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Underground mining remains one of the most dangerous occupations in the world, and coalmining is known for its high accident rates. In this paper we aim to present an overview of safety in the extractive industry and we will present statistics on known accidents. The repeated occurrence of explosions in underground mining raises questions about the measures taken to prevent their occurrence. Hazard identification and risk analysis are necessary to identify adverse events that may lead to a hazardous situation, to analyze the mechanism by which this adverse event may occur and usually to estimate the magnitude and likelihood of effects.

According to ANSYS - developer of the Multiphysics platform for computer simulations - the FSI (Fluid-Structure Interaction) model can be used in all cases where a fluid encounters a solid structure, for example, wind gusts rotating a turbine, air washing the surface of a moving car etc. This method finds applications especially in the aeronautical and automotive industries, but also in medical research, such computer simulations track the influences of blood pressure and blood flow velocity in the veins. This paper deals with an extension of applying this method in a lesser field, namely in investigating gas explosion events through computer simulations. For this, in the virtual domain, a geometry similar to a house was built, in which an explosive atmosphere generated by an accidental natural gas leak was simulated. Following the source of initiation, the process of rapid combustion of combustible gas takes place, the dynamic effects produced by the pressures generated by the expansion of the gases being calculated and quantified by the FSI model. The results obtained by applying this method in the simulations help in the decision-making process to adopt the most effective measures to prevent explosion-type events of air-fuel mixtures, being useful in the development of explosion risk assessment studies, for identifying the worst-case scenario.

Given the possibilities offered by PIV systems, it was considered appropriate to test them in the study of the formation of explosive atmospheres. In this sense, within the INCD INSEMEX Petroșani laboratories, a test stand was created subject to the conditions of applying PIV techniques. Thus, this stand was built of transparent materials, having the possibility to introduce, in the inner volume, the suspended particles and the combustible gas, being at the same time able to be sectioned by the light plane generated by a laser source and to provide the recording conditions using a CMOS camera. The physical experiments concerned both the situation of a normal atmosphere inside the test stand and the situations of the appearance of a fuel gas leak and an efficient source of initiation of the formed explosive atmosphere.

The presence of a flammable gas in a combustible dust cloud significantly modifies its explosivity parameters. Thus, a hybrid mixture can become flammable even when both the dust-air and gas-air binary mixtures are under the corresponding lower explosion limits. The pressure-time histories of hybrid mixtures formed by coal dust, methane and air at different concentrations, at 1 bar initial pressure and normal temperature, were studied using the standard 20 L spherical explosion vessel and 5kJ chemical igniters or 10 J permanent sparks. From the early stages of the pressure-time history, when the pressure increase is equal to or less than the initial pressure, the normal burning velocities were evaluated and discussed.

Methane is one of the most common gaseous fuels that also exist in nature as the main part of the natural gas, the flammable part of biogas or as part of the reaction products from biomass pyrolysis. In this respect, the biogas and biomass installations are always subjected to explosion hazards due to methane. Simple methods for evaluating the explosion hazards are of great importance, at least in the preliminary stage. The paper describes such a method based on an elementary analysis of the cubic law of pressure rise during the early stages of flame propagation in a symmetrical cylindrical vessel of small volume (0.17 L). The pressure–time curves for lean, stoichiometric and rich methane–air mixtures were recorded and analyzed. From the early stages of pressure–time history, when the pressure increase is equal to or less than the initial pressure, normal burning velocities were evaluated and discussed. Qualitative experiments were performed in the presence of a radioactive source of 60Co in order to highlight its influence over the explosivity parameters, such as minimum ignition energy, maximum rate of pressure rise, maximum explosion pressure and normal burning velocity. The results are in agreement with the literature data.

