The fault tree in eXpress has a fully customizable set of options to design how the fault tree appears in standard configurations.
The “Fault Tree Appearance Options” dialog allows the user to fully customize the fault tree event appearance setup different looks for the fault tree which include:
1. Control details, appearance, sizing and placement of the event in the fault tree.
2. Specify automatic simplification details by removing or retaining repeated events, logically redundant events and fully-prognosed failures.
3. Specify the level of automatic optimization when the tree is display in the optimized mode.
4. Specify automatic grouping and paging details to simplify the display of the tree to improve readability.
Fault Tree Appearance Options Dialog
When displayed in multipage mode. Transfer events simplify the diagram by placing common or complex event structures on separate pages of the FTA with a Yellow triangle pointing to the page number of the transferred events.
Faults may be inserted into the FTA by selecting the root failures and changing the status from “Unknown” to either “Failed” or “Not Failed”. When the event status has been changed then all of the dependent events of the selected root failure will be highlighted in red or green depending on whether “Failed” or “Not Failed” was selected. The likelihood of the dependent events will then be recalculated based upon the assumption that the given root failure is proven “Not Failed” or indicted as “Failed”.
One of the unique features of the eXpress FTA is that it provides three different ways of viewing a given fault tree: “As Modeled”, “Simplified” and “Optimized”.
In eXpress, fault trees are displayed using the same graphic interface that is used to display eXpress FMECA charts. One benefit of this tight integration is that each fault tree also serves as an index to information in the corresponding FMECA. This is particularly powerful when your FMECA has custom columns containing project-specific data. Many companies treat their FMECAs as data repositories for multiple design and analysis disciplines. With the eXpress FTA module, this information remains at your fingertips as you evaluate the system-level impact of failures using fault trees.
During fault tree editing, FMECA rows that are related to the selected fault tree can be optionally displayed (instead of the fault tree diagram) on the right-hand side of the screen. When one or more entries are selected in the Explorer Tree on the left – which the fault tree events, then the chart will be further filtered to list only FMECA rows related to the selected entries.
During fault tree editing, FMECA rows that are related to the selected fault tree can be optionally displayed (instead of the fault tree diagram) on the right-hand side of the screen. When one or more entries are selected in the Explorer Tree on the left – which contains the Minimal Cut Sets, then the chart will be further filtered to list only FMECA rows related to the selected entries.
The display of the tree can be transitioned between a quantitative view which displays the likelihood of occurrence of the critical event and the qualitative tree which displays only the relationships between dependent events.
Fault Insertion showing qualitative vs quantitative views