Safety analysis and risk assessment of a Micro-GtL Plant

Laboratory hydrogen generators, medical oxygen, and micro-breweries are examples of modular and micro technologies that are commercial successes. Researchers, patients, and unskilled workers operate these facilities but more complex processes require highly qualified personnel to ensure they operate safely. Modular-micro processes in isolated locations meet economic objectives when operated remotely thereby minimizing labor costs. Mitigating the risk requires a comprehensive hazards analysis with advanced control systems particularly for explosive and toxic compounds. Here, we propose a method called Failure Mode Risk Decision (FMRD) to review the inherent hazards of a micro-refinery unit (MRU) that converts flared and wasted natural gas to long chain hydrocarbons. This approach combines the Process Flow Failure Mode (PFFM) methodology as a systematic and reliable technique with a novel numerical risk assessment to improve the analytical evaluation of hazardous conditions. The objective is to combine causes and consequences in a single metric, where scaled probability of evident causes and severity of consequences are used to derive a risk level measure. With the proposed metric, the magnitude of a potential hazard is directly correlated with the risk level. This mechanism identifies extra risk scenarios compared to the classical hazard analysis method and provides a straightforward comprehensive numerical assessment to represent the inherent and residual risks to facilitate justifying the hazardous scenarios. Accordingly, we design a safety loop and supply all the required facilities to remove the potential risks at the process plant. Not only the proposed methodology clarifies the risks of the MRU presented in this study, but can be extended to review the hazards of other chemical process plants.     

基于Fuzzy模型的职业病危害综合风险评估方法研究

为有效评估作业场所职业病危害的风险大小,研究职业病危害综合风险评估方法。在综合考虑作业场所职业病危害的固有危害特征、接触特征、防护特征和健康影响特征等风险影响因素的基础上,采用层次分析和专家咨询法筛选和建立了职业病危害综合风险评价指标体系,研究制定了各评价指标的分级评价准则,利用模糊数学理论,构建了基于Fuzzy模型的职业病危害综合风险评价模型。该方法可以对职业病危害的综合风险进行评估,并能够确定风险控制的优先权,避免了传统单一指标评价的局限性,对职业病危害评价工作具有一定借鉴意义。     

Safety study of an LNG regasification plant using an FMECA and HAZOP integrated methodology

A safety analysis was performed to determine possible accidental events in the storage system used in the liquefied natural gas regasification plant using the integrated application of failure modes, effects and criticality analysis (FMECA) and hazard and operability analysis (HAZOP) methodologies. The goal of the FMECA technique is the estimation of component failure modes and their major effects, whereas HAZOP is a structured and systematic technique that provides an identification of the hazards and the operability problems using logical sequences of cause-deviation-consequence of process parameters. The proposed FMECA and HAZOP integrated analysis (FHIA) has been designed as a tool for the development of specific criteria for reliability and risk data organisation and to gain more recommendations than those typically provided by the application of a single methodology. This approach has been applied to the risk analysis of the LNG storage systems under construction in Porto Empedocle, Italy. The results showed that FHIA is a useful technique to better and more consistently identify the potential sources of human errors, causal factors in faults, multiple or common cause failures and correlation of cause-consequence of hazards during the various steps of the process.     

Risk assessment of rare events

Rare events often result in large impacts and are hard to predict. Risk analysis of such events is a challenging task because there are few directly relevant data to form a basis for probabilistic risk assessment. Due to the scarcity of data, the probability estimation of a rare event often uses precursor data. Precursor-based methods have been widely used in probability estimation of rare events. However, few attempts have been made to estimate consequences of rare events using their precursors. This paper proposes a holistic precursor-based risk assessment framework for rare events. The Hierarchical Bayesian Approach (HBA) using hyper-priors to represent prior parameters is applied to probability estimation in the proposed framework. Accident precursor data are utilized from an information theory perspective to seek the most informative precursor upon which the consequence of a rare event is estimated. Combining the estimated probability and consequence gives a reasonable assessment of risk. The assessed risk is updated as new information becomes available to produce a dynamic risk profile. The applicability of the methodology is tested through a case study of an offshore blowout accident. The proposed framework provides a rational way to develop the dynamic risk profile of a rare event for its prevention and control.     

