Integration of process control protection layer into a simulation-based HAZOP tool

This paper discusses the framework methodology behind the proposed simulation-based HAZOP tool. Simulation-based approach is one of the many ways to support conventional HAZOP by its automation. Compared to knowledge-based and other approaches, a HAZOP software tool based on deviations simulation is able to examine the investigated process more into detail and so find root causes of hazardous consequences. Another advantage is the ability to identify also potential hazards which did not occur in the past and might be overlooked. The presented framework methodology uses a layer of protection analysis (LOPA) concept of independent protection layers (IPLs) testing. Control system integrated into the raw process design represents the first of various protection layers of the LOPA concept. As a case study, a CSTR chemical production with nonlinear behavior under Proportional-Integral-Derivative (PID) actions as the predominant type of classical feedback control strategy is used. The presented tool identifies hazardous regimes under conditions when control loop introduces hazardous consequences or even acts synergically with existing hazardous events. Risk derived from different consequences is ranked by the risk assessment matrix (RAM) as a part of the conventional quantitative HAZOP study.     

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.     

Dynamic risk assessment using failure assessment and Bayesian theory

To ensure the safety of a process system, engineers use different methods to identify the potential hazards that may cause severe consequences. One of the most popular methods used is quantitative risk assessment (QRA) which quantifies the risk associated with a particular process activity. One of QRA's major disadvantages is its inability to update risk during the life of a process. As the process operates, abnormal events will result in incidents and near misses. These events are often called accident precursors. A conventional QRA process is unable to use the accident precursor information to revise the risk profile. To overcome this, a methodology has been proposed based on the work of Meel and Seider (2006). Similar to Meel and Seider (2006) work, this methodology uses Bayesian theory to update the likelihood of the event occurrence and also failure probability of the safety system. In this paper the proposed methodology is outlined and its application is demonstrated using a simple case study. First, potential accident scenarios are identified and represented in terms of an event tree, next, using the event tree and available failure data end-state probabilities are estimated. Subsequently, using the available accident precursor data, safety system failure likelihood and event tree end-state probabilities are revised. The methodology has been simulated using deterministic (point value) as well as probabilistic approach. This Methodology is applied to a case study demonstrating a storage tank containing highly hazardous chemicals. The comparison between conventional QRA and the results from dynamic failure assessment approach shows the significant deviation in system failure frequency throughout the life time of the process unit.     

中小企业作业场所有毒有害物质危险评价方法

针对中小企业职业卫生管理中专业人员、技术及资源缺乏的特点建立了一种作业场所有毒有害物质危险评价分级的简便方法。该方法建立在物质的毒性评估和暴露评估基础之上,能对有毒有害物质的危害性进行科学、客观的评价,而且该方法实用性很强,无需太多的专业知识和技术的要求,很好满足了中小企业在有毒有害物质危险评价方面的需求。此外,在危险评价分级基础上,对不同的危害等级提出了相应的控制策略,为中小企业制定作业场所有毒有害物质的控制措施提供有价值的参考。     

A new simple methodology for evaluation of explosion risk in underground coal mines

The key objective of this paper is the presentation of a new risk assessment tool for underground coal mines based on a simplified semi-quantitative estimation and assessment method.In order to determine the risk of explosion of any work process or activity in underground coal mines it is necessary to assess the risk. The proposed method is based on a Risk Index obtained as a product of three factors: frequency of each individual scenario P_ucm, associated severity consequences C_ucm and exposure time to explosive atmospheres E_ucm. The influence of exposure time is usually not taken into account up to now. Moreover, the exposure to explosive atmospheres may affect factors of hazardous event probability as much as its consequences. There are many definitions of exposure to explosive atmospheres but in the case of underground coal mines the exposure is defined as frequency risk of firedamp and coal dust. The risk estimation and risk assessment are based on the developed of a risk matrix.The proposed methodology allows not only the estimation of the explosion risk but also gives an approach to decide if the proposal investment is well-justified or not in order to improve safety.     