Fire and explosion prevention requires the knowledge of the explosive or flammability parameters of combustible gases and vapours that can be found in industrial and civil environments, as well as the influence of certain substances in the process on these parameters. In some cases, pyrophoric sulphides can be formed and it is supposed that they may influence the known flammability parameters of the substances used in various industrial processes. In order to track the influence of iron sulphides on the flammability parameters of liquids, determinations of these parameters (flash point and auto-ignition temperature) were made for a series of flammable liquids that have been contaminated with various quantities of commercial iron sulphide.

The current paper is an overview on previous and ongoing research carried out by the authors concerning the use of Computational Fluid Dynamics for the accurate classification of hazardous Ex areas generated by flammable gases, for the optimization of computational simulation of air-methane mixture explosions by using ANSYS CFX and FLUENT and for calibrating computational simulations of gas explosions using the Schlieren effect. These research works containing analytic studies have led to the observation of basic principles which come to support the benefit of computational approaches for estimating gas dispersion within technological installations in which are handled or stored flammable materials and in which there are likely to occur explosive atmospheres. Preliminary results have led to the idea of developing a computational method for assessing the hazardous area extent in case of gas leak explosions in confined spaces. The computational method intended to be developed has to be validated in the lab using an experimental chamber as domain for analysing accidental flammable gas leaks from transportation installations and for studying the formation, ignition and burning of air-flammable gas mixtures in confined spaces. Results obtained from physical experiments will be used for calibrating the mathematical models. Further, verification and validation of computational simulations carried out based on physical experiments will be performed by a comparative analysis of virtual results with the experimental ones. In the end, the mathematical model will be implemented on a small-scale reproduction of a confined industrial area with explosion hazard.

For assessing the intrinsic safety to mechanical sparks, two dedicated methods are implemented in testing laboratories and further used for the conformity assessment of products with regard to explosive atmospheres ignition, namely: impact test and friction test. The purpose of the article is to present the results obtained by using the first method mentioned, results which shall be applied in further research for comparison with the ones resulting from the friction test. The article presents the process for developing the research facilities used for testing activities in the field of non-electrical equipment intended to be applied in potentially explosive atmospheres. Also, the paper highlights important aspects on non-sparking tools used to carry out the specific maintenance works within technical installations located in hazardous Ex areas, in compliance with the European workplace safety and health principles and practices. Theoretical and practical studies, laboratory research, assessment methods and tests for determining the ignition hazard by mechanical sparks generated by non-electrical equipment are developed in order to improve the performance of the actual testing system for the assessment and testing of non-electrical equipment intended for use in atmospheres with explosion hazard. The development of the test method for non-sparking materials and the test setup ensures the optimal performance of the tests required for carrying out the conformity assessment process for equipment and non-sparking tools intended for use in potentially explosive atmospheres, taking into consideration the provisions of international regulations in force.

At the underground mining works performed in coal, rock and mixed coal & rocks, the process applied almost exclusively is by drilling & blasting. Given that the mines in the Jiu Valley are classified as methane mines, this involves the use of explosives and means of initiation that are safe from methane gas and coal dust. To date, permissible powdered explosives have been widely used. The drilling & blasting patterns were established according to the physical - mechanical and geological characteristics of the rocks in the massif, the type and section of the mining works as well as the restrictions imposed by the methane regime of the mines. In recent years, the widespread use of emulsion explosives has led to the development of permissible types of emulsion explosives. In order to use the permissible emulsion in the coal mines in the Jiu Valley, it was necessary to test in the INSEMEX landfill the safety and functioning parameters as well as to perform underground blasts, in the specific conditions of the methane coal mines. The paper describes the underground experimental blasting works performed, as well as technical and safety recommendations for the use of this type of explosive - permissible emulsion.

