Turret Mooring System Collar Deck Arrangement
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Solution Overview
Problem
As offshore vessels such as FPSO and FLNGs have increased in size, the elevated topside process deck and bearing arrangement have resulted in higher bending forces and moments, necessitating heavier and more complex reinforcement of axial bogies and radial wheels in turret mooring systems.
Innovation Solution
The turret mooring system positions the radial wheels and axial bogies lower in the vessel's hull, with a collar deck above the axial bogies and below the topside process deck, reducing the lever arm and bending forces, allowing for lighter and less reinforced structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the topside process deck and bearing arrangement are elevated to accommodate larger vessel sizes, then the vessel can handle increased processing capacity, but the bending forces and moments on the bearing arrangement increase significantly
Solution Approach 1:
The patent introduces a collar deck as an intermediate structural element between the topside process deck and the bearing arrangement. This creates a new vertical dimension in the load path, allowing the bearing arrangement to be positioned lower while still supporting the elevated topside process deck. The collar deck acts as a load transfer interface, distributing forces through this intermediate level and reducing the direct bending moments on the bearing arrangement.
2Strength
If the bearing arrangement is reinforced to handle increased bending forces, then the structural strength is improved, but the weight and complexity of the turret and support structures increase
Solution Approach 1:
The patent segments the support structure into distinct functional components: the bearing arrangement at the bottom, the collar deck as an intermediate element, and the topside process deck at the top. This segmentation allows each component to be optimized independently - the bearing arrangement can be smaller and lighter because it doesn't need to directly support the full height and associated bending moments of the elevated topside deck.
3Device complexity
If the radial wheels are positioned higher to support the elevated bearing arrangement, then the structural configuration is simplified, but the radial wheels are exposed to seawater causing premature deterioration
Solution Approach 1:
The collar deck serves as an intermediary element that decouples the positioning of the radial wheels from the elevation of the topside process deck. The radial wheels can be positioned at their optimal lower location protected from seawater, while the collar deck mediates the load transfer to support the elevated topside structure. This intermediary structure allows the radial wheels to remain below the seawater exposure zone.
4Length of stationary object
If the collar deck is positioned close to the topside process deck, then the vertical space is reduced, but the lever arm and bending forces on the bearing arrangement remain large
Solution Approach 1:
The patent utilizes the vertical dimension strategically by positioning the collar deck at an optimized intermediate height rather than close to the topside process deck. This vertical positioning creates a favorable lever arm geometry that reduces bending moments on the bearing arrangement. The collar deck's elevated position relative to the bearing arrangement allows for a more efficient force distribution throughout the structure.
Data Source
Figure 1A
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Figure 2
AI summary
A turret mooring system for a floating process and storage offloading, FPSO, vessel or a FLNG vessel 150; 250 includes a turret structure 120 and a bearing support structure 110, 115. The turret structure is to be placed within a moonpool 155 in a hull of the vessel and rotatably held within the moonpool via the bearing support structure. The bearing support structure includes a radial support 115 and an axial support 110. The radial support includes a plurality of radial wheels, and the axial support includes a plurality of axial bogies. The vessel has a topside process deck 160 and the turret structure includes a collar deck 125. The collar deck is positioned vertically above an upper side LI of the axial support and below an elevation of the topside process deck 160. An FPSO or FLNG vessel is provided which includes the turret mooring system.