GoldSim records the unique state of the element each time that it fails. After the simulation has been completed, GoldSim can analyze these failure scenarios to allow you to determine key sources of unreliability for a particular component.
The Causal Analysis option in the Results tab of a reliability element allows you to view this type of analysis for the component.
Note: Causal
Analysis is not available if you have carried out your simulation using the
Distributed Processing Module.
Note: The Display button for Causal Analysis is grayed out
when the model is in Scenario Mode. That is, you cannot view these results
when running and comparing scenarios.
When you first click the Display button for Causal Analysis, a dialog will appear with the component’s unique states analyzed and sorted by Time in State:
The Summary section of the dialog displays a pie chart which shows the average percentage of the total simulation time spent in each of a number of primary states (Operating, Failed due to Internal Requirements, Failed due to External Requirements, Preventive Maintenance, Parent Not Operating and Component Turned Off). The Operating state can be excluded from the pie chart by clearing the “Plot ‘Operating’ State” checkbox (so that only non-operating states are shown in the pie chart).
Below the summary, the “State Analysis” section sorts each of the primary states by the time in each state (normalized to a single realization). For the External Requirements and Internal Requirements, the tree can be expanded (by clicking the plus sign next to the entry for those primary states) to explore each of the unique substates the component experienced:
Each of the substates for each primary state is again sorted by time in state. To allow you to quickly identify key sources of unreliability, for Failed Internal Requirements and Failed External Requirements primary states, the tree nodes for each individual substate are expanded in the section and color-coded: nodes that are true are highlighted in green and nodes that are false are highlighted in red.
Note: You can jump to the next false node in the tree by pressing
Ctrl+N, and you can jump to the previous false node by pressing
Ctrl+P. All branches of the state analysis tree can be
expanded by pressing Ctrl+A.
Alternatively, each of the primary states and their substates can also be sorted by Occurrence Count. When this radio button is selected, GoldSim tracks the number of times that the element entered each primary state, as well as the number of times that GoldSim entered each substate for the Failure Mode, Failed Internal Requirements and Failed External Requirements. The primary states, and their substates are then sorted using these values. Instead of displaying the time in each state (normalized to a single realization), each primary and substate displays the state frequency (count) normalized to a single realization.
GoldSim can also display the unique state information in a different manner, by root cause. If you select the Display Root Cause radio button, GoldSim displays the primary states in the same manner, but the substates are analyzed and GoldSim attempts to determine the identity of the lowest level components that resulted in failure of the system.
Note: The algorithm that is used to carry out the Root Cause analysis is
described in Appendix A.
These states are then sorted by cause (e.g., a failure mode, or the failure of a sub-component) most frequently responsible for failure of the component. Depending on whether Time in State or Occurrence Count is selected, for each state, GoldSim displays either the time or count.
Root causes can also be expanded to show the reason why reliability components identified as root causes were not operating or operable. These reasons can include conditions in the element’s internal or external requirements tree, failure modes of the component, or the fact that the component was turned off:
Note that if you have a large causal analysis tree with a number of hierarchical levels, it might be useful to view the tree in an expanded sub-window. You can do this by pressing the “pushpin” button in the Result tab just to the left of the tree. When you do so, GoldSim will display the tree in a separate (and resizable) window:
