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TOPHAZOP: A knowledge-based software tool for conducting HAZOP in a rapid, efficient yet inexpensive manner
Abstract
Hazard and operability (HAZOP) studies constitute an essential step in the risk analysis of any chemical process industry and involve systematic identification of every conceivable abnormal process deviation, its causes and abnormal consequences. These authors have recently proposed optHAZOP as an alternative procedure for conducting HAZOP studies in a shorter span of time than taken by conventional HAZOP procedure, with greater accuracy and effectiveness [Khan, F. I. and Abassi, S. A., optHAZOP. An effective and efficient technique for hazard identification and assessment Journal of Loss Prevention in the Process Industries, 1997, 10, 191–204]. optHAZOP consists of several steps, the most crucial one requires use of a knowledge-based software tool which would significantly reduce the requirement of expert man-hours and speed up the work of the study team. TOPHAZOP (Tool for OPTmizing HAZOP) has been developed to fulfil this need.The TOPHAZOP knowledge-base consists of two main branches: process-specific and general. The TOPHAZOP framework allows these two branches to interact during the analysis to address the process-specific aspects of HAZOP analysis while maintaining the generality of the system. The system is open-ended and modular in structure to make easy implementation and/or expansion of knowledge. The important features of TOPHAZOP and its performance on an industrial case study are described.
... Multiple prototypes were built using rule networks for cause and consequence reasoning, such as TOPHAZOP, OptHAZOP, EXPERTOP, and ExpHAZOP + (cf. Chae and Yoon, 1994;Khan and Abbasi, 1997a;Khan and Abbasi, 1997b;Khan and Abbasi, 2000;Rahman et al., 2009). Graf and Schmidt-Traub (2000) developed a modelbased approach for hazard identification based on qualitative plant models formulated as statecharts. ...
... The research group around Khan et al. developed various approaches: OptHAZOP by (Khan and Abbasi, 1997b), TOPHAZOP by (Khan and Abbasi, 1997a), EXPERTOP by (Khan and Abbasi, 2000), and ExpHAZOP+ by (Rahman et al., 2009). The ExpHAZOP+ approach consists of a graphical user interface, a knowledge base, and an inference engine. ...
... Initial research attempts used rule-based approaches in the form of expert system shells or other inference engines to identify HAZOP-relevant scenarios or their components, such as causes or consequences (cf. Suokas et al., 1990;Chae and Yoon, 1994;Heino et al., 1995;Khan and Abbasi, 1997a). The major disadvantage of rule-based systems is that the rules must be matched precisely to the problem statement, leading to nested rules and inefficiencies in larger domains (cf. ...
The hazard and operability (HAZOP) method is widely used in chemical and process industries to identify and evaluate hazards. Due to its human-centered nature, it is time-consuming, and the results depend on the team composition. In addition, the factors time pressure, type of implementation, experience of the participants, and participant involvement affect the results. This research aims to digitize the HAZOP method. The investigation shows that knowledge-based systems with ontologies for knowledge representation are suitable to achieve the objective. Complex interdisciplinary knowledge regarding facility, process, substance, and site information must be represented to perform the task. A result of this work is a plant part taxonomy and a developed object-oriented equipment entity library. During ontology development, typical HAZOP scenarios, as well as their structure, components, and underlying causal model, were investigated. Based on these observations, semantic relationships between the scenario components were identified. The likelihood of causes and severity of consequences were determined as part of an automatic risk assessment using a risk matrix to determine safeguards reliably. An inference algorithm based on semantic reasoners and case-based reasoning was developed to exploit the ontology and evaluate the input data object containing the plant representation. With consideration given to topology, aspects like the propagation of sub-scenarios through plant parts were considered. The results of the developed knowledge-based system were automatically generated HAZOP worksheets. Evaluation of the achieved results was based on representative case studies in which the relevance, comprehensibility, and completeness of the automatically identified scenarios were considered. The achieved results were compared with conventionally prepared HAZOP tables for benchmark purposes. By paying particular attention to the causal relationships between scenario components, the risk assessment, and with consideration of safeguards, the quality of the automatically generated results was comparable to conventional HAZOP worksheets. This research shows that formal ontologies are suitable for representing complex interdisciplinary knowledge in the field of process and plant safety. The results contribute to the use of knowledge-based systems for digitizing the HAZOP method. When used correctly, knowledge-based systems can help decrease the preparation time and repetitious nature of HAZOP studies and standardize results.
... Other approaches were using rule networks for consequence reasoning e.g. Chae et al. (1994), TOPHAZOP by Khan and Abbasi (1997b) or EXPERTOP by Khan and Abbasi (2000) value to the HAZOP team in charge to be applicable and used within HAZOP studies. Hence, the following requirements for improvements to the HAZOP process are identified: ...
... The research group of Khan et al. developed various approaches: OptHAZOP by Khan and Abbasi (1997b), TOPHAZOP by Khan and Abbasi (1997a), EXPERTOP by Khan and Abbasi (2000) and Ex-pHAZOP + by Rahman et al. (2009). The ExpHAZOP+ approach consists of the typical elements of an expert system: graphical user interface, knowledge base and inference engine. ...
For more than 30 years, multiple research groups have worked on the automation of hazard and operability (HAZOP) studies, or more specifically on the hazard identification process. So far, very few of these approaches have been used in the chemical process industry. Automatic hazard identification is a knowledge-intensive process that demands high standards with regard to the way in which knowledge is stored and made available. There are various suitable approaches to the qualitative modeling of processes and plants, which are the foundation for reasoning systems that are used for the identification of hazards. Additionally, there are quantitative methods that are based on process simulations and can be used to identify potential hazards. The investigation of the state of research demonstrates that there are sophisticated technologies for automated systems that include powerful reasoning techniques. The benefits and shortcomings of existing technologies are discussed with regard to their industrial applicability. Often, the quality of the necessary specific and generic knowledge is not sufficient to detect potential hazardous events and operational malfunctions. Computer-aided HAZOP systems should be integrated with computer-aided design- or process simulation software using common data models based on the digital representation of the process plant. In order to be used by HAZOP practitioners automated systems need to be comprehensive, serve as specialized decision support systems, and be tested and evaluated using round robin tests.
... The vapor cloud then drifts downwind till it meets an ignition source, leading to a flash fire or an explosion. More often than not, these happenings cause other storage units or reactors to fail, leading to much bigger releases of flammable substances, in turn to an escalation of the initial accident [17,18,22,23]. This 'domino effect' has been responsible for some of the most catastrophic process industry accidents [18,29]. ...
... More often than not, these happenings cause other storage units or reactors to fail, leading to much bigger releases of flammable substances, in turn to an escalation of the initial accident [17,18,22,23]. This 'domino effect' has been responsible for some of the most catastrophic process industry accidents [18,29]. It is also an ever-present risk. ...
Most accidents in chemical process industry, as well as a large number of fires in general, are triggered by accidental spilling of flammable liquids. Such spills either get auto-ignited or are set on fire by one or the other ignition source. If other flammable material happens to catch fire before the initial fire is extinguished, the accident gets escalated. In many situations, the escalation is catastrophic, resulting in very large fires, with or without explosions. This paper assesses the transient models developed so far to predict the areas covered by accidental fuel spills.
... "Two women, trapped in a station wagon which met witha traffic accident near Dalby, Australia, died when an LPGtank in the back of the car suffered a BLEVE. The accidentwhich took place on 19 March 2009, had initially led to afire. The fire then engulfed the LPG cylinder causing it toundergo BLEVE even as rescuers tried frantically to get thetrapped women out". ...
... It may be mentioned that the abovementioned steps necessarily occur when LPG containers suffer BLEVEs. But BLEVEs are not confined to flammable substances, and, as noted by Abbasi and Abbasi (2007)"BLEVE accidents have occurred involving ammonia (Casal et al., 2001), chlorine (Marshall, 1987), chlorobutadiene (Khan and Abbasi, 1997c), and phosgene (Marshall, 1987) wherein the explosion did not cause a fireball but was accompanied by dispersion of toxic material. Indeed of the one-third past BLEVE events not involving flammable liquids, the majority have been associated with toxic gases-chlorine (14%), ammonia (10%), and phosgene (2%) account for 76% of the BLEVEs involving non-flammables" (Abbasi and Abbasi 2007a). ...
