Multi-layer Thermometer Protection Tubes
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Solution Overview
Problem
Conventional thermocouple protection tubes react with each other at high temperatures, limiting the long-term protection of thermocouples in high-temperature environments, such as carbon-existing atmospheres, and affecting temperature measurement accuracy.
Innovation Solution
A thermometer design featuring multiple protection tubes with inert gas-filled spaces between them, where the inner and outer protection tubes are made of materials with low reactivity, such as Mo, W, Ta, Ir, graphite, C/C composite, and SiC, to prevent reactions and extend thermocouple lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protection tube is provided surrounding the thermocouple, then the thermocouple is protected from carbon reaction, but the protection tube material reacts with the thermocouple wires at high temperatures
Solution Approach 1:
The protection tube is divided into multiple layers with different materials (inner layer and outer layer) to provide different protection functions. The inner layer protects against carbon, while the outer layer protects against oxidation, preventing harmful reactions with the thermocouple wires
Solution Approach 2:
A coating layer is applied on the inner surface of the protection tube as an intermediary between the thermocouple wires and the protection tube material. This coating prevents direct contact and reaction between the thermocouple wires and the protection tube material at high temperatures
2Duration of action of stationary object
If conventional protection tubes are used in carbon-existing atmosphere, then short-term protection is provided, but the protection tube reacts with carbon at high temperatures limiting long-term protection
Solution Approach 1:
The protection tube is segmented into multiple layers with specific materials selected for their resistance to carbon reaction. The inner layer uses materials highly resistant to carbon, while the outer layer provides additional protection, enabling long-term operation in carbon-existing atmospheres
Solution Approach 2:
The protection tube is constructed as a composite structure with multiple materials (e.g., metal matrix composite, ceramic coating) that combine the advantages of each material to resist both carbon reaction and oxidation, extending the service life in harsh environments
3Reliability
If multiple protection tubes with different materials are used, then comprehensive protection is achieved, but the complexity of the device increases
Solution Approach 1:
The protection tube is divided into functional layers (inner layer and outer layer) where each layer has a specific protection function. This segmentation provides comprehensive protection while maintaining a relatively simple integrated structure that is easy to manufacture and install
Data Source
AI summary
A carbon atmosphere thermometer 10a has: a thermocouple having thermocouple wires 16, 18, a thermocouple temperature measuring junction 14, and an insulating tube 12; a first protection tube 20 surrounding the thermocouple, while at least partially spaced apart from the thermocouple wires 16, 18 and others of the thermocouple; and a second protection tube 22 surrounding the first protection tube 20, while at least partially spaced apart from the first protection tube 20. For this reason, it becomes feasible to protect the thermocouple from the external environment, while preventing the thermocouple from reacting with the first protection tube 20. Furthermore, it becomes feasible to protect the thermocouple and the first protection tube 20 from the external environment, while preventing the first protection tube 20 from reacting with the second protection tube 22.