Experimental and analytical study on mechanical performance of hydraulically expanded steel-lined pipes

Mechanically lined pipes (MLPs) consist of a carbon steel base pipe, providing the necessary structural strength, and a stainless steel or nickel alloy liner, offering corrosion resistance . These pipes are widely utilized in oil and gas development, particularly in environments with high hydrogen sulfide content. The hydraulic expansion process, favored for its cost-effectiveness and consistent quality, is frequently employed to manufacture these pipes. During the reel-lay process, the pipeline undergoes significant plastic deformation . Insufficient bonding between the base pipe and liner can result in wrinkling and detachment of the liner, rendering the pipeline unusable. According to practical engineering demands, this study conducted production and sawing tests on mechanically lined pipes subjected to various hydraulic forming pressures using industrial equipment. A finite element model , incorporating pipe end boundary conditions, was developed to analyze variations in contact pressure, stress, and geometric dimensions during expansion. Additionally, a theoretical equation for calculating residual contact pressure was formulated. The results highlight the importance of considering non-uniform contact pressure and stress distribution. The numerical model, which accounts for material strain hardening, demonstrated good alignment with experimental results. This research provides essential guidance for the design and production of mechanically lined pipes, thereby enhancing their reliability. • The hydraulic forming process was implemented in real industrial production for mechanically lined pipes. • Finite element models for the real manufacturing processes of mechanically lined pipes were established. • The mechanical properties of mechanically lined pipes during the hydraulic forming process were clarified. • The relationship between the designed hydraulic forming pressure and the residual contact pressure of mechanically lined pipes was presented and compared.