Process Isolation Diaphragm Weld Ring Offset Design
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Solution Overview
Problem
Existing process fluid pressure transmitters face challenges with non-metallic seals in high-pressure and high-temperature applications, where metal seals offer advantages but require specific surface finish requirements that cannot be met when welds for the isolation diaphragm are on the sealing surface, leading to potential fatigue issues and reduced sealing effectiveness.
Innovation Solution
A process isolation diaphragm assembly using a metal seal with a weld ring and diaphragm spacer configuration, where the weld is offset and aligned with the metal seal, eliminating torque and ensuring a consistent hinge point, and optionally incorporating a secondary support weld for increased rigidity and fatigue life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If welds for attaching the isolation diaphragm are located on the sealing surface, then the assembly structure is simplified, but the metal seal cannot meet surface finish requirements and sealing effectiveness is reduced
Solution Approach 1:
The sealing surface is segmented into two distinct zones: a first portion for receiving the metal seal with precise surface finish requirements, and a second portion for locating welds with relaxed surface requirements. This segmentation allows each zone to be optimized independently for its specific function, resolving the conflict between structural simplicity and sealing effectiveness.
2Ease of manufacture
If welds are located on the sealing surface, then manufacturing is easier, but torque is generated that causes fatigue issues in the assembly
Solution Approach 1:
The design employs asymmetric positioning where the welds are deliberately offset from the central seal seating area. The welds are located in a second portion of the sealing surface that is radially offset from the first portion receiving the seal. This asymmetric arrangement eliminates torque generation during pressurization while maintaining manufacturing ease.
3Adaptability or versatility
If a non-metallic seal is used, then the seal can tolerate surface variations from welds, but the seal cannot retain pressures above 6000 psi in high temperature applications
Solution Approach 1:
The invention changes the material parameter of the seal from non-metallic to metal, which fundamentally alters the pressure retention capability. Metal seals can withstand pressures above 6000 psi and high temperatures, whereas non-metallic seals cannot. The parameter change is compensated by implementing precise surface finish control in the seal receiving portion and offset weld positioning to eliminate torque.
Data Source
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AI summary
A process fluid pressure transmitter (10) includes a sensor body (14) having a pressure sensor (16) and electronics (18) coupled to the pressure sensor (16) to obtain an indication of pressure from the pressure sensor (16). At least one process fluid isolation assembly is fluidically coupled to the pressure sensor and is configured to receive a process fluid. The process fluid isolation assembly includes an isolation diaphragm (58) welded to a weld ring (70, 80). The weld ring (70, 80) has a sealing surface on a first side adapted for contact with a metal sealing ring (72) and a weld portion welded to the sensor body (14) on a second side. The sealing surface and the weld are substantially aligned with one another.