Analysis of large numbers of inspection data to assess corrosion remnant life in offshore pipework

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Analysis of large numbers of inspection data to assess corrosion remnant life in offshore pipework

Terpstra, Sieger / Hoeve, Fred / Camp, Peter van de / Hughson, Willie / Stewart, Jake

This paper reports on the experiences with the upgrading of the integrity of offshore production platforms located in the North Sea, now around 25 year old. In the project a significant part of the work is spent on upgrading the integrity of the pipework. To identify pipe sections that need replacement, extensive inspection is carried out to reveal the internal and external condition of the pipework. The inspection is followed by analysis of the internal wall loss data to assess pipework remnant life. Key factors determining the effectiveness of the inspection process are the knowledge of the corrosion rate and its distribution. Challenges to identify these come, amongst others, from the sheer volume of the inspection data, a mix of degradation phenomena, the limited coverage of a typical pipework inspection process, and data errors of all kind. For this work special analysis tools have been developed, such as automated trending of corrosion rates, and creating overviews of corrosion damage in bar graphs, histograms and pipework drawings. With these tools the corrosion characteristics in the pipe circuits could be understood much better. With this knowledge, and the use of non-intrusive inspection principles an inspection programme was developed and an optimized pipework repair scope have been identified that meets project targets. In this process numerous learning points and improvements were identified with which the effectiveness of future pipework inspection will be enhanced.