Flexible Duct Reinforced Maintain Layer for Radial Buckling
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Solution Overview
Problem
Flexible underwater pipes used for transporting hydrocarbons face challenges in extreme depths and dynamic bending stresses, leading to radial 'birdcage' buckling due to the swelling of traction armor layers, which can result in irreversible deformation and pipe failure.
Innovation Solution
The use of a retaining tape with a polymer reinforcing layer and a textile layer interposed between the fiber rovings and the reinforcing layer increases the bending rigidity of the coated retaining strip, enhancing its resistance to deformation and fatigue under extreme conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reinforcing ribbons made of Kevlar fibers are wound around traction armor layers to limit swelling, then the risk of radial buckling is reduced, but the bending rigidity is insufficient under extreme dynamic conditions
Solution Approach 1:
The patent combines Kevlar fiber rovings with a polymer matrix material to create a composite retaining ribbon. The Kevlar fibers provide high tensile strength to resist swelling forces, while the polymer matrix provides bending rigidity and structural continuity. This composite structure resolves the contradiction by integrating both required properties into a single reinforcing element that can withstand both radial expansion and dynamic bending stresses.
Solution Approach 2:
The patent modifies the physical and mechanical parameters of the retaining layer by using high-modulus Kevlar fibers (with elastic modulus greater than 50 GPa) and optimizing the polymer matrix composition. These parameter changes enable the retaining ribbon to simultaneously achieve sufficient tensile strength for swelling resistance and adequate bending rigidity for fatigue resistance under dynamic conditions.
2Productivity
If the flexible pipe is used at great depths with dynamic bending stresses, then hydrocarbon transport capability is maintained, but fatigue phenomenon deteriorates the reinforcing tapes
Solution Approach 1:
The composite structure of Kevlar fibers embedded in a polymer matrix provides superior fatigue resistance compared to traditional woven tapes. The continuous fiber orientation and polymer bonding create a more durable structure that can withstand the cyclic bending stresses encountered in dynamic deep-water conditions while maintaining hydrocarbon transport functionality.
Solution Approach 2:
The patent specifies using Kevlar fibers with elastic modulus greater than 50 GPa and elongation at break greater than 2%, which are critical parameters for fatigue resistance. These parameter selections ensure the retaining layer can endure the repeated bending cycles experienced in dynamic deep-water operations without deteriorating.
3Reliability
If the external sheath is tight to oppose swelling, then hydrostatic pressure effectively counteracts armor expansion, but any tear causes immediate loss of pressure opposition
Solution Approach 1:
The patent applies preliminary anti-action by placing the retaining layer with high tensile strength between the traction armor and the external sheath. This layer pre-establishes a protective barrier that counteracts the swelling forces before they can reach the external sheath, thereby preventing the conditions that would lead to sheath tearing while maintaining pressure opposition capability.
Data Source
Figure 1~3
Figure 4~7
AI summary
The invention relates to an underwater flexible duct for conveying hydrocarbons, said flexible duct including from the inside to the outside an inner sealing sheath (18), at least one ply of traction armours (14, 16) wound about said inner sealing sheath, a deformable maintain layer (12) including at least one flexible maintain ribbon wound about said traction armour ply, and at least one tubular structure (10) surrounding said maintain layer, wherein the maintain ribbon includes fibre wicks and said wicks are oriented substantially in the longitudinal direction of said maintain ribbon. According to the invention, the maintain ribbon is covered by a reinforcing layer of a polymer material for the deformation resistance of said maintain layer.