查看更多>>摘要：The rapid development of chemistry in the past years has caused not only serious environmental pollution but also other disastrous accidents to certain local areas, especially those densely populated areas. Therefore, to prevent the disastrous consequences of those accidents on vulnerable areas effectively, the local government should determine the sensibility of different regions to potential risks. An integrated risk assessment procedure, which considers accident consequences and the vulnerability of local population, is presented and then applied to a small town in China. In this procedure, a hazard map is obtained from the footprint of regional hazards. The population vulnerability is determined on the basis of the exposure, sensitivity, and adaptability of residents. Population exposure indicators include population density and dwelling environment. Population sensitivity indicators consist of health status, gender, age, and educational level. Adaptability indicators include emergency supplies, medical resources, and traffic convenience. The ArcGIS mapping software is used to overlay the hazard map and the population vulnerability map to generate a composite risk map. The synthesized human vulnerability index system in combination with regional features, overlapping with possible accident ranges, clarifies the visualization of regional risks. This regional risk map can assess the existing land utilization condition; provide a reference for future land planning, transportation line improvement, and medical service configuration; and benefit emergency plan design and material input.
查看更多>>摘要：Hot work accidents have significant consequences. Admittedly, preventing hot work accidents requires managers to analyze the accident profoundly and learn from the requisite documents that contain the detailed process and causes of the accident. However, the analysis process of unstructured records is manual, leading managers to failing to quickly analyze the cause of the accident and identify the key causes. Therefore, we used deep learning to automatically classify and predict the cause of accidents by the textual features and text mining methods that quickly extract the cause information to optimize accident record analysis. Initially, the latent Dirichlet allocation model was adopted to extract the topic words in the accidents to form cause topics, and convolutional neural networks were trained to predict the cause of the accident based on the previous cause topics. Then, the key causes of hot work accidents were extracted by qualifying the importance score of the cause, which included no gas detection and continuous monitoring, uncleaned combustibles, improper protection measures, and violations of regulations by workers. Managers can utilize these key causes to formulate optimal safety strategies to reduce the number of accidents. This study provides valuable suggestions for improving the process safety management of hot work in China. Moreover, the results of our method can be used as important documents for the safety education and training of the enterprise.
Shahab, Mohammed AatifIqbal, Mohd UmairSrinivasan, BabjiSrinivasan, Rajagopalan...
12页
查看更多>>摘要：Operators' mental models play a central role in safety-critical domains like the chemical process industries. Accurate mental models, i.e., a correct understanding of the process and its causal linkages, are prerequisites for safe operation. Mental models are often defined and explained in abstract terms that make their interpretation subjective and prone to bias. In this work, we propose a Hidden Markov Model (HMM) based formalism to characterize control room operators' mental models while handling abnormal situations. We show that a suitable HMM representing the operator's mental model - including the states, state transition probabilities, and emission probability distributions - can be identified experimentally using data of the operator's control actions, eye gaze, and process variable values. This HMM can be used for the quantitative assessment of operators' mental models as illustrated using various case studies. We discuss the potential applications of the model in identifying various cognitive errors and human reliability assessment. In Part 2 of this paper, we use the proposed approach to assess operators' learning during training.
Shahab, Mohammed AatifIqbal, Mohd UmairSrinivasan, BabjiSrinivasan, Rajagopalan...
12页
查看更多>>摘要：Operator training is critical to ensure safe operation in safety-critical domains such as chemical process industries. Training enhances the operator's understanding of the process, which is then encapsulated as mental models. Typically, the operator's learning in traditional training programs is assessed using expert judgment or in terms of process-and operator action-based metrics. These assessment schemes, however, ignore the cognitive aspects of learning, such as mental model development and cognitive workload. The HMM-based model proposed in Part 1 offers a systematic way to quantify operators' cognition during abnormalities. In this Part 2, we show that the cognitive behaviors displayed by expert operators can be represented as target values on the HMM's state transitions and emission probability distributions. Further, we propose two axioms of learning that can capture the evolution of the operator's mental models as they learn the causal relationships in the process and gain expertise in handling abnormal situations. We validate the proposed axioms by conducting training experiments involving 10 participants performing 486 tasks. Our results reveal that the axioms can accurately assess the progress of operators' learning.
查看更多>>摘要：In the event of an accidental spill of an aqueous solution of ammonia, a toxic cloud can be generated, being the ammonia evaporation rate a key issue. In this communication, new experimental data have been obtained at different initial ammonia concentrations and air speeds. The evolution of the evaporation rate, of the ammonia concentration in the solution and of the solution temperature have been studied. Three phases have been clearly identified in the evaporation process, affected by the ammonia concentration, the evaporation rate and the condensation of water. A simple model has also been proposed, based on previous ones from the literature and now including the condensation of water. The proposed model has been compared with experimental data. Although some scattering has been found, it still proves itself useful at predicting the source term in the event of an accidental spill.
查看更多>>摘要：Errors and uncertainties in the input parameters can have a significant effect on the reliability, quality and safety of a chemical process. However, the majority of mathematical models use deterministic operating conditions. Therefore, to have a more realistic mathematical design, it is essential to take them into account in order to analyse how they propagate in a chemical reactor and influence the safety criteria.In this work, random variations were imposed on the input parameters of a batch chemical reactor and the impact on the system reliability was studied. An exothermic reaction of the synthesis of peroxyformic acid was chosen and the maximum temperature of this reaction was taken as a safety criterion. The case of impurity presence in the reactor was also investigated. This impurity can lead to the reactant decomposition and consequently to thermal runaway, despite the adequate setting of the operating conditions.The probability density functions (PDFs) for the reaction maximum temperature were used to estimate the system reliability. Theses PDFs were obtained by solving Latin hypercube sampling and genetic algorithm combined with the least square method. Stochastic treatment provides a more significant information concerning the reliability and highlights the nonlinearity of the process.
查看更多>>摘要：In order to study the development law of gasoline-air mixture explosion in vertical dome oil tank, a series of experiments are carried out in simulated oil tank. It is found that the development of overpressure in internal field can be divided into three stages: the overpressure rising stage, the overpressure relief stage and the overpressure oscillation and attenuation stage. The maximum overpressure peak, average overpressure rise rate and maximum overpressure rise rate in internal field all increase first and then decrease with the increase of gasoline vapor volume fraction. However, the formation time of the maximum overpressure peak, the maximum negative overpressure and the average pressure relief rate have opposite numerical trends. All of these peaked at the initial gasoline vapor volume fraction of 1.7%. The external field pressure wave of gasoline-air mixture explosion has a great relationship with spatial azimuth. With the increase of proportional distance, the pressure wave of external field at any angle shows the exponential decay law in form of Pext = kR-alpha. The relationship among the maximum overpressure peak, distance and direction can be uniformly expressed by a formula. With the increase of gasoline vapor volume fraction, the maximum overpressure peak at the nearest measurement point in the direction of dome opening increases first and then decreases, and the formation time of the maximum overpressure peak changes in the opposite trend, which can be expressed by cubic polynomials. The flame propagation of gasoline air mixture explosion can be divided into three stages: the in-tank development stage, the vent explosion stage and the free burning stage. In addition, affected by fluid instability during explosion propagation, the positive feedback mechanism makes the development of explosion more and more intense.
查看更多>>摘要：Against dust explosions, all the flammability and explosibility parameters must be evaluated following standard procedures using the 20 L and/or the 1 m(3) vessel. Previous results comparing the dust dispersion in the 20 L sphere equipped with rebound or perforated annular nozzle showed that the initial turbulence level, the dust concentration, and the feeding are affected by the type of nozzle used. In this work, a similar investigation was performed on the 1 m(3) vessel, simulating the fluid flow evolution which is obtained with the rebound nozzle. Results showed that the 1 m3 vessel equipped with rebound nozzle presents a less uniform degree of turbulence and a higher amount of dust fed, compared to the case of perforated annular nozzle. However, the greatest effect on the initial level of turbulence and turbulent combustion regime is determined by the size of the vessel and not by the type of nozzle used.
NSTL
Elsevier