La frecuencia de los accidentes es un aspecto muy importante en el campo del análisis del riesgo. Variables cómo el factor humano en general no se consideran explícitamente en su evaluación. Esto se debe a la incertidumbre que se genera debido a la falta de información y la complejidad para calcular este factor. No obstante, el factor humano es una de las mayores causas de eventos no deseados en las industrias de proceso. En esta tesis, se desarrolló un modificador de la frecuencia de accidentes con el objetivo de introducir el factor humano en la estimación de riesgo. Este modificador tiene en cuenta variables como: el factor organizacional, el factor de las características del trabajo y el factor de las características personales. La inclusión del factor humano se hizo mediante la aplicación de dos metodologías: La lógica difusa y la simulación de Monte Carlo. La primera de ellas se basa en el funcionamiento del razón humana, por ello fue necesaria la contribución de expertos internacionales en el área de estudio a través de su contribución en un cuestionario. En la segunda, Montecarlo, las variables son representades por funciones de probabilidad a través de un tratamiento probabilístico. Los modificadores fueron aplicados a cuatro casos de estudio de industrias químicas reales: dos relacionados con empresas que almacenan productos inflamables y dos que almancenan productos tóxicos e inflamables. Los nuevos valores de frecuencia, después de aplicar el modificador obtenido, son considerados más realistas debido a que ya incluyen el factor humano. Además, los modelos fueron validados con la comparación de los resultados obtenidos con el método internacionalmente aceptado para la evaluación de riesgo: el Análisis Cuantitativo de Riesgo (ACR). Consecuentemente, la evaluación final de riesgo es más conservadora aunque en la línia de los resultados obtenidos a partir de un ACR.
González, J.R.; Guix, A.; Martí, V.; Arnaldos, J.; Darbra, R.M. International Conference on Uncertainty Quantification in Computational Science Engineering p. 68-73 Presentation's date: 2015-05-27 Presentation of work at congresses
Four strategies can be used to achieve safety in chemical processes: inherent, passive, active and procedural; however, the one that offers better results is the inherent safety approach, especially if applied at the initial stages of a project. Inherently Safer Design (ISD) permanently eliminates or reduces hazards to avoid or reduce the consequences of incidents, and can be applied using four strategies: substitution, minimization, moderation and simplification. In this paper, a methodology which allows combining ISD strategies with Quantitative Risk Assessment (QRA) in order to optimize the design of storage installations is proposed; taking into account that 17% of the major accidents in the chemical industry occur during the storage process, causing significant losses, it becomes important to improve safety in these installations. The proposed method applies QRA to estimate the risk associated to a specific design, which can later be compared to others in order to decide which one is inherently safer, incorporating complex phenomena like the domino effect and possible affectation to material and human vulnerable elements. The methodology is applied to two case studies, one based on the San Juanico tragedy occurred in Mexico, 1984, and another one focused on a chlorine storage installation; in this way the method is evaluated on two types of plant, one related to flammable materials and another to toxic substances.
Segui, X.; Darbra, R.M.; Vílchez, J.A.; Arnaldos, J. Journal of loss prevention in the process industries Vol. 32, p. 404-414 DOI: 10.1016/j.jlp.2014.10.017 Date of publication: 2014-11-01 Journal article
A tool for the quantification of the consequences of toxic dispersions coming from fires in warehouses has been developed. This tool is expected to be applied in the framework of the risk assessment in Catalonia, specifically in the Quantitative Risk Assessment. The present study is based on the criteria gathered in the technical guide BEVI 3.2 and the methodology CPR-15 used in the Netherlands. Hence, the approach performed accepts the main body of the foresaid methodology but implements a different and free source dispersion model, a modified Gaussian model that takes into account the warehouse effect. In the work conducted, a historical analysis of accidents involving fire in warehouses has been performed in order to justify the importance of assessing their potential toxic dispersions. Furthermore, the tool has been tested in different case studies providing results that have been compared with other methodologies, observing similar results that can be useful for the stakeholders and decision makers in the framework of the risk assessment. (C) 2014 Elsevier Ltd. All rights reserved.