... It is difficult to understand their failure, especially due to software failures. The dynamic flowgraph method (DFM) which is a digraph-based technique was used to validate the safety requirements of the digital instrumentation Khan and Abbasi (1997a) JLPPI optHAZOP-an optimal approach for HAZOP study Khan and Abbasi (1997b) JLPPI TOPHAZOP-a knowledge based software tool for HAZOP study Kennedy and Kirwan (1998) SS SCHAZOP-safety culture hazards and operability study McCoy et al. (1999aMcCoy et al. ( ,b,c, 2000a PSEP HAZID-a computer aided hazard identification method Mushtaq and Chung (2000) JLPPI Batch HAZOP methodology Cagno et al. (2002) RESS HzM-multi level HAZOP analysis Garrett and Apostolakis (2002) RESS Dynamic Flowgraph Method (DFM) Baybutt (2003) PSP Major Hazards Analysis (MHA) Triplett et al. (2004) PSP Chain of Event Analysis (CEA) Zhao et al. (2005a,b) PSEP PHASuite-a software system for an automated hazard analysis Labovský et al. (2007) JLPPI Model-based HAZOP study Ramzan et al. (2007) PSP Extended Hazop Laskova and Tabas (2008) PSP An integrated HAZOP and systematic hazard identification method Cui et al. (2008) PSP LDGHAZOP-a layered digraph model for the HAZOP analysis Chung (2008, 2009) JLPPI CHECKOP-an automated tool for batch HAZOP analysis Rahman et al. (2009) JLPPI ExpHAZOP + -an automated HAZOP analysis methodology Wang et al. (2009) PSEP Signed graph based HAZOP analysis JLPPI Database of expert knowledge Risk assessment Baybutt (2007) PSP Improved Risk Graph Baybutt (2012) JLPPI Use of risk tolerance criteria to determine the SIL Safety management Svenson (1991) RA Accident Evolution and Barrier (AEB) Model Hale et al. (1997) SS Structural Analysis and Design Technique (SADT) Rasmussen and Grtinberg (1997) JLPPI Uncontrolled Flow of Energy (UFOE) Model Youngblood (1998) RA Top Event Prevention Analysis (TEPA) Duarte and Pires (2001) PSP Logic diagram based approach to improve the safety systems Svedung and Rasmussen (2002) SS An accident mapping method Kim et al. (2003) JLPPI yAGAS-an experience based approach to develop accident scenario Gupta and Edwards (2003) JHM A graphical method to measure ISD Leveson (2004) SS (Garrett and Apostolakis, 2002). Ramzan et al. (2007) developed the Extended HAZOP which was supported by dynamic simulation. ...
... This method increased the efficiency, effectiveness and reliability of the HAZOP study. As a further improvement of optHAZOP, Khan and Abbasi (1997b) subsequently proposed a knowledge based software tool, termed TOPHAZOP, to further reduce the requirement of expert man-hours and to speed up the work of the study team. Subsequently, Khan and Abbasi (2000a) combined their previous developments of TOPHAZOP and opt-HAZOP and developed EXPERTOP which is a complete expert system. ...
The paper reviews past progress in the development of methods and models for process safety and risk management and highlights the present research trends; also it outlines the opinions of the authors regarding the future research direction in the field. Based on the open literature published in the leading journals in the field of safety, risk and reliability, the review covers the evolution of the methods and models developed for process safety and risk management. The methods and models are categorized as qualitative, semi-quantitative, quantitative and hybrid. The progress in the last few decades is discussed in the context of the past. Developments in the current decade formulate the basis of the present trends; future directions for research in these fields are also outlined. The aim of the article is to provide a historical development in this field with respect to the driving forces behind the development. It is expected that it will help researchers and industrial practitioners to gain a better understanding of the existing concepts. At the same time the aim is to provide direction to bridge the existing gaps through research and developments.
... (Khan & Abbasi, 1997a) Developed OptHAZOP, a tool based on experience feedback that enables efficient management and organisation of HAZOP study databases. Building upon this tool, they further created TOPHAZOP (Khan & Abbasi, 1997b), an expert system consisting of a database, an inference engine and a graphical user interface (GUI). ...
Risk analysis is crucial in industrial conception. HAZOP is the top risk analysis method for the oil and gas sector. This paper presents a semi-automatic method to address HAZOP's limitations and produce automatic results. The method uses a knowledge base, initially filled with gas liquefaction data, and is enhanced with subsequent case studies. An inference engine processes this data to conduct a HAZOP study. Propagation rules identify potential deviation paths, enabling risk analysis and consequence prediction based on the knowledge base. This method uniquely illustrates deviation paths and introduces nodes along these paths for further study. The findings derive from dynamic knowledge of each system in the knowledge base and can be reviewed and amended by experts.
... (Khan & Abbasi, 1997a) Developed OptHAZOP, a tool based on experience feedback that enables efficient management and organisation of HAZOP study databases. Building upon this tool, they further created TOPHAZOP (Khan & Abbasi, 1997b), an expert system consisting of a database, an inference engine and a graphical user interface (GUI). ...
Risk analysis is crucial in industrial conception. HAZOP is the top risk analysis method for the oil and gas sector. This paper presents a semi-automatic method to address HAZOP's limitations and produce automatic results. The method uses a knowledge base, initially filled with gas liquefaction data, and is enhanced with subsequent case studies. An inference engine processes this data to conduct a HAZOP study. Propagation rules identify potential deviation paths, enabling risk analysis and consequence prediction based on the knowledge base. This method uniquely illustrates deviation paths and introduces nodes along these paths for further study. The findings derive from dynamic knowledge of each system in the knowledge base and can be reviewed and amended by experts.
... Matrix-based (Ni et al., 2010) and index-based methods (Khan and Abbasi, 1998a) were the representatives of qualitative and semi-quantitative risk assessment methods. Other methods such as HAZOP analysis (Khan and Abbasi, 1997), layer of protection analysis (Markowski and Kotynia, 2011), and "What-If" analysis (Assael and Kakosimos, 2010) were also widely used as semi-quantitative hazard identification and risk assessment methods. ...
Multi-hazard accidents in process industries, which can cause more severe consequences compared to individual accidents, have gained growing attention from administrators and scholars in recent years. With the development of process industries and the expansion of the urban area, high-risk zones may emerge in densely populated areas. Accurate risk assessment of the multi-hazard accidents in process industries is essential for protecting properties, human life, and the environment. This study reviews past studies on the risk assessment of three types of multi-hazard accidents in process industries: Natech events, domino effects, and concurrent hazards. The development trends of risk assessment of multi-hazard accidents are analyzed and the research gasps of past research are identified. Based on the identified gaps in previous research, future perspectives on multi-hazard research in process industries are discussed. To improve the assessment methods for multi-hazard risks, more advanced basic models and applicative risk analysis methods are required. Considering multi-hazard interactions and other factors are also important for process plants against multi hazards. This study can potentially contribute to developing better risk assessment models of multi-hazard accidents and therefore safer and resilient process industries.
... Different approaches that have been developed are classified as: (a) using rule networks for consequence reasoning e.g. TOPHAZOP (Khan, 1997b), optHAZOP (Khan, 1997a), ExpHAZOP+ (Rahman, 2009);(b) using to integrate hazard identification into CAD software; (c) using statecharts for hazard identification; (d) using directed graphs for model-based reasoning in combination with rules; (e) based on Petri nets and applied to batch processes, and (f) using recently methods from artificial intelligence (AI). A detail of all these approaches can be found in a review study (Johannes I. Single, 2019). ...
This work proposes a framework for synthesis of safety-related control design in the process industries based on two aspects: (i) critical faults prevention and mitigation and, (ii) pathogenic accidents. The approaches found in the literature are based on the development of control solutions that use the results of hazard identification and risk analysis that were carried out to specify safety requirements to avoid or mitigate critical faults. However, the possibility of occurrence of the undesirable unobserved and/or hidden hazardous events associated with possible pathogenic accidents is not addressed. The objective of this work is to integrate the issue of analysis of pathogenic accidents into the context of synthesis of safety-related control design. Thus, a framework is proposed to: (1) address the issue of pathogenic accidents, which according to the analysis of accident investigation reports, its represent critical and / or undesirable unobserved and/or hidden events during the process of events evolution. This step is based on the analysis of the databases with missing data or incompleted obtained through accident records; (2) proposes an improvement in the hazard identification process, as it considers a systematic integration between the knowledge from experts (eg, automated HAZOP) and accident models that describe the critical and / or unwanted process of events evolution ensuring the principles of defense-in-depth and safe diagnosability; (3) address the use of safety barrier diagrams formalism to design a controlled degeneration process that will be treated locally, by each defense mechanism (eg, prevention / mitigation safety barrier), reducing the damage of the whole process; and (4) address the modeling, analysis and validation of defense algorithms with a focus on the prevention and mitigation of critical faults given a particular critical scenario using a hierarchical control structure based-approach via Petri nets formalism. Finally, the proposed framework is aligned with the requirements of the IEC 61511(2016) and IEC 61508(2010) Standards; and the models generated in Petri nets that have been validated, can be transcribed in an isomorphic way in control programs recommended by the IEC 61131-3 standard. The framework proposed was applied into an application example of an accident that occurred at isomerization unit of the British Petroleum (BP) refinery in Texas - USA.
... Another example of graphical based risk assessment tool is called SAFE (Situative Anforderungsanalyse von Fahraufgaben) which has the benefit of assessing the risk of the car driving task (Fastenmeier & Gstalter, 2007). Additionally, a tool like TOPHAZOP (tool for optimizing HAZOP) was developed to support the HAZOP analysis with shorter durations, greater accuracy and more effectiveness (Khan & Abbasi, 1997). ...
