Foldable Spar Hull Belly Strake Installation
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Solution Overview
Problem
Spar-type floating oil and gas platforms with large diameter hulls face challenges in installing belly strakes due to limited water depth, requiring complex and costly procedures, including underwater fabrication and heavy lift vessel operations, which increase time and costs.
Innovation Solution
A foldable belly strake system for spar hulls that can be installed in a deep water pit, allowing the hull to be rotated for access, with strake panels and frames that can be folded and unfolded for transport and final positioning, reducing the need for offshore installation and heavy lift vessels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If belly strakes are installed on spar hulls with large diameter, then vortex-induced vibrations are reduced and stability is improved, but installation complexity and cost increase due to limited water depth requirements
Solution Approach 1:
The belly strake is divided into multiple panels that can be folded together like an accordion structure. This segmentation allows the strake to be compact during transport and then expanded to full size when installed on the spar hull, eliminating the need for complex heavy lift vessel operations while still providing the stability benefits
Solution Approach 2:
The belly strake employs a foldable structure with hinges and fasteners that transitions from a compact folded state during transport to a fully extended rigid state during installation. This dynamic configuration allows the same structure to meet different operational requirements (transport vs. installation) without requiring separate systems
2Ease of manufacture
If belly strakes are installed during wet tow transport, then installation can be performed in shallow water, but the strake panels cannot be properly installed due to insufficient water depth
Solution Approach 1:
The belly strake panels are pre-assembled in a folded configuration on the quayside before the spar hull is transported to the installation site. This preliminary assembly in controlled shallow water conditions allows the structure to be prepared in advance, and then the folded strake is attached to the hull during transport without requiring deep water
3Length of moving object
If heavy lift vessels are used for transporting spar hulls, then large diameter hulls can be transported, but installation costs and logistical complexity increase
Solution Approach 1:
By segmenting the belly strake into foldable panels, the system eliminates the need for heavy lift vessels during strake installation. The compact folded structure can be handled with standard quayside equipment, and the spar hull can be transported using conventional towing methods rather than requiring specialized heavy lift capability
Data Source
AI summary
A spar hull for a floating vessel can include a hard tank having a belly portion, a fixed strake coupled to the outer surface of the tank and a folding strake coupled to the belly portion of the tank, the folding strake having one or more strake panels and one or more support frames. A method for installing folding belly strakes on a spar hull may include providing a floating spar hull having a hard tank with a belly side, rotating the spar so that the belly side is in a first workable position, coupling at least one folding strake to the belly side of the spar, and coupling the strake in a folded position for transport. The method may include positioning the spar hull offshore in a transport position, upending the spar hull, unfolding the strake, fixing the strake in the unfolded position and installing the spar hull.