Based on the experience accumulated over time on the evaluation of equipment and installations in environments with potentially explosive atmospheres, this paper is intended to be an element of synthesis on issues related to the “in situ” assessment and solutions of solvency the deficiencies found. The assessment of these installations is very important in order to verify the implementation of measures that lead to minimizing the risk of ignition of explosive atmospheres. Evaluation of these installations is made through an on-site visit and on the basis of the technical documentation developed by the care of the user. In first part of the paper were presented the legal aspects regarding the placing on the market and the use of equipment designed for potentially explosive atmospheres. The paper is continuing with the presenting the technical aspects regarding the evaluation of equipment and installations operating in potentially explosive atmospheres followed by requirements for electrical equipment. The main conclusion, of the paper is that the explosion protection of the equipment intended for use in potentially explosive atmospheres may be invalidated by the incorrect selection of the equipment, incorrect installation of the product, inadequate: performance of inspection operations, maintenance or repairing of equipment.

In the natural gas pipelines, the so-called black powder is formed. It can take many forms, including wet tarred substance or fine dry powder. Black powder occurs in both newer and older natural gas pipelines. This can disrupt the distribution of natural gas either by interrupting distribution to the customer or by reducing the quality of products delivered to customers. This residue, black powder can damage operations that take place in the transport pipelines, such as reduced inspection accuracy, erosion of the control valve and reduced flow. In addition, this powder also presents a health hazard due to the fact that it may contain pyrophoric sulphides, which require specific handling and storage procedures. Black powder is a solid contaminant found in natural gas distribution systems around the world. Drilling mud, dust, construction dirt, sand, iron oxide, iron carbonate, iron sulfides, welding slag, salt crystals, valve grease, corrosion inhibitors, and other organic materials can contribute to the formation and the presence of this residue, also called black powder. In this paper were analyzed the flammability properties of black powder collected from natural gas transmission pipelines of an operator in Romania.

When conducting a research concerning the propagation of a shock wave generated by the detonation of civil use explosives, the first thing that comes to mind should be if the detonation process takes place in an obstacle-free field, or the area has obstacles such as rocks, metals structures, wood etc, obstacles that can and will influence the final results, the shock wave curve being obturated by it. On one hand, the paper presents the experimental results obtained after the detonation of a freely suspended load, placed at 0.5m above a concrete surface. On the other hand, it compares the values of explosion pressure as shock wave, measured on 4 sensors linearly disposed at the same elevation to the ground, at a distance of 2,3,4 respectively 6 meters from the explosive charge. These values are determined through computerized simulation, using ANSYS AUTODYN software, by virtually reproducing the real scenario. Following the two experiments (real and virtual), one can conclude that computerized simulation proves to be a very useful instrument in an a priori evaluation of hazardous situations/utility of peak values for shock wave, by allowing the user to develop prevention measures/optimization of the analysed processes and also in further investigations

Explosion/fire investigation is a procedure that involves significant resources of time and activities. The most important of the basic activities performed by the investigator/investigation team is the on-site research, which, if properly performed, allows the elaboration, foundation, and verification of hypotheses, while playing a defining role in establishing the final conclusions regarding the place of initiation and cause of the event. For these types of phenomena, the on-site investigation is hampered by the damage caused by the event, making it difficult to identify footprints or traces, or by the disruptive effects of the extinguishing products used. The investigation is carried out in the area of the outbreak as well as in all the areas where the fire spread and aims to examine the fire footprint, the set of traces, objects, and materials present in the burnt area, seen in interaction, both with each other and with the surrounding space and environment. Traditional verbal or written methods of presenting evidence or traces collected at the crime scene are no longer sufficient today, as technological advances are also evident in these areas. Important benefits include the coverage of the entire crime scene, which allows for complete and efficient documentation, using spherical or panoramic photography, or the use of spatial, three-dimensional scans. This paper aims to present the important contribution made by on-site documentation activities using SceneCam Forensic imaging scanning equipment, based on a high-resolution (HDR) image capture device capable of capturing spherical, 360° x 180° images at a resolution of up to 50 Megapixels in a single scanning operation (Spheron Cam VR).