Accident prediction models are used to estimate accident occurrences related to various identified factors. However, human behavioural factor is always absent from a model parameter since the information is usually unavailable in accident data. This study focused on the development of a model that is capable of integrating the human behaviour, engineering and environmental factors that contribute to the pedestrian accident. The developed model can be used to quantify the potential accident risks of pedestrians crossing at signalised intersections in the urban area. Petri Nets π-tool has been applied in this study to achieve integration of behavioural, engineering and environmental factors in assessing the potential risks of crossing pedestrians. Petri Nets is a flexible graphical modelling tool with a strong mathematical basis that is capable of modelling and analysing the system with multiple interactions in pedestrian accident event sequence. Signalised intersections in Kuala Lumpur were used as case studies to predict the risk probability of pedestrian accident occurrences within specific time periods. Site observations were conducted to obtain the pedestrian crossing scenario. The event sequence extracted from this scenario was translated into Petri Nets elements for model formulation. Identified factors were organised into several sub models in the hierarchical model structure. The developed model is called PedCRA (Pedestrian crossing risk assessment) model. Twelve factors were identified as the model parameters and sensitivity analysis was conducted to evaluate the effect of these parameters to the potential pedestrian risk value. The results from this analysis showed that the important parameters are the compliance behaviour of pedestrians, the volume and approach speed of vehicular traffic, the number of lanes and the existence of median. Since the model is designed to only capture an interaction with one approach of the intersections at one time, calibration is required to estimate the risk value for the intersection with 3 or 4 approaches. Validation of the model successfully compared the predicted risk value obtained from the model with the actual risk value obtained from historical accident occurrences at 30 selected signalised intersections in Kuala Lumpur. Chi-Square goodness of fit test indicated that risk values from model and accident data follow the same distribution trend at a 5 percent significance level (p=0.05).
... Another example of graphical based risk assessment tool is called SAFE (Situative Anforderungsanalyse von Fahraufgaben) which has the benefit of assessing the risk of the car driving task (Fastenmeier & Gstalter, 2007). Additionally, a tool like TOPHAZOP (tool for optimizing HAZOP) was developed to support the HAZOP analysis with shorter durations, greater accuracy and more effectiveness (Khan & Abbasi, 1997). ...
Accident prediction models are used to estimate accident occurrences related to various identified factors. However, human behavioural factor is always absent from a model parameter since the information is usually unavailable in accident data. This study focused on the development of a model that is capable of integrating the human behaviour, engineering and environmental factors that contribute to pedestrian accident. The developed model can be used to quantify the potential accident risks of pedestrians crossing at signalised intersections in the urban area. Petri Nets z-tool has been applied in this study to achieve integration of behavioural, engineering and environmental factors in assessing the potential risks of crossing pedestrians. Petri Nets is a flexible graphical modelling tool with a strong mathematical basis that is capable of modelling and analysing the system with multiple interactions in pedestrian accident event sequence. Signalised intersections in Kuala Lumpur were used as case studies to predict the risk probability of pedestrian accident occurrences within specific time periods. Site observations were conducted to obtain the pedestrian crossing scenario. The event sequence extracted from this scenario was translated into Petri Nets elements for model formulation. Identified factors were organised into several sub models in the hierarchical model structure. The developed model is called PedCRA (Pedestrian crossing risk assessment) model. Twelve factors were identified as the model parameters and sensitivity analysis was conducted to evaluate the effect of these parameters to the potential pedestrian risk value. The results from this analysis showed that the important parameters are the compliance behaviour of pedestrians, the volume and approach speed of and the existence of median. Since the model is designed to only capture an interaction with one approach of the intersections at one time, calibration is required to estimate the risk value for the intersection with 3 or 4 approaches. Validation of the model successfully compared the predicted risk value obtained from the model with the actual risk value obtained from historical accident occurrences at 30 selected signalised intersections in Kuala Lumpur. Chi-Square goodness of fit test indicated that risk values from model and accident data follow the same distribution trend at a 5 percent significance level (p=0.05).
... The authors proposed a HAZOP knowledge-base that consists of "processspecific" and "process-general" components for hazard identification in HAZEXPT (Faisal I Khan & Abbasi, 1997a). Based on the HAZOP knowledge-base, an optimal study procedure HAZOP (OptHAZOP) and Tool for optimizing HAZOP (TOPHAZOP) were developed in order (Faisal I Khan & Abbasi, 1997a, 1997b. OptHAZOP attempted to eliminate repetitive tasks in a semi-automated HAZOP study, whereas TOPHAZOP sought a more enhanced systematic structure that incorporates 1) knowledge-base, 2) inference engine, and 3) user interface. ...
... The automation of elements of HAZOP studies has been a topic of research for more than 30 years. The first systems were mainly built on logic trees, rules and rule networks, within expert system shells (see [2]- [4]). Later research approaches used qualitative models for reasoning purposes in combination with rules (see [5]- [8]). ...
Safety assessments are conducted to identify and assess the risks that arise from processes, process plants or technical systems in general. This includes the identification of potential hazards posed by plants. One recognized and generally accepted method for this is the hazard and operability (HAZOP) method. It is a human-centered process that is time- and labor-intensive. In the presented research approach, the structure of a computer-aided HAZOP system is described. The identification of hazards and malfunctions within technical systems is knowledge-intensive. Within this research approach, it transpired that the semantically correct and detailed modeling of deviation cause and effect relationships in the form of ontologies are of particular importance to draw correct conclusions. Thus, the guiding principles of a knowledge representation framework are described from a process safety perspective, and serve as a basis for the automatic identification of hazards. An integral understanding of the process, process plant and involved substances requires extensive knowledge. The way in which this knowledge is used and the search for hazards is conducted has an influence on the completeness of the results. Within this approach, the hazard/malfunction identification is conducted on different layers of abstraction to improve the efficiency of the search algorithm. The proposed methodology is applied within a case study to a technical system that consists of a compressor, vessel and valve. The first results demonstrate that the proposed method is well-suited to understand and identify the context of hazards and malfunctions. Thus, a system for computer-aided HAZOP studies can be used to assist HAZOP conductors in performing hazard analysis while increasing the speed of safety assessments and serving as a decision support system.
... Chemical process industries which involve hazardous chemicals as raw materials and/or products carry a significant risk of accidents that can occur during the transportation, storage, or handling of such chemicals [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. ...
... Fonte: Adaptado de Manuj e Mentzer (2008).2.3 Aplicação de ferramentas da ABNT NBR ISO/IEC 31010:2009Dentre muitas ferramentas que podem ser aplicadas na gestão de riscos, a ABNT (2012) relaciona a aplicabilidade do método de estudo de perigos e operabilidade (HAZOP) aos processos de avaliação de risco, classificando-o como fortemente aplicável na identificação de riscos e análise de suas consequências, além de utilizar a classificação aplicável para a análise na probabilidade de ocorrências, nível de risco e avaliação de risco. A norma ainda enfatiza a relevância da aplicação da técnica identificando os modos de falha, suas causas e consequências por raciocínio indutivo aplicados a sistemas de processo químico, sistemas mecânicos e eletrônicos, procedimentos e sistemas de software e controle de instrumentos críticos.HAZOP é uma técnica qualitativa utilizada em gestão de riscos cujo objetivo é permitir a correlação entre perigos na operabilidade, variáveis de processo e ação requerida para mitigar ou até eliminar os riscos (KHAN;ABBASI, 1997). Essa ferramenta é baseada no 2. AVALIAÇÃO DE RISCOS E EVOLUÇÃO Análise de decisões, estudos de caso e bases de percepções 3. SELECIONAR A APROPRIADA GESTÃO DE RISCO Estratégia proposta: evasão, adiamento, limitação, controle, compartilhamento e segurança 4. IMPLEMENTAÇÃO DE GESTÃO ESTRATÉGICA DE RISCO Capacidade da implementação da estratégia de risco: complexidade, aprendizagem e desempenho 5. MITIGAÇÃO DOS RISCOS NA CADEIA DE SUPRIMENTOS Capacidade da implementação da estratégia de risco: complexidade, aprendizagem e desempenho 1. IDENTIFICAÇÃO DO RISCO Usando múltiplas fontes e classificando risco no fornecimento, operações e demanda na segurança ...
In ironworks industries, a number of risks in processes are observed, due to flaws in the control parameters directly affecting the quality of products supplied to customers. The purpose of this article is to identify potential anomalies during the execution of activities in the production of wire. The formulation of the treatment plan is achieved through the integration of various tools in this case study of a large plant producing long products, applying the mapping process, HAZOP and LOPA combined with critical analysis of experts. The methodology allowed for the identification of potential failures of mapping and was systematized to identify their causes, adding knowledge to operational standards, allowing for an objective approach in the detection of problems and assertive action to fix them by restricting the interference of the anomaly in question with the application of the product by the customer.
... Chemical process industries which involve hazardous chemicals as raw materials and/or products carry a significant risk of accidents that can occur during the transportation, storage, or handling of such chemicals [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. ...
We have recently proposed in this journal a new methodology ‘Risk and Distance Minimization in Process industry Units Siting’ (RIDIMPUS) (J Fail Anal Prev 18:83–91, 2018). The methodology has been developed for siting hazardous utilities within the periphery of a chemical process industry in such a manner that the inter-utility distance is minimized while also minimizing the risk of accidents due to those hazardous utilities. In this follow-up report, we present a case study which demonstrates the applicability of RIDIMPUS and validates its efficacy.
... Abbasi et al. 1 have recently brought out that majority of process industry accidents begin with the accidental spilling of one or the other flammable liquid. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] These spills often lead to fires and/or explosions, escalating the initiating event to catastrophic proportions. [18][19][20][21][22][23][24][25][26] Indeed this type of "domino" or "cascading" effect is more a norm than an exception. ...
