Search Results (126)

The use of propylene (C₃H₆) in semiconductor manufacturing processes is increasing, and conventional 47 L cylinder supply systems are recognized as a primary source of leakage accidents associated with human error due to the need for frequent manual cylinder replacement. In this study, a Computational Fluid Dynamics (CFD)-based dispersion analysis and a preliminary accident consequence assessment—based on explicitly stated assumptions—were conducted for a gas cabinet housing a 440 L Y-type propylene cylinder. The potential for Vapor Cloud Explosion (VCE) was analyzed using a TNT equivalence model that accounts for the internal volume of the semi-enclosed cabinet. Pressure Vessel Burst (PVB) was evaluated using the Brode–Baker–Tang approach, while the fireball resulting from a Boiling Liquid Expanding Vapor Explosion (BLEVE) was assessed using the EFFECTS software. Under emergency ventilation conditions, the steady-state volume of the flammable gas cloud exceeding the Lower Flammability Limit (LFL) was calculated to be 6.9 m³, representing less than 0.2% of the total indoor volume. The distance corresponding to an overpressure of 1 psi was estimated to be 12.0 m for PVB and 13.6 m for VCE. Additionally, assuming that the entire 185 kg inventory participates in fireball formation, the distance corresponding to a radiant heat flux of 5 kW/m² was calculated to be 104 m. However, this distance represents an upper bound solely with respect to the fraction of material participating in fireball formation and does not account for other input variables in the fireball model. The presented results represent a preliminary consequence analysis based on the specified assumptions. Some of the applied assumptions are conservative; for instance, a constant leak rate and complete participation of the stored inventory in fireball formation were assumed. Conversely, the neglect of liquid pool evaporation and the assumption that vessel rupture occurs at operating pressure are not conservative approaches. The analysis indicates that, while the consequences of overpressure are confined to the immediate vicinity of the gas cabinet, the extent of thermal radiation impact depends on whether accident scenarios initiated by external fires can be prevented. These findings provide consequence-based baseline data for the design of safety systems—such as emergency ventilation, gas detection, automatic shut-off, fire suppression, and protective structures—for facilities utilizing 440 L Y-type cylinders. However, these results alone do not determine whether the installation of such facilities is acceptable from a safety perspective. Full article

Transient temperature measurement under confined extreme thermal environments requires sensors with rapid response and structural stability. Conventional thermocouples often suffer from delayed response or insufficient junction protection, leading to inaccurate characterization of local thermal loads. In this work, a ceramic embedded junction thermocouple was developed for in situ transient temperature measurement. The sensor structure was optimized by finite element simulation, and a NiCr/NiSi junction was embedded into an Al₂O₃ ceramic substrate through inorganic bonding, thermal treatment, and surface grinding. The fabricated sensor was evaluated through thermoelectric characterization, high-temperature stability testing, dynamic response measurement, and calibration. The sensor exhibited a Seebeck coefficient of 41.26 μV/°C from 300 to 1200 °C, maintained continuous output at 1200 °C for 8 h, and achieved a response time of approximately 187 μs. The maximum relative deviation was below 0.47% within 300–1000 °C. During a confined thermal nose explosion test, the sensor successfully captured transient temperature evolution and recorded a peak temperature of approximately 1289 °C. Conventional thermocouples recorded peak temperatures below 800 °C, which were approximately 40% lower than the developed sensor. The proposed sensor provides a reliable approach for localized transient temperature measurement under confined extreme thermal environments. Full article

Multi-layer composite confinement structures (MLCCSs) are critical for containing accidental internal explosions, yet conventional design methods cannot capture their three-layer load-redistribution mechanism. Based on a validated fluid–structure interaction (FSI) model, this study investigates four key parameters (the foam-concrete yield strength, interlayer thickness, inner-layer reinforcement ratio, and inner-layer thickness) under 3 and 5 kg TNT charges and develops a simplified design method for MLCCSs with a foamed-concrete interlayer under internal blast. The foam yield strength is found to be the most critical parameter controlling the Mode I/II transition: increasing it reduces the inner-layer displacement but increases the risk of premature outer-layer yielding, challenging the conventional “stronger-is-better” design philosophy and establishing both upper and lower bounds for the foam yield strength. The method is derived from a rigid–plastic inner-layer model and the load-controllability mechanism of the foam interlayer, yielding closed-form expressions for the inner-layer maximum displacement, the minimum required interlayer thickness, and the outer-layer peak hoop strain. The inner-layer maximum displacement is quantitatively validated, with a mean absolute error of 9.50%, while the three remaining outputs are checked for consistency with the numerical results; because the Mode I/II threshold is calibrated from the same numerical dataset, this consistency check is an internal self-consistency test rather than an independent validation of the strain prediction. A step-by-step design procedure incorporating the Mode I/II criterion is proposed and demonstrated on a prospective design example whose configuration is not among the calibration cases. The study provides a rapid screening tool for the preliminary design of MLCCSs. Full article

