Evaluating and Managing Safety Barriers in Major Hazard Plants

摘要

The European ARAMIS project (Hourtolou and Salvi, 2003) is developing an integrated approach to the modelling and management of major hazard risks for major hazard plants. Central to the model being used is the concept of safety functions and barriers. The project defines safety barriers broadly, so that they include not only physical barriers, control instrumentation and active safety barriers, but also human actions which implement the whole or parts of the safety functions. The performance of each type of barrier depends on its associated level of confidence, i.e. the likelihood that a barrier will achieve the appropriate safety function. This level of confidence depends on how well the barrier is managed throughout its life cycle. This assumption provides the link in the ARAMIS project to the quality of the management system. The life cycle of a barrier starts with its design to meet the requirements of the scenario it must block or control, goes through the correct installation, the correct use and avoidance of misuse or degradation of the barrier, to its maintenance. Monitoring of the performance of the barrier allows the company to learn and improve its safety performance over time, so closing the life cycle loop. The project is developing generic classifications of types of barriers that imply different emphases in the way in which the company must manage them to ensure that they meet their reliability. Assessments of the quality of these different aspects of the management system through audits can thus be linked to barrier performance and so to the risk level of the plant.