Waterhammer caused by intermittent and simultaneously pump failure in pipe systems including series pump groups

In the large scale pipe systems the use of pump group connected in series is evitable to meet the desired pressure head. If one or more of the pumps shuts down، water hammer event occurs which manifests in pressure and rare faction wave، along the pipeline these waves result in huge stresses on the system. In this regard، this paper aims at investigating the pump stations performance during steady and transient flows، in which the focus is placed on various possibility of pump failure in a system of pumps in series. The mathematical model to carry out this research includes continuity and momentum equations (transformed to two characteristic equations) as well as equations to govern mechanical behavior of pump stations. These governing relations are numerically solved and programmed in a MATLAB code. The results reveal that the use of the same pumps leads to larger efficiency compound to using different pumps. Furthermore، if the pumps shut down one after other، the water hammer pressures remarkably alleviate. The result for this sequential pump station failure are quantitatively presented and discussed.