Fuzzy logic for piping risk assessment (pfLOPA)

This paper explores the application of the fuzzy logic for risk assessment of major hazards connected with transportation of flammable substances in long pipelines. As a basis for risk assessment, the framework of the fuzzy Layer of Protection Analysis (fLOPA) was used. fLOPA presents a new approach to risk assessment based on two assumptions: 1. different effects of the layer of protection functions on particular elements of the risks (frequency and severity of consequence), and 2. the application of fuzzy logic system (FLS) composed of three elements: fuzzification, inference process and defuzzification. A further calculation follows LOPA methodology with the use of fuzzy logic system where fuzzy risk matrix is used for risk assessment. A typical case study comprising section of a long pipeline failure is performed and a comparison between the classical LOPA approach and fuzzy approach is made.     

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.     

Transport risk modeling for hazardous chemical transport Companies—A case study in China

Traffic accidents of hazardous chemical transport vehicles strongly correlate with the operation and management level of road transport companies. An accurate risk assessment of these transport companies will play a critical role in improving their management and supervision and in turn the overall safety of roadways, property, and most importantly people's lives. Therefore, this study constructs a logistic regression scorecard model to evaluate transport risk of hazardous chemical transport companies and evaluates it using a case study in China. This study first selected 16 indicators from the dimensions of driver behaviors, driving performance, dangerous goods and company business operation to construct company user portraits. Next, a K-means++ algorithm was used to cluster the data samples of the companies on a monthly basis. On this basis, a scorecard was constructed based on a logistic regression scorecard model to realize and visualize the monthly risk portrait of companies. The constructed scorecard predicted transport risk of companies accurately. The results show that the more complex the types of dangerous goods transported, the higher the risk value of the company in the dangerous goods index. Moreover, for transport companies, the driver behaviors and driving performance on their trips are closely related to their business risk. In a practical application, the proposed scorecard can realize the dynamic risk monitoring of transport companies and enable managers and supervision departments to clarify where the risk is from. The transport companies can also carry out safety training and rectification for drivers and operations to reduce the occurrence of hazardous materials-related traffic accidents.     

Developing a new fuzzy inference system for pipeline risk assessment

The problem of less and/or even lack of information and uncertainty in modeling and decision making plays a key role in many engineering problems; so that, it results in designers and engineers could not reach to sure solutions for the problems under consideration. In this paper, an application of the fuzzy logic for modeling the uncertainty involved in the problem of pipeline risk assessment is developed. For achieving the aim, relative risk score (RRS) methodology, one of the most popular techniques in pipeline risk assessment, is integrated with fuzzy logic. The proposed model is performed on fuzzy logic toolbox of MATLAB^® using Mamdani algorithm based on experts' knowledge. A typical case study is implemented and a comparison between the classical risk assessment approach and the proposed model is made. The results demonstrate that the proposed model provides more accurate, precise, sure results; so that, it can be taken into account as an intelligent risk assessment tool in different engineering problems.     

Economic valuation of damages originated by major accidents in port areas

Due to special features of ports – variety of activities: storage and loading/unloading of hazardous materials; circulation of ships, lorries and trains; proximity to urban zones; etc. – major accidents can be associated with severe damages. The cost of such accidents must be known to allow for compensation to people and companies. A procedure is presented to estimate the cost of damages suffered by people, equipment and environment. Criteria to assess the cost of damage to people – a controversial issue – are discussed, establishing a method to predict the number of people killed, injured and evacuated. Economic compensation is proposed. Environmental damages are also considered. These include potential damage to the atmosphere, soil, water and fauna. Estimates of the cost of the equipment and buildings affected by the accident are proposed. Finally, an assessment of the loss of profits due to activity breakdown and indirect costs is analysed. The methodology presented can easily be extended to general, inland process and storage sites.     

