No one sets out to buy a tube fitting that will leak, but how can it be told in advance if it will once it is incorporated into a fluid system? There are three design factors that determine the effectiveness of a fitting, assuming it has been installed correctly:
1. Tube Grip
2. Gas Seal
3. Vibration Protection
Here is Swagelok's short, three minute long video that covers these big three factors. If you'd rather read the highlights, see below.
The way that a tube fitting grabs hold of the tubing plays a major role in the leak resistance of the fitting and the structural integrity of the tubing. The standard bite-type ferrule design (with either single or double ferrules) has a single point of connection holding the fitting in place. In Swagelok's design, the patented hinging and colleting action of the rear ferrule means that more material from the fitting in contact with the tubing, thus providing more direct axial support. (See the yellow area indicated in the illustration to the right.)
2. Gas Seal
While the rear ferrule is primarily responsible for holding the fitting in place, Swagelok's front ferrule has a burnishing or polishing action that occurs between it and both the tubing and the fitting body. What this does is create zones of contact (See the yellow areas in the illustration) which prevent leakage.
3. Vibration Resistance
In the bite-type design, having the single point in contact with the tubing causes stress risers, as seen in the illustration below.
By having an entire colleting region, the Swagelok design is able to not only protect the stress risers, but is also able to ensure that any that fractures that might occur are not occurring in the compromised area.
If you doubt the superior performance and unfailing reliability of the Swagelok tube fitting, we encourage you to visit with one of our engineers to better understand the design, metallurgy and testing that supports this. Not only is the Swagelok tube fitting the only one approved directly by the U.S. Navy, but we can share extensive performance testing data and Finite Element Analysis data to support this.