Reliability Allocation: an iterative approach for complex systems

Reliability Allocation is a top-down technique implemented to assign a reliability target to all the components making up the system based on a system reliability goal. It is therefore fundamental to perform an accurate and effective reliability allocation during the early phase of the system's design. Despite several reliability allocation techniques are available in literature, every existing method is based on the assumption of a series reliability configuration of the system under analysis. However, redundancy plays a fundamental role in many different fields of application where it is absolutely required to ensure continuity of service in case of failure of a critical component. Therefore, this simplifying hypothesis is too simplistic for many industrial systems characterized by the presence of several redundancies and fault tolerant architectures. Starting from a previous work, this paper presents an iterative allocation procedure based on the hierarchical decomposition of the studied system. The proposed approach allows to successfully overcome the assumption of a series architecture without changing the main core of the allocation procedure. A lube oil console for Oil&Gas applications has been taken as case study to test and validate the performances of the iterative approach.