Mechanical Analysis of Lined Pipe System Under Temperature–Pressure Coupling in Elastic Laying

Abstract

Lined pipes are widely used in oil and gas transportation systems due to their excellent corrosion resistance and cost-effectiveness. However, current design codes often oversimplify their mechanical behavior by treating them as single-layer systems, neglecting the complex interactions between the liner and outer pipes under temperature–pressure coupling. To address this gap, this study develops a finite element model for a Φ323.8 × (10 + 3) mm X60-825 lined pipe under elastic laying conditions. The model evaluates stress distribution, bonding strength, and liner deformation under varying operational conditions, including temperatures ranging from 20 °C to 80 °C and internal pressures from 0 MPa to 14 MPa. Key findings reveal that the liner pipe approaches its yield strength (241 MPa) under high-pressure conditions, with a maximum Tresca stress of 238.81 MPa, while the outer pipe reaches 286.51 MPa. Internal pressure significantly enhances bonding strength, increasing it from an initial 0.85 MPa to 11.86 MPa at 14 MPa, thereby reducing the risk of delamination. Simplified single-layer models, which ignore the liner’s pressure-bearing effect, underestimate stress interactions, resulting in a 16.63% error in outer pipe stress under extreme conditions. These results underscore the limitations of simplified models and highlight the importance of considering multi-field coupling effects in pipeline design. This study provides critical insights for optimizing laying radii and ensuring the long-term integrity of lined pipe systems. Future work should focus on experimental validation and microstructural analysis to further refine the design guidelines.