Flareless Fitting Torque Assembly and Work-Hardened Ferrule
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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 torque-based assembly, as they require hardened materials and complex manufacturing processes.
Innovation Solution
A flareless fitting design featuring a male nut made of work-hardened stainless steel and an annealed female body, with case-hardened ferrules and a cartridge nut assembly that allows pull-up by torque, enabling higher pressure ratings without compromising leakage or vibration resistance and reducing manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ferrule type fittings are used to achieve high reliability and leakage resistance, then sealing performance is improved, but assembly complexity increases due to the need for precise turn-based tightening
Solution Approach 1:
The patent replaces the traditional mechanical turn-based tightening system with a torque-based tightening system. The fitting incorporates a torque indicator mechanism that provides visual feedback when the specified torque is reached, eliminating the need for operators to count turns and reducing assembly complexity while maintaining reliable sealing performance.
Solution Approach 2:
The fitting includes built-in torque indicators and guide features that automatically guide the assembly process. The torque indicator provides self-service by visually indicating when proper tightness is achieved, eliminating the need for external measurement tools or complex procedural knowledge during assembly.
2Stress or pressure
If work hardened materials are used for high pressure ratings, then pressure resistance is improved, but manufacturing cost increases due to material removal requirements
Solution Approach 1:
The patent applies work hardening locally only to the ferrule and specific critical areas of the fitting body that require high strength for gripping the conduit and withstanding pressure. The body can be manufactured from more economical materials or processes for non-critical areas, reducing overall manufacturing cost while maintaining high pressure rating capability where needed.
Solution Approach 2:
The fitting employs a composite construction combining work hardened ferrule material with body materials optimized for their specific functions. This allows the ferrule to provide the necessary grip strength while the body can be manufactured more economically, potentially using casting or forming processes rather than extensive machining of hardened material.
3Reliability
If multiple ferrules are used to ensure grip and seal, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple ferrule functions into a single integrated ferrule component. This unified ferrule incorporates both the gripping surface and sealing surface, eliminating the need for separate grip ferrules and seal ferrules. The single ferrule is designed with appropriate geometries to perform both functions simultaneously, reducing assembly complexity while maintaining reliable grip and seal performance.
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 higher pressure ratings exceeding 12 ksi with improved assembly efficiency and cost-effectiveness, ensuring reliable fluid tight seals and resistance to vibration fatigue, while allowing for easier assembly using torque rather than turns.
Implementation Method 1
a male fitting component, such as a nut, includes a structure, which constrains a tube gripping device, such as a ferrule or ferrules
Implementation Method 2
The ferrules are case hardened, for example by a low temperature carburization process to provide very hard ferrules
Implementation Method 3
The ferrule or ferrules must establish a fluid tight seal, particularly under pressure, as well as adequate grip of the conduit
Implementation Method 4
The assembly is first tightened to a finger tight condition and then a prescribed number of turns, such as one and a quarter or one and a half turns, are used to pull-up the fitting to its final assembled condition
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.