Flexible Pipe Intermediate Sheath High-Pressure Fatigue
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional flexible pipes used for conveying fluids at high pressures in dynamic applications, such as deep water hydrocarbon extraction, suffer from fatigue and fatigue-fretting phenomena, which reduce their mechanical properties and longevity.
Innovation Solution
Incorporating an intermediate polymer sheath between the inner and outer sheaths to confine an inner fluid at high pressure, which reduces axial and radial stresses on the pipe layers, and using a pressure vault with a V-shaped wire and aramid or composite strips to enhance mechanical strength, along with spiral-wound armours to manage stress angles effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If traditional flexible pipe construction is used for high-pressure fluid conveyance, then the pipe can convey fluid at high pressure, but fatigue and fatigue-fretting phenomena occur on the pressure vault and spiral hoop layer, reducing mechanical properties and longevity
Solution Approach 1:
The pipe is divided into multiple functional layers with distinct roles: the inner sheath for fluid containment, the intermediate sheath for structural support and stress distribution, and the outer sheath for protection. This segmentation allows each layer to be optimized for its specific function, with the intermediate sheath specifically designed to reduce fatigue on pressure-bearing components
Solution Approach 2:
The pipe employs composite construction combining polymer materials (inner and outer sheaths made of flexible polymer) with metal or composite armours (spiral hoop layer and longitudinal armours). This composite structure leverages the flexibility and corrosion resistance of polymers alongside the strength and fatigue resistance of metal/composite armours, creating a synergistic system that withstands high pressure while resisting fatigue
2Length of moving object
If the pipe length exceeds 200m for deep water exploitation, then the pipe can reach deep reservoirs, but differential pressure for reinjection becomes extremely high (above 400-700 bars)
Solution Approach 1:
The pipe design incorporates dynamic flexibility through the polymer sheaths that can accommodate bending and movement, allowing the pipe to maintain structural integrity over lengths exceeding 200m while withstanding the dynamic pressure variations encountered during deployment and operation in deep water environments
Solution Approach 2:
The intermediate sheath acts as a mediator between the inner pressure-containing sheath and the outer protective sheath. It distributes and manages the extreme differential pressures (400-700 bars) by providing an additional structural barrier that prevents stress concentration on any single layer, enabling the pipe to handle high-pressure reinjection over long distances
3Stress or pressure
If absolute pressure at the bottom of the pipe reaches approximately 1300 bars, then the pipe can operate at deep water depths, but the mechanical strength requirements become extremely demanding
Solution Approach 1:
The composite structure combines the compressive strength of metal/composite armours with the flexibility and pressure distribution capabilities of polymer sheaths. The intermediate sheath specifically reinforces the structure to handle the 1300 bar absolute pressure by distributing loads across multiple layers, preventing any single material from being overwhelmed by the extreme pressure
Solution Approach 2:
The pipe employs a nested multi-layer construction where the inner sheath is contained within the intermediate sheath, which is in turn contained within the outer sheath. Each nested layer provides additional structural support and pressure management, with the intermediate sheath serving as a critical reinforcement layer that enables the pipe to withstand the 1300 bar absolute pressure at deep water depths
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 solution significantly reduces fatigue and fatigue-fretting phenomena, allowing the flexible pipe to maintain strength and longevity under high-pressure conditions, exceeding current pressure limits and extending service life.
Implementation Method 1
the inner fluid being confined in the inner annular space at a pressure above 50 bars... which reduces axial and radial stresses on the pipe layers
Data Source
AI summary
A pipe (10) for conveying a fluid, including an inner sheath (20), at least one layer (34, 36) of inner armors, arranged outside the inner sheath (20) and an outer protection sheath (22), positioned outside each layer (34, 36) of inner armors. It includes an inner fluid, received between the inner sheath (20) and the outer sheath (22). The pipe includes an intermediate polymer sheath (24), interposed between the inner sheath (20) and the outer sheath (22), the intermediate sheath (24) and the inner sheath (20) delimiting an inner annular space (26) between them for receiving the inner fluid. The inner fluid is confined in the inner annular space (26) at a pressure above 50 bars.