Numerical Investigation of Spring-Energized Seals for a Fluid Swivel in a Single-Point Mooring System

Single-point mooring systems are among the key systems for offshore oilfield development. The fluid swivel is a core component of such systems, enabling fluid transfer while allowing the vessel to follow the weather vane effect. The spring-energized seal is critical for ensuring reliable fluid transmission. Existing studies on spring-energized seals primarily focus on small-scale mechanisms, with limited research on large-scale seal design under complex operating conditions. This work investigates the dynamic sealing performance of the oil-transferring rotary joint in a 300,000 ton VLCC catenary single-point mooring system. A spring-energized seal is designed with a PTFE-based composite as the sealing jacket and Inconel 718 as the spring material. A finite element model of the spring-energized seal is developed in ANSYS 2022 R1, and the design is optimized to achieve lower equivalent strain, more uniform contact pressure distribution, larger contact width, and reduced friction. Fatigue life analysis of the optimized design verifies its reliability over a 10-year service period. The proposed study provides a reference for the design of dynamic seals in high-end offshore engineering equipment.