Stability Analysis of Dual-Lifting Vessels under Collaborative Lifting Operation

The current market for the assembly and disassembly of offshore platforms exceeds $100 billion. However, existing methods face limitations that reduce their efficiency. To address these limitations, we propose a dual-vessel collaborative assembly and disassembly system with multiple motion-compensated lifting arms. The compensation system enables the lifting arms to isolate the topside module from the wave-induced loads, and specifically the torque, transmitted from the lifting vessel. Through theoretical derivations based on hydrostatics principles, a mathematical model of the topside module is established. We consider the effects of lifting load, tidal changes and the ballast water system on stability, and develop a stability analysis model for the dual-vessel system. The intact stability and loss-of-load stability under dual-vessel collaborative lifting conditions are analysed to verify compliance with stability requirements for lifting a 30,000 ton topside module. The results conclusively demonstrate that the proposed system with multiple motion-compensated lifting arms meets the stability performance needs for dual-vessel collaborative offshore assembly and disassembly operations.