"Data that Swagelok collects from field surveys show that intermixing and interchanging has terrible results—leak rates are through the roof (19%) on the fittings field tested, for example."
- Jason Burns, Swagelok Northern California
It is dangerous to mix materials or fitting components from various manufacturers—including but not limited to tubing, ferrules, nuts, and fitting bodies.
Leak-tight seals that will withstand high pressure, vibration, vacuum, and temperature changes depend on close tolerances and consistent, exacting quality control in conjunction with good design principles. The critical interaction of precision parts is essential for reliability and safety. A video below illustrates this.
Components of other manufacturers may look like Swagelok tube fitting components, but they cannot be manufactured in accordance with Swagelok engineering standards, nor do they benefit from innovations in design and manufacture defined by 36 active Swagelok tube fitting patents issued since 1989.
Musa Mihseiin and Mike D. Seymour published in the Journal of Engineering Design, Vol.10, No.4. the findings of independent research examining "the effects of intermixing the component parts of twin ferrule tube fittings manufactured by four different companies." It concludes that intermix/interchange can lead to system issues, leakage, and safety concerns.
Here is the paper's summary (bolding added):
"This paper presents the findings of an independent study carried out to examine the effects of intermixing the component parts of twin ferrule tube fittings manufactured by four different companies. Experimental tests and finite element analysis has shown that the swaging and sealing mechanisms of fittings are different despite seeing geometric similarities. It was evident that no two companies produced components to the same dimensional or metallurgical specification and that pressure testing alone should not be used as the only means of validation.
"The ERA plots of intermixed fittings show that a form of sealing occurred in some combinations which could lead to acceptance. However,it was not until further engineering assessment was made could it be seen that the sealing methods were not as originally designed and therefore a high risk factor must be applied. In addition to the design safety factors being compromised any intended sealing mechanism either became superfluous or over-stressed. Other components were stressed to levels in some unintended way and often were found to impede the movement of other parts and acting as a conduit or fatigue failure."
Here are the authors' conclusions:
Years ago, Swagelok tube fittings were put through a severe thermal shock test at an oil refinery facility in Ohio. The classic film is still great at illustrating the temperatures pressures and stresses our tube fitting connections withstand with absolutely no leakage.
We can take some of the sting out of replacement component searches by identifying product alternatives and highlighting any savings such as reduced purchase cost, maintenance, and downtime. To talk with our engineering team or ask a technical question, start here:
More like this: