Composite Enhanced Metallic Drilling Riser Preloading
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Solution Overview
Problem
Existing composite enhanced metallic drilling riser systems face challenges in effectively transferring and managing axial loading, which is essential for achieving a 50% weight reduction while maintaining structural integrity and supporting hoop loading.
Innovation Solution
The system employs a segmented hyperboloid shaped profile with adjustable jack bolts and a ratcheting thread mechanism to preload the composite shell and metallic cylinder, ensuring balanced tensile and compressive loads, and an alternate embodiment uses a pressure port and inwardly biased C-ring to maintain pre-load, allowing for efficient load distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a composite overwrap is applied to a metallic tubular, then the hoop characteristics are improved and riser weight is reduced by approximately 30%, but the ability to carry axial loading is insufficient to achieve the required 50% weight reduction
Solution Approach 1:
The patent applies preliminary action by pre-loading the composite overwrap during installation. The hyperboloid-shaped profile is used to apply axial compression to the metallic tubular and tensile pre-stress to the composite overwrap before the riser enters service. This pre-loading ensures the composite is immediately capable of carrying axial loads from the outset, enabling the 50% weight reduction target to be achieved without compromising axial load carrying capacity.
2Weight of moving object
If the composite overwrap is pre-loaded to carry axial loading, then the weight reduction target of 50% can be achieved, but problems exist in transferring axial loading from the metallic tubular to the composite
Solution Approach 1:
The patent employs spheroidality by using a hyperboloid-shaped profile (a curved, three-dimensional geometric form) to facilitate load transfer. This curved profile distributes axial loads smoothly from the metallic tubular to the composite overwrap through a gradual transition zone, avoiding stress concentrations and ensuring reliable load transfer. The hyperboloid geometry enables efficient stress distribution while maintaining the integrity of both the metallic and composite components.
3Reliability
If a segmented hyperboloid shaped profile is used for preloading, then reliable pre-loading of composite and metallic components is achieved, but the device complexity increases with jack bolts and adjustment mechanisms
Solution Approach 1:
The patent applies self-service by designing the hyperboloid-shaped profile to automatically generate the required pre-loading forces through its geometric configuration. The segmented hyperboloid sections, when assembled, create inherent mechanical leverage that applies axial compression to the metallic tubular and tensile pre-stress to the composite overwrap without requiring external active control systems. The jack bolts and adjustment mechanisms are designed to be simple, manual devices that set the pre-load once during installation, after which the system maintains itself through its own structural geometry.
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 solution enables reliable pre-loading of the composite and metallic components, optimizing load distribution and enhancing the fatigue performance of the drilling riser system, thereby achieving the required weight reduction while ensuring structural integrity.
Implementation Method 1
Both halves of the hyperboloid shape are capable of axial movement by adjusting jack bolts connected to one of the hyperboloid halves
Implementation Method 2
As the other hyperboloid half moves axially away from the restricted half, the movement simultaneously generates the composite pre-load and the metallic cylinder pre-load
Implementation Method 3
An inwardly biased 'C-ring' is located at the vertical plane of the two hyperboloids, and moves radially into the axial gap created between thehyperboloid halves
Data Source
Figure 1~2
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Figure 5~6
AI summary
An offshore composite enhanced metallic drilling riser (20) is equipped to enable preloading of the composite shell (37) and the metallic riser (21). A riser (20) has steel end connectors (22) and a continuous metallic inner liner (21), encased in a composite shell (37). A segmented hyperboloid shaped profile (26, 27) is located near each of the end fittings (22) for preloading of the composite (37) and the metallic riser (21). In one version, both halves of the hyperboloid shape (26, 27) are capable of axial movement by adjusting jack bolts (33) connected to one of the hyperboloid halves (27). One of the halves (26) is limited in axial movement while the other half (27) moves axially away from the restricted half (26), the movement simultaneously generates the composite pre-load and the metallic riser pre-load. The other version uses fluid pressure between mating faces of the segments (47, 49) to push them apart.