Flexible Pipe End Piece Insert Design for Stress Reduction
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Solution Overview
Problem
Flexible pipe end pieces used in hydrocarbon transport across water bodies face challenges in withstanding high pressures, temperatures, and dynamic stresses, leading to potential resin block weaknesses and breakage, especially at the transition zones between frustoconical and cylindrical regions.
Innovation Solution
The end piece design incorporates an insert within the receiving chamber that contacts the internal surface of the cover, embedding the armor elements in a solid filler material, which forms a continuous block providing robust anchoring and reducing stress concentrations, along with a wedge effect for enhanced mechanical strength and resistance to creep at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the cover has a frustoconical region to anchor armor elements, then anchoring strength is improved, but the transition zone between frustoconical and cylindrical regions becomes fragile and prone to breakage
Solution Approach 1:
The invention divides the resin block into two distinct segments: a frustoconical first portion for anchoring armor elements and a cylindrical second portion for sealing. This segmentation allows each portion to be optimized for its specific function while reducing stress concentration at the transition zone, preventing resin block breakage under dynamic stresses.
Solution Approach 2:
The invention applies different geometric qualities to different regions of the resin block. The frustoconical first portion provides convergent walls for anchoring armor elements, while the cylindrical second portion provides parallel walls for sealing. This local differentiation optimizes each region's performance and reduces harmful stress concentrations at the transition.
2Strength
If armor elements are embedded in resin with friction and capstan effect, then anchoring is improved, but dynamic fatigue stresses cause resin block breakage over time
Solution Approach 1:
By segmenting the resin block into frustoconical and cylindrical portions, the invention creates a stress distribution that prevents concentration at the transition zone. This segmentation allows the resin block to withstand repeated dynamic fatigue stresses without breaking, extending service life while maintaining anchoring strength.
Solution Approach 2:
The cylindrical second portion with parallel walls acts as a cushioning element that prevents stress concentration before dynamic fatigue can cause breakage. This geometric design anticipates and mitigates the harmful effects of repeated bending and dynamic stresses during service.
3Force
If hooks are embedded in resin for mechanical blocking, then anchoring resistance to tension is improved, but resin block becomes vulnerable to breakage at transition zones
Solution Approach 1:
The segmented design with distinct frustoconical and cylindrical portions distributes the mechanical loads from embedded hooks away from the transition zone. This segmentation prevents stress concentration that would otherwise cause resin block breakage while maintaining effective mechanical blocking against tension.
Solution Approach 2:
The invention applies different geometric qualities locally: the frustoconical portion with convergent walls provides anchoring for hooks under tension, while the cylindrical portion with parallel walls provides structural support. This local differentiation maintains force resistance without compromising overall resin block strength.
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 design significantly enhances the mechanical strength and durability of the end piece, ensuring robust anchoring of armor elements and reducing the risk of resin block breakage under high-pressure and temperature conditions, while minimizing axial movement and fatigue, thereby improving the overall performance and longevity of the flexible pipe.
Implementation Method 1
The friction between the armor elements and the resin helps to anchor the armor elements in the end cap.
Implementation Method 2
The end sections of the armor elements have a helical trajectory. This helical trajectory generates a capstan effect which also contributes to retaining the armor elements in the end piece.
Implementation Method 3
The insert has a wedge shape and is disposed between the armor elements and the rear sealing assembly, with its longitudinal face bearing against the longitudinal face of the rear sealing assembly. The wedge effect helps distribute stress and prevent resin block breakage.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The end piece (14) comprises an insert (58) arranged in a receiving chamber (52) and contacting an inner surface (60) of a cover (51). The insert (58) defines an interior surface (88) converging from front to back towards the longitudinal axis (A-A'), a rear edge (94) of the converging interior surface (88) being located near an end section (34) of an armour element (29), a front edge (92) of the converging interior surface (88) contacting the inner surface (60) of the cover (51), in continuous engagement with the inner surface (60) of the cover (51), the converging interior surface (88) being located away from a plurality of armour elements (29) on at least one part of the length of the armour element (29) between the rear edge (94) and the front edge (92) of the converging interior surface (88), the solidified filling material (68) contacting the converging interior surface (88) between the rear edge (94) and the front edge (92) of the converging interior surface (88).