Selection of failure frequency and its impact on risk assessment – A case study from plot plan optimisation

Facility Siting is an important phase of project development. A critical stage is plot plan optimisation, where significant potential hazards are eliminated due to equipment spacing. In addition to ensuring appropriate compliance with minimum spacing requirements, occupied building studies to achieve compliance with the requirements of API 752 and API 753 could also be undertaken to optimise safety outcomes. The studies are done in three stages, where the first stage is hazard identification, second stage is consequence assessment and the third stage is risk assessment. Third stage assessments are only carried, if the consequence based siting recommendations are not practical to implement.This paper presents the challenges in estimating risk due to process hazards with a focus on selecting right event likelihood data. A comparison is presented on the variation in predicted risk levels based on equipment failure rates and leak frequencies.Case study of a plot plan optimisation study is undertaken with DNVGL Phast Risk and the variation in risk levels up to two orders of magnitude are recorded. Challenges such as adaption of data for local conditions, consistent definitions of failure, sample size of data, applicability of data play a significant role in identifying and correctly quantifying the risk levels. Such challenges and its impact on risk quantification are presented in this paper as well as its impact on facility siting.     

Learning from the application of nuclear probabilistic safety assessment to the chemical industry

This paper introduces the new approach of risk analysis established by the French Ministry of the Environment and develops the benefits of applying nuclear probabilistic safety assessment approaches to the chemical industry.In the aftermath of the AZF disaster in Toulouse on 21 September 2001, a new law was proposed by the French government asking for the investigation of all representative scenarios and the assessment of the probability of the resulting dangerous phenomena to demonstrate an acceptable level of safety. Therefore, any accident is investigated from a global point of view, according to its gravity and its probability.In 2000, the French Ministry of the Environment asked the Institute for Radiological Protection and Nuclear Safety (IRSN), and in particular its Systems and Risk Protection Assessment (SESPRI) and its Industrial Risks, Fire and Containment Assessment and Study (SERIC) departments, to conduct a Probabilistic Safety Assessment (PSA) study of an LPG distribution facility, specially for the BLEVE scenario. This study has showed the power of PSA for defining and prioritizing actions to be carried out to improve safety of facilities; however, it requires credible data for reliability and failure of the equipment, not available in generic failure databases.Since 2007, IRSN has taken several initiatives in collaboration with operators in order to provide more precise and representative failure rates for main safety equipment, ready to use in future PSA relative to LPG plants.     

Important meteorological data for use in risk assessment

This paper presents a methodology for the calculation of atmospheric stability classes in correlation with wind velocities for six sites of the Greek territory, namely Ellinikon (Athens), Elefsis, Megara, Heraklion, Chania and Patras, based on real data obtained from meteorological observations in these sites and on computations related with their geographic position. In addition to that, a comparison is presented of the atmospheric stability classes produced with online measurements for the Ellinikon (Athens) site with significant coincidence in the results.

These calculated values of the meteorological parameters (particularly of atmospheric stability) are most appropriate for uncertainty calculations in quantified risk assessments (QRAs) of hazardous installations sited in the above-mentioned areas, especially when risk and safety-related decisions need to be taken. Consequent results obtained with these parameters are more realistic compared to the “classical” assumption of D5/F2, which leads to significant diversification in the estimation of risk.     

Uncertainties in QRA: Analysis of losses of containment from piping and implications on risk prevention and mitigation

Quantitative Risk Assessment (QRA) is commonly used in the chemical industry to support decision-making. Common practices are based on standard methods, such as fault tree, event tree, etc.; in this frame, risk is a function of frequency of events (probability) and associated consequences (negative outcomes), but relevant uncertainties often are not properly taken into account in the derived results. This paper presents the application of an extended risk analysis of loss of containments for a case-study with the following aims: firstly, the uncertainties related to the results of the analysis, which derive from assumption in the application of the standard models, are qualitatively assessed; secondly the application allows evaluating the impact of the uncertainties on the trustworthiness of the results and, finally, commenting about their use in the risk prevention and mitigation.     

