Stress Corrosion Cracking (SCC) is a challenging integrity threat facing today’s pipeline industry. Environmental cracking processes are complex, not always well understood, and often difficult to predict.
The morphology of Stress Corrosion Cracking (SCC) is highly variable, and there may be many other features present in the pipe body and seam weld which are not a result of environmental cracking but create similar signals in inspection data. These challenges make it difficult to reliably identify the different feature types based on a single source of inspection data. This in turn creates significant uncertainties as to how to best manage the future integrity of a pipeline subject to SCC.
When SCC is discovered in a pipeline system, industry-based practice requires further investigation in the form of hydrostatic testing, inline inspection, or direct assessment. Hydrostatic testing often requires significant downtime, which is often impractical for many operators. That is why a range of multi-disciplinary elements is needed to effectively manage these threats.
ROSEN’s reasoned and systematic approach, that focusses efforts on the critical issues and locations of features, is overviewed in the Crack Management Framework.
In this approach, all available data is integrated and utilized to fully understand the probable cause and morphology of any SCC, and to evaluate the sizes of these critical defects in order to ensure safe operation. Since not all parts of the pipeline have the same susceptibility to SCC, dividing the pipeline into segments of similar SCC risk is required to help focus the ILI data evaluation effort and optimize future integrity management activity. Effective segmentation requires the integration of extensive pipeline information, including original pipeline design data, pipeline coating data, construction methods, terrain representations such as those from Google Earth™, soil data, and rainfall records. This information is then combined with the inline inspection reports; since SCC may be linked to stress raisers such as dents, areas of corrosion, and locations with bending strain. With a thorough understanding of the issues and constraints, future integrity management programs are enabled and comprehensive asset care can be achieved.
Andrew Wynne, Integrity Engineer at ROSEN UK, gave a presentation, titled “Completing the Jigsaw and getting to know your SCC,” at the Institution of Gas Engineers & Managers (IGEM) Young Person’s Paper Competition (YPPC) 2019. In his presentation, which won the first prize in the U.K. North East regional heat, Wynne provided an overview of a project in which in-line inspection, in-field verification and finite element analysis were used to identify a distinct pattern between Stress Corrosion Cracking (SCC) and stress concentrations introduced during construction. The discovery of this connection between cracking and construction practices resulted in a deep understanding of the cause of SCC across the pipeline system. Wynne will represent the North East in the national finals of the completion on June 13, 2019. Find out more about the IGEM YPPC here: http://www.igem.org.uk/news/yppc-2019.aspxx