Wood dust poses fire and explosion hazards in wood-processing and biomass-handling facilities, but its behavior varies with material properties and operating conditions. This review develops a framework linking particle-scale conversion processes with industrial accident pathways and protection strategies. It distinguishes stand-alone smoldering and flaming fires, direct dust-cloud ignition, flash fires, confined deflagrations, and secondary explosions. Lignocellulosic pyrolysis, volatile combustion, and char oxidation are examined in relation to ignition delay, flame propagation, and pressure development. Ignition and explosion parameters, including minimum ignition energy, minimum ignition temperature, minimum explosible concentration, limiting oxygen concentration, maximum explosion pressure, and deflagration index, are evaluated alongside the effects of wood composition, particle-size distribution, moisture, turbulence, and confinement. For example, increasing the tested Pinus massoniana dust particle-size fraction from 0–63 to 250–500 μm reduced the maximum explosion pressure (P_max) from 7.56 to 6.80 bar and the deflagration index (K_st) from 129 to 59.2 bar·m·s⁻¹, illustrating the greater particle-size sensitivity of K_st in that study. Such results remain material- and test-dependent and do not establish universal wood-dust design values. Prevention and mitigation measures are assessed through risk-based selection of source control, inerting, venting, isolation, and suppression. Computational fluid dynamics applications are critically examined in terms of model assumptions, validation, and engineering applicability. Throughout the review, wood-dust-specific findings are distinguished from woody-biomass and other analog evidence. Major gaps remain in quantitative links between composition and explosion behavior, transitions between fire and explosion pathways, and industrial-scale validation of suppression and numerical models. Addressing these gaps would strengthen scenario-specific protection of dust collectors, conveying ducts, dryers, and silos. Full article

Fine coal dust generated by coal and gas outbursts is difficult to wet, readily resuspended, and capable of contributing to secondary explosions during emergency rescue. A biomass-based composite comprising pectin extracted from citrus residues, sodium alginate, sodium phytate, rhamnolipid, sodium carboxymethyl cellulose, and citric acid was developed and optimized using a Box–Behnken design. The resulting local optimum within the investigated design space (OPT; 2.15% total active components) exhibited an equilibrium surface tension of 36.2 ± 0.72 mN·m⁻¹ and a mean loose-dust wetting time of 56.6 ± 13.7 s, compared with 75.4 ± 13.1 s for the practically applicable 0.80% SDBS/APAM reference. An additional 2.15% SDBS/APAM formulation retained a similar equilibrium surface tension (34.2 mN·m⁻¹) but exhibited a markedly elevated apparent viscosity (587.5 mPa·s), showing that equal-solids matching produced a substantially different rheological condition. Under stepwise exposure to 3–15 m·s⁻¹, the fully dried OPT layer showed only 1.2% cumulative wind erosion after 35 min; an independent 15 m·s⁻¹, 30 min validation using fresh specimens yielded 2.3 ± 0.3% mass loss. In 20 L explosion tests, OPT reduced the maximum explosion pressure from 0.709 ± 0.017 to 0.609 ± 0.016 MPa and the maximum pressure-rise rate from 11.39 ± 0.45 to 3.90 ± 0.25 MPa·s⁻¹. Because the electronic igniter energy was not independently calibrated, these explosion parameters and the apparent deflagration index are interpreted only as relative measures under the present apparatus conditions and are not used for formal St-class assignment. FESEM, EDS, and representative-spectrum Raman analyses were consistent with particle aggregation, surface retention of Na/P-containing material, and altered post-explosion carbon-framework evolution. These observations support a proposed multistage pathway involving pre-ignition particle connection and possible condensed-phase participation, while the specific phosphorus-containing products and individual component contributions remain unresolved. The study therefore provides an integrated evaluation of field-collected outburst coal dust from wetting and dry-state stabilization to confined-vessel explosion mitigation. Full article

