Disconnectable Mooring Buoy for Shallow-Water Line Pull-In
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Solution Overview
Problem
Existing disconnectable mooring systems for offshore semi-submersible floating structures, such as floating offshore wind turbines, are cumbersome and costly due to the need to individually connect and disconnect multiple mooring lines and power cables, which is complicated by deep water operations and the risk of twisting and damage, especially when using submerged turret buoys.
Innovation Solution
A disconnectable mooring system with a buoy that supports mooring chains, allowing mooring lines to be connected and disconnected from shallow water, using a swivel-less design that applies tension from a single direction, reducing the need for swivels and minimizing environmental loads on the buoy, and incorporating a three-way connector for efficient mooring line pull-in.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple mooring lines and power cables are individually connected and disconnected, then the FOWT can be detached for maintenance or relocation, but the operation becomes long, expensive, and complex
Solution Approach 1:
The patent combines multiple mooring lines and power cables into a single integrated mooring buoy assembly. The buoy serves as a common connection point for all mooring lines, and the cables are routed through the buoy, allowing simultaneous connection or disconnection of the entire mooring system and power supply in one operation rather than individually connecting each line and cable separately
Solution Approach 2:
The mooring buoy acts as an intermediary device between the FOWT and the seabed anchors. It consolidates multiple connection points into a single interface that can be attached to or detached from the FOWT as one unit, simplifying the operational complexity while maintaining the functional separability needed for maintenance and relocation
2Strength
If mooring lines are pulled in from deep water, then proper tensioning is achieved, but the risk of twisting and damage increases
Solution Approach 1:
The mooring lines are pre-configured with the buoy attached at the appropriate depth before being paid out to the seabed anchors. This preliminary arrangement ensures that the lines are properly positioned and tensioned from the start, reducing the risk of twisting and damage during the tensioning operation compared to pulling lines in from a completely loose state in deep water
3Ease of operation
If a submerged turret buoy is used, then single-point mooring is achieved, but the buoy becomes large in deep water due to cable weight
Solution Approach 1:
The mooring system is segmented into multiple functional components: the buoy provides buoyancy and serves as the connection point, while the mooring lines extend separately to the seabed anchors. This segmentation allows the buoy to remain relatively small and manageable in size even in deep water, as it doesn't need to support the entire length of mooring lines or cables alone - their weight is distributed along their respective lengths to the seabed
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system enables rapid, safe, and cost-effective connection and disconnection of mooring lines and power cables, reducing the need for high-tension operations and minimizing risks, while maintaining structural stability and electrical continuity.
Implementation Method 1
a buoy (24) ... supporting the mooring chains (20b, 20c) deeper in the water; but avoids the requirement for swivels
Data Source
AI summary
A disconnectable mooring system for offshore semi-submersible floating structures. A disconnectable buoy has a number of mooring lines which include a buoy chain between the mooring chain and the buoy. The mooring chain and the buoy chain are connected via a three way mooring connector, with the third connection configured to pull the mooring connector to a mooring point on the structure. In a first configuration the buoy is disconnected and supports the mooring chains for recovery at shallow depths to be pulled in. In a second configuration, the mooring lines are pulled in via the mooring connectors thereby providing a spread mooring to the structure with the buoy chain left as a catenary between the buoy and mooring point.