What can be cooked from squid: quick and tasty

Water is the most widely used and effective remedy extinguishing fires.

Table 1: Comparison of the effectiveness of fire extinguishing agents (OF)

As follows from Table 1, water and foam are the most effective extinguishing agents for class A and B fires (class B, mainly with water mist or ultra-sprayed water).

The basis of the fire extinguishing effect of water is its cooling capacity, which is due to its high heat capacity and heat of vaporization.

With the highest heat absorption capacity, water is the most efficient natural material for extinguishing fires. Water droplets, falling into the combustion center, go through two stages of heat absorption: when heated to 100 ° C and evaporated at a constant temperature of 100 ° C. For the first stage, 1 liter of water spends 335kJ of energy, for the second phase - evaporation and transformation into water vapor - 2260kJ.

When water penetrates into a high-temperature zone or when it hits a burning substance, it partially evaporates and turns into steam. During evaporation, the volume of water increases almost 1670 times, due to which the air is displaced by water vapor from the fire, and, as a result, the combustion zone is depleted in oxygen.

Water has a high thermal stability. its vapors only at temperatures above 1700 ° C can decompose into hydrogen and oxygen. In this regard, water extinguishing of most solid materials is safe, since their combustion temperature does not exceed 1300 ° C.

Water is capable of dissolving some vapors, gases and absorbing aerosols. Therefore, it can precipitate combustion products during fires in buildings. For these purposes, finely atomized and ultra-atomized (water mist) jets are used.

The good mobility of water makes it easy to transport through pipelines. Water is used not only to extinguish fires, but also to cool objects located near the fire. Thus, preventing their destruction, explosion and ignition.

Mechanism for extinguishing fires with water:

• cooling the surface and reaction zone of burning substances;
• dilution (phlegmatization) of the environment in the combustion zone with steam generated during evaporation;
• isolation of the combustion zone from the air;
• deformation of the reaction layer and flame rupture due to the mechanical action of a jet of water on the flame.

When extinguishing burning oil products in tanks with water, droplets supplied to the combustion center are essential. The optimum diameter of water droplets is 0.1mm when extinguishing gasoline; 0.3 mm - kerosene and alcohol; 0.5mm - transformer oil and petroleum products with a flash point above 60 ° C.

High efficiency of extinguishing combustible substances with a high combustion temperature and creating a high flame pressure is achieved through the use of a mixture of small and large water droplets. In this case, small drops, evaporating in the flame combustion zone, lower its temperature, and large drops, not having time to completely evaporate, reach the burning surface, cool it and, if their kinetic energy by the time of reaching the burning surface is high enough, destroy reaction layer.

Table 2: Scope of water for different classes of fire

Note: "1" is OK but not recommended; "2" - satisfactory; "3" - fits well; "4" - great; "-" - not suitable, "*" - for flammable and combustible liquids with a flash point up to 90 ° С; "**" - for flammable and combustible liquids with a flash point of more than 90 ° С; "***" - live electrical equipment.

Water should not be used to extinguish the following materials:

• potassium, sodium, lithium, magnesium, titanium, zirconium, uranium, plutonium;
• organoaluminum compounds (explosively reacts);
• organolithium compounds, lead azide, carbides, alkali metals, hydrides of a number of metals, magnesium, zinc, calcium carbides, barium (decomposition with the release of combustible gases);
• iron, phosphorus, coal;
• sodium hydrosulfite (spontaneous combustion occurs);
• sulfuric acid, termites, titanium chloride (strong exothermic effect);
• bitumen, sodium peroxide, fats, oils, petrolatum (increased combustion as a result of emission, splashing, boiling).

Oil products and many other organic liquids, when extinguished with water, float to its surface, as a result of which the area of ​​the fire can significantly increase. For example: in case of fire of oil products located in the tank, it is not recommended to extinguish with water. Oil products float above the water. Water, as a result of heating, turns into steam. Water vapor rises in portions, which causes splashing of burning oil products from the tank and makes it difficult for firefighters to access the fire.

Water disadvantages include heat freezing. To lower the freezing point, special additives (antifreeze), some alcohols (glycols), mineral salts (K 2 CO 3, MgCl 2, CaCl 2) are used. However, these salts increase the corrosiveness of water, so they are practically not used. The use of glycols significantly increases the cost extinguishing agent.

