DRC signal treatment for heat flow and reagents accumulation determination

In order to optimize the use of the DRC^® data (Differential Reaction Calorimeter commercialized by Setaram SA), Aventis Pharma Safety Laboratories and the Thermokinetic team of Nice Sophia-Antipolis University have developed a software which deconvolutes collected DRC data to assess the real heat flow and determine reagents accumulation. The accuracy of the results given by the DRC is shown for three batch reactions (neutralization, hydrolysis and acylation). The results are very close to those obtained by RC1 online heat flow measurements.     

Pressure relief sizing of reactive system using DIERS simplified methods and dynamic simulation method

Incidents involving uncontrolled chemical reactions continue to result in fatality, injury and economic loss. These incidents are often the result of inadequate pressure relief system designs due to a limited knowledge of the chemical reactivity hazard. A safe process design requires knowledge of the chemical reactivity of desired as well as undesired chemical reactions due to upset conditions. Simplified, cost effective methods to relief system sizing are presented by The Design Institute of Emergency Relief Systems (DIERS). They require multiple experiments, and sizing is only valid for the system composition and thermal inertia represented by the small scale experiments. Results are often conservative, especially for gassy systems. Detailed, dynamic computer simulation is highly accurate and can be used for iterative design and multiple scenario evaluation.In this study, an accelerating rate calorimeter (ARC^®) and a low thermal inertia calorimeter (automatic pressure tracking adiabatic calorimeter – APTAC™) were used to collect chemical reactivity data for the dicumyl peroxide and toluene system. Results of the pressure relief system sizing using the dynamic simulation method are presented and compared with DIERS simplified methods.     

Model-based zero emission safety concept for reactors with exothermal reactions for chemical plants

To avoid major accidents caused by runaway reactions, a new safety concept called SmartHIP¹ is introduced, with the objective to prevent runaway reactions and avoid emissions. The basic principle is based on an online model-based approach by using safety instrumented systems. Different criteria exist for calculating the hazard potential of a runaway reaction and its early detection. The approaches of the literature from the last years are analysed and divided into three different groups: Divergence, Accumulation and Adiabatic Criterion. Each approach is compared to the other by applying it to an esterification reaction of acetic anhydride with methanol. The approaches are evaluated according to different requirements, like accuracy, wide range of application or reliability.     

施工现场工作环境安全评价

随着经济的发展,人们对于安全,包括工作环境的安全的要求越来越高.目前对工作环境安全性的评价,一是采用定性的方法,二是依靠历史统计数据,对危险性进行量化.主要对象是人机环境中"机"的因素.本文利用实验心理学的有关理论,尝试通过人对环境的生理、心理反应建立评价工作环境安全性的方法.该方法应用于竹脚手架、金属脚手架的安全性比较研究的实验,分析结果显示它能够较客观地评价工作环境的安全程度.     

苯和甲苯硝化及磺化反应热危险性分级研究

首先介绍了化工工艺热安全性的内涵,并从反应过程热危险性分析的方法学出发,介绍间隙、半间歇化学反应工艺热危险性分级研究的总体思路及方法。然后,围绕甲苯和苯的硝化、磺化反应,用全自动反应量热仪(RC1e)和加速度量热仪(ARC)测定其反应过程的绝热温升(△Tad)、目标反应所能达到的最高温度(TM)、分解反应最大速率到达时间(θD)等参数。运用风险评价指数矩阵法(方法1)和基于失控过程温度参数的热危险评估法(方法2)分别对其硝化和磺化反应过程的热危险性进行了分级评估。结果表明,这两种方法具有良好的一致性;给定工艺条件下甲苯和苯的一段硝化反应过程的热危险度等级较低;而磺化反应的热危险较高。尽管这两种方法还有一定的局限性,但对于间歇、半间歇合成工艺的本质安全化设计、工艺热危险性的评估具有重要的参考价值和实用意义。     

Sam Mannan and his scientific publications: A life in process safety research

Dr. M. Sam Mannan is one of the true pioneers in the process safety area, spending almost his entire lifetime in process safety and risk research. He was dedicated to ‘make safety second nature’ and published an impressive body of work. An overview of his research helps understanding the process safety area and provides insight in the legacy of this process safety pioneer. In this paper, 327 publications authored by Dr. Mannan from 1999 to 2019 in Web of Science core collection were downloaded and visually analyzed from four perspectives: his publication outputs, collaboration networks, topic areas, and highly cited papers and cited references. The results show a rapidly increasing trend in his research activity, mostly through journal publications. He published in 53 different outlets, with Journal of Loss Prevention in the Process Industries being most frequently selected. Dr. Mannan had a very active and diverse worldwide network, and collaborated with 18 different countries/regions, nearly 90 different institutions and 387 authors. His publications addressed process safety-related topics widely, including safety related to liquefied natural gas, explosions, runaway reactions, inherent safety, flammability and aerosol, and more recently resilience. Dr. Mannan's most cited paper focused on ‘fuzzy risk matrix’, whereas the most frequently cited reference in his work is ‘thermal hazard evaluation by an accelerating rate calorimeter’ by Townsend DI in 1980. Based on his most recent research activity, promising future directions for process safety research include resilience linked to risk assessment and management, for instance through the ‘safety triad’ concept he promoted shortly before passing away.     

Predicting safety culture: the roles of employer, operations manager and safety professional

Introduction: This study explores predictive factors in safety culture. Method: In 2008, a sample 939 employees was drawn from 22 departments of a telecoms firm in five regions in central Taiwan. The sample completed a questionnaire containing four scales: the employer safety leadership scale, the operations manager safety leadership scale, the safety professional safety leadership scale, and the safety culture scale. The sample was then randomly split into two subsamples. One subsample was used for measures development, one for the empirical study. Results: A stepwise regression analysis found four factors with a significant impact on safety culture (R² = 0.337): safety informing by operations managers; safety caring by employers; and safety coordination and safety regulation by safety professionals. Safety informing by operations managers (ß = 0.213) was by far the most significant predictive factor. Impact on industry: The findings of this study provide a framework for promoting a positive safety culture at the group level.     

On the use and misuse of detected onset temperature of calorimetric experiments for reactive chemicals

The interpretation of the detected onset temperature for DSC and other calorimetric measurements used for Reactive Chemicals is briefly discussed in terms of calorimeter sensitivity and reaction dynamics. Common misinterpretations are also addressed. It is shown that the detected onset temperature should not be considered as an upper stability limit for a process defining the ‘start’ of undesired reactions. It is also not a point below which processes can operate safely at any temperature. In the latter case, an arbitrary choice of operating somewhere below a detected onset temperature can stall desired chemistry, lead to an over-conservative safety margin impacting cycle time/production rates, or provide a false sense of security triggering serious consequences. An understanding of the heat gain rates and heat loss rates is necessary to engineer for safe operations.     

Thermal hazard in a batch process involving hydrogen peroxide

Hydrogen peroxide is a versatile and interesting reagent for many industrial processes; nevertheless, it is very sensitive to impurities that can catalyze its decomposition, so that the desired reaction could be accompanied by undesired parallel and consecutive reactions. As an example, the butadiene free radical polymerization with hydrogen peroxide in the presence of an organic solvent was studied. Batch polymerization occurs in the liquid phase at about 120 °C. Because of the involved reactive compounds and the relatively high temperature, this is an intrinsically dangerous reaction. Therefore calorimetric data can give important information about safety and process optimization during the scale-up. The aim of this research project was to study the influence of impurities on the overall heat of reaction. The experiments were made in a high-pressure reaction calorimeter. The study has revealed that impurities do indeed affect the reaction course. Most importantly, the presence of carboxylic acids and/or ionic iron must be avoided and the recycle of unreacted reagents must be carefully controlled to minimize the build-up of these impurities.     

Perceived benefits of applying Pay for Safety Scheme (PFSS) in construction – A factor analysis approach

In recent years, construction safety has been a hot topic in Hong Kong. The Government of the Hong Kong Special Administrative Region (HKSAR) has launched different safety measures to improve the prevailing safety performance of the construction industry. The Pay for Safety Scheme (PFSS) has emerged as one of the major safety initiatives launched within the public sector construction industry since 1996. It aims to encourage the safety awareness by taking the contractor’s pricing for safety-related items out from the consideration of competitive bidding. The objective is to provide a concise review of the prevailing application of PFSS in Hong Kong in general, and to identify and analyse the key benefits of PFSS in construction through an industry-wide empirical questionnaire survey in particular. Altogether, 145 industrial practitioners who have derived extensive hands-on experience with the PFSS construction projects participated in the survey to indicate their levels of agreement to those 14 key benefits identified which were measured and analysed by factor analysis. The results of factor analysis indicated that the 14 individual benefits of implementing PFSS were consolidated under four underlying factors: (1) Enhancing safety climate and attitude; (2) Promoting effective safety-related communication; (3) Streamlining the safety procedures; and (4) Ensuring adequate safety training. A wider application of PFSS should be encouraged with a view to achieving better safety performance within the industry. It is recommended that a similar scheme to PFSS currently applied in Hong Kong may be developed for implementation in other regions or countries for international comparisons.     

Research on the critical temperature of thermal decomposition for large cartridge emulsion explosives

Emulsion explosives are one type of main industrial explosives. The emergence of the large cartridge emulsion explosives has brought new security incidents. The differential scanning calorimeter (DSC) and the accelerating rate calorimeter (ARC) were selected for the preliminary investigation of the thermal stability of emulsion explosives. The results showed that the initial thermal decomposition temperatures were in the range of 232–239 °C in nitrogen atmosphere (220–232 °C in oxygen atmosphere) in DSC measurements and 216 °C in ARC measurements. The slow cook-off experiments were carried out to investigate the critical temperature of the thermal decomposition (T_c) of the large cartridge emulsion explosives. The results indicated that the larger the diameter of the emulsion explosives, the smaller the T_c is. For the large cartridge emulsion explosives with diameter of 70 mm, the T_c was 170 °C at the heating rate of 3 °C h⁻¹. It is a dangerous temperature for the production of the large cartridge emulsion explosives and it should cause our attention.     

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.     

The impact of differences in reliability data on the results of probabilistic safety analyses

The lack of plant-specific reliability data for probabilistic safety assessments is occasionally used for discrediting and doubting the validity of such analyses. On the other hand, analyses are often performed without even discussing the applicability of generic reliability data. In an attempt of clarification the impact of several sets of reliability data stemming from different sources on the explosion frequency of two processes with exothermal reactions (one of them is analyzed with plant-specific data) are quoted. As a further case study the reactor cooling system of one of the processes is analyzed. Additionally, a procedure using frequency and probability ranges is employed for comparison. The results show agreement within their respective uncertainty bounds; the identification of key components for safety is not hampered by data differences. The superiority of plant-specific data, which should of course be acquired, cannot be doubted. Nevertheless, improving the safety of a plant is possible using probabilistic safety analyses even with data which do not stem from the plant under investigation.     

SVM application in hazard assessment: Self-heating for sulfurized rust

In order to assess the oxidation self-heating hazard of sulfurized rust, for particular ambient conditions in crude oil tanks, the support vector machine (SVM) technique is applied to predict the maximum temperature (T_max) of oxidation self-heating process. Five governing parameters are selected, i.e. the water content, mass of sulfurized rust, operating temperature, air flow rate and oxygen concentration in the respiratory/safety valve. The efficiency and validity of the SVM predictions are investigated in the case of two sets of data: more than 85 experiments performed in academic lab (China) and almost 17 additional results collected from existing literature. Two main steps are also discussed: the training process (on selected subsets of data) and prediction process (for the remaining subsets of data). It can be concluded that for both datasets the maximum temperature (T_max) values calculated by SVM technique were in good accordance with the experimental results, with relative errors smaller than 15% except for a few cases.The SVM technique seems therefore to be relevant and very helpful for complex implicit processes such as chemical reactions, as it is the case of the oxidation of sulfurized rust in oil tanks. Furthermore, such predictive methods can be continuously be improved through additional experiments feedback (larger databases) and can then be of crucial help for monitoring and early warning of hazardous reactions.     

