Defining the Problem with Fault Tree Analysis

1 Defining the Problem with Fault Tree Analysis 

Notice that one event has units of per-demand and the others have a per-unit-time dimension. From elementary considerations, the top event can only have dimensions of per-demand (pure probability) or per-unit-time dimensions. Which dimensions they have depends on the application. If the fault tree provides a nodal probability in an event tree, it must have per-demand dimensions, if the fault tree stands alone, to give a system reliability, it must have per-unit-time dimensions. Per-unit-time dimensions can be converted to probability using the exponential model (Section 2.5.2.6). This is done by multiplying the failure rate and the mission time to give the argument of the exponential which if small may be 

2 Applying FTAPSUIT Chemical Process Tank Rupture 

To do this go to FTAPSUIT (refer to j Section 6.4.2. Go to the FTAPSUIT main 3 menu and select 1 to go to FTAPlus to input the data. The first selection is the title, the second is the file name (use pv for this 

Since dependency analysis is not needed, we can go on to the BUILD program. Go to FTAPSUIT and select 5 Run Build. It asks you for the input file name including extender. Type pv.pch, It asks you for name and extender of the input file for IMPORTANCE. Type, for examle, pv.ii . It next asks for the input option. Type 5 for ba.sic event failure probabilities. This means that any failure rates must be multiplied by their mission times as shown in Table 7.4-1. (FTAPlus was written only for option 5 which uses probabilities and error factors. Other options will require hand editing of the pvn.ii file. The switch 1 is for failure rate and repair time, switch 2 is failure rate, 0 repair time, switch 3 is proportional hazard rate and 0 repair time, and switch 4 is mean time to failure and repair time.) 

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