Foaming agents, antifreezes and other additives also increase the corrosivity and electrical conductivity of water. As protection against corrosion, special coatings can be applied to metal parts and pipelines, or corrosion inhibitors can be added to the water.

Expansion of the field of application of water for extinguishing electrotechnical equipment under voltage is possible when it is used in a fine and ultra-sprayed state.

Low wetting ability and low viscosity of water make it difficult to extinguish fibrous, dusty and especially smoldering materials. Materials with a large specific surface area, the pores of which contain the air necessary for combustion, are subject to smoldering. Such materials can burn at a highly reduced oxygen content in environment... The penetration of extinguishing agents into the pores of smoldering materials is usually rather difficult.

With the introduction of a wetting agent (sulfonate), the water consumption for extinguishing is reduced by four times, and the extinguishing time is halved.

In some cases, water quenching becomes very effective if it is thickened with, for example, sodium carboxymethyl cellulose or sodium alginate. An increase in viscosity to 1-1.5 N * s / m 2 allows reducing the quenching time by about 5 times. The best additives in this case are solutions of sodium alginate and sodium carboxymethylcellulose. For example, a 0.05% sodium carboxymethyl cellulose solution provides a significant reduction in water consumption for fire extinguishing. If, under certain conditions of extinguishing with ordinary water, its consumption is from 40 to 400 l / m 2, then when using "Viscous" water - from 5 to 85 l / m 2. The average damage from fire (including as a result of exposure to water on materials) is reduced by 20%.

The most commonly used additives to improve the efficiency of water use are:

• water-soluble polymers to increase adhesion to burning objects ("Viscous water");
• polyoxyethylene to increase the throughput of pipelines ("slippery water");
• inorganic salts to improve the extinguishing efficiency;
• antifreeze and salt to reduce the freezing point of water.

Currently, one of the most promising areas in the field fire protection an object for various purposes is the use of fine and ultra-sprayed water as a means of extinguishing fires. In this form, water is capable of absorbing aerosols, precipitating combustion products and extinguishing not only burning solids, but also many flammable liquids.

When water is supplied in a fine or ultra-sprayed state, the greatest fire extinguishing effect is achieved. The use of fine and ultra-sprayed water is especially important at facilities where high extinguishing efficiency is required, there are restrictions on water supply, and it is important to minimize damage from water spills.

With the help of fine and ultra-sprayed water, protection of many especially socially and industrially significant objects can be ensured. These include: living quarters, hotel rooms, offices, educational institutions, hostels, administrative buildings, banks, libraries, hospitals, computer centers, museums and exhibition galleries, sports complexes, industrial facilities, i.e. such objects where fire extinguishing must be carried out in the initial stage rather quickly and with low water consumption.

Additional advantages of using spray water over a compact jet or spray stream:

• the ability to extinguish almost all substances and materials, with the exception of substances that react with water with the release of thermal energy and combustible gases;
• high extinguishing efficiency due to the increased cooling effect and uniform water irrigation of the fire;
• minimum water consumption - insignificant consumption allows you to avoid significant damage from the consequences of the spill and ensure the possibility of using it subject to the water limit;
• shielding of radiant thermal radiation - use for the protection of service personnel taking part in extinguishing a fire, personnel of fire departments, load-bearing and enclosing structures, as well as nearby material assets;
• dilution of combustible vapors and a decrease in the concentration of oxygen in the combustion zone as a result of the intense formation of water vapor;
• decrease in temperature in rooms in case of fire in them;
• uniform cooling of overheated metal surfaces of load-bearing structures due to the high specific surface area of ​​drops - eliminates their local deformation, loss of stability and destruction;
• effective absorption and removal of toxic gases and fumes (smoke deposition);
• low electrical conductivity of ultra-finely sprayed water - makes it possible to use it as an effective fire extinguishing agent on energized electrical installations;
• environmental cleanliness and toxicological safety in combination with the protection of people from the effects of hazardous fire factors - allows personnel to save value during the operation of an automatic fire extinguishing system.

