Catastrophic failure, fault tree analysis

Fault tree analysis is used primarily as a tool for conducting system or subsystem hazard analyses, even though qualitative or top-level (that is, limited number of tiers or detail) analyses may be used in performing preliminary hazard analyses. Generally, FTA is used to analyze failure of critical items (as determined by a failure mode and effects analysis or other hazard analysis) and other undesirable events capable of producing catastrophic (or otherwise unacceptable) losses. 

Historically the FMEA technique has been used extensively used in the aerospace, automotive, electronics, and defense industries because they all require analysis of complex mechanical systems and because the failure of an equipment item can have such catastrophic consequences. The FMEA method has not been used a great deal in the process industries partly because of a perception that its use is very time consuming. The same criticism is sometimes made of the Fault Tree Analysis. In fact, neither the FMEA or FTA methods need to take a lot of time it is just that the level of detail that is necessary for the analysis of, for instance, a nuclear reactor or airplane wing is much greater than that needed for a... 

Are there documents that provide comprehensive analysis of all potential safety and health hazards of the worksite Are there documents that provide both the analysis of potential safety and health hazards for each new facility, equipment, material, or process and the means for eliminating or controlling snch hazards Does documentation exist outlining the step-by-step analysis of hazards in each part of each job, so that yon can clearly discern the evolution of decisions on safe work procedures If complicated processes exist, with a potential for catastrophic impact from an accident but low probability of such accident (as in nnclear power or chemical production), are there documents analyzing the potential hazards in each part of the process and the means to prevent or control them If there are processes with a potential for catastrophic impact from an accident but low probability of an accident, have analyses such as fault tree or what if been documented to ensure sufficient backup systems for worker protection in the event of multiple control failures ... 

Model Based Safety Assessment aims at supporting the Preliminary System Safety Assessment (PSSA) [8]. Before the PSSA is performed, the Functional Hazard Analysis identifies the Failure Conditions (e.g. safety critical situations of the system) and assesses their severity on a scale going from No Safety Effect (NSE) to Catastrophic (CAT). Then, during the Preliminary System Safety Assessment, safety models (or alternatively fault-trees) axe built and analysed. A safety model describes formally in which node a fault occurs and how this fault propagates inside the system architecture in order to cause a Failure Condition. 

A fault tree arises from an undesired event, usually of critical or catastrophic kind. Through logic network diagrams the analysis then proceeds to the identification of subordinate events or conditions that may have produced this undesired condition. The components are strictly considered to either operate successfully or fail. Indeed, partial or degraded operation is not considered. Anything less than full operation is a failure. Incidents on a fault tree are arranged in a hierarchical way and can be classified as follows ... 

---