Experimental and dynamic system simulation and optimization of a centrifugal pump-coupling-engine system. Part 1: Failure identification

The failure mode of the six impellers of a centrifugal pump in an irrigation system used for street washing has been analyzed. The irrigation system is installed in more than 300 vehicles and consists of a pump, a tank, a regulator valve and the piping network. The was caused by a premature deterioration of the pump impellers in the water inlet section, which led to an increase in water loss, reduction of pump capacity and, finally, the breakdown of the pump. In order to ascertain whether the anomaly was metallurgically related, the original pump impellers were replaced with others of the same geometry but made of stainless steel; these new pumps also presented the same failure mode. The system was analyzed using a non-excited torsional lumped model, in which the stiffness of several degrees of freedom was evaluated with a finite element code, and an experimental analysis of the pumping system. The results show a very high level of torsional vibrations induced by severe pulsations of engine torque. These vibrations were mainly responsible for damage to the impellers.