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.     

Simulation-based approach to design of inherently safer processes

Safety of chemical processes and plants is a matter of high priority. The design of an inherently safer process is one of very beneficial ways of achieving this goal.The paper describes the method of designing an inherently safer process for a chosen set of equipment and materials involved by applying non-linear optimization. The optimization is aimed at finding an operational mode, which guarantees safety of the process under normal conditions and provides maximal attainable safety in case of one typical accident scenario – cooling failure. Discussion covers problem statement, choice of the optimization criteria, appropriate methods for defining control variables.An important practical challenge is stability analysis of the optimized process mode with respect to permissible deviations of control parameters and variables from the estimated values. The original method for the stability analysis of a non-stationary process is proposed. It comprises simplified preliminary evaluation method followed by the more detailed numerical optimization-based analysis.Several examples illustrate application of the methods proposed.     

Incorporating inherent safety during the conceptual process design stage: A literature review

This paper reviews principal concepts, tools, and metrics for risk management and Inherently Safer Design (ISD) during the conceptual stage of process design. Even though there has been a profusion of papers regarding ISD, the targeted audience has typically been safety engineers, not process engineers. Thus, the goal of this paper is to enable process engineers to use all the available design degrees of freedom to mitigate risk early enough in the design process. Mainly, this paper analyzes ISD and inherent safety assessment tools (ISATs) from the perspective of inclusion in conceptual process design. The paper also highlights the need to consider safety as a major component of process sustainability. In this paper, 73 ISATs were selected, and these tools were categorized into three groups: hazard-based inherent safety assessment tools (H-ISATs) for 22 tools, risk-based inherent safety assessment tools (R-ISATs) for 33 tools, and cost-optimal inherent safety assessment tools (CO-ISATs) for 18 tools. This paper also introduces an integrated framework for coordinating the conventional process design workflow with safety analysis at various levels of detail.     

Nonlinear molecular based modeling of the flash point for application in inherently safer design

New chemical process design strategies utilizing computer-aided molecular design (CAMD) can provide significant improvements in process safety by designing chemicals with required target properties and the substitution of safer chemicals. An important aspect of this methodology concerns the prediction of properties given the molecular structure. This study utilizes one such emerging method for prediction of a hazardous property, flash point (FP), which is in the center of attention in safety studies. Using such a reliable data set comprising 1651 organic and inorganic chemicals, from 79 diverse material classes, and robust dynamic binary particle swarm optimization for the feature selection step resulted in the most efficient molecular features of the FP investigations. Apart from the simple yet precise five-parameter multivariate model, the FP nonlinear behavior was thoroughly investigated by a novel hybrid of particle swarm optimization and support vector regression. Besides, 195 missing experimental FPs of the DIPPR data set are predicted via the presented procedure.     

Toward an inherently safer design and operation of batch and semi-batch processes: The N-oxidation of alkylpyridines

This work shows an application of inherent safety principles to a reaction widely used in the pharmaceutical industry. More specifically, it incorporates the teachings of Trevor Kletz into the design of an inherently safer process for the N-oxidation of alkylpyridines. This reaction is of interest because of the hazards resulting from the undesired, gas-generating decomposition of hydrogen peroxide, the oxidizing agent. The generation of oxygen, combined with the flammability of the alkylpyridines, represents a serious fire and explosion hazard for this process. The purpose of this paper is to demonstrate how an inherently safer process can be potentially achieved by designing improved reactors and by assessing conditions that reduce or eliminate the hazards. Furthermore, it is shown that such improvement in safety increases the efficiency of the process and results in a cost reduction.     

设计初期化工过程本质安全化设计策略

该文提出了一种在设计初期进行化工过程本质安全化设计的策略。首先进行危险物质与危险能量两类共计11种危险类型的危险辨识。针对辨识出的危险类型,通过与相应的临界条件比较进行快速的危险评价,对于不可接受的危险必须采取本质安全化措施,可接受的危险可有选择性地进行本质安全化设计。在设计初期可以使用的本质安全化原则主要是消除、最小化、替代和缓和,针对11种危险类型可以应用不同的本质安全化设计模型,以使实际进行本质安全化设计时更加简单与快捷。该文把提出的本质安全化设计策略应用到一个甲苯硝化制硝基甲苯的工艺,形成了多种本质安全化措施,可以用来在设计初期消除或减少危险。     