A tool for the quantification of the consequences of toxic dispersions coming from fires in warehouses has been developed. This tool is expected to be applied in the framework of the risk assessment in Catalonia, specifically in the Quantitative Risk Assessment. The present study is based on the criteria gathered in the technical guide BEVI 3.2 and the methodology CPR-15 used in the Netherlands. Hence, the approach performed accepts the main body of the foresaid methodology but implements a different and free source dispersion model, a modified Gaussian model that takes into account the warehouse effect. In the work conducted, a historical analysis of accidents involving fire in warehouses has been performed in order to justify the importance of assessing their potential toxic dispersions. Furthermore, the tool has been tested in different case studies providing results that have been compared with other methodologies, observing similar results that can be useful for the stakeholders and decision makers in the framework of the risk assessment
Planas, E.; Arnaldos, J.; Darbra, R.M.; Muñoz, M.A.; Pastor, E.; Vílchez, J. Journal of loss prevention in the process industries Vol. 28, p. 109-117 DOI: 10.1016/j.jlp.2013.04.005 Date of publication: 2014-04-11 Journal article
This paper aims at presenting the evolution of process safety in Spain from various points of view. In first place, a study of the accidents occurred in this country in the process industry and in the transportation of chemical substances is presented. After this, the starting point of the process safety research in Spain and its evolution during the years are explained. The importance of this topic has also been reflected in the chemical engineering studies in some Spanish universities. Therefore, the current status of the studies on process safety in Spain is analyzed in this paper. A section has also been devoted to the process safety in the Spanish industry. An analysis of the related legislation and its implementation in the Spanish process industry is also presented in this paper. Finally, the professional career of Prof. Joaquim Casal, the pioneer in Spain in process safety and risk assessment, is summarized.
It is well known that the domino effect can have a major impact on accidents in storage facilities, as it can increase the consequences of an initial event considerably. However, quantitative risk assessments (QRAs) do not usually take the domino effect into account in a detailed, systematic way, mostly because of its complexity and the difficulties involved in its incorporation. We have developed a simple method to include the domino effect in QRAs of storage facilities, by estimating the frequency with which new accidents will occur due to this phenomenon. The method has been programmed and implemented in two case studies. The results show that it can indeed be used to include the possibility of domino effect occurrence in a QRA. Furthermore, depending on the design of a facility, the domino effect can have a significant effect on the associated risk.
El almacenamiento de materiales peligrosos es una parte necesaria del ciclo de vida y de la operación regular de cualquier planta de procesos que intrínsecamente entraña ciertos riesgos y peligros. Los resultados de análisis históricos revelan que el 17% de los accidentes graves en la industria de procesos ocurren en terminales de almacenamiento, y la NFPA de USA reportó que, en 2009, 13% de los grandes incendios que ocurrieron en el país tuvieron lugar en instalaciones de almacenamiento, causando $69.980.000 en pérdidas. Por lo tanto, es claro que una metodología para la optimización del diseño de terminales de almacenamiento desde el punto de vista de la seguridad de procesos podría ser muy útil. Una metodología que permite hacer esto, a través de la combinación del Análisis Cuantitativo de Riesgos, el Diseño Inherentemente Seguro y la Optimización, ha sido desarrollada en esta tesis. La metodología ha sido aplicada a un caso de estudio real, obteniéndose resultados que la validan como una herramienta útil para el diseño de terminales de almacenamiento.
The storage of hazardous materials is a necessary part of the life cycle and operation of any process plant, which intrinsically entails certain hazards and dangers. The results of historical analysis reveal that 17% of major accidents in the process industry occur in storage terminals, and the NFPA of the USA reported that in 2009, 13% percent of the major fire accidents that occurred in that country took place in storage installations, causing $69,980,000 in losses. Therefore, it is clear that a methodology for the optimization of the design of storage terminals from a safety point of view could be very useful. A method that allows doing this, through the combination of Quantitative Risk Assessment, Inherently Safer Design and mathematical optimization, has been developed in this thesis. This methodology has been applied to a real life case study, obtaining results that validate it as a useful tool in the design of storage terminals.
González, J.R.; Darbra, R.M.; Arnaldos, J. International Conference on Chemical and Process Engineering p. 193-198 DOI: 10.3303/CET1332033 Presentation's date: 2013-06 Presentation of work at congresses
The frequency of an accident scenario is most commonly assessed by a generic failure frequency approach; the accuracy of the calculations is based on the quality of the data used. There exist different sources of generic failure frequencies such as the Reference Manual Bevi Risk Assessments (2009), the Failure Rate and Event Data for use within Risk Assessments of the HSE (2012), and the Handbook of Failure Frequencies of the Flemish Government (2009). The differences between them rely on the factors considered for their calculation and on the way the failures have been classified. Each one of the aforementioned sources takes into account different variables, but aspects such as the mechanical failures or the human factor are not explicitly detailed. Although the mechanical failures may have been considered indirectly, the human factor is difficult to quantify. The latter is a major cause of undesired events in process industries. Due to the complexity of quantifying human error and the causes that lead to it, this factor is not often considered in most of the generic failure frequencies databases. Through the use of fuzzy logic, the human factor is going to be introduced in the failure frequency estimation of storage vessels in chemical plants. This theory allows including qualitative variables not considered by traditional methods and deal with the uncertainty involved. In this way, the failure frequency estimation for storage vessels will be more realistic and accurate. To design the model the expert's opinion is going to be taken into account through a questionnaire.
