过程工业计算机辅助安全防护层分析技术进展

介绍当前过程工业安全防护层分析(LOPA)的基本内容,研讨LOPA方法与深层次的危险和可操作性分析方法(HAZOP)之间的关系以及计算机辅助HAZOP的研究进展。针对人工LOPA方法的缺点,开发了SDG-HAZOP软件平台,为计算机辅助LOPA平台研发创造了先决条件。应用计算机辅助LOPA方法,使防护层的设置具有更好的针对性、合理性和有效性,发挥对事故的预防和预警作用,并具有良好的发展前景。     

HAZOP分析中LOPA的应用研究

通过分析危险与可操作性研究(HAZOP)方法的不足和保护层分析(LOPA)方法的功能,提出将LOPA融入HAZOP分析中,能进一步提高HAZOP的事故预防能力和丰富HAZOP的分析结果。介绍LOPA基本方法,阐述LOPA融入HAZOP的机理、衔接关系及分析步骤,并通过一个化工工艺流程危险性分析实例说明LOPA的作用及如何将LOPA融入HAZOP分析中。结果表明:在HAZOP分析中融入LOPA方法,能实现对现有保护措施的可靠性进行量化评估,确定其消除或降低风险的能力,从而寻求是否需要附加减少风险的安全保护措施。     

Beyond-compliance uses of HAZOP/LOPA studies

Recent years have seen a convergence of scenario-based Hazard and Operability (HAZOP) studies, Layer of Protection Analyses (LOPAs), and safety integrity level (SIL) determinations. These can all be performed using order-of-magnitude estimates for the initiating cause frequency, the effectiveness of protection layers, the severity of loss event consequences, and the inclusion of other risk-reduction factors. Conducting a HAZOP study or a HAZOP/LOPA study in this manner makes it possible to extend the study results to not only determine required SILs, but also to sum scenario risks by process unit and show the quantitative benefit of implementing risk-reduction measures. The aggregated risk can be compared to process-wide tolerable risk criteria, in addition to comparing each scenario to a risk matrix or risk magnitude. This presentation demonstrates how a true risk-based HAZOP study can be performed with little additional effort over that required for commonly performed cause-by-cause HAZOP studies, and how facility managers and engineers can then use the results when deciding on and implementing risk-reduction measures.     

Advanced process control system with MPC as a new approach for layer of protection analysis

Layer of protection analysis (LOPA) is a widely used method to support process safety in the chemical industries. In the LOPA, the process is classified into many layers, one of such layers considers the basic process control system (BPCS) which commonly uses PID controllers. This kind of controllers cannot deal with constraints. For this reason, the main purpose of this work is to provide a framework to enhance the control layer in the LOPA, which consists of a model predictive control (MPC) with safety features. These features include: sublayers in the controller system (such as real time optimization, target calculation, and MPC), safety constraints, and guarantee of stability by adopting an Infinite Horizon MPC (IHMPC). Here, we propose an approach for control-inspired view to process safety, replacing the BPCS by an Advanced Process Control System (APCS). Moving forward with these concepts, first, a literature review emphasizes the content, showing two perspectives for the APCS. The APCS is designed for two varieties of controllers, a basic IHMPC and IHMPC with zone control to compare the performance. In this framework, the first sublayer consists of a real time optimization (RTO) structure, that calculates the optimal operating condition for the process controller, which computes the control action. Besides, RTO has an additional constraint called the safety index, based on the protection of process operational. RTO and basic IHMPC communicate directly, while for IHMPC with zone control there is an inner sublayer called Target Calculation, it computes a feasible target to the controller, working as another safety strategy in APCS. After that, we demonstrate both structures applied to a CSTR reactor. From the case study, we compared both controllers, and evaluated the effect that the safety index constraint causes in the setpoints, outputs, and control actions. The use of safety constraint in RTO proved to be a safe strategy for the control layer, as well as IHMPC with zone control presented a safer profile than basic IHMPC. Furthermore, the results show that safety constraint affect the economic goal, decreasing its value.     