The deployment of autonomous haulage systems and battery electric vehicles represents a promising pathway to decarbonizing the extractive industry while mitigating severe occupational hazards. This study investigates a 40-year historical dataset (1984–2024) from the U.S. Mine Safety and Health Administration across the stone and sand and gravel sectors to establish baseline injury trajectories and evaluate the safety impacts of fleet electrification and automation. Predictive and probabilistic modeling shows that removing onboard drivers achieves a net fatal risk reduction between 58% and 92%, even after incorporating emerging high-power battery charging hazards. However, haulage automation reconfigures shift dynamics without inherently eliminating ground-level hazards; residual non-fatal frequency rates depend critically on daily task reallocation across manual handling and auxiliary ground logistics. Furthermore, semi-quantitative assessment confirms a critical risk migration toward high-voltage maintenance (R = 12) and confined underground charging (R = 12), where thermal runaway off-gassing elevates explosion risks. Maximizing the safety benefits of autonomous electric haulage requires shifting safety governance from driver training to advanced high-voltage protocols, sensor maintenance and dedicated ventilation standards. Full article

This study addresses the challenges of slow attenuation and significant hazards associated with explosive shock waves confined within conventional underground tunnel walls. A novel serrated passive shock-attenuating tunnel design is proposed, grounded in the principle of viscous dissipation within the boundary layer. The investigation encompasses both experimental analyses and numerical simulations. The study found that shock waves in smooth tunnels primarily propagate as one-dimensional plane waves, resulting in concentrated energy and gradual attenuation. Conversely, the serrated tunnel geometry generated a continuous reflection, scattered and vortex formation due to abrupt geometric discontinuities, led to distortion and fragmentation of the shock front and the emergence of a three-dimensional discrete pressure field. Through turbulent dissipation mechanisms, energy is rapidly transformed into small-scale vortices, effectively reducing wave velocity and markedly diminishing the forward peak pressure. Under conditions of high-equivalent explosions, the serrated structure demonstrates enhanced efficacy in energy dissipation and peak pressure attenuation, significantly curtailed the effective propagation distance of high-pressure shock waves. Optimization of the serration spacing identified 30 cm as the optimal interval, minimizing stress peaks both centrally and at the tunnel entrance, thereby maximizing wave attenuation. Comparative analysis between simulation and experimental was resulted that corroborates the wave-attenuation performance of the serrated design, offering a critical foundation for the development of blast-resistant underground structures. Full article

Safety monitoring and visual surveillance in underground coal mines must cope with extreme low light and pervasive coal dust, yet the most accurate low-light image enhancement models rely on self-attention, whose quadratic cost precludes real-time use on the edge-computing platforms deployed underground, such as inspection robots and explosion-proof cameras. Our key observation is that these two degradations are separable by a wavelet decomposition: the low-frequency band carries the illumination to be corrected, whereas dust-induced noise is largely confined to the high-frequency bands. MineSSM turns this observation into an efficient design that routes each band to the operator it needs: a linear-complexity state-space model (Mamba) that homogenizes the global illumination and a lightweight convolutional branch that performs dust suppression on the high-frequency bands, so that no heavy operator ever runs at full resolution, and the two branches are recomposed under a Retinex constraint for faithful color restoration. A frequency-domain analysis of a real dusty mining frame confirms this split, with the smooth veil and lamp glow in the low-frequency band and the discrete dust speckles in the high-frequency bands. MineSSM surpasses the Transformer-based MEFormer on the MELOL mining dataset (26.58 dB PSNR/0.96 SSIM vs. 26.34 dB/0.91 SSIM) and attains the best PSNR and SSIM on the LOLv1 benchmark, while running at 27.8 FPS (0.036 s per $400\times 600$ image) on a desktop GPU with linear resolution scaling. On an embedded NVIDIA Jetson Orin NX it sustains 8.0 FPS at $400\times 600$, supporting near-real-time on-device enhancement at typical surveillance resolutions. Full article

Gas explosions bring severe hazards and threats to coal mine safety. To prevent such explosions and mitigate their consequences, research on the mechanism of gas explosions and isolation-suppression technology has been conducted using theoretical analyses, experimental studies, and numerical simulation methods, etc., and various isolation-suppression explosion materials (technologies) have been developed. The mechanisms of gas explosions and their isolation-suppression explosion are summarized in this paper, and the current research status of isolation-suppression materials (technologies) of gas explosions is reviewed from the perspectives of gas-phase, liquid-phase, and solid-phase isolation-suppression explosion, wall materials, and multi-phase synergistic isolation-suppression explosion. The results indicate that current studies on gas explosion mechanisms, isolation-suppression explosion mechanisms, and related technologies have been extensively conducted, resulting in significant achievements, some of which have already been integrated into the theoretical framework and technological applications of isolation-suppression explosion of gas explosions. However, due to the specific nature of gas explosions and variations in explosion environments, the effectiveness of existing isolation-suppression measures has not yet reached the desired level, particularly in the case of single-phase isolation-suppression explosion materials (technologies). Although multi-phase synergistic isolation-suppression explosion materials (technologies) have shown significant advantages, their effectiveness is not only influenced by various factors in single-phase materials (technologies), but is also constrained by the synergistic effects among different factors. Therefore, it is necessary to further investigate the optimal synergistic relationship among multiple factors. This review is expected to provide valuable references for promoting the development of isolation-suppression explosion materials (technologies) for gas explosions and their disaster prevention in confined spaces. Full article

