Competency requirements for process hazard analysis (PHA) teams

Process hazard analysis (PHA) is a cornerstone of process safety management programs. The quality of the PHA performed directly affects the level of risk tolerated for a process. The lower the quality of a PHA, the more likely higher risk will be tolerated. There are few requirements for PHA team members in the U.S. Occupational Safety and Health Administration's process safety management regulations. More detailed requirements for participation in a PHA are desirable.A competency management program should be used to ensure PHA practitioners and teams are appropriately qualified. Criteria for selecting PHA team leaders, or facilitators, and other team members are key to such a program and are described in this paper. The criteria cover both technical and personal attributes. Application of the criteria is described and team performance metrics, which can be used to correlate performance with the assessment of competency to validate the criteria and methods used, are discussed.Owing to the importance of the role played by team leaders, certification of their competency is desirable. Criteria for certification are described and their application is discussed.     

国外化工企业工艺安全技术管理概述

国外化工企业工艺安全技术管理范畴主要包括PHA、MOC、RA/RM、事故调查、其他工艺安全管理工具等。本文主要介绍了国外化工企业常规工艺安全技术管理MOC———变更管理的概念、流程,临时MOC、MSR、PSSR等概念及流程。PHA———工艺危险性分析是国外化工企业工艺安全技术管理核心,主要应用于大型或复杂项目,重点详述了工艺危险性分析的流程、步骤以及四种常用的危险识别方法———HAZOP、SCA、What-If、FEMA的概念、主要步骤、分析过程及主要优点。一旦工艺危险被分析识别后,阐述了如何运用风险评估和风险管理（RA/RM）步骤、后果等级、频率评价、风险等级矩阵和风险降低的主要方法,如何采用故障树FTA和事件树ETA两种不同的方法测算各种事件或故障发生的概率以及事故的后果等级,最后介绍了故障树FTA和事件树ETA的主要步骤和方法。     

基于PHA-LEC法的建筑工程项目安全评价问题研究

建筑工程项目现场条件复杂,各工种交叉作业,极易产生安全事故。本文结合预先危险分析方法(PHA)和作业条件危险性评价方法(LEC)对建筑工程项目的安全评价问题展开研究。首先是从指标量化和危险性等级多重约束分级的角度改进了PHA-LEC方法,并引入POSE四维度分析方法来辅助解决PHA-LEC改进方法中包括参数取值和计算规则在内的三个核心问题。随后,本文设计了基于PHA-LEC改进方法的建筑工程项目安全评价流程,提出要加强基础数据的收集和危险源数据库标准化建设工作。最后就该安全评价流程的应用提出了三点建议,以加强建筑工程项目安全评价工作的效率和有效性。     

The role of people and human factors in performing process hazard analysis and layers of protection analysis

Process hazard analysis (PHA) and Layers of Protection Analysis (LOPA) studies address human failures in operating and maintaining processes and the human factors that influence them, amongst other types of failures. People perform PHA and LOPA studies and, therefore, such studies themselves are subject to various possible human failures. Much less attention has been paid to the human factors that influence the performance of PHA and LOPA studies than human factors that influence hazard scenarios. Human failures in the performance of PHA and LOPA studies should be of significant concern to practitioners as such studies are difficult and time-consuming activities that place significant demands on participants, which increases the chance that errors will be made. Human factors such as willingness to rely on the unsubstantiated opinions of others, groupthink, underestimation of the frequencies of low-probability, high-consequence events, and allowing a false sense of accomplishment to distract from implementing study results must be recognized and addressed.This paper identifies and discusses various human factor issues that can influence the quality of PHA and LOPA studies covering preparing for, conducting, recording, documenting, and following-up on studies. Guidelines are provided to help minimize the extent to which these human factor issues may impair study quality.     

On the need for system-theoretic hazard analysis in the process industries

Most process hazard analysis (PHA) studies today are conducted using traditional methods such as the hazard and operability study (HAZOP). Traditional methods are based on a chain-of-events model of accident causality. Current models of accident causality are based on systems theory and provide a more complete representation of the causal factors involved in accidents. Consequently, it is logical to expect that PHA methods should reflect these models, that is, system-theoretic hazard analysis (STHA) should be used. Indeed, system-theoretic process analysis (STPA) has been developed as such a method. STPA has been used in a variety of industries but, at this time, it has not gained acceptance by the process industries. This article explores the reasons for this situation. Expectations for PHA in the process industries are examined and issues for the application of STPA in the process industries are discussed. It is concluded that a variety of matters must be addressed before STPA can be considered as a viable PHA method for the process industries and the case for the use of STHA in the process industries is not yet proven.     