Ontology-based computer aid for the automation of HAZOP studies

Hazard and Operability (HAZOP) studies are conducted to identify and assess potential hazards which originate from processes, equipment, and process plants. These studies are human-centered processes that are time and labor-intensive. Also, extensive expertise and experience in the field of process safety engineering are required. There have been several attempts by different research groups to (semi-)automate HAZOP studies in the past. Within this research, a knowledge-based framework for the automatic generation of HAZOP worksheets was developed. Compared to other approaches, the focus is on representing semantic relationships between HAZOP relevant concepts under consideration of the degree of abstraction. In the course of this, expert knowledge from the process and plant safety (PPS) domain is embedded within the ontological model. Based on that, a reasoning algorithm based on semantic reasoners is developed to identify hazards and operability issues in a HAZOP similar manner. An advantage of the proposed method is that by modeling causal relationships between HAZOP concepts, automatically generated but meaningless scenarios can be avoided. The results of the enhanced causation model are high quality extended HAZOP worksheets. The developed methodology is applied within a case study that involves a hexane storage tank. The quality and quantity of the automatically generated results agree with the original worksheets. Thus the ontology-based reasoning algorithm is well-suited to identify hazardous scenarios and operability issues. Node-based analyses involving multiple process units can also be carried out by a slight adjustment of the method. The presented method can help to support HAZOP study participants and non-experts in conducting HAZOP studies.     

Layer of Protection Analysis – Quantifying human performance in initiating events and independent protection layers

Layer of Protection Analysis (LOPA) is widely used within the process industries as a simplified method to address risks and determine the sufficiency of protection layers. LOPA brings a consistent approach with added objectivity and a greater degree of understanding of the scenarios and risks as compared to purely qualitative studies such as Process Hazard Analyses. LOPA can be used to address a wide range of risk issues and serves as a highly effective aid to decision making.Incorporation of human performance within LOPA is recognized as an important, though often challenging, aspect of the analysis. The human role in potential initiating events or within human independent protection layers is important throughout the process industries, and becomes even more critical for batch processing facilities and in non-routine operations. The human role is key to process safety and the control of risks, necessitating the inclusion and quantification of human actions in independent protection layers for most companies. Human activities as potential initiating events and human performance within independent protection layers are reviewed and methods for quantification outlined. An extension into Human Reliability Analysis (HRA) is provided, including methods to develop Human Error Probabilities specific to the process safety culture and operations at a given plant site.     

ExSys-LOPA for the chemical process industry

The chemical process industries are characterized by the use, processing, and storage of large amounts of dangerous chemical substances and/or energy. Among different missions of chemical plants there are two very important ones, which: 1. provide a safe work environment, 2. fully protect the environment. These important missions can be achieved only by design of adequate safeguards for identified process hazards. Layer of Protection Analysis (LOPA) can successfully answer this question. This technique is a simplified process of quantitative risk assessment, using the order of magnitude categories for initiating cause frequency, consequence severity, and the likelihood of failure of independent protection layers to analyze and assess the risk of particular accident scenarios. LOPA requires application of qualitative hazard evaluation methods to identify accident scenarios, including initiating causes and appropriate safeguards. This can be well fulfilled, e.g., by HAZOP Studies or What-If Analysis. However, those techniques require extensive experience, efforts by teams of experts as well as significant time commitments, especially for complex chemical process units. In order to simplify that process, this paper presents another strategy that is a combination of an expert system for accident scenario identification with subsequent application of LOPA. The concept is called ExSys-LOPA, which employs, prepared in advance, values from engineering databases for identification of loss events specific to the selected target process and subsequently a accident scenario barrier model developed as an input for LOPA. Such consistent rules for the identification of accident scenarios to be analyzed can facilitate and expedite the analysis and thereby incorporate many more scenarios and analyze those for adequacy of the safeguards. An associated computer program is under development. The proposed technique supports and extends the Layer of Protection Analysis application, especially for safety assurance assessment of risk-based determination for the process industries. A case study concerning HF alkylation plant illustrates the proposed method.     

HAZOP、LOPA和SIL方法的应用分析

通过概括介绍危险与可操作性分析(HAZOP)、保护层分析(LOPA)和安全完整性等级分析(SIL)三种方法的特点,总结三种分析方法之间的关系.LOPA分析是HAZOP分析的继续,可以解决HAZOP分析中残余风险不能定量化的不足,是对HAZOP分析结果的丰富和补充;SIL分析则在LOPA分析的基础上,进一步对需要增加的安全仪表系统(SIS)进行设计,并对LOPA分析结果进行验证,即HAZOP、LOPA分析是SIL分析的前期准备工作.因此,在详细介绍SIS的组成、安全生命周期阶段、SIL的选择确定方法以及SIL分析流程之前,也简要介绍了HAZOP、LOPA分析方法,梳理了两种方法的分析流程.最后通过引入示例来展示三种分析方法之间的关系.     

