Risk

The following articles provide information to do with the management of process facilities.

Event Tree Analysis

​This seven minute video describes the topic of Event Tree Analysis (ETA); It is an example of inductive analysis. The video uses the same logical and mathematical techniques as Fault Tree Analysis. However, whereas a fault tree analyzes how an undesirable top event may occur, an event tree considers the impact of the failure of a particular component or item in the system, and works out the effect such a failure will have on the overall system risk or reliability. Event trees use an inductive approach, whereas fault trees are deductive.

Fault Tree Analysis

Risk can be analyzed in one of two basic ways: inductively or deductively, that is either bottom-up or top-down. In a deductive analysis a system failure is postulated. The analyst then works backwards to deduce what combinations of events could have occurred for the system failure to have taken place (a detective solving a crime is thinking deductively). Fault tree analysis, the topic discussed in this section, is deductive. An inductive analysis works in the other direction. A single failure, such as a pump stopping or a valve closing at the wrong time, is postulated.

Acceptable Risk

Acceptable Risk is the level of risk that a community is willing to accept for a project to go forward or for a facility to continue to operate. It is a subjective value depending on factors such as benefit to the community and familiarity with the hazards.

Risky Matrices

Risk matrices are widely used in the process industries. Details vary considerably from company to company, particularly with regard to the size of the matrices, but generally a process such as the following is used.

1. A hazard is identified.

2. The consequence of that hazard is determined. The most important consequence is usually do with safety, but environmental, economic and public relations impact can also be considered.

Hard Times for Culture Change

There has been much discussion in recent years as to how to develop new and improved cultures within the process industries. There appears to be an implicit assumption in these discussions that ours is the first generation to wrestle with the problem of creating a new culture. Nothing could be further from the truth. Indeed, it can be instructive to examine how previous generations affected cultural change with respect to industrial safety and environmental performance, and to consider how their techniques and approaches may apply to our times.

Let's not make common cause


The picture at the head of this page shows the tsunami surging through the Fukushima-Daiichi nuclear power plant complex in the year March 2011. This was a tragic, yet powerful, illustration of many common cause effects. The incident started with an earthquake that knocked out the reactors' operating systems. The earthquake was quickly followed by a tsunami that knocked out all the backup systems. Hence the reactor cores overheated and, in some cases, melted down. The earthquake was the common cause for the failure of the reactors and of their backup systems.

Double Contingency

During process hazards analyses It is common to hear phrases such as, "Double contingency doesn't count, you know". What the speaker means by this is that only single failures should be considered when determining what could go wrong and how risk can be managed.

Subscribe to Risk