Evaluation of inspection performance as achieved

Integrity management is increasingly focussed on quantitative information on asset condition. This is being supported by advances in inspection technology that enable collection of large quantities of digital data. A key feature of the evolving approaches to integrity management is a definition, at the planning stage, of the inspection performance requirements, e.g. wall thickness measurement accuracy or probability of detection (POD). These requirements are set such that the inspection planned will deliver the level of information required to support the integrity process.

Validation that the inspection performance actually achieved meets the requirements is fundamental step to ensuring the updates to information in the integrity process are reliable. This is critical to making integrity decisions that are aligned to risk and how that is changing over time. Assessment of inspection performance as achieved is also an important step in Quality Assurance of inspection and helps ensure consistent and cost effective delivery of inspection meeting the requirements.

Sonomatic has developed and applies methods for quantitative assessment of inspection performance as achieved. These methods cover the following.

• Probability of detection. Assessment of signal data and/or measurements reported to make estimates of POD as achieved using POD modelling.
• Wall thickness measurement accuracy. A range of statistical methods are applied to determining measurement accuracy as achieved. These include analysis of the raw signal data, point to point measurement variations and repeat inspection comparison.

The nature and extent of the assessments varies according to each situation but the requirement is becoming more widespread and Sonomatic increasingly provides a performance assessment as part of the inspection. This is particularly relevant to situations where the integrity decisions are based on sample inspection, e.g. Type B NII and compliance inspection for dry gas pipelines.

Sonomatic also provides assessments of inspection performance as a third party QA review to clients.