Requirements for improved process hazard analysis (PHA) methods

In order to develop better process hazard analysis (PHA) approaches, weaknesses in current approaches first must be identified and understood. Criteria can then be developed that new and improved approaches must meet. Current PHA methods share common weaknesses such as their inability specifically to address multiple failures, their identification of worst-consequence rather than worst-risk scenarios, and their focus on individual parts of a process. There has been no comprehensive analysis of these systemic weaknesses in the literature. Weaknesses are identified and described in this paper to assist in the development of improved approaches. Knowledge of the weaknesses also allows PHA teams to compensate for them to the extent possible when performing studies.Key criteria to guide the development of improved methods are proposed and discussed. These criteria include a structure that facilitates meaningful brainstorming of scenarios, ease of understanding and application of the method by participants, ability to identify scenarios efficiently, completeness of scenario identification, exclusion of extraneous scenarios, ease of updating and revalidating studies, and ease of meeting regulatory requirements. Some proposals are made for moving forward with the development of improved methods including the semi-automation of studies and improvements in the training of team members.     

驾驶舱屏蔽系统预先危险性分析

挖掘机驾驶舱屏蔽系统是确保挖掘机能够于放射性环境下作业的特殊构造,是作业人员安全防护的关键措施。首先对驾驶舱屏蔽系统进行介绍;其次基于能量释放理论将驾驶舱屏蔽系统事故分为座椅振动、舱内噪声、机械事故、辐射事故四大类,并做出驾驶舱屏蔽系统能量释放图;继而提出九因素综合调研统计方法,并将其运用至驾驶舱屏蔽系统核辐射事故预先危险性分析(PHA)中;最后,制出驾驶舱屏蔽系统综合PHA分析表,旨在通过PHA分析结果提升驾驶舱屏蔽系统安全性能。     

Reducing unknown risk: The safety engineers’ new horizon

A significant gap exists between accident scenarios as foreseen by company safety management systems and actual scenarios observed in major accidents.The mere fact that this gap exists is pointing at flawed risk assessments, is leaving hazards unmitigated, threatening worker safety, putting the environment at risk and endangering company continuity. This scoping review gathers perspectives reported in scientific literature about how to address these problems.Safety managers and regulators, attempting to reduce and eventually close this gap, not only encounter the pitfalls of poor safety studies, but also the acceptance of ‘unknown risk’ as a phenomenon, companies being numbed by inadequate process safety indicators, unsettled debates between paradigms on improving process safety, and inflexible recording systems in a dynamic industrial environment.The immediacy of the stagnating long term downward major accident rate trend in the Netherlands underlines the need to address these pitfalls. A method to identify and systematically reduce unknown risks is proposed. The main conclusion is that safety management can never be ready with hazard identification and risk assessment.     

戴腰山铜矿采矿技改工程安全评价研究

为了提高戴腰山铜矿采矿技改工程本质安全程度,辨识技改工程中存在的主要危险、有害因素;结合技改项目资料和现场调查,将该项目划分为10个评价单元;针对不同评价单元特点,分别采用安全检查表(SCL)、预先危险性分析(PHA)、事故树分析(FTA)和作业条件危险性评价法(LEC)等对该技改工程中的危险、有害因素进行了定性、定量评价;针对安全评价中出现的问题提出了切实可行的安全措施建议。     

Got a risk reduction strategy?

Process safety can be viewed as part of a triad that supports safety in a petrochemical facility. The other two parts are OSHA-type people safety (slips, falls, etc.) and industrial hygiene. The paper will look at process safety from a top down, plant centric view. Process safety can be distilled down to the basic concept of risk reduction. If we reduce risk, our facility will be safer. The obvious problem is that we have potential risks everywhere so how are we going to reduce all these risks to an acceptable level. Clearly we need a strategy or to use a less fancy word – a plan.Too many times it is easy to concentrate on certain aspects such as safety instrumented systems (SIS), layer of protection analysis (LOPA), behavioral safety, prevention, etc. and lose track of the whole picture of what risk reduction entails in a plant.This paper will look at risk reduction in a facility from a plant viewpoint and will cover the details and concepts of risk reduction across a wide spectrum of plant functionalities – safety climate and culture, process safety management, mechanical integrity and risk, layers of protection in risk reduction, loss of containment/hazard relationship, the risk reduction bow-tie diagram, developing a risk reduction strategy, risk reduction strategy elements, and sustainability.It will also discuss some key concepts in dealing with risk reduction in general.     

Improved management practice and process hazard analysis techniques for minimizing likelihood of process safety incidents in Taiwan

In Taiwan, process safety accidents often occur despite the prior implementation of process hazard analysis (PHA). One of the main reasons for this is the poor quality of the PHA process; with the main hazards not being properly identified, or properly controlled. Accordingly, based on the findings of 86 process safety management (PSM) audits, dozens of post-accident site resumption review meetings, and hundreds of PSM review sessions, this study examines the main deficiencies of management practice and PHA implementation in Taiwan, and presents several recommendations for improved PHA assessment techniques and procedures. The study additionally examines the feasibility for using PSM-related information, such as process safety information and process incident information, as a tool for further enhancing the PHA quality. Overall, the study suggests that, in addition to following the basic rules of PHA and requirements of OSHA (1992),management in Taiwan should also provide training in the enhanced assessment techniques proposed herein and take active steps to incorporate PSM information into the PHA framework in order to improve the general quality of PHA and reduce the likelihood of process safety accidents accordingly.     

Integrating cybersecurity in hazard and risk analyses

As operational and information technologies converge to allow for remote and real-time access to plant operating data and control functions, the process industry could become increasingly susceptible to cyber-attacks. Traditional hazard and risk analysis methods appear inadequate to identify, prevent, and mitigate such attacks. This paper discusses the significance of incorporating cybersecurity vulnerability analysis not just as part of process hazard analysis (PHA), but also in terms of protecting the process control network and implementing adequate safeguards in general against cyber threats. A layer of protection analysis (LOPA) is adapted to evaluate potential weaknesses and ensure safeguards for critical applications would be resistant to cyber-attacks. Integrating cybersecurity into hazard and risk analyses as well as other elements of process safety management (PSM) is demonstrated with examples, making the plant more resilient against both traditional and cyber threats.     

A new accident model for engineering safer systems

New technology is making fundamental changes in the etiology of accidents and is creating a need for changes in the explanatory mechanisms used. We need better and less subjective understanding of why accidents occur and how to prevent future ones. The most effective models will go beyond assigning blame and instead help engineers to learn as much as possible about all the factors involved, including those related to social and organizational structures. This paper presents a new accident model founded on basic systems theory concepts. The use of such a model provides a theoretical foundation for the introduction of unique new types of accident analysis, hazard analysis, accident prevention strategies including new approaches to designing for safety, risk assessment techniques, and approaches to designing performance monitoring and safety metrics.     

Organizational Climate Metrics as Safety,Health and Environment Performance Indicators and an Aid to Relative Risk Ranking within Industry

The chemical, pharmaceutical and other related process industries are characterized by inherently hazardous processes and activities. To ensure that considered risk management decisions are made it is essential that organizations have the ability to rank the risk profiles of their assets and operations. Current industry risk ranking techniques are biased toward the assessment of the risk potential of the asset or operation. Methodologies used to assess these risks tend to be engineering-based and include, for example, hazard identification and event rate estimation techniques. Recent research has associated lagging safety performance indicators with metrics of organizational safety climate. Despite the evidence suggesting their potential usefulness, organizational climate metrics have not yet been exploited as a proactive safety, health and environmental performance indicator or as an aid to relative risk ranking. This paper summarizes research that successfully produced a statistical model of organizational climate and its relationship to site significant injury frequency rates, allowing the relative risk ranking of sites based upon organizational climate metrics. The responses to an industrial organizational survey are examined for a pharmaceutical company's sites in the United Kingdom, Sweden and the United States. Projection to Latent Structures Analysis is performed on the survey responses. The resultant models are shown to be able to accurately model the site significant injury frequency rates. The organizational climate metrics that discriminate between the safety performance levels of different sites are identified.     

Qualitative Assessment for Inherently Safer Design (QAISD) at preliminary design stage

Conventional hazard evaluation techniques such as what-if checklist and hazard and operability (HAZOP) studies are often used to recognise potential hazards and recommend possible solutions. They are used to reduce any potential incidents in the process plant to as low as reasonably practicable (ALARP) level. Nevertheless, the suggested risk reduction alternatives merely focus on added passive and active safety systems rather than preventing or minimising the inherent hazards at source through application of inherently safer design (ISD) concept. One of the attributed reasons could be the shortage of techniques or tools to support implementation of the concept. Thus, this paper proposes a qualitative methodology that integrates ISD concept with hazard review technique to identify inherent hazards and generate ISD options at early stage of design as proactive measures to produce inherently safer plant. A modified theory of inventive problem solving (TRIZ) hazard review method is used in this work to identify inherent hazards, whereby an extended inherent safety heuristics tool is developed based on established ISD principles to create potential ISD options. The developed method namely Qualitative Assessment for Inherently Safer Design (QAISD) could be applied during preliminary design stage and the information required to apply the method would be based on common process and safety database of the studied process. However, user experiences and understanding of inherent safety concept are crucial for effective utilisation of the QAISD. This qualitative methodology is applied to a typical batch reactor of toluene nitration as a case study. The results show several ISD strategies that could be considered at early stage of design in order to prevent and minimise the potential of thermal runaway in the nitration process.     

