Assessment and management of ageing of critical equipment at seveso sites

The Directive Seveso III points towards the introduction of plans for a safe management of ageing of critical facilities at major-risk. Such plans have to cover all phases of the life cycle of the equipment and take into account current deterioration mechanisms (i.e. internal and external corrosion, erosion, thermal and mechanical fatigue, etc.). Due to this requirement, there is a need of procedures to check the equipment conditions, especially at the final stages of its life cycle, and evaluate the adequateness of actions for its control. Currently, managers adopt Risk-Based Inspection (RBI) standards, nevertheless it is essential to demonstrate the integration of ageing management within the overall management of major hazard plants. This paper discusses the adequateness of the measures, usually adopted to control the ageing phenomenon in primary containment equipment, whose deterioration could generate a major accident. In order to evaluate the status of such items, a shortcut method has been developed. It represents a first attempt to develop a tool for ageing monitoring. The first release of the method is static and appropriate for independent auditors and inspectors acting on behalf of Seveso Authorities. The second release, which is currently under development, is considered dynamic as information about process variables, external data, inspection information and etc. are continuously collected and processed, in order to provide an overall picture of the ageing of systems in a form of an index. These indexes allow the realtime forecasting of the equipment deterioration process and its management based on the industrial risk acceptance levels. The core of the method is a dynamic model of the strengths that accelerate the degradation processes and factors that slow down them. Based on this model a “digital twin” of a complex plant can be built, by integrating smart sensors and other smart devices.