Ultra-atomized water in the combustion zone evaporates intensively. A protective layer of water vapor can isolate the combustion zone, preventing the access of oxygen. When the oxygen concentration in the combustion center drops to 16-18%, the fire self-extinguishes.

Used literature: L.M. Meshman, V.A.Bylinkin, R.Yu. Gubin, E.Yu. Romanova. Automatic water and foam fire extinguishing systems. Design. Moscow city. - 2009

Ticket number 8 Question 2 Water as a fire extinguishing agent: physical and chemical parameters and their analysis, the mechanism for stopping combustion, scope, methods and techniques of water supply

Water is the main extinguishing agent for cooling, the most affordable and versatile. When it hits a burning substance, water partially evaporates and turns into steam (1 liter of water turns into 1700 liters of steam), due to which the oxygen in the air is displaced from the fire zone by water vapor. The fire extinguishing efficiency of water depends on the way it is supplied to the fire site (solid or spray jet). The greatest fire extinguishing effect is achieved when water is supplied in a sprayed state, because the area of ​​simultaneous uniform cooling increases. The sprayed water heats up quickly and turns into steam, taking away a large amount of heat. Sprayed water jets are also used to reduce the temperature in rooms, to protect against thermal radiation (water curtains), to cool heated surfaces building structures, structures, installations, as well as for the deposition of smoke.

1) Water has high heat capacity (4187 J / kg deg) under normal conditions and high heat of vaporization (2236 kJ / kg), therefore, getting into the combustion zone, on a burning substance, water takes away a large amount of heat from the burning materials and combustion products. At the same time, it partially evaporates and turns into steam, increasing in volume 1700 times (from 1 liter of water during evaporation, 1700 liters of steam are formed), due to which the reactants are diluted, which in itself contributes to the cessation of combustion, as well as the displacement of air from the zone the source of the fire.

2) Water has high thermal stability ... Its vapors only at temperatures above 1700 0 C can decompose into oxygen and hydrogen, thereby complicating the situation in the combustion zone. Most of the combustible materials burn at temperatures not exceeding 1300-1350 0 С and extinguishing them with water is not dangerous.

3) Water has low thermal conductivity , which contributes to the creation of reliable thermal insulation on the surface of the burning material. This property, in combination with the previous ones, makes it possible to use it not only for extinguishing, but also for protecting materials from ignition.

4) Low viscosity and incompressibility of water allow it to be fed through the sleeves over considerable distances under high pressure.

5) Water capable of dissolving some vapors, gases and absorbing aerosols ... This means that water can precipitate combustion products on fires in buildings. For these purposes, sprayed and finely atomized jets are used.

6) Some flammable liquids (liquid alcohols, aldehydes, organic acids, etc.) are soluble in water, therefore, mixing with water, they form non-flammable or less flammable solutions.

7) Water with the absolute majority of flammable substances does not enter into a chemical reaction .

Negative properties of water as a fire extinguishing agent:

1) The main disadvantage of water as extinguishing agent thing is due to high surface tension (72.8 · 10 -3 J / m 2) she poorly wets solid materials and especially fibrous substances ... To eliminate this disadvantage, surfactants (surfactants), or, as they are called, wetting agents, are added to the water. In practice, surfactant solutions are used, the surface tension of which is 2 times less than that of water. The use of solutions of wetting agents allows to reduce the consumption of water for extinguishing a fire by 35-50%, to reduce the extinguishing time by 20-30%, which ensures extinguishing with the same volume of extinguishing agent over a larger area. For example, the recommended concentration of wetting agent in aqueous solutions for extinguishing fires:

Ø Foam concentrate PO - 1.5%;

Ø Foam concentrate PO-1D - 5%.

2) Water has relatively high density (at 4 ° С - 1 g / cm 3, at 100 ° С - 0.958 g / cm 3), which limits and sometimes excludes its use for extinguishing petroleum products with a lower density and insoluble in water.

3) The low viscosity of water contributes to the fact that a significant part of it escapes from the fire without significantly affecting the process of stopping combustion. If the viscosity of water is increased to 2.5 · 10 -3 m / s, then the extinguishing time will significantly decrease and the coefficient of its use will increase by more than 1.8 times. For these purposes, additives from organic compounds are used, for example, CMC (carboxymethyl cellulose).