危险评价中的数据环境

本文通过分析危险评价的数据来源、数据的准确程度和危险评价模型，论述了数据环境与危险评价的关系，指出了数据的不确切必然会影响到危险评价质量，但应用数据进行危险评价是完全必要的。关键是如何提高数据的精确程度和模型的真实程度，使评价结果更趋准确、可靠。     

Influence of new generic frequencies on the QRA calculations for land use planning purposes in Walloon region (Belgium)

In Europe, the article 12 of the “Seveso” Directive focuses on land use planning (LUP) around major hazard plants and imposes to keep a sufficient distance between a major hazard plant and populated areas. In Belgium, the LUP is treated at the regional level. The regional authority defines the policy and manages the LUP according to the quantified risk. The quantified external risk, around each Seveso company in the Walloon Region, is assessed by a unique technical expert, the Faculté Polytechnique de Mons, by means of a full probabilistic approach (QRA). This QRA methodology uses accident generic frequencies published by the Flemish Region (Aminal, 2004). In 2009-2010, the quantification of the external risk of the 90 walloon Seveso plants will be completed, based on this set of generic frequencies. However, the Flemish Region recently published a new set of generic frequencies (LNE, 2009), which, in some cases, are quite different of the previous ones for some equipment. This paper discusses the influence of the new frequency data on the quantified risk. An overview of the changes induced by the new set of data will be presented, as well as their impact on the already defined "consultation zones" in which decisions are made concerning the compatibility of the land use and the intensity of risk.     

Past,present and future of Quantitative Risk Assessment (QRA) and the incentive it obtained from Land-Use Planning (LUP)

This paper tells the story about the development of Quantitative Risk Assessment, how it was conceptualized in the early 1970s in the nuclear industry, how it was employed within the chemical industry soon after, and what its status is today. The different purposes of QRA are explained, and we elaborate on one of the purposes, that is, Land-Use Planning. The role of Professor Ben Ale, as a process safety pioneer, is discussed throughout the history. We finally provide some on-going state-of-the-art research and projects to further improve QRA approaches, and we sketch the future of QRA and its relation with LUP.     

On the development of a new hybrid risk assessment process using occupational accidents’ data: Application on the Greek Public Electric Power Provider

The occupational accidents have a major impact upon human integrity and also bring about high costs for the social health and insurance system of a country. In addition, risk analysis is an essential process for the safety policy of a company, having as main aim the effacement of any potential of damage in a productive procedure, while the quantified risk evaluation is the most crucial part of the whole procedure of assessing hazards in the work. The main goal of this study is double: a) the development and presentation of a new hybrid risk assessment process (HRAP) and b) the application of HRAP in the Greek Public Power Corporation (PPC) (the unique electric power provider and the largest industry in Greece), by using occupational accidents that have been recorded, during the 12-year period of 1993-2004. The new process consists of four distinct phases a) the hazard sources’ identification phase, b) the risk consideration phase, c) the risk-evaluation phase, and d) the phase of the risk assessment and safety-related decision making. The results show that in some cases the risk value has been calculated in PPC to be higher than 500 (in the risk rating of 0-1000), which imposes the taking of suppressive measures for abolishing the danger source, while the fatal accident frequency rate (per 10⁸ man-hrs) is FAFR ≅ 2.4.     

Optimizing the design of storage facilities through the application of ISD and QRA

Four strategies can be used to achieve safety in chemical processes: inherent, passive, active and procedural. However, the strategy that offers the best results is the inherent safety approach, especially if it is applied during the initial stages of a project. Inherently Safer Design (ISD) permanently eliminates or reduces hazards, and thus avoids or diminishes the consequences of incidents. ISD can be applied using four strategies: substitution, minimization, moderation and simplification. In this paper, we propose a methodology that combines ISD strategies with Quantitative Risk Assessment (QRA) to optimize the design of storage installations. As 17% of major accidents in the chemical industry occur during the storage process and cause significant losses, it is essential to improve safety in such installations. The proposed method applies QRA to estimate the risk associated with a specific design. The design can then be compared to others to determine which is inherently safer. The risk analysis may incorporate complex phenomena such as the domino effect and possible impacts on vulnerable material and human elements. The methodology was applied to the San Juanico tragedy that occurred in Mexico in 1984.     

