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The System Overview worksheet for simulation diagrams presents an overview of the calculations performed for the entire system. The values shown are averages of the results of all of the simulations.
General Information
Mean Availability (All Events): Includes all system downing events during the time of the simulation. The standard deviation of this value is provided in the Std Deviation (Mean Availability) field.
Mean Availability (w/o PM, OC & Inspection): Includes all downing events, but not preventive, on condition or inspection tasks, during the time of the simulation.
Point Availability (All Events) at [Time]: The point availability of the system, including all downing events, at the simulation end time.
Reliability at [Time]: The reliability of the system at the simulation end time.
Uptime: The total amount of time that the system was up (i.e., operational) during the simulation.
Total Downtime: The total amount of time that the system was down (i.e., not operational) during the simulation.
Metrics
MTTFF: The mean time to first failure for the system.
MTBF (Total Time): The mean time between failures for the system, based on the total simulation time and including all system failures. This is calculated by dividing the simulation run time by the number of system failures.
MTBF (Uptime): The mean time between failures for the system, considering only the time that the system was up. This is calculated by dividing system uptime by the number of system failures.
MTBE (Total Time): The mean time between all downing events for the system, based on the total simulation time and including all system downing events. This is calculated by dividing the simulation run time by the number of downing events.
MTBE (Uptime): The mean time between all downing events for the system, considering only the time that the system was up. This is calculated by dividing system uptime by the number of downing events.
Note: To better understand the difference between total and uptime consider the case of a system that has two time reading displays. One display is based on the actual system run hours (like a Hobbs meter – or time-on meter) and the other is a real-time chronograph recording the true time elapsed. As the system goes up and down, the two will no longer be in sync. For example, imagine that the system had two failures and the real time display reads 1,000 hours elapsed time while the Hobbs meter reads 500 hours. The MTBF based on total time would be 1,000/2 = 500 hours, while the MTBF based on uptime would be 500/2 = 250 hours.
MTTM: The mean time to maintain for the system. This is calculated by dividing the total downtime by the number of downing events (i.e., the mean duration of downtime events for the system during the simulation.)
MTTR: The mean time to repair for the system. This is calculated by dividing the total downtime associated with corrective tasks by the number of failures.
Downtime Summary. For phase diagrams, when you are viewing overall results for all phases, the information in this section will be shown for all phases, for operational phases and for maintenance phases.
Waiting Downtime: The total amount of time that the system was down and no task existed that would restore it.
Critical Downtime: The total amount of time that the system was down where the length of the downtime met or exceeded the system downtime threshold, as specified on the Analysis Settings page of the diagram's control panel.
Event Count Summary displays information for all events associated with system downtime that occurred during the simulation. Note that events with zero duration will appear in this section only if the task properties specify that the task brings the system down or if the task properties specify that the task brings the item down and the item's failure brings the system down. For phase diagrams, when you are viewing overall results for all phases, the information in this section will be shown for all phases, for operational phases and for maintenance phases.
System Failures
Expected Number of Failures: The total number of failures expected to occur during the simulation for the system. The standard deviation of this value is provided in the Std Deviation (Number of Failures) field.
For each of the four classes of tasks (i.e., corrective, inspection, preventive and on condition), the following information is presented with regard to tasks performed during the simulation time:
Number of [Task Class]: The total number of tasks of this class performed on the system during the simulation.
[Task Class] Downtime: The total amount of time that the system was down (i.e., not operational) due to tasks of this class during the simulation.
State Change Triggers
Number of OFF Events by Trigger: The total number of events where the system is turned off by state change triggers. An OFF event is not a system failure but it may be included in system reliability calculations.
Total
Total Events: The total number of system downing events that occurred during the simulation time.
Cost Summary. For phase diagrams, when you are viewing overall results for all phases, the information in this section will be shown for all phases, for operational phases and for maintenance phases.
Opportunity Costs
Opportunity Cost (Total): Potential system revenue lost as a result of system downtime. This is based on the lost revenue per hour of uptime during system downtime plus the lost revenue per unit produced (if a throughput simulation has been run). Both Revenue per Hour of Uptime and Revenue per Unit Produced are specified on the Analysis Settings page of the diagram control panel.
Total Costs
System Total Cost: The total costs that accrued for the system during the simulation time, which is based the costs for tasks, crews and spare part pools along with the block consequential costs, as defined in each block's properties.
Revenue
Total Revenue: The total system revenue, including uptime revenue and throughput revenue (if a throughput simulation has been run), based on the System Level Revenue settings on the Analysis Settings page of the diagram control panel.
Throughput Analysis Summary: Throughput results will be calculated only if you selected to run a throughput simulation on the Analysis Settings page of the diagram control panel.
Throughput
Total Throughput: The total number of units that were processed/produced by the system during the simulation time.
Throughput Metrics
Maximum Capacity: The maximum number of units the system could have processed/produced during the total simulation time if no downtime was considered.
Actual Utilization: The ratio of actual units produced (Total Throughput) to the maximum that could have been produced (Max. Capacity), expressed as a percent (i.e., Total/Max).
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