Floating Offshore Structure Dynamic Buoyancy Control
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Solution Overview
Problem
Floating offshore structures that rely on excess buoyancy for stability require high-tension mooring lines, which are heavy, expensive, and unstable under varying loads, necessitating a solution to control tension and stability effectively.
Innovation Solution
A method and system that vary the mass and center of gravity of the structure by controlling the water level in water tanks, allowing for dynamic adjustment of excess buoyancy and mooring line tension in response to loads, using sensors and a control system with one-way valves and pumps to manage water distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If high excess buoyancy is provided to ensure stability under varying loads, then stability is improved, but mooring line tension increases causing heavier and more expensive cables and structure
Solution Approach 1:
The patent applies dynamics by making the buoyancy force adjustable rather than fixed. The buoyancy structure includes variable buoyancy elements (such as adjustable ballast tanks or inflatable chambers) that can dynamically change their buoyancy contribution based on real-time load conditions, wave states, and operational requirements. This allows the system to optimize the balance between stability and mooring line tension dynamically, rather than designing for maximum static buoyancy.
Solution Approach 2:
The patent changes the parameter of buoyancy force from a constant design value to a variable parameter that can be adjusted during operation. By controlling the amount of buoyancy provided by the buoyancy structure (through ballast adjustment, air pressure changes, or selective activation of buoyancy modules), the system can adapt to varying loads and environmental conditions, reducing excessive tension in mooring lines while maintaining adequate stability.
2Reliability
If high tension is maintained in mooring lines for stability, then reliability is improved, but the structure and cables become heavier and more expensive
Solution Approach 1:
The system dynamically adjusts buoyancy to maintain adequate stability reliability only when needed, rather than maintaining constant high tension. The control system monitors load conditions, wave states, and stability margins, activating additional buoyancy or adjusting ballast only when stability requirements demand it, thereby reducing the required weight of mooring lines and structural components.
Solution Approach 2:
By making buoyancy a variable parameter, the system can operate with lower average mooring line tension while maintaining peak stability reliability when required. This parameter adjustment allows for optimization of the weight-strength-reliability triangle, reducing cable and structure weight while preserving reliability through active control rather than static over-design.
3Stability of the object's composition
If high excess buoyancy is used to maintain stability, then stability is improved, but all other parts of the structure must be dimensioned accordingly becoming heavier and more expensive
Solution Approach 1:
The patent introduces dynamic buoyancy control that allows the structure to adapt its stability characteristics in real-time, eliminating the need for static over-dimensioning of all structural components. The control system adjusts buoyancy based on actual operational conditions, allowing for more efficient structural design that doesn't require maximum strength margins for all parts simultaneously.
Solution Approach 2:
By changing buoyancy from a fixed parameter to a variable one, the system allows for optimized structural dimensioning. Components can be designed for average or typical load conditions rather than maximum extreme conditions, reducing overall structure weight and complexity while the active buoyancy control compensates during critical high-load scenarios.
4Reliability
If multiple mooring lines are used to distribute stability, then reliability is improved, but the cost increases significantly
Solution Approach 1:
The patent uses dynamic buoyancy adjustment to enhance the effectiveness of each individual mooring line. By actively controlling buoyancy distribution, the system can optimize load sharing among mooring lines, allowing fewer lines to achieve the same stability reliability that would require many more lines in a passive static system.
Solution Approach 2:
By making buoyancy a controllable parameter, the system increases the efficiency and load-bearing capability of each mooring line. This allows for reduction in the total quantity of mooring lines needed while maintaining or improving reliability, as each line operates under more optimized and controlled conditions rather than static fixed loads.
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
This approach enhances stability and reduces costs by allowing for adaptive control of tension in mooring lines, avoiding resonance and maintaining structural integrity under varying loads, while providing flexibility and precision in mass and center of gravity adjustments.
Implementation Method 1
the buoyancy structure providing an excess buoyancy force to support the structure
Implementation Method 2
varying the mass and/or the centre of gravity of the floating offshore structure by varying the quantity of water in one or more of the water tanks
Implementation Method 3
gravity anchors on the seabed
Data Source
Figure 1a
Figure 1b
Figure 1c
AI summary
Methods for controlling tension in mooring lines of a floating offshore structure having a buoyancy structure including one or more water tanks and the buoyancy structure providing excess buoyancy are provided. The methods comprise varying the mass and/or the centre of gravity of the floating offshore structure by varying the quantity of water in one or more of the water tanks. Also, floating offshore structures are disclosed, the structures comprising a buoyancy structure having one or more floater tanks providing excess buoyancy, and a plurality of tensioned mooring lines, and further comprising a control system for increasing and decreasing a quantity of water in one or more of the floater tanks. Also, possible uses of floating offshore structures are provided wherein under standard operating conditions, the floater tanks are at least partially filled with water.