RISK-BASED APPROACH TO EVALUATE THE RELIABILITY OF A CITY SEWER NETWORK

Abstract

Introduction. The authors pay attention to the fact that there exist such technical objects, the reliability evaluation of which — if performed with the use of measures of the “classical” reliability theory (in particular, reliability function and/ or mean operating time to failure) — is ambiguous and poorly interpreted physically. A city sewer network can serve as an example of such an object. The authors consider a situation when the result of the formal sewer network reliability analysis comes into conflict with the physical interpretation of object operation. This generates a need for searching for a more informative reliability indicator peculiar to a city sewer network. Methods. The research is based on the sewer network decomposition-equivalenting method (DEM) developed previously. This method, in turn, is based on the probability theory, reliability theory and mathematical statistics. A database containing the information about all network elements’ failures and restorations over a preceding period, is used as reference material. Results. Operational risk is taken as the reliability measure of a city sewer network. It is defined as the relative volume of sewage, not delivered to treatment facilities of the network due to failures of its elements, in a certain time. A procedure for the quantitative calculation of this measure is developed. Its comprehensiveness and informative richness are demonstrated. The article shapes possible ways of using the “operational risk” indicator when developing a city sewer network renovation strategy. Conclusion. Operational risk as the reliability measure can be used in practice to improve the performance of a city sewer network.