Means for localizing and extinguishing fires in railways. Open Library - open library of educational information

The main types of equipment designed to protect various objects from fires include alarm and fire extinguishing equipment.

Fire alarm must quickly and accurately report a fire, indicating its location. The most reliable fire alarm system is the electric fire alarm. The most advanced types of such alarms additionally provide automatic activation of the fire extinguishing means provided at the facility. Schematic diagram The electrical alarm system is shown in Fig. 18.1. It includes fire detectors installed in protected premises and connected to the signal line; receiving and control station, power supply, sound and light alarms, as well as automatic installations fire extinguishing and smoke removal.

Rice. 18.1. Schematic diagram of the electrical fire alarm system:

1 - detector sensors; 2- receiving station; 3-block backup power;

4-block – mains power supply; 5- switching system; 6 - wiring;

7-actuator mechanism of the fire extinguishing system

Reliability electrical system signaling is ensured by the fact that all its elements and connections between them are constantly energized. This ensures constant monitoring of the serviceability of the installation.

The most important element Alarm systems are fire detectors that convert physical parameters characterizing a fire into electrical signals. Based on the method of actuation, detectors are divided into manual and automatic. Manual call points produce an electrical signal of a certain shape into the communication line at the moment the button is pressed.

Automatic fire detectors are activated when environmental parameters change at the time of a fire. Depending on the factor that triggers the sensor, detectors are divided into thermal, smoke, light and combined. The most widespread heat detectors, the sensitive elements of which can be bimetallic, thermocouple, semiconductor.

Smoke fire detectors that react to smoke have a photocell or ionization chambers as a sensitive element, as well as a differential photo relay. Smoke detectors There are two types: point, signaling the appearance of smoke at the place of their installation, and linear-volumetric, working on the principle of shading the light beam between the receiver and the emitter.

Light fire detectors are based on fixing various | components spectrum open flame. Sensitive elements Such sensors react to the ultraviolet or infrared region of the optical radiation spectrum.

The inertia of the primary sensors is an important characteristic. Thermal sensors have the greatest inertia, light sensors the least.

A set of measures aimed at eliminating the causes of a fire and creating conditions under which continuation of combustion will be impossible is called fire extinguishing.

To eliminate the combustion process, it is necessary to stop the supply of either fuel or oxidizer to the combustion zone, or reduce the supply heat flow to the reaction zone. This is achieved:

Strong cooling of the combustion site or burning material with the help of substances (for example, water) with high heat capacity;

Isolation of the combustion source from atmospheric air or by reducing the oxygen concentration in the air by supplying inert components to the combustion zone;

The use of special chemicals, inhibiting the rate of oxidation reaction;

Mechanical flame suppression with a strong jet of gas or water;

By creating fire suppression conditions under which the flame spreads through narrow channels, the cross-section of which is smaller than the extinguishing diameter.

To achieve the above effects, the following are currently used as extinguishing agents:

Water that is supplied to the fire source in a continuous or sprayed stream;

Various types of foams (chemical or air-mechanical), which are air bubbles or carbon dioxide, surrounded by a thin film of water;

Inert gas diluents, which can be used: carbon dioxide, nitrogen, argon, water vapor, flue gases, etc.;

Homogeneous inhibitors - low-boiling halogenated hydrocarbons;

Heterogeneous inhibitors - fire extinguishing powders;

Combined formulations.

Water is the most widely used extinguishing agent.

Providing enterprises and regions with the necessary volume of water for fire fighting is usually done from the general (city) water supply network or from fire reservoirs and containers. Requirements for fire water supply systems are set out in SNiP 2.04.02-84 “Water supply. External networks and structures" and in SNiP 2.04.01-85 "Internal water supply and sewerage of buildings."

Fire-fighting water supply systems are usually divided into low- and medium-pressure water supply systems. Free pressure during fire extinguishing in the water supply network low pressure at the design flow rate it must be at least 10 m from the ground surface level, and the water pressure required for fire extinguishing is created by mobile pumps installed on hydrants. Online high pressure The height of the compact jet must be ensured at least 10 m at full design water flow and the location of the barrel at the level of the highest point of the tall building. High pressure systems are more expensive due to the need to use increased strength pipelines, as well as additional water tanks at the appropriate height or pumping water station devices. Therefore, high-pressure systems provide for industrial enterprises, more than 2 km away from fire stations, as well as in populated areas with a population of up to 500 thousand people.

