Introduction. Flexible rationing determines the design objectives of the fire protection system of the object, and the ways to achieve them are chosen by the designer. The fulfilment of the set task is confirmed by the verification of criteria. The purpose of the article is to show the possibilities of using simulation modelling to implement the objectives of flexible rationing of fire protection systems of public buildings.

Theoretical foundations of simulation modelling. It is proposed to take into account individual fire risk and the risk of material losses in case of fire during simulation modelling. To draw one random fire scenario, an approved procedure for calculating individual fire risk is used, which is included in the main block. The list of random input variables, the areas of their change, the drawing of values, the processing of simulation results, the choice of solutions based on the results obtained, modelling control is carried out in the second block of the simulation system.

Results and their discussion. The application of simulation modelling is justified for the choice of rational decisions on fire safety. The designer based on the conditions of the object and fire safety requirements can choose the criterion and system of object protection by solving a multi-criteria problem. Models for assessing the reliabi­lity of the use of primary fire extinguishing means, fire extinguishing by the fire brigade in the fire centre, reliability of fire protection building structures, fire doors, separate or as part of fire barriers are proposed. The system of criteria is formulated, including the following criteria: individual fire risk, reduced costs, “evacuation time reserve”, necessary evacuation time.

On the basis of statistics obtained as a result of simulation modelling, the designer determines the required indicators. The formula for calculating the number of tests depending on the accuracy of determining the mathe­matical expectation, dispersion of random values of statistical parameters is given.

Conclusions. It is proposed to use Monte Carlo simulation modelling in the framework of flexible rationing when designing fire protection systems. Decision-making criteria that take into account the characteristics of fire risks are systematized. Calculated estimates of the effectiveness of a number of fire-fighting measures are given.

Introduction. A large proportion of direct-action safety valves open at given pressure, and close at lower pressure, forming a hysteresis loop. This effect is known from the test results for a long time. The reason for the occurrence of hysteresis is explained by comparing the gas dynamic forces acting on the moving parts of the valve and the force of the spring or load. Unfortunately, the comparison is made by a graph-analytic method that lacks gene­ral judgment. This could be overcome by describing the hysteresis loop analytically, but known mathematical models, including numerical ones, describe only its separate branches, whether it is the section of the loop at the moment of valve opening or closing.

Purpose of the research. To solve analytically the problem of constructing the hysteresis loop in the operation of direct-action safety valve.

Working hypothesis. Sharp movement of the valve head upwards from the seat to the stop in the limiter when the calculated pressure is reached in the protected volume and sharp movement of the head downwards to the seat when the pressure is reduced is the result of the head jumping from one stable position to another, bypassing the unstable part of the valve characteristic.

Method of the research. Theoretical, with the use of laws of gas dynamics, mechanics, stability theory and simi­larity theory.

Conclusions. The hysteresis loop in the operation of the safety valve, which represents the discontinuous function, can be described analytically. It is a set of stable sections of the equilibrium line of forces acting on the moving parts of the safety valve. Obtained from the condition of equilibrium of forces, the dependence of the valve lift height on the pressure in the protected volume quite adequately reflects the known experimental data.

It is also obtained that load valves organically have a large hysteresis loop, which by any means cannot be excluded. Spring valves also have a hysteresis loop, the size of which can be adjusted by changing the spring stiffness, including complete exclusion.

Introduction. The paper substantiates the importance of investigations of LNG tanks behaviour during fires. The most dangerous mode of their destruction (BLEVE, boiling liquid expanding vapour explosion), is mentioned. The relevance of the article is conditioned by the need to analyze the BLEVE phenomenon to prevent it and to miti­gate its consequences. The purpose of the paper is to present fundamentals of this phenomenon and to analyze advanced relevant research findings, including the analysis of recent accidents. The main focus is on liquefied natural gas.

General regularities of BLEVE. The BLEVE phenomenon was analyzed using p–V and p–T diagrams (p is pressure, V is volume, and T is temperature). Liquid boils at critical overheat temperature in the mode of homogeneous nucleation followed by BLEVE. Experimental data on critical overheat temperatures are presented for some liquefied gases and flammable liquids.

Brief analysis of BLEVE accidents involving LNG tanks. Major BLEVE accidents, involving LNG tanks, are considered. These events occurred in Tivissa (Spain, 2002), Zarzalico (Spain, 2011), and Shansi (China, 2019), and each involved road tanks for LNG transportation. Dimensions of hazardous thermal radiation zones, that emerged as a consequence of fireballs, blast waves and vessel fragments, reached 100–200 m.