TOPHAZOP: a knowledge-based software tool for conducting HAZOP in a rapid, efficient yet inexpensive manner

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.     

A fuzzy logic and probabilistic hybrid approach to quantify the uncertainty in layer of protection analysis

Layer of protection analysis (LOPA) is a widely used semi-quantitative risk assessment method. It provides a simplified and less precise method to assess the effectiveness of protection layers and the residual risk of an incident scenario. The outcome failure frequency and consequence of that residual risk are intended to be conservative by prudently selecting input data, given that design specification and component manufacturer's data are often overly optimistic. There are many influencing factors, including design deficiencies, lack of layer independence, availability, human factors, wear by testing and maintenance shortcomings, which are not quantified and are dependent on type of process and location. This makes the risk in LOPA usually overestimated. Therefore, to make decisions for a cost-effective system, different sources and types of uncertainty in the LOPA model need to be identified and quantified. In this study, a fuzzy logic and probabilistic hybrid approach was developed to determine the mean and to quantify the uncertainty of frequency of an initiating event and the probabilities of failure on demand (PFD) of independent protection layers (IPLs). It is based on the available data and expert judgment. The method was applied to a distillation system with a capacity to distill 40 tons of flammable n-hexane. The outcome risk of the new method has been proven to be more precise compared to results from the conventional LOPA approach.     

HAZOP-LOPA方法与SIL定级在电镀废水处理中的应用

为了保证电镀废水处理工艺的安全性,首先采用危险与可操作性分析(HAZOP)方法定性辨识工艺中潜在的危险和危害,并提出安全对策措施;然后采用保护层分析(LOPA)方法定量计算现有保护措施是否能够将风险控制在可接受范围;如果风险较高,通过增加安全仪表等级(SIL)降低风险值。并通过实例分析证明HAZOP-LOPA分析方法能够有效地实现电镀废水处理工艺的风险评价。     

A formulation to optimize the risk reduction process based on LOPA

This paper presents a mixed integer nonlinear programming (MINLP) model to improve the computational use of the layer of protection analysis (LOPA). For a given set of independent protection layers to be implemented in a process, the proposed optimization model is solved to: a) Include costs associated with the different prevention, protection and mitigation devices, and b) Satisfy the risk level typically specified in the LOPA analysis through the occurrence probability. The underline purpose focuses on improving the analysis process and decision making to obtain the optimal solution in the safeguards selection that satisfies the requirements to be considered as IPL’s. The optimization is based on economic and risk tolerance criteria. As a first stage of this proposal, the safety instrumented system (SIS) design is optimized so that the selection of SIS components minimizes the risk and satisfies the safety integrity level (SIL) requirements. A case study is presented to validate the whole proposed approach.     

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.     

SIL评估及HAZOP分析技术在海洋平台安全评估中的应用

针对海洋平台安全仪表系统安全可靠性要求的提高,分析海洋平台安全仪表系统SIL评估及HAZOP分析方法,对SIL评估的必要性、目的和内容、方法与流程进行论述,对SIL等级选择的HAZOP和LOPA分析方法进行介绍,对SIL评估过程中的重要数据问题进行阐述,对SIL等级验证中各参数和失效数据的选取进行说明。通过案例进一步论述SIL评估及HAZOP分析技术的要点和实施步骤,针对该案例提出了提高SIL等级的建议和措施,为海洋平台安全仪表系统的SIL评估提供重要的参考和依据。     

合成氨装置系统安全仪表系统安全完整性等级分析

论文在介绍安全仪表系统、安全完整性等级的基本原理基础上,综合分析了危险与可操作性分析(HAZOP)、保护层分析(LOPA)等系统风险分析理论的应用方法。并结合上述理论,确定了安全仪表系统的安全完整性等级(SIL)定级。以合成氨装置为例,应用HAZOP及保护层分析方法,得出了合成塔压力过高及废热锅炉液位过低2个场景下的安全完整性SIL等级。结果表明:合成塔装置仪表的SIL等级为1,废热锅炉仪表的SIL等级为2。     

Dynamic model based safety analysis of a three-phase catalytic slurry intensified continuous reactor

