The goal of any tank floor inspection is to formulate an optimal maintenance and repair strategy. To achieve this, key information about the location and severity of damage mechanisms, such as corrosion, is essential. Asset owners need to understand these details efficiently to make informed decisions.
Confidence in the data within an NDT report is crucial. Asset owners must understand the capabilities and limitations of the inspection equipment, including coverage and probability of detection, to make informed decisions. Additionally, inspection integrity and report uniformity are paramount. Asset owners require assurance that all inspections are performed according to regulations and procedures and that reports are clear, consistent, and accessible.
Key considerations for inspection integrity include:
- Inspection Statistics: Details such as the quantity and location of system verification (prove-up), identification of equipment used for prove-up, and range of coverage.
- System Conformance: Information on system calibration dates and quality assurance to ensure performance throughout the inspection.
- Inspection Decisions: Visibility into actions affecting corrosion location and classification.
Such an approach enhances inspection confidence and quality, providing clear reporting.
The final NDT report must meet these requirements to help asset owners devise the best maintenance and repair strategies, leading to optimal inspection intervals.
Providing the Ideal Tank Inspection Report
Magnetic Flux Leakage (MFL) based tank bottom scanners are a well-established and highly valued method for tank floor inspection. Advances in MFL technology, including improvements in key system components, next-generation signal processing, and research breakthroughs, make MFL the primary choice for inspecting large, ferrous surfaces like storage tank floors.
Modern MFL technology offers numerous benefits, such as efficient coverage of critical zones and detailed information on defect location, severity, surface origin, and extent of coverage. Advanced MFL tank floor scanners can create a corrosion map, providing immediate insight into coverage. Advanced analysis tools enable recipients to fully interrogate data sets, determine corrosion rates, and understand reporting conclusions, thus gaining confidence in the inspection.
As tank floor inspection technologies evolve, regulatory bodies increasingly recommend corrosion maps. Organizations like EEMUA now advise providing a corrosion map of the tank floor. However, until all global regulations mandate it, some may question the necessity of a corrosion map.
Challenges and Solutions
A corrosion map can be time-consuming and may seem unnecessary if no corrosion is present. In such cases, a detection-only mode may be preferred, but this relies heavily on the operator, potentially affecting data accuracy due to fatigue and repetition.
A practical solution is hybrid scanning, which combines the benefits of mapping with the flexibility of free scanning. This approach maps only areas or plates of interest, providing a corrosion map where significant wall loss is detected. Hybrid scanning maintains data integrity and traceability while minimizing inspection intervals and meeting asset owner needs. Combining Freescan mode for screening and full mapping mode with defect sizing allows for maximum productivity with recorded and reportable data at areas where it matters most.
Conclusion
Service companies can now offer tailored solutions based on asset owner requirements, including full corrosion maps or hybrid reports mapping only damaged areas. This flexibility ensures data integrity, adherence to regulations, minimized inspection intervals, and comprehensive coverage. The key question is not whether to map, but when to map.
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Authors: Matthew Boat & Andrew Simpson