Efficacy of all the existing transient models for forecasting the area attained by accidentally spilled
liquid fuels has been sought to be assessed on the basis of experimental data available in prior art. Of the two
models for which required inputs are available in the prior art, the model of Huppert (1982) is able to
forecast spill area with much greater precision than the model of Raj and Kalelkar (1974). Both the models
give better predictions when the spill volume is higher and the spill duration is lower but neither model yields
a correlation between the accuracy of the spill area forecast and the nature of the spilled liquid or the
receiving surface.
... Accidents can occur at different levels and areas in chemical process industry (CPI), during the transportation, storage and/or manufacture of substances [18,[28][29][30][31][32][33][34][35][36][37][38][39][40][41][42]. Generally speaking, accidents in a process industry are divided into three main categories, namely fire, explosion and toxic release [43][44][45][46][47][48][49][50][51]. ...
In the original version of this article, Vipin’s name was incorrect. It is correct as reflected here. The original article has also been corrected.
... Accidents can occur at different levels and areas in chemical process industry (CPI), during the transportation, storage and/or manufacture of substances [18,[28][29][30][31][32][33][34][35][36][37][38][39][40][41][42]. Generally speaking, accidents in a process industry are divided into three main categories, namely fire, explosion and toxic release [43][44][45][46][47][48][49][50][51]. ...
A pool or a pile of a flammable substance catching fire—which is termed a ‘pool fire’—is among the most common of fire-related accidents. In chemical process industries (CPI) in particular, pool fires are the most frequent of all possible types of accidents. Pool fires are also, more often than not, the triggers of larger fires, explosions and/or toxic releases in CPI. As demonstrated in this paper, most of the catastrophic accidents that have occurred in CPI have begun with a pool fire, which has then led to other fires and/or explosions, compounding the initial accident many times over. In day-to-day life also, as also in forest fires, major fire accidents begin with a small pool fire. Due to these reasons an understanding of factors which influence pool fires, and the associated mechanisms, is essential for devising strategies to control and mitigate pool fires. This review, which is specific to pool fires occurring in CPI, recounts illustrative case studies of some major pool fire accidents, performs a past accident analysis and describes pool fire mechanism, modeling and control.
... Or the spilled liquids have evaporated to form highly flammable vapor clouds which have then generated flash fires or vapor cloud explosions. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] These happenings have, in turn, led to more fires and/or explosions, thus multiplying the harm caused by the initial accident several times over. [17][18][19][20][21][22][23][24][25][26] Spills causing such chain of accidents, or 'domino effect', has been a recurring phenomenon of great impact. ...
Very large quantities of flammable substances are produced, transported, and refilled across the world. Of these some, like gasoline and diesel, are liquids at normal temperature and pressure while some others – like liquid petroleum gas (LPG – are pressure liquefied gases. Ever so often accidental spills of these chemicals occur. While some spills are contained before they could do much damage, many others catch fire and often also lead to massive explosions. Indeed, accidental spills have been the initiators of the majority of industrial disasters the world has seen. Given the exceptional importance associated with the containing and controlling of accidental spills, it is essential to understand the factors which effect the spill dynamics so that ways to reduce the risk posed by such spills can be devised. But even as a great deal of work has been done on the dynamics of spills occurring on flat surfaces, little past effort is on record pertaining to the study of spills occurring on inclined surfaces. This is surprising because the spillways actually provided in the industries for large storage tanks invariably have downward slope to enable quick drainage of the flammable liquid away from the storage tank in the event of an accidental leak. The present work is an attempt to make some contribution towards the understanding of the dynamics of spillage of flammable liquids on inclined surfaces. When accidental spills occur in the open – during transportation by road, railroad, or pipeline – the receiving surfaces can be porous and the liquid can percolate down, making environmental contamination that much difficult to remediate. To incorporate this aspect in the present study we have chosen porous surfaces and studied the dynamics of the spill of three different flammable liquids on them at angles of inclination varying from zero to 20°.
... Several catastrophic accidents such as the ones which have occurred at Jaipur [17], Puerto Rico [44], BPL Refinery at Texas City [11], Buncefield [13], and elsewhere have resulted and escalated ( Fig. 1) due to lacunae in plant layouts which failed to provide sufficient barriers to counter the escalation [19,20,37,40]. The frequency of occurrence as well as the scale-with losses running into billions of rupees-has increased public awareness of hazards in chemical process industry [6,7,[22][23][24][25][26][27][28][29][30][31][32][33][34][35], thus elevating the importance of safety considerations within the process plant layout and design frameworks [1][2][3][4][5][47][48][49][50]. Various studies indicate that facility siting plays a very important role in risk reduction and minimizing adverse consequences of accidents as well as in the reduction in the costs of plant operation and maintenance [38]. ...
A new method, RIsk and DIstance Minimization in Process Units Siting (RIDIMPUS), is presented with which hazardous units can be sited in a chemical process facility in a manner that the risk of accidents involving the hazardous units as also the cost of spacing the units is minimized. To achieve this, safety and cost factors were modeled using various governing parameters and then expressions were designed to integrate the safety and the economic concerns to form model equations, inequalities and disjunctions. The resulting nonlinear programming model is solvable by using algorithms and solvers on any common desktop computer, thereby providing an optimal and prompt solution.
... The paper by Suokas et al. (1990) reports 330 expert system rules for deviation causality, 20 for consequences and 20 for safeguards. There have been several subsequent developments using expert system frameworks, such as Anderson and Ferguson (1987), Rahman et al. (2009), Khan and Abbasi (1997a, 1997b, 1998, Khan (2005), Venkatasubramanian and Vaidhyanathan (1994), Venkatasubramanian and Preston (1996), Venkatasubramanian et al. (2000), Viswanathan et al. (2000), Zhao et al. (2009). An important extension of capabilities in some of these is the automated conversion of P&ID's in CAD formats to "intelligent drawings" which can be used in automated HAZOP, and the provision of guidance on risk reduction. ...
Hazard and operability analysis (HAZOP) has developed from a tentative approach to hazard identification for process plants in the early 1970s to an almost universally accepted approach today, and a central technique of safety engineering. Techniques for automated HAZOP analysis were developed in the 1970s, but still have not displaced expensive manual approaches. Reasons for this were investigated and conclusions are drawn. The author's actual experience in applying automated HAZOP techniques over a period of more than 30 years is revisited, including results from several full-scale validation studies and many industrial applications. Automated techniques, when combined with manual approaches, were found to provide significant improvements in HAZOP quality and a limited but valuable improvement in efficiency.
... Having developed the knowledge-base, they proposed the optHAZOP study procedure to increase efficiency by eliminating repetitive tasks. At the same year, in 1997, to enable HAZOP automation, TOP-HAZOP (Khan and Abbasi, 1997b) advanced in a systematic way with three structures (knowledge-base, inference engine, and user interface). TOPHAZOP generates deviations and contains rule-based trees linking to process specific attributes, via process parameters, and deviations to causes and consequences. ...
Hazard identification is the first and most crucial step in any risk assessment. Since the late 1960s it has been done in a systematic manner using hazard and operability studies (HAZOP) and failure mode and effect analysis (FMEA). In the area of process safety these methods have been successful in that they have gained global recognition. There still remain numerous and significant challenges when using these methodologies. These relate to the quality of human imagination in eliciting failure events and subsequent causal pathways, the breadth and depth of outcomes, application across operational modes, the repetitive nature of the methods and the substantial effort expended in performing this important step within risk management practice. The present article summarizes the attempts and actual successes that have been made over the last 30 years to deal with many of these challenges. It analyzes what should be done in the case of a full systems approach and describes promising developments in that direction. It shows two examples of how applying experience and historical data with Bayesian network, HAZOP and FMEA can help in addressing issues in operational risk management.
... There are two possible approaches: knowledgebased and model-based. Typical knowledge-based expert systems, i.e. systems using a knowledge base containing information about the failure mode, causes and consequences of various process units and/or pieces of equipment, are presented in publications of Venkatasubramanian et al. (1994), Khan et al. (1997), Srinivasan et al. (1997) and Kang et al. (1999). The knowledge-based approach has one significant disadvantage: in the age of constant development of technology and pushing the limits of process variables to extreme values, it is questionable, if the identification of all possible hazardous events is possible using only large databases of experience. ...
Hazard and operability (HAZOP) analysis is a highly disciplined process hazard analysis (PHA) technique based on the exploration of the effects of process variables deviations. Inconveniences of a conventional HAZOP study are its time-consuming character and high cost. The principal objective of this paper is to present a new methodology for hazard identification of a selected chemical production process. Model-based HAZOP study is a very robust tool for predicting a systems response to deviations from design or operation conditions. An approach based on the mathematical modelling of a process can help to identify sources of hazard that could be overlooked by conventional PHA techniques. A case study focused on the multiple steady states phenomenon in an ammonia synthesis reactor is presented. The process simulation was performed using the Aspen HYSYS v8.4 process modelling environment. Nonlinear behaviour of the investigated fixed-bed reactor system was confirmed by an accident in an industrial ammonia synthesis reactor. The analysed system exhibited the feed temperature and pressure dependence of various operation parameters. This fact indicates the presence of multiple steady states. From the safety analysis point of view, switching between steady states can lead to process hazards.
