Tapered Riser Tension Joint for Offshore Motion Compensation
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Solution Overview
Problem
Top-tensioned risers on offshore platforms face challenges in accommodating lateral movements due to wind and waves, leading to vertical displacement and increased loads on tensioning systems, which existing solutions like motion compensators and buoyancy cans do not fully address, especially in the absence of keel joints that can limit movement and affect hydrodynamic properties.
Innovation Solution
A ram-type tensioning system with a tapered tension joint and rollers that react to bending moments and shear forces, eliminating the need for a keel joint by distributing loads and providing stability through a combination of hydraulic cylinders and flexible tension rings, allowing for reduced deck structure requirements and efficient motion compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a motion compensator is included in the top-tensioning riser system, then constant tension is maintained on the riser, but the device complexity increases
Solution Approach 1:
The patent extracts the motion compensation function from a complex active motion compensator and implements it through the passive geometric configuration of the keel joint and riser arrangement. The keel joint's specific geometry naturally accommodates platform motion without requiring active sensing or actuation systems, thereby maintaining constant tension while reducing device complexity.
Solution Approach 2:
The keel joint is designed to automatically compensate for platform motion through its geometric configuration. As the platform moves vertically, the keel joint's angled structure self-adjusts the riser angle and tension distribution, providing passive motion compensation without requiring external control systems or additional active components.
2Adaptability or versatility
If buoyancy cans are deployed around the riser, then the riser is kept afloat and flexible pipe can accommodate facility movements, but the device complexity and weight increase
Solution Approach 1:
The patent removes the need for buoyancy cans by integrating the motion accommodation function into the rigid riser system itself through the keel joint configuration. The keel joint's geometric design allows the rigid riser to naturally adapt to platform movements and maintain proper alignment, eliminating the need for separate buoyancy devices.
Solution Approach 2:
Instead of using flexible pipe with buoyancy cans to accommodate movement, the patent inverts the approach by using a rigid riser with a specially designed keel joint that passively adapts to movement through its geometry. This inversion maintains the benefits of motion accommodation while preserving the advantages of rigid piping.
3Object-affected harmful factors
If a keel joint is used to limit movement, then hydrodynamic properties are improved, but the manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by concentrating the complex geometric features specifically at the keel joint location where hydrodynamic performance is critical. The keel joint's angled configuration and specific dimensions are optimized for hydrodynamic efficiency, while the rest of the riser system maintains simple, easy-to-manufacture cylindrical geometry. This localized approach achieves improved hydrodynamics without requiring complex manufacturing throughout the entire riser system.
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 tapered tension joint and roller support system effectively resist bending and shear loads, reducing the need for additional structural support, minimizing deck loads, and maintaining constant tension without the need for a keel joint, enhancing the efficiency and stability of top-tensioned riser systems on floating platforms.
Implementation Method 1
at least one cylinder coupled to the traveling trolley structure on one end
Implementation Method 2
The tension joint is supported laterally by rollers below the tension ring
Implementation Method 3
The tapered tension joint and roller support system effectively resist bending and shear loads
Data Source
Figure 1
Figure 2A~2B
Figure 2C
AI summary
A top-tensioned riser (TTR) is supported by a tensioning system on the deck of a floating platform. The tension ring may include an elastomeric layer which permits small angular and lateral displacements of the tension joint. The tension joint comprises a tapered section to resist the bending moment and shear imposed by the vessel's motion. The riser tension joint may be supported laterally by rollers below the tension ring. The rollers react on the tapered section when the riser strokes up and down. The tapered section may be engineered to maximize the use of the tension joint, and to reduce bending moment and shear loads imposed on the tensioning system. In certain embodiments, there may be a small gap between the rollers and the tapered section. In certain other embodiments, the rollers may be spring-loaded to increase the stability of surface equipment on the upper terminus of the riser.