The method
Before using the result
- Comparable measurement locations/methods and representative uniform loss. Local damage, uncertainty and future service changes are not modelled.
Worked examples
These original training examples illustrate the method for API 510 Pressure Vessel Inspector (API 510). Use the matching “Load example” button above to explore a variation; example values are not equipment settings or prescribed criteria.
1. Worked example
Compare thickness readings taken at the same inspection location over documented dates. A thicker later reading needs measurement review rather than a negative-life extrapolation.
- Earlier thickness
- 0.01 m
- Later thickness
- 0.009 m
- Earlier measurement date
- 2021-10-15
- Later measurement date
- 2026-10-15
- Elapsed time = 4.999315537303217 years (365.25-day basis).
- Rate = (0.01 − 0.009) / 4.999315537303217 m/year.
- Elapsed period: 4.999316 years
- Signed thickness-loss rate: 0.2000274 mm/year
2. Comparison example
Compare a different supplied condition using the same method. For Welding Exam, the important check is that the input meaning, units and method assumptions still match the problem.
- Earlier thickness
- 0.01 m
- Later thickness
- 0.0085 m
- Earlier measurement date
- 2021-10-15
- Later measurement date
- 2026-10-15
- Elapsed time = 4.999315537303217 years (365.25-day basis).
- Rate = (0.01 − 0.0085) / 4.999315537303217 m/year.
- Elapsed period: 4.999316 years
- Signed thickness-loss rate: 0.3000411 mm/year
Check your understanding
1. Which relationship is used?
Thickness-loss rate = (earlier thickness − later thickness)/elapsed years; year = 365.25 days.
2. Which assumption should you check first?
Comparable measurement locations/methods and representative uniform loss. Local damage, uncertainty and future service changes are not modelled.
3. How should you verify a different unit system?
Convert every input to the displayed calculation units first. Equivalent physical inputs must give equivalent results; a unit label alone does not convert a number.
Continue with the matching exam topic
This tool connects to API 510 Pressure Vessel Inspector (API 510) free practice. Work through a question independently, then use the calculation steps to identify where your method differs. The tool stays free whether or not you choose paid preparation.