Flexible Line Access System for Offshore Vessel Transfer
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Solution Overview
Problem
Offshore wind turbines face reduced availability and increased maintenance costs due to safety restrictions during harsh weather conditions, as existing access systems are either expensive, fragile, or unsuitable for reaching high platforms and evacuating injured personnel.
Innovation Solution
A method utilizing a flexible line for safe access between a vessel and an offshore structure, allowing for self-stabilization and shock load damping, enabling access and evacuation even in difficult weather, using a simple and cost-effective setup with small boats, and incorporating a motor-driven system with safety features to maintain line tension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a motion compensation platform or Stewart platform is used to actively compensate wave movements, then safety and access reliability are improved, but system cost and complexity increase significantly
Solution Approach 1:
A flexible line acts as an intermediary element between the moving vessel and the static offshore structure. The line absorbs and dampens relative movements and shock loads, enabling safe access without requiring complex motion compensation systems. The line's flexibility and sagging configuration allow it to mediate the interaction between the two structures, transferring personnel and equipment while accommodating wave-induced motions.
2Adaptability or versatility
If a variable length gangway with articulate connection is used, then access flexibility is improved, but system cost and ship size requirements increase
Solution Approach 1:
The system employs a flexible line instead of a rigid gangway structure. This flexible element can accommodate various vessel positions and wave conditions while maintaining access capability. The line's flexibility allows it to adapt to different operational scenarios without requiring complex articulation mechanisms or large support structures.
3Length of stationary object
If the gangway is made long enough to reach the platform, then access reach is improved, but system cost and structural requirements increase
Solution Approach 1:
The flexible line is deployed in a sagging, curved configuration rather than a straight rigid structure. This curved arrangement allows the line to reach the platform entrance effectively while absorbing shock loads and accommodating vessel movements. The sagging shape creates a gradual transition that reduces impact forces compared to a taut straight line.
4Ease of operation
If direct contact between moving vessel and static offshore structure is made, then access simplicity is improved, but safety risks increase due to shock loads and impact forces
Solution Approach 1:
The flexible line is pre-configured with sufficient sag and length to absorb shock loads and impact forces before they can be transmitted to the vessel or offshore structure. This beforehand cushioning effect protects both structures from damaging forces while maintaining simple access operations. The line's elasticity and slack configuration provide inherent shock absorption capability.
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
Enables safe and cost-effective access to offshore structures under various weather conditions, reducing maintenance downtime and allowing for efficient evacuation of personnel, while avoiding sudden shock loads and ensuring safe distance between moving and static structures.
Implementation Method 1
The line will sag under its own weight. As a result, sudden shock loads and impact loads by sea induced motion are damped.
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
Method of transferring a person or a load between a vessel and an offshore structure, comprising the step of establishing a connection by at least one line between the vessel and the offshore structure, which line is stretched, and subsequently a transport member is guided along the stretched line to move between the vessel and the offshore structure. The line can for example be stretched by driving the vessel to move away from the offshore structure, e.g. astern, e.g., in part load.