Kletz's legacy for developing countries: Simple systems based on inherently safer design

The now well-known theory surrounding Inherently Safer Design (ISD) developed by Trevor Kletz has spread worldwide thanks to journals and almost unlimited communication between members of process safety all around the globe. This means that developing countries, such as Colombia, now have the possibility of applying it to their specific situations, which can often be resolved if the safety hierarchy is followed in order to attack problems from the design stage, a solution that might not seem instinctive, but is actually effective since there isn't a “reduction” strategy, but a removal of hazards. To apply this methodology to a specific Colombian case study, a previous quantitative risk analysis of an LPG storage tank farm in Colombia is revised and reformulated by developing an optimization (MINLP) based on the principles of inherent safety in order to design the same process (LPG pressurized storage) so that the available engineering tools can be used to mathematically formulate the inherent safety criteria. This allows determining the design conditions and safety measures needed to reduce the likelihood of an incident, being consistent with the Inherent Safety philosophy, which seeks a change of mental structure when designing processes, just like Trevor Kletz proposed and established as a new paradigm for Process Plants/Equipment design. The results of the project allow obtaining a specific optimal configuration of control, wall thickness, operating pressure and tank dimensions, pointing out a decrease of around 20% on the operating pressure.     

FMEA and consideration of real work situations for safer design of production systems

Production equipment designers must ensure the health and safety of future users; in this regard, they augment requirements for standardizing and controlling operator work. This contrasts with the ergonomic view of the activity, which recommends leaving operators leeway (margins for manoeuvre) in performing their task, while safeguarding their health. Following a brief analysis of design practices in the car industry, we detail how the Failure Modes and Effects Analysis (FMEA) approach is implemented in this sector. We then suggest an adaptation that enables designers to consider real work situations. This new protocol, namely, work situation FMEA, allows experience feedback to be used to defend the health standpoint during designer project reviews, which usually only address quality and performance issues. We subsequently illustrate the advantage of this approach using two examples of work situations at car parts manufacturers: the first from the literature and the second from an in-company industrial project.     

Solvent design and inherent safety assessment of solvent alternatives for palm oil recovery

The concept of inherent safety is important in developing an inherently safer and user-friendly process. This paper discusses a new integrated approach of computer-aided product design and inherent safety assessment. Computer-aided Molecular Design (CAMD) approach was utilized in this work to identify potential alternative to n-hexane, the widely used industrial solvent in extracting residual palm oil from pressed palm fibre. The formulation of solvent mixtures was optimized to meet the targeted physical properties before being tested using the Soxhlet Extraction method. Inherent safety assessment to assess the solvent's flammability, toxicity, reactivity, and explosiveness was conducted on the new solvent mix, Mixture 1 (n-hexane + ethanol), Mixture 2 (n-hexane + acetone) and Mixture 3 (n-hexane + n-butanol). It was found that Mixture 1 and 3 are safer than n-hexane and able to extract more oil than n-hexane and Mixture 2. However, the utilization of the solvent is dependent on the end product from the residual palm oil.     

Integration of data analytics with cloud services for safer process systems,application examples and implementation challenges

Emerging sensors, computers, network technologies, and connected platforms result potentially in an immeasurable collection of data within plant operations. This creates the possibility of solving problems innovatively. Because most of the data appear to be unstructured or semi-structured, organizations shall design and adopt new strategies. Further, workflow architectures with data analytics are needed including machine learning tools and artificial intelligence techniques before proto-type solutions can be developed. We shall discuss several prospects of using (big) data analytics integrated with cloud services to produce solutions for improving plant operations. The paper outlines the vision and a systematic framework highlighting the data analytics lifecycle in the area of plant operation, process safety, and environmental protection. Four rather diverse example case studies are demonstrated including (1) deep learning-based predictive maintenance monitoring modeling, (2) Natural Language Processing (NLP) for mining text, (3) barrier assessment for dynamic risk mapping (DRA), and (4) correlation development for sustainability indicators. It further discusses the challenges in both research and implementation of proposed solutions in the industry. It is concluded that a well-balanced integrated approach including machine supporting decisions integrated with expert knowledge and available information from various key resources is required to enable more informed policy, strategic, and operational risk decision-making leading to safer, reliable and more efficient operations.     

