Application of the Statistical Methods for Determining the Self-ignition Temperature of Combustible Liquids
Purpose: The purpose of this research was to develop a calculation-experimental method of determining the probability of self-ignition of flammable liquids. The article discusses self-ignition of liquids involved in the technological process that occurs as result of their contact with a heated surface. The relevance of the conducted research is supported by the fact that there is no unified approach for determining the temperature of spontaneous ignition. For this reason the assessment of the reliability of the existing experimental data and its practical use, e.g., in the form of initial data for the development of calculation methods is not always possible. Methods: Experimental work included the carrying out the tests according to GOST-1313 (a method for determining the minimum temperature at which the flammable liquid will spontaneously ignite) on the «standard» experimental stand, as well as the modernised experimental stand which differs from the «standard» by the fact that the closed reaction vessel is replaced with an opened cylindrical glass on the bottom of which there is a flat cylindrical plate 5 mm thick made of the tested material. Plate’s temperature is controlled and measured with a thermocouple. Single drops of the liquid are squeezed out of the pipette from a height of 15 cm and fall on the center of the plate. For the analysis of the results the authors used the logistic regression model that relates the probability of flammable liquid self-ignition from a heated surface with the predictors (experimental conditions, coinciding with the terms of the technological process). For the approbation of the probabilistic approach to the definition of the self-ignition temperature of combustible liquids were executed test to spontaneous combustion of diesel fuel DWT. Investigation of the self-ignition hanging ten different volumes (0,1 ml, 0,2 ml,..., 1.0 ml) in the temperature range 247ºС - 266ºС through one degree (5 tests for each temperature). The results showed good agreement between the calculated and experimental data. Thus, a new calculation-experimental method, which allows to predict the probability of ignition fluids combustible in a particular technological process. On the basis of the proposed approach is expected to create a program code. Research data allow the categorization of technological processes according to their fire risk. As a criterion security will serve the temperature of a heated surface at which ignition occurs with a certain degree of probability.