RELIABILITY ANALYSIS OF COMPLEX SYSTEMS BASED ON THE LOSSES FROM FAILURES

Abstract

The conventional reliability analysis is based on the premise that increasing the reliability of a system will decrease the losses from failures. In this paper it is demonstrated that increasing the reliability of the system does not always mean decreasing the losses from failures. An inappropriate increase of the reliability of the system may lead to a simultaneous increase of the losses from failure. In other words, a system reliability improvement, which is disconnected from the losses from failure does not necessarily reduce the losses from failures. An efficient discrete-event simulation model and algorithm have been proposed for reliability analysis based on the losses from failure for production systems with complex topology. The model links reliability with losses from failures. A new algorithm has also been developed for system reliability analysis related to productions systems based on multiple production units where the absence of critical failure means that at least m out n production units are working. The parametric study conducted on the basis of the developed models revealed that a dual-control production system is characterized by enhanced production availability, which increases with increasing the number of production units in the system. A production unit from a dual-control production system including multiple production units is characterized by a larger availability compared to a production unit from a dual-control production system including a single production unit. The proposed approach has been demonstrated by comparing the losses from failures and the net present values of two competing design topologies: one based on a single-channel control and the other based on a dual-channel control. The proposed models have been successfully applied and tested for reliability value analysis of productions systems in deepwater oil and gas production. It is also argued that the reliability allocation in a production system should be done to maximize the net profit/value obtained from the system. Consequently, a method for setting reliability requirements and reliability allocation maximizing the net profit by minimizing the sum of the capital costs and the expected losses from failures has been proposed. Reliability allocation which maximizes the net profit in case of a system consisting of blocks arranged in series is achieved by determining for each block individually, the reliabilities of the components which minimize the sum of the capital costs and the expected losses from failures.