Inherent risk assessment methodology in preliminary design stage: A case study for toxic release

At preliminary design stage, process designers normally lack of information on the risk level from process plant. An inherently safer process plant could be designed if the information of risk levels could be known earlier at the preliminary design stage. If the risk level could be determined, there is a possibility to eliminate or reduce the risk by applying the well-known concept: inherent safety principle. This paper presents a technique to determine the risk levels at preliminary process design stage using a 2-region risk matrix concept. A model to calculate the severity and likelihood of a toxic release accident was developed in Microsoft Excel spreadsheet. This model is integrated with process design simulator, iCON to allow for data transfer during preliminary design stage. 2-region risk matrix is proposed and used to evaluate the acceptability of the inherent risk based on the severity and likelihood rating. If the inherent risk level is unacceptable, modification for improvement can be done using the inherent safety principles. A case study has been carried out to illustrate the benefit of applying this newly developed technique. It was successfully shown that an inherently safer plant could easily be designed by applying this technique.     

Creating safer workplaces: assessing the determinants and role of safety climate

PROBLEM: Although there has been considerable interest in safety climate, relatively little attention has been given to the factors that determine safety climate or to testing the hypothesized mediating role of safety climate with respect to safety-related outcomes. METHOD: Questionnaire responses were obtained from 2,208 employees of a large national retail chain in 21 different locations. RESULTS: After controlling for demographic variables, three factors: environmental conditions, safety-related policies and programs, and general organizational climate, accounted for 55% of the variance in perceived safety climate. Interestingly, organizational climate made a significant contribution to safety climate, even after controlling for the other more safety-relevant variables. Partial correlations showed that safety policies and programs had the largest observed correlation with safety climate, followed by two of the dimensions of organizational climate (communication and organizational support). Using Baron and Kenny's (J. Pers. Soc. Psychol. 51 (1986) 1173) procedures, the principal effects of the various work situation factors on perceived safety at work were found to be direct rather than mediated by safety climate. Safety climate influenced perceived safety at work, but its role as a mediator was limited. IMPACT ON INDUSTRY: These results are discussed in terms of other recent findings on safety climate and the growing interest in understanding management and organizational factors in the context of workplace safety.     

CFD在电除尘器超低排放设计中的应用

由于我国环保排放要求的日益严格,电除尘器超低排放成为最受关注的问题之一。流场作为影响电除尘器超低排放性能的重要因素,具有重要的工程意义。基于CFD(计算流体力学)模拟方法,并结合工程实际应用,从流量分配、本体气流分布设计、本体阻力、电场极配型式、绝缘系统热风吹扫设计等方面对电除尘器流场设计进行阐述和对比分析。结果表明:电除尘器流场优化既要考虑流量分配均匀,又要考虑粉尘量分配均匀,电除尘器入口烟道导流板的合理设计不但可以解决流量分配平衡问题,也可以使粉尘量的偏差得到大幅度改善;进出口喇叭角度不但对本体流场均匀性有影响,对除尘器本体阻力也有较大影响,进口喇叭扩张角、出口喇叭收缩角越大,本体速度分布均匀性越差,本体阻力也越大;灰斗阻流板的合理设计有助于减轻收尘区下沿高速区与灰斗的强回流现象;在不同极配型式中,针刺线平行于极板比针刺线垂直于极板的击穿电压更高,电流密度更均匀,更有利于粉尘收集;改进绝缘系统热风吹扫的方式有助于解决绝缘系统短路现象。     

Demographic similarity to the work group: A longitudinal study of managers at the early career stage

A sample of 141 Canadian business school graduates responded to questionnaires at 3, 9 and 14 months after beginning full-time jobs. Their job experiences including challenge, work group fit, supervisor support, and mentorship were measured along with organizational commitment, turnover, and promotion. There was little evidence of treatment discrimination against the female and minority members of the sample. However, dissimilarity to one's work group in terms of age, education, and lifestyle meant lower job challenge and poorer work group fit. In contrast, being dissimilar in terms of gender meant greater challenge, and, if the manager was male, greater likelihood of promotion. Being dissimilar in terms of culture was not associated with any of the job experiences. Relationships between the early experiences and organizational commitment were strongest for those who were most dissimilar in terms of gender, whereas relationships between the experiences and turnover were strongest for those who were most dissimilar in terms of age, education, and lifestyle.     