... All the above methods are discussed in detail in the relevant literature (Lawley, 1974;Sevcik, 1981;Khan. and Abassi, 1997;Kliem and Ludin, 1997;Hollnagel, 1999;Hammer and Price, 2001;Ringdahl, 2001;Cooper et al., 2004 andLoosemore et al., 2006). ...
The construction industry is plagued by occupational risky situations and poor working conditions. Risk Assessment for Occupational Safety (RAOS) is the first and key step to achieve adequate safety levels, particularly to support decision-making in safety programs.
Due to the lack, inadequate and imprecise data, the use of probabilistic existing OSRA models at constructions sites requires analysts to make harsh estimates based on their experience and perceptions. This is reflected in the analyst-to-analyst variability of results. Significant analyst-to-analyst variability might be perceived by engineers, foreman, workers and managers as indicate an inexact and immature analysis results not capable to providing accurate predictions of risk. Any decisions based on misleading results may lead to non-effective safety actions.
So, most construction safety efforts are applied informally under the premise that simply allocating more resources to safety management will improve safety on site. Moreover, there are many traditional methods to address RAOS, but few have been adapted and validated for use in the construction industry, thus producing poor results.
Construction needs OSRA models that can allow the use real data and information should all be achieved and treated in an easily and understandable manner to assure that safety practitioners understand the results entirely.
This work contributionis a qualitative fuzzy RAOS model, tailored for the construction industry, named QRAM (Qualitative Risk Assessment Model). QRAM is based on four dimensions: Safety Climate Adequacy, (work accidents) Severity Factors, (work accidents) Possibility Factors and Safety Barriers Effectiveness. For instance, safety climate traditional measurement methods need a lot of expertise to apply on construction. Some factors require significant expertise to evaluate, others require a lot of time. QRAM by the linguistic variables provides a practical way to estimate safety climate at construction sites.
Fuzzy Sets Theory presents a natural way of modelling the intrinsic vagueness and imprecision of everyday concepts by providing a very precise approach for dealing with uncertainty which grows out of the vagueness and complexity of human behaviour and enable to produce more realistic models that can reach better results. It proved be a good framework for modelling OSRA especially because it allows the use of ill-defined data and the use of empirical knowledge to deal with fuzzy (real) concepts.
The risk assessment is based on real data collected by observation of reality, interviews with workers, foreman and engineers and consultation of site documents (working procedures, reports of work accident investigation, etc.), avoiding the use of data obtained by statistical tecnhiques.
To rating each parameter it was defined qualitative evaluators - linguistic variables - which allow to perform a user-friendly knowledge elicitation.
QRAM was, firstly evaluated by “peer” review, with 12 safety experts from Brazil (2), Bulgaria (1), Greece (3), Turkey (3) and Portugal (3), and then, evaluated by comparing QRAM with other RAOS tecnhiques and methods.
The safety experts , concluded that: a) QRAM is a versatile tool for occupational safety risk assessment on construction sites; b) the specific checklists for knowledge elicitation are a good decision aid and, c) the use of linguistic variables is a better way to make the risk assessments process more objective and reliable.
... There is no limitation for the category of events, and they could be some type of component failure, human error, or energy-related event. However, the selection of these events, the links between the events and even the point of beginning and ending is arbitrary (Khan and Abbasi [3]). In order to reduce the subjectivity, more experts with different academic backgrounds are involved and the results need to be reviewed at least once, which obviously make the safety analysis time-consuming and mentally intensive. ...
Ensuring safety in railway signalling systems is always considered as significant
as a guarantee of the safe and efficient operation of the whole railway. In fact,
safety analysis of the signalling system with distributed computer technique is
becoming extraordinarily difficult, because of the frequent and complex
interaction between components and the various backup modes. The dominant
approaches are subjective, difficult to reuse and not well structured, thus leaving
the safety analysis process time-consuming and error-prone. This paper develops
a hierarchical methodology for safety analysis based on the failure propagation
model and state-transition model. Unlike traditional safety analyses, the
proposed approach demonstrates more accurate representation of practical failure
behaviour in a computer-based signalling system. Dynamic properties, system
structure and failures at the component level are separately modelled in different
layers, and connected with synthesis laws. The analysis can be easily refined as
the system design progresses and automatically produces safety-related
information to help the engineer in making design decisions. The preliminary
design of the Communication Based Train Control (CBTC) system for the
Yizhuang Line in Beijing is used to demonstrate this approach.
Keywords: signalling system, automatic safety analysis, model-based, FPTN.
1 Introduction
Railway systems have a very low tolerance for accidents, because of the
potentially large numbers of injuries and deaths, huge financial losses and even
worse social effects. Achieving a high degree of safety is one of the most
... A limitation of HazOp is that this approach is inherently qualitative (a "diagnostic tool") (Crawley et al., 2000). Moreover, there is the difficulty to estimate the time required for a complete HazOp study (Dunjó et al., 2010;Freeman and Mcnamara, 1992;Khan and Abbasi, 1997) as well as a lack of risk acceptability criteria and international standards, as discussed by Rouhiainen & Gunnerhed (2002) and Labovský et al. (2007). ...
Explosives are widely used in extraction of ores, melts and fuels and in the safe and economical demolition of structures. These applications demonstrate the value of explosives to society and the reason why they are manufactured worldwide despite the hazard of their preparation. Hence, this paper focuses on the manufactory of the military explosive Hexogen (also known as RDX). Thecharacteristics of the process are described by the analysis of a specify manufactory plant. The chosen analysis tool is the Hazard and Operability Study – HazOp. Historically, this methodology has been applied at chemical industries and is used in industrial process operability analysis. This study analyses seven critical nodes in the RDX manufacturing process, identifies several deviations, and causes and consequences. From these results, improvements in the units are suggested and actual conditions discussed. It is important to remark that this work is an initial approach to analysis of the manufacturing process of RDX using the HazOp methodology.
... A limitation of HazOp is that this approach is inherently qualitative (a "diagnostic tool") [26]. Moreover, there is the difficulty to estimate the time required for a complete HazOp study [19,27,28]. Another negative aspect of the traditional HazOp is the lack of risk acceptability levels and international standards, as discussed by Rouhiainen & Gunnerhed [29]. ...
Risk management can be defined as a systematic application of management policies, procedures and practices, which include identifying, analyzing, evaluating, monitoring and reviewing risk. Usually, the combined risk identification, analysis and evaluation are folded into what is known as risk assessment. As examples of risk assessment methods, one should quote the HazOp (Hazards and Operability Study) and the PHA (Preliminary Hazard analysis). PHA was originally proposed by the US military in the MIL-STD 882, in 1973, which undertook five reviews over time. Currently, the up-to-date version is the MIL-STD 882-E. The aim of this methodology is to be a semi-quantitative technique to assess risk using a risk matrix. On the other hand, the study of hazards and operability (HazOp) is a qualitative method developed to identify risks and operational problems through the deviations effects from design conditions in industrial process plants. It has been used effectively at any stage of the life of plants. Traditionally, a HazOp study and PHA are two sessions held separately, producing two databases. Considering an integrated approach, proposed by this work, the results combine upsides from PHA and HazOp and after determining deviations, through guidewords, the team determines its possible causes and consequences. Thus, it is possible to systematically identify the ways in which the equipment constituting the industrial process may fail or be improperly operated, which would lead to unwanted operating situations, as well as categorize risk in order to prioritize the measures. As a conclusion, this work provides a hybrid methodology between HazOp and PHA, by integrating HazOp and risk matrixes. The HazOp brings structure, procedure and its criteria (mainly the use of nodes, keywords and deviations), while the use of risk matrix brings to this hybrid technique the capability to prioritize risks/deviations, in other to provide information to a more detailed implementation plan.
This study aims to analyze the risk of transporting hazardous chemicals on sea-crossing bridges using a dynamic Bayesian network (DBN) model that incorporates vehicle dynamics. Firstly, the cause-consequence relationship analysis is constructed using the bow-tie (BT) model, which is then translated into a Bayesian network (BN) by mapping algorithms. Based on the dynamic model, the occurrence probabilities of rollover and sideslip under different wind speeds are calculated as conditional probabilities. Secondly, a DBN model that satisfies the Markov assumption and time invariance is established to realize short-term risk prediction. Finally, the proposed model is applied to a sea-crossing bridge in Zhejiang, and other node parameters are obtained by combining the monitoring data of the vehicle-bridge transportation system (VBTS) monitoring platform and expert experience. The results indicate that vehicle failure has the highest impact on VBTS, and unsafe driver behavior and road alignment are the most vulnerable root causes, which should receive more attention. Additionally, wind sensitivity to VBTS is significant and cannot be ignored. The proposed method can effectively address the risks and challenges posed by hazardous chemical transportation on sea-crossing bridges and provides valuable insights with practical application to enhance transportation safety.
