Fault hazard analysis process factors

Bow-Tie Analysis (BTA) a type of qualitative process hazard analysis.The methodology is an adaptation of three conventional system safety techniques Fault Tree Analysis, Causal Factors Charting, and Event Tree Analysis. Existing safeguards (barriers) are identified and evaluated for adequacy... 

Topics Include methods lor calculating damage resulting from the physical effects of accidental releases, using risk assessment Information to specify safety control systems, fault tree analysis, hazards of trace substances, warehouse fires, human exposure to process systems, and solutions to human factor problems. 

Appraisal of technical factors focuses on the equipment and processes within the unit and is considered the physical assessment of current conditions. It is founded on techniques such as hazard and operability studies and fault tree analysis. This technique uses question trees to identify weaknesses in these areas. If weaknesses are identified during the question tree portion of the method, these concerns should be addressed before attempting the ladder assessment portions. 

Do not hesitate to combine some of these tools. For example, when doing a hazard analysis or HAZOP, add a hnman factors analysis (as a subset of the overall hazard analysis) if hnman operators play a significant role. Or, if the HAZOP has identified particularly dangerous deviations of the process resulting from a failure in the system, do an FMEA or fault tree analysis of just that critical subsystan. 

All of these factors determine the stress experienced by the workers and the extent to which operational errors will be recovered before disastrous consequences have ensued. In this context, hazard identification techniques, such as hazard and operability studies (HAZOP), failure modes and effects and criticality analysis (FMECA), fault trees, and others are useful in making the process environment more forgiving. 

CONSTRUCTING THE FAULT TREE. Fault tree construction begins at the top event and proceeds, level by level, until all fault events have been traced to their basic contributing events or basic events. The analysis starts with a review of system requirements, function, design, environment, and other factors to determine the conditions, events, and failures that could contribute to an occurrence of the undesired top event. The top event is then defined in terms of sub-top events, i.e., events that describe the specific "whens and wheres" of the hazard in the top event. Next, the analysts examine the sub-top events and determine the immediate, necessary, and sufficient causes that result in each of these events. Normally, these are not basic causes, but are intermediate faults that require further development. For each intermediate fault, the causes are determined and shown on the fault tree with the appropriate logic gate. The analysts follow this process until all intermediate faults have... 

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