Flexible Pipe Stiffening Cover for Overbending Control
Solution Overview
Problem
Unbonded flexible pipes used in dynamic offshore applications face challenges in maintaining high flexibility while minimizing the risk of overbending due to stiff armoring layers, which can lead to deformation or breakage under mechanical and turbulent forces.
Innovation Solution
The flexible pipe design incorporates a stiffening cover with a layer of material having a higher flexural modulus than the outer sealing sheath, specifically polyethylene or polyamide-based materials, to increase stiffness in critical sections without compromising flexibility, and can be applied selectively to areas prone to excessive bending.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If armoring layers are made stiffer to prevent pipe collapse, then structural strength is improved, but flexibility deteriorates and the pipe becomes susceptible to overbending and wire breakage
Solution Approach 1:
The patent applies different stiffness characteristics to different parts of the pipe structure. The armoring layers provide localized strength where needed to prevent collapse, while the unbonded configuration allows flexibility in other regions. This local differentiation resolves the contradiction by having strong where strength is needed and flexible where movement is needed.
Solution Approach 2:
The unbonded flexible pipe allows dynamic movement between layers, enabling the structure to adapt to varying mechanical loads and turbulent forces. The layers can slide relative to each other, providing dynamic flexibility that prevents overbending while maintaining overall structural integrity under different operating conditions.
2Ease of operation
If armoring layers are made more flexible to follow dynamic motions, then flexibility is improved, but structural strength deteriorates and the pipe becomes susceptible to collapse
Solution Approach 1:
The patent uses composite construction with multiple unbonded layers including inner and outer sheaths, armoring layers, and reinforcement elements. This composite structure combines materials with different properties - the sheaths provide flexibility and sealing, while the armoring layers provide structural strength, achieving both flexibility and strength simultaneously.
Solution Approach 2:
The pipe is divided into multiple unbonded segments or layers that can move independently. The armoring layers are segmented into discrete helical or axial elements that can flex relative to each other, maintaining structural support while allowing the overall pipe to follow dynamic motions without collapse.
3Strength
If bonding agents are used to strengthen the bond between layers, then structural strength is improved, but flexibility deteriorates and the pipe loses its ability to withstand dynamic forces
Solution Approach 1:
The patent removes the bonding agents entirely from the pipe construction. By taking out the bonding function, the layers remain unbonded and free to move relative to each other, maintaining flexibility while deriving strength from the composite action and geometric configuration of the unbonded layers rather than adhesive bonds.
Data Source
AI summary
The invention relates to an unbonded, flexible pipe having a length and comprising from inside out, a tubular inner sealing sheath, at least one metal armor layer and an outer sealing sheath of a sealing material. The unbonded, flexible pipe comprises at least one stiffened length section comprising a stiffening cover partially or totally surrounding the outer sealing sheath in the stiffened length section. The stiffening cover comprises a layer of a stiffening material having a flexural modulus which is higher than the flexural modulus of the sealing material, wherein the flexural modulus is determined according to ISO 178.