Based on the typical physical effects of different accidents and considering the interaction of time and space, a dynamic evolution model of the domino effect was proposed in this study. The Monte Carlo method was used to deal with the uncertainty of the evolution path and capture the characteristics of the time evolution. The model considered mixed accident types and the synergistic effect of accidents and extended the application of the probit model. Risk assessment parameters such as evolution path, evolution time, tank accident probability, and domino evolution probability were obtained to evaluate the vulnerability of storage tanks exposed to such hazards. The proposed model was verified through a comparative case analysis, and the results showed that the model can not only capture the space–time dimension but also overcome the limitations of conventional analysis of high-level domino propagation. Different accident types, synergistic effects, and burning capacity of storage tanks have a significant impact on the domino propagation process.
To elucidate the dispersion and explosion characteristics of an unconfined detonable aerosol, experiments were performed with propylene oxide, JP-10 and petroleum ether. Unmanned air vehicles, a high-speed camera, infrared thermal imaging and a pressure-measurement system were used to record the experimental data. The results showed that the mean value of the fractal dimension of fuel aerosol edges decreased with increasing liquid viscosity. The initial diameter of the explosion cavity (the zone within the inner interface of the liquid shell) decreased with the increase of viscosity. An initiator charge of 500 g TNT was enough to induce a detonation in the aerosols (pure propylene oxide, 30% petroleum ether and 70% propylene oxide mixtures). After the aerosol was ignited, a secondary explosion phenomenon was observed and its characteristics were discussed. Furthermore, consequence analysis to determine the damage to humans and buildings were quantitatively assessed by using PROBIT equations. The relative-safety radii for humans and buildings were also obtained.
This chapter presents an overview of the advanced methods used for process risk assessment and management. A brief history of risk assessment and management is also provided from both the general and process industry perspectives. The driving forces behind research growth are also analyzed, highlighting the significant contributions of several regulatory bodies, industries, and individuals. The development and applications of a wide range of methodologies have been presented concisely, with their evolution, merits, and demerits.
In this article, the plantwide control of a novel process for diethyl oxalate production via two steps is investigated. The unique feature of this process is that there is a closed regeneration-coupling circulation. It results in that two steps should be matched properly and mass balance for overall reaction should be satisfied precisely. An effective control structure using a feedforward ratio with composition controller is determined.
Later, safety analysis for this process is investigated by the integration of dynamic simulation and HAZOP (hazard and operability analysis). In comparison with heuristic HAZOP, quantitative deviations can be introduced. Quantitative variation trends and change rates of important variables can be determined. Determining increase rate in temperature and pressure is significantly important, since response time as indirect indictor can be used to assess the possibility of risk. Finally, a general procedure based on simulation for design and safety analysis of chemical process is proposed.
In the article, the legal risk of the researcher in the case of a scientific experiment in the machining of magnesium alloys was determined. The use of magnesium alloys in industry and identification of the problems associated with machining were presented. The issues concerning legal liability in the experiment and provisions ensuring a greater scope of legal protection for the researcher were indicated and challenges in the machining of magnesium alloys were analyzed. Moreover, the method to assess legal risk in experiments was proposed and its application in the experiments was presented. The analysis confirmed the applicability of the proposed method to the analysis of the legal risk.
In recent years, the chemical process industry has witnessed increased process safety management challenges. One of the initial steps in process safety and risk management of any facility is hazard identification and analysis. Two types of factors: 1) technical (e.g., equipment malfunction), and 2) social (e.g., human and organizational factors) are important in analyzing hazards of a socio-technical process system as a whole. With the conventional process hazard analysis (PHA) methods, there is a tendency to overlook the potential impact of socio-technical systems on the health and sustainment of safeguards. This disregard leads to ignoring social factors, such as shift handover communication, downtime, operating and maintenance procedures, and more. This need calls for the development of a holistic and integrated systems framework for hazard analysis. This paper presents a novel hazards analysis approach that incorporates both technical and social factors within a single analysis method called Resilience-based Integrated Process Systems Hazard Analysis (RIPSHA). This approach is based on the following resilience aspects – ‘early detection’, ‘error tolerant design’, ‘plasticity’, and ‘recoverability’. This work establishes and presents a worksheet for analysis of hazards within process systems. The paper concludes with an example of a liquefied natural gas (LNG) process system to illustrate the key concepts of this integrated approach.
The vulnerability to an accident in a chemical process industry is not merely a function of the severity of a loss of confinement or the size of the area that can be affected by it. What constitutes the impact area is equally important. Vulnerability is a function of several variables—population density, quality of roads (to help disaster management), proximity to, and quality of, healthcare facilities, etc—besides an overall awareness of the risk and preparedness for the emergency. Additionally, factors such as time and climate which are not directly related to the composition of the impact area also determine it. In order to estimate the risk of an accident more precisely—so that strategies to prevent accidents or to cushion their impacts (when accidents occur) can be put in place accordingly—an index has been attempted which has the provision to factor in the vulnerability aspect. Given the fuzziness associated with the occurrence as well as the impact of any accident, this index is based on fuzzy logic.
One of the most dangerous consequences of an equipment failure in process industries resulting in a fire and/or explosion is the triggering off of the “domino effect” or “chain of accidents.” An accident in a unit may trigger an accident in another unit which, in turn, may lead to yet other accidents. To prevent such an occurance, it is imperative that hazardous units are kept safe distances away from each other. Of the types of accidents that can occur in chemical process industries, the boiling liquid expanding vapor explosion (BLEVE) is perhaps the most destructive of the forms of accidental explosions that can occur during the manufacture, storage, or transportation of chemicals in a pressure-liquefied state. The resulting blast wave, missiles, and fire or toxic release can cause great damage to life and property. There are several standards and codes which prescribe minimum safe distances to be maintained between equipment to prevent the domino effect from occurring. Of these the code prescribed by the National Fire Protection Agency (NFPA), USA, is among the ones most widely adopted for locating hazardous units. This paper evaluates the effectives of the safe distances prescribed by the NFPA 58 code in preventing a BLEVE in one vessel from causing other vessels and nearby structures to fail. The study reveals that the distances presented by NFPA are not sufficient to prevent the domino effect when the primary accident is a BLEVE.
The development and validation of a new software named chemical accident simulation tool (CAST) is presented. CAST enables development of scenarios of different types of accidental fires and explosions that can occur in chemical process industry (CPI). CAST is also capable of assessing the likely consequences of such accidents in terms of the area impacted and the types of impacts. The distinguishing features of CAST are (a) it incorporates a larger set of established models than handled by existing packages to simulate a wider variety of accidents in CPI; (b) it is developed with an integrated mapping tool to display damage zones around accident center; this makes the application useful in decision making; and (c) it calculates the results in a fast and reliable manner. Due to these attributes, CAST has increased efficiency, better understanding of the accident scenarios, and better communication of results. Validation of the software has been done with published results which shows that the codes for calculating the impacts from accidents are correct.
Accidents are now widely acknowledged to be a systems phenomenon. As part of a proactive approach to safety management, organisations use risk assessment methods to identify the hazards and associated risks that may lead to accidents. Although there is an extensive body of literature on the need for a systems thinking approach in accident analysis, little has been said regarding the theoretical underpinnings of risk assessment methods. The aim of this paper was to systematically review the risk assessment methods presented in the literature and evaluate the extent to which they are underpinned by a systems thinking approach. A total of 342 methods spanning a range of safety-critical domains were evaluated using Rasmussen’s tenets of accident causation. A key finding is that the majority of existing risk assessment methods are not consistent with Rasmussen’s model of accident causation (arguably the most popular model in safety science circles). Instead, the majority of risk assessment methods focus on risks at the so called sharp-end and largely view accidents as emerging from a linear, or chain-of-events process. This overlooks emergent risks at other levels of the system, including supervisory, managerial, regulatory and government levels. The findings therefore suggest that the majority of existing risk assessment methods may be inadequate for identifying hazards and analysing risks within complex sociotechnical systems. The implications for risk assessment practice are discussed.
On December 19, 2007, a powerful explosion and fire killed four employees and destroyed T2 Laboratories, Inc., a chemical manufacturer in Jacksonville, Florida. In the accident 32 people were injured, including 4 employees and 28 members of the public who were working in the surroundings. Debris was found up to one mile away, and the explosion damaged buildings within one quarter mile of the facility. After the accident, the question which arose was: could an even simplified risk analysis prevent such a tragedy? It is widely accepted that performing a detailed Quantitative Risk Analysis (QRA) is a complex and time consuming task because of all the steps which must be carried out: 1) hazards identification; 2) frequency estimation; 3) accident consequence evaluation; 4) individual and societal risk calculation.
Specifically, Hazard Identification (HI) and Frequency Estimation (FE) represent two fundamental activities since: 1) not identified hazards can remain hidden until the occurrence of the related accidents; 2) the probabilistically quantification of the hazardous plant states frequencies, e.g. through Fault Tree Analysis (FTA), helps to support decisions making on risk reduction. Particularly, since generating FTs is a time consuming task, the Recursive Operability Analysis (ROA) has been ideated. ROA, both in its classical and revised version (called Recursive Operability Analysis – Cause Consequence Diagrams, ROA-CCD), is based on a procedure which allows collecting plant perturbations data in a structured way.