作业条件危险评价方法的修正及在吉林油田的应用

对隐患的评价分级是治理的重要依据 ,作业条件危险评价方法是常用的一种危险评价方法。笔者认为 ,这种方法中的L项过于强调生产系统自身的客观不利因素 ,对管理行为外界主观因素没有考虑 ,恰恰就是这些因素可以在一定程度上消减客观不利因素。因此 ,通过对L项的修正 ,客观地评价危险的等级 ,从而降低了安全投入 ,提高了治理措施的经济性。     

Methodology for the quantification of toxic dispersions originated in warehouse fires and its application to the QRA in Catalonia (Spain)

A tool for the quantification of the consequences of toxic dispersions coming from fires in warehouses has been developed. This tool is expected to be applied in the framework of the risk assessment in Catalonia, specifically in the Quantitative Risk Assessment. The present study is based on the criteria gathered in the technical guide BEVI 3.2 and the methodology CPR-15 used in the Netherlands. Hence, the approach performed accepts the main body of the foresaid methodology but implements a different and free source dispersion model, a modified Gaussian model that takes into account the warehouse effect. In the work conducted, a historical analysis of accidents involving fire in warehouses has been performed in order to justify the importance of assessing their potential toxic dispersions. Furthermore, the tool has been tested in different case studies providing results that have been compared with other methodologies, observing similar results that can be useful for the stakeholders and decision makers in the framework of the risk assessment.     

Modeling and application of risk assessment considering veto factors using fuzzy Petri nets

Risk assessment is important for plant safety, and fuzzy set theory is useful for such assessment because many risk factors have fuzzy characteristics. In this study, veto factors for risk assessment are taken into account. Weighted fuzzy Petri nets (WFPN) with inhibitor arcs are proposed to model relationships between risk factors and establish the risk assessment structure considering veto factors. Definitions of WFPNs as well as the enabling rule and execution rule are provided. The modeling approach for the assessment combining normal factors with veto items is discussed. The proposed fuzzy risk assessment approach is illustrated by an example of the assessment of production installations and process technology of plants that deal with hazardous chemicals. Veto factors and non-veto factors are presented and the assessment structure based on WFPNs is established. Using the factor data of a plant, an assessment value is obtained through the operation of WFPNs and the verification of the approach is discussed.     

I-Risk: development of an integrated technical and management risk methodology for chemical installations

This paper presents an integrated quantitative risk assessment method for hazardous installations, taking into account management as well as technical design and producing risk level measures. The key components of the I-Risk methodology are the technical model, the management model and their interface. The technical model consists of developing a master logic diagram (MLD) delineating the major immediate causes of loss of containment (LOC) and associated quantitative models for assessing their frequency. The management model consists of the tasks, which must be carried out systematically in the primary business functions (such as operations, emergency operations, maintenance and modifications). A management audit quantifies the quality of these management tasks. The management–technical interface modifies certain parameters of the technical model on the basis of the quality of the safety management system of the specific installation. The methodology is exemplified through its application to the risk assessment of an ammonia storage facility. A detailed technical model simulating the response of the system to various initiating events is developed along with a detailed management model simulating the influence of the plant-specific management and organisational practices. The overall effect is quantified through the frequency of release of ammonia as a result of a loss of containment in a storage tank and in a pipeline.     

A comprehensive approach to API RP 752 and 753 building siting studies

Facility siting studies are an important part of process safety, and are required for facilities that fall under OSHA’s PSM program. Facility siting is frequently interpreted as performing a building siting study which adheres to the guidance given in API RP 752. Building siting may also consider siting of temporary or portable buildings based on the guidance in API RP 753. While both API RP 752 and API RP 753 provide a framework and some guidance for performing building siting studies, they do not provide detailed methodologies or provide guidance on performing a detailed analysis. As a result many building siting studies are inconsistent in their overall approach, or in the way they address hazards. Due to the recent scrutiny applied to building siting studies, more attention has been given to provide evaluations which correctly describe the range of hazards that may affect an occupied building at a petrochemical facility. This paper outlines a comprehensive methodology for performing building siting studies at such facilities. The methodology addresses the applicable hazards and the available tools by which the potential impacts to building occupants can be evaluated.     

