Flexible Composite Pipe Sealing for Deepwater Corrosion Resistance
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Solution Overview
Problem
Hybrid flexible pipes used in deep water applications are prone to water infiltration and corrosion under high hydrostatic pressure, leading to potential leakage and irreversible damage due to the brittleness of the composite tubular structure and diffusion of acid gases.
Innovation Solution
A flexible pipe design with a sealing layer thickness of less than 15 mm, comprising a thermoplastic matrix reinforced with carbon fibers, where the sealing layer is either bonded or unbonded to the composite reinforcement structure, and formed by winding or extrusion, to enhance impermeability and resistance to corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick sealing layer is used to prevent water infiltration, then impermeability is improved, but the pipe weight increases and flexibility decreases
Solution Approach 1:
The patent employs a composite reinforcement structure comprising carbon fibers embedded in a thermoplastic matrix (such as PEEK). This composite structure provides both mechanical strength and impermeability without requiring excessive sealing layer thickness. The carbon fiber reinforcement enables the use of thinner sealing layers while maintaining structural integrity and resistance to water infiltration under high hydrostatic pressure.
2Strength
If metal reinforcement layers are used to increase strength, then resistance to hydrostatic pressure is improved, but corrosion resistance deteriorates due to sensitivity to acid gases
Solution Approach 1:
The patent replaces traditional metal reinforcement layers with a composite reinforcement structure consisting of carbon fibers in a thermoplastic matrix. Carbon fibers provide the necessary tensile strength to resist hydrostatic pressure at great depths without suffering from corrosion. The thermoplastic matrix (e.g., PEEK) further enhances corrosion resistance while maintaining mechanical properties, eliminating the corrosion issues associated with metal wires exposed to acid gases like H2S and CO2.
3Strength
If the composite tubular structure becomes brittle under high pressure, then strength is maintained, but reliability decreases due to potential leakage and irreversible damage
Solution Approach 1:
The patent utilizes thermoplastic materials such as PEEK that maintain their mechanical properties and flexibility under high hydrostatic pressure. Unlike some composite materials that become brittle under pressure, these thermoplastics retain their ductility and toughness, preventing catastrophic failure. The material parameters are selected to ensure the reinforcement structure remains flexible and resistant to both internal and external pressures, avoiding the brittleness problem.
4Weight of moving object
If lightweight composite materials are used to reduce pipe weight, then ease of installation is improved, but resistance to corrosion from acid gases deteriorates
Solution Approach 1:
The patent employs a composite reinforcement structure with carbon fibers in a thermoplastic matrix (such as PEEK). Carbon fibers are lightweight yet provide exceptional strength, while the thermoplastic matrix offers excellent chemical inertness and resistance to acid gases like H2S and CO2. This combination achieves both weight reduction for easier installation and superior corrosion resistance, outperforming traditional metal reinforcement while protecting against harmful chemical environments.
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 design significantly reduces water permeability and prevents corrosion, maintaining the integrity of the pipe under high hydrostatic pressure and extending its lifespan by limiting water infiltration and acid gas diffusion.
Implementation Method 1
The design significantly reduces water permeability and prevents corrosion, maintaining the integrity of the pipe under high hydrostatic pressure
Implementation Method 2
limiting water infiltration and acid gas diffusion
Data Source
AI summary
A flexible pipe designed to transport fluids that include, from the interior toward the exterior: an internal tubular sheath with an axis (A-A′) defining an internal passage for fluid circulation; a composite reinforcing structure applied around the tubular sheath and connected to the tubular sheath; at least one sealing layer made of thermoplastic material applied around the composite reinforcing structure; at least one ply of tensile armor, not connected to the sealing layer, the at least one ply of tensile armor ply comprising at least one armor element wound around the sealing layer; the thickness of the sealing layer being less than 15 mm.