The aim of this work is to apply both the classical and the new ROA-CCD analysis on the T2 Laboratories chemical plant (with particular reference to the reactor node) in order to identify all the possible top events and states of plant unavailability. In this way, it has been evidenced that even a simplified but reliable risk analysis could have been unearthed clearly all plant criticalities. Moreover, the results concerning the risk quantification have been critically analyzed showing that ROA-CCD achieves the same results, in terms of Minimal Cut Sets, of its classical version with a lower effort. This goal is fulfilled by avoiding the unnecessary subdivision of the plant into nodes prior to perform the analysis; in this way, considering only the process variables related to the “key piece of equipment” (in this case, the reactor), records in the ROA format are drastically reduced.
The chapter goes into detail of some new methods. First is the system-theoretic process analysis for scenario identification followed by the blended hazard identification (Hazid) method. Then, an overview is given of all trials thus far to automate hazard and operability study. Next, the principles of Bayesian data analysis are explained and the Bayesian network technique introduced. Because in risk analysis we have to deal with various types of uncertainty, this is given much attention. Fuzzy set approach is briefly explained. Examples are given of Bayesian network solutions of, for example, layers of protection cost-benefit. This chapter also shows how data of performance indicators can be used to measure effect on management effectiveness with, in turn, the state of workers and the relation with human error. It is further shown how Petri net and agent-based modeling can be applied in risk analysis. Finally, methods are discussed that can be used in resilience engineering.
Nowadays the application of decision support systems (DSSs) in process safety is more important than ever. The use of DSS for preventing domino effects is one of the diverse applications of these computer-automated toolkits. Different software packages were developed in recent years, each trying to manage domino risk by a specific approach. In this chapter, the definition, architecture, benefits and essential characteristics of DSS toolkits are described. The application, scope, approach, technical features, advantages, shortcomings and limitations of all the available computerized tools and software packages presented up to now for managing domino effect are then discussed and analyzed thoroughly. Finally, a framework for an integrated DSS to prevent domino effects based on all existing advancements and potential possibilities for improvement is introduced.
The combination of an automatic HAZOP analysis with a structural model was introduced to obtain a systematic procedure for hazard and mal-operations identification. There are three stages of the proposed procedure. The first stage was used to analyze the conventional hazard and mal-operations for each process unit, whereas the second stage extended the analysis to adjacent units. The interaction style was used to identify the cause-consequence relationships between upstream and downstream unit with the concepts of the non-local path and the dummy parameters. Therefore, a generic HAZOP library will be additional modified. The third stage created the templates for hazard and mal-operations identification for operating arbitrary units. This proposed HAZOP analysis was verified with conventional HAZOP of the defatted soy flour pilot plant with three scenarios. The analysis scheme fulfilled the library of the case study and discovered 18 new consequences for the first scenario, 10 new consequences for the second scenario. For the third scenario, the analysis specified on an arbitrary flash drum by applying three guide-words (more, less and no) and found 46 causes and 83 consequences. The proposed methodology, therefore, can simplify and reveal the guidance for hazards and mal-operations identification.
Chemical engineering systems have been widely used in industry fields such as petroleum, medicine and astronautics. The delivered liquid of chemical engineering system, especially used in astronautics field, is combustible, poisonous and exposable. For these kinds of chemical engineering systems, training with physical equipments not only increases cost, but also causes danger and pollution threats to operators and surroundings. In order to reduce danger and cost in physical chemical process training and testing, this paper proposed a simulation system for chemical process using distributed virtual reality. According to characters of an existing chemical engineering system, a data-driven simulation framework is proposed, and some related key technologies such as modeling and chemical process path calculation were discussed.
As is known to all, in chemical plants, safety is considered as a significant task, and it also plays an important role in the design process. For these reasons, in the early design phase, it is usual to carry out a complete safety analysis to ensure the demands of the plants. On the other hand, chemical processes are becoming more complex, and this makes modeling and simulation more difficult. Thus, the traditional modeling methods may not be as applicable as they once were. This paper introduces an agent-based approach to process hazard identification by simulation and reachability examinations of dangerous plant states.
It is impossible to eliminate all hazards in a plant, but for safety's sake all potential ones must be determined. Then we must establish the most important so as to know which to attack first. Here are ways to do this.
A new and elaborate software package MAXCRED (MAXimum CREDible accident analysis) has been used for generating accident scenarios and estimating damage potential for a typical industry. Four different scenarios have been generated for explosions, fires, as well as toxic releases. The damage they would cause has been estimated. The studies indicate that a confined vapour cloud explosion followed by fire would be the worst disaster scenario and would also have the highest probability of leading to 'cascading' or 'domino' effects.
The progressive concentration of production into large single-train units, and the increasing need to operate closer to risk situations requires refined methods for eliminating problems at the design stage. One method, called an ″operability study″ is based upon the supposition that most problems are missed because the system is complex rather than because of a lack of knowledge on the part of the design team. It can be used to examine preliminary process design flowsheets at the start of a project, or detailed piping and instrument diagrams at the final design phase. The other method, ″hazard analysis″ provides a full quantitative examination after a serious hazard has been identified. Examples of each of these methods is presented and discussed in detail.
Monsanto has developed an expert system useful for planning a HAZOP study. The expert system estimates the manhours and elapsed time required to complete a HAZOP study. The expert system also provides the user with help on defining the essential documentation set needed to perform the study as well as consultants (internal and external to Monsanto) who can aid in the study. This article presents the technical basis for the time estimate methods used in the expert system.
Many of the techniques introduced in recent years for the identification and assessment of hazards in process plants have the common feature that they deal with the propagation of faults through the plant. The modelling of fault propagation, its application to fault tree synthesis, a computer-based interactive facility and an illustrative example have been described in previous papers. This paper describes a similar, though not identical, method of modelling fault propagation for the purpose of hazard identification implemented on a computer-based interactive facility. The information produced is similar to that obtained from a hazard and operability study, though less complete. Consideration is also given to expert system enhancement of the method. An illustrative example is described in a further, complementary paper.
Quantitative Risk Analysis (QRA) is a tool that is being used increasingly in the chemical process industry (CPI) to help prevent rare but potentially catastrophic events. The QRA methodology includes: 1.(1) establishing QRA priorities,2.(2) identifying accident scenarios,3.(3) quantifying the frequency of each scenario,4.(4) quantifying the consequences of each scenario and5.(5) quantifying total risk. A wide variety of factors contributed to the rather large uncertainty of QRA results.The results of a QRA can be expressed in terms of absolute risk which can be compared to established levels of unacceptability. The result can also be expressed in terms of relative risk, indicating the effect on risk of various design options. However, the most important result of QRA is the operational insights revealed to the analysts which lead to risk reduction and understanding of the sources of residual risk. This paper describes the QRA method as it is used in the CPI.
The Chemical Process Industry is been forced by the society to improve its standards in safety, environmental effects and product quality. One aproach used to address all these aspects in traditional process industries is the HAZOP study (HAzard and OPerability study). But, the application of this technique to a detailed chemical plant design is a complex and time consuming task.These two aspects and the availability of proved technology to develop computational systems able to manage qualitative knowledge, have motivated the construction of SERO, a knowledge-based system for HAZOP studies. The objective of this project is to generate a system aimed at enhancing the knowledge and creative power of the expert team involved in a HAZOP study.One of the main aspects of SERO, that is presented in this paper, is its knowledge representation structure, which has been developed to encode the different kinds of knowledge used in a HAZOP study. The knowledge representation structure of SERO has been designed and constructed using the object oriented paradigm.
A set of procedures and corresponding methodologies for probabilistic safety assessment (PSA) in chemical installations is presented. State-of-the-art methodology for PSA in nuclear power plants is tested for suitability and applicability to chemical installations and applied on a refrigerated ammonia storage facility. The procedural steps comprise hazard identification, accident sequence modelling, data acquisition and parameter estimation, accident sequence quantification, hazardous substance release categories assessment, consequence assessment and integration of results. The results of the application indicate that the methodology applied is adequate from the procedural and completeness point of view and that no major aspect of PSA of a chemical installation is overlooked. A need for integrated computerized tools has, however, been identified.
Probabilistic Risk Assessment (PRA) is a method of quantifying the frequency of occurrence and magnitude of the consequences of accidents in systems that contain hazardous materials such as toxic, flammable or explosive chemicals. The frequency and magnitude of the consequences are the basic elements in the definition of risk, often simply expressed as the product of frequency and magnitude, summed over all accident sequences. PRA is a mature technique that has been used to estimate risk for a number of industrial facilities: for example, the Canvey Island Petrochemical complex; the Port of Rotterdam; the Reactor Safety Study, the first study to put the risks associated with nuclear power into perspective; and the transportation of chlorine. PRA has been developed to a greater level of sophistication in the nuclear industry than in the chemical industry. In the nuclear area, its usefulness has been demonstrated by increased plant safety, engineering insights, and cost-saving recommendations. Data and methods have been developed to increase the level of realism of the treatment of operator actions in PRA studies. It can be stated generally that the same methods can be applied with equal success in the chemical industry. However, there are pitfalls into which the unwary nuclear-oriented PRA analyst may stumble if he does not bear in mind that there are significant differences between nuclear plants and chemical plants.
Growing concern about the risk of major chemical accidents in the U.S. has led both government and industry to find new ways to identify and evaluate potential hazards. Among the most promising (and misunderstood) approaches is a collection of techniques called quantitative risk assessment (QRA). Adapted primarily from probabilistic risk assessment approaches developed in other industries, the use of QRA is spreading rapidly through the U.S. chemical industry. Of equal importance, legislators and regulatory agencies at the state and federal level are making QRA an integral part of their proposals for mandatory accident prevention measures.
