Pre-tensioned Anti-swelling Layer for Flexible Subsea Pipes
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Solution Overview
Problem
Flexible underwater tubular pipes face challenges in resisting reverse end cap effects, which cause axial compression and radial swelling, leading to potential buckling and irreversible deformation, especially under high external pressures and varying curvature conditions, and existing solutions like aramid fiber reinforced tapes are costly and do not fully address lateral buckling issues.
Innovation Solution
The method involves pre-tensioning deformable materials used in the anti-swelling layer during winding, stretching them within their elastic limit to reduce radial swelling and improve resistance to axial compression, while maintaining the same maximum axial stress levels, thereby reducing the number of layers and material costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If aramid fiber reinforced tapes are used to reduce radial swelling, then the resistance to radial swelling is improved, but the manufacturing cost increases significantly
Solution Approach 1:
The patent changes the physical state and mechanical properties of the deformable material by applying controlled tension during winding, stretching it within its elastic limit. This parameter change allows the material to permanently resist radial swelling without requiring expensive aramid fibers, resolving the contradiction between swelling resistance and manufacturing cost
Solution Approach 2:
The patent applies preliminary action by pre-tensioning the deformable material during the winding process. This preliminary stretching within the elastic limit creates a permanent structural state that resists future radial swelling, achieving the same effect as expensive aramid tapes but with more economical materials
2Strength
If multiple layers of anti-swelling material are added to prevent buckling, then the resistance to lateral buckling is improved, but the device complexity and weight increase
Solution Approach 1:
The patent changes the mechanical parameters of the deformable material through controlled tensioning during winding. This creates a single-layer solution with enhanced properties that replaces multiple layers, reducing device complexity while maintaining or improving buckling resistance
Solution Approach 2:
The patent uses composite action by combining the deformable material's inherent properties with the applied tension state during winding. This creates a composite effect within a single layer that provides both structural support and anti-buckling properties, eliminating the need for multiple separate layers
3Strength
If the deformable material is stretched beyond its elastic limit, then the radial swelling resistance is maximized, but the material undergoes irreversible deformation and loses flexibility
Solution Approach 1:
The patent precisely controls the tension parameter during winding to stretch the material within its elastic limit. This parameter control achieves permanent swelling resistance through elastic deformation that recovers upon tension release, maintaining material flexibility while maximizing swelling resistance
Solution Approach 2:
The patent copies the effective behavior of expensive aramid tapes (high swelling resistance) using a different mechanism - controlled elastic deformation during winding. This achieves the same functional outcome without the negative consequences of plastic deformation or material brittleness
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 approach effectively reduces radial swelling and enhances resistance to axial compression and lateral buckling, improving the pipe's stability and reducing the risk of deformation without increasing material costs or weight, while maintaining similar resistance properties.
Implementation Method 1
stretching them within their elastic limit to reduce radial swelling
Implementation Method 2
improve resistance to axial compression
Data Source
Figure 1~2
Figure 3~6
AI summary
The invention relates to a method for manufacturing a flexible tubular underwater pipe (10). A sealed tubular structure (12, 14, 16) covered with at least one layer (18, 20) of sheathing wires is provided, and at least one continuous longitudinal element made of a deformable material is wound around said layer (18, 20) of sheathing wires into a helix having a short pitch so as to form a support layer (24). According to the invention, said at least one longitudinal element is wound with a longitudinal tension T0 so as to stretch said deformable material according to a relative elongation corresponding to a tensile stress s0 lower than the threshold value of the maximum elastic limit sE of said deformable material, said threshold value of the maximum elastic limit sE corresponding to a tensile stress beyond which the deformation of said material is irreversible.