The high pressure liquid and gas pipeline network is aging in all regions around the globe and becomes more and more vulnerable to integrity threats. Besides general corrosion, stress corrosion cracking becomes an increasingly important topic. Pipeline operators are facing the challenge to address these threats. Most (31%) of the pipelines worldwide are pipelines with diameters ≤10″ [1]. Providing a better inline inspection service starting with small diameter pipelines will therefore address the threats arising from stress corrosion cracking most effectively. This way the typical diameters of pipelines posing risks served first.

Ultrasound inline inspection for pipelines is known for years and provide several advantages over hydrostatic tests. Its most important advantage for pipeline operators is that sub-critical flaws can be detected, which results in a comprehensive picture of the integrity status of the pipeline.

Despite the advantages and the experience with ultrasound inline inspection, the sizing precision and the sizing confidence are two factors limiting the success of the ultrasound inline inspection technology.

This paper presents several measures to address these two issues and thus to provide a more valuable service for pipeline operators.

There are two ways to increase the sizing precision and the sizing confidence: either to develop new procedures to evaluate existing data or to gather more or better data during inline inspection. The focus in this paper will be on the second option.

Three measures are described in this paper: first, using a new design to improve the guidance of the sensor carrier leading to better data quality, especially at welds. Second, using more sensors for the inline inspection tools. This will not only provide a more precise circumferential position of the flaws but also more data for every flaw. Finally, recording more echoes at each point of the pipeline which is the basis to extract more information from every measurement.

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