Zero-Dead-Volume Capillary Fitting with Primary Seal Mediation
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Solution Overview
Problem
Existing zero dead volume fittings in analytical systems face issues with overdriving tubing due to ferrule deformation, leading to potential tubing fracture and the creation of undesirable mixing chambers under high pressures, exacerbated in multi-ported valves with multiple fitting bodies.
Innovation Solution
A high-pressure capillary tubing connector system featuring a main body, a primary seal made from inert materials like PEEK or PTFE, and a retaining member with a hex or knurled head, which limits ferrule compression and prevents overdriving of tubing by using a primary seal that seats flat against the fitting detail, ensuring a leak-tight seal without extraneous volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ferrule is deformed against the fitting to provide a seal, then a leak-tight seal is achieved, but the force may exceed the tubing strength and overdrive the tubing into the fitting
Solution Approach 1:
The patent introduces a primary seal as an intermediary element between the ferrule and the fitting. This primary seal (made of softer material like PTFE or PEEK) receives the compressive force from the ferrule and transmits it to the fitting surface, rather than allowing the ferrule to directly compress the tubing. This mediator protects the tubing from excessive force while still achieving a leak-tight seal through the primary seal's deformation against the fitting's seal surface.
2Reliability
If the ferrule is deformed to create a seal, then sealing is achieved, but dead volume is created at the interface of components
Solution Approach 1:
The patent extracts the sealing function from the traditional ferrule-tubing interface and relocates it to a dedicated primary seal component that interfaces with the fitting. By separating the sealing action from the tubing connection, the design eliminates the dead volume that would otherwise be created at the ferrule-tubing-fitting interface. The primary seal is designed to contact the fitting's seal surface directly, creating the seal away from the tubing path to minimize dead volume.
3Reliability
If high compression force is applied to the ferrule, then seal reliability is improved, but turbulence and mixing are induced in the flow path
Solution Approach 1:
The primary seal acts as a mediator that absorbs the compression force needed for sealing without transmitting it to the tubing or fitting structures that could induce turbulence. The soft, compliant material of the primary seal deforms to create the seal while maintaining a smooth flow path, preventing the generation of turbulence or mixing chambers that would occur with rigid ferrule deformation against the tubing.
4Stress or pressure
If the fitting is designed to sustain high pressures, then pressure resistance is improved, but the risk of overdriving tubing and creating mixing chambers increases
Solution Approach 1:
The primary seal serves as a pressure-distributing intermediary that allows the fitting to sustain high pressures without directly transmitting excessive localized forces to the tubing. The primary seal deforms under pressure to maintain the seal integrity while protecting the tubing from overdriving, thus preventing mixing chamber formation even under high pressure conditions.
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 system effectively prevents tubing overdriving and fracture while maintaining a leak-tight seal, reducing dead volume and turbulence, thus enhancing the efficiency and reliability of analytical systems under high pressures.
Implementation Method 1
the nut is threadedly engaged so as to be retained in place and to deform the ferrule against the mating wall of the fitting detail, causing the ferrule to apply pressure to the tubing and force such tubing against the bottom of the fitting detail
Implementation Method 2
the ferrule is then slid along the tubing until it engages the mating walls of the fitting, and the nut is threadedly engaged so as to be retained in place and to deform the ferrule against the mating wall of the fitting detail
Data Source
Figure 1
Figure 2~3
AI summary
The present disclosure provides a high pressure capillary tubing connector system for use with a zero dead volume fitting which includes a main body, a primary seal, inert tubing, a ferrule, and a retaining member, where the zero dead volume fitting has a zero dead volume fitting detail having a zero dead volume fitting detail pilot which terminates at a zero dead volume detail pilot bottom and which has a zero dead volume fitting detail pilot length and having a zero dead volume fitting detail ferrule seat.