Industrial Application of SENT and Segment Testing on Deepwater Buckle Arrestor Assembly Installed by S-Lay

摘要

For a major deepwater pipeline project in the Black Sea, Buckle Arrestors will be deployed to prevent catastrophic buckle propagation in the event of collapse. Buckle Arrestor Assemblies (BAAs) will be installed using the S-lay pipeline installation method, then introducing cyclic plastic strain on the BAAs’ girth welds during their passage over stinger’s rollers. Fracture during installation is one of the potential failure modes for the girth weld. A material testing and assessment program has been launched at Centro Sviluppo Materiali (Italy) aimed at evaluating the impact of in-field strain sequence on a defected girth weld. The program was articulated in the evaluation of toughness by using single-specimen method with compliance technique on large thickness SENT samples. Then cyclic tearing sequence has been applied on Segment specimens with increased daylight length, aimed at reproducing the real pipe remote strain conditions by small-to-medium scale testing. Accompanying the testing program, a series of ECA calculations has been performed to investigate the robustness of the segment testing methodology used to evaluate the resistance of flawed pipes when subjected to tearing plus cycling loading scenario. As a main conclusion, the segment with increased daylight methodology has been found robust. It has been confirmed by comparison of experimental results and ECA pipe solutions provided by both BS 7910 and API 579.