BlockSim provides a number of results at the overall system level and at the individual phase level when a simulation is run on phase diagrams. To illustrate these results, consider the probabilistic scenario of Figure 11.7 used to illustrate the Go to Maintenance Phase option. Assume that phase 2 has the option to Start New Simulation selected for the On System Failure property instead of the Go to Maintenance Phase option in the original example. The phase properties for the resulting phase diagram are shown next. Some of the results obtained from BlockSim after running the 1,000 simulations, using the settings shown in Figure 11.18, are shown in Figure 11.19.
Figure 11.18 Simulation settings in BlockSim.
Figure 11.19 Summary of phase diagram results for 1,000 simulations.
Phases Summary Results
Cycle: This column displays the cycle number of the phase for which the results are recorded. Depending on the duration of the phase, the simulation end time and other phase properties, a phase diagram may be partially or totally executed (cycled) more than once. The Cycle column denotes which cycle the results of a particular phase apply to.
Mean Duration: Mean duration is the average of the duration of a phase over all of the simulations in a particular cycle. It is calculated by dividing the total duration of a phase in a particular cycle by the number of executions. For example, row 3 displays the mean duration of phase 1 in the first cycle as 307.3127 hrs. This means that on the average, for the 1,000 simulations, the duration of phase 1 in the first cycle was 307.3127 hrs. A dash (-) is displayed in row 19 for the mean duration of phase 2 in the sixth cycle, indicating that BlockSim is unable to calculate the mean duration for this phase in the sixth cycle. This results from the fact that phase 2 never gets executed in the sixth cycle during any of the 1,000 simulations.
End of Phase Point Availability (EPPA): This is the availability at the end of the phase in a particular cycle. It is the ratio of the number of times the system was available at the end of the phase to the sum of the number of executions and the number of aborted executions of the phase. For example, phase 2 gets executed once in the fifth cycle and the system is available at the end of the phase during this execution. There are no aborted executions. Thus the End of Phase Point Availability for this phase is:
Reliability: This is the probability that the system has not failed during the execution of the phase for a particular cycle. It is calculated by dividing the number of times the system encounters its first failure during the phase by the sum of the number of executions and the number of aborted executions. The resulting ratio is the unreliability, and the reliability value is obtained by subtracting this ratio from 1. A reliability value of 0.3864 is calculated for the first cycle of phase 2. There are 108 executions of phase 2 in the first cycle where there is a system failure, and the total number of executions is 176. There are no aborted executions. Thus, the reliability is:
Throughput: The average throughput processed during a phase in a particular cycle is displayed in this column. It is the ratio of total throughput for the phase in the cycle to the number of executions of the phase.
Executions: This column gives the number of times a phase is reached for a particular cycle. It is the sum of the number of simulations for which the phase is executed.
Aborted Executions: Aborted Executions displays the number of times a phase is aborted because the simulation ends due to a preceding phase. This takes place when a system failure occurs in a phase having the Start New Simulation option selected for the On System Failure property.
RS ACI: ReliaSoft's Aborted Criticality Index (RS ACI) for a phase during a particular cycle is a relative index showing the percentage of times a simulation is terminated because of a system failure occurring in the phase. RS ACI applies only to those phases that have the Start New Simulation option selected for the On System Failure property. It is calculated by counting the number of times a phase in a particular cycle has a system failure that leads to termination of the simulation, and dividing this by the total number of times the simulation is terminated because of system failures in all the phases. For example, for phase 2 in the first cycle, RS ACI is 56.84%. This means that 56.84% of the times that the simulation was aborted, it was due to a system failure in the first cycle of phase 2.
Other Results
In addition to the Phases Summary Results, all other simulation results available at the system level are also available for each individual phase. Results for System, Blocks, Crews, Spare Pools and Reports are all available for each phase of the phase diagram.
See Also:
Reliability Phase Diagrams (RPDs)
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