Inherently Safer Design (ISD) or Inherently Safer Technology (IST) is a concept that, in direct relation to the process industries, dates from 1974, when, after the Flixborough explosion Trevor Kletz questioned the need for such large quantities of hazardous materials to be stored in process plants, as well as the need for processing at such elevated pressures and temperatures. The Center for Chemical Process Safety (CCPS) has produced a definition for Inherently Safer Technology:
“Inherently Safer Technology (IST), also known as Inherently Safer Design (ISD), permanently eliminates or reduces hazards to avoid or reduce the consequences of incidents. IST is a philosophy, applied to the design and operation life cycle, including manufacture, transport, storage, use, and disposal. IST is an iterative process that considers such options, including eliminating a hazard, reducing a hazard, substituting a less hazardous material, using less hazardous process conditions, and designing a process to reduce the potential for, or consequences of, human error, equipment failure, or intentional harm. Overall safe design and operation options cover a spectrum from inherent through passive, active and procedural risk management strategies. There is no clear boundary between IST and other strategies.” ...
The storage of dangerous substances is a high risk procedure: a historical analysis revealed that 17% of the major accidents associated with the chemical industry are related to this process. When a storage facility is designed, the investment in safety is not always optimal. The safety measures that are applied are sometimes redundant or ill-maintained. One way to improve safety in a storage facility would be to take advantage of the fact that dividing the mass of dangerous substance results in less catastrophic accidents. In this paper, we present a new method for optimizing the design of storage plants and minimizing the risk by calculating the ideal number of tanks and improving the way in which money is invested in safety. This is achieved by redefining how to estimate risk and by applying the principles of mathematical optimization to quantitative risk analysis. The method is explained step by step. We also present two case studies and a validation of the method using risk analysis software and iso-risk curves.
Risk is a function of two variables: the frequency of an occurrence and the consequences associated to said event. There are many methods that can be used to estimate the frequency of an accident, like failure and event trees, historical analysis, Monte Carlo simulations and many others. Many times, these methods produce values that can be used to know the frequency of an event in a single unit or piece of equipment, and not the frequency with which the event will occur in a whole installation or industrial site.
In installations in which there are similar or identical equipment, like storage parks, it would be useful to know the frequency with which certain accidents will occur in the installation, not per equipment, but in the totality of the site. There are studies like Quantitative Risk Assessment (QRA) in which this information could be used in order to reduce the time needed to complete the study. When performing QRAs in installations with similar equipment, sometimes only one scenario is defined for many equivalent units, and the frequency of the accident studied in said scenario is multiplied by the number of equipment in which it can occur, in order to take into account the fact that the accident will always be similar, but that it can happen in many units. However, this approach does not take into account the fact that the equipment may interact with each other after an accident in a domino effect, so that the possibility of a certain accident occurring in the installation is higher than only the possibility of it occurring in any and each of the units". ..
The Buncefield fire was a major accident that occurred in the Hertfordshire Oil Storage Terminal, on December 11, 2005. A series of failures during operations in the terminal resulted in a petrol overflow in one of the tanks (believed to have started at 5:20 a.m.), which went unnoticed for about forty minutes, resulting in a continuous release of the product during a significant amount of time. Although the product was spilled into a bund in which several tanks were placed, limiting the size of the release, a flammable cloud of considerable dimensions formed, and started drifting through the terminal. At 6:01 a.m. the first (and largest) of a set of explosions was registered, meaning that the cloud reached an ignition source at this point. After the first explosion, subsequent accidents, involving other explosions and fires occurred in a domino effect, destroying 20 storage tanks and causing 43 injuries and millionaire losses. The event has been described as the worst of its type in the UK since the Flixborough disaster in 1974.
In this work, a model that can be used to estimate the impact of the domino effect on accident frequencies in Quantitative Risk Assessment (QRA) of storage installations, developed by some of the authors, and published in the Process Safety and Environmental Protection Journal, has been applied to a layout based on the Hertfordshire Oil Storage Terminal, in order to determine the differences that would exist in the results of two QRAs of the installation, one performed in the traditional way, and another taking in to account the domino effect. ..
