Reliability centered preliminary hazard analysis

Preliminary Hazard Analysis (PHA) is a safety analysis method that is applied in the preliminary system design phase [1]. The purpose of PHA is to identify the hazards and assess the relevant risks, in order to support the following safety design. However, traditional PHA has several shortcomings. First, the reliability information of the system is always useful to system safety and rarely used in traditional PHA. Second, the qualitative risk assessment that is used in traditional PHA, specifically, the risk matrix, can easily lead to a subjective assessment. Generally speaking, the effect of traditional PHA is limited. This paper modifies the traditional PHA into the RCPHA (Reliability Centered Preliminary Hazard Analysis) with two distinct advancements: (1) a reliability centered hazard analysis is presented, with a new concept of Hazard occurrence degree, in order to use the reliability data adequately to analyze the probability of hazard occurrence; (2) a multi-level factors integrated assessment of hazard severity based on fuzzy set theory is presented, which achieves the quantitative assessment of system risk. Finally, the RCPHA is validated by analysis of a helm control system.