Helical Buoyancy Elements in Flexible Pipe Bodies
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Solution Overview
Problem
Flexible pipes in deep and ultra-deep water environments face high tension loads due to internal pressure and self-supported weight, leading to potential failure, and existing buoyancy aids can increase compression and tension forces at the touchdown area, causing birdcaging and requiring labor-intensive and costly installation.
Innovation Solution
A flexible pipe body with integrated buoyancy elements, such as syntactic foam rods, helically wound at a 25-degree angle, providing continuous buoyancy along the pipe length to reduce tension loads and prevent birdcaging, manufactured during production for cost-effective and efficient deployment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional buoyancy aids are added to flexible pipe at discrete locations, then tension loads on tensile armour layer are reduced, but compression and tension forces at touchdown area increase causing birdcaging
Solution Approach 1:
The buoyancy is segmented into multiple discrete buoyancy elements distributed along the pipe length, with specific positioning to avoid concentration of forces at touchdown area while still providing overall tension relief to the tensile armour layer
Solution Approach 2:
The buoyancy elements are strategically positioned at specific locations along the pipe rather than uniformly distributed, creating local variations in buoyancy support that prevent force concentration at critical areas like the touchdown zone while maintaining overall structural integrity
2Strength
If discrete buoyancy aids are attached to flexible pipe, then uplift is provided to reduce tension loading, but installation becomes labor-intensive and costly
Solution Approach 1:
The buoyancy elements are integrated into the flexible pipe structure during manufacturing, merging the buoyancy function with the pipe body construction. This eliminates separate attachment operations and reduces installation complexity while maintaining the tension relief function
Solution Approach 2:
The buoyancy elements are pre-positioned and integrated into the pipe structure during manufacturing before deployment. This preliminary action eliminates the need for complex field installation operations and reduces labor requirements during deployment
3Strength
If stepped riser configuration with multiple junctions is used, then buoyancy aids can be positioned at discrete locations, but device complexity increases
Solution Approach 1:
The flexible pipe body is designed as a universal structure that can accommodate buoyancy elements at various positions along its length without requiring stepped configurations or multiple junctions. The pipe body itself serves multiple functions: fluid transport, structural support, and integrated buoyancy accommodation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The integrated buoyancy elements effectively reduce tension loads and prevent birdcaging, allowing for simpler and cost-effective installation, while maintaining flexibility and structural integrity in extreme water environments.
Implementation Method 1
The buoyancy elements provide an upwards lift to counteract the weight of the riser, effectively taking a portion of the weight of the riser, at various points along its length
Data Source
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AI summary
A flexible pipe body and method of producing a flexible pipe body are disclosed. The flexible pipe body 400 includes an inner fluid retaining layer 402; an armour layer 404 provided radially outwards of the inner fluid retaining layer; and a buoyancy layer 406 comprising a plurality of discrete elongate buoyancy elements provided radially outwards of the fluid retaining layer wound at a helical pitch angle equal to or more than 0 degrees and less than about 85 degrees to the longitudinal axis of the flexible pipe body.