Factors contributing to commercial vehicle rear-end conflicts in China: A study using on-board event data recorders

Introduction: In the last 30 years, China has undergone a dramatic increase in vehicle ownership and a resulting escalation in the number of road crashes. Although crash figures are decreasing today, they remain high; it is therefore important to investigate crash causation mechanisms to further improve road safety in China. Method: To shed more light on the topic, naturalistic driving data was collected in Shanghai as part of the evaluation of a behavior-based safety service. The data collection included instrumenting 47 vehicles belonging to a commercial fleet with data acquisition systems. From the overall sample, 91 rear-end crash or near-crash (CNC) events, triggered by 24 drivers, were used in the analysis. The CNC were annotated by three researchers, through an expert assessment methodology based on videos and kinematic variables. Results: The results show that the main factor behind the rear-end CNC was the adoption of very small safety margins. In contrast to results from previous studies in the US, the following vehicles' drivers typically had their eyes on the road and reacted quickly in response to the evolving conflict in most events. When delayed reactions occurred, they were mainly due to driving-related visual scanning mismatches (e.g., mirror checks) rather than visual distraction. Finally, the study identified four main conflict scenarios that represent the typical development of rear-end conflicts in this data. Conclusions: The findings of this study have several practical applications, such as informing the specifications of in-vehicle safety measures and automated driving and providing input into the design of coaching/training procedures to improve the driving habits of drivers.     

绿色技术评价磺化反应过程热危险性

反应量热仪RC1研究磺化反应过程中热危险性具有评价路线简单、易于操作、过程绿色环保等优势,近年来逐渐成为研究的热点.磺化反应过程中由于工艺的不同,不同磺化反应过程的热危险性也具有很大的差别.通过反应量热仪RC1、差示扫描量热DSC、绝热加速量热仪ARC对10种不同工艺的磺化反应过程的热危险进行了深入的研究,对企业实践生...     

Stigma at work: The psychological costs and benefits of the pressure to work safely

Introduction: Workplace accidents and injuries can be quite costly to both individual employees and their organizations. While safety climate (i.e., perceptions of policies and procedures related to safety that should reflect an organization's value of safety) has been established as a predictor of safety behaviors, less research has considered the possible negative pressures that could result from an environment that emphasizes safety. Though organizations may intend to create a positive safety climate, concerns about being treated differently if an employee were to be involved in a safety incident may result in unintended, but detrimental safety and health outcomes. Method: This study investigated the stigma associated with being involved in a safety-related incident in relation to self-reported safety behaviors and psychological health outcomes. The data were acquired through a two-wave prospective design, surveying workers from Amazon Mechanical Turk (MTurk; N = 528) who indicated they were exposed to at least one physical work stressor (e.g., heavy lifting; air quality; standing for extended periods) a few times each month or more. Results: When controlling for safety climate, safety stigma was related to decreased safety compliance and poorer psychological health. There was a marginally significant interaction between safety stigma and safety motivation in relation to safety compliance. Conclusions: These findings suggest that experiencing pressure to work safely, for fear of being evaluated negatively, may actually come at the cost of employees' safety compliance and psychological health. Practical applications: These results may be useful in assessing and intervening to improve an organization's safety climate. Organizations should closely examine the climate for safety to ensure that positive aspects of safety are not undermined by a stigmatizing pressure associated with safety in the work environment.