Flexible Pipe Sheath Composition for Corrosion-Resistant Armor
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Solution Overview
Problem
Flexible pipes used in deep water hydrocarbon transport face corrosion and mechanical integrity issues due to exposure to corrosive gases and high mechanical loads, leading to stress corrosion cracking and reduced service life.
Innovation Solution
Incorporating a polymeric sheath with a thermoplastic polymer matrix and silicone composition in the outer or intermediate layers of the pipe to enhance gas permeability and mechanical strength, reducing corrosion and improving service life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional impermeable inner sheath is used, then mechanical strength is maintained, but corrosion of tensile armor layers occurs due to trapped corrosive gases
Solution Approach 1:
The inner sheath is designed with controlled permeability to gases, allowing corrosive gases (CO2, H2S) to pass through from the fluid circulation passage to the annular space, preventing gas accumulation and corrosion of the tensile armor layers while maintaining mechanical integrity
Solution Approach 2:
The annular space acts as an intermediary chamber between the fluid passage and outer environment, collecting and venting corrosive gases away from the tensile armor, thereby protecting the mechanical structure from corrosion
2Object-affected harmful factors
If high permeability sheath is used to evacuate gases, then corrosion resistance improves, but mechanical strength decreases
Solution Approach 1:
The sheath exhibits different properties for different functions: it has controlled permeability to gases (allowing gas evacuation) while maintaining high mechanical strength for structural support, achieving local optimization of material properties
Solution Approach 2:
The flexible pipe employs composite construction with multiple layers including the permeable inner sheath, tensile armor layers, and outer sheath, where each layer contributes specific properties (permeability, strength, protection) to resolve the contradiction between gas evacuation and mechanical integrity
3Strength
If tensile armor layers are placed in annular space, then mechanical strength is enhanced, but exposure to corrosive gases causes stress corrosion cracking
Solution Approach 1:
The annular space serves as a protective intermediary zone that collects and vents corrosive gases away from the tensile armor layers, reducing their exposure and preventing stress corrosion cracking while allowing the armor to maintain its mechanical strength
Solution Approach 2:
The controlled permeability of the inner sheath allows corrosive gases to pass through to the annular space rather than accumulating against the tensile armor, preventing gas-induced corrosion and stress corrosion cracking
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 increases gas permeability and mechanical strength, reducing corrosion of tensile armor layers and extending the service life of the flexible pipe in aggressive environments, allowing for the use of higher grades of steel and improved resistance to corrosive conditions.
Implementation Method 1
the polymeric sheath comprising a polymeric mixture comprising a thermoplastic polymer forming a matrix and at least one silicone composition incorporated in said matrix
Data Source
AI summary
The present invention relates to a flexible pipe (10) intended to be immersed into a body of water, comprising: - an inner sheath (12) defining a passage for transporting a fluid, in particular hydrocarbons; and - at least one tensile armor layer (16, 17) arranged around the inner sheath (12). The flexible pipe (10) comprises at least one polymeric sheath having a polymeric mixture comprising a thermoplastic polymer forming a matrix, and at least one silicone composition incorporated into said matrix.