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Class “B” fires are the combustion of liquid substances that can be soluble in water (alcohols, acetone, glycerin) and insoluble (gasoline, oil, fuel oil).

Just like solids, flammable liquids release vapors when burned. The process of vaporization differs only in speed - in liquids it happens much faster.

The level of danger of flammable liquids depends on the flash point - the lowest temperature of a condensed substance at which vapors above it are able to ignite under the influence of an ignition source, but combustion does not occur after it is eliminated. Also, the degree of danger of flammable liquids is influenced by the ignition temperature, flammability range, evaporation rate, chemical reactivity under the influence of heat, density and vapor diffusion rate.

Flammable liquids are considered to be liquids with a flash point of up to 61°C (gasoline, kerosene), flammable liquids are those with a flash point above 61°C (acids, vegetable and lubricating oils).

Class B fires

The following materials can cause a class B fire:

• paints and varnishes;
• flammable and combustible liquids;
• liquefied solids(paraffins, stearins).

1. Varnishes, paints, enamels. Liquids on water based less dangerous than oil ones. The flash point of oils contained in paints, varnishes and enamels is quite high (about 200°C), but the flammable solvents contained in them flare up much earlier - at a temperature of 32°C.

The colors burn well, with highlighting large quantity thick black smoke and toxic gases. When paints or varnishes catch fire, explosions often occur in the containers in which they are located.

It is impossible to extinguish paints, varnishes and enamels with water due to the low flash point. Water can only be used to cool surrounding objects or extinguish dry paint.

The burning of paints and varnishes is suppressed with foam, in some cases with carbon dioxide or powder fire extinguishers.

1. Flammable and combustible liquids. Their combustion is accompanied by the release of non-standard combustion products characteristic of such liquids.

Alcohols burn with a clear blue fire with a small amount of smoke.

The combustion of liquid hydrocarbons is characterized by an orange flame and the formation of thick, dark smoke.

Esters and terpenes burn accompanied by boiling on their surface.

During the combustion of petroleum products, oils and fats, a toxic, irritating gas, acrolein, is released.

Extinguishing flammable and combustible liquids is not an easy task, and each fire has its own characteristics and sequence of its suppression. First, you need to block the flow of liquid into the fire.

Surrounding objects and containers with burning liquids should be cooled with water. There are different ways to extinguish a Class B fire:

• a foam or powder fire extinguisher or a spray of water can handle a small fire;
• in case of large spreading of flammable liquid, it is better to use powder fire extinguishers in conjunction with fire hoses to supply foam;
• if a liquid burns on the surface of water, then you must first limit its spreading, and then cover the flame with foam or a powerful water jet;
• When extinguishing equipment operating on liquid fuel, it is necessary to use sprayed water or foam.

Paraffins and other similar petroleum products. Extinguishing them with water is strictly prohibited and dangerous. Small fires can be suppressed with carbon dioxide fire extinguishers. Large fires - with the help of foam.

Behind last decade The tank farm for storing oil and petroleum products has increased, a significant number of underground reinforced concrete tanks with a volume of 10, 30 and 50 thousand m3, metal above-ground tanks with a volume of 10 and 20 thousand m3 have been built, tank designs with pontoons and floating roofs with a volume of 50 thousand m3 have appeared. 3, in the Tyumen region, reservoirs with a volume of 50 thousand m were built on a pile foundation.

Means and tactics for extinguishing oil and petroleum product fires are being developed and improved.

Tank farms are divided into 2 groups.

The first is raw material parks of oil refineries and petrochemical plants; bases of oil and petroleum products. This group is divided into 3 categories depending on the capacity of the park, thousand m3.

St. 100........................................ 1

20-100.................................... 2

Up to 20................................................... 3

The second group is tank farms, which are part of industrial enterprises, the volume of which is for underground tanks with flammable liquids 4000 (2000), for gas liquids 20,000 (10,000) m 3. Figures in parentheses are for above-ground tanks.

Classification of tanks.According to the material: metal, reinforced concrete. By location: above ground and underground. By form: cylindrical, vertical, cylindrical horizontal, spherical, rectangular. By pressure in the tank: at a pressure equal to atmospheric, the tanks are equipped with breathing equipment, at a pressure above atmospheric, i.e. 0.5 MPa, with safety valves.

Reservoirs in parks can be placed in groups or separately.

For DVZh total capacity

a group of tanks with a floating roof or pontoons is no more than 120, and with fixed roofs - up to 80 thousand m 3.

For gas liquids, the capacity of a group of tanks does not exceed 120,000 m3.

The gaps between above-ground groups are 40 m, underground - 15 m. Driveways are 3.5 m wide with hard surfaces.

Fire-fighting water supply must ensure water flow for cooling ground-based tanks (except for tanks with a floating roof) over the entire perimeter in accordance with SNiP.

The water supply for extinguishing should be 6 hours for above-ground tanks and 3 hours for underground tanks.

