Cylindrical Hull FPSO Motion Suppression
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Solution Overview
Problem
Conventional offshore vessels for petroleum production and storage face challenges in harsh environments due to unstable motion behavior, limited storage capacity, high fabrication costs, and complex structural designs, which affect safety and operational efficiency.
Innovation Solution
A spread moored vessel with a longitudinal hull design featuring a bow, midbody, and stern, equipped with motion suppressing elements that reduce heave, pitch, and roll motions, allowing for uniform motion independent of wave direction and enabling reduced mooring complexity and increased storage capacity, while being scalable and fabricable using standard shipbuilding facilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a conventional ship-shaped FPSO is used, then storage capacity can be large, but motion behavior becomes unstable in harsh environments requiring complex weather vaning facilities
Solution Approach 1:
The patent applies a cylindrical hull form instead of a conventional ship-shaped hull. This curved, symmetric geometry provides uniform motion characteristics independent of wave direction, eliminating the need for complex weather vaning facilities while maintaining large storage capacity through the cylindrical cargo tanks arranged within the hull.
Solution Approach 2:
The patent introduces asymmetric bilge boxes extending laterally from the cylindrical hull to suppress roll motion. This asymmetric addition to the symmetric cylindrical form creates motion suppression without requiring the vessel to actively weather vaning, resolving the contradiction between large storage capacity and stable motion behavior.
2Stability of the object's composition
If a semi-submersible design is used, then motion behavior becomes favorable and uniform, but storage capacity is limited and structural complexity increases
Solution Approach 1:
The patent uses a cylindrical hull that serves multiple functions: it provides the main structural form, contains large-volume cargo tanks for storage, and creates favorable motion characteristics through its geometric properties. This multi-functionality achieves both uniform motion behavior and large storage capacity without the limitations of semi-submersible designs.
3Stability of the object's composition
If box-shaped or cylindrical units are used, then uniform motion behavior is achieved, but fabrication complexity and cost increase due to non-standard shapes
Solution Approach 1:
The patent maintains a simple cylindrical hull form for the main structure to ensure uniform motion behavior, while applying local modifications such as bilge boxes only where needed for roll suppression. This localized approach to complexity allows standard fabrication methods to be used for the majority of the structure, reducing overall fabrication cost while maintaining motion stability.
4Stability of the object's composition
If motion suppressing elements are added to cylindrical designs, then favorable motions are achieved, but deck area-to-storage-volume ratio decreases
Solution Approach 1:
The patent extends bilge boxes laterally from the cylindrical hull below the waterline to suppress roll motion, rather than adding vertical structures that would reduce deck area. This lateral extension in the horizontal dimension achieves motion suppression while preserving the deck area-to-storage-volume ratio by not encroaching on the available deck space.
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 design provides enhanced stability, reduced motion sensitivity, increased storage capacity, and lower fabrication costs, enabling safe and efficient operation in both benign and harsh conditions, with improved topside load capacity and deck area, and the ability to use free-hanging steel catenary risers.
Implementation Method 1
The motion suppressing element causes a significant reduction of undesired motion of the vessel, especially heave, pitch and roll
Implementation Method 2
The motion suppressing element causes a significant reduction of undesired motion of the vessel, especially heave, pitch and roll
Data Source
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AI summary
The present invention relates to a spread moored vessel for production and/or storing of hydrocarbons. The vessel comprises a laterally extending main deck, a symmetrical mooring arrangement for mooring the vessel to a seabed when the vessel is floating in a body of water and a longitudinal hull. The longitudinal hull further comprises a bow, a midbody, a stern, and a motion suppressing element protruding out from the longitudinal hull, below the vessel's maximum draught. The ratio between a maximum length (Lw1) and a maximum breadth (Bw1) of the longitudinal hull, at the vessel's maximum draught, is between 1.1 and 1.5. The specific hull shape with the particular length/breadth ratio and the motion suppressing element allows for favorable and uniform motions regarding of wave direction in relation to vessel heading.