CONICET | Buscador de Institutos y Recursos Humanos

Flexible hoses are sometimes placed at compressor discharge to minimize the effect of vibrations on piping and vessels. Doing well for this purpose, these elements can suffer themselves dynamic loads from gas pulsation and fail. The root cause of the failure of a flexible connection at the discharge of an oil distillery propane alternative compressor is investigated. The connection is a six inches stainless steel corrugated metal hose with an external braid. It was found that the flexible connection was under a working pressure higher than the maximum allowable pressure defined by the manufacture. The failed flexible is different from those previously used; thinner wires and lower angle of the braid. These result in a lower resistance to axial load, and in different dynamic characteristics. The flexible worked in its position supported by the end fittings. Due to dimensional conditions, once set in working position the braid was free of global traction stresses. This produced a gap between the corrugated and the braid allowing relative displacements. The failure took place by overload of the braid, after a noticeable local reduction of section of the wires, caused by wear. In the final steps of the failure the corrugated produced a squirm outside the braid towards the external side of the curve, producing the stretching of the corrugated hose. The final breakage of the corrugated took place by traction, its instability increased by the breakage of the wires. The fractures in the wires were consequence of fatigue crack propagation in previously worn areas; Recommendations are made to establish procedures to verify dimensions previous to assembly and to increase the inspection frequency of these elements, as well as to verify vibration levels of the connected machines. Elastomer material placed between corrugated and braid would diminish the rate of wear caused by vibrations.