Risk assessment of petrochemical plants under extreme loading

Energy industries, e.g., petrochemical plants, play a highly important role by producing and supplying energy -the lifeblood of modern society- across the world. Due to high vulnerability and severity of potential accidental consequences under events, such as earthquakes and explosions, these installations are often considered as “special-risk” plants. In fact, many accidents under natural hazards have recently been reported in these industries that caused catastrophic losses of human lives, properties and environmental pollution; see in this respect Fig. 1. Hence, particular attention should be provided to these installations to safeguard them against hazards, such as earthquakes, fire or blasts.

The HMSDC Group is actively working on extreme natural hazard mitigation in such facilities through cutting edge research that involves both numerical and experimental investigations. The group’s expertise in relevant areas, such as earthquake engineering, industrial piping systems, probabilistic analysis and structural dynamics, constitutes its strength to carry out such research. For instance, within a European Union project INDUSE-2-SAFETY (www.induse2safety.unitn.it), it is currently developing a quantitative risk assessment methodology for seismic loss prevention of petrochemical plants and components, e.g., support structures, piping systems, tanks and pressure vessels. This probabilistic-based methodology will ensure safe functioning/shutdown of a plant subjected to ground motions of increasing spectral acceleration. 

The models and methods developed for quantitative risk assessment will be capable of reproducing independent damage scenarios and their interrelation triggered by earthquakes or other extreme hazards in petrochemical or similar installations. This will be achieved through a number of steps: (i) development of a systematic list of top events and accident conditions caused by responses of plant components under an accident; (ii) implementation of equipment vulnerability models able to compute the probability of occurrence of the above cited top events as a function of the hazard; (iii) development of a methodology to generate accident scenarios and propagation of uncertainties in a Domino-like fashion including likely interactions between plant equipment; (iv) development of methods and models for estimating damage to plant equipment and physical consequences according to the above cited uncertainty propagation scenarios; (v) development of a method to compute synthetic performance estimation parameters, e.g., risk indices etc., expressing seismic risk of the plant and a method to rank criticalities of process units; (vi) application of the risk assessment procedure developed above to the Case Study plant. An example of risk assessment of a system subjected to earthquake loading is illustrated in Fig. 2. 

 
Fig. 1 Earthquake consequences on a petrochemical plant (Japan, 11/03/ 2011);

 

Fig. 2. Example of seismic risk evaluation of a system