Mirela Ancuta Radu’s research while affiliated with National Institute for Research and Development in Mine Safety and Protection to Explosion and other places

A potentially explosive atmosphere exists when a mixture of air, gases, vapours, mists or dust combines in a way that can ignite under certain operating conditions. Hydrogen is the special gas in this context. Those who have knowledge of the properties and flammability of hydrogen will recognize that hazards due to explosive atmospheres must be assessed more and more frequently as the element is utilized, and, if necessary, appropriate protective measures must be taken. In this kind of atmosphere, special attention should be given to the mechanical equipment that are being used for operational purposes, as they might initiate an explosion. Mechanical equipment used in explosive atmospheres should be assessed through an ignition hazard assessment. They must fulfil the essential health and safety requirements, which implies that they shall be assessed according to their ability to prevent them from becoming ignition sources and their ability to protect against the consequences of an explosion. This paper presents the issue of the ignition hazard assessment of mechanical equipment and points out some aspects that may be important to consider when assessing mechanical systems for use in potentially explosive atmospheres. Ignition of explosive atmospheres by mechanical equipment occurs when energy supplied by equipment is converted into heat, usually as the result of a mechanical failure of the equipment or associated systems. The ignition hazard assessment procedure also involves a series of specific laboratory tests. These tests demonstrate the non-sparking character of the materials used in the manufacture of mechanical equipment and the fact that the assessed equipmen

An attack with a "improvised" explosive device (IED) is when someone uses a bomb and/or destructive device to cause damage, render someone helpless, harass, or divert attention. Terrorists, criminals, vandals, suicide bombers, and rebels all utilize IEDs. IEDs can take many different shapes because they are improvised; they can be as simple as a pipe bomb or as complex as a sophisticated weapon that can inflict significant damage and casualties. IEDs can be transported or carried in a car; they can also be delivered in a package; they can be delivered by a person; or they can be hidden by the side of the road. In the course of 2023, INSEMEX perfected, patented, and tested the liquid-jet neutralization device of the improvised explosive devices DNJLDEI (prototype for an improvised bombs neutralization device, Patented Request CBI OSIM nr. a/00178/11.04.2023), which has the potential to be a valuable tool for urban interventions against terrorist attack. In this paper was presented the liquid-jet neutralization device of the improvised explosive devices DNJLDEI (prototype for a neutralization device of improvised explosive bombs), which has the potential to be a valuable tool for urban interventions against the terrorist attack. Tests were carried out for the two improved variants of plastic containers, with measurements of the velocity of the projected liquid jet (water). The experimental test program of DNJLDEI included the final verification of functionality of new prototype of IED neutralization device, based on liquid-jet, the operational validation being performed upon a bomb briefcase, which was neutralised by accuracy destroying of detonator, without damages of explosive charge.

Electrical contacts are important circuit components with diverse industrial applications, and their failure can lead to multiple unwanted effects. Hence, the behavior of electrical contacts is a widely studied topic in the scientific literature based on various approaches, tools, and techniques. The present study proposes a new approach to numerical modeling and simulation based on the Holm contact theory, aiming to study the dependence between the electric potential and the temperature within an electrical contact. Structured in five sections, the research was conducted using COMSOL Multiphysics software (version 5.3) and its solid-state mechanics, electric current, and heat transfer modules in order to highlight contact behavior from mechanical, electrical and thermal points of view: the von Mises stress, contact force, electric field amplitude, variation of the electrical potential along the current path, temperature gradient, and dependence of temperature along the contact elements edges were obtained by simulation, and are graphically represented. The results show that the temperature increase follows a parabolic curve, and that for values higher than 4 mV of voltage drop, the temperature of the contact increases to 79.25 degrees (and up to 123.81 degrees for 5 mV) over the ambient temperature, thus the integrity of insulation can be compromised. These values are close (10–12%) to the analytically calculated ones, and also in line with research assessed in the literature review.

Electrical contacts are important circuit components with diverse industrial applications, and their failure can lead to multiple unwanted effects. Hence, the behavior of electrical contacts is a widely studied topic in scientific literature based on various approaches, tools, and techniques. The present study proposes a numerical modeling and simulation approach based on the Holm contact theory to study the dependence between the electric potential and the temperature within an electrical contact. Structured in 5 sections, the research was conducted using COMSOL Multiphysics software and its solid-state mechanics, electric current, and heat transfer modules in order to highlight contact behavior from mechanical, electrical and thermal points of view: the von Mises stress, contact force, the electric field amplitude, the variation of the electrical potential along the current path, the temperature gradient, and dependence of temperature along the contact elements edges were obtained by simulation and graphically represented. The results are in line with the expectations and with past research that was studied in the literature review.

In order to improve the safety and health protection of workers who may be exposed to a potential risk due to explosive atmospheres, in every industrial area where such atmospheres may occur, the employer shall ensure the development and updating of a document called Explosion Protection Document. The main chapter of this document is the Explosion Risk Assessment. Risk assessment is a complex process that involves identifying the risk, analyzing the risk and estimating the risk, the main purpose of assessing the level of risk being to establish the necessary protection measures to reduce it to acceptable levels. This paper identifies the factors that may influence the level of risk of explosions in the workplace in order to establish the protection measures required to reduce the risk to acceptable levels. Explosion risk assessment must be performed by competent persons with knowledge of technical, electrical and mechanical engineering and who understand the general principles of explosion protection.