Medina, H.; Arnaldos, J.; Casal, J.; Bonvicini, S.; Cozzani, V. Journal of loss prevention in the process industries Vol. 25, num. 3, p. 489-493 DOI: 10.1016/j.jlp.2011.12.005 Date of publication: 2012-05 Journal article
Crude oil and other liquid materials are transported in large quantities through pipelines. Pipelines are an
efficient and safe transport way as compared to both rail and road transportation, both from the
economical and environmental points of view. Nevertheless, loss of containment accidents can occur due
to external action ea mechanical impact, for examplee or to corrosion, aging, etc. Even though the
frequency of such events is certainly very low, the effects and consequences on environment can be very
The consequences of accidents in pipelines can be efficiently reduced through a suitable design of the
whole system. One of the points which must be decided in the design is the installation of blocking
valves at appropriate distances, so that emergency shutdowns can interrupt the flow of substance and
isolate the section where the loss of containment has taken place. In the case of pipe rupture the amount
released is therefore limited to the content between two consecutive valves, usually placed according to
heuristic criteria. However, if too many valves are used, the capital cost of equipment increases excessively,
and if too few are used, the risk of serious accidents increases.
In this paper we consider the possibility of improving the design of such systems by applying riskbased
optimization criteria. We propose an optimization methodology to solve this conflict by means
of an objective function that analyzes the variations in overall costs, including the cost of the investment
(with specific reference to blocking valves) and the cost of accidents. The result is an optimum situation
in which costs are kept to a minimum. As an example, we apply the methodology to the transportation of
gasoline by pipeline.
The design storage installations for dangerous substances can be optimized from a safety and risk point of view by combining quantitative risk analysis and mathematical optimization techniques; the consequences of accidents are directly proportional to the mass involved in them, which means that in a storage installation, if the totality of the stored substance is divided into more tanks, the consequences when an accident occurs in any of the units will be less significant than if all the mass was stored in one tank (in installations where there is low possibility of domino effect occurrence). However, as more tanks are used to store the mass, the economical investment will also increase; then, a situation arises between two conflicting objectives, that can be solved through the use of multi objective optimization. In this paper, a method to solve the multi objective optimization problem between risk and investment for storage facilities that have low domino effect probability of occurrence is proposed and applied to a case study involving a facility that stores chlorine. The final result is the design that represents the best compromise solution between risk and investment for the installation.
The design storage installations for dangerous substances can be optimized from a safety and risk point of view by combining quantitative risk analysis and mathematical optimization techniques; the consequences of accidents are directly proportional to the mass involved in them, which means that in a storage installation, if the totality of the stored substance is divided into more tanks, the consequences when an accident occurs in any of the units will be less significant than if all the mass was stored in one tank (in installations where there is low possibility of domino effect occurrence). However, as more tanks are used to store the mass, the economical investment will also increase; then, a situation arises between two conflicting objectives, that can be solved through the use of multi objective optimization.
Storing hazardous substances is a process that entrails high risk, and in which many resources are spent in the planning of safety measures; however, safety could be included at the initial stages of the design of this type of installations, by optimizing the number of tanks that are used to store the substance. The effects and consequences of major accidents are directly proportional to the mass of materials involved in them; therefore, if the mass was divided in more containing units, the consequences at the moment of an accident occurrence would be lesser. However, as more units are used to store a dangerous substance in an installation, the risk of domino effect occurrence at the moment of an accident also increases. The objective of this paper is to develop a methodology that allows finding the optimum number of units that have to be used to store dangerous materials, taking the possibility of domino effect occurrence into account. The proposed methodology is described and applied to a case study as a decision making tool, obtaining results that demonstrate that the design of storage installations can be improved from a risk point of view, by combining quantitative risk analysis and optimization techniques.
Risk analysis is a topic of high relevance in chemical engineering. Courses on this topic are being introduced increasingly
into the university curricula. The investigation of real cases is an interesting opportunity to consolidate the
concepts taught in such courses and to get a better engagement of students through a creative work. The exercise
proposed in this paper has to be performed by a group of students to whom a set of information has been provided.
In the exercise, the students play the role of an expert team: they have to deliver a final report including diverse
sections such as the description of the accident, the explanation of why and how it occurred, different calculations
and finally, some conclusions. From the pedagogical point of view, the results obtained from this type of exercise are
very positive and promote the students active and cooperative learning.
Dunjó, J.; Fthenakis, V.; Darbra, R.M.; Vilchez, J.; Arnaldos, J. Process safety and environmental protection Vol. 89, num. 4, p. 214-223 DOI: 10.1016/j.psep.2011.03.001 Date of publication: 2011-07 Journal article
Dunjó, J.; Fthenakis, V.; Darbra, R.M.; Vilchez, J.; Arnaldos, J. Process safety and environmental protection Vol. 89, num. 4, p. 224-233 DOI: 10.1016/j.psep.2011.03.002 Date of publication: 2011-07 Journal article