Tube Buoyancy Can System for Riser Tensioning
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Solution Overview
Problem
Current buoyancy can systems for top-tensioned risers face challenges in deep water and harsh ocean environments, where increased weight and dynamic loads require larger, more complex, and expensive tensioner systems, limiting operational flexibility and increasing costs.
Innovation Solution
A tube buoyancy can system that uses tubular cans with a pressurized gas system to adjust buoyancy and tension load by ballasting with seawater or de-ballasting with pressurized gas, allowing for flexible tensioning of top-tensioned risers without significantly affecting the natural heave period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional buoyancy can systems are used to support multiple risers, then the tensioning capacity is sufficient, but the buoyancy can must be ballasted to prevent over-tensioning, which shifts the natural heave period into a range with appreciable wave energy, resulting in increased dynamic loads
Solution Approach 1:
The patent applies dynamics by making the buoyancy can system adjustable rather than fixed. The system can transition between different operational states (ballasted and de-ballasted) to adapt to varying tension requirements. This allows the natural heave period to be adjusted out of the dangerous wave energy range while maintaining sufficient tensioning capacity for multiple risers.
Solution Approach 2:
The patent changes the physical parameters of the buoyancy can system by controlling the amount of ballast water present. By adjusting the ballast level, the system modifies its natural heave period and tensioning capacity. This parameter change allows the system to operate in optimal conditions, avoiding resonance with wave energy while providing adequate tension for the required number of risers.
2Object-affected harmful factors
If the buoyancy can is de-ballasted to reduce dynamic loads, then the natural heave period moves out of the wave energy range, but the tensioning capacity is reduced, requiring additional dummy risers
Solution Approach 1:
The system uses dynamic adjustment of ballast levels to achieve the desired operational state. When dynamic loads are a concern, the system can be de-ballasted to move the natural heave period out of the wave energy range. When tensioning capacity is needed, ballast can be added. This dynamic capability eliminates the need for permanent dummy risers while maintaining safety.
Solution Approach 2:
The patent utilizes parameter changes in the ballast configuration to achieve different operational requirements. By controlling the ballast level, the system can adjust both the natural heave period and tensioning capacity as needed. This flexible parameter adjustment allows the system to meet both dynamic load requirements and tensioning capacity requirements without permanent compromises.
3Object-affected harmful factors
If additional dummy risers are added to maintain natural heave period, then the dynamic loads are minimized, but the system complexity and costs increase
Solution Approach 1:
Instead of adding permanent dummy risers to maintain natural heave period, the patent uses a dynamic ballast adjustment system. The buoyancy can can be de-ballasted when needed to achieve the desired natural heave period, eliminating the need for permanent additional risers. This dynamic approach reduces system complexity while maintaining the benefit of optimized natural heave period.
Solution Approach 2:
The patent changes the operational parameters of the existing buoyancy can system by adjusting ballast levels, rather than adding permanent structural elements. This parameter change approach achieves the desired natural heave period without increasing system complexity. The system uses the existing buoyancy can with variable ballast rather than requiring additional dummy risers.
4Force
If larger tensioner systems are used to handle increased weight and dynamic loads, then the tensioning capacity is sufficient, but the systems become larger, more complex, and expensive
Solution Approach 1:
The patent uses parameter changes in the buoyancy can system to achieve the required tensioning capacity without increasing system size. By adjusting ballast levels, the system can optimize its natural heave period and tensioning characteristics. This allows a smaller, simpler buoyancy can system to perform the function of a larger, more complex tensioner system.
Solution Approach 2:
The buoyancy can system is self-regulating through its ballast mechanism. The system uses its own weight and buoyancy characteristics to provide the required tensioning capacity without requiring external active control systems. This self-service capability eliminates the need for complex hydraulic actuators or active control systems, resulting in a simpler, more cost-effective design.
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 adjustable tensioning of risers, reducing the need for additional dummy risers and minimizing dynamic loads, thereby reducing costs and maintaining operational efficiency in deep water environments.
Implementation Method 1
a pressurized gas system configured to selectably inject pressurized gas into the tubular can
Implementation Method 2
When the opening is closed and pressurized gas is injected into the tubular can, the tubular can is de-ballasted of seawater
Implementation Method 3
an open lower end configured to allow seawater to flow freely into and out of the tubular can
Implementation Method 4
When the opening is open, the tubular can is ballasted by seawater
Data Source
AI summary
A tube buoyancy can system for tensioning a top tension riser. In some embodiments, the system includes a tubular can coupled to the top tension riser and a pressurized gas system configured to selectably inject pressurized gas into the tubular can. The tubular can includes an enclosed upper end having at least one closeable opening therethough, an open lower end configured to allow seawater to flow freely into and out of the tubular can, and an inner surface extending therebetween. The inner surface is devoid of structural obstructions which substantially inhibit the free flow of seawater through the lower end. When the opening is open, the tubular can is ballasted by seawater. When the opening is closed and pressurized gas is injected into the tubular can, the tubular can is de-ballasted of seawater.