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 'singing carcasses' or flow-induced pulsations, which cause fatigue damage, and previous solutions like inserting holes or profiles have been ineffective or complicated to manufacture.

Innovation Solution

A method involving a cover strip with a pretreated anchor width section to reduce tensioning and buckling, where the anchor width section is weakened to match the winding radius of the cover width section, ensuring interlocking folds and reduced resistance to bending, thereby minimizing vortex formation and corrosion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If traditional carcass structures with gaps between windings are used, then the carcass provides structural support, but vortex formation and vibrations occur leading to fatigue damage

Engineering Contradiction:

Improvestructural supportVSAvoidvortex formation and vibrations

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The harmful gaps between windings are removed by inserting a cover strip into the carcass structure. The cover strip effectively extracts or eliminates the source of vortex formation while preserving the structural support function of the carcass.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

A cover strip is introduced as an intermediary element between the windings. This mediator fills the gaps and prevents direct fluid interaction with the carcass structure, thereby eliminating vortex formation while maintaining structural integrity.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If flow velocity is reduced to eliminate vortex formation, then vibrations are reduced, but the capacity of the flexible pipe is reduced

Engineering Contradiction:

Improvevortex formationVSAvoidpipe capacity

Core Design Contradiction:

Object-affected harmful factorsVSProductivity

Solution Approach 1:

Instead of reducing flow velocity, the solution extracts the harmful gaps from the system by inserting the cover strip. This allows high flow velocities to be maintained while vortex formation is eliminated, preserving pipe capacity.

Inventive Principle:

Principle #2Taking out (Extraction)

3Object-affected harmful factors

If cover strip is added to carcass structure, then vortex formation is reduced, but manufacturing complexity increases due to tensioning and buckling issues

Engineering Contradiction:

Improvevortex formationVSAvoidmanufacturing complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The anchor width section of the cover strip is pretreated before insertion to reduce its bending resistance. This preliminary action prevents tensioning and buckling issues during the winding process, simplifying manufacturing while maintaining the vortex-reducing benefit.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Different sections of the cover strip have different properties: the anchor width section has reduced bending resistance for easy insertion, while the cover width section maintains sufficient stiffness to effectively cover the gaps. This local differentiation resolves the manufacturing complexity issue.

Inventive Principle:

Principle #3Local quality

4Strength

If anchor width section of cover strip has high bending resistance, then structural integrity is maintained, but tensioning and buckling occur during winding

Engineering Contradiction:

Improvestructural integrityVSAvoidwinding process

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The cover strip is designed with non-uniform properties: the anchor width section has reduced bending resistance for easy winding, while the cover width section maintains high bending resistance for structural integrity and effective gap coverage.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The anchor width section undergoes pretreatment to reduce bending resistance before the winding process. This preliminary modification enables easy insertion without tensioning, while the overall structural integrity is preserved through the design of the cover width section.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS12011750B2Method for producing a carcass, a method of producing a flexible pipe and a flexible pipe

Publication Date: 2024.06.18 NAT OILWELL VARCO DENMARK

AI summary

A method of producing a carcass for a flexible pipe, the carcass and a flexible pipe with the carcass 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 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 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.