LNG Tank Isolation Valves in Sealed Cofferdam
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Solution Overview
Problem
The confinement and leakage risks of liquefied natural gas (LNG) in ship propulsion systems pose safety challenges, requiring effective isolation and containment measures to prevent accidents and comply with regulatory standards like the IGF Code.
Innovation Solution
A floating structure design featuring a membrane tank integrated into the ship's shell, with an intermediate carrier wall and sealed isolation valves, optimized to minimize volume usage and enhance safety through a multilayer thermal insulation and waterproof membrane structure, and a connection device enclosed in a sealed, liquefied natural gas-resistant material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tank containing liquefied natural gas is placed below the first deck with isolation valves on pipes connecting to management device, then safety and isolation capability are improved, but the structure becomes more complex and installation becomes more difficult
Solution Approach 1:
The connection device with isolation valves is nested within a sealed enclosure that is integrated into the hull structure. The enclosure is positioned within the space between the intermediate load-bearing wall and the first deck, effectively nesting multiple functional elements (tank, connection device, enclosure) within each other to reduce overall structural complexity while maintaining safety isolation.
Solution Approach 2:
The patent combines the connection device, isolation valves, and sealed enclosure into a single integrated assembly. The enclosure serves multiple functions: it seals the isolation valves, creates a cofferdam space for safety, and integrates with the hull structure. This merging of functions reduces the number of separate components and simplifies installation.
2Reliability
If isolation valves are placed in a sealed enclosure (connection device) below the first deck, then leakage risk is reduced and safety is improved, but the useful volume of the floating structure is decreased
Solution Approach 1:
The connection device and sealed enclosure are positioned in the vertical space between the intermediate load-bearing wall and the first deck, utilizing the third dimension (height) rather than occupying horizontal space. This vertical arrangement allows the safety enclosure to exist in an otherwise unused space, minimizing impact on the useful volume available for cargo or other purposes.
Solution Approach 2:
The sealed enclosure containing isolation valves is nested within the existing structural space of the hull, specifically within the region between the intermediate load-bearing wall and the first deck. This nesting approach allows the safety infrastructure to be accommodated within the existing structural envelope without requiring additional volume that would reduce useful space.
3Temperature
If a membrane tank with multilayer thermal insulation and waterproof membrane is used, then thermal protection and waterproofing are improved, but manufacturing complexity increases
Solution Approach 1:
The patent employs a membrane tank construction with flexible waterproof membranes as the primary containment barrier. These thin film membranes are applied over the thermal insulation layers, providing both waterproofing and thermal protection in a integrated manner. This approach simplifies manufacturing compared to rigid multi-component systems, as the membranes can be installed as continuous layers over the prepared substrate.
Solution Approach 2:
The tank structure uses composite construction with distinct layers: thermal insulation material as the core, waterproof membrane as the protective outer layer, and integration with the hull structure. This composite approach allows each layer to perform its specific function optimally while the combination provides comprehensive protection. The modular nature of composite materials facilitates easier manufacturing and assembly compared to monolithic structures.
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
The design effectively isolates the LNG tank from the management device, creating a secure cofferdam and minimizing the risk of leakage, while optimizing the useful volume and enhancing fire protection, thus addressing safety concerns and regulatory compliance.
Implementation Method 1
The walls of the tank comprise, successively from the outside to the inside of the tank, at least one thermal insulation layer carried by, and preferably anchored to an inner surface of said hull and by a lower surface of the intermediate load-bearing wall
Implementation Method 2
at least one waterproof membrane disposed on an inner surface of said thermal insulation layer
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
Floating structure comprising at least a first bridge (11) and an intermediate load-bearing wall (12), the floating structure comprising a tank (1) suitable for containing liquefied combustible gas and arranged below the intermediate load-bearing wall (12), at least one pipe (2, 3) connecting the tank (1) to the management device (7) and a connection device (5) comprising one or more isolation valves (4) arranged on the one or more pipes (2, 3) and an enclosure (6) enveloping the one or more isolation valves (4) in a sealed manner, in which the tank (1) is a tank with a membrane integrated into the shell and the connection device (5) is arranged above the intermediate load-bearing wall (12) and at least partially under the first bridge (11) in a space set up as a cofferdam.