System Safety for the 21st Century, 2nd Edition

CHAPTER 16Fault Tree Analysis

Fault tree analysis is a very detailed analytical technique for determining the various ways in which a particular type of failure could occur. Fault tree analysis is based on the negative analytical trees discussed in Chapter 11 and uses the same event and gate symbols (Fig. 16‐1).

Rectangles are used as general event symbols, circles are used to show base events, and diamonds are used to show undeveloped terminal events. And gates are used to indicate that, in order to get an output, all inputs below that gate are required, and or gates are used to indicate that, in order to get an output, any one or any combination of the inputs is required.

There are two basic approaches to fault tree analysis. The qualitative approach is used to determine, using deductive logic, the ways in which the undesired top event could occur. The quantitative approach adds reliability or probability of failure data.

Fault tree analysis is one of the most meaningful system safety techniques available for systematically reducing the probability of an undesired event. It can also be one of the more expensive techniques because it requires a skilled and knowledgeable analyst and a considerable amount of time, especially if the project is complex and a quantitative approach is required.

The primary advantages of FTA are that it does produce meaningful data to evaluate and improve the overall reliability of the system and that it evaluates the effectiveness of and need for ...