This paper summarizes a workshop on QRA that was presented at the International Conference and Workshop on Process Safety Management, sponsored by the AIChE Center for Chemical Process Safety, in Toronto during May 1990. It is based on A Manager's Guide to QRA [1] developed for the Chemical Manufacturers Association. This paper gives an overview of the Guide and discusses important implications concerning the increasing acceptance of QRA as a chemical regulatory tool.
Of all the analytical tools available to the process safety professional, perhaps the most critical are those used to identify and analyze process hazards. Such tools have been collectively referred to as “Hazard Evaluation Procedures” by the Center for Chemical Process Safety (CCPS) and as techniques for “Process Hazard Analysis” (PHA) by the Occupational, Safety and Health Administration (OSHA).
One of the best known PHA tools, the Hazard and Operability or HAZOP study, emerged over two decades ago in ICI, U.K., and its use has since spread over six continents. In 1979, ARCO Chemical piloted its first HAZOP and since then, HAZOPs have become the backbone of the company's Process Hazards Review procedure.
Repeated use of the HAZOP technique since 1979 has resulted in an affirmation that to be “successful”, much more was needed than simply executing the HAZOP technique. Success is dependent upon the preparation and planning effort that precedes the HAZOP, and the follow-up activity that ensures implementation of study findings. Unlike the study technique, little information was available in 1979 on how to design the framework, or management system, that was needed to support the use of this tool.
The purpose of this paper is shift focus from executing the HAZOP technique to that framework, by presenting insights that have accumulated from using the technique in ARCO Chemical, especially during the period 1979 through 1986. These were the formative years, during which the company's advancement on the learning curve was most noticeable. These were the years that convinced the company that successful HAZOP studies do not just happen; success comes from building the right management system. Success must be defined and assured at each step in a Process Hazards Review procedure, of which executing the HAZOP technique is only one.
The application of fault propagation modelling to hazard identification and its implementation on a computer-based interactive facility are described in a companion paper. This paper describes the use of the facility for hazard identification in a water separator system. The object of the work was to produce information similar to that obtained in a hazard and operability study.
Hazard and operability (HAZOP) analysis is the study of systematically identifying every conceivable abnormal process deviation, its abnormal causes and adverse hazardous consequences in a chemical plant. HAZOP analysis is a difficult, time-consuming, and labor-intensive activity. A automated HAZOP system can reduce the time and effort involved in a HAZOP review, make the review more thorough and detailed, and minimize or eliminate human errors. Towards that goal, a knowledge-based system, called HAZOPExpert, has been proposed in this article. In this approach, HAZOP knowledge is divided into process-specific and processindependent components in a model-based manner. The framework allows for these two components to interact during the analysis to address the process-specific aspects of HAZOP analysis while maintaining the generality of the system. Process-general knowledge is represented as HAZOP models that are developed in a process-independent manner and are applicable to a wide variety of process flowsheets. The important features of HAZOPExpert and its performance on an industrial case study are described.
A knowledge-based expert system for hazard and operability study (HAZOP) is developed. HAZOP study is regarded as one of the
most systematic and logical qualitative hazard identification methodologies. But, it requires a multidisciplinary team and
is very time-consuming and repetitious task in nature. By developing an computer-aided automation system, these drawbacks
of HAZOP study can be overcome. Considerable manpower and time can be reduced and even past experiences of engineers and existing
checklists can be stored for future use in the form of knowledge base. The developed knowledge-based HAZOP expert system has
a frame-based knowledge structure for equipment failures and process properties, and rule networks for consequence reasoning
which uses both forward and backward chaining. The system is open-ended and modular in structure to make it easy to implement
wide process knowledge for future expansion. LPG storage and fractionation process has taken as example to test the applicability
of the developed system as an automated HAZOP study system. The result shows that savings more than 50% of the required manpower
and time for HAZOP studies can be achieved, and the system is very efficient and reliable, too.
Operability study is a systematic technique for identifying hazards or operability problems throughout an entire facility. In this paper, we have proposed an approach using knowledge engineering techniques to the automated operability study. The computer-aided operability study system consists of the plant-specific knowledge-base, the generic knowledge-base and the inference engine. Causal relationships between input and output variable deviations for components are modeled using decision tables. Decision tables for components are developed by the user and stored in a generic knowledge-base in computers. The plant structure (piping and instrumentation diagram) and reaction types are inputted to the plant-specific knowledge-base in computers. Each process variable of equipment is examined in sequence by searching the generic knowledge-base, and operability study is generated resulting from the search. We demonstrate via the Solvey process how the computer-aided operability study can identify hazards, and substantiate the usefulness of the method. Copyright © 1996 Elsevier Science Ltd Printed in Great Britain. All rights reserved.
Qualitative hazard assessment is part of the detailed risk analysis of chemical process industries and a hazard and operability (HAZOP) study is the best technique to carry out this step. It is a systematic study conducted by a team of experts of different disciplines to identify and assess hazards using brainstorming discussion of deviation in operational parameters from normal/standard conditions. This study needs high levels of expertise and substantial time commitments. The various steps involved in any typical HAZOP (application of deviation, cause-finding, and consequence analysis of each and every line and equipment) need a sustained high level of mental performance and alertness for a long span of time, but the repetitious nature of these steps inevitably generates a feeling of drudgery and mental fatigue, even exhaustion. This may not only reduce the effectiveness of HAZOP, but even render it incomplete or erroneous.This paper is devoted to a discussion about the factors that have direct influence on the efficiency, effectiveness and reliability of such studies. It also suggests an optimal approach to HAZOP study procedures (optHAZOP) based on the utilization of an already developed information base. The optHAZOP technique reduces the mental execution load of experts by a half, and thus provides more time to study typical hazardous units and conceptualize better control strategies. This technique takes around 45% less time than that of the conventional HAZOP study procedure (estimated using CPM networking and time analysis of different steps of study) with better efficiency and effectiveness.
In today's process industry environment, it is becoming more and more important for companies to evaluate the risks associated with their plants. However, many risk evaluation methods of varying degrees of complexity and cost exist. Choosing the right method to provide the information management needs to answer a company's risk questions is often difficult. This paper provides an overview of three risk evaluation methods: one (HAZOP analysis) is a qualitative technique, the second (Facility Risk Review) blends together aspects of qualitative and quantitative risk assessment techniques, and the third (Quantitative Risk Analysis) is a quantitative technique. Example risk evaluations using each technique are provided to help the reader understand the capabilities and typical results obtained with each method.
Safety and risk analyses have often been criticized as incomplete and inaccurate. This criticism, however, lacks a sound basis, since there has been little scientific evaluation of the methods developed for safety and risk analysis. The aim of this paper is to present a proposal for establishing measures—reliability, validity, and coverage—to be used in the evaluation of the scientific quality of the hazard identification and accident modeling phases in safety and risk analysis. The paper also presents four main principles for the evaluation of the scientific quality, and a theoretical framework to be used in evaluation. The framework is illustrated with practical examples taken from the chemical industry.
The key elements that make the hazards and operability (HAZOP)
technique effective for identifying chemical process hazards are
outlined. Six categories of problems that can sometimes reduce the
effectiveness of HAZOP and even prevent it from discovering some major
hazards are explained. Several examples are included to show how lack of
experience, failure to communicate, management shortcomings, complacency
and poor loss-prevention practices, a shortage of technical information,
and other limitations, each contribute to the problem. Practical
solutions are recommended for countering the difficulties and for making
the HAZOP a more effective risk-management tool
The application of qualitative and quantitative hazards/risk
analysis methods is discussed. Two examples of both qualitative and
quantitative methods are discussed. The relative advantages of each, as
well as relative manpower requirements for their application, are
examined. The two qualitative analysis examples are: (1) hazards and
operability (HAZOP) analysis, based on the conceptual design analysis of
an offshore gas-processing platform, and (2) a qualitative fault-tree
analysis based on a design review of a land-based oil-processing
facility. The two quantitative analysis examples are: (1) the use of
event sequence diagrams for the risk analysis of a batch
chemical-operation plant, and (2) an event-tree analysis relative to the
consequences of the loss of electric power for the same batch plant. In
these examples, design operations and maintenance-safety enhancements
that have been implemented are identified
Experience with the application of HAZOP to computer based systems Leone, H., A knowledge-based system for HAZOP studies. The knowledge representation structure
- J A Mcdermid
- M Nicholsen
- D J Pumfrey
- P Fenelon
McDermid, J. A., Nicholsen, M., Pumfrey, D. J. and Fenelon, P., Experience with the application of HAZOP to computer based systems. Department of Computer Science, University of York, Heslington, 1996. Leone, H., A knowledge-based system for HAZOP studies. The knowledge representation structure. Computer and Chemical Engineering, 1996, 20(A), S369-S374.
Building an HAZOP studies to reproduce knowledge-based systems
- J I Tait
Tait, J. I., Building an HAZOP studies to reproduce knowledge-based systems. IEEE Colloquium, Stevenage, UK, 1995. Stevens, G. C. and Humphreys, A. M., Calibrating HAZOP Stud-ies. Arthur D. Little Ltd, Cambridge, 1996.