Research in the field of gas explosions has had and continues to have, as its main support, physical experiments performed on various scale models, the construction of real size models are often large consuming materials, time and labor. The rapid development of computing techniques has allowed among other things, the transfer of gas explosions research in the virtual space, for the validation of computational simulations of this type being still considered physical experiments and specialty literature. Within NIRD INSEMEX Petrosani, being an accredited institute in the elaboration of technical reports for gas explosion type events, the phenomenon of rapid combustion virtualization increased in time and as a result, computational simulations becoming an efficient tools in explaining the mechanisms of explosion production. Nevertheless, one of the problems raised by this virtualization process is the limitation of performing computational simulations in closed or partially closed spaces, initial conditions imposed, without the possibility of dynamic modification of these conditions according to the development of overpressures generated by the virtual explosion. This paper presents a computational experiment in which it was possible to transform the boundary conditions at predefined pressure thresholds, from rigid surfaces into surfaces capable of releasing the overpressures developed in closed / partially closed spaces, putting the results of this kind of simulations in line with real dynamic effects of gas explosion events.

Even though blast events in inhabited areas are characterized by a low probability of occurrence, they can present a high risk for buildings and their occupants. The means to reduce the vulnerability and prevent the progressive collapse of buildings includes large stand-offs, enhanced local strength of structural elements, and increased redistribution capacity after a local damage. Blasts are extremely complex events, especially when the charge is detonated at a small distance from the building. In such cases, the application of analytical methods may give inaccurate results. The paper presents the results of a combined experimental/numerical program, which focused on the response of steel frames to close-in detonations. Two identical specimens were tested inside a specialized bunker for different charge sizes and stand-off distances. Very similar behaviors and failure modes were observed for the two specimens. The numerical model, calibrated against test data, was able to accurately predict the deformations and failure mode of the specimens. The results of the parametric numerical study indicated that the local failure mechanism and resistance to progressive collapse of steel building frames depend very much on the blast load parameters but also on the level of gravity loads in columns.

In quarries, hard rock blasting is done effectively using explosives for civil use. Perhaps, the most used technical solution for decreasing the seismic effects due to blasting is sequential blasting in front of the quarry. This technical solution involves the use of proper means of initiating explosives, which have to meet certain characteristics able of leading to the achievement of the intended purpose. This paper describes one of the methods of verification and the testing results for non-electric initiation system components, usually used to initiate the explosives in quarries, in terms of delay accuracy , which is an essential parameter for highlighting the possibility of using these products within blasting schemes.

Diesel fuel in motion when is transporting by pipes when is mixing, pumping, filtering, agitating or by pouring them from one vessel to another can generate static charges. Also, static electricity may occur if the liquid is splashes and forms a mist inside the tank. Accumulation of static electricity can, under certain conditions, be discharge and ignite the flammable/explosive atmosphere. Ignition hazards from static discharges can be eliminated by controlling the generation or accumulation of static charges or by eliminating a flammable mixture where static electricity may be discharged. Factors that need to be considered to reduce the risk of ignition sunt flammability characteristics of explosive atmosphere (the vapor pressure, flash point, temperature, and pressure) and the factors that determine the charging of static electricity (fuel type, electrical conductivity, sulfur content, viscosity, vehicle process: flow rate, pipe diameter, filters, pumps, spark promoters). In this paper are presented some aspects regarding the technical, organizational requirements and responsibilities of the personnel designated to prevent the formation and accumulation of static electricity when loading diesel fuel tanks, starting from a case study, respectively some explosions which occurred to a company during the loading operation.

In the virtual environment, respectively in a rectangular tube with a hole at one end, a computational simulation was performed comprising two stages: the first stage aims at simulating a methane gas leak through a hole in the floor of the tube and its diffusion in the air of which the inner volume of the virtual environment is constituted. At the full end of the tube is arranged an electric ignition source that activates in parallel with the gas source, being observed the formation of the explosive mixture in the proximity of the ignition source and the moment of initiation of the explosive atmosphere. The second stage of the simulation is marked by a higher level of velocities characteristic of the explosive process of the airmethane mixture, which involves the use of different settings. The host of the computer simulation is the Fluent application of the ANSYS platform. Post-processing is performed both on the ANSYS platform, through the Fluent and Results applications and through the facilities offered by the Tecplot 360 application.

