ITEM TOOLKIT

Chapter 8 Fault Tree 187
• Dormant Event
A Dormant event indicates a system event with unrevealed failures until maintenance, or inspection.
• Conditional Event
A Conditional event is similar to a basic event but represents a conditional probability connected to an inhibit gate.
How to Create and Add a Failure Model into an Event
Failure Models contain failure and repair information for a component, or probability of occurrence data for human errors,
environmental conditions etc. A failure model is assigned to an event or events, for use in the Quantitative Analysis of the
fault tree diagram.
1. Right Click on the first Event.
2. Select Event Parameters.
3. The Event Parameters Window opens.
B
C
D
A
E
4. Input the Description of the Event “Switch 1 is open” into the general window (A).
5. Input the Name “Switch 1”(B), select the Type “Rate” (C) and input the Failure Rate “1.5e-006” (D) of the Failure
Model into the Failure Model window.
6. Available model types include: Fixed, Rate, MTTF, Dormant, Standby, Weibull, LogNormal, Normal, Gamma, Beta,
BiNomial, ChiSquared, Poisson, Uniform and LogUniform.
7. When completed, click OK (E).
8. Repeat 1 to 6 for the second Event with “Switch 1 is open” as Description, “Switch 2” as Name, “2e-006” as Failure
Rate and select “Rate” for the Type.
9. Repeat 1 to 6 for the third Event with “No current to point A” as Description, “No Current” as Name, “3e-006” as
Failure Rate and select “Rate” for the Type.