Offshore Cable Hang-Off Pivoting to Reduce Fatigue
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Solution Overview
Problem
Dynamic cables suspended from offshore structures experience repeated bending due to environmental loads and floater movement, leading to fatigue failure, which is typically addressed by using a bend stiffener that requires a water barrier at the structure interface.
Innovation Solution
A transfer system with a hang-off device that allows the cable to pivot above the waterline, reducing the need for a water barrier and distributing bending stress through pivotable elements, thereby reducing strain variations and avoiding or minimizing the use of a bend stiffener.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bend stiffener is introduced to distribute cable curvature and keep local strains below critical values, then cable fatigue resistance is improved, but device complexity increases and a water barrier is required at the structure interface
Solution Approach 1:
The patent removes the bend stiffener and water barrier components from the cable system. Instead of adding protective elements, the solution extracts these components entirely by allowing the cable to pivot above the waterline, eliminating the need for complex protective structures while maintaining cable integrity through reduced bending moments
Solution Approach 2:
The patent moves the cable bending location from the horizontal plane at the structure interface to the vertical dimension above the waterline. By positioning the hang-off point above the waterline, the cable bending occurs in a different spatial dimension where water barrier requirements are eliminated
2Strength
If a bend stiffener is used to protect the cable interface, then cable component strain is reduced, but the need for a water barrier increases device complexity
Solution Approach 1:
The patent extracts both the bend stiffener and water barrier from the system. The cable is allowed to pivot freely above the waterline without requiring protective stiffening elements or water barriers, reducing both strain through eliminated bending moments and device complexity through component removal
3Device complexity
If the cable is allowed to pivot above the waterline without a water barrier, then device complexity is reduced, but the cable may experience angular deflection and bending
Solution Approach 1:
The patent introduces dynamic pivoting capability to the cable system. The cable is allowed to rotate and pivot at the hang-off point above the waterline, transforming from a static fixed connection to a dynamic articulated connection that can accommodate environmental movements and floater motion without requiring complex protective structures
Solution Approach 2:
The patent converts the potential harm of cable bending and angular deflection into a benefit by allowing controlled pivoting above the waterline. This controlled movement reduces the bending moments compared to a rigid fixed connection, transforming what could be a stability problem into a fatigue reduction solution
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 configuration reduces fatigue in cable components by allowing angular deflection and bending above the hang-off device, minimizing the need for a bend stiffener or reducing its dimensions, and maintaining mechanical strength and protection without a water barrier.
Implementation Method 1
a first element pivotably connected to the base at a first pivoting axis
Data Source
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AI summary
The present invention relates to a transfer system connectable to an offshore structure. The transfer system comprises a transfer device connectable to a connector box on the offshore structure. The transfer device comprises a tensile element; wherein the transfer device is defined with a lower section and an upper section, wherein the tensile element is removed from at least parts of the upper section. The transfer system further comprises a hang-off device comprising a base mechanically connectable to the offshore structure. The hang-off device comprises a first element pivotably connected to the base at a first pivoting axis. The lower section is suspended from the first element into a wet zone of the offshore structure while the upper section is extending above the first element into a dry zone of the offshore structure.