Experimental and theoretical investigations of BLEVE and fireballs that emerged at LNG tanks. The most interesting experimental studies in this area are analyzed. Hazardous factors (the fireball diameter, time frame, height of elevation, and thermal radiation intensity) were determined using a 5 m3 tank. The empirical correlation, connecting the above mentioned parameters with the LNG mass in the tank, were obtained. Large-scale experiments were carried out to determine characteristics of fireballs that emerged when LNG was flowing out of the pipeline and when the resulting oversaturated cloud was on fire.

Conclusions. The main patterns of BLEVE and fireball accidents, involving LNG tanks, were analyzed. Their patterns are similar to those typical for LPG tanks. However, the surface radiation from LNG tank fireballs (nearly 500 kW/m2) is much higher than the surface radiation from LPG tanks (nearly 350 kW/m2).

Introduction. Updated requirements to (1) fire resistance limits and (2) the fire hazard class of building structures must be developed, and effective engineering solutions, allowing to implement these requirements, must be developed and substantiated due to the effective large-scale introduction of modular buildings into construction practice.

Goals and objectives. The aim of the article is to develop requirements to fire resistance limits, to the fire hazard class of building structures of modular buildings, and to fire resistance limits of intersections and fastening units, that are beyond the scope of Federal Law No. 123-FZ and fire safety regulations. The aim of the article also encompasses the development and justification of effective engineering solutions required to implement these requirements, as well as the pilot testing of the above-mentioned findings at construction facilities, having different numbers of storeys and functional purposes.

Methods. The analytical method is employed to substantiate the requirements applied to fire resistance limits and the fire hazard class of modular building structures. The proposed method supplements and refines provisions of the Federal Law No. 123-FZ and other fire safety regulations, taking into account the results of calculations and fire tests of fire resistance and fire hazard classes of basic building constructions of modular buildings.

Results. Introduction of the results of the work in fire safety designs of modular buildings, having different purposes and numbers of storeys; development of revisions for SP (Construction Regulations) 2.13130.2020 in compliance with the requirements applied to fire resistance limits and fire hazard classes for facilities composed of these structures.

Conclusion. Requirements for fire resistance limits and fire hazard classes were developed on the basis of the research; their distinctive feature is the location of load-bearing elements inside the building envelope, as a result of which provisions of No. 123-FZ and regulatory documents on fire safety do not establish requirements for the fire resistance limits of elements of such systems, requirements for fire resistance of intersections and fastening units, as well as requirements for fire hazard classes. The requirements have a combined nature, in other words, they contain minimum necessary and numerically different requirements for R, E, and I signs of each structure. They ensure the overall strength and 3D stability of the structural system and prevent the progressive collapse of structures outside the fire. Effective engineering solutions, allowing to implement the developed requirements, were substantiated.

Introduction. The emergence of robotic fire monitors (RFM), which form the basis of robotic fire suppression systems (RFSS), has significantly expanded the functionality of fire monitors used in extinguishing fires, and, accordingly, affected the extinguishing parameters. The purpose of the article is to substantiate the parameters of effective fire suppression by RFSS.

Effective extinguishing parameters. Firefighting monitors are used for extinguishing most of the fires. The development of robotic fire monitors (RFM) has significantly expanded the functionality of technology, which has become the basis of robotic fire suppression systems (RFSS).

The main advantage of the RFSS is the ability to detect the source of ignition at an early stage and extinguish it with the entire flow of the fire extinguishing agent (FEA) by targeted supply of a jet of FEA to the source of ignition along a ballistic trajectory. This creates a high intensity of irrigation, which allows a quick elimination of the source of fire, which significantly increases the efficiency of fire extinguishing and reduces damage from fire. Standards for traditional automatic fire suppression systems (AFSS) include standard extinguishing parameters for irrigation intensity in, total flow rate Qn and extinguishing time tn. Extinguishing on the area St is carried out at a constant normative intensity of irrigation in, while the flow rate of extinguishing Qt will be a variable value depending on the extinguishing area. A feature of RFSS, in contrast to traditional AFSS, is that the flow rate is a constant value, and the irrigation intensity and extinguishing time are variable values. The article considers the influence of the distinctive features of the RFSS on the extinguishing parameters, the actual issues of the effective application of the RFSS, and provides a rationale for the optimal parameters of the RFSS, taking into account a differentiated approach in relation to the RFSS. The calculated data are given on the actual parameters of fire extinguishing of the RFSS, taking into account the assessment based on the actual test results. The possibility of algorithmization of the operation of the RFSS (stopping the extinguishing and checking the quality of the extinguishing) based on the condition of localization and elimination of fire at an early stage of fire development is shown.

