Multi-Hoop Ceramic Tube Joining Device
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Solution Overview
Problem
The challenge in ethylene production is the unreliable connection between ceramic and metal tubes due to differing thermal expansion coefficients, leading to sealing issues and potential separation, especially in high-temperature environments like ethylene production furnaces, where existing connection devices fail to provide a mechanically reliable and waterproof seal over a wide temperature range.
Innovation Solution
A connection device featuring hoops with carefully selected expansion coefficients, where a first hoop with a lower expansion coefficient than the ceramic tube is hooped by a second hoop with an even lower expansion coefficient, ensuring a compressive force is maintained to prevent separation and leakage, and using materials like silicon carbide for the ceramic tube to enhance thermal conductivity and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single hoop connection is used between ceramic and metal tubes, then the device complexity is reduced, but the reliability of the connection deteriorates due to differing thermal expansion coefficients causing separation and sealing failure
Solution Approach 1:
The connection device is divided into multiple hoops (first hoop, second hoop, and optionally third hoop) with different expansion coefficients, each serving a specific function. The first hoop provides initial mechanical support, the second hoop maintains sealing under thermal expansion, and the third hoop (if present) provides additional constraint. This segmentation allows each component to address specific aspects of the connection reliability problem without requiring a single complex mechanism.
Solution Approach 2:
The invention changes the parameter of expansion coefficient by selecting materials for different hoops with progressively lower expansion coefficients. The first hoop has an expansion coefficient between 10-15×10^-6/K, the second hoop between 5-10×10^-6/K, and the third hoop between 0-5×10^-6/K. This parameter variation allows each hoop to respond differently to thermal changes, maintaining connection reliability across the temperature range while managing the complexity through standardized material selection.
2Ease of operation
If functional clearance is provided in the connection device, then ease of assembly is improved, but hydrocarbon leaks occur during startup and mechanical reliability at room temperature deteriorates
Solution Approach 1:
The hoops are pre-assembled in a specific sequence during manufacturing, with the first hoop fitted to the ceramic tube, followed by the second hoop, and optionally the third hoop. This preliminary assembly ensures proper positioning and initial sealing before the device enters service. The sequential fitting allows for controlled clearance management where minimal clearance is maintained for assembly ease, while the multi-hoop structure compensates for any gaps to prevent leaks.
3Strength
If a rigid connection is used between ceramic and metal tubes, then mechanical strength is improved, but the ability to withstand thermal cycles deteriorates due to stress from differential expansion
Solution Approach 1:
The connection device uses a composite structure with multiple hoops made of different materials, each selected for its expansion coefficient characteristics. The first hoop may be made of a material with expansion coefficient 10-15×10^-6/K, the second hoop with 5-10×10^-6/K, and the third hoop with 0-5×10^-6/K. This composite approach allows the connection to maintain mechanical strength while accommodating differential thermal expansion through the coordinated response of different materials, preventing stress concentration and maintaining stability during thermal cycles.
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
This solution provides a reliable mechanical connection and sealing between ceramic and metal tubes over a wide temperature range, increasing productivity by maintaining a stable and efficient heat transfer, reducing coke formation, and extending the lifespan of the connection.
Implementation Method 1
the second hoop having an expansion coefficient lower than the expansion coefficient of the first hoop, at least between 20°C and 1000°C. When the temperature rises, the second hoop expands less than the first hoop. It thus exerts on the latter a compressive force avoiding its separation from the first part or a loss of sealing
Data Source
Figure 1~3
Figure 2~6
Figure 7
AI summary
The invention relates to a device comprising a first part (22) banded by means of a first band (42), the first band being banded in turn by means of a second band (44) with a thermal expansion coefficient lower than that of the first band.