Fault Tree Analysis Methodology

Chapter 2

2. Literature Review
Root causes analysis is simply a tool designed to help incident investigators describe what happened during a particular incident, to determine how it happened and to understand why it happened.
The definition of a root cause varies between authors and root causes methodologies, with different ‘levels’ of causation being adopted by different systems. Figure 1 illustrates the different levels of cause that can be ascribed to an incident. The root causes lie at level 1 which inevitably influence the effectiveness of all the risk control systems and workplace precautions that exist at levels 2 and 3.
The most useful definition identified to date is the definition used by Paradies and Busch (1988), that is:
The

It is a deductive methodology that is it involves reasoning from the general to the specific, working backwards through time to examine preceding events leading to failure. FTA is used for determining the potential causes of incidents, or for system failures more generally. The safety engineering discipline uses this method to determine failure probabilities in quantitative risk assessments.
A fault tree is a graphic model that displays the various logical combinations of failures that can result in an incident, as shown in figure given below. These combinations may include equipment failures, human errors and management system failures.
The tree starts with a ‘top event’ which is a specific undesired event (accident) or system condition. This top event is then broken down into a series of contributory events that are structured according to certain rules, and logic. This process of breaking down the events to identify contributory causes and their interaction continues until the root causes are identified.
Once the fault tree is completed it can be analyzed to determine what combinations of failures or other faults may cause the ‘top

A broken wrist, for instance, really hurts! But painkillers will only take away the symptoms; you will need a different treatment to help your bones heal properly.
But what do you do when you have a problem at work? Do you jump straight in and treat the symptom, or do you stop to consider whether there’s actually a deeper problem that needs your attention? If you only fix the symptom – what you see on the surface – the problem will almost certainly return, and need fixing over and over again.
However, if you look deeper to figure out what’s causing the problem, you can fix the underlying systems and processes so that it goes away for good.
Root cause analysis RCA is a popular and often-used technique that helps people answer the question of why the problem occurred in the first place. It seeks to identify the origin of a problem using a specific set of steps, with associated tools, to find the primary cause of the problem, so that you