bijan sayyafzadeh

By increasing the number of process industrial plants because of societies necessity to their productions, a new branch of accidents caused by various occurred process failures and their effect on the societies and environment and economy has been introduced. Beside it, the increase of the accidents because of natural hazards effect on the industrial plants and their huge costs to the societies and governments and high vulnerability of plants and urbanized territory to the branch of the accidents, increased the attention to this type of accidents. However, in many parts of the world still do not pay attention seriously to this issue and by considering them as very low probability accidents, eliminate paying attention and accepting the responsibility of them while the frequency of such accidents is under growing! In this article according to the existing statistics, an evaluation and comparison of consequences of natural hazards that caused NaTech events has been done. The purpose of the NaTech events is process events that triggered because of natural hazards that are known as events with low probability and high consequences that can affect a wide area and cause huge accidents associated with domino effects. After introducing and categorizing NaTech events, a comparison of their distribution and consequences of these events in Iran and the world has been done according existing articles and researches. Researches shows opposite of the natural hazards and their effects on some structures and infrastructures, Natech events has not been paid under attention enough in Iran. While the variety of industrial plants and their structures in Iran is high, their existing condition and repairing and maintenance of them is not proper and according collected statistics in this article, the potential of NaTech events is also high in country. In the first step, to increase the preparedness for NaTech events, review of effective world experiences in this field is recommended. Recognition of past events and categorizing them and codification of data that should be included in safety reports and scenarios evaluation and considering the domino effects and review the recommendations in this field are parts of this step.

Process towers or vertical vessels are among the industrial structures that play a key role in the production process of petroleum products and their derivatives in refineries and oil and gas industries. Due to the vulnerability of these structures in past earthquakes, and the lack of valid regulations and methods for seismic analysis and design of these structures, a case study on a designed and constructed process tower 26.5 meters high, located in Qeshm Island Refinery, has been conducted in this research. Since considering a rigid foundation, without the interaction of soil and structure, may lead to wrong results, in this study, the tower has been modeled in Abaqus finite element software considering soil behavior. The Winkler model used for soil modeling and the seismic behavior of the tower was investigated using pushover and incremental dynamic analysis, and finally, the resulting fragility curve is presented to show the structure's vulnerability at different levels of seismic intensities. In this investigation, the probable failures, including the failure of the body and the skirt, as well as the overturning of the structure, have been investigated. According to the incremental dynamic analysis results, no buckling was observed in the body and the tower's skirt before the tower overturned. The results show that overturning was the predominant failure mode and the probability of this failure mode until PGA=0.1g is approximately equal to zero, and for PGA= 0.35g, this probability is less than 20%. But for rare seismic intensities, the overturning probability is considerable.

Recent decades with the birth and growth of the world's industries have witnessed the destructive effects of severe natural events on industrial plants and the consequences and events caused by natural events have drawn a lot of attention to this emerging category of technological events caused by natural events (NaTech). Lack of preparation to face this class of events and confusion to make decisions in providing the appropriate response to the existing conditions by macro decision-makers and emergency response forces and the public have always been observed. Various reasons can be mentioned for it, including the multidisciplinary nature of the subject, the emerging and low statistics of these events, the insufficiency of specialized information, and the adoption of approaches similar to process events. Types of damage to infrastructures and lifelines due to the occurrence of natural events are prominent cases and there are many problems and obstacles in responding to the circumstances of the event. In this article, the investigation of natural seismic events in other countries is discussed and after reviewing the description of the events, the response situation in emergency situations has been investigated and categorized. Using other studies, the status of lifelines and infrastructures is investigated; the response status to emergency situations in the event of a possible natural seismic event in Tehran is discussed.

The vulnerability of industrial plants to natural hazards has made world worries because of countries general disability about the prediction of the level of effects and preparedness for the consequences of these types of events. For this purpose, seismic assessment of plant equipment is a strategic issue. One of the most equipment that is used in most oil & gas plants is stack flares. Stack flares are a type of stacks that are used for burning additional flammable gases before causing any other problem for other plant facilities. Proper seismic assessment of this type of equipment has been missed in the past and its exact performance evaluation can be effective in determining probable damages in future earthquakes and distinguishing the weakness of components of this type of structure. In this study probabilistic seismic behavior of two designed and constructed stack flares are investigated and using incremental dynamic analysis their fragility curve and behavior factor are calculated. Results show that in ordinary intensities, the seismic demand of these structures is not considerable but in range of rare intensities, extreme damages are probable. Also, in the above case studies, the performance of 4 side stack with respect to 3 side stack was more proper, and seems more assessment is needed on the suggested behavior factor by codes.

Risk reduction and management of oil, gas, and petrochemical plants are important in terms of energy supply, financial implications, life loss, and repairs. Probabilistic analysis and reliability methods are effective approaches for calculating the risk and cost to such plants, which are composed of units with different types of equipment and structures that have different responses and consequences. One major piece of equipment in a plant that has been shut down is the flare. Depending on the height, the flares can be self-supported, guy-supported, or derrick-supported. The current study investigated the seismic probability behavior of a derrick-supported flare. An existing flare was investigated using the finite element method and incremental dynamic analysis as a case study. The different limit states of the structures were considered when calculating the fragility curves using the results of incremental dynamic analysis. The results showed that the seismic demand on the main structure of the flare stack in the ordinary seismic intensity range was not significant due to the flexible behavior of the structure.