Evaluation of the validity of four hazard identification methods with event descriptions

The aim of the investigation was to develop a new method for evaluating the validity of safety analysis with incident and accident descriptions, and to use the approach on some common methods of safely analysis. For this purpose descriptions of disturbances and accidents were collected in seven Finnish process plants. This resulted in 51 incident descriptions. Complementary material (18 incidents) was collected from the FACTS-data bank. The evaluation concerned four methods - hazard and operability study (HAZOP), action error analysis (AEA), failure mode and effect analysis (FMEA), and management oversight and risk tree (MORT). The basic idea of the evaluations was to use the descriptions of accidents and disturbances as indicators of the real accident contributors, and to decide which of them would have been identified if the methods had been applied in a plant-wide analysis. The results show a total validity of 0.55 of the methods in the eases used in the evaluations. The validity was highest (0.66) in the physical subsystem. In the human subsystem the validity was 0.49, and in the management and information subsystem 0.33. The most problematic contributors to identify were, according to the evaluations, maintenance errors, misdiagnosis of process state and design errors. Factors belonging to the information and management subsystems were expected to be covered mainly on a general level but not so often as incident-specific. The investigation recommends that plant-wide safely analysis be complemented by more detailed analyses of important human activities. The results also show the need for new methods for dealing with the diagnosis of process state. The investigation also recommends the systematic collection of operational experience to complement safely analyses carried out during the design phase.