Importing CAFTA Fault Trees

Windchill Risk and Reliability Desktop Help > Windchill FTA > Fault Tree Interface > Fault Tree How-Tos > Importing CAFTA Fault Trees

If you are a member of the CAFTA consortium, you can import CAFTA fault trees from version 5.0 or later into the FTA module. Because CAFTA uses Lambda Tau calculations, you cannot import CAFTA trees into an existing System file with time dependent trees. However, you can import them into a new System file, which automatically sets the FTA calculation type to Lambda Tau in its file properties. Additionally, you can import CAFTA trees into an existing System file with other Lambda Tau trees. For more information, see Performing Lambda Tau Analysis.

1. Because the FTA module cannot read the CAF files in which CAFTA stores tree structures, in CAFTA, you must first output the tree structure you want to import into a format that the FTA module can read:

a. Start CAFTA and open the CAF file for the tree you want to import.

b. Select File > Reports. The Fault Tree Reports window opens.

c. Under Report Type, select either Gate List (Alphabetical) or Gate List (Depth First).

d. Click Print to File. A window opens for specifying the file name, type, and location.

e. Use the options provided to save the report as a TXT file, supplying a location on your computer to which you can easily navigate.

2. In a new System file, or in a System file with Lambda Tau trees, select an FTA pane.

3. Select Tools > Import from CAFTA. The Import CAFTA window opens.

4. For CAFTA Gate and Event Library (.RR) file, use the browse button to select the RR file for the CAFTA tree to import.

The RR file contains gate and event data. This file, which is not modified during the import, can be shared with multiple CAFTA trees. It does not contain any structure information.

5. For Gate List Report (.TXT) file, use the browse button to select the TXT file that you generated in step 1.

6. Click OK. The Importing CAFTA window opens, displaying progress as the CAFTA tree is imported.

This status information window also shows any important messages related to the import so that you can save or print them before closing the window. For more information, see Status Information Windows.

7. When finished, click Close.

If the CAFTA tree is imported successfully, it is inserted at the end of the FTA Table. If this tree is collapsed, in Identifier for its top gate, click the + (plus) sign to the left of the gate symbol. To expand and collapse branches, you can either click the + (plus) and - (minus) signs or use the commands on the Tree menu. For more information, see Expanding and Collapsing Branches.

Basic data for events and gates is mapped from CAFTA to fields in the FTA module as follows:

CAFTA	FTA Module
Name	Identifier
Description	Description
Source	Remarks
Notes	User Memo 1

Calculation input data is mapped from CAFTA to the FTA module as follows:

CAFTA	FTA Module	Additional Information
0 - Probability	Constant Probability	Value
1 - Multiply	Lambda Tau	---
2 - Periodic Test	Average Unavailability (approx)	---
3 - Mission time, no repair	Probability of Failure	---
4 - Repairable	Asymptotic Unavailability	---
5 - Periodic test	Average Unavailability	---
6 - Repair & Mission Time	Constant Probability	Calculated value to match CAFTA results for the event probability, warning written to Importing CAFTA window
9 - Initiator	Constant Probability	Value with no units adjustment, warning written to Importing CAFTA window
+ - TRUE	Constant Probability	---
- - FALSE	Constant Probability	---
= - Equation	Constant Probability	Evaluated equation, warning written to Importing CAFTA window

While most gate mapping from CAFTA to the FTA module is exact, a few special cases exist.

• Combination gates in CAFTA (such as COM3 and COM4) are converted to Voting gates, with the number (3 or 4) set as the number of votes.

• “A and not B,” “not A, or B,” “not A and B,” and “A, or not B” in CAFTA are converted to standard OR or AND gates, with NOT gates inserted between them and the appropriate input.

• Equivalence gates in CAFTA are converted to pass-through gates.

• Priority AND gates in CAFTA are converted to AND gates. When such a conversion occurs, a warning message is written to the Importing CAFTA window.

CAFTA supports many more types of events than the FTA module. Only basic events and undeveloped events map directly. All other CAFTA event types are converted to basic events. While a warning message is written to the Importing CAFTA window for these other event types to indicate this, you need not worry about them. These other events differ from basic events only in their visual styles. They are all calculated in the same manner.

Customized user data and CCF data from CAFTA is not imported.