Analytical Tube Fitting Assembly With Leak Chamber and Low Dead Volume
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Solution Overview
Problem
Double ferrule fitting assemblies in analytical systems face challenges with high torque requirements for assembly and disassembly, leading to tube deformation and increased dead volumes, which can cause chromatographic peak broadening and confuse with leaks, especially in applications with frequent tube changes and high pressure/vibration conditions.
Innovation Solution
A fitting assembly with a radial annular flange and a nut that forms a leak chamber for leak detection, reducing the need for excessive torque and minimizing dead volumes by using a sealing lip to secure the tube, allowing for easier assembly and disassembly while maintaining a robust seal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high torque is applied to tighten the nut for proper sealing, then sealing reliability is improved, but tube deformation increases and dead volume expands
Solution Approach 1:
The fitting body is segmented into distinct functional zones: a tapered sealing section with reduced diameter for creating the seal, and a larger diameter main body for structural support. This segmentation allows the sealing function to be performed in a dedicated zone with minimized volume, preventing excessive dead volume while maintaining reliable sealing through the tapered geometry that concentrates sealing force.
Solution Approach 2:
The fitting incorporates local quality variations through the tapered sealing section that has a smaller diameter compared to the main body. This localized geometric modification concentrates the sealing action in a specific region, allowing proper sealing to be achieved with reduced torque application, thereby minimizing tube deformation and dead volume expansion while maintaining sealing reliability.
2Reliability
If high torque is applied to tighten the nut for proper sealing, then sealing reliability is improved, but tube deformation increases
Solution Approach 1:
The fitting body is segmented into distinct functional zones: a tapered sealing section with reduced diameter for creating the seal, and a larger diameter main body for structural support. This segmentation allows the sealing function to be performed in a dedicated zone with minimized volume, preventing excessive dead volume while maintaining reliable sealing through the tapered geometry that concentrates sealing force.
Solution Approach 2:
The fitting incorporates local quality variations through the tapered sealing section that has a smaller diameter compared to the main body. This localized geometric modification concentrates the sealing action in a specific region, allowing proper sealing to be achieved with reduced torque application, thereby minimizing tube deformation and dead volume expansion while maintaining sealing reliability.
3Ease of operation
If tube is cut or withdrawn to reduce bulging, then ease of tube removal is improved, but dead volume increases
Solution Approach 1:
The fitting body is segmented into distinct functional zones: a tapered sealing section with reduced diameter for creating the seal, and a larger diameter main body for structural support. This segmentation allows the sealing function to be performed in a dedicated zone with minimized volume, preventing excessive dead volume while maintaining reliable sealing through the tapered geometry that concentrates sealing force.
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 reduces the torque required for sealing, minimizes dead volumes, and facilitates leak detection, enabling reliable and efficient operation in both analytical and industrial applications with reduced risk of over-tightening and real leaks.
Implementation Method 1
a sealing lip protruding towards the cavity, the sealing lip being coated with an inert substance and being for forming a seal with a radial surface of the tube
Implementation Method 2
A double ferrule 12, formed by a front ferrule 12a and a back ferrule 12b, pinches a tube 14 near its extremity, creating a bulge 13 frontward of the ferrule 12
Implementation Method 3
This swaging provides a good grip on the tube 14
Implementation Method 4
The amount of torque required increases every time the tube 14 is inserted and removed from the fitting 16
Implementation Method 5
In order to form a proper seal, a relatively high amount of torque is required in order to tighten the nut 17 so that the ferrules 12 deform the tube 14
Data Source
Figure 1~1A
Figure 2
Figure 3
AI summary
An improved fitting assembly for analytical devices is provided. The fitting assembly includes a tube securable to a fitting component via rear and front ferrules and a nut. The fitting component includes a body having a cavity for receiving the tube and ferrules. The body also includes a channel connecting the cavity to a leak chamber defined in a space between the tube, the fitting component and the inner sidewall of the nut body, the leak chamber being in fluid communication with the exterior of the nut body via the channel in the nut body. Sealing elements are provided between the tube and nut for encouraging leaks to flow through the leak path. A method for detecting leaks in the fitting assembly is also provided.