Hazardous substances are considered to be liquids, gases or solids which are of risk for the health and safety of workers and they may be found in almost all workplaces, including in SME’s. Hazardous substances include chemical agents, but also biological ones, such as bacteria, viruses, mould etc. Most chemicals used in the industry present risk for the workers, depending on their physico-chemical properties. Directive 2012/18/EU is the legal act which regulates the chemical substances field within the Member States, regulation dealing with the control of hazards involving dangerous substances which may lead to major accidents. In Romania, Law 59 dated April 2016 on controlling the hazard of major accidents caused by hazardous substances evaluates “hazardous chemicals”, describing the risk for people and regulating concentrations of such substances. By using the commercially available Phast consequence modelling package, within this study were modelled leaks of several chemical substances used in the industry, in order to estimate their hazardous influence extent. The current article is a significant work on modelling of discharge and atmospheric dispersion of hazardous substances using state-of-the-art consequence modelling software. Emergency Response Planning Guidelines (ERPG) are used as reference exposure levels within the present study. Output data of computational modelling are significantly influenced by input parameters. In this regard, the effects of the latter for ensuring robustness of the simulation and for identifying improvements have proven to be necessary.

This paper refers to research undertaken in order to substantiate and elaborate ²The document for safety to professional vibration², which constitutes a procedural instrument for highlighting the synthesized estimation process of traceability and professional risk assessment of exposure to this type of emissions. Based on the results of the risk assessment of occupational exposure to vibration, whether exposure action values are exceeded, the employer must establish and implement a program of technical and/ or organizational measures intended to reduce exposure to occupational vibration.

The paper presents a theoretical and practical approach to the concept of risk assessment of exposure to noise, specific to activity for use of pyrotechnic articles Category 4, from the perspective of ensuring the security of the effect resulting after fireworks displaying with these types of pyrotechnic products. For estimation and risk assessment using these types of products, researches has been undertaken to make an evaluation process procedure in order to provide data and information to prevent and combat the causes that may create a hazard.

The main objective of this paper is to develop the infrastructure of the risk assessment methodology of major accidents in terms of considering the acts of malevolence.

The dust cloud is the main form of existence of combustible dust in the production area and together with the existence of effective ignition sources are the main causes of dust explosions in production processes. The minimum ignition temperature has an important role in the process of selecting the explosion-protected electrical equipment when performing the explosion risk assessment of combustible dusts. The heated surfaces are able to ignite the dust clouds that can form in process industry. The oil products usually contain hydrogen sulfide and thus on the pipe walls iron sulfides can form, which can be very dangerous from health and safety point of view. In order to study the influence of the pyrophoric sulfide over the minimum ignition temperature of combustible dusts for this work were performed several experiments on a residue collected from the oil pipes contaminated with commercially iron sulfide.

The naturally or industrially occurring flammable mixtures containing combustible gases or/and dusts represent a potential risk of explosion with major consequences on the environment and human personnel. Methane and coal dust are among the best known components able of leading to the formation of such mixtures either in coal mining activities or in different industries using coal dust as fuel. In order to assess the risk of explosion and the explosion evolution in such composite mixtures, the knowledge of the characteristic explosion parameters under standardized conditions is necessary. In this paper the maximum explosion pressure pmax, maximum rate of pressure rise (dp/dt)max and explosion severity factor for methane-air mixtures, air - coal dust mixture and hybrid air-methane-coal dust mixture were determined in a standard 20 dm3 spherical explosion vessel.

