Extended Pontoons for Subsea Riser Buoyancy Stability
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Solution Overview
Problem
Subsea riser support buoys in BSR systems face challenges in maintaining stability and minimizing tether size and number while avoiding clashes with riser and jumper pipes, especially in congested spaces, which affects dynamic behavior and fatigue life.
Innovation Solution
The addition of extended pontoons of negative or neutral buoyancy at the corners of the buoy, which increase the spacing between tethers and rotational moment, allowing for the same number and size of tethers as in a smaller buoy, while adjusting the tether attachment points to avoid clashes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If tethers are attached to outer side walls of the buoy near corners to maximize spacing from pipes, then risk of clashing with pipes is reduced, but the buoy requires larger dimensions and increases the footprint in congested spaces
Solution Approach 1:
The patent extends the buoy in the longitudinal direction by adding extended pontoons, moving tether attachment points from the lateral width dimension to the longitudinal length dimension. This allows tethers to be spaced further from pipes along the length of the buoy rather than requiring greater width, thereby reducing the buoy's lateral footprint in congested horizontal spaces while maintaining adequate clearance from riser and jumper pipes.
Solution Approach 2:
The extended pontoons are designed and positioned in advance to predetermined locations along the longitudinal axis of the buoy, establishing fixed attachment points for tethers before deployment. This preliminary configuration ensures optimal spacing between tethers and pipes is achieved through careful design rather than post-installation adjustment, preventing clashes while minimizing the buoy's overall footprint.
2Stability of the object's composition
If additional stabilizing measures such as guy lines or interconnections are applied to the buoy, then stability in extreme conditions is improved, but cost and structural weight increase
Solution Approach 1:
The patent employs dynamically adjustable tensioning devices at each tether attachment point on the extended pontoons, allowing the tension in each tether to be independently controlled and adjusted. This dynamic adjustment capability enables the buoy to maintain optimal stability in varying sea conditions without requiring excessive structural reinforcement or additional stabilizing structures, thereby avoiding increased structural weight while adapting to different operational scenarios.
Solution Approach 2:
The tensioning devices allow modification of the tension parameter in each tether individually, enabling fine-tuning of the buoy's stability characteristics. By adjusting these parameters, the system achieves enhanced stability in extreme conditions through optimized force distribution rather than through added structural mass, thus avoiding the weight penalty associated with over-engineered static stabilization structures.
3Device complexity
If the number and size of tethers are reduced to minimize cost and complexity, then device complexity is reduced, but the buoy becomes more susceptible to excessive movement in extreme conditions
Solution Approach 1:
The extended pontoons are designed in advance to provide optimally positioned attachment points that maximize the lever arm and stabilizing moment for each tether. This preliminary geometric optimization allows each tether to contribute more effectively to buoy stability, meaning fewer or smaller tethers are required to achieve the same stabilizing effect, thereby reducing device complexity while maintaining stability performance.
Solution Approach 2:
The adjustable tensioning devices enable dynamic optimization of tether force distribution, allowing the system to maximize the stabilizing effect of each individual tether by adjusting its tension according to loading conditions. This dynamic capability compensates for having fewer or smaller tethers, as each tether can be optimally utilized to resist excessive buoy movement, maintaining stability without increasing the number or size of tethers.
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 design enhances the dynamic behavior and fatigue life of the tether system, improves robustness for payload increases, and reduces structural weight by placing tethers further from ballast tanks, thereby increasing the endurance of the BSR system.
Implementation Method 1
pontoons of negative or neutral buoyancy that extend lengthwise beyond the positive buoyancy of the riser support member and the jumper support member
Data Source
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AI summary
A subsea riser support buoy comprises a riser support member and a jumper support member that extend generally parallel to each other and that define a lengthwise direction extending between them across the buoy. Pontoons extend lengthwise beyond the riser support member and the jumper support member to provide attachment points for connecting tethers to the buoy. In this way, the attachment points are spaced more widely than lengthwise extremities of the riser support member and the jumper support member, beneficially altering the dynamic behaviour of the buoy and especially its pitch characteristics.