R and p.1 8.2. Integrated water supply scheme:

1 - water source; 2-water intake; 3-station first lift; 4-water treatment facilities and a second lift station; 5-water tower; 6 main lines; 7 - water consumers; 8 - distribution pipelines; 9-entry into buildings

A schematic diagram of the united water supply system is shown in Fig. 18.2. Water from a natural source enters the water intake and is then supplied by pumps from the first lift station to the structure for treatment, then through water pipelines to the fire control structure (water tower) and then through the main water lines to the entrances to the buildings. The construction of water pressure structures is associated with uneven water consumption by hour of the day. As a rule, the fire-fighting water supply network is made ring-shaped, providing two water supply lines and thereby high reliability of water supply.

The regulated water consumption for fire extinguishing consists of the costs for external and internal fire extinguishing. When rationing water consumption for external fire extinguishing, it is based on the possible number of simultaneous fires in locality, arising in I for three adjacent hours, depending on the number of residents and the number of storeys of buildings (SNiP 2.04.02-84). Consumption rates and water pressure in internal water supply systems in public, residential and auxiliary buildings are regulated by SNiP 2.04.01-85 depending on their number of floors, length of corridors, volume, purpose.

For indoor fire extinguishing, automatic fire extinguishing devices are used. The most widely used installations are those that distribution devices use sprinkler (Fig. 8.6) or deluge heads.

sprinkler head is a device that automatically opens the water outlet when the temperature inside the room increases due to a fire. Sprinkler systems turn on automatically when the indoor temperature rises to a predetermined limit. The sensor is the sprinkler head itself, equipped with a low-fusible lock that melts when the temperature rises and opens a hole in the water pipeline above the fire. A sprinkler installation consists of a network of water supply and irrigation pipes installed under the ceiling. Sprinkler heads are screwed into the irrigation pipes at a certain distance from each other. One sprinkler is installed on an area of ​​6-9 m2 of room, depending on fire danger production. If in the protected premises the air temperature can drop below + 4 °C, then such objects are protected by air sprinkler systems, which differ from water ones in that such systems are filled with water only up to the control and alarm device, distribution pipelines located above this device in unheated room, are filled with air pumped by a special compressor.

Deluge installations in design they are similar to sprinklers and differ from the latter in that the sprinklers on the distribution pipelines do not have a fusible lock and the holes are constantly open. Deluge systems are designed to form water curtains, to protect the building from fire in the event of a fire in an adjacent building, to form water curtains in the room to prevent the spread of fire and for I fire protection in conditions of increased fire danger. The deluge system is turned on manually or automatically by the first signal from an automatic fire detector using a control and starting unit located on the main pipeline.

Air-mechanical foams can also be used in sprinkler and deluge systems. The main fire-extinguishing property of foam is to isolate the combustion zone by forming a vapor-proof layer of a certain structure and resistance on the surface of the burning liquid. The composition of air-mechanical foam is as follows: 90% air, 9.6% liquid (water) and 0.4% foaming agent. Characteristics of foam that determine it

fire extinguishing properties are durability and multiplicity. Durability is the ability of the foam to survive high temperature in time; air-mechanical foam has a durability of 30-45 minutes, the expansion ratio is the ratio of the volume of foam to the volume of the liquid from which it is obtained, reaching 8-12.

| Foam is produced in stationary, mobile, portable devices and hand-held fire extinguishers. Foam of the following composition is widely used as a fire extinguishing agent I: 80% carbon dioxide, 19.7% liquid (water) and 0.3% foaming agent. The multiplicity of chemical foam is usually 5, durability is about 1 hour.

The process of extinguishing fires is divided into localization and elimination of fire. Under localization fires understand limiting the spread of fire and creating conditions for its elimination. Under liquidation Fires mean the final extinguishing or complete cessation of combustion and the elimination of the possibility of re-occurrence of fire.

The success of quickly localizing and extinguishing a fire in its initial stage depends on the availability of fire extinguishing means and the ability to use them, fire communications and alarm systems for calling the fire brigade and activating automatic fire extinguishing systems. The main fire extinguishing agents and substances are water, sand, inert gases, dry (solid) fire extinguishing substances, etc.
Fire extinguishing agents
Firefighting is a set of measures aimed at extinguishing fires. For the occurrence and development of the combustion process, the simultaneous presence of a combustible material, an oxidizer and a continuous flow of heat from the fire to the combustible material (fire source) is necessary; then to stop the combustion, the absence of any of these components is sufficient.

