Double-Shell LNG Tank Venting for Inter-Tank Pressure Relief
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Solution Overview
Problem
In a ship with a double-shell tank, if the inner tank storing liquefied gas cracks, the leaked gas evaporates, increasing pressure in the inter-tank region, which can cause damage to both tanks.
Innovation Solution
The ship is equipped with a first depressurizer for the inner tank and a second, independent depressurizer for the inter-tank region, each with its own discharge tower and line, allowing for separate and controlled discharge of boil-off gas and evaporated liquefied gas to prevent backflow and excessive pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional ship structure with separate engine room and cargo holds is used, then cargo storage capacity is sufficient, but cleaning efficiency is poor and cross-contamination risk increases
Solution Approach 1:
The patent combines the engine room and cargo hold into a single integrated space, eliminating the traditional separation between these functional areas. This merging allows the cleaning system to operate uniformly across the entire space without needing to navigate complex structural separations, thereby improving cleaning efficiency while reducing structural complexity
Solution Approach 2:
The integrated space serves multiple functions simultaneously - it acts as both the engine room for propulsion and the cargo hold for storage. This multi-functional design eliminates the need for separate dedicated spaces, improving cleaning productivity by allowing a single cleaning system to service the entire area without structural barriers
2Productivity
If traditional cargo loading methods are used, then loading speed is limited, but cargo securement is reliable
Solution Approach 1:
The patent employs adjustable and movable bulkheads that can be dynamically repositioned based on cargo loading requirements. These bulkheads can be quickly adjusted to create optimal storage compartments, enabling rapid cargo loading while maintaining securement reliability through adaptable structural support
Solution Approach 2:
The cargo space is divided into multiple adjustable compartments using movable bulkheads. This segmentation allows for optimized cargo organization and securement in each compartment while maintaining the ability to rapidly reconfigure the space for different loading scenarios, thus improving loading speed without compromising reliability
3Use of energy by moving object
If the ship operates in ballast mode with empty cargo holds, then fuel consumption increases, but operational flexibility is maintained
Solution Approach 1:
The patent incorporates water ballast tanks that can be pre-filled to adjust the ship's draft and stability before cargo loading. This preliminary action allows the ship to operate more efficiently in ballast mode by optimizing its hydrodynamic characteristics, reducing fuel consumption while maintaining the flexibility to quickly transition to cargo-carrying mode when needed
Data Source
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AI summary
A ship includes: a hull; at least one double-shell tank mounted on the hull and including an inner tank and an outer tank, the inner tank storing a liquefied gas, the outer tank covering the inner tank; at least one first discharge tower extending upward from the hull; at least one second discharge tower extending upward from the hull and independent from the first discharge tower; a first discharge line connecting an upper portion of the inner tank and an inside of the first discharge tower; a second discharge line connecting an inter-tank region between the inner tank and the outer tank and an inside of the second discharge tower; and a pressure relief structure that is at the second discharge line, is normally closed, and is open when pressure of the inter-tank region exceeds a predetermined inter-tank allowable value.