This study demonstrates that supercritical carbon dioxide phase-change fracturing technology can reduce acute pressure-related injury potential compared to conventional explosives in underwater reef clearance operations along the Yangtze River. Employing a stepwise “pipe test, numerical simulation and engineering application” framework, a novel rock–water–fish coupled HJC–Gruneisen elastoplastic model was established to simulate cross-medium shock wave attenuation processes. The supercritical CO₂ shock wave exhibits characteristics of “low peak overpressure (13% of equivalent explosives) and long duration (6–7 times longer than conventional explosives),” attenuating in water with a power-law index α = 0.717. A dual-parameter “resistance line (intact rock buffer between the fracturing tube and the rock–water interface)–water depth” correction model indicates that the resistance line reduces peak overpressure by 18.6%, while each 10 m increase in water depth enhances attenuation by 60.6%. The preliminary engineering critical safety threshold for 30 cm silver carp (indicated by swim bladder rupture) is 0.20 MPa. Based on the representative engineering scale of the Chaofu Waterway Regulation Project, characterized by water depths of approximately 6–16 m and a resistance-line-controlled buffer condition, a theoretical safety distance model R_safe was also derived. Under these engineering constraints, the application results indicate that the lethal zone was confined to 7.5–9.9 m, enabling precise lethal-injury-safe zoning. This work establishes a fish injury threshold and safety assessment system for supercritical CO₂ subaquatic fracturing, providing direct green guidelines for Yangtze River navigation projects. Full article

Very large-scale biogas (biomethane) projects are important infrastructure systems for integrating organic waste treatment, renewable energy substitution, and carbon mitigation under China’s carbon peaking and carbon neutrality goals. However, their long process chains, concentrated hazardous media, and frequent confined-space operations create coupled safety risks that may undermine sustainable operation. To identify the dominant risk drivers and safety governance priorities, this study investigated five operating very large-scale biogas projects in Shanxi Province, China. On-site inspections, semi-structured interviews, and document reviews were used to identify ten safety-risk causative factors. The Decision-Making Trial and Evaluation Laboratory (DEMATEL) method was combined with Interpretive Structural Modeling (ISM) to quantify causal relationships and reveal the hierarchical transmission structure among the factors. The results show a structural imbalance between document-based compliance and operational implementation. Although basic safety documents were generally established, only 20% of the projects had scenario-specific emergency response plans for major accident scenarios; the compliance rate of explosion-proof electrical equipment, the configuration rate of fixed monitoring and alarm systems for combustible and toxic gases, and the effective operation rate of forced ventilation facilities were 40%, 60%, and 40%, respectively. Insufficient enterprise safety investment (M1) and unclear external regulatory responsibilities (M2) were the dominant root causes of system-level risk propagation, while inadequate control of high-risk operations (M9) and unsafe worker behavior (M10) were the final manifestations. A four-pillar governance pathway is proposed, including policy and standard improvement, technological support and equipment upgrading, personnel capacity enhancement, and sustainable funding mechanisms. The findings provide empirical evidence for risk-based supervision and indicate how operational safety governance can serve as an enabling condition for the long-term sustainability of the biomethane industry, rather than as a direct measurement of carbon-mitigation or energy-performance outcomes. Full article

