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About the Journal
Superintended by：China North Industries Group Corporation Limited
Sponsoredy：Beijing Institute of Technology, Chinese Scoiety for Environmental Sciences, China Occupational Safety and Health Association
Edited & Published by: Editorial Department of Journal of Safety and Environment
Issues per year: 12
ISSN 1009-6094
CN 11-4537/X
Failure risk assessment of dry tree cylindrical FPSO Christmas tree in complex scenarios based on the DBN-IT2FS model
Li Xinyi;Hu Jinqiu;Zhang Laibin;Ma Mingjun;Xu Xin;To comprehensively analyze the failure risks of Christmas trees in complex production-storage-offloading scenarios aboard cylindrical dry-tree Floating Production Storage and Offloading(FPSO), this study introduces a key risk assessment model for Christmas tree failures based on the Dynamic Bayesian Network(DBN)-Interval type-2 Fuzzy Sets(IT2FS) method. This approach addresses the limitations of traditional risk assessment methods in managing data uncertainty and dynamic predictions. The paper innovatively employs the IT2FS method combined with an improved similarity aggregation technique to derive prior probabilities for root nodes, thereby minimizing subjectivity in the determination of these probabilities. Additionally, the Weibull distribution is utilized to characterize the state transition probabilities of dynamic nodes as they undergo degradation over time, aligning closely with actual equipment deterioration patterns and enhancing the accuracy of dynamic failure probability predictions. Conditional failure probabilities for non-root nodes were computed using Noisy-OR gates, which helped to reduce data requirements and simplify statistical inference. The vulnerability model quantified the propagated failure probabilities of risk-coupled nodes—such as thermal radiation, shock waves, and physical debris—while thoroughly accounting for potential domino effects from accidents. This methodology significantly enhances the accuracy of dynamic failure probability predictions and facilitates a more comprehensive identification of risk factors. DBN analysis revealed an initial failure probability of 5.644 6×10-5 for the Christmas tree, which increased to 5.736 5×10-6 after ten years of operation. Both values are classified within low-risk categories, demonstrating an evolution pattern characterized by a “significant increase followed by stable operation.” Simultaneously, key failure risk factors were identified, including safety interlock failure, riser system malfunction, instrumentation failure, pressure sensor failure, and solenoid valve sticking. In response to these critical risks, this paper discusses various risk control measures encompassing design improvements, assembly practices, periodic maintenance, and specialized environmental considerations. These measures serve as valuable decision-making references for ensuring the normal operation of the Christmas tree and mitigating risks in complex scenarios. This methodology not only provides accurate predictions of failure probabilities but also facilitates a comprehensive identification of risk factors. It reveals the temporal evolution of failure probabilities while pinpointing key risk factors associated with tree failures in complex scenarios and proposing effective control measures.
Safety evaluation of flotation reagents for oxidized ores based on an AHP-EWM-FCE model
Bu Xianzhong;Sun Shuwen;Wang Yonghai;Sun Jian;Wu Hao;Duan Zhiyi;Ai Xiaozong;The safety performance of flotation reagents is closely linked to the ecological sustainability of mining areas and the occupational health of workers. As mineral resources become increasingly complex and the use of flotation reagents expands, potential environmental and health risks have garnered significant attention. However, conventional safety evaluation approaches are often limited by insufficient consideration of toxicological factors and a lack of systematic quantitative indicator frameworks, which hinders the development of green and sustainable mineral processing technologies. To address these limitations, this study proposes a multi-criteria safety evaluation model that integrates the Analytic Hierarchy Process(AHP), Entropy Weight Method(EWM), and Fuzzy Comprehensive Evaluation(FCE). Based on internationally recognized chemical risk classification standards, a safety indicator system comprising ten key indicators was established across three dimensions: human health hazards, environmental risks, and chemical stability. This system enables a comprehensive characterization of potential risks associated with flotation reagents during their production, application, and disposal. To ensure scientific rigor and objectivity in weight determination, a combined weighting strategy was employed. Subjective weights were derived using AHP based on expert judgment, while objective weights were calculated with EWM according to the information entropy of the evaluation data. These weights were integrated to obtain final comprehensive indicator weights. Subsequently, the FCE model was applied to calculate fuzzy membership degrees for fifteen typical ilmenite flotation reagents and classify their overall safety risk levels. Results indicate that fatty acid collectors and organic depressants exhibit higher safety performance, characterized by lower toxicity and reduced environmental persistence. In contrast, phosphonic acid and arsenic-containing reagents present significantly higher safety risks due to pronounced toxicity, poor degradability, and potential long-term environmental impacts. These findings highlight clear differences in the safety profiles of commonly used ilmenite flotation reagents. Overall, the proposed AHP-EWM-FCE model provides an objective assessment of flotation reagent safety risks, supporting rational reagent selection, effective environmental risk management, and the promotion of sustainable mining practices for oxidized mineral flotation, such as ilmenite.
