Composite Weld Ring for Corrosion Resistant Isolator Assembly
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Solution Overview
Problem
The use of high-corrosion resistant materials like tantalum in process fluid pressure measurement devices poses manufacturing challenges due to metallurgical incompatibilities with other materials, leading to increased costs and longer lead times, as traditional welding methods are impractical and do not meet NACE requirements.
Innovation Solution
A composite weld ring formed from metallurgically incompatible materials, such as tantalum and stainless steel, using explosion welding and subsequent machining to create a dimensionally controlled and reproducible interface, allowing for standard manufacturing processes to be employed in high-corrosion resistance applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tantalum is used for the isolation diaphragm to achieve high corrosion resistance, then corrosion resistance is improved, but manufacturing difficulty increases due to metallurgical incompatibility with stainless steel housing
Solution Approach 1:
The weld ring is divided into two distinct segments: an inner portion made of tantalum (compatible with the isolation diaphragm) and an outer portion made of stainless steel (compatible with the housing). This segmentation allows each material to be optimized for its specific function while avoiding the need to weld metallurgically incompatible materials together.
Solution Approach 2:
The weld ring acts as an intermediary component between the tantalum isolation diaphragm and the stainless steel housing. It provides a transition interface that enables connection between the two metallurgically incompatible materials through separate, compatible welds: one between tantalum components and another between stainless steel components.
2Strength
If traditional welding methods are used to join tantalum to stainless steel, then connection is achieved, but the weld does not meet NACE requirements and creates metallurgical incompatibility
Solution Approach 1:
The connection path is segmented into two separate weld zones: an inner weld between tantalum materials (isolation diaphragm to weld ring inner portion) and an outer weld between stainless steel materials (weld ring outer portion to housing). This eliminates the need for a mixed-metal weld, ensuring NACE compliance while maintaining connection strength.
3Reliability
If high-corrosion resistant materials like tantalum are used, then corrosion resistance is improved, but product cost increases
Solution Approach 1:
High-corrosion resistant tantalum material is applied locally only where it is absolutely necessary (inner portion of the weld ring in contact with the isolation diaphragm and process fluid), while the outer portion uses less expensive stainless steel. This local application of expensive material minimizes cost while maintaining the required corrosion resistance at the critical interface.
4Ease of manufacture
If explosion welding is used to join dissimilar metals, then joining capability is improved, but control over weld geometry and dimensions becomes difficult
Solution Approach 1:
The weld ring is pre-formed with the tantalum inner portion and stainless steel outer portion joined together before the isolation diaphragm is installed. This preliminary formation of the composite structure allows for precise dimensional control of the interface features, ensuring proper fit and alignment with the isolation diaphragm while still utilizing explosion welding to join the dissimilar metals.
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 approach reduces production costs and lead times by enabling the use of standard manufacturing techniques, while maintaining high-corrosion resistance, and avoids the limitations of explosive welding by allowing for more complex geometries and precise dimensional control.
Implementation Method 1
A composite weld ring formed from metallurgically incompatible materials, such as tantalum and stainless steel, using explosion welding
Data Source
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AI summary
A process device (10) has a process seal (48, 52) for coupling to an industrial process. The process device (10) includes a process device body (14, 250) having an isolation cavity and an isolation passageway (32, 34) extending from the isolation cavity to a pressure sensor (16). The isolation cavity and isolation passageway (32, 34) filled with an isolation fluid. An isolation diaphragm (254) is positioned to isolate the isolation cavity from process fluid. The isolation diaphragm (254) has a process fluid side and an isolation fluid side. A weld ring (200) is positioned around a periphery of the process fluid side of the isolation diaphragm (254). The weld ring (200) is formed of a first material compatible with the isolation diaphragm and a second material compatible with the process device body (14, 250). A weld (258) secures the weld ring (200) to the process device body (14, 250).