While many smaller systems can be accurately represented by either a simple series or parallel configuration, there may be larger systems that involve both series and parallel configurations in the overall system. Such systems can be analyzed by calculating the reliabilities for the individual series and parallel sections and then combining them in the appropriate manner. Such a methodology is illustrated in the following example.
Consider a system with three components. Units 1 and 2 are connected in series and Unit 3 is connected in parallel with the first two, as shown in the next figure.
What is the reliability of the system if R1 = 99.5%, R2 = 98.7% and R3 = 97.3% at 100 hours?
First, the reliability of the series segment consisting of Units 1 and 2 is calculated:
The reliability of the overall system is then calculated by treating Units 1 and 2 as one unit with a reliability of 98.2065% connected in parallel with Unit 3. Therefore:
See Also:
RBDs and Analytical System Reliability
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