Offshore Platform Deck Removal Using Pre-Tensioned Rods
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Solution Overview
Problem
Offshore heavy module removal poses challenges due to obsolete lifting points, uncertain weight, and center of gravity evaluation on modified structures, along with adverse weather and stability issues during lifting operations.
Innovation Solution
A crane vessel system and method utilizing pre-tensioned tension rods to lift offshore platforms from underneath, avoiding tensile stresses on columns and using a spreader bar to balance lifting forces, with a mapping system for adjusting rod length and force distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional lifting methods using marine lever or standard barges are used, then lifting capability is achieved, but the risk of overstressing existing structures increases and operation safety decreases
Solution Approach 1:
Instead of lifting the module from above using traditional crane methods that apply tensile loads to columns, the invention lifts the module from below using reaction forces applied to the deck. This inverts the lifting direction and load path, avoiding tensile stresses on columns while maintaining structural integrity during removal operations
Solution Approach 2:
The invention introduces an intermediate lifting system comprising lifting beams, hydraulic jacks, and tensioning devices that act as mediators between the crane vessel and the module. This intermediate system distributes lifting forces through the deck structure rather than directly loading columns, reducing stress concentration and preventing structural damage
2Productivity
If multiple lifting operations are performed to remove module parts, then complete removal is achieved, but productivity decreases and time consumption increases
Solution Approach 1:
The invention combines multiple lifting operations into a single integrated lifting action. By establishing a comprehensive lifting system that engages multiple lifting points simultaneously across the module, all module components are lifted together in one operation rather than requiring sequential removal of individual parts, significantly improving productivity and reducing time loss
3Ease of operation
If new lifting points are created on modified structures, then lifting capability is achieved, but manufacturing complexity increases and structural integrity risk increases
Solution Approach 1:
The invention performs preliminary assessment and preparation by evaluating existing structural elements before lifting operations. Load path analysis is conducted in advance to identify suitable existing structures that can serve as lifting points, avoiding the need for complex modifications. This preliminary action ensures both ease of operation and maintains structural integrity by utilizing proven load-bearing paths
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
Enables faster and safer lifting operations without overstressing existing structures, reducing the risk of lifting failure and minimizing the need for new lifting points, while maintaining structural integrity and stability.
Implementation Method 1
pre-tensioning a plurality of tension rods with a view to applying a compressive action to said payload
Implementation Method 2
A plurality of tension rods 13, connecting said lower lifting device 7 and said at least one upper lifting device 10
Implementation Method 3
The method comprises the step of welding at least one lower lifting device 7 to a welding portion 9 of said at least one column 6
Implementation Method 4
for lifting a payload 2 of an offshore platform 3
Implementation Method 5
at least one crane 43 hanging at least one assembly 1 for lifting a payload 2
Data Source
AI summary
A method for lifting a payload of an offshore platform is provided. The offshore platform comprises a support structure supporting the payload. The payload includes a main deck and a column directly connected to the support structure, the column supporting the main deck. The method includes coupling a plurality of tension rods to a lower lifting device, having a welding surface weldable to a welding portion of the column and an upper lifting device having a coupling interface such that the plurality of tension rods connect the lower lifting device and the upper lifting device. The plurality of extendable tension rods can extend along a rod direction between the lower lifting device and the upper lifting device to separate the payload from the support structure. At least some of the tension rods of the plurality of tension rods are pre-tensioned to exert a compressive action to the payload.