4) Metallic magnesium, zinc, aluminum, titanium and its alloys, thermite and electron during combustion create a temperature in the combustion zone that exceeds the thermal resistance of water, i.e. more than 1700 0 С. Their extinguishing with water jets is unacceptable.

5) Water electrically conductive , therefore, it cannot be used to extinguish live electrical installations.

6) Water reacts with certain substances and materials (peroxides, carbides, alkali and alkaline earth metals, etc.) , which therefore cannot be extinguished with water.

Water vapor found wide application in stationary extinguishing installations in rooms with a limited number of openings, with a volume of up to 500 m 3 (drying and painting chambers, holds of ships, pumping stations for pumping oil products, etc.), technological installations for outdoor fire extinguishing, at the facilities of the chemical and oil refining industries. Its fire extinguishing volume fraction is 35%. In addition to the diluting effect, water vapor has a cooling effect and mechanically breaks the flame off.

Water mist(droplet diameter less than 100 microns) - to obtain it, pumps are used that create a pressure of more than 2-3 MPa (20-30 atm.) and special spray nozzles.

Once in the combustion zone, finely sprayed water evaporates intensively, reducing the oxygen concentration and diluting the combustible vapors and gases involved in combustion. The use of water mist is very effective, since it also has a cooling effect in addition to the diluting effect. For example, after 4 minutes of operation of one barrel high pressure in a closed room, the temperature dropped from 700 to 100 0 C.

To obtain continuous sprayed water, foam and powder jets, fire nozzles are used. They are divided into hand-held and monitored. The combined barrel is used to obtain a continuous and spray jet.

Hand-held barrels of the RS-50 and RS-70 types are used to create compact water jets, differ in geometric dimensions and nozzle diameters, and are widely used in the national economy.

Air-foam barrel SVP is designed to produce air-mechanical foam. It is reliable in operation, simple in design, and is widely used in extinguishing fires.

PLC-P20 portable monitor barrel is designed to obtain a powerful compact water jet for extinguishing developed fires in settlements, in timber warehouses, timber and woodworking industries and other facilities.

Sprayed water jets are used to reduce the temperature in rooms, to protect against thermal radiation (water curtains), to cool the heated surfaces of building structures, structures, installations, as well as for the deposition of smoke.

For uniform cooling of the combustion area, a continuous stream of water is moved from one area to another. When the flame is knocked down from the moistened combustible substance and combustion is stopped, the jet is transferred to another place.

Urgent fire containment measures are also protection of metal load-bearing structures from collapse, cooling of heated devices and communications, reduction of heat radiation from a burning gas torch, and other actions to prevent an explosion or dangerous heating of technological devices and structures.

Gunmen, working at the boundaries of localization of a fire inside a building, must supply jets of water to the greatest possible depth along the flame front and gradually move forward. Working on the proposed boundaries of localization of open fires, while protecting the walls and roofs of neighboring buildings and structures from ignition, the barrels, maneuvering with their trunks, irrigate not only protected areas with water, but also burning surfaces deep into the propagating flame front.

Ticket number 9 Question 1 Storming ladder: purpose, device, technical specifications, terms and procedure of testing

Assault ladder (LSh) designed to lift firefighters along outside wall on the floors of buildings and structures, to ensure work when opening the roof on steep roofs, as well as for training sessions and competitions. The most successful assault ladder is used in combination with a three-knee retractable ladder or auto ladder.

The assault ladder consists of two parallel bowstrings rigidly connected thirteen transverse support steps, hook with teeth for hanging onto the supporting surface(window sills, openings and ledges of buildings and structures), three steel ties (for LSh with wooden steps, at the ends and in the middle of the bowstrings). The lower ends of the bowstrings are pointed and equipped with metal shoes.

Bowstrings and steps of a metal assault ladder are made of aluminum alloy. The steps are fixed in the holes of the bowstrings by flaring.

