PSI - Issue 44

Mariano Ciucci et al. / Procedia Structural Integrity 44 (2023) 347–354

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Mariano Ciucci et al. / Structural Integrity Procedia 00 (2022) 000–000

1. Introduction The impact of a natural disaster on a facility storing or processing dangerous substances can result in the release of those hazardous substances with possible severe off-site consequences through toxic-release, fire or explosion scenarios. Accidents triggered by a natural hazard, involving release of dangerous substances are commonly referred to as NaTech events. One of the main issues of NaTech accidents is the simultaneous occurrence of a natural disaster and a technological accident; both require simultaneous efforts in dealing with a situation in which lifelines designed for a disaster mitigation are likely unavailable, as they may have been damaged by the natural disaster. In addition, hazardous substances releases may occur from single or multiple sources, resulting in multiple chains of accidents in the same installation, or in different plants, requiring emergency-management resources that unfortunately could be engaged in responding to the natural disaster in other situations, Caputo, A.C et al. (2015). The Directive 2012/18/EU of the European Parliament and of the council of 4 July 2012 on the control of major-accident hazards involving dangerous substances (Directive 2012/18/EU), implemented by the member states recognized the relevance of NaTech events. The implementation of smart technologies (sensors, actuators, innovative systems for seismic protection) to the critical elements of a plant allows the reduction of major hazards and related consequences because it provides simultaneous monitoring and control of natural and technological events. The object of this paper is to provide a clear descriptive overview of smart technologies as efficient tools in reducing the seismic risk of major-hazard industrial plants. In order to achieve this goal it is necessary a complete evaluation of the applicability of these technologies to

the actual conditions and operability of critical elements of major hazard industrial plants. 2. Seismic vulnerability of critical elements in major hazard industrial plants

NaTech events derives from the interaction between industrial and natural hazards. In particular, earthquakes have been recognized as one of the most disruptive natural hazard, as demonstrated by many past earthquake, which raised public concern because of the general unpreparedness of the countries in predicting effects and consequences in the aftermath of a disaster. According to the structural classification of the process plant units the components that can be subjected to major damages and generate serious consequences are the following:

• • Slim vessels (columns, pressure vessels) • • Above-ground squat equipment (large tanks) • • Squat and slender equipment supported by column (elevated tanks, Furnaces, etc..) • • Piping systems and support structures

Risk analysis is the process by which all internal and external hazards associated with industrial activity and conditions that may lead to incidental events with damaging consequences for people, the environment and property are identified. In particular, plants where dangerous substances are involved in industrial processes are defined as “major hazard industrial plant”. Risk analysis is based on a probabilistic approach, since the random variables involved in the assessment of major accidents; risk is generally defined as the probability of a given event occurring in a given period and under specific circumstances. The first step to assess the seismic risk associated with a process activity is to identify incidental scenarios, as a release of hazardous substances, due to the occurrence of a leak/break/failure of an equipment. This can be carried out using various complementary techniques, such as historical analysis, checklists, what-if analysis, HazOp analysis, failure modes and effects analysis or random failure analysis. Then, two separate analyses are required to identify the expected frequency of an incidental scenario: • Fault Trees Analysis (FTA) aims to assess the expected frequency of the incidental scenario starting from the causes and prevention interventions. FTA involves the construction of a logical decision tree using initiator events, enabler events and logical gates linking the various events. The values to be assigned to the causes must be expressed in occasions/year. • Event Trees Analysis (ETA) aims to assess and assign an expected frequency to all possible event evolutions, also considering protection interventions. Subsequently, the calculation of consequences is carried out from a set of boundary conditions, some defined by the standards and others to be identified for each individual industrial site or at the level of an individual scenario. The final objective of a risk analysis is to quantify the risk and, if this is not considered acceptable, to reduce it through