Offshore Cantilever With Stationary Swivel Axis
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Solution Overview
Problem
Existing offshore systems with moveable and rotatable cantilevers face high bending moments and loads due to the cantilever's positioning, which complicates the design and increases structural demands, especially when the swivel axis moves with the cantilever.
Innovation Solution
An offshore system featuring a cantilever that is moveable in a longitudinal direction and rotatable about a substantially vertical swivel axis, utilizing a single sliding and swivel assembly with a stationary swivel axis on the deck, allowing the cantilever to maintain a constant bending arm and reduce loads through actuators and a slew bearing configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the cantilever is positioned beyond the deck to extend operational reach, then the operational capability is improved, but the bending moments and loads on the supporting structure increase significantly
Solution Approach 1:
The patent implements a moveable cantilever system that can dynamically adjust its position between retracted and extended states, allowing the operational reach to be changed as needed while controlling the loads by retracting when not in use
2Adaptability or versatility
If the swivel axis moves along with the cantilever, then the rotational functionality is improved, but the bending arm length varies causing loads to exceed limits
Solution Approach 1:
The patent separates the swivel axis function from the cantilever by providing a stationary swivel axis on the deck independent of the cantilever's longitudinal position, ensuring the bending arm length remains constant while the cantilever moves
Solution Approach 2:
The patent introduces a sliding assembly as an intermediary component between the cantilever and the stationary swivel axis, allowing the cantilever to move longitudinally while maintaining a constant distance from the swivel axis through the sliding mechanism
3Force
If a single sliding and swivel assembly is used with a stationary swivel axis, then the loads are kept within limits, but the device complexity increases
Solution Approach 1:
The patent combines the sliding function and swivel function into a single integrated sliding and swivel assembly, where the sliding part allows longitudinal movement and the fixed part provides the stationary swivel axis, merging two functions into one compact unit
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 configuration keeps loads within manageable limits, provides design flexibility, minimizes the impact on cables and hoses, and maintains consistent alignment for subsea operations, enhancing the structural integrity and operational efficiency of the offshore system.
Implementation Method 1
the fixed part comprises a stationary part and a rotatable part with a bearing in between the stationary part and the rotatable part forming the substantially vertical swivel axis
Implementation Method 2
the sliding part is arranged to slide in longitudinal direction of the cantilever relative to the fixed part when the cantilever moves in the longitudinal direction
Implementation Method 3
a sliding assembly is arranged at the other end of the cantilever supporting the cantilever and allowing the cantilever to slide in longitudinal direction of the cantilever relative to the deck during movement of the cantilever in longitudinal direction, and to slide in a transverse direction perpendicular to the longitudinal direction relative to the deck during rotation of the cantilever relative to the deck
Data Source
AI summary
An offshore system includes a vessel having a deck; a cantilever which is mounted on the deck and which is moveable in a longitudinal direction of the cantilever relative to the deck between a retracted position and an extended position, and which is rotatable relative to the deck about a substantially vertical swivel axis; and actuators to move the cantilever in longitudinal direction and to rotate the cantilever about the swivel axis. The swivel axis is provided by a single sliding and swivel assembly arranged at one end of the cantilever, including a fixed part mounted to the deck and a sliding part mounted to the cantilever. The sliding part is arranged to slide in longitudinal direction of the cantilever relative to the fixed part when the cantilever moves in the longitudinal direction. The fixed part and/or the combination of fixed part and sliding part are configured to form the swivel axis allowing the cantilever to rotate relative to the deck. A sliding assembly is arranged at the other end of the cantilever supporting the cantilever and allowing the cantilever to slide in longitudinal direction of the cantilever relative to the deck during movement of the cantilever in longitudinal direction, and to slide in a transverse direction perpendicular to the longitudinal direction relative to the deck during rotation of the cantilever relative to the deck.