Flexible Pipe Helical Sealing Structure to Limit Gas Diffusion
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Solution Overview
Problem
Flexible pipes used for transporting oil and gas fluids in underwater environments face issues with gas diffusion through the pressure jacket, leading to corrosion of metal elements and premature failure due to the accumulation of gases like CO2, H2S, and methane, especially under high temperature and pressure conditions.
Innovation Solution
The internal reinforcing structure of the flexible pipe features helical interstices sealed by a sealing element that blocks the passage of small gas molecules, maintaining a low concentration of corrosive gases in the annular space, while allowing flexibility and resistance to hydrostatic pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the pressure jacket is used to contain oil and gas fluids, then the pipe can transport fluids under high pressure, but small gas molecules can diffuse through the pressure jacket and accumulate in the annular space, causing corrosion
Solution Approach 1:
A sealing element is introduced as an intermediary component between the internal carcass turns to block the diffusion path of gas molecules. The sealing element fills the interstices between carcass turns, preventing gas from migrating from the internal passage through the pressure jacket to the annular space, thus protecting against corrosion while maintaining pressure containment.
Solution Approach 2:
The sealing element is nested within the helical interstices formed by the adjacent turns of the internal carcass. This nested configuration allows the sealing element to occupy the gaps between carcass turns without disrupting the overall pipe structure, effectively blocking gas diffusion paths while maintaining the pressure-containing function of the pressure jacket.
2Strength
If the internal carcass is made with short pitch helical winding to absorb radial crushing forces, then the pipe can resist hydrostatic pressure, but helical interstices are created that allow gas diffusion
Solution Approach 1:
The sealing element serves as a mediator that fills the helical interstices between internal carcass turns. It blocks the gas diffusion paths created by the short pitch winding configuration while maintaining the structural integrity and radial crushing resistance of the internal carcass. The sealing element is positioned within the interstices without compromising the load-bearing capability of the carcass.
3Adaptability or versatility
If the pipe structure is made flexible to allow bending and movement, then the pipe can be installed and operated in various configurations, but gas can accumulate in the annular space leading to premature failure
Solution Approach 1:
The sealing element acts as a protective intermediary that prevents gas accumulation in the annular space, thereby eliminating the corrosion mechanism that would otherwise lead to premature failure. This allows the pipe to maintain its flexibility and adaptability for various installation configurations without compromising reliability, as the sealing element continuously blocks gas diffusion regardless of pipe bending or movement.
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 gas diffusion, minimizing corrosion and enhancing the structural integrity of the flexible pipe, ensuring durability and reliability under high pressure and temperature conditions.
Implementation Method 1
the sealing element closes at least a portion of these helical interstices to block the circulation of the petroleum and/or gas fluid through the internal reinforcing structure
Data Source
Figure 1~2
Figure 3~4B
Figure 5A~5C
AI summary
The invention relates to a flexible pipe for transporting a gas and/or petroleum fluid and intended to be submerged within a body of water, comprising, from the outside to the inside of said flexible pipe: - an external sealing sheath intended to limit the penetration of water from the body of water into the flexible pipe, - at least one external reinforcing structure intended to reinforce the flexible pipe wtih respect to internal radial forces and/or tensile forces, - an internal protective sheath (6), - an annular space delimited by the external sheath and the internal sheath (6), the external reinforcing structure being arranged within said annular space, - a tubular internal reinforcing structure (8) intended to reinforce the flexible pipe with respect to external radial forces exerted on the flexible pipe, comprising at least one helical gap (10) and at least one sealing element (11) intended to limit the passage of the gas and/or petroleum fluid from the internal passage to the annular space, said sealing element (11) being wound in a helix within at least one helical gap (10). The invention makes it possible to reduce the corrosion of the external reinforcing structure.