Dynamic probability assessment of urban natural gas pipeline accidents considering integrated external activities

Urban gas pipelines usually have high structural vulnerability due to long service time. The locations across urban areas with high population density make the gas pipelines easily exposed to external activities. Recently, urban pipelines may also have been the target of terrorist attacks. Nevertheless, the intentional damage, i.e. terrorist attack, was seldom considered in previous risk analysis of urban gas pipelines. This work presents a dynamic risk analysis of external activities to urban gas pipelines, which integrates unintentional and intentional damage to pipelines in a unified framework. A Bayesian network mapping from the Bow-tie model is used to represent the evolution process of pipeline accidents initiating from intentional and unintentional hazards. The probabilities of basic events and safety barriers are estimated by adopting the Fuzzy set theory and hierarchical Bayesian analysis (HBA). The developed model enables assessment of the dynamic probabilities of consequences and identifies the most credible contributing factors to the risk, given observed evidence. It also captures both data and model uncertainties. Eventually, an industrial case is presented to illustrate the applicability and effectiveness of the developed methodology. It is observed that the proposed methodology helps to more accurately conduct risk assessment and management of urban natural gas pipelines.     

基于突变理论的采空塌陷区输气管道危险性评价研究

为了减少采空塌陷区输气管道危险性评价中对主观判断的依赖,提出以突变理论为基础的危险性评价模型。首先,从采矿因素、岩体物理力学参数、环境与地质因素和埋地管道因素等4个方面分析采空塌陷区输气管道危险性影响因素;其次,建立采空塌陷区输气管道危险性指标体系;然后,对指标体系中的底层指标进行无量纲化和归一化处理;最后,计算得到输气管道危险性突变数值,进而实现对采空塌陷区输气管道危险性等级的综合评判。将以上评价模型进行实例应用,应用结果表明,基于突变理论的采空塌陷区输气管道综合评价模型可以用于采空塌陷区输气管道的危险性评价。     

基于地震动参数的大型储罐潜在危险性评估方法研究

建设项目安全条件分析中有关自然条件影响分析内容通常采取定性方法加以研究。以地震对大型储罐造成的潜在危险性评估为研究对象,从地震动作用下储罐结构动力响应及破坏特征入手,详细介绍了美国联邦应急管理署(FEMA)开发的HAZUS-MH中的震害危险评估框架及理论模型。重点阐述了地震反应谱、承灾体脆弱性曲线、能力曲线以及需求曲线在危险性评估过程的应用及参数设定。以某大型低温液化气储罐为例,定量计算了地震潜在破坏程度及概率,借此说明该震害危险性评估框架和方法对我国安全评价工作的借鉴意义。     

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.     

Mapping human vulnerability and risk due to chemical accidents

Chemical accidents in the vicinity of densely populated areas can cause colossal damage. Close proximity of chemical facilities to the general public has been identified as a major issue for increased human exposure in 43% of the accidents investigated by the U.S. Chemical Safety Board (CSB). This emphasises the need for incorporating societal factors in risk assessment to plan actions in order to minimise exposure during accidents. The purpose of this research is to develop a model for the assessment of human vulnerability and risk due to chemical accidents. A GIS based methodology is proposed which uses computer aided hazard modelling tools and technical guidelines to model accidents and assesses population vulnerability. The population vulnerability is determined based on a set of societal indicators derived from relevant research work, expert opinions and suggestions by World Bank. Risk is defined as the probable magnitude of harm to humans and dependent on both the degrees of hazard and vulnerability. A case study is carried out by applying the methodology to Meghnaghat Industrial Area in Bangladesh. Accident scenarios are built and hazard modelling software ALOHA is used to spatially display accident footprints. Vulnerability of population is assessed using data from Bangladesh Bureau of Statistics (BBS) and field survey. The hazard footprints and vulnerability map are superimposed using mapping software ArcGIS to generate a composite risk map. The risk map is used to assess existing land use and recommendations are made for future land use planning. The composite risk map is expected to be of help for effective community response, emergency response planning and allocation of medical and support services during emergencies.     

