Subsea Flexible Pipe Sacrificial Layer for Armor Corrosion Control
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Solution Overview
Problem
Flexible pipes used in subsea hydrocarbon transport face significant mechanical stress and corrosion issues due to high tensile armor loads and exposure to corrosive gases like hydrogen sulfide and carbon dioxide, leading to potential loss of mechanical integrity and stress corrosion cracking.
Innovation Solution
Incorporation of a sacrificial metal layer with a porous body, such as metal foam or wool, impregnated with a water-soluble resin, which reacts with oxygen and consumes hydrogen sulfide, reducing corrosion and enhancing mechanical strength by providing additional surface area for reaction and cathodic protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metallic tensile armor layers are used to ensure good tensile strength, then mechanical strength is improved, but corrosion resistance deteriorates due to exposure to corrosive gases and water in the annular space
Solution Approach 1:
A sacrificial metal layer is introduced as an intermediary between the corrosive environment (corrosive gases and water in the annular space) and the metallic tensile armor layers. This sacrificial layer preferentially corrodes, protecting the tensile armor from direct exposure to corrosive agents, thereby maintaining both mechanical strength and corrosion resistance.
Solution Approach 2:
The sacrificial metal layer is designed to be consumed over time as it corrodes preferentially, protecting the more valuable tensile armor layers. This disposable layer sacrifices itself to extend the service life of the entire pipe structure, particularly protecting the load-bearing components.
2Length of moving object
If the line length is increased to serve greater depths, then service capability is improved, but mechanical stress on tensile armor increases leading to higher corrosion risk
Solution Approach 1:
The sacrificial metal layer serves as a protective intermediary that becomes increasingly important as line length increases. It absorbs the corrosive effects that would otherwise accumulate and intensify over the extended length of the pipe, particularly protecting the tensile armor from stress corrosion cracking in the annular space.
Solution Approach 2:
The sacrificial layer provides beforehand cushioning against corrosion by being positioned in advance to intercept corrosive agents before they can reach the tensile armor. This pre-protective measure is particularly valuable in long lines where cumulative exposure to corrosive environments would be severe.
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 sacrificial layer effectively limits corrosion and enhances the mechanical strength and service life of the flexible pipe by rapidly reacting with oxygen and reducing hydrogen sulfide concentrations, thereby preventing stress corrosion cracking and extending the pipe's operational lifespan.
Implementation Method 1
a first sacrificial layer (18) made from a porous body (30) at least partially metallic... which reacts with oxygen
Implementation Method 2
reacts with oxygen and consumes hydrogen sulfide, reducing corrosion
Implementation Method 3
a porous body (30) at least partially metallic... providing additional surface area for reaction
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The invention relates to a line to be submerged in a body of water, comprising: an outer sheath defining an inner volume; an inner sheath arranged in the inner volume and defining a passage for the transport of a fluid, particularly of hydrocarbons, the inner sheath and the outer sheath together defining an annular space; and at least one traction armour ply arranged in the annular space. The line comprises at least one metal sacrificial layer (18) arranged in the annular space, the sacrificial layer (18) comprising a porous body (30) having a minimum specific surface area of at least 5 cm2/g, and the sacrificial layer (18) having a linear metal surface per metre of line of at least 0.3 m2/m.