Dual Axis Chain Support for Offshore Mooring Fatigue Reduction
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Solution Overview
Problem
Existing mooring systems for offshore structures face issues with out-of-plane bending-induced fatigue damage, limited rotation capabilities, and challenging maintenance due to complex chain retainer mechanisms, which affect the alignment and adjustability of mooring lines.
Innovation Solution
A dual-axis chain support with an elongated hawse pipe and a gimbal body, equipped with passive spring-loaded chain retainers and a cruciform chain guide, allowing for extensive rotation and adjustable length while minimizing bending stresses and facilitating easy maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a chain stopper provides two axes of rotation with a fixed captive link, then reduced chain wear is achieved, but out-of-plane bending occurs causing fatigue damage
Solution Approach 1:
The patent applies dynamics by making the chain retainer mechanism movable rather than fixed. The retainer can dynamically adjust its position and orientation to follow the chain's natural bending plane, eliminating fixed-point out-of-plane bending stresses while maintaining rotational capability around two perpendicular axes
Solution Approach 2:
The patent changes the geometric parameters of the chain support assembly, specifically positioning the chain retainer at a distance from the intersection of rotation axes. This parameter change allows the retainer to operate in a plane that accommodates chain bending without inducing out-of-plane stresses, while still providing the necessary rotational freedom
2Object-affected harmful factors
If the chain retainer mechanism is located below the two axes of rotation, then out-of-plane bending is minimized, but operation and maintenance become more challenging
Solution Approach 1:
The patent resolves this contradiction by operating in another dimension - placing the chain retainer in a horizontal plane rather than vertically below the axes. The retainer is positioned at a radial distance from the rotation axis intersection, allowing it to access chains from the side while maintaining minimal out-of-plane bending through proper geometric alignment
3Strength
If the hawse pipe is made load carrying, then structural integrity is improved, but the overall width of the assembly increases
Solution Approach 1:
The patent applies universality by making the hawse pipe multi-functional - it serves both as a structural load-carrying member and as part of the rotation mechanism. The hawse pipe acts as one of the rotation axes themselves, eliminating the need for separate wide mounting structures while maintaining full load-carrying capability
4Ease of operation
If spring-loaded chain retainers are used, then operation is automated and maintenance is simplified, but device complexity increases
Solution Approach 1:
The patent applies self-service through spring-loaded retainers that automatically engage and disengage chain links without manual intervention. The springs provide the necessary force for automatic operation, and the retainers self-regulate their positioning, eliminating complex control systems while maintaining simplicity through mechanical self-actuation
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 solution reduces fatigue damage from out-of-plane bending, enables smooth rotation and vertical adjustments, maintains chain alignment, and simplifies operation and maintenance by ensuring the chain is pulled in a straight line, even under tension, with the option for dual or single retainer mechanisms.
Implementation Method 1
The use of a passive, spring actuated chain retainer mechanism, operation of the chain retainer mechanism is assured regardless of the orientation of the hawse pipe
Implementation Method 2
An elongated hawse pipe is pivotally connected to a structure such as a vessel or buoy by using a gimbal body
Data Source
AI summary
A chain support, hinged on two perpendicular axes to allow chain movement in two perpendicular planes is disclosed. The apparatus provides an improved arrangement to allow chain to be pulled at an angle above the chain support while maintaining straight pull across a stopper mechanism.