Sewerage in the embankment is calculated at total consumption: produced water, atmospheric water and 50% of the calculated flow rate for cooling tanks.

Features of fire development. Fires in tanks usually begin with an explosion of a steam-air mixture in the gas space of the tank and the breaking off of the roof or an outbreak of a “rich” mixture without tearing off the roof, but with a violation of the integrity of its individual places.

The force of the explosion is usually greater in those tanks where there is a large gas space filled with a mixture of oil product vapors and air (low liquid level).

Depending on the force of the explosion in a vertical metal tank, the following situation may be observed:

the roof is completely torn off and thrown to the side at a distance of 20-30 m. The liquid burns over the entire area of ​​the tank;

the roof rises slightly, comes off completely or partially, then remains in a semi-submerged state in the burning liquid (Fig. 12.11);

the roof is deformed and forms small gaps at the points of attachment to the tank wall, as well as in the weld

ny seams of the roof itself. In this case, flammable liquid vapors burn above the formed cracks. In the event of a fire in reinforced concrete buried (underground) tanks, the explosion causes destruction of the roof, in which holes are formed large sizes, then during a fire the coating may collapse over the entire area of ​​the tank due to high temperature and the impossibility of cooling their supporting structures.

In cylindrical horizontal, spherical tanks, the bottom most often collapses during an explosion, as a result of which the liquid spills over a large area, creating a threat to neighboring tanks and structures.

The condition of the tank and its equipment after a fire occurs determines the method of extinguishing and

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According to the “Rules for the Construction of Electrical Installations”, the definition of a flammable liquid sounds quite succinct - it is a liquid that flares up at a temperature above 61℃, and then continues to burn independently without external initiation or influence. A flammable liquid according to the PUE is a gas liquid with a flash temperature of no more than 61℃, and those that have an evaporation pressure of at least 100 kPa at T = 20℃ are explosive.

GCs are classified as flammable materials, but they are explosive if they are heated to flash temperatures during the technological process.

Such preliminary categorization of protection objects allows, at the design stage and start of operation, to make organizational and technical decisions on the selection, installation, and installation of products that meet the requirements. regulatory documents, for example, such as types, types, incl. explosion-proof flame detectors, smoke detectors for alarm systems, stationary fire extinguishing systems; to eliminate primary sources of fire in premises with the presence of flammable liquids and gases.

Additional information in the table:

Source: Koshmarov Yu.A. Predicting indoor fire hazards: A tutorial

Fire class of flammable liquids

Due to their parameters, flammable and combustible liquids when burning both in enclosed spaces of production, warehouse buildings, technological structures, and in open industrial areas; where external oil processing plants are located, gas condensate, chemical organic synthesis apparatus, storage facilities for raw materials, finished commercial products if fires occur or the fire spreads, it is classified as class B.

The fire class symbol is applied to containers with flammable liquids, flammable liquids, and their storage facilities, which allows you to quickly right choice, reducing the time for reconnaissance, localization and elimination of fires of such substances and their mixtures; minimize material damage.

Classification of flammable liquids

The flash point of a flammable liquid is one of the main parameters for classifying and assigning flammable liquids to one type or another.

GOST 12.1.044-89 defines it as the lowest temperature of a condensed substance that has vapor above the surface that can flare up in air environment indoors, or in an open space when a low-calorie source of open flame is presented; but a stable combustion process does not occur.

And the flash itself is considered to be the instantaneous burning out of an air mixture of vapors and gases over the surface of a flammable liquid, which is visually accompanied by a short period of visible glow.

The value of T℃, obtained as a result of tests, for example, in a closed laboratory vessel, at which the gas liquid flares up, characterizes its fire and explosion hazard.

Important parameters for GZh, LVZh specified in this state standard, also the following parameters:

• The ignition temperature is lowest temperature flammable liquids that emit flammable gases/vapors with such intensity that when a source of open fire is brought in, they ignite and continue to burn when it is removed.
• This indicator is important when classifying flammability groups of substances, materials, hazards technological processes, equipment in which gas fluids are involved.
• T of self-ignition is minimum temperature GZ, in which self-ignition occurs, which, depending on the prevailing conditions in the protected room, storage facility, building technological equipment– the apparatus, installation may be accompanied by combustion open flame and/or explosion.
• The data obtained for each type of gas liquid capable of self-ignition allows you to select suitable types explosion-proof electrical equipment, incl. for installations of buildings, structures, structures; for the development of explosion and fire safety measures.

For information: “PUE” defines a flash by the rapid burnout of a flammable air mixture without the formation of compressed gas; and an explosion is an instantaneous combustion with the formation of compressed gases, accompanied by the appearance of a large amount of energy.

The speed and intensity of evaporation of flammable liquids and flammable liquids from the free surface with open tanks, containers, and process plant housings are also important.

Fires of gas liquids are also dangerous for the following reasons:

• These are spreading fires, which are associated with the spilling, free spreading of flammable liquids across the premises or territory of enterprises; