RECENT TRENDS IN THE DEVELOPMENT OF SENSORS FOR PRE-EXPLOSIVE CONCENTRATIONS OF FLAMMABLE GASES AND VAPORS OF FLAMMABLE LIQUIDS (REVIEW)

This paper presents a review of current trends in the development of manufacturing technologies of sensors of pre-explosive concentrations of flammable gases and vapors of flammable liquids. Various types of gas sensors are discussed, including catalytic, semiconductor, and optical sensor types, and the principles of their operation. The advantages and disadvantages of each type of gas sensor are highlighted. New and traditional technologies for manufacturing sensitive elements that improve sensor parameters such as processability, miniaturization and reduce energy consumption are discussed. In conclusion, this article suggests future trends and prospects for development and research to improve the sensitivity and selectivity of sensors.

Prospective designs of self-extinguishing devices for spills of burning engine fuels

Проведены теоретические и экспериментальные исследования процессов горения и прекращения горения моторных топлив в трубчатых вертикальных каналах без применения средств пожаротушения. Разработаны технические решения, обеспечивающие локализацию проливов горящих жидкостей и эффективное прекращение горения проливов бензина, летнего, зимнего и арктического дизельных топлив. По результатам проведенных исследований разработаны перспективные конструкции устройств, обеспечивающие самотушение моторных топлив за время не более 300 с. В данных конструкциях реализуется принцип подавления естественной конвекции с помощью ряда конструктивных приемов, которые нарушают взаимосвязь пламени с испаряющейся жидкостью и воздушной средой, создавая тем самым условия прекращения горения. There were found technical solutions for localization of spills of burning liquids and effective flame suppression, called self-extinguishing devices for spills of flammable liquids (USP) on the basis of researches conducted by FGBU VNIIPO EMERCOM of Russia (VNIIPO). Currently there are developed several types of USP differ from each other in design solutions due to the conditions of their practical application. The efficiency of devices is confirmed by numerous experiments on self-extinguishing of burning spills of transformer and turbine oils, conducted by VNIIPO and LLC “SKB” Tensor” in the interests of electric power companies. A number of copyright certificates and patents for inventions were obtained. The principle of suppressing natural convection is implemented in the configuration of USP by a number of design techniques that violate the connection of flame with evaporating liquid thereby creating burnout conditions. This paper presents investigation results on development of self-extinguishing devices for spills of burning motor fuels. The conducted theoretical studies of possibility of extinguishing motor fuels in the channels of USP devices allowed us to determine the critical height of the channels at which self-extinguishing of motor fuels occurs. The results of theoretical studies were confirmed experimentally. The experiments were conducted in two stages. There were tested 15 experimental samples of grids of modular USP assemblies with a ratio of lengths and diameters of vertical channels of 3.8 at the first stage of experiments. At the second stage there were tested 4 mock-up samples of USP for motor fuels manufactured by LLC “SKB “Tensor” with a ratio of lengths and diameters of vertical channels from 3.8 to 6 with grid elements and with flat and volumetric hydraulic locks. There were identified the most promising USP designs that provide self-extinguishing of engine fuel spills with the necessary parameters.

EXPERIMENTAL STUDIES OF THE RELATIONSHIP BETWEEN THE BOILING TEMPERATURE AND THE FLASH TEMPERATURE OF MIXED HYDROCARBON FUELS

В работе экспериментально показано, что по мере испарения смесевой горючей жидкости при одновременном повышении плотности и снижении упругости пара в многокомпонентных взаиморастворимых композициях температура кипения повышается. В этом случае и температура вспышки смесевой горючей жидкости также будет повышаться. Так, при проливах горючих жидкостей происходит довольно быстрое обеднение легкими фракциями, упругость пара при заданной температуре существенно снижается, а температуры кипения и вспышки, соответственно, повышаются. Полученные в работе зависимости температур кипения и вспышки испытанных смесевых горючих жидкостей характерны и для других различных многокомпонентных жидких композиций. Эти зависимости могут учитываться при разработке планов предотвращения и ликвидации аварий в случае их проливов. Based on the experiments it is shown that as the flammable liquid mixtures evaporate, while increasing density and decreasing vapor tension in multicomponent compositions-soluble, the boiling temperature increases. In this case, the flash point of the mixed combustible liquid will also increase. Thus, in the case of spills of flammable liquids there is a fairly rapid depletion of light fractions, the vapor tension at a given temperature reduces significantly, and the boiling and flash temperatures increase accordingly. The dependences of the boiling and flash temperatures of the tested mixed combustible liquids obtained in this work are also typical for other various multicomponent liquid compositions. These dependencies can be taken into account when developing plans for the prevention and elimination of emergencies caused by their spills.

Testing of metrological parameters of analyzers of explosive gases in laboratory conditions

Introduction. When training fire safety specialists, it is practically important to acquire skills in assessing the fire hazard of accidents with the release of flammable gases (GG) and vapors of flammable liquids (FL). The task of detecting hazardous concentrations of these substances is performed by gas analysis systems, the main element of which is gas analyzers. Goals and objectives. The aim of the study is to create a gas analysis installation for determining the main metrological characteristics of gas analyzers in a training laboratory. The tasks include the analysis of an existing installation that complies with the current standard, consideration of the design of the test chamber and the methodology for its application for the study of gas analyzers with a diffusion supply of the analyzed medium. The methods include system analysis and mathematical assessment of physical processes occurring in the test chamber during the preparation and conduct of research. Results and discussion. The article proposes and substantiates the design of a laboratory facility, in which a given volumetric concentration of the explosive substance under investigation is created in a special chamber with the help of a dispenser. Mathematical expressions have been obtained to determine the required amount of flammable liquids. The method of preparation of the installation and options for its use for laboratory work are considered. This technique is simple and ensures the safety of industrial gas analyzers research. Conclusions. The article substantiates the design of the gas analysis unit using a special chamber as a source of the gas mixture (GM). A mathematical model of the formation of HMs with a given volumetric concentration of flammable liquids vapors is obtained, based on the Mendeleev-Cliperon equation. The technique of preparing a chamber for determining the metrological characteristics of gas analyzers in a training laboratory is considered. Keywords: explosive gas, gas analyzer, laboratory facility, ideal gas equation, test chamber

Experimental and theoretical investigation of acetone evaporation

In the case of flammable liquids, it is known that is not the liquid itself that is prone to ignition, but the vapour of the hazardous substance. For these substances, it is particularly important to be able to determine exactly how much vapour is produced and how it spreads. The substance to be tested is acetone. That is a common substance in households in various forms (cosmetics), but is also frequently used in the chemical industry. Different models are available for calculating the evaporation rate, which are compared in this study with the evaporation experiments carried out. The aim is to select a suitable model in relation to the measured results.