Consideration on improvement of qualitative risk assessment (Quantification of qualitative risk matrix for PHA)

Quantitative risk assessment of large and complex system developments is becoming a mainstream global trend for risk management. However, qualitative risk assessment such as preliminary hazard analysis (PHA) is extremely crucial in promoting inherent safety design in the early phase of development. Therefore, qualitative risk assessment will play an increasingly important role in complementing quantitative risk assessment. Compared with previous developments, inherent safety design is being pursued more thoroughly as product development becomes larger and more complex. On the other hand, many engineers share their work loads and have more interfaces in their projects. Under these situations, hazard identification and risk evaluation in qualitative risk assessment should be improved with quantified expression. This paper presents a methodology of quantification and approximation formulas for better consistency and information sharing of qualitative risk assessment.