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.     

危险品道路运输风险分级指数法研究

危险品道路运输过程风险影响因素多,随机性和不确定性大,定量风险评价比较复杂,至今没有统一的风险评估模型.为了有效预防危险品运输事故和进行快速风险评估,基于运输危险品本身特性和相关的风险影响因素探讨了运输危险品现实风险分级指数法.该方法由危险品风险分级指数、路线影响因素和安全措施补偿因子3部分构成.危险品风险分级指数由危险品加权平均风险等级和运输危险品量、泄漏点与居民区距离以及危险品扩散因子等级确定.危险品加权平均风险等级涉及其健康危害性、可燃性、化学反应活性以及特殊危险性(氧化性和与水反应性)等级的确定.路线影响因素包含运输道路特征、气象条件、交通状况和影响人员分布4类.安全措施补偿因子为车辆、设备、容器、包装因子,人员素质因子和安全管理因子3类.该方法可对运输危险品的潜在风险进行快速分级,有利于采取有效的安全预防和控制措施,降低运输事故概率和沿线影响人员风险.     

石油化工企业火气系统安全性评估方法

火气系统属于减缓层内的安全仪表系统,在减轻事故后果方面起到非常重要的作用。针对传统火气系统只满足功能需求设计的不足,提出与风险分析相结合的火气系统设计新理念,以具体案例分析场景危险性,通过覆盖率、可用性、有效性等参数,定量场景的潜在生命损失,以风险降低为目的,量化计算事故后果和频率,评估火气系统的有效性。     

Using risk tolerance criteria to determine safety integrity levels for safety instrumented functions

Standards and industry guidelines for Safety Instrumented Systems (SISs) describe the use of hazard and risk analysis to determine the risk reduction required, or Safety Integrity Levels (SILs), of Safety Instrumented Functions (SIFs) with reference to hazardous events and risk tolerance criteria for them. However, significant problems are encountered when putting this approach into practice. There is ambiguity in the meaning of the term hazardous event. Notably, even though it is a key concept in the process-sector-specific SIS standard, IEC 61511/ISA 84, it is not defined in the standard. Consequently, risk tolerance criteria for hazardous events are ill-defined and, therefore, they are not the most appropriate criteria to use. Most current approaches to SIL determination use them and therefore they are flawed fundamentally.An informed decision on the tolerability of risk for a facility cannot be made by determining only the tolerability of risk for individual hazardous events. Rather, the tolerability of the cumulative risk from all hazard scenarios and their hazardous events for a facility must be determined. Such facility risk tolerance criteria are the type used by regulators. This issue applies to all per event risk tolerance criteria. Furthermore, determining the tolerability of risk for a facility based only on the risks of single events, be they hazard scenarios or hazardous events, and comparing them to risk tolerance criteria for the events is not meaningful because there is no consideration of how many such events can actually occur and, therefore, no measure of the total risk. The risks from events should be summed for a facility and compared with overall facility risk tolerance criteria.This paper describes and illustrates SIL determination using a risk model implemented within the framework of Layers of Protection Analysis (LOPA) that overcomes these problems. The approach allows the allocation of risk across companies, facilities, processes, process units, process modes, etc. to be managed easily.     

A methodology for identifying and addressing dead-legs and corrosion issues in a Process Hazard Analysis (PHA)

Identifying dead-legs and related corrosion issues continues to be a challenge in the process industry. Pipeline corrosion has been a factor in several recent incidents involving releases and fires. A review of incident reports and citations over the past ten years indicates that Process Hazard Analysis (PHA) revalidations have been noted for not addressing the hazards of a process including corrosion mechanisms and dead-legs. In order for the hazards to be addressed, they must first be accurately identified in a PHA and documented along with any recommended actions for preventive maintenance. This paper describes a methodology for identifying and addressing dead-legs and related corrosion issues in a PHA that can be used to update corporate PHA procedures to be more robust in preventing corrosion related incidents.