Mooring Energy Absorption Arrangement for Peak Load Reduction
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Solution Overview
Problem
Designing a mooring arrangement in shallow water for floating vessels in extreme weather conditions is challenging due to non-linear restoring forces and sensitive extreme loads, which existing technologies fail to adequately address by reducing peak loads effectively.
Innovation Solution
An energy absorption arrangement comprising a rigid yoke with a weighted pendulum member and an energy absorption device with a movable rod and absorption medium, which absorbs mooring loads up to a predetermined level and exerts a restoring force to reduce peak loads, allowing the rod to extend and retract based on load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional mooring arrangement with rigid yoke and ballast is used, then the vessel can be moored in shallow waters, but the peak mooring loads become extremely sensitive to wave conditions and can reach dangerous levels
Solution Approach 1:
The energy absorption device is pre-configured with a rod and absorption medium (such as gas or liquid) that activates beforehand to cushion extreme load peaks. The device absorbs energy through controlled compression of the absorption medium when loads exceed the predetermined threshold, preventing dangerous peak loads before they can damage the mooring system.
Solution Approach 2:
The energy absorption device changes the mechanical parameters of the mooring system by introducing a non-linear spring element with variable stiffness. The absorption medium (gas or liquid) changes its compressibility characteristics under different pressure conditions, allowing the system to maintain stability under normal conditions while absorbing extreme peaks during severe weather.
2Force
If existing damping arrangements are used to reduce extreme loads, then general damping of vessel motion is increased, but the specific peak load reduction is insufficient
Solution Approach 1:
The damping function is segmented into two distinct components: a weighted pendulum for general motion damping and an energy absorption device for specific peak load reduction. This segmentation allows each component to specialize in its function, with the energy absorption device specifically targeting extreme load peaks through its rod and absorption medium mechanism.
Solution Approach 2:
The energy absorption device acts as an intermediary element between the rigid yoke and the floating vessel. It mediates the transmission of loads by absorbing extreme peaks through the compression of its absorption medium, thereby protecting the mooring system without requiring complex active control systems.
3Force
If more ballast is added to the yoke to increase restoring forces, then the mooring capability in extreme weather improves, but the total weight and system complexity increase significantly
Solution Approach 1:
The mechanical system is modified by replacing pure mass-based restoring forces (ballast) with a hybrid system that includes an energy absorption device using compressed gas or liquid. This substitution reduces the need for excessive ballast weight while maintaining restoring forces through the elastic properties of the absorption medium.
Solution Approach 2:
The mooring system employs a composite approach combining traditional mechanical elements (rigid yoke, ballast) with elastic energy storage elements (compressed gas or liquid in the absorption device). This composite structure achieves the required restoring forces with optimized weight distribution and reduced overall system mass.
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 significantly reduces peak mooring loads by absorbing kinetic energy, decreasing the probability of vessel disconnection during extreme events and maintaining system stability in varying weather conditions.
Implementation Method 1
an absorption medium... the rod... is extended a second length when exposed to a second load greater than the first load
Implementation Method 2
at least one energy absorption device for reducing peak mooring loads... Mooring loads higher than the first predetermined load is absorbed by the at least one energy absorption device
Implementation Method 3
a weighted pendulum member arranged on the end of the yoke... Mooring loads up to a first predetermined load is absorbed by the weighted pendulum
Implementation Method 4
The energy absorption device exerts a restoring force opposite of the first and second load, causing the rod to retract from its second length to its first length when the mooring loads decreases
Data Source
AI summary
An energy absorption arrangement for reducing peak mooring loads between a mooring structure with a turret rotatable around a vertical axis, and a floating structure is disclosed. The energy absorption arrangement comprises a rigid yoke horizontally rotatable in two axes and connected to the turret, a weighted pendulum member arranged on the end of the yoke and at least one mooring tether connected to the weighted pendulum member, and at least one energy absorption device for reducing peak mooring loads, comprising a fixed part connected to the floating structure, a movable rod and an absorption medium.