Flexible Pipe Outer Layer for Gas Venting and Water Blocking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Flexible pipes used for transporting hydrocarbons in underwater environments face corrosion issues due to gas diffusion and water ingress, leading to stress corrosion of metallic armor wires, and increasing the outer sheath thickness is not entirely effective in preventing corrosion while increasing manufacturing costs.
Innovation Solution
A flexible pipe design featuring a polymeric internal sheath, tensile armor layers, and an external layer with a thickness between 1/125 and 1/75 of the internal diameter, composed of a polymer matrix reinforced with reinforcing elements wound at a specific angle to promote gas diffusion outwards and prevent water ingress, while also being impermeable to liquids to reduce corrosion and manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the outer sheath is increased to reduce corrosion of armor wires, then the reliability of the flexible pipe is improved, but the manufacturing cost increases due to more raw material required
Solution Approach 1:
The outer layer is designed with a porous structure containing hydrophobic pores that allow gas molecules to diffuse through while repelling water. This porous design enables the outer layer to be thin (1/125 to 1/75 of internal diameter) while still providing effective corrosion protection by allowing gas escape paths and preventing water contact with armor wires, thus reducing material usage and manufacturing cost while maintaining reliability
Solution Approach 2:
The outer layer is constructed as a composite material combining a polymer matrix with hydrophobic reinforcing elements. This composite structure provides both mechanical strength and hydrophobic properties, enabling the thin outer layer to effectively prevent water ingress while allowing gas diffusion, thereby protecting armor wires from corrosion without requiring excessive material thickness
2Reliability
If the thickness of the outer sheath is increased to prevent water ingress, then the reliability is improved, but the flexibility of the pipe deteriorates
Solution Approach 1:
The porous outer layer with hydrophobic pores provides water ingress prevention through the hydrophobic effect rather than through thickness, allowing the use of a thin layer that maintains pipe flexibility while reliably preventing water contact with internal components
Solution Approach 2:
The outer layer is designed as a thin flexible shell rather than a thick rigid barrier. The thin porous structure maintains the flexibility needed for submarine deployment while providing effective water ingress prevention through hydrophobic pore properties, avoiding the flexibility loss associated with thick outer sheaths
3Ease of manufacture
If the outer layer is made thin to reduce manufacturing cost, then the manufacturing cost is reduced, but the ability to prevent water ingress deteriorates
Solution Approach 1:
The thin outer layer compensates for its reduced thickness by incorporating a porous structure with hydrophobic properties. The hydrophobic pores actively repel water while allowing gas molecules to pass through, providing effective water ingress prevention in a thin configuration that reduces manufacturing cost
Solution Approach 2:
The patent replaces the traditional mechanical barrier approach (thick solid outer sheath) with a hydrophobic porous structure that uses surface chemistry and capillary pressure effects to prevent water ingress. This substitution allows thin layer design while maintaining effective water protection
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 effectively reduces gas concentration within the annular space, protecting the tensile armor layers from corrosion and preventing irreversible deformation of the flexible pipe under external pressure, while maintaining flexibility and sealing properties.
Implementation Method 1
The thickness of the external layer according to the invention promotes the diffusion of gases such as carbon dioxide, hydrogen sulphide and/or methane through the outer layer towards the outside of the flexible pipe
Implementation Method 2
an external layer impermeable to liquids... The outer layer... comprising at least one helically wound strip forming a plurality of turns
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
The invention relates to a flexible pipe (10) for conveying a fluid in a submarine environment, having a longitudinal axis (A) and a liquid-impermeable outer layer (20) with a thickness of between 1/125 and 1/75 of the internal diameter of said outer layer (20), and comprising at least one helically wound strip (22) forming a plurality of turns, said strip (22) being made of a polymer matrix (24) reinforced with a plurality of reinforcing elements (26).