Mitigation effectiveness, examples modeling conditions

Table 2.1 shows examples of how the elements of an accident fit together. Reading the table from left to right, you can see how an accident evolves. First, there is a hazardous condition—such as large quantities of flammable liquids. Then the initiating event occurs—for example, a valve sticks open. The effect of a valve-failed-open propagates a pressure rise in the system. Now, an in-line relief valve can mitigate the effects of the initial event. If not, an accident ensues—explosion. Chapter 11 discusses and details the events that lead to an accident. It also discusses James Reason s famous Swiss cheese accident model. 

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