Innovative NDT Approaches for Inspecting Unpiggable Offshore / Subsea Pipelines

Abstract Non-Destructive Testing (NDT) technologies offer effective solutions for inspecting unpiggable offshore pipelines, reducing costs, environmental impact, and safety risks. This paper examines three advanced NDT methods - Pulsed Eddy Current Array (PECA), Acoustic Resonance Technology (ART), and Subsea Phased Array (SPA) - highlighting their complementary roles in detecting and characterizing corrosion. PECA enables inspection through the Concrete Weight Coating (CWC), utilizing advanced sensors to detect areas of gross corrosion larger than half the size of the probe footprint (87x87 mm). Where potential anomalies are indicated, targeted removal of CWC can be carried out to enable more detailed assessment, thus minimizing unnecessary intervention. Once the coating is removed, ART detects and sizes corrosion pits larger than 8 mm, while SPA provides superior resolution for smaller or complex-shaped pits, capturing details often missed by conventional techniques. Together, these technologies enable a comprehensive inspection process - both through and after CWC removal. Integrated with Remotely Operated Vehicles (ROVs), they deliver a precise, efficient, and reliable method for subsea pipeline integrity assessment. This research contributes to the development of more effective and targeted inspection strategies, ultimately enhancing the safety and reliability of offshore pipeline operations.