Flexible Pipe Armour Anodes for Long-Range Subsea Corrosion Protection
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Solution Overview
Problem
Conventional cathodic protection systems for flexible pipes in subsea environments suffer from attenuation effects, limiting the effective length of protection and requiring more end fittings, which increases cost and complexity.
Innovation Solution
The implementation of helically wound elongate anode elements with a cross-section aspect ratio of 1:1, made from more electrically reactive materials than the tensile armour wires, interposed between armour wires, to provide effective cathodic protection along the length of flexible pipes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cathodic protection systems are used with end fittings, then corrosion protection is provided, but the effective length is limited due to attenuation effects and more end fittings are required
Solution Approach 1:
The cathodic protection system is segmented into multiple distributed anodes positioned at different locations along the flexible pipe, with each anode providing local protection to its surrounding region, thereby extending the overall protected length without requiring additional end fittings
Solution Approach 2:
Electrically conductive elements are introduced as intermediaries to electrically connect the distributed anodes to the armour wires, enabling the anodes to effectively provide cathodic protection despite being positioned at intermediate locations rather than at the pipe ends
2Length of stationary object
If more end fittings are added to extend protection length, then effective protected length increases, but device complexity and cost increase
Solution Approach 1:
Instead of using fewer, larger end fittings, the system uses multiple smaller distributed anodes along the pipe length, which achieves extended protection coverage without increasing the number of complex end fitting assemblies
Solution Approach 2:
The distributed anodes are integrated directly into the flexible pipe structure during manufacturing, allowing the pipe to provide its own cathodic protection system without requiring separate, complex end fitting installations
3Length of stationary object
If distributed anodes are used instead of end fittings, then protected length increases, but manufacturing complexity may increase
Solution Approach 1:
The manufacturing process merges the incorporation of distributed anodes with the existing flexible pipe assembly process, integrating multiple components (anodes, conductive elements, armour wires) into a single coordinated manufacturing operation rather than separate steps
Solution Approach 2:
The helical armour wire structure serves multiple functions: it provides mechanical strength and tension resistance while also serving as the cathodic protection electrode surface, eliminating the need for separate protection structures
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
This solution reduces attenuation effects, allowing for longer protected lengths of flexible pipes without the need for additional end fittings, thereby decreasing costs and complexity while maintaining effective corrosion protection.
Implementation Method 1
providing corrosion protection to armour wires of at least one tensile armour layer of a flexible pipe having a breached pipe annulus region
Data Source
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AI summary
A flexible pipe for subsea transportation of production fluids, a method of manufacturing flexible pipe body and a method of providing corrosion protection to armour wires of at least one tensile armour layer of a flexible pipe having a breached pipe annulus are disclosed. The flexible pipe comprises a fluid retaining layer, an outer sheath and at least one tensile armour layer comprising a plurality of helically wound monofilament armour wires of a first material, each having a non-circular cross section with an aspect ratio of greater than 1:2 disposed between the fluid retaining layer and the outer sheath. The tensile armour layer further comprises at least one helically wound elongate anode element substantially having a cross-section aspect ratio of 1:1 and comprising a further material, interposed between armour wires, the anode element cross section having an area that is 50% or less of a corresponding area of said non-circular cross section.