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.     

玻璃隔墙冷却专用喷头的设计及其应用效果研究

用水喷淋冷却是提高玻璃隔墙耐火极限的有效途径。首先确定了玻璃隔墙冷却专用喷头的设计目标,基于溅水盘的布水原理,通过溅水盘底部和背部的形状设计,确定了新型喷头的整体结构。然后搭建冷态试验平台进行布水规律试验。以钢化玻璃为冷却对象,在水压为0.05 MPa(表压)下,观察喷头距玻璃隔墙水平距离分别为0.1 m、0.3 m和0.5 m时,喷头在玻璃隔墙表面的布水现象,记录喷水密集和稀疏的区域,从喷洒半径、不同布水区域覆盖面积、水的利用率及水膜厚度等方面分析了布水规律,并与常用工程喷头的布水效果进行了比较。最后进行点火试验,在玻璃表面布置贴片热电偶,以汽油作为燃料,预燃60 s后,启动喷淋系统,分别测定了喷淋启动前后玻璃表面的温度,并选取玻璃迎火面布水密集区的一点计算冷却速率。结果表明:新型喷头的布水效果较好,与直立边墙型喷头相比,水量密集区域的覆盖面积增大了13.9%~19.5%,基本实现了玻璃隔墙表面的全覆盖;喷头冷却速率为1.1,冷却效果较好。     

Risks of faults intrinsic to software languages: Trade-off between design performance and application safety

A lot of products embed software applications carrying out complex functions (e.g. cars, aircrafts, and medical equipments). More and more authority for control is placed on these applications whose failures may lead to accidental loss. Numerous methods have been developed to prevent these failures. These methods apply either to the programs developed or to the design activities. However, the programming or modelling languages used to operationalise the solutions as software applications are rarely questioned. These languages constitute the technology of realization of the program. On one hand, the language features are selected to increase the development performance and to decrease the software application costs. On the other hand, these features may be at the origin of specific types of faults which constitute the intrinsic risks of these languages. Therefore, the choice of a language or of a subset of a language, leads to a decision-making issue of how to deal making safety and performance trade-offs. The first part of the paper analyzes the evolution of the programming languages. We show that these changes were aimed at the convergence of design performance improvement with designed application safety. The introduction of the object-oriented technologies breaks this commonality. They cut the development expenditures but introduce new types of faults. The decision-makers such as the critical software application producers (e.g. the aircraft manufacturers) and the authorities (e.g. the avionics certification authorities) have to deal with this trade-off. These new technologies cannot be just rejected as they are more and more often used in certain domains (e.g. mobile phones, internet applications). The proposed constraint on using them seem to be too restrictive and are not justified. In particular, the safety levels of software programs developed applying these constraints are not assessed. The second part of the paper addresses these questions. It specifies the problem and it proposes a method to estimate the risk of faults in object-oriented programs. Thus, the decision-makers can elaborate rules for using object-oriented languages establishing a trade-off between the wished-for development performance and the required safety levels.     

黏土地层联络通道冻结壁厚度优化设计及应用研究*

为解决传统冻结壁设计方法不能真实、合理地反映黏土地层中联络通道冻结壁实际受力情况,进而导致冻结壁厚度设计过于保守的问题,结合黏土地层直墙拱形冻结壁实际受力特点,基于对冻结壁支护压力的合理计算,提出1种适用于黏土地层冻结壁厚度设计的优化方法。结果表明:与传统设计方法相比,该方法所确定冻结壁支护压力与实际施工环境中冻结壁受力状态吻合效果更好,并且能够提供合理的安全储备;经数值计算和现场应用验证,计算所得冻结壁设计方案可以满足施工环境中的承载力及变形稳定性要求;且相较传统设计方案,所得方案兼具安全性与经济性,可有效规避因设计过于保守和冻结周期过长引起的冻胀、融沉变形过大等工程灾害的风险;该方法高效、易行,可为传统冻结壁设计方法提供必要补充,亦可为类似工程的施工设计提供有益参考。