Flexible Riser Design with Metal and Composite Armor Sections
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Solution Overview
Problem
Existing riser systems for deep water subsea fluid transportation face challenges with stiffness from metallic rigid central parts, leading to excessive stress on flexible pipe sections, and require complex buoyancy arrangements that are costly and difficult to install and control.
Innovation Solution
A riser system comprising an unbonded flexible metal armored section and a composite armored section, with the metal armored section closer to the upper facility to manage tensile forces and reduce corrosion risk, and the composite section in direct contact with seawater to avoid pressure buildup, eliminating the need for rigid central parts and complex buoyancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a metallic rigid central part is used in the riser system, then the riser provides structural strength and rigidity, but it generates excessive stiffness that subjects flexible pipe sections to uncontrolled stress
Solution Approach 1:
The patent removes the metallic rigid central part from the riser system entirely, extracting the source of excessive stiffness while maintaining structural integrity through alternative means (flexible pipe design with appropriate armor layers and buoyancy modules)
Solution Approach 2:
The patent changes the physical parameters of the flexible pipe sections by incorporating specific armor layer configurations, material properties, and buoyancy module distributions to achieve the required structural strength without relying on rigid central components
2Adaptability or versatility
If flexible pipes are used for deep water applications to accommodate large movements, then the riser achieves high flexibility, but it becomes very heavy and requires complex buoyancy arrangements
Solution Approach 1:
The patent divides the riser into multiple sections with different flexibility requirements, allowing the upper portions to have higher flexibility for movement accommodation while lower portions can be more rigid for stability, eliminating the need for complex distributed buoyancy arrangements
Solution Approach 2:
The patent employs composite armor layers combining different materials (metallic and non-metallic) with distinct properties to achieve the required flexibility-strength balance without adding excessive weight or requiring complex buoyancy systems
3Reliability
If the metal armored section is placed closer to the upper facility, then tensile forces are better managed and corrosion risk is reduced, but the composite section must withstand direct seawater contact
Solution Approach 1:
The patent applies different material qualities to different sections of the riser: metal armor near the upper facility for corrosion resistance and tensile strength, and composite armor in lower sections for flexibility and seawater compatibility, with each section optimized for its specific environmental conditions
Data Source
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AI summary
The invention relates to a riser for transporting fluid between an upper facility and a subsea facility. The riser has a center axis and a length along the center axis and comprises an unbonded flexible metal armored riser section and an unbonded flexible composite armored riser section arranged in fluid connection to each other. The metal armored riser section comprises at least two cross-wound tensile armor layers each comprising a plurality of helically wound elongate metal armor elements wound with a winding angle of about 60 degree or less relative to the center axis. The composite armored riser section comprises at least one tensile armor layer comprising a plurality of helically wound elongate composite armor elements wound with a winding angle of about 60 degree or less relative to the center axis. The invention also relates to an offshore system comprising such riser.