Aspects of risk analysis associated with major failures of fuel pipelines

This paper presents a methodology of risk assessment for hazards associated with transportation of dangerous substances in long pipelines. The proposed methodology comprises a sequence of analyses and calculations used to determine basic reasons of pipeline failures and their probable consequences, taking individual and societal risk into account. A specific feature of this methodology is a combination of qualitative (historical data analysis, conformance test and scoring system of hazard assessment) and quantitative techniques of pipeline safety assessment. This enables a detailed analysis of risk associated with selected hazard sources by means of quantitative techniques. On the ground of this methodology typical problems that usually pose serious threat and constitute part of risk analysis for long fuel pipelines are also presented. To verify above methodology, complete risk analysis was performed for the long distance fuel pipeline in Poland.     

An extension to Fuzzy Fault Tree Analysis (FFTA) application in petrochemical process industry

Fault Tree Analysis (FTA) is an established technique in risk management associated with identified hazards specific to focused fields. It is a comprehensive, structured and logical analysis method aimed at identifying and assessing hazards of complex systems. To conduct a quantitative FTA, it is essential to have sufficient data. By considering the fact that sufficient data is not always available, the FTA method can be adopted into the problems under fuzzy environment, so called as Fuzzy Fault Tree Analysis (FFTA). This research extends FFTA methodology to petrochemical process industry in which fire, explosion and toxic gas releases are recognized as potential hazards. Specifically, the case study focuses on Deethanizer failure in petrochemical plant operations to demonstrate the proposed methodology. Consequently, the study has provided theoretical and practical values to challenge with operational data shortage in risk assessment.     

An integrated methodology to manage risk factors of aging urban oil and gas pipelines

Aging urban oil and gas pipelines have a high failure probability due to their structural degradation and external interference. The operational safety of the aging urban oil and gas pipeline is challenged by different hazards. This paper proposes a novel methodology by integrating an index-based risk evaluation system and fuzzy TOPSIS model for risk management of aging urban oil and gas pipelines, and it is carried out by evaluating the priority of hazards affecting pipeline safety. Firstly, the hazard factors of aging urban oil and gas pipelines are identified to establish an index-based risk evaluation system. Subsequently, the fuzzy TOPSIS model is employed to evaluate the importance of these hazard factors and to decide which factors should be managed with priority. This work measures the importance of a hazard factor from three aspects, i.e. occurrence (O), severity (S) and detectability (D), and the weights of these three parameters are determined by a combination weight method. Eventually, the proposed methodology is tested by an industrial case to illustrate its effectiveness, and some safety strategies to reduce the operational risk of the pipeline are presented. The proposed methodology is a useful tool to implement more efficient risk management of aging urban oil and gas pipelines.     

城市重大危险源区域风险评价方法研究

针对城市应急管理的特点,提出了一种城市重大危险源区域风险评价方法。在ARAMIS方法的基础上,对严重度计算进行了修订,引入了急性暴露指南（AEGL）标准对事故后果进行分区;同时,增加了与应急救援效率相关的指标进行风险目标的脆弱性评估;利用GIS技术,对严重度和脆弱性进行叠加分析,绘制出城市重大危险源区域风险地图。以液氨储罐毒气泄漏事故为例,对文中提出的方法进行了验证。实例分析表明,此方法为快速获取城市重大危险源区域风险的空间分布格局提供了新思路,对于降低城市突发环境污染事故的影响和辅助决策者制定科学的城市公共安全管理决策具有一定的现实意义。     

