Resumen de Intermixing Twin Ferrule Tube Fittings - Is it Safe?
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 FEA 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 overstressed. 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 faliure.