Thus, cessation of combustion can be achieved by reducing the content of the combustible component, reducing the concentration of the oxidizer, reducing the activation energy of the reaction, and, finally, reducing the temperature of the process.

In accordance with the above, there are the following main fire extinguishing methods:

Cooling a fire or combustion source below certain temperatures;

Isolation of the combustion source from air;

Reducing the concentration of oxygen in the air by diluting with non-flammable gases;

Slowing down (inhibiting) the rate of oxidation reaction;

Mechanical flame failure by a strong jet of gas or water, explosion;

Creation of fire containment conditions under which fire spreads through narrow channels, the diameter of which is less than the extinguishing diameter;

To achieve this, various fire extinguishing materials and mixtures (hereinafter referred to as extinguishing substances or extinguishing methods) are used.

The main methods of extinguishing are:

Water that can be supplied to the fire in solid or spray streams;

Foams (air-mechanical and chemical of different expansions), which are colloidal systems consisting of air bubbles (in the case of air-mechanical foam) surrounded by a film of water;

Inert gas diluents (carbon dioxide, nitrogen, argon, water vapor, flue gases);

Homogeneous inhibitors – halogenated hydrocarbons (freons) with a low boiling point;

Heterogeneous inhibitors - fire extinguishing powders;

Combined mixtures.

The choice of extinguishing method and its supply is determined by the class of fire and the conditions of its development.

Fire protection Fire resistance building structures Basic definitions

Fire resistance of a structure is the ability of a building structure to resist
fire exposure.

Fire resistance limit - time in minutes during which a building structure
retains its fire resistance.

The limiting state of a structure for fire resistance is the state of the structure when
in which it loses the ability to maintain one of its fire-fighting functions.

The following types of limit states of building structures for fire resistance are distinguished:

Loss of bearing capacity (R) due to collapse of the structure or the occurrence of extreme deformations;
loss of integrity (E) as a result of the formation of through cracks in structures through which combustion products or flames penetrate onto an unheated surface;
loss of thermal insulation ability (I) due to an increase in temperature on the unheated surface of the structure to maximum values ​​by an average of 140°C or at any point by 180°C. in comparison with the temperature of the structure before testing, or more than 220 ° C, regardless of the temperature of the structure before testing.

Enterprises use a large number of various substances for implementation of technological processes. Each type of substance has its own specific type of extinguishing agent. The main fire extinguishing agent is water . It is cheap, cools the combustion area, and the steam generated by the evaporation of water dilutes the burning medium. Water also has a mechanical effect on the burning substance - it breaks off the flame. The volume of steam generated is 1700 times greater than the volume of water used.

It is not advisable to extinguish flammable liquids with water, as this can significantly increase the area of ​​the fire. It is dangerous to use water when extinguishing live equipment to avoid electric shock. To extinguish fires, water fire extinguishing installations, fire trucks or water nozzles are used. Water is supplied to them from water pipes through fire hydrants or taps, and constant and sufficient water pressure in the water supply network must be ensured. When extinguishing fires inside buildings, internal fire hydrants are used, to which fire hoses are connected.

Fire heating is a set of devices for supplying water to the site of a fire. Regulated by the documents: SNiP 2.04.01 – 85. “Internal water supply and sewerage of buildings”; SNiP 2.04.02 – 84. “Water supply. External networks and structures."

The fire-fighting water supply system is designed to supply the amount of water required to extinguish a fire under appropriate pressure for at least 3 hours. On the external water supply network, at a distance of 4 - 5 meters from the buildings, hydrant taps are installed along the houses after 80 - 120 meters, in which flexible hoses with fire nozzles are connected in case of fire.

In accordance with the requirements of SNiP 2.04.01 - 85, an internal fire water supply which provides:

· availability of water in the parking areas of internal fire hydrants;

· Irrigation of premises with the calculated number of jets (to obtain jets with a productivity of up to 4 l/s, fire hydrants and hoses with a diameter of 50 mm should be used; for fire jets with a higher productivity - 65 mm).

Sprinkler and deluge systems are used for automatic water fire extinguishing. Sprinkler installations - This is a branched pipe system filled with water, which is equipped with sprinkler heads, whose outlets are sealed with a low-melting compound.