A semi-quantitative methodology for risk assessment of university chemical laboratory

University chemical laboratory is a high-risk place for teaching and scientific research due to the presence of various physical and chemical hazards. In recent years, university chemical laboratory accidents occur frequently. This urges the need to enhance university chemical lab safety. A semi-quantitative methodology comprising Matter-Element Extension Theory (MEET) implemented with Combination Ordered Weighted Averaging (C-OWA) operator is proposed to assess the risk of a university chemical laboratory. First, an index-based risk assessment system of university chemical laboratory is built by identifying various risk factors from a system perspective. Then, C-OWA operator is used to calculate the weight of assessment indices, whereas MEET is employed to determine the correlation degree of assessment indices. Finally, the comprehensive risk of university chemical laboratories is assessed, and some safety measures are proposed to reduce the risk of university chemical laboratories. The applicability of the proposed methodology is tested using a practical case. It is observed that the methodology can be a useful tool for risk assessment and management of university chemical laboratories.     

Supporting the selection of process and plant design options by Inherent Safety KPIs

Effective support of inherent safety implementation in process design requires a quantitative metric for monitoring and communicating the expected safety performance of alternative design options. The Inherent Safety Key Performance Indicators (IS-KPIs) methodology was developed to provide both a flexible procedure for the identification of the hazards, and a sound consequence-based quantification of the safety performance. The integration of different hazard identification techniques yields the relevant accident scenarios for each unit in the plant. The calculation of credible damage distances by consolidate consequence simulation models provides a sound basis for the definition of the KPIs based on worst case effects. Specific indicators were devoted to hazards from external actions, as natural events and intentional malicious acts. The methodology was demonstrated by the comparison of alternative technological options for LNG regasification. The application evidenced the potential of the IS-KPI method in pinpointing the critical issues related to each alternative configuration.     

Fire and explosion assessment on oil and gas floating production storage offloading (FPSO): An effective screening and comparison tool

Fires and explosions have been identified as major potential hazards for Oil and Gas Floating Production Storage Offloading (FPSO) installations and pose risk to personnel, assets, and the environment. Current fire and explosion assessment (FEA) tools require physical effect modeling software and follows standards from API, ISO, and engineering practices. However, the tools are not specific to any particular system such as an FPSO, and do not provide comprehensive guidance for safety engineers to perform FEA.This paper discusses the development of a screening and comparison tool for FEA on FPSOs and the incorporation of an expert system into the tool. The results are computerized using MS Excel/VBA to provide a structured and comprehensive assessment on each equipment and module handling natural gas, crude oil, methanol and diesel on FPSO topsides.This tool features built-in calculations for jet and pool fire size estimation for gas/liquid releases, and the ability to perform Quantitative Risk Analysis (QRA) to specify the personnel and equipment risk for varying leak sizes and process conditions. Control and recovery measures are incorporated as an expert system based on report findings, engineering practices, and relevant standards. Bowtie analysis is applied in the tool to define detailed control and recovery measures for the FPSO based on the incident scenarios. An explosion assessment is performed by incorporating physical effect modeling software results.Unique features provided in the tool include fire and radiation contour mapping on an FPSO layout to help determine personnel and equipment risk more accurately and fire pump sizing that can be used to verify the amount of water deluge system required to mitigate fires and explosions. In addition, flexibility of data input (process data, failure rate data, etc.) and user interfaces assist safety engineers to screen and compare process alternatives, check design quality, and evaluate design options at any design stage.     

