A diverless chain connector for the high integrity connection of mooring legs

Abstract

This paper presents a new design of chain connector that allows disconnection of the mooring line, and inspection and possible replacement of the chain connector's articulation bushes, without the assistance of divers. This design brings dual benefits: Reduced risk of mooring line failure caused by unexpected wear or damage to chain connector articulations, which could not have been inspected with traditional chain connector designsIncreased safety by removing the need for diver intervention. The paper presents the development of the chain connector, including the latching system that enables connection and disconnection without diver assistance. The development has been performed following a structured process with milestones. The main development steps have been the concept engineering phase, an extensive phase of sub-component testing, a phase of assembly prototype testing at a reduced scale, realization of detailed engineering phase of the component, and the development of full scale prototype test rig. Chain connectors are a key component of any mooring system, transferring the load from the mooring leg to the FPU. The chain connector also forms an articulation between the mooring leg and structure, and its reliable behaviour is fundamental to avoiding Out-of-Plane Bending (OPB) fatigue failure of the chain links. The described development process and especially the system testing demonstrate the functionality of the diverless chain connector having as aim the high integrity of the mooring legs. Furthermore, it allows assessing the envelope of its connection and disconnection functionality, given different mooring line configurations. Testing provides complete and reliable results of connection and disconnection functionality for different values of in plane and out of plane angles, and pretension. In addition to that, the testing results allow sizing the installation winches adapted to different mooring line configurations. The trend towards offshore developments in increasing harsh environments is leading to increased technical challenges in ensuring the integrity of Floating Production Units. In parallel, the design life of these systems is increasing above 20 years, and up to 50 years. The ability to monitor the condition of the chain connectors, and to safely maintain or replace any element in case of unpredicted aging effects is the benefit given by the component development described here.