Leg-Mounted Ballast Tanks for Jack-Up Rig Preload
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Solution Overview
Problem
Jack-up rigs face limitations in preloading their legs due to the weight of water ballast, which reduces the capacity for additional equipment and quarters on the hull, and increases stress on jacking systems.
Innovation Solution
The implementation of ballast tanks moveably coupled to the support legs, allowing for adjustable preload and buoyancy, reducing the need for water ballast on the hull, thereby enabling greater flexibility in equipment capacity and stress reduction on jacking systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If water ballast is added to the hull to preload the legs, then the legs are securely driven into the sea floor, but the total load supported by the hull and jacking systems increases, reducing capacity for additional equipment and quarters
Solution Approach 1:
The invention divides the ballast system into separate modular tanks that can be independently positioned along the legs. Each ballast tank is segregated from the hull and can be moved to specific locations on the legs, allowing the ballast weight to be distributed and applied directly to the legs rather than being concentrated in the hull. This segmentation enables independent control of ballast placement to optimize leg preload while minimizing hull load.
Solution Approach 2:
The invention extracts the ballast function from the hull structure and relocates it to the legs. By removing the traditional hull-mounted ballast tanks and replacing them with leg-mounted ballast tanks, the ballast weight is taken out of the hull load path and directly applied to the legs through the leg structure. This extraction resolves the contradiction by maintaining leg preload functionality while eliminating the increase in total hull load.
2Ease of operation
If water ballast is pumped into the hull to provide preload, then the penetration of legs into the sea floor is facilitated and controlled, but the additional weight reduces the capacity available for other equipment and quarters on the hull
Solution Approach 1:
The invention implements dynamic ballast tanks that can be moved along the legs and positioned at different locations. The ballast tanks are not fixed but can be dynamically repositioned to optimize leg preload during different operational phases. This dynamic capability allows for precise control of leg penetration while maintaining flexibility in equipment configuration on the hull, as the ballast system can be adjusted without adding permanent weight to the hull structure.
3Force
If the hull supports both the drilling rig and additional water ballast, then the legs can be preloaded, but the jacking systems that move the legs relative to the hull experience increased stress
Solution Approach 1:
The invention introduces the leg structure as an intermediary between the ballast weight and the jacking system. Instead of the ballast weight being supported by the hull and requiring the jacking system to lift both the hull and ballast, the ballast tanks are mounted on the legs themselves. The leg structure mediates the force transmission, allowing the ballast weight to be directly applied to the leg preload while the jacking system only needs to move the lighter hull structure, thereby reducing stress on the jacking systems.
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 solution allows for enhanced preload and buoyancy control, increasing the capacity for additional equipment and quarters on the hull while reducing stress on jacking systems, improving the overall operational efficiency and stability of the jack-up rig.
Implementation Method 1
The additional weight provided by the water ballast facilitates and controls the penetration of the legs into the sea floor
Implementation Method 2
The invention relates to offshore platforms for drilling and production operations... jack-up rig with leg-supported ballast loads
Data Source
AI summary
A jack-up rig for offshore operations comprises a hull. In addition, the rig comprises a support leg moveably coupled to the hull. The support leg has a central axis, an upper end, and a lower end opposite the upper end. Further, the support leg is adapted to be axially raised and lowered relative to the hull. The rig also comprises a ballast tank movably coupled to the support leg. The ballast tank is adapted to be axially raised and lowered relative to the support leg and the hull.