In the event of a fire, these holes themselves melt and irrigate the security zone with water. Deluge installations - this is a system of pipelines inside a building on which special heads with a diameter (8, 10, 13 mm) of a rosette type are installed, capable of irrigating up to 12 m2 of floor.

For extinguishing hard and liquid substances apply foam . Their fire extinguishing properties are determined by their expansion ratio (the ratio of the volume of foam to the volume of its liquid phase), durability, and dispersibility and viscosity. Depending on the conditions and method of production, the foam can be:

· chemical – this is a concentrated emulsion of carbon monoxide in an aqueous solution of mineral salts;

· air-mechanical (multiplicity 5 – 10), which is obtained from 5% aqueous solutions of foaming agents.

When extinguishing fires gases use carbon dioxide, nitrogen, argon, flue or exhaust gases, steam. Their fire extinguishing effect is based on diluting the air, that is, reducing the oxygen concentration. When extinguishing fires, carbon dioxide fire extinguishers (OU-5, OU-8, UP-2m) are used if the molecules of the burning substance include oxygen, alkali and alkaline earth metals. To extinguish electrical installations, it is necessary to use powder fire extinguishers (OP-1, OP-1O), the charge of which consists of sodium bicarbonate, talc and iron and aluminum stearators.

Extinguishing ferry used in liquidation small fires in open areas, in closed apparatus and with limited air exchange. The concentration of water vapor in the air should be approximately 35% by volume.

As one of the most common extinguishing agents at industrial facilities, it is sand , in particular, at enterprises sand is stored in special containers in a strictly defined place.

The required number of fire techniques is determined depending on the category of premises and external technological installations according to explosion and fire hazard, maximum protected area with one fire technique and fire class according to ISO No. 3941 - 77.

Primary fire extinguishing means are installed on special fire panels or in other accessible places. At the enterprise they are located: in fire cabinets, corridors, at exits from premises, as well as in fire hazardous places. To indicate the location of fire extinguishers at the facility, signs are installed in accordance with GOST 12.4.026 - 76 “Signal colors and safety signs.”

The main types of equipment designed to protect various objects from fires include alarm and fire extinguishing equipment.

Fire alarm

Fire alarms must quickly and accurately report a fire and indicate its location. The most reliable fire alarm system is electrical fire alarm. The most advanced types of such alarms additionally provide automatic activation of the fire extinguishing means provided at the facility. A schematic diagram of the electrical alarm system is shown in Fig. 1. It includes fire detectors installed in protected premises and connected to the signal line; reception and control station, power supply, sound and light alarms, as well as automatic fire extinguishing and smoke removal installations.

The reliability of the electrical alarm system is ensured by the fact that all its elements and the connections between them are constantly energized. This ensures monitoring of plant malfunctions.

Rice. 1 Schematic diagram of the electrical fire alarm system: 1- sensors-detectors; 2- receiving station; 3- backup power supply; 4- mains power supply; 5- switching system; 6- wiring; 7- actuator of the fire extinguishing system.

The most important element of the alarm system is fire detectors, which convert physical parameters characterizing a fire into electrical signals. Based on the method of actuation, detectors are divided into manual and automatic. Manual call points They produce an electrical signal of a certain shape into the communication line at the moment the button is pressed.

Automatic fire detectors are activated when parameters are changed environment at the time of the fire. Depending on the factor that triggers the sensor, detectors are divided into thermal, smoke, light and combined. The most widely used are heat detectors and sensitive elements, which can be bimetallic, thermocouple, or semiconductor.

Smoke fire detectors, reacting to smoke, have a photocell or ionization chambers as a sensitive element, as well as a differential photo relay. Smoke detectors come in two types: point detectors, which signal the appearance of smoke at the location where they are installed, and linear-volume detectors, which operate on the principle of shading the light beam between the receiver and the emitter.

Light fire detectors are based on fixing various components of the open flame spectrum. The sensitive elements of such sensors react to the ultraviolet or infrared region of the optical radiation spectrum.

The inertia of the primary sensors is important characteristic. Thermal sensors have the greatest inertia, light sensors the least.

A set of measures aimed at eliminating the causes of a fire and creating conditions under which continuation of combustion will be impossible is called fire extinguishing.

To eliminate the combustion process, it is necessary to stop the supply of either fuel or oxidizer to the combustion zone, or to reduce the supply of heat flow to the reaction zone. This is achieved:

1. Strong cooling of the combustion site or burning material with the help of substances (for example, water) with high heat capacity.

