Planning guide · Published by Atlantis NDT
Can two thickness campaigns be compared? Check before plotting a trend
Review locations, measurement context and component changes before using inspection history for corrosion assessment.
Start with the decision you need to make
A difference between recorded thickness values is not automatically evidence of a corrosion rate. First confirm that the measurements refer to the same component and comparable locations, with compatible units and documented examination conditions. Repairs, relocated points, coatings and changed coverage can complicate interpretation. Prepare a comparability review for the responsible engineer before asking software to plot a trend. Keep excluded or uncertain records visible so the graph does not imply more continuity than the evidence supports.
What to check and why it matters
| Decision area | Evidence to prepare | Question to resolve |
|---|---|---|
| Location continuity | Check component identity, CML or point reference, drawing revision and physical location. Retain records of replacement or relocation. | Are the two values associated with the same intended measurement location? |
| Measurement context | Review method, equipment references, surface or coating condition, units and reported limitations. Clarify missing metadata before combining records. | Which differences could affect the meaning of the comparison? |
| Engineering use | Identify the assessment the owner needs and who confirms whether the data is suitable. A planning worksheet cannot establish remaining life or an interval. | Which values are accepted for assessment, and which require further examination? |
Illustrative example · Not a customer case study
Apply the questions to a real-world situation
Hypothetical campaign: an old report uses point names that were reassigned after a spool replacement. A spreadsheet initially shows an apparent increase in thickness. The reviewer separates the replacement component’s baseline from the previous history and documents the mapping decision. The corrected dataset can support a responsible review without presenting the change as measurement error or an improvement in the original component’s condition.
Prepare your working brief
Capture what is known and name the unresolved questions. You can use the worksheet without registering or sending information to Atlantis.
- Comparison purpose
- State the question the integrity engineer needs answered.
- Location evidence
- Describe point IDs, drawings and any component changes.
- Measurement metadata
- List dates, units, methods and relevant limitations.
- Uncertain records
- Identify missing or conflicting information requiring review.
- Assessment owner
- Name the role that approves the comparison dataset and next actions.
When you need project-specific support
Discuss the examination scope for ultrasonic thickness measurement services. Confirm the current deliverables and fit for your requirement with the Atlantis team.
Explore traceable inspection history visualization. Confirm the current deliverables and fit for your requirement with the Atlantis team.
For a US enquiry, include the project state and time zone, the responsible employer or owner, and the documents governing the work. For other countries, include the relevant recognition or customer requirements. Delivery and availability are confirmed for the engagement.
Request an inspection scope reviewScope and further reading
This guide does not calculate corrosion rates, remaining life, fitness for service or inspection intervals. Those decisions require suitable data and authorized engineering assessment.
Continue with the detailed companion guide, Reconciling Mismatched Measurement Baselines Across Corrosion Campaigns, for a related evidence-handling workflow and its source references. The planning suggestions here are original discussion aids, not approved procedures or reproductions of standards.
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