Flexible Pipe Carcass Cover Strip for Vortex-Free Windings
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Solution Overview
Problem
Traditional carcass structures in flexible offshore pipes suffer from vortex formation and resulting vibrations due to gaps between windings, leading to fatigue damage, and previous attempts to mitigate this have either reduced pipe capacity or been impractical in manufacturing.
Innovation Solution
A method for producing a carcass with a cover strip that involves pretreating the anchor width section to reduce resistance against length extension and bending, allowing for helical winding without buckling, and using a cover strip with a smaller winding radius to cover interstices between windings, thereby reducing tension undulations and enhancing structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional carcass structures with gaps between windings are used, then manufacturing is simpler, but vortex formation and vibrations occur leading to fatigue damage
Solution Approach 1:
The harmful gaps or interstices between adjacent windings are removed by inserting a cover strip into these spaces. The cover strip is positioned between the windings to eliminate the gaps that cause vortex formation, thereby extracting the harmful element (gaps) from the carcass structure while maintaining the overall winding configuration.
Solution Approach 2:
A cover strip is introduced as an intermediary element between the adjacent metal strip windings. This cover strip fills the interstices and prevents direct fluid flow through the gaps, acting as a mediator that eliminates vortex formation without requiring changes to the fundamental winding process or metal strip configuration.
2Reliability
If flow velocity is reduced to eliminate vortex formation, then vibrations and fatigue damage are reduced, but pipe capacity is reduced
Solution Approach 1:
The invention converts the harmful effect of fluid flow through gaps (which causes vortex formation) into a beneficial outcome by using the cover strip to redirect the flow. The fluid that would have caused damage now flows over the smooth outer surface of the cover strip, eliminating vortex formation while maintaining high flow velocities and pipe capacity.
3Reliability
If cover strip is added to cover interstices, then vortex formation is reduced, but manufacturing complexity increases
Solution Approach 1:
The cover strip is implemented as a thin, flexible element that can be easily inserted into the interstices between windings. This thin-film approach provides effective gap coverage without adding significant structural complexity or weight, maintaining the flexibility and simplicity of the overall carcass construction while eliminating vortex formation.
4Strength
If anchor width section of cover strip is not pretreated, then material strength is maintained, but tension undulations and buckling occur during winding
Solution Approach 1:
The anchor width section of the cover strip undergoes pretreatment before being applied to the carcass. This preliminary action involves modifying the material properties of the anchor section to reduce its resistance against length extension and bending, making it more compliant during the winding process. This pretreatment prevents tension undulations and buckling, ensuring smooth application while the rest of the cover strip maintains its full strength.
Solution Approach 2:
The cover strip exhibits local quality differentiation where the anchor width section has modified properties (reduced resistance to extension and bending) compared to the rest of the strip. This localized modification allows the anchor section to conform smoothly during winding without affecting the overall strength and rigidity of the cover strip in its functional coverage area.
Data Source
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AI summary
P71696PC01 35 ABSTRACT Herein is described a method of producing a carcass for a flexible pipe, the carcass and a flexible pipe with the carcass. The method includes providing at least one first metallic strip a cover metallic strip. Shaping the first strip to have a profile with a first fold adapted to face 5 towards the carcass axis and a second fold adapted to face away from the carcass axis. Pretreating an anchor width section of the cover strip including a weakening treatment of resistance against length extension and/or a length extension of the pretreated part of the anchor width section. Inserting the anchor width section of the cover strip into the first fold, ensuring that a 10 cover width section of the cover strip extends beyond the second fold. Helically winding the first metallic strip and the cover strip, to provide that the first fold engages and interlocks with the second fold and that the cover width section covers a helical interstice between windings of the first metallic strip on the inner side of the carcass.15 Fig.2 20