Effectiveness of high-pressure water mist for suppressing full-scale cable tunnel fires
Yan Long;Wang Junyi;Xu Zhisheng;Li Xin;Li Qi;To ensure fire safety in cable tunnels, this study employed a cone calorimeter and a full-scale cable tunnel test to analyze the combustion characteristics of cable fires and the progression of fires within the tunnel. It also examined the impact of a high-pressure water mist system on fire temperature, gas volume fraction, and extinguishing time. The results indicate that the cable combustion process exhibits typical bimodal heat release characteristics, with cable spacing significantly influencing fire risk. When the cable spacing is 1.5 times the cable diameter, the rate of fire spread is at its highest, resulting in an increased fire risk. The evolution of a cable tunnel fire can be categorized into three stages: ignition, stable combustion, and decline, with longitudinal temperatures within the tunnel reaching up to 695 °C. The high-pressure water mist system effectively suppresses cable tunnel fires, demonstrating that its fire control efficacy is positively correlated with both the nozzle flow coefficient and the fine water mist pressure. Additionally, these two parameters exhibit systematic differences in their fire suppression mechanisms. The nozzle flow coefficient primarily contributes to fire suppression through cooling and smothering effects, while fine water mist pressure affects atomization efficiency and kinetic penetration. However, it was found that when the fine water mist pressure is set at 10 MPa with a nozzle flow coefficient of 0.5, the high-pressure water mist system fails to extinguish the cable tunnel fire. When the nozzle flow coefficient is increased to 1.0 or higher, the system proves effective in extinguishing cable tunnel fires. Specifically, at a nozzle flow coefficient of 1.0, raising the water mist pressure from 7 MPa to 13 MPa significantly reduces the fire extinguishing time. The high-pressure water mist system, configured with a flow coefficient of 1.0 and a water mist pressure of 13 MPa, achieves the best overall fire extinguishing performance, with the fire extinguishing time reduced to just 250 s.
Research on the key smoke exhaust volume of tunnel fires under the synergistic effect of water mist curtains
Jiang Xuepeng;Tong Boyu;Li Haowu;This study aims to explore the critical operating parameters for effective smoke control through the synergistic application of water mist curtains and key smoke exhaust systems in tunnel fires. The primary objective is to establish a quantitative relationship among smoke exhaust volume(E), total water mist curtain flow rate(q), and fire source power(Q) under critical conditions. First, a theoretical analysis was conducted based on the π theorem, leading to the derivation of a dimensionless relationship. To verify and quantify this relationship, numerical simulations were carried out using the Fire Dynamics Simulator(FDS). The physical model represented a 1 200-meter-long underwater tunnel with a rectangular cross-section(14 m wide and 6 m high). A uniform grid size of 0.4 m×0.4 m×0.4 m was utilized to balance calculation accuracy and efficiency. Simulations encompassed nine fire scenarios with power levels ranging from 10 MW to 50 MW, and three series of working conditions were designed:(1) Series A: fixed initial nozzle flow rate(120 L/min) with varying smoke exhaust volumes;(2) Series B: fixed critical smoke exhaust volume(determined by analysis) with varying nozzle flow rates;(3) Series C(50 MW only): water mist curtain turned off with varying smoke exhaust volumes as a control group. Clear critical performance criteria were defined: the critical smoke exhaust volume is the minimum volume that satisfies two conditions simultaneously: maintaining visibility ≥10 m at the critical personnel height(2.2 m above ground) in all tunnel areas except near the water mist nozzles(where visibility reduction from droplets is unavoidable), and achieving smoke exhaust efficiency ≥90%(calculated by the ratio of exhausted to generated CO2 mass flow rates). The critical nozzle flow rate is defined as the minimum flow rate per nozzle needed to completely prevent smoke penetration, determined by monitoring CO2 concentration(maintained at ambient levels) in the immediate area downstream of the water mist curtain. Results identified optimal combinations of critical E and q for each fire power level. Nonlinear regression analysis of the dataset(E, q, Q) yielded a quantitative relationship q/E=1.3×10-4×Q*-0.4 with a goodness of fit R2=0.96, confirming the theoretical dimensionless relationship. This derived formula provides reliable quantitative support for the design and dynamic regulation of coordinated water mist curtain and smoke exhaust systems in tunnels.
Fire prediction and prevention optimization for mountainous tourist cities based on deep learning
Wu Yunfa;Cheng Yuqi;Chen Sarula;Li Shuying;To strengthen fire prevention in mountainous tourist cities, this study proposes a systematic prevention and control method that integrates fire prediction with prevention optimization. Huangshan City, a renowned tourist destination in China characterized by over 50% mountainous terrain and frequent fire risks associated with tourism activities, was selected as a case study. A comprehensive dataset was constructed by integrating fire hotspot data from the Moderate-resolution Imaging Spectroradiometer(MODIS) with multi-source geospatial data, including meteorological, topographic, vegetation, and urban planning information. Two deep learning models—a Convolutional Neural Network(CNN) and a Long Short-Term Memory(LSTM) network—were developed to perform spatiotemporal predictions of fire occurrence probability at a spatial resolution of 1 km × 1 km and on a daily temporal scale. Model performance was evaluated using multiple metrics: accuracy, precision, recall, and the Area Under the Receiver Operating Characteristic Curve(AUC-ROC). The LSTM model significantly outperformed the CNN model, achieving an accuracy of 88%, a precision of 87%, a recall of 90%, and an AUC-ROC of 0.95, demonstrating its superior suitability for fire prediction in the study area. Sensitivity analysis of the driving factors revealed that daily maximum temperature was the key driver of fire occurrence, contributing 35.2%, while wind speed had a relatively minor impact, contributing only 8.7%. This pattern differs significantly from those observed in urban areas. Using Geographic Information System(GIS) spatial analysis, the fire risk sensitivity of Huangshan City was quantified and zoned, revealing a distinct pattern of higher risk in the central-western regions and lower risk in the northern and southern areas. Subsequently, a location-allocation model was employed to optimize the layout of fire stations with the goal of maximizing fire emergency coverage within a 5-minute response time. The optimized layout scheme recommends retaining 5 existing fire stations and adding 23 new stations in high-risk and underserved areas. Verification of the optimized scheme indicates that the overall fire emergency coverage rate for Huangshan City increased from 59.27% to 80.53%. By integrating qualitative and quantitative fire risk analyses, this method effectively enhances the scientific foundation for pre-disaster prevention and improves the efficiency of post-disaster emergency response in mountainous tourist cities.
