Flexible Stinger for Spar Riser Curvature Control
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Solution Overview
Problem
Conventional bend limiters for steel catenary risers in spar-type offshore platforms are rigid and cannot optimally support dynamic motion, leading to excessive static and dynamic stresses due to abrupt curvature transitions and inability to pass through vertical riser guides.
Innovation Solution
A bend-limiting conduit or 'stinger' with progressively increasing flexibility and weight per unit length, formed from steel pipe sections with reduced wall thickness and weighted jackets, allowing gradual curvature transition and movement with the platform's dynamic motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional rigid bend limiter is used, then the riser curvature is limited, but the device cannot pass through vertical riser guides and cannot optimally support dynamic motion
Solution Approach 1:
The bend limiter is divided into multiple modular sections that can be connected together. Each section has a standardized connection interface allowing them to be assembled in different configurations. This segmentation enables the device to be transported and installed through vertical riser guides while maintaining its bend-limiting function.
Solution Approach 2:
The bend limiter incorporates dynamic elements that allow it to adapt to the motion of the floating platform. The modular sections can rotate and adjust relative to each other, enabling the device to accommodate dynamic movements while continuously controlling riser curvature and reducing stresses.
2Reliability
If a conventional fixed-geometry bend limiter is used, then some bending moment limitation is achieved, but the device cannot optimally support dynamic motion of the riser relative to the platform
Solution Approach 1:
The bend limiter transitions from a fixed-geometry structure to a dynamic modular system where sections can rotate and adjust. This allows the device to maintain optimal bend limitation while adapting to the continuous motion between the floating platform and the seabed, providing versatile support for varying operational conditions.
Solution Approach 2:
The modular sections can be configured with different geometric parameters to optimize performance for specific conditions. The ability to change the configuration and orientation of sections allows the bend limiter to adapt its characteristics to match the dynamic requirements of different operational scenarios.
3Ease of manufacture
If the riser makes an abrupt transition from catenary curve to straight vertical configuration, then installation is simpler, but static bending moments and dynamic stresses increase
Solution Approach 1:
The bend limiter introduces a gradual curved transition zone between the horizontal catenary section and the vertical riser section. This curved geometry distributes the bending moment along the transition length, reducing peak stresses while maintaining installation simplicity through standardized modular components.
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 stinger effectively reduces bending moments and stresses by controlling curvature through distributed weight and graduated stiffness, enabling better stress management and compatibility with vertical riser guides.
Implementation Method 1
The stinger effectively reduces bending moments and stresses by controlling curvature through distributed weight
Implementation Method 2
A bend-limiting conduit or 'stinger' with progressively increasing flexibility and weight per unit length, formed from steel pipe sections with reduced wall thickness
Data Source
AI summary
A bend-limiting conduit controls the curvature of a catenary riser extending from the seafloor as it enters the centerwell of a spar-type offshore platform through the keel of the platform. The conduit has a bore dimensioned to receive the riser, and it extends from an upper end constrained within the keel to a lower end disposed below the keel. The conduit has increasing flexibility and weight per unit length from the upper end to the lower end, which results in a lateral load being applied to the riser as it passes through the conduit, thereby causing a gentle and gradual transition in the riser from a curved configuration at the lower end of the conduit, to a straight configuration as it emerges from the upper end of the conduit.