Technical modeling in integrated risk assessment of chemical installations

This paper presents the technical model of an Integrated Quantitative Risk Assessment method, taking into account management as well as technical design and producing risk level measures. The basic steps of the technical model consist in developing a Master Logic Diagram (MLD) delineating the major immediate causes of Loss of Containment and associated quantitative models for assessing their frequency. Appropriate management models quantify the parameters of the technical model on the basis of the safety management system of the installation. The methodology is exemplified through its application on the risk assessment of a LPG scrubbing tower of an oil refinery. A detailed technical model simulating the response of the system to various initiating events is developed, along with a detailed model simulating the influence of the plant-specific management and organizational practices. The overall effect is quantified through the frequency of release of LPG as a result of a Loss of Containment in scrubbing towers of the refinery.     

Joint applicability test of software for laboratory assessment and risk analysis

Most of the available risk management methods are not directly applicable to academic research laboratories. One solution to systematically perform risk analyses in this environment is the Laboratory Assessment and Risk Analysis (LARA) method. This method was developed to allow untrained personnel to identify of possible risks and rank them according to their importance. The purpose of this study was to find out, if this method can be used as a holistic risk management technique in different environments, and which are the differences when comparing the results to other, well established risk analysis techniques. The risk analyses were performed at two European universities and for various procedures. The results show, that the LARA procedure is more easily performable than the other methods and gives comparably adequate results. Being applicable by non-experts, this holistic risk analysis method for research laboratories can help to reduce the accident rate in the academic environment.     

用于工业机器设计的安全性分析模式及方法研究

工业机器也属职业事故的重要危险源之一。在其设计时 ,有效地进行安全性分析是消除和控制工业机器中存在的固有危险的最佳途径。为此 ,推荐了一种用于工业机器的安全分析模式 ;并对已有的安全分析方法进行了重点选择 ,将供设计人员使用的安全分析方法从百余种减少到 11种 ;还对这些方法进行了分类 ,可供设计人员在设计工业机器时 ,较方便地选择和系统地应用。     

保险对企业安全监督管理之作用

通过开展适合于保险与安全监管工作的风险评估体系的研究 ,充分发挥保险在安全监管工作中的作用 ,从而为降低职工、企业乃至全社会的风险水平 ,为经济的可持续发展和社会稳定提供必要的保证条件。     

Design for safety in Safecharts with risk ordering of states

Safecharts is a variant of Statecharts intended exclusively for safety critical systems design. With two separate representations for functional and safety requirements, Safecharts brings the distinctions and dependencies between them into sharper focus, helping both designers and auditors alike in modelling and reviewing safety features. Safecharts incorporates ways to represent equipment failures and failure handling mechanisms and uses a safety-oriented classification of transitions and a safety-oriented scheme for resolving any unpredictable non-deterministic pattern of behaviour. It achieves these through an explicit representation of risks posed by hazardous states by means of an ordering of states and a concept called risk band. Recognising the possibility of gaps and inaccuracies in safety analysis, Safecharts do not permit transitions between states with unknown relative risk levels. However, in order to limit the number of transitions excluded in this manner, Safecharts provides a default interpretation for relative risk levels between states not covered by the risk ordering relation, requiring the designer to clarify the risk levels in the event of a disagreement and thus improving the risk assessment process.     

Technical,human, and organizational factors affecting failures of firefighting systems (FSs) of atmospheric storage tanks: Providing a risk assessment approach using Fuzzy Bayesian Network (FBN) and content validity indicators

Most risk assessment methods have problems such as uncertainty, static structure, and lack of validation. Also, in most of these studies, less attention has been paid to human, managerial, and organizational issues. Therefore, this study proposes a risk assessment method based on the Fuzzy Bayesian Network (FBN) to prevent failure of firefighting systems (FFSs) in the atmospheric Storage Tanks of a Petrochemical Industry. The first stage of the study is the development of a fault tree (FT) and investigation of basic events (BEs). In this study, content validity indices and brainstorming technique were used to validate the FT structure and reduce the uncertainties of Completeness, Modeling, and Parameter. After determining the probability of basic events (BEs) by the expert team opinions and fuzzy logic, events were transmitted to the Bayesian Network (BN) and then analyzed with deductive and inductive reasoning, followed by sensitivity analysis in the GeNIe software. Finally, results of a case study in the Atmospheric Storage Tanks of the Methanol Floating Roof of a Petrochemical Industry showed that FBN simulation and FT validation could provide a practical way to determine FFSs probabilities, identify impactful events, and reduce the above uncertainties. Also, taking account of hidden factors of events, such as organizational and managerial factors, can help managers to prevent FFSs in tanks.