Hydraulic reliability index for sewage pumping stations

In this paper, we propose a hydraulic reliability index for sewage pumping stations (SPS). This hydraulic reliability index is a measure of the ability of an SPS to fulfill its function in the future in conditions where its pump units (PUs) will be put out of operation occasionally. The reliability index is defined as the ratio of the expected volume of sewage that will not be pumped by SPS, due to possible PU failures, to the expected volume of sewage that will enter the pumping station inlet over the same prediction time. The calculation of the expected volume of unpumped sewage is based on the assumption that the processes leading to PU failures are stochastic and mutually independent. The simple example is used to demonstrate the proposed methodology.