Conclusions. Improving the technical means and algorithms for the operation of the RFSS allows to review the existing extinguishing parameters with the including of new parameters. The use of new parameters of the RFSS will significantly increase efficiency in terms of such as reducing flow rate, reducing extinguishing time, and reducing damage from a fire.

Introduction. Effective application of forces and means of the Ministry of Emergency Situations of Russia for solving a wide range of tasks according to the intended purpose to a great extent depends on the activity of the management system of the department connected with the development of optimal decisions and plans. The head of the appropriate level of management of the Ministry of Emergency Situations of the Russian Fede­ration when making a decision faces the need to develop optimal ways of action of subordinate forces and means in the expected conditions of the situation. The use of methods of decision-making theory and operations research in such conditions is the most pragmatic approach.

Aims and purposes. Finding the optimal plan for detecting the victim of a catastrophe object in the emergency zone in the shortest possible time and with a minimum number of casualties is an optimization problem, which should be solved using known mathematical methods (methods of operations research). This problem can be formulated as follows: to determine the optimal sequence of traversal of the search area of the object in the disaster zone in the shortest possible time.

Methods. Two methods were used to solve the problem: the method of dynamic programming (DP) and an ap­­pro­ximate method obtained experimentally. Using the R. Bellman functional equation, a mathematical model for predicting different variants of event development and finding the optimal variant of the problem solution was constructed.

Results and discussions. The article considers the methods of optimization of decisions during search and rescue operations in the emergency zone in order to support managerial decision-making in the operational activity of the Ministry of Emergency Situations of Russia. The method of finding the optimal plan of surveying the areas of the search area of the object is proposed using the method of DP. Calculations with specific initial data for drawing up the optimal route of object search in the shortest possible time are given. The approximate method of finding the optimal sequence of detour of object search areas with a slight simplification of initial data is proposed, which is proved experimentally on different examples and with different initial data.

Conclusions. Mathematical modelling is successfully applied in tasks of optimization of processes of management of forces and means of the Ministry of Emergency Situations of Russia. Methods of operations research are also used in solving the problems of operational activity of the Ministry, which use DP for step-by-step finding the optimal variant of management decision.

Introduction. Currently, the design and construction of liquefied natural gas (LNG) facilities are actively taking place in the Russian Federation. Accidents at these facilities typically start with equipment leaks, followed by the release and subsequent ignition of flammable substances. The impact of such fire hazards can lead to the destruction of adjacent equipment and cascading accidents. Existing literature on LNG fire suppression mainly focuses on extinguishing or containing LNG spills. However, there is limited research on fire suppression of pressurized combustible gases.

This publication aims are to develop a methodology for conducting fire tests on gas jet fire suppression.

The tasks include reviewing the results of previous experiments on jet releases of LNG, analyzing the frequency of leaks and their most probable diameter, determining the parameters of the model fire source, defining the parameters of the test setup, and outlining the procedure for conducting fire tests.

Analytical part. The methodology is developed based on the analysis of statistical data on accidents in the petrochemical industry. Parameters of the test setup for conducting LNG jet fire suppression tests are determined using data on the frequency of equipment leaks and the most probable equivalent diameter of the accidental openings.

Conclusions. A review of previous experiments on LNG jet releases and an analysis of leak frequencies and their most probable diameters have been conducted. Based on this analysis, parameters for the test setup and a pro­cedure for conducting fire tests have been proposed. A methodology for conducting fire tests on gas jet fire suppression to determine the fire extinguishing effectiveness of fire suppression modules has been developed.

Statistical data reflecting the state of the electric vehicle fleet in Russia are presented. The description of the main difficulties arising for firefighting departments when extinguishing traction lithium-ion batteries of electric vehicles is given. The existing fire extinguishing systems for electric vehicles successfully used in a number of foreign countries are analyzed. The technical possibility of effective extinguishing of the battery pack with the help of water when it is supplied directly into the internal space of the battery is shown. The ways of ensuring fire safety in case of repeated ignition of an electric car battery with performance of full immersion of the latter in a container with water, and also covering the body with a fireproof cloth are considered.