Case-Hardened Ferrule Fitting for High-Pressure Tube Sealing
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Solution Overview
Problem
Current flareless fittings, particularly those using ferrules, face challenges in high-pressure applications such as hydrogen storage in vehicles, where existing materials and manufacturing processes are inadequate for pressures exceeding 10 ksi, and assembly methods like pull-up by turns are not suitable for torque-based assembly requirements.
Innovation Solution
A fitting design that incorporates a male nut with a higher hardness ratio relative to the fitting body, using case-hardened ferrules and an annealed body, allowing for higher pressure ratings without material hardening of the body, and a cartridge nut assembly for easier assembly and torque-based pull-up, reducing material costs and assembly complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the fitting body is made from hardened material to withstand high pressure, then the pressure rating is improved, but the manufacturing cost and material removal increase significantly
Solution Approach 1:
The patent applies local quality by making only the ferrule (not the entire fitting body) from hardened material. The ferrule is case-hardened to provide localized strength where it is most needed for high-pressure containment, while the fitting body remains annealed for ease of manufacturing complex shapes. This resolves the contradiction by achieving high pressure rating through selective hardening rather than hardening the entire component.
Solution Approach 2:
The patent uses composite materials by combining annealed fitting body material with case-hardened ferrule material. The annealed body provides ductility and ease of fabrication for complex geometries, while the case-hardened ferrule provides the necessary hardness and strength for high-pressure applications. This composite approach allows the fitting to achieve 15,000 psi pressure rating without requiring the entire body to be made from expensive hardened material.
2Reliability
If ferrule type fittings are used for high reliability connections, then the seal quality is improved, but the assembly complexity increases due to pull-up by turns requirement
Solution Approach 1:
The patent changes the assembly parameter from rotational turns to linear torque application. Instead of requiring a specific number of turns (pull-up by turns), the invention uses a torque wrench to apply a specified torque value directly to the nut. This simplifies the assembly process by providing a clear, measurable parameter (torque) that ensures proper sealing without requiring operators to count turns or estimate assembly progress.
Solution Approach 2:
The patent substitutes the mechanical turn-counting system with a torque-based mechanical system. The torque wrench provides direct feedback through mechanical means (clicking or digital display) when the correct torque is reached, replacing the indirect and less precise turn-counting method. This substitution maintains the reliability of ferrule fittings while significantly improving ease of operation.
3Volume of moving object
If the ferrule is made smaller for compact design, then the device size is reduced, but the risk of dropping or losing the ferrule increases
Solution Approach 1:
The patent merges the ferrule with the nut by forming the ferrule as an integral part of the nut structure. The ferrule is positioned within the nut and retained by the nut's internal geometry, eliminating the need for separate ferrule handling. This merging ensures that the ferrule cannot be dropped or lost during assembly, while still maintaining a compact overall fitting size. The ferrule-nut integration provides reliable retention through the natural geometry of the threaded component.
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 up to 15 ksi with improved assembly efficiency and reduced material costs, ensuring reliable fluid tight seals and grip under high pressures, and facilitates easier assembly using torque rather than turns.
Implementation Method 1
using case-hardened ferrules and an annealed body
Implementation Method 2
using case-hardened ferrules and an annealed body
Data Source
Figure 1
Figure 1A~1C
Figure 2~3
AI summary
A fitting for a conduit (T) has a first fitting component (112) adapted to receive the conduit end; a conduit gripping device such as a ferrule (132) or ferrules, and a second fitting (114) component that can be joined to the first fitting component (112) to cause the conduit gripping device (132) to grip the conduit (T) and seal when assembled. In one aspect of the invention, a portion of the second fitting (114) component at least partially retains the conduit gripping device (132). The retaining portion can also be configured to retain the conduit gripping device to the second fitting component prior to installation and in a finger-tight condition. In another aspect of the invention, a tool is provided to retain a fitting component (112) and a conduit gripping device prior to assembly of the fitting and conduit gripping device to a conduit end.