CR increases, what happens to remaining life?
👉 Answer: Decreases
5. If no previous data exists, CR should be based on?
👉 Answer: Conservative estimate / similar service
🔴 SECTION 2: REMAINING LIFE (RL)
6. Current thickness = 10 mm
Minimum thickness = 7 mm
CR = 0.5 mm/year
RL = ?
👉 Answer:
RL = (10 − 7) / 0.5 = 6 years
7. Current = 12 mm, Min = 9 mm, CR = 0.3
👉 Answer:
RL = 10 years
8. Current = 8 mm, Min = 6 mm, CR = 0.25
👉 Answer:
RL = 8 years
9. If CR doubles, RL becomes?
👉 Answer: Half
10. If thickness approaches minimum, RL becomes?
👉 Answer: Very low / critical
🔴 SECTION 3: INSPECTION INTERVAL
11. RL = 10 years
Inspection interval = ?
👉 Answer:
Typically ½ RL = 5 years (subject to code limits)
12. RL = 6 years
👉 Answer:
Interval ≈ 3 years
13. RL = 2 years
👉 Answer:
Interval ≤ 1 year
14. Which is correct?
- Interval > RL
B. Interval ≤ RL
C. Interval ignored
D. Random
👉 Answer: B
15. Maximum interval is governed by?
👉 Answer: Code limits (API 570)
🔴 SECTION 4: THICKNESS & CORROSION
16. If thickness loss increases, what happens?
👉 Answer: CR increases → RL decreases
17. If current thickness = minimum thickness?
👉 Answer: Immediate action required
18. If measured thickness is inconsistent?
👉 Answer: Recheck / verify readings
19. If corrosion is localized?
👉 Answer: Use worst-case thickness
20. If inspection data is poor?
👉 Answer: Use conservative assumptions
🧠 ULTRA-FAST FORMULA MEMORY
✔ Corrosion Rate:
CR = (Initial − Current) / Time
✔ Remaining Life:
RL = (Current − Minimum) / CR
✔ Inspection Interval:
≈ ½ Remaining Life (within code limits)
🎯 FINAL EXAM STRATEGY
When solving:
Identify given values
Use correct formula
Check units (mm/year)
Apply conservative logic
🚀 LAST TIP
Most candidates fail because they:
❌ Forget formulas
❌ Mix RL & interval
❌ Ignore conservative approach
👉 You pass if you:
✔ Use formulas correctly
✔ Apply code logic
✔ Stay consistent