Safety analysis like the HAZOP (HAZard OPerability) study can be much more efficient if a dynamic model of the system under consideration is available to evaluate the consequences of hazard deviations and the efficiency of the proposed safety barriers. In this paper, a dynamic model of a three-phase catalytic slurry intensified continuous chemical reactor is used within the context of its HAZOP (HAZard OPerability) study. This reactor, the RAPTOR®, is an intensified continuous mini-reactor designed by the French company AETGROUP SAS that can replace batch or fed-batch processes in the case of highly exothermic reactions involving hazardous substances. The highly hazardous hydrogenation of o-cresol under high pressure and temperature is taken as an example of application. Deviations as a temperature increase of the cooling medium or no cooling medium flow can produce an overheating of the reactor. Thus, three possible safety barriers are evaluated by simulation: shut off the gaseous reactant feed, shut off the liquid reactant feed or stop the agitation. The more efficient actions are the stopping of the agitation and/or of the gas reactant feed. The simulation results can efficiently help the reactor design and optimisation. Safety analysis can also be one of the criteria to compare batch and intensified continuous processes.     

HAZOP和LOPA方法在食品企业氨制冷系统中的应用

为评估食品企业氨制冷系统所处的风险状态,文章在HAZOP方法和LOPA方法理论研究的基础上,将其组合应用于食品企业氨制冷系统的风险评估中,以提前识别可能导致事故的原因和后果,确定现有防控措施是否足够、有效,并将风险控制在可接受水平。通过对氨制冷系统中低压循环桶液位过高场景的实例分析,得出该场景下的剩余风险基本在企业可接受范围内,不需要增加独立安全仪表系统的结论,为食品企业安全管理决策提供了科学依据。     

Villains,victims, and heroes: Accounting for the roles human activity plays in LOPA scenarios

When a team is analyzing a LOPA scenario, the team needs to consider all three roles played by human interaction in the scenario: that of cause, as a result of human error; that of receptor, both in terms of safety impacts (inside the fence line) and community impacts (outside the fence line); and that of independent layer of protection (IPL), considering both administrative controls and human responses. Frequently, the nature of these three roles are inter-related, and setting guidance that is internally consistent is important to using LOPA to assess risk rather than as a means to game the analyses to simply achieve a wished-for result.A number of criteria have been proposed to quantify human involvement, typically as cause, as receptor, or as IPL. Establishing a framework to look at all three in a unified way is more likely to result in analyses that are consistent from scenario to scenario.This paper describes such a framework and presents it in a way that allows organizations to review their own criteria for quantifying human involvement in LOPA. It also examines some of the published LOPA criteria for human involvement and looks at them in terms of consistency of approach between evaluation of cause, receptor, and IPL. Finally the paper makes suggestions to use in calibrating LOPA methodologies to achieve consistent and believable results in terms of human interaction within and between scenarios that have worked for other organizations.     

烷基苯联合装置风险及控制研究

烷基苯联合装置含有国家安全监管总局首批重点监管的15种危险化工工艺中的加氢工艺、烷基化工艺两种,装置工艺介质为易燃、易爆、有毒及强腐蚀性物质,生产中潜在危险性较大;开展工艺风险研究,落实控制措施,对于提高装置本质安全性具有极为重要意义.首先探讨了工艺危险和要害部位,确认装置主要风险为火灾、爆炸和毒性危害;然后应用HAZOP方法,以加氢反应进料加热炉、烷基化反应器为分析对象,研究了工艺状态参数温度、压力、物料流量等方面出现偏差的原因、后果及安全措施;还对氢气泄漏发生火灾、爆炸和苯泄漏发生火灾、爆炸、人员中毒进行了事故后果定量分析,提出了相应的安全措施,以消除或降低工艺危险,保障装置安全.     

Value at Risk Perspective on Layers of Protection Analysis

Layers of protection analysis (LOPA) is an established tool for designing, characterizing, and evaluating risk in the chemical process industry. Value at risk (VaR) is a method first introduced in the financial sector for modeling potential loss in a complex venture. In this paper we demonstrate the application of VaR principles to the LOPA of an ethylene refrigeration compressor. We calculate the changes in risk profile (probability versus loss) associated with adding or removing different safety interlocks around the compressor. The VaR analysis shows that the benefits of a given layer of protection are not necessarily captured by a single average number, since the entire probability–value curve is affected. This type of analysis will aid in the allocation of limited resources to process risk interventions.