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Technique Limitations

All inspection techniques have limitations and specifying an ineffective approach due to performance uncertainties about its performance capabilities is arguably worse than doing nothing at all because it can generate inaccurate or irrelevant information which can engender a false sense of security or lead to unnecessary remedial action.

These uncertainties are compounded by various manufacturers' claims about the capabilities of their particular offerings and the fact that many of the established techniques were 'incorporated' and prescribed before their limitations were fully appreciated.

For instance, radiography - although highly effective at producing a recognizable visual image and highly suited to some manufacturing quality control functions - only records change in density. It is therefore, at best, a comparative means of defect size measurement. It is also orientation sensitive and, in today's safety and cost conscious world, it is now recognized as hazardous and logistically cumbersome. Despite these limitations, and the fact that more appropriate alternatives do exist, it is still prescribed as the prime inspection technique in many major fabrication codes and, consequently, is still in regular use today.

Reflectivity based ultrasonic methods suffer similar limitations yet, by virtue of established practice, enjoy similar status.

Our view is quite simple - if an inspection technique isn't capable of reliably detecting and accurately reporting defects or its application is inappropriate from a commercial or safety perspective, then that technique is not valid if used in isolation.

Awareness of technique performance capabilities and limitations is crucial if any value is to be derived from their usage and their effective usage can help protect vital assets.

This brick pyramid gives a few of the cracks in the technique capability equation-

Also see -

- Probability of Detection
- Coverage
- Resolution
- Reproducibility

For further information on our inspection services, contact Colin Mortimer