Investigation of Pump Failure-Induced Waterhammer Waves: A Case Study

Abstract

The present study analyzes the effect of the pipe material type on the transient flow behavior in a pumping system due to an accidental pump shutdown. The material types addressed in this study include steel and High- or Low-Density PolyEthylene (HDPE) or (LDPE); involving elastic and plastic rheological pipe-wall behavior. The numerical solution is developed basing on the Method Of Characteristics used for the discretization of the Extended One-Dimensional pressurized-pipe flow model, incorporating the Kelvin-Voigt and Vitkovsky rules. Experimental data from the literature were used to validate the numerical solver. The proposed numerical algorithm is then used to investigate the transient pressure-wave behavior induced by the power failure to a pumping station composed of an inline connection using different pipe material types. The findings show the severity of such a scenario, in terms of the magnitudes of induced up-surge and down-surge pressure-waves. Furthermore, this research demonstrates that plastic pipe-wall materials allow for substantial attenuation of surge magnitude in conjunction with the expansion of the period of pressure-wave oscillations. The observed attenuation and expansion effects are also found to be highly dependent on the plastic material type. In this respect, the findings indicate that the (LDPE-Steel) piping system's specific layout allows for the best tradeoff between the two last effects.

Flow Deflection between Guide Vanes in a Pump Turbine Operating in Pump Mode with a Slight Opening

“…The unstable phenomena that occur in an RPT under runaway conditions (S-shaped characteristic in the turbine) are associated with fluctuations in the head and discharge of the system. This unstable behavior has been addressed by some authors [2][3][4][5][6][7] who believed that the nature of the vortex structures can be the mechanism that leads to potentially unstable characteristics.…”

“…Unstable phenomena such as rotating stall always come with the vibration of the units [5][6][7], which is harmful to the stability of the turbine and other devices. In addition, especially during the startup or shutdown process, the resonance of the units also frequently occurs, which is usually caused by rotor-stator interference (RSI) [15], self-excitation [16], or pressure pulsation [17].…”