From Detection to Action: EMAT‑Driven SCC Assessment

Introduction.
Stress corrosion cracking (SCC) is a complex degradation mechanism driven by the presence of mechanical stress, a corrosive environment, and the material’s susceptibility. Steel pipelines used for transporting natural gas and oil may be vulnerable, as SCC can initiate and propagate cracks that threaten structural integrity. In advanced stages, the progression of these cracks can reduce the load-carrying capacity of the pipe wall and, under critical conditions, may lead to failure. Consequently, the detection, characterization, and assessment of SCC-related cracking have become components of pipeline integrity management programs.

Methods.
Among the available crack detection technologies in the pipeline industry, Electromagnetic Acoustic Transducer (EMAT) in-line inspection tools have gained relevance in recent years. EMAT technology enables the detection, identification, and sizing of linear indications that may be associated with SCC. However, because of the complexity of SCC morphology (crack colonies, crack interaction), accurate classification and sizing can be challenging. Effective characterization requires field verifications that allow the operator to correlate EMAT signal responses with pipeline properties and actual conditions.

Results.
In a recent case study, field excavation results confirmed that the EMAT tool detected anomalies associated with SCC. However, subsequent destructive testing highlighted adversities in both sizing and classifying these indications, underscoring the challenges associated with characterizing SCC through an ILI alone and reinforcing the need for complementary data integration and field verifications.

Conclusion.
EMAT technology provides capability for detecting and managing anomalies associated with SCC in pipelines, but its effectiveness as part of an SCC integrity management program relies on more than the inspection tool. Threat management requires integrating EMAT results with operational, material, field excavation, destructive testing, and historical data. When EMAT ILI data is combined with material characterization and engineering assessments, operators can make informed integrity decisions and more effectively mitigate the operational risks associated with SCC.