Stress corrosion cracking (SCC) in gas transmission lines is a serious threat to pipeline integrity, and gas pipeline operators today implement and run asset integrity management programs to maintain the integrity of their energy infrastructure. Detection and identification by inline inspection (ILI) smart tools is a vital part of this effort.
NDT Global is developing an ultrasonic based technology which addresses crack diagnostics in gas pipelines. This development utilizes directional gas-coupled guided wave generation in the pipe wall, which allows inspection of the asset by non-contact measurement. The development has shown that the measurement principle is highly sensitive to crack-like features, and less sensitive to other pipeline features such as sharp-edge corrosion. These developments will significantly improve pipeline safety for systems subjected to SCC.
This paper is a continuation of the development presented at International Pipeline Conference (IPC) in Calgary, 26th-30th September 2022. At IPC the focus was the history of the development, gap analysis of existing solutions and results from small-scale testing. Since then, a full-fledged 20'' tool has been developed and tested in a large Nitrogen filled pressure chamber in Norway, operated at different pressures. It is demonstrated that results from small-scale testing can be carried over to a full-scale realistic pipeline environment. The tool has now been validated with several pipe spools containing natural SCCs and corrosion fields, together with manufactured cracks and other pipeline defects, to derive an initial performance specification regarding detection, discrimination and sizing capabilities of the 20'' tool.