Tube Fitting With Hardened Nut And Annealed Body
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Solution Overview
Problem
Current flareless fittings, particularly those used in high-pressure applications like hydrogen storage in alternative fuel vehicles, face challenges in maintaining leakage resistance and grip performance while being cost-effective and suitable for complex configurations, as they require hardened materials and complex manufacturing processes.
Innovation Solution
A fitting design that uses a male nut with a higher hardness ratio relative to the female body, allowing for higher pressure ratings without compromising leakage or grip, and incorporates case-hardened ferrules and selectively work-hardened components to achieve these goals, enabling easier assembly by torque rather than turns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hardened materials are used for high-pressure fittings, then pressure rating and reliability are improved, but manufacturing cost and device complexity increase
Solution Approach 1:
The fitting is divided into two separate components with different material properties: a softer annealed body and a harder nut. This segmentation allows each component to be optimized independently - the body for ease of manufacture and corrosion resistance, and the nut for high-pressure containment - resolving the contradiction between reliability and manufacturing cost
Solution Approach 2:
Different material hardness levels are applied to different parts of the fitting system. The nut is hardened to contain high pressure while the body remains annealed for easier manufacturing. This local differentiation of material properties allows the system to achieve high pressure rating without requiring the entire fitting to be made from expensive hardened material
2Reliability
If hardened materials are used for complex fitting configurations, then pressure rating is improved, but material removal and manufacturing cost increase
Solution Approach 1:
The fitting configuration is segmented into body and nut components that can be manufactured separately using optimal processes for each. The body can be formed by cheaper methods like stamping or drawing, while the nut is hardened separately, avoiding the need to machine complex hardened configurations
Solution Approach 2:
The material state is changed from hardened to annealed for the body portion, allowing easier forming and reduced material removal for complex configurations. The hardness parameter is then applied selectively to the nut component where it is most needed for pressure containment
3Reliability
If ferrule type fittings are used for high-pressure applications, then leakage resistance is improved, but assembly complexity and precision requirements increase
Solution Approach 1:
The interface between the nut and body is designed with homogeneous, conforming surfaces that naturally self-align during assembly. This reduces assembly complexity and precision requirements while maintaining the leakage resistance provided by the ferrule-type seal
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 design achieves high-pressure ratings exceeding current standards, reduces manufacturing costs, and simplifies assembly processes by using annealed bodies and work-hardened nuts, ensuring reliable fluid tight seals and resistance to vibration fatigue.
Implementation Method 1
incorporates case-hardened ferrules and selectively work-hardened components
Implementation Method 2
work-hardened nuts
Implementation Method 3
annealed bodies
Data Source
AI summary
A fitting for a tube or pipe capable of functioning a high pressures having a first fitting component adapted to receive the conduit end; a conduit gripping device such as a ferrule or ferrules and a second fitting component that can be joined to the first fitting component to cause the conduit gripping device to grip the conduit and seal when assembled. In one aspect of the invention, the first fitting component is constructed from a material that is softer than the material used to construct the second fitting component. An additional aspect of the invention include a retaining portion on the second fitting component that constrains the tube gripping device against pressure. The retaining portion can also be configured to retain the tube gripping device to the second fitting component prior to installation and in a finger-tight condition. A further aspect of the invention includes a first fitting component in which an exterior portion of the component is work hardened radially outward from the tube gripping device. The fitting may optionally be provided with a structure to effect the pull-up by torque functionality.