Abstract
It is important to analyze the cause of an accident so as to prevent further incidents of a similar kind.
Variation Tree Analysis (VTA) and Why-Why analysis are accident investigation methods to analyze an accident due to human factors in Mitsubishi Chemical Corporation.
VTA is the method to employ time series analysis of the circumstances at the time of an accident, with particular emphasis on the actions and judgments of human. Why-Why analysis is the method to identify the underlying causes of accidents and develop countermeasures by continually questioning the causes of accidents. So, the causes of an accident are identified through VTA, after that, the causes of the accident are analyzed through Why-Why analysis.
These methods are used easily because they do not need special skill and knowledge. On the other hand, according to the internal investigation, these methods have some problems that they take much time to analyze an accident, it is difficult to identify the root cause of an accident and these analyses sometimes lead to take misguided measures. Because process of Why-Why analysis tend to depend on personal skills, it is difficult to obtain logical results through Why-Why analysis.
To solve these problems, we improve VTA and Why-Why analysis by the following viewpoints.
Narrowing analysis targets - The comprehensive analysis across the all scenario would take much time and manpower. To select the upstream deviation node as the starting point of Why-Why analysis is one of the effective approaches.
Standardizing analysis procedures - The standardized templates will be applied to the analysis procedure to reduce the variation in the analysis results by providing the templates.
Outlining policy for preventive measures against accidents - Accident prevention countermeasures are recognized as three steps as follows. Improvement of the design of manufacturing process and maintenance management. Improvement of the management of the SOP and the skill of the operating staffImprovement of reliability of the individual work execution by operating staff. On assumption the human errors is inevitable, countermeasure of accident is preferentially carried out first to (a), followed by (b) and (c). The analysis of human factors could be analyzed more effectively by these improved methods. Moreover, more effective risk assessment will be possible by using these improved methods and their output.
Improved methods for Human Factors analysis are introduced.