Water is one of the most effective means of extinguishing fires. This is explained by a number of its inherent specific properties, the combination of which makes it possible to successfully extinguish even the most complex fires: high specific heat capacity (4200 J / (kg ∙ K)) and high specific heat of vaporization (2.3 10 6 J / kg). Both factors determine the high heat-absorbing capacity of water, which, when supplied to the combustion zone, leads to a decrease in the temperature of the latter. When the temperature of the combustion source is lower than the self-ignition temperature of the combustible substance, fire extinguishing occurs. In addition, at a temperature in the fire center of ~ 1700 ° C from one volume of water ~ 1760 volumes of water vapor are formed, which, due to the dilution of the oxidizer and the combustible substance in the flame, leads to a decrease in the concentration of oxygen and combustible substance. When the oxygen concentration is less than MWC and (or) a combustible substance is less than NKPRP, fire extinguishing occurs.

However, water, as a fire extinguishing agent, cannot be used where there are alkali metals (when they interact with water, they ignite), calcium carbide (when interacting with water, a flammable acetylene gas is released), electrical installations that are energized (in contact with water, short closure and defeat of people electric shock). You cannot extinguish flammable liquids with water, the density of which is less than the density of water, for example, oil and oil products, since water sinks into a layer of burning liquid and does not perform its fire extinguishing functions.

Some of these negative factors of fire extinguishing with water, for example, the impossibility of extinguishing burning oil products, can be eliminated by using it not in the form of compact jets, but in the form of foam or spraying to droplets of micron and submicron sizes. At the same time, the efficiency of water use increases significantly, since the heat exchange area in the "fire center - water" system increases, and, consequently, the rate of heat absorption and vaporization. In addition, both foam and aerosol cloud with a water dispersed phase are retained for a longer time in the combustion zone, for example, foam covers a solid burning object up to 40 min.

Foam consisting of water, foaming agent and air (air-mechanical foam) is obtained using foam generators, one of the device options for which is shown in Fig. 1.

Rice. 1. Generator of air-mechanical foam of medium expansion ГПС - 200.

1 - nozzles; 2 - mesh cassette; 3 - generator case; 4 - sprayer body; 5 - sprayer; 6 - connecting head.

A more effective fire extinguishing agent is chemical foam, in which gas bubbles formed by a thin film of water are filled with carbon dioxide inert to combustion. The use of such foam is widespread mainly in hand-held fire extinguishers of the OHP-10 type, the design and principle of operation of which will be discussed below.

As mentioned above, even more effective way the use of water as a fire extinguishing agent is its spraying, i.e. creation of an aerosol system, the dispersed phase of which is the smallest droplets of water. Such fire extinguishing is voluminous and allows you to cover a larger area of ​​the fire with less water compared to traditional methods.

Modern technologies volumetric water fire extinguishing uses a unique pneumoacoustic method of creating a water aerosol using a special nozzle that creates a so-called "protective fog" (fine water mist). Water mist effectively affects all factors of extinguishing a fire: it quickly reduces its temperature; concentration of flammable gases and vapors, as well as oxygen. This happens due to an increase in the contact surface of water with a burning medium by billions of times compared to the traditional use of water, which leads to immediate evaporation of water. At the same time, the fire-extinguishing component has a penetrating ability of gas, does not harm people, property and the environment, does not cause short circuits in the wiring.

The main extinguishing agent in fire extinguishing is water. It is almost universally available, cheap and highly effective. When it is supplied to the combustion zone, water cools the most heated layer of the substance. At the same time, it partially evaporates and turns into steam, due to which the dilution of the reacting substances occurs, which in itself contributes to the cessation of combustion, as well as the displacement of air from the zone of the fire.

Water in the form of atomized and finely dispersed (finely dispersed) jets possesses increased efficiency when extinguishing a fire. Once in the combustion zone, it intensively evaporates, reducing the oxygen concentration and diluting the combustible vapors and gases involved in combustion. In addition, the smallest water droplets moving at high speed penetrate well into the depth of porous materials.

Along with this, water also has negative properties. The main disadvantage of water as a fire extinguishing agent is that, due to its high surface tension, it poorly wets solid materials and especially fibrous substances. To eliminate this disadvantage, surfactants (wetting agents, foaming agent) are added to water to obtain solutions, the surface tension of which is less than that of water.

With some substances and materials (see table), water reacts with the release of hydrogen, combustible gases, a large amount of heat, etc. Such substances cannot be extinguished with water.

Table. Substances and materials, during extinguishing of which it is dangerous to use water and other fire-extinguishing substances based on water