Anthropogenic activities related to mining generate both progress and a vast amount of waste that is responsible for environmental degradation. The Jiu Valley is one of the areas of Romania where mining has affected large areas of land, used to build mines and tailings ponds. The former Coroiesti coal processing plant (CCPP) is such a location with a total area of 25 ha containing approximately 5.5 million tons of tailings. The assessment of the stability of tailings dams is extremely important from safety and environmental aspects. This study proposes a solution based on numerical methods for determining the stability of a section of the dam of a tailings pond. The model of tailings pond no. 1, compartment B, from the Coroieşti Coal Preparation was built using COMSOL Multiphysics. Two scenarios of stability analysis were conducted on a section of the tailings dam: the FOS was determined using the shear strength reduction (SSR) method for both the initial and the current state of this TP. This method is a modern alternative to the limit equilibrium method, and its implementation by COMSOL is new to our country, thus aligning this methodology with current worldwide trends and developments in the field. The results obtained proved to be in line with those calculated in the past with traditional analytical methods, proving that the safety criteria of the studied TP/TD are being met.

The continuous development of human society from a technical-economic point of view is closely related to the increase in energy consumption. However, this implies the rapid depletion of existing fossil fuels and an accelerated increase in global pollution. At the moment, to counteract these impediments, one of the most important sources that can be used for the purpose of energy production, without having a negative impact on the environment, is hydrogen. Due to the fact that, when mixed with air, hydrogen can generate potentially explosive atmospheres, it is necessary to adopt and apply protective measures aimed at ensuring an acceptable level of protection in accordance with current regulations. These measures materialize mainly through the use of appropriately protected technical equipment in locations where potentially explosive atmospheres generated by the presence of hydrogen are possible. Some of these equipment�s are provided with non-metallic casings on which the type of protection of the respective equipment depends. That is why, in order to demonstrate the ability of the non-metallic materials that make up the equipment casings, to maintain the specific type of protection after exposure to extreme, positive and negative temperatures, it is of particular importance to determine the thermal endurance of the respective casings by performing laboratory tests. This paper highlights the importance of determining the thermal endurance in the case of equipment with non-metallic casings and non-metallic parts of the casings intended to be used in potentially explosive atmospheres generated by hydrogen, as well as the method and equipment required to perform laboratory tests for its determination.

The removal and collection of dust particles from the air discharged into the atmosphere by industrial plants processing, transporting and storing dusty materials is an important objective for employers to prevent air pollution according to environmental legislation and employee safety regulations. Where the dust in question is flammable and may generate an explosive atmosphere, measures must be taken to prevent explosion and/or limit the effects of explosion. To this end, proper assessment of the risk of explosions is essential in order to determine the effectiveness of the measures implemented and/or the need to take additional measures. As there is no specific assessment method for the risk of explosions in dust/air explosive atmospheres, various bodies/persons have developed their own more or less comprehensive assessment methods. In the paper are presented some important aspects included in the assessment procedure applied by us for the evaluation of the risk of explosions in dust removal systems with emphasis on the development of laboratory tests to determine the explosive characteristics of explosive air/flammable dust mixtures as well as on the constructive solutions to limit the effects of possible explosions. It highlights the importance of the competence of persons involved in the design, installation, maintenance and inspection of installations regarding the application of standards, guidelines and legislation in the field.

Due to the tightening of air pollution laws and employee safety regulations, manufacturers are being forced to pay more and more attention to removing dust particles from the air released by their installations. This requires them to install large complex dust collection systems in all their facilities. Dust collection systems include collection points where air and entrained dust are drawn into a system of pipes that carry dust and air, fans that feed the movement of air, and dust collectors that separate dust from air. Dust collectors are mostly dry type. Dry-type dust collectors are divided into cyclones and bag-type dust collectors. As dust can create an explosive atmosphere, it is necessary to assess the risk of explosions and to establish appropriate measures to prevent the explosion or, as the case may be, to limit the effects of explosions. The paper presents aspects related to the evaluation of the risk of explosions at dust removal installations with emphasis on the risk of initiating the explosive dust / air atmosphere through electrostatic discharges.

In the case of use of the electric igniters, in various applications, depending on their field of use, there may be a risk of unexpected initiation by means of electrostatic discharges from persons, their clothing and / or objects isolated from the ground. Electrification and consequently the accumulation of dangerous electrostatic potentials on people and on their outerwear, generally takes place during the performance of work tasks, a situation in which due to the movements performed by the persons involved, there is the phenomenon of friction between different parts of clothing or between clothing and the person wearing the clothing. The presence of the risk of unexpected initiation of electric igniters by electrostatic discharge requires the adoption and implementation of measures to minimize their effects on the safety and health of workers and others. In view of the above, determining the performance of sensitivity of electric igniters to unexpected initiation by electrostatic discharge is very important as this depends on the safety and security of workers / persons involved in activities that require the use of these elements / products.