In industrial sectors that use, process, transport or store, substances such as combustible dusts could exist some workplaces with explosion hazard due to the possibility of dust/air explosive formation and ignition, both inside the installations and in the surrounding atmosphere. Methods and means of protection aim to prevent the development of explosive atmospheres, followed by preventing the occurrence of ignition sources and then limiting the effects of explosions. To assess the risk of ignition of the explosive atmosphere, there must be known first of all, the explosive atmosphere’s sensitivity to ignition by electrostatic discharge, respectively, the minimum ignition energy of the explosive mixture, afterwards being required an analysis on the possibilities of formation and discharge of electrostatic charge. For the most common combustible dusts, the minimum ignition energy is given, but for new types of flammable substances this parameter defining the sensitivity to ignition of the mixture by electrostatic discharges must be determined. The paper presents the results of research carried out in order to develop the methods and standards for determining the minimum ignition energy of the combustible dust / air mixture and of the methods for the assessment of the risk of ignition of the dust/air explosive atmosphere by electrostatic discharge.

Nowadays, the transportation of hazardous substances required for various industrial works is a very common activity. In each national economy, safe transport of hazardous materials on land is an important issue. Much of these materials are either moved by trucks or trains. However, hazardous materials transportation is very likely to generate major accidents with irreversible consequences on surrounding population and on the environment along transportation routes. The current paper deals with analysis and simulation of the consequences of an explosion involving a truck transporting flammable gas cylinders materials. Consequence modelling involves the graphic representation or the calculation and estimation of numerical values which best describe the physical results of loss of containment scenarios which involve flammable/explosive/toxic materials with regard to their impact on surrounding assets or people. In the present study, state of the art software has been used for modelling and simulating the accident scenario, namely the initial fire and the subsequent explosion of the gas cylinders.

This paper work presents the model for forecasting the exposure risk of workers to hand-arm occupational vibrations, which has been achieved in the PN 07 45 01 18 Project from within the framework of the NUCLEU/2012-2013 Program.This project is of national and European interest, in order to increase occupational health and safety level and to ensure sustainable environmental quality and comfort at work.

Fireworks are devices containing pyrotechnic composition which, upon functioning, will burn and/or explode to produce a visual or aural effect or movement, or a combination of such effects, intended as a direct form of entertainment.

The paper describes the results obtained during the experimentation of a new method that allows an in site verification of the electric systems for ignition of the electric detonators part of the special trucks for prospecting works, aiming to reach an adequate level of safety in operation. By this method, for in field verification of the electric detonators' ignition system that is mounted in the special trucks for prospecting works, based on the acceptance criteria and the operating ways on the safety parameters, the following are tested: insulation resistance, output energy and output voltage. Employing the verification method in situ prevents the operators electrocuting hazards, unexpected firing of electric detonators or misfiring in the blasting work itself, after the explosive charge was lowered into the prospecting hole. The method has successful experimented on site for 4 special trucks and it has implemented to INCD-INSEMEX Petrosani for testing programme of electric initiation system integrated in prospecting trucks in order to assessing the conformity of products in the voluntary field.

This paper aims to study the behavior of air-gas explosion systems, in terms of propagation speed of pressure wave and flame front, based on experimental measurements in a shock tube, in order to prevent accidental pollution with the combustion gases. The characteristic parameters of the explosion process determined using the shock tube, the velocity of propagation of the flame front, the speed of propagation of the wave of pressure, explosion pressure at various distances from the source of initiation, can be used in the preparation of explosion risk assessment studies for technological processes carried out in potentially explosive atmospheres. Taking the developed technical measures would make possible ensure both the explosion protection and the prevention of accidental pollution with combustion gases.

In order to investigate the degree of pollution by heavy metals, mining water samples were subjected to analysis, using inductively coupled plasma optical spectrometry method. An experimental module was developed and the water treatment capacity of natural zeolites was studied. The contaminated water was passed through 3 columns filled with zeolites, under static and dynamic mode in order to optimize the ion exchange process. Experiments were performed using different particle sizes of zeolite, and in different pH conditions. In this study, the degree of treatment in static conditions was performed, when a purification degree of 97.04% for zinc and 96.70% for manganese was obtained. In dynamic operation, the purification degree was lower, 81 % for manganese and 93% for zinc.