Passive Buoyancy Unit Flooding for Subsea Structure Launch
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Solution Overview
Problem
Existing methods for launching elongate subsea structures, such as pipeline bundles, face challenges in varying buoyancy during different stages of the launch procedure, particularly in deep water, where conventional buoyancy reduction methods are complex and impractical, especially when requiring precise control to avoid surface wave fatigue.
Innovation Solution
A passive variable buoyancy device, such as an open-topped caisson with predetermined apertures, is attached to the structure, which automatically floods and reduces buoyancy as it submerges, providing initial lift during launch and automatically sinking to prevent excessive buoyancy in deeper water, thus minimizing wave exposure and operational complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional buoyancy reduction methods are used in deep water, then buoyancy can be reduced, but the methods become complex and impractical
Solution Approach 1:
The buoyancy unit is designed to automatically flood and reduce its own buoyancy through predetermined apertures as it submerges, without requiring external mechanical intervention or complex control systems. The structure serves itself by using the submersion process to trigger the buoyancy reduction naturally.
Solution Approach 2:
The patent replaces complex mechanical buoyancy reduction systems with a passive hydrostatic system. Instead of using mechanical pumps, valves, or active control mechanisms, the design relies on water pressure and gravity to naturally flood the buoyancy unit through apertures as it submerges, substituting a simple passive system for a complex active one.
2Ease of operation
If the structure is towed near the surface, then towing is easier to manage, but surface water dynamics generate fatigue in the pipeline bundle
Solution Approach 1:
The buoyancy of the structure is dynamically adjusted during the towing operation. The structure transitions from a positively buoyant state near the surface to a negatively buoyant state in deeper water as the buoyancy unit floods, allowing the towing depth and characteristics to change dynamically to avoid wave fatigue while maintaining ease of management.
Solution Approach 2:
The patent changes the physical parameter of buoyancy from positive to negative as the structure submerges. This parameter change allows the structure to transition from surface-towing conditions (easier to manage but high wave exposure) to deep-water towing conditions (more protective but harder to control), effectively moving the structure to a more favorable operational regime.
3Object-affected harmful factors
If towing depth is increased to protect from surface waves, then wave fatigue is reduced, but controlling the bundle unit becomes more challenging
Solution Approach 1:
The buoyancy unit undergoes a periodic transformation from positively buoyant to negatively buoyant as it submerges and floods through its predetermined apertures. This periodic change in buoyancy characteristics facilitates the transition to deeper towing depths by naturally reducing the structure's tendency to surface, making deep-water towing more controllable.
4Stability of the object's composition
If buoyancy is not reduced in later stages of launch, then the structure remains supported, but excessive buoyancy causes the structure to float at or near the surface
Solution Approach 1:
The buoyancy unit is designed with predetermined apertures positioned at specific heights that will be submerged at appropriate stages of the launch procedure. This preliminary design ensures that as the structure is launched and the buoyancy unit submerges to a predetermined depth, water automatically enters through the apertures and reduces buoyancy before the structure reaches deep water, preventing excessive buoyancy and surface floating.
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 method simplifies buoyancy management by automatically adjusting buoyancy during the launch phase, reducing structural fatigue and operational complexity, allowing for controlled submersion and towing without mechanical intervention, enhancing safety and efficiency in deep water environments.
Implementation Method 1
providing buoyant support to the structure by displacing water with a hollow buoyancy unit that applies buoyant upthrust to the structure
Implementation Method 2
by lowering the buoyancy unit in the water to bring at least one permanently open aperture of the buoyancy unit beneath a surface level of the water, flooding the buoyancy unit with water through the or each permanently open aperture to reduce the buoyant upthrust applied to the structure
Data Source
Figure 1~2
Figure 3a~3c
Figure 4a~4c
AI summary
A method of launching an elongate subsea structure such as a pipeline bundle unit into water comprises providing buoyant support to the structure by displacing water with a hollow buoyancy unit that applies buoyant upthrust to the structure. By lowering the buoyancy unit in the water to bring a permanently open aperture of the buoyancy unit beneath a surface level of the water, the buoyancy unit is flooded with water through the or each permanently open aperture to reduce the buoyant upthrust applied to the structure.