Gas Supply of Multi-Storey Building

When the pressure of natural gas changes, a significant level difference appears between the gas control point and the location of the consumer. In this case, the pressure value may exceed safety standards. In buildings, supplying gas to the burner with a value other than the nominal pressure causes incomplete combustion of the fuel and the formation of carbon monoxide. Leakage of natural gas at pressures above the nominal leads to a rapid increase in the percentage of gas in the room air above the lower concentration limit of explosiveness, which makes the mixture explosive. In this regard, in some countries, building codes do not allow gasification of buildings above 10 floors. In Georgia, such a ban does not exist and this problem becomes relevant, since a large number of high-rise buildings have been built in the country and almost 100% of them are gasified.

SUB-LAYER EXTINGUISHING OF ALCOHOLS BY BINARY MIXTURES OF FIRE-EXTINGUISHING AEROSOL AND CO2

Introduction. Now the number of enterprises and technological processes where alcohols and alcohol-containing liquids are used is constantly increasing. Due to the content of carbon, hydrogen and oxygen in the molecule, alcohols have increased flammable properties, namely: high combustion temperature, low lower concentration limit of flame propagation, high evapo-ration rate due to low boiling point and significant explosion pressure. Thus, in order to increase the fire safety of alcohol enterprises, is relevant the search for fire extinguishers that would provide both surface extinguishing and volumetric phlegma-tization of alcohol-air mixtures .The purpose and objectives of the study. The aim of the work is to determine the fire extinguishing factors and the efficiency of sublayer extinguishing by binary mixtures of fire extinguishing aerosol and CO2.Research objectives To establish fire-extinguishing factors of sublayer extinguishing of alcohols by binary mixtures of fire-extinguishing aerosol and CO2. To determine the fire-extinguishing efficiency of sublayer extinguishing of alcohols by binary mixtures of fire-extinguishing aero-sol and CO2.Methods. In the work according to the developed method with the use of metrologically certified equipment and certified measuring instruments, the fire-extinguishing minimum volume concentration of the components of the binary gas-aerosol mixture on the developed installation was determined.6 Пожежна безпека, №36, 2020Results. It was found that the maximum fire-extinguishing intensity of the aerosol formed from aerosol based compound based on sucrose (33%), potassium nitrate KNO3 (67%), is about 6 g / s in the experimental setup. The fire-extinguishing inten-sities of aerosol supply and its binary mixture with CO2 have been experimentally established. It was found that the addition of CO2 to the aerosol reduces the time of emergence of gas aerosol bubbles and quenching to 1.5 times. It was found that the size of the bubbles when adding CO2 is 10 -35% larger than when using CO2 itself.Conclusions. The results of the research showed that binary gas-aerosol mixtures have high fire-extinguishing efficiency with their sublayer supply for extinguishing alcohols and are several times more efficient, cheaper and have several times longer service life compared to traditional fire extinguishers.

COMPARISON OF POTENTIALALLY DANGEROUS FACTORS WITH THE USE OF RARE AND GASILY VEHICLE

A detailed analysis of the potentially dangerous factors in the use of diesel, gasoline, methane and propane-butane fuels was carried out in cars. A detailed analysis of potentially dangerous factors when using diesel, gasoline, methane and propane-butane fuels in automobiles has been carried out. 6 options of fuel usage are considered: a tank with g asoline and a system supplying it to the carburetor and further to the engine cylinders, a tank with diesel fuel and the system feeding it to the engine cylinders, gas cylinder installation when installing cylinders with methane on the roof of the car, gas cylinder installation when mounting cylinders with methane in the luggage compartment of the car, gas installation when installing cylinders with propane-butane mixture on the roof of the car, gas installation when installing cylinders with propane-butane mixture in the cargo compartment of the car. Meanwhile, the potential danger while the vehicle is in motion is analyzed, as well as while it is in the open parking lot and in the garage. As the initial data, the common operation period was taken - in summer with the temperature of 30°C and possible fuel leakage with the probability of formation of an explosive mixture. Nonane is taken as a model when considering gasoline, and Pentadecane is used for diesel fuel. It was noted that the gasoline self-ignition temperature ranges from 255°С to 435°0С, the lower concentration limit of petrol explosiveness can be considered as 0.76% vol., while under selected conditions indoors, gasoline vapor can reach the concentration of up to 0.8 vol. %. The relative vapor density of diesel fuel betting the same conditions is 8.52 kg/m3. With the explosion, the pressure in the closed volume will reach 5.2 atm. It was noted that the gasoline self-ignition temperature ranges from 210°С to 370°0С, the lower concentration limit of petrol explosiveness can be considered as in % vol., while under selected conditions indoors, gasoline vapor can reach the concentration of up to 0.13 vol. %. With the explosion, the pressure in the closed volume will reach 5.0 atm. The self-ignition temperature of methane is 537°C, the lower concentration limit of explosiveness of this gas is 5.28% (vol). The vapor density of methane at the temperature of 300°C (303K) is 0.64 kg/m3, which is significantly less than the density of air. The explosion pressure in the closed volume will reach 7.7 atm. The propane-butane mixture used in summer contains about 40% of propane and 60% of butane. Spontaneous ignition temperature of propane is 4700C, butane is 4050C. The calculated lower explosion limit of this mixture is 1.5% (vol), and the vapor density of mixture at the temperature of 300°C is 2.1 kg/m3, which is almost twice the density of air under the same conditions. The calculated explosion pressure in the closed volume will reach 8.3 atm. It was concluded that when using certified equipment which is professionally installed, methane, which cannot accumulate in the lower part of the room or any compartment, is much safer than propane-butane and, especially, than gasoline or diesel fuel, as vapor densities of both are more than air density.

A Quantitative Comparison of Methods Measuring Fluoride in Solutions or in Enamel

Fluoride in solution is most usually measured with the ion-specific electrode, although a few other methods are available. The electrode can be used in a straightforward manner, its lower concentration limit may be extended by special methods such as the standard addition of fluoride, or microdiffusion methods may be used to extract fluoride from the sample and concentrate it in base. Specifications of all methods are tabulated. A choice of method depends on the requirements in terms of specifications but also on the personal experience of the investigator and the required robustness. Microdiffusion of some kind is preferable for concentrations below 5 μmol/L or when electrode-interfering molecules such as proteins are present in rather high concentrations. Fluoride in enamel may be determined by removal of layers by etching, abrasion, or microdrilling, followed by dissolution of the layer removed. Specifications of depth and area resolution are tabulated. Alternatively, probing methods of a physical nature can be used. These methods require sophisticated instruments that are not widely available. Some of them are destructive, others are not. All but one require exposure to vacuum. However, most of them combine a very good sensitivity with a very good resolution in depth and/or measured area. Therefore, their use in research (requiring cooperation with instrument specialists/owners) may well be worth the effort.

The effect of drop size on flame propagation in liquid aerosols

A method has been developed whereby suspensions of controlled uniform drop size can be prepared from pure liquids. Using tetralin as the fuel, it has thus been possible, within limits, to study the effect of the drop size on the combustion properties of a liquid-in-air suspension. Through a study of limits of inflammability, nitrogen dilution limits and burning velocities, it has been shown that the mechanism of flame propagation is completely transformed within the drop-size range 7 to 55 μ . Below 10 μ the suspension behaves like a vapour, but above 40 μ the drops burn individually, in their own air envelope, and one burning drop ignites adjacent ones, thus spreading combustion. At intermediate sizes, behaviour is transitional. A practical consequence of this transformation is that the lower concentration limit of inflammability is reduced and the rate of burning increased for the larger drops.