Alternative Design and Monitoring Options
What the exam expects
When conventional mitigation is impractical, alternative design and monitoring options apply. Candidates must know the options and their trade-offs:
- Design alternatives: corrosion allowance, material upgrade, internal coating, chemical injection points, pigging facilities, and layout changes to avoid stagnant zones.
- Monitoring alternatives: non-intrusive UT, guided-wave, acoustic emission, and remote monitoring where intrusive access is limited.
- Risk-based inspection (RBI): prioritize inspection by likelihood and consequence.
- Data integration: combine monitoring with process and inspection data.
Traps in questions
- Treating non-intrusive methods as equivalent to intrusive probes; each has sensitivity and coverage limits.
- Forgetting that design changes require re-evaluation of the corrosion control program.
- Assuming RBI replaces monitoring; it prioritizes inspection, not chemical control.
Worked example
A line cannot be pigged and has no probe access. The correct alternative is non-intrusive UT plus guided-wave screening, with RBI prioritization, not simply accepting the risk. Rule of thumb: if you cannot measure intrusively, measure non-intrusively and prioritize by risk; never leave a line unmonitored without a documented rationale.