Summary of Design and Validation of in-Duct Composite Soft Pipe for Subsea Pipelines

To address the challenges of prolonged maintenance cycles and high operational costs during the later service life of subsea pipelines, an innovative three-layer composite structure has been developed. This structure features an inner layer composed of thermoplastic polyurethane (TPU), a middle reinforcement layer made of high-strength Kevlar fiber, and an outer protective layer constructed from modified TPU. This advanced design has enabled the successful creation of a domestically produced in-duct composite soft pipe tailored for subsea applications. Land-based pilot tests have demonstrated the exceptional flexibility and durability of this composite soft pipe. During testing, the pipe successfully navigated through a complex pathway consisting of eight 90-degree bends and two 150-degree bends, achieving a total travel distance of 260 meters without structural compromise. Furthermore, comprehensive pressure tests confirmed that the pipeline fully meets industry-standard requirements for performance and safety. This breakthrough in composite soft pipe technology provides a scientifically grounded and practical solution for extending the service life of subsea pipelines while ensuring safe and cost-effective operations. By significantly reducing maintenance demands and enhancing operational efficiency, this innovation supports the long-term economic viability and reliability of subsea infrastructure in offshore energy development.