Pulverized coal explosions pose significant hazards during pneumatic conveying and handling in coal preparation and mining. To investigate flame propagation and pressure evolution under conditions representative of vertical conveying pipelines, explosion experiments were conducted using pulverized coal with defined particle sizes and dust concentrations. Flame propagation and pressure dynamics were synchronously captured via high-speed imaging and dynamic pressure measurements. Results showed that flame height exhibited a Logistic growth pattern, whereas flame propagation velocity followed an inverted parabolic trend, reaching a maximum value of 14.5 m s⁻¹ at approximately 20 ms after ignition. Significant flame-front wrinkling, distortion, and oscillatory propagation were observed during explosion development, reflecting increasingly complex flame evolution within the confined vertical pipeline. Increasing dust concentration from 0.3 to 0.5 kg m⁻³ promoted flame acceleration and pressure development. For 45 μm particles, the maximum explosion pressure increased from 0.710 to 0.948 MPa. At a constant concentration, decreasing particle size enhanced both flame propagation and explosion severity. Under 0.5 kg m⁻³, the maximum pressure increased from 0.788 MPa for 200 μm particles to 0.948 MPa for 45 μm particles. The enhanced explosion intensity at higher concentrations and smaller particle sizes is attributed to accelerated heat and mass transfer together with more efficient combustion under confined conditions. These findings provide new insight into the coupled evolution of flame propagation and pressure development and contribute to explosion risk assessment in pulverized coal conveying systems. Full article

On 14 February 2025, the outer cladding of the Chornobyl New Safe Confinement (NSC) was damaged by an explosion caused by a one-way attack unmanned aerial vehicle (UAV), creating a hole of about 15 m in diameter and requiring about 300 penetrations to be made in the cladding during firefighting. This created an urgent need to assess radiation dose rates above damaged areas to support repair planning and worker radiation protection. This study presents a UAV-based survey of the equivalent gamma dose rate distribution above the damaged northern side of the NSC outer cladding. The survey used a bespoke system, integrating a multirotor UAV, an AccuRad Personal Radiation Detector (PRD), onboard data acquisition and transmission modules, and ground-based and server-side analytical components. Measurements were performed under real post-incident field conditions, including restricted flight zones, wind-induced turbulence, proximity to large metallic structures, and electronic warfare interference. The dataset was filtered for Global Positioning System (GPS) reliability, transformed into a metric coordinate system, and processed for spatial interpolation and mapping. The resulting distribution showed a spatially non-uniform radiation field: the main damage zone had relatively low equivalent gamma dose rates, whereas the highest values, up to 1092 μSv/h, were recorded over areas of the NSC closest to the Shelter Object. The study demonstrates UAV-based radiation mapping of a damaged large-scale confinement structure and provides data supporting Chornobyl Nuclear Power Plant repair planning. Full article

The containment of internal explosions remains a critical challenge in the design of protective infrastructure for ammunition storage and hazardous industrial facilities. To address the limitations of conventional single-layer reinforced concrete (RC) structures, this study proposes a multi-layer composite confined structure comprising RC layers and energy-absorbing interlayers. A fluid–structure interaction (FSI) numerical model was developed and validated against experimental data from scaled blast tests on two multi-layer composite confined structures reported in our companion study. Comparative analyses were performed between the composite structures and an equivalent single-layer RC structure under varying charge masses. The results indicate that the energy-absorbing layer transforms the monolithic structural response into a progressive, layer-by-layer deformation mode, effectively decoupling the outer layer from the direct blast impulse. Foamed concrete demonstrated superior performance by limiting the transmitted stress to its yield plateau (~1.0 MPa) and reducing the outer-layer energy to 8.77% of that in the single-layer structure. Two distinct failure modes were identified for the first time: the desired Mode I, where the inner layer reaches its deformation limit while the outer layer remains elastic, and the undesired Mode II, characterized by premature plastic failure of the outer layer. These findings provide a rational basis for the design of blast-resistant composite structures, highlighting the efficacy of foamed concrete in ensuring containment integrity. Full article

Explosion venting is widely used to limit overpressure in confined systems, although its effectiveness depends on complex interactions between combustion, flow, geometry and external conditions. This review examines the phenomenology of vented hydrogen explosions, the main parameters governing their severity, recent experimental and numerical advances, and current design standards. The literature shows that hydrogen concentration, ignition position, vent characteristics, congestion, enclosure geometry and scale affect not only the maximum overpressure, but also the sequence and physical origin of the pressure peaks. Experimental studies highlight the importance of external cloud combustion, flame-acoustic coupling and obstacle-induced turbulence, while CFD models can reproduce overall pressure and flame-propagation trends but remain sensitive to modelling assumptions and validation conditions. Existing standards, particularly EN 14994:2007 and NFPA 68:2023, provide a valuable basis for preliminary design and engineering practice, although additional assessment may be required for highly reactive mixtures, congested layouts and non-standard geometries. Further large-scale testing, benchmark validation and integrated experimental-numerical approaches are needed to improve the reliability of explosion-venting design for hydrogen applications. Full article