Bending Rigid Subsea Spools via Tensile Chord Compression
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Solution Overview
Problem
The transportation and installation of long rigid subsea spools are challenging due to their susceptibility to bending and buckling, and existing methods are inefficient for connecting both ends of these spools to predetermined locations on the seabed, especially when their length exceeds their minimum bending radius, leading to costly and complex supporting structures.
Innovation Solution
A method involving a tensile chord system that applies longitudinally-compressive forces to bend the spool along its length, with anchorages at both ends to control the curvature and facilitate connection to subsea structures, allowing for precise control of the bend radius and safe installation without the need for bulky supporting structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rigid spools are used to reduce cost, then material cost is reduced, but the spools are susceptible to bending and buckling during transport and installation
Solution Approach 1:
A supporting structure comprising a series of support elements arranged along the length of the rigid spool provides intermediate support points during transport and installation. These support elements act as intermediaries that distribute loads and prevent excessive bending moments, allowing the rigid spool to maintain structural integrity without requiring overly complex bracing systems.
Solution Approach 2:
The supporting structure is divided into multiple discrete support elements spaced along the spool length rather than using a single continuous complex framework. This segmentation allows each support element to be independently positioned to provide optimal support at critical locations, reducing overall structural complexity while maintaining reliability.
2Reliability
If longer rigid spools are used to replace flexible pipe, then installation cost is reduced, but the spools become too long to be transported conveniently in a straight configuration
Solution Approach 1:
The rigid spool is designed with controlled elastic flexibility that allows it to bend dynamically during transport and installation while maintaining structural integrity. The spool can be bent to a radius greater than its minimum bending radius (MBR) to conform to transport constraints, then returns to its straight configuration when installed, enabling longer spools to be transported conveniently without compromising installation efficiency.
Solution Approach 2:
The spool's curvature radius is temporarily changed during transport to exceed the MBR, allowing the long spool to be bent into a transportable configuration. During installation, the curvature parameter is adjusted back to the optimal straight or gently curved state, enabling the spool to function effectively as a rigid connection while being transportable.
3Quantity of substance
If rigid spools with small wall thickness are used, then material usage is reduced, but the spools are more susceptible to buckling before proper support is established
Solution Approach 1:
The supporting structure is designed to be installed or positioned before the rigid spool is fully deployed or loaded. This preliminary support establishes critical load-bearing points that prevent buckling from occurring during the installation process, allowing the use of thinner-walled, more material-efficient spool designs without compromising buckling resistance.
Solution Approach 2:
The supporting structure acts as a preemptive cushioning system that provides load distribution and structural reinforcement before the spool is subjected to full operational loads. This beforehand support prevents buckling initiation during critical installation phases, enabling the use of optimized thinner-walled spools that would otherwise be prone to buckling.
4Stability of the object's composition
If bulky supporting structures are used to prevent bending, then structural stability is improved, but the structures become too large to be handled by conventional installation vessels
Solution Approach 1:
The supporting structure is segmented into multiple smaller support elements distributed along the spool length rather than using a single bulky framework. This segmentation reduces the volume of any individual support component, making the entire system handleable by conventional installation vessels while maintaining overall structural stability through the distributed support arrangement.
Solution Approach 2:
Support is provided at specific critical locations along the spool rather than through a continuous bulky structure. The support elements are strategically positioned at locations where bending moments are highest or where support is most needed, providing local stability enhancement without the volume penalty of a comprehensive bulky supporting structure throughout the entire spool length.
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
This approach enables the efficient transportation and installation of longer rigid spools by controlling the curvature of the spool during transport and installation, reducing the risk of buckling and fracture, and allowing for precise connection to subsea structures, thereby reducing costs and operational complexity.
Implementation Method 1
shortening a tensile chord system acting on longitudinally-spaced locations on the element to apply longitudinally-compressive forces to the element, which forces bend the element along its length between said locations against elastic recovery force
Data Source
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AI summary
A method of handling a discrete elongate subsea element (32) of determinate length, such as a spool of rigid pipe. The method comprises shortening a tensile chord system (44) acting on longitudinally-spaced locations (52) on the element to apply longitudinally-compressive forces to the element. The compressive forces bend the element along its length against elastic recovery force to shorten the span of the element. One end of the element is anchored at a first anchorage (34) before or after the element is bent. The other end of the element is anchored at a second anchorage (34), after the element is bent and while the element remains bent. The method is apt to be used during installation of the element, where the anchorages are both underwater, and during transportation of the element, where the anchorages are hang-off platforms of a surface vessel.