Roll Stability Evaluation of the Floating Multi-Body System at TML (Twin Marine Lifter) Operation

Twin Marine Lifter (TML) is a specially designed heavy-lifting system consisting of two vessels for offshore installation & decommissioning. The system is developed multi-functionally in the heavy lifting sector to be cost-effective. Conceptually, they can be used in tandem for the platform installation and decommissioning of both topsides and jackets or carrying out by single lift configuration for other offshore construction tasks such as wind farm equipment installation. These flexible and versatile solutions to a wider range of potential clients also constrain the shape and the main particulars of the vessels, which results in extra challenges coming from the stability properties of the specific multi-body system compared to traditional single vessel operations, and there are few literatures could be referred to. In view of the highly complicated motions in the multi-body system at lifting phases, the topological model reflecting the flexible connections among bodies in system during the operation is constructed to obtain theoretical estimation of the roll stability of the targeted decommission topside. The virtual prototype technology based on ADAMS (Automatic Dynamic Analysis of Mechanical Systems) considering the coupling boundary of control factors including capability of the DP power and the compensation system are introduced by experimental data to correctly estimate the influence of multi-body motions on the roll stability of the topside in a synchronized way. A fast analysis and prediction methodology on the roll stability limiting criteria of the multi-body system is proposed. It would provide a safety guarantee and technical support for the design of the specific apparatus and the successful decision making on schemes of a new type of offshore operation mode.