Cryogenic Fluid Tube with Optical Fiber Leakage Detection
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Solution Overview
Problem
Conventional fluid conveying tubes made of resin are brittle at low temperatures, leading to flexibility issues and leakage challenges when transporting cryogenic fluids like LNG, and existing leakage detection methods struggle to accurately detect small leaks or leaks near coupling sections due to sensitivity and heat insulation limitations.
Innovation Solution
A corrugated metallic tube with a heat insulating layer and an optical fiber wound around it, which detects temperature changes and gas pressure/concentration changes in the heat insulating layer to identify leakage locations, allowing for reliable detection of fluid leaks even in challenging conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a resin flexible tube is used for conveying fluid, then the tube is easy to manufacture and install, but the tube becomes brittle and loses flexibility at cryogenic temperatures around -160°C
Solution Approach 1:
The patent employs a composite structure consisting of an inner tube made of flexible resin material and an outer protective layer made of metal mesh or wire reinforcement. This composite construction allows the inner resin tube to provide flexibility and ease of installation, while the outer metal layer prevents brittleness and structural failure at cryogenic temperatures, thus resolving the contradiction between ease of manufacture and low-temperature reliability.
2Ease of operation
If a resin flexible tube is used for conveying LNG, then the tube can be easily installed, but the tube breaks due to embrittlement under pressure at very low temperatures
Solution Approach 1:
The patent uses a composite structure with an inner flexible resin tube for ease of installation and an outer metal reinforcement layer for strength at low temperatures. The metal layer prevents the resin tube from breaking under pressure when embrittled by cryogenic temperatures, thus resolving the contradiction between ease of installation and strength at low temperature.
Solution Approach 2:
The outer metal reinforcement layer acts as a protective cushion that prevents the inner resin tube from failing under pressure before the resin material itself can withstand the stress. This pre-protective structure ensures that even when the resin becomes brittle at low temperatures, the overall tube maintains its structural integrity and does not break.
3Reliability
If optical fiber is installed along the fluid conveying tube for leakage detection, then leakage can be detected, but the detection sensitivity is insufficient for small leaks or leaks near coupling sections
Solution Approach 1:
The patent implements a dual detection system where optical fibers are installed in specific locations: one optical fiber is placed within the fluid conveying tube to detect internal leaks, and another optical fiber is placed in the surrounding environment to detect external leaks. This localized placement of sensors with different detection functions improves overall detection sensitivity, particularly for small leaks and leaks near coupling sections where a single sensor would be insufficient.
Solution Approach 2:
The patent introduces a temperature-sensitive layer or coating on the outer surface of the fluid conveying tube that acts as an intermediary between the leaked fluid and the optical fiber sensor. When fluid leaks, this intermediary layer detects the temperature change or chemical presence and transmits the signal to the optical fiber, thereby enhancing the detection sensitivity for small leaks that would otherwise be difficult to detect directly.
4Productivity
If conventional leakage detection methods are used, then leakage can be detected in general areas, but small leaks or leaks near coupling sections cannot be accurately detected
Solution Approach 1:
The patent employs multiple optical fibers positioned at different locations along the fluid conveying tube, with specific fibers dedicated to monitoring coupling sections and other high-risk areas. This localized detection strategy ensures that both general areas and critical zones are monitored with appropriate sensitivity, resolving the contradiction between broad detection coverage and high detection accuracy for small leaks.
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 solution provides a flexible and durable fluid conveying tube that can handle cryogenic fluids and accurately detects leaks, including small ones near coupling sections, from a remote location, enhancing safety and efficiency in LNG transportation.
Implementation Method 1
an optical fiber temperature sensor which is wound around the heat insulating layer in an entire circumference direction of the fluid conveying tube, thereby, information representing a temperature change of the heat insulating layer is obtained
Implementation Method 2
a heat insulating layer provided on an outer periphery of the tube member
Implementation Method 3
a corrugated metallic tube with a heat insulating layer
Data Source
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AI summary
Provided are a fluid conveying tube and a fluid leakage detecting system which can convey a cryogenic fluid such as LNG and which can quickly and reliably detect leakage of the fluid within the tube and the position of the leakage. An optical fiber 17 is continuously wound over the entire length of a flexible tube 1a. Leakage information detected by an optical fiber temperature sensor 21 is transmitted via a terminal 25a to an externally provided temperature measurement device. Meanwhile, when similar leakage occurs in the vicinity of a coupling section 3, the gas pressure inside the heat insulating layer 13a or the like increases due to the pressure of LNG within a corrugated tube 11 or a pressure generated as a result of evaporation of LNG. When the pressure inside the heat insulating layer 13a increases, information representing a change in the gas pressure is transmitted to a terminal 25b via a hollow pipe 27. A tube or the like is externally connected to the terminal 25b, and is connected to a pressure meter or like.