(23a) Quantification of Human Factors for Quantitative Risk Analysis

Inclusion of human factors (HF) in quantitative risk analysis (QRA) is done by use of human reliability analysis (HRA) techniques. However, HRA methods experience some drawbacks, which lead to uncertainties in human error probabilities (HEP). These limitations lead to uncertainty in QRA results.

This work was founded on premise that most HEPs are inaccurate and therefore do not represent the actual conditions of the plant being analysed (Kariuki and Löwe 2006). It is critical that potential human causes for major accidents be exhaustively identified and quantified for a complete QRA. Unfortunately, the tools currently used by analysts for hazards identification do not adequately address the problem (AIChE 1994). A systematic method to analyse the underlying HF, which cause errors that lead to accidents is needed. This work brings in the aspects of HF into QRA. It applies risk analysis framework and is extended to capture human and organisation factors that influence the operator performance in order to identify the actual error producing conditions.

The work was accomplished in the following steps: i) investigation of state-of-the-art of human factors and human errors understanding in the chemical process industry (Löwe et al. 2005), ii) development of a qualitative human factors assessment tool, iii) development of a framework to identify human error events and to analyse human and organisational factors behind these error events, iv) quantification of the human and organisational factors for quantitative risk analysis (QRA).

This approach has the following advantages: one, it provides a systematic process to identify underlying human factors that act as error producing conditions and two, it enables quantification of these human factors to produce HEP that are more accurate and that reflect the actual conditions of the plant under investigation for use in QRA. It will be part of the overall risk analysis of the plant.