Disconnectable Mooring Line Segmentation for Ice Load Management

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Solution Overview

Problem

Disconnectable mooring systems face challenges when high mooring forces are transmitted during disconnect operations, leading to asymmetrical loads that can cause damage to the buoy member, risers, and surrounding structures due to extreme conditions like drifting pack ice.

Innovation Solution

The mooring lines are designed with a first section connected to the turret structure and a second section connected to the buoy member, where the second section is of sufficient length to remain slack during mooring force transmission, allowing direct force transfer to the turret structure and reducing asymmetrical loads, enabling controlled disconnect and lowering of the buoy member without causing damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the buoy member is disconnected from the turret structure under extreme mooring forces, then the vessel can be freed from ice encasement, but the buoy member tilts and causes severe damage to structural parts

Engineering Contradiction:

Improvevessel freedom from ice encasementVSAvoidstructural damage to buoy member and surrounding structure

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The mooring line is divided into two distinct sections: a first section connected to the turret structure and a second section connected to the buoy member. This segmentation allows the first section to remain tensioned and connected to the turret during disconnect operations, while the second section can be sufficiently long to prevent tilting and structural damage to the buoy member during the disconnect process.

Inventive Principle:

Principle #1Segmentation

2Object-affected harmful factors

If the second section of the mooring line is made longer to reduce asymmetrical loads, then the buoy member can be lowered safely, but the device complexity increases

Engineering Contradiction:

Improveasymmetrical load reductionVSAvoidmooring line configuration

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

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 design ensures safe and controlled disconnect and lowering of the buoy member under all conditions, including extreme loads, preventing structural damage and maintaining the buoy's position for vessel movement after disconnect, while allowing for maintenance and efficient reconnection.

Implementation Method 1

the length of the second section between said coupling point and its connection to the buoy member is chosen such that when the buoy member is received in the buoy receptacle with the first section connected to the turret structure and in a state for transmitting mooring forces, said second section is in a slack state not loaded by said mooring forces

Methodology Applied

Scientific EffectGravitation: Gravitation

Implementation Method 2

a buoy member having a plurality of passages each adapted to receive a riser, wherein the turret structure has a lower end comprising a buoy receptacle for detachably receiving the buoy member

Methodology Applied

Scientific EffectBuoyancy: Archimedes' Principle (Buoyancy)

Data Source

PatentUS8651040B2Disconnectable mooring system and method for disconnecting or reconnecting it

Publication Date: 2014.02.18 BLUEWATER ENERGY SERVICES BV (100 00)

AI summary

A disconnectable mooring system for a vessel is presented, comprising a moonpool in the vessel, a turret structure mounted for a rotation in said moonpool and a buoy member having a plurality of passages each adapted to receive a riser. The turret structure has a lower end comprising a buoy receptacle for detachably receiving the buoy member, wherein the mooring system further comprises a plurality of mooring lines for transmitting mooring forces and each have a lower end and an upper end connected to the seabed and the buoy member, respectively. The mooring lines each comprise a first section which in a disconnectable manner is connected to the turret structure and a second section connected to the first section at a coupling point and connected to the buoy member. Also methods for disconnecting and reconnecting such a mooring system are presented.