Experimental and analytical studies of the fire hazard of materials used in equipment with oxygen-enriched media and ways to reduce their flammability

Introduction. Sealed equipment (hereinafter referred to as hermetic chambers) is used in various branches of economy. Atmospheres enriched with oxygen (in some cases under variable pressure conditions) are used.
It was shown that the main reason of the fires in the pressurized chambers was the unregulated use of the electrical equipment, as well as combustible substances and materials on the basis of organic compounds included in the materials used in the pressurized chambers.

Objective. To find ways to decrease combustibility of materials used in pressurized chambers and to study fire risk parameters of pressurized chambers with high oxygen content and increased pressure.

Objectives. To determine the boundary conditions of applying materials with increased values of temperature, oxygen content and pressure and analyze the results of experimental studies of combustibility of materials used in sealed chambers.

Research methods. Investigation of the characteristics of the combustion process of non-metallic materials under increased pressure was carried out on an original setup represented by a stainless steel vessel with a height of 750 mm and an inner diameter of 155 mm. A spiral of nichrome wire was used to ignite the sample. The pressure was fixed with a manometer.

Results and their discussion. As a result of experimental research of fire hazard of construction and construction materials in oxygen-enriched media and under increased pressure the ways of increasing the oxygen concentration limit (OCL) and reduction of combustibility of materials were determined: application of heat-removing surface, incombustible shell; putting inhibitors in their composition and structure; surface treatment with different fire protective compositions and impregnations. When studying the parameters of fire hazard (flame propagation velocity, heat of combustion, autoignition temperature) of materials under the conditions of changes in the composition of nitrogen-oxygen atmosphere and pressure, it was found that the OCL for all materials decreases at higher pressures.

Conclusions. It is found that the limiting oxygen concentration depends on the geometrical dimensions of the sample, as well as on the speed of the gas flow. At higher pressures the OCL for all the materials decreases. The presence of a heat-removing surface also leads to higher OCL, which increases with increasing substrate thickness and decreasing thickness of the material on it. For materials not containing substances that inhibit the combustion reaction, a decrease in the LOC value with an increase in the number of hydrogen atoms in the polymer macromolecule is characteristic.

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