Inherent safety tool for explosion consequences study

The lack of formal integration between process design stages with risk and consequence estimation is a hurdle to designing inherently safe process plants. Conventional risk assessment methodologies are often not carried out concurrently with process design. Therefore, process designers lack the information about risk levels and consequence that may result from the process conditions being considered in a particular process route until the design is completed. Hence, effects of changes in process conditions on risk levels and consequence cannot be studied in a time effective manner during the design stages. Few studies have been identified on the possibility and viability of integrating risk estimation with process design. But viable framework and methodology for doing so has not yet been reported. This paper presents a feasible framework in which risk and consequences estimation can be part of design stages. A demonstrative tool named as integrated risk estimation tool (iRET) was developed by using process simulation software, HYSYS and spreadsheet, MS Excel as the platforms. iRET estimates risk due to explosions by using TNT equivalence method and the TNO correlation method. iRET has a potential to be extended to include all forms of risk such as fire, explosion, toxic gas releases and boiling liquid expanding vapour explosion (BLEVE). The paper also presents case studies to demonstrate the functionality and viability of using iRET in conjunction with process design. The results of these case studies have successfully shown that the risk due to explosion can be assessed during the initial design stage ensuring a safer plant. The framework and iRET there by presented here provide systematic methodology and technology to design inherently safer plants.     

Semi-quantitative risk assessment of commercial scale supply chain of hydrogen fuel and implications for industry and society

This paper is derived from a study on the safety of bulk transport and storage of hydrogen as a fuel, carried out by the Health and Safety Laboratory (HSL) for the Department for Transport (DfT). The aim of the study was to identify the knowledge and data required to develop fully a risk assessment for a hydrogen delivery and storage infrastructure. The methodology used was to begin to carry out a risk assessment for a representative delivery and storage supply chain, using a risk assessment methodology commensurate with the availability of necessary data. Semi-quantitative risk assessment was carried out through top-down HAZID brainstorming, consequence modelling using commercially available software, and use of a risk matrix.Finally through the risk assessment carried out and relevant literature review, the gaps in hazard identification, consequence modelling and frequency assessment, which should be filled to develop a quantified methodology, were compiled.Using data for current UK LPG consumption, comparisons were made between hydrogen and LPG for mode of failures and number of trips required to supply equivalent energy demand. The implications of using ammonia as a hydrogen carrier (hydrogen is within the ammonia molecule) and regulatory implications on hydrogen fuelling or storage sites are also discussed.     

综合安全评价(FSA)方法

为提高国际海运安全管理的决策水平,国际海事组织(IMO)接受并倡导由英国海运界提出的综合安全评价(FSA)方法,笔者对FSA方法作了本质性分析和应用性研究。阐述了FSA的由来,5个组成步骤及相互关系和流程,揭示了FSA与风险管理和安全系统工程的渊源;介绍了危险识别的7种工具;对步骤二“风险评估”重点引入了半定量分析方法和定量分析方法,并用集合论观点讨论了事故频率和后果严重度的计算方法;介绍了风险控制方案的“成本与效益评估”的数学模型;归纳了FSA方法的优缺点。指出FSA是一种集风险评价和成本/效益评估于一体,兼顾技术性与经济性,可广泛兼容具体评价方法和普遍适用各类风险评价的框架性方法,但具体应用需要有效整合适用的定性和定量方法。     

Risk assessment of antagonistic hazards

This paper considers the risk to major hazard plant from terrorists deliberately causing catastrophic industrial accidents. The United States of America Department of Justice [Assessment of the increased risk of terrorist or other criminal activity associated with posting off-site consequence analysis information on the internet, 2000] reports that “breaching a containment vessel of an industrial facility with an explosive or otherwise causing a chemical release may appear relatively simple to…a terrorist”. They concluded that the risk of such action is “real and credible”.

Analysis of terrorism is often hampered by its being described as ‘irrational’; one corollary would be that it is unpredictable. However, terrorism may usefully be treated as a rational behaviour and in doing so it becomes possible to assess the risks it causes.

We analyse the vulnerability of major hazard plant to terrorist attack and identify nine factors (access, security, visibility, opacity, secondary hazard, robustness, law enforcement response, victim profile, and political value) that might be used as a starting point for more formal risk assessment and management.