Dependency of technological lines in reliability analysis of heat production

Changes in external temperature throughout the year, related to the required thermal power in district heating cause large variability of thermal load during the year. The reliability analysis of heat production subsystem (SbHP) is performed under different operational conditions. Different thermal power supplies characterize particular operational states in which time-varying reliability structure is observed. Multi-state approach to the SbHP reliability analysis is proposed taking additionally into account the equal load sharing model of dependency among its technological lines. Variability of operating thermal load highly influences on the SbHP reliability characteristics. The SbHP mean conditional lifetimes in different operational states take values differing by 60%, 80% or even 90% of the value. Comparative analysis showed that the influence of dependencies among technological lines on the reliability of entire heat production subsystem is most significant in case of technological lines, linked in parallel. The expected lifetimes of SbHP with dependent lines in one of operational state compared to their values assuming independence among all lines are shorter by almost 40%. The presented approach allows for preventive and corrective maintenance in optimal time and for assessing the reliability and efficiency in various heat sources' configurations providing the optimal use of energy resources. (C) 2020 Elsevier Ltd. All rights reserved.