2. By isolating the combustion site from atmospheric air or reducing the oxygen concentration in the air by supplying inert components to the combustion zone.

3. The use of special chemicals that inhibit the rate of oxidation reaction.

4. Mechanical flame suppression using a strong jet of gas and water.

5. By creating fire barrier conditions under which the flame spreads through narrow channels, the cross-section of which is smaller than the extinguishing diameter.

To achieve the above effects, the following are currently used as extinguishing agents:

1. Water that is supplied to the fire source in a continuous or sprayed stream.

2. Various types of foams (chemical or air-mechanical), which are air or carbon dioxide bubbles surrounded by a thin film of water.

Fire safety- the state of the object in which the possibility of a fire is excluded, and in the event of its occurrence, the effect of dangerous factors on people is prevented, and the protection of material assets is ensured. Security fire safety It is an integral part government activities to protect human life and health, national wealth, the environment natural environment and is executed in accordance with the Law of Ukraine “On Fire Safety” dated December 17, 1993 and the Fire Safety Rules of Ukraine dated June 22, 1995 No. 400.

To protect various objects from fires, alarm and fire extinguishing means are used. The fire alarm system reports a fire quickly and accurately. It includes fire detectors, sound and light alarm systems, and ensures automatic activation of fire extinguishing and smoke extraction systems.

The most important element of the alarm system is fire detectors, which convert physical parameters into electrical signals. Depending on the factors that trigger the detectors, they are divided into thermal, smoke, light and combined.

Based on the method of connecting detectors to the receiving station, two systems are distinguished - beam and ring.

Telephone communication is widely used to call fire assistance. Operational communication between fire departments involved in extinguishing a fire, as well as between them and the fire department management, is carried out using short-wave or ultra-short-wave radio stations. This type of communication is especially convenient because the radio stations are installed directly on fire trucks, which ensures continuous communication with the control center.

A set of measures aimed at eliminating the causes of a fire and creating conditions under which continuation of combustion will be impossible is called fire extinguishing.

The main methods of extinguishing fires are based on following principles :

· reducing the temperature of flammable substances to a level below its combustion temperature;

· reduction of air oxygen concentration in the combustion zone to 14 - 15%;

· stopping the access of vapors and gases of flammable substances (most flammable substances, when heated, turn into a gas or vapor state).

To achieve such effects, the following are used as extinguishing agents:

· water supplied in a continuous or spray stream;

· different kinds foam (chemical or air-mechanical);

· inert gas diluents, for example: carbon dioxide, nitrogen, argon, water vapor, flue gases, etc.;

· homogeneous inhibitors - low-boiling halogenated hydrocarbons;

· heterogeneous inhibitors - fire extinguishing powders;

· combined formulations.

The most widely used is water.

Requirements for fire-fighting water supply systems are set out in SNiP 2.04.02-84 "Water supply. External networks and structures" and in SNiP 2.04.01-85 "Internal water supply and sewerage of buildings."

Water consumption for fire extinguishing consists of the costs of external and internal fire extinguishing. When calculating water consumption for external fire extinguishing, we proceed from the possible number of simultaneous fires in a populated area that can occur within three adjacent hours, depending on the number of residents and the number of storeys of buildings. Consumption rates and water pressure in internal water supply systems in public, residential and auxiliary buildings are calculated depending on their number of floors, length of corridors, volume, and purpose.

For indoor fire extinguishing, automatic fire extinguishing devices are used. Installations that use sprinkler or deluge heads as distribution devices have become widespread. The design and operation of these devices are presented in the works of S. V. Belov, O. N. Rusak.

Foam of the following composition is widely used as a fire extinguishing agent: 80% carbon dioxide, 19.7% liquid (water) and 0.3% foaming agent.

In addition to stationary installations, primary fire extinguishing agents can be used to extinguish fires in the initial stage of development. The most common primary fire extinguishing agents are foam, carbon dioxide, carbon dioxide-bromoethyl, aerosol and powder fire extinguishers, asbestos sheets, coarse fabrics (felts, felt), dried and sifted sand.

Primary fire extinguishing means should be placed near the places where they are most likely to be used, with easy access to them. In this case, it is advisable to place the primary fire extinguishing means on staircase landings at the entrance to the floors.