Dual Ferrule Compression Fitting Geometry for Thicker Tubing
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Solution Overview
Problem
Ferruled-type compression fittings face limitations in handling increased tubing wall thickness and newer, stronger materials, leading to inconsistent performance and unforeseen failure modes such as premature tube slippage and ferrule 'bite' issues.
Innovation Solution
A novel geometry for dual ferrule compression fittings with specific ratios between ferrule lengths, seal depth, and diametrical surfaces, allowing for increased maximum allowable operating pressures and improved sealing, regardless of tubing material or thickness, by utilizing a curved ferrule design and optimized ferrule engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional ferruled-type compression fittings are used with increased tubing wall thickness, then the fitting can accommodate thicker walls, but the fitting becomes incapable of maintaining a grip on the tubing due to lack of deformation
Solution Approach 1:
The single ferrule is divided into two separate ferrules (first ferrule and second ferrule), each performing a specific function. The first ferrule provides initial engagement and deformation, while the second ferrule provides enhanced gripping force and sealing, allowing the fitting to handle thicker walls effectively
Solution Approach 2:
Each ferrule is designed with specific geometric characteristics optimized for its function. The first ferrule has geometry optimized for initial deformation, while the second ferrule has geometry optimized for gripping and sealing, allowing each component to excel at its specific task rather than requiring a single ferrule to perform all functions
2Strength
If newer and stronger tube materials are introduced into conventional ferruled-type compression fittings, then the system can handle stronger materials, but inconsistent fitting performance and unforeseen failure modes occur
Solution Approach 1:
The invention specifies precise geometric parameters and ratios for the dual ferrule design (such as ferrule length ratios, diametrical surface dimensions, and engagement geometries) that ensure consistent performance across different tube materials and thicknesses, preventing premature failure modes
Solution Approach 2:
By dividing the gripping function into two separate ferrules with optimized geometries, the system can better adapt to and accommodate variations in tube material properties, ensuring reliable performance whether working with softer or harder materials
3Adaptability or versatility
If the ferrule geometry is optimized for thicker walls, then the fitting can handle increased wall thickness, but the fitting design becomes limited to specific wall thickness ranges
Solution Approach 1:
The dual ferrule design creates a universal fitting that can accommodate a broad range of wall thicknesses and tube sizes. The first ferrule handles initial engagement across various wall thicknesses, while the second ferrule provides consistent gripping force, making the fitting adaptable to different applications without requiring multiple specialized designs
Data Source
AI summary
A fitting assembly having a longitudinal axis including a fitting body having a seat, a threaded drive nut, a tube, a first (rear) ferrule and a second (front) ferrule receivable over the tube, the first (rear) ferrule having a first driven end and a first driving end and defining a first (rear) ferrule length (FFL) therebetween, the second (front) ferrule having a second driven end and a second driving end and defining a second (front) ferrule length (SFL) therebetween, and a seal depth (SD) of the tube defined by a distance between the seat of the fitting body and the second driving end. A surface of the second driven end of the second (front) ferrule is a diametrical surface having a diameter (DSF). At least one of the following apply:SFL/SD≥0.9;2.7≥SFL/DSF≥2.2; andSFL/FFL≥4.0.