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 in ship channels, requiring complex and costly procedures, including underwater fabrication and heavy lift vessel operations, which increase installation time and costs.
Innovation Solution
A foldable belly strake system for spar hulls that can be selectively folded and unfolded, allowing installation on the quayside or offshore, reducing the need for heavy lift vessels and minimizing offshore swage operations, with support frames and panels that can be temporarily coupled and unfolded during transport and final positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If belly strakes are installed on large diameter spar hulls using conventional methods, then the strakes can be properly installed, but the installation requires heavy lift vessels and complex underwater fabrication procedures
Solution Approach 1:
The belly strake is designed as a foldable structure that can transition between a compact folded state for transport and an extended installed state for operation. The strake includes foldable panels connected by hinges, allowing it to be dynamically reconfigured during installation without requiring heavy lift vessels or complex underwater fabrication procedures.
Solution Approach 2:
The belly strake is divided into multiple panels that can be folded and unfolded independently. This segmentation allows the strake to be transported in a compact form and then deployed into its full operational configuration on-site, eliminating the need for heavy lift vessels and reducing installation complexity.
2Reliability
If belly strakes are installed with full extension around the hull, then vortex-induced vibrations are effectively reduced, but the installation becomes impossible in shallow water depths
Solution Approach 1:
The foldable belly strake can be installed in a compact folded state in shallow water and then unfolded to its full extended configuration to provide complete vortex-induced vibration reduction. The dynamic folding mechanism allows the strake to adapt to both transport constraints and operational requirements.
Solution Approach 2:
The foldable strake panels are nested within each other in the folded configuration, allowing the full-length strake to be installed in shallow water depths and then unfolded to provide complete coverage around the hull for effective vortex-induced vibration reduction.
3Device complexity
If conventional fixed belly strakes are used, then the structure is simple and robust, but the installation time and costs increase due to heavy lift vessel requirements
Solution Approach 1:
The foldable belly strake structure, while more complex than fixed strakes, enables rapid installation without heavy lift vessels. The strake can be pre-assembled in a folded state and quickly deployed on-site, significantly reducing installation time and costs compared to conventional fixed strake installation methods.
4Ease of operation
If the spar is transported on a heavy lift vessel with supports, then the transport is feasible, but the belly strakes cannot be installed on the supported portions of the hull
Solution Approach 1:
The foldable belly strake can be installed in a compact folded state on the supported portions of the hull during transport, and then unfolded after the supports are removed to provide complete coverage. This dynamic configuration allows both feasible transport and complete strake installation.
Data Source
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Figure 3A~3B
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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.