Jack-up Platform Leg Preloading for Crane Stability
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Solution Overview
Problem
The increasing size of offshore constructions, such as wind turbines, poses a challenge for jack-up platform units due to the significant loading on legs during crane or cantilever operations, which can lead to uncontrolled settlement or collapse, as the loading may exceed preloading values, compromising stability.
Innovation Solution
A method that involves preloading the legs and applying a torque to the hull by differentially loading pairs of diagonally opposed legs, allowing for increased operational margin and crane capacity without structural modifications, by adjusting load distribution to accommodate the location of cranes or cantilevers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If preloading is applied to stabilize the platform, then stability is improved, but the operational margin for crane operations is reduced because the preloading load approaches the maximum allowable load
Solution Approach 1:
The platform is divided into multiple legs, and the loading is segmented and distributed differentially across these legs. By applying preloading selectively to specific legs rather than uniformly to all legs, the method creates a segmented load distribution that optimizes both stability and operational margin for crane operations.
Solution Approach 2:
Different legs are assigned different load levels during preloading. The method applies local quality by selectively loading specific legs more heavily while keeping other legs lighter, creating a non-uniform load distribution that accounts for the specific operational requirements and crane positions.
2Productivity
If the crane capacity is increased to handle larger offshore constructions, then productivity is improved, but the leg loading increases which may exceed the preloading values and compromise stability
Solution Approach 1:
The load distribution on the legs is made dynamic and adjustable. The method allows for flexible redistribution of loads between legs based on the specific crane operations being performed, enabling the platform to adapt to varying operational demands while maintaining stability.
Solution Approach 2:
The load parameters on different legs are changed and optimized. By adjusting the load distribution parameters - specifically making the load on legs with cranes lower than on other legs - the method enables higher crane capacities while maintaining overall platform stability.
3Ease of operation
If equal load is applied to all legs during preloading, then simplicity of operation is improved, but the operational margin for crane operations is reduced
Solution Approach 1:
The preloading process intentionally creates asymmetric load distribution rather than symmetric equal loading. By applying different load levels to different legs based on their proximity to cranes and operational requirements, the method optimizes the operational margin while maintaining reasonable operational simplicity.
Data Source
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AI summary
Method for stabilizing a jack-up platform unit, the unit including a hull, a plurality of legs which are extendible from and/or through the hull and which are arranged to support the platform unit during off-shore operations, and a jacking system arranged to move the legs between a transport position and an operational position, wherein the jacking system is also arranged to move the hull along the plurality of legs between a floating position and an operational position, the method comprising the steps of lowering the plurality of legs until the legs stand on or in the seabed, raising the hull substantially above the sea surface, temporarily applying a preloading on the plurality of legs, further raising the hull to an operational height above the sea surface.