低温乙烯储存过程风险评价及其缓解对策

为加强危险化学品储存的环境安全性,在深入调研危化品储存环节主要风险的基础上建立评价指标体系,采用层次分析法与模糊综合评价法相结合的风险评估模型对低温乙烯罐储存过程进行风险评估,并提出可行的控制措施。研究结果表明,储罐环境安全处于安全级内;针对低温乙烯罐存在的风险建立EHS一体化管理模式,建立全厂应急预案及一系列的风险预防措施,以缓解其储存过程的风险。     

Operational risk assessment: A case of the Bhopal disaster

Accidental releases of hazardous chemicals from process facilities can cause catastrophic consequences. The Bhopal disaster resulting from a combination of inherently unsafe designs and poorly managed operations is a well-known case. Effective risk modeling approaches that provide early warnings are helpful to prevent and control such rare but catastrophic events. Probability estimation of these events is a constant challenge due to the scarcity of directly relevant data. Therefore, precursor-based methods that adopt the Bayesian theorem to update prior judgments on event probabilities using empirical data have been proposed. The updated probabilities are then integrated with consequences of varying severity to produce the risk profile.This paper proposes an operational risk assessment framework, in which a precursor-based Bayesian network approach is used for probability estimation, and loss functions are applied for consequence assessment. The estimated risk profile can be updated continuously given real-time operational data. As process facilities operate, this method integrates a failure-updating mechanism with potential consequences to generate a real-time operational risk profile. The real time risk profile is valuable in activating accident prevention and control strategies. The approach is applied to the Bhopal accident to demonstrate its applicability and effectiveness.     

一种新型危险化工工艺安全评估方法的设计

在安全生产过程中,建设项目风险评价在我国经过几十年的发展,无论在模型亦是方法上均有所进步,但对化工项目进行危险化工工艺风险等级评价的研究并不多见。本文按照危险化工工艺表征涉及的影响因素,在参考了日本劳动省"六阶段"的定量评价表以及危险度评价法并对15种危险化工工艺定性分析的基础上,提出了一种基于危险度评价法的更为全面的危险化工工艺辨识方法。该评价方法可用于确定危险化工工艺的风险等级。为化工企业工艺危险的实时评估和安全管理提供技术支撑和科学途径。     

Risk analysis system for the transport of hazardous materials

IntroductionIn this paper, a literature study on risk analysis systems for the transport of hazardous materials was conducted.ResultsThe insights that resulted from this literature review have led to the development of a refined approach to map the risk of hazmat transport in Flanders based on historical accident data. The proposed framework allows setting up an overall risk map for hazmat transport by different transport modes. Additionally, a methodology to calculate a local accident risk, which takes local infrastructure parameters and accident data into account, is being introduced. In the presented framework one of the general principles is that the risk of a catastrophic hazmat incident can be divided into two parts, which can both be validated on the basis of accident data: (a) the calculation of the general probability of the occurrence of an accident based on international accident data of transport of hazardous materials – this is the basis for the global risk map, and (b) the calculation of the local probability of the occurrence of an accident based on accident data and infrastructure parameters of the complete available freight transport in Flanders – this is the basis for the local risk map. The ratio between these two results in a locality parameter, which represents the local specific circumstances that can lead to an accident.ConclusionsThis evaluation framework makes it possible to estimate the risks of hazmat transport along a specific route for transport by road, rail, inland navigation and even pipelines.     

Risk-based maintenance (RBM): a quantitative approach for maintenance/inspection scheduling and planning

The overall objective of the maintenance process is to increase the profitability of the operation and optimize the total life cycle cost without compromising safety or environmental issues. Risk assessment integrates reliability with safety and environmental issues and therefore can be used as a decision tool for preventive maintenance planning. Maintenance planning based on risk analysis minimizes the probability of system failure and its consequences (related to safety, economic, and environment). It helps management in making correct decisions concerning investment in maintenance or related field. This will, in turn, result in better asset and capital utilization.

This paper presents a new methodology for risk-based maintenance. The proposed methodology is comprehensive and quantitative. It comprises three main modules: risk estimation module, risk evaluation module, and maintenance planning module. Details of the three modules are given. A case study, which exemplifies the use of methodology to a heating, ventilation and air-conditioning (HVAC) system, is also discussed.     

航运企业风险评估的实施

航运业历来就是一种高风险的行业,随着航运科技和安全管理手段的不断发展,全球航运安全形势呈现了良好的态势,尤其自1998年7月1日国际海事组织公布了以ISO9002为基准的《国际安全管理规则》（ISM CODE）以来,航运业的安全管理进入了国际标准化时代。为进一步完善航运业的标准化管理,国际海事组织在85届海安会上通过了MSC.237（85）决议批准了ISMCODE的修正案,并要求航运企业自2010年7月1日起针对安全和防止污染的任何活动都需要进行风险评估。为保证航运企业能够正确进行安全活动的风险评估,以满足该修正案的要求,应用风险决策法系统分析了航运企业进行船舶、人员和环境风险评估所涉及的各个要素。提出一套合理、实用和系统的航运企业风险评估方法,并对风险评估实施过程需要特别关注的问题进行阐述。对进一步提高船舶安全操作水平有了重要的现实意义。     

A new approach for facility siting using mapping risks on a plant grid area and optimization

The present work is focused on developing a methodology to find the optimal placement of a hazardous process unit and other facilities using optimization theory while considering a risk map in the plant area. Incidents can have possible consequences resulting from flammable gas releases, which can be evaluated by using consequence modeling programs. The probability of each incident can be derived from initial leak hole size estimation through event tree analysis. In this methodology the plant area was divided into square grids and risk scores were estimated for each grid. The overall cost is a function of the probable cost of property damage due to fires or explosions and the interconnection cost including piping, cable, and management. The proposed approach uses a mixed integer linear optimization programming (MILP) that identifies attractive locations by minimizing the overall cost. A case study is presented for a hexane–heptane separation facility that considers the meteorological data for the given area in order to show the applicability of the proposed methodology. Results from this study will be useful in assisting the selection of locations for facilities and for risk management.     

A novel approach based on non-parametric resampling with interval analysis for large engineering project risks

The issue of risk assessment has been always the matter of debate in large engineering projects (LEPs). The assessment is an indispensable means for the projects to accomplish their objectives. It is firmly accepted that LEPs are particularly subject to more potential risks than other business activities because of their complexity, uncertainty and ambiguity. These characteristics are often conducive to small sample sizes of the gathered risk data in practice. Consequently, traditional statistical techniques cannot contribute significantly to analyze the risk data. The non-parametric resampling technique, namely bootstrap, has been used subsequently to solve numerous complicated problems and evaluate the accuracy of a parameter estimator in situations where commonly used techniques are not valid. It is also more natural, applicable and simple to estimate the risk data in an interval form under decision-making process by considering the concept of safety by professional experts in LEPs. Hence, in this paper, a new approach based on bootstrap technique with the interval analysis is presented in the context of the project risk assessment. The proposed approach not only plays an important role in reducing risk data and saving time but also is more economical. A real case study is conducted to illustrate the applicability of the approach. Finally, the comparison results indicate that the proposed approach outperforms the traditional technique in terms of the accuracy and efficiency.     

System safety assessment using safety entropy

Safety assessment has a primary role in hazardous operations. Most studies on safety assessment focus on risk and accident modeling, in which safety is absent. These top-down methods are highly dependent on the occurred accidents to establish accidental scenarios, which may make the assessment approach lagging behind the evolving modern systems. Moreover, this “special to general” logic is scientifically suspect in safety assessment. There is a call for the development of safety assessment methods in the presence of system safety to complement risk-focused safety analysis. These methods should provide a framework based on a bottom-up approach to examine system safety from the operational perspective. This paper has attempted to provide a potential solution. In particular, a novel concept of safety entropy is proposed to integrate with The Functional Resonance Analysis Method (FRAM), which is used to form the qualitative understanding of a system. A formula consisted of safety entropy, functional conformability, and system complexity has been established to determine the spontaneity of the safety state-changing process. The proposed method is applied to the safety assessment of a propane feed-control system. The results show the applicability of the method. Nevertheless, the model still needs to be further improved to fulfill better support for safety-related decision problems.     

基于风险的危险品道路运输安全容量研究

为了确定危险品道路运输安全容量，保障危险品道路运输安全，基于风险理念，使用对比研究方法，提出危险品道路运输个人风险基准，建立改进的危险品道路运输定量风险评估模型。结合提出的风险基准，提出危险品运输安全容量确定方法，解决了单一类别和多种类别危险品运输安全容量确定问题。研究结果表明:在某城市化工集聚区的实例应用该方法，能够大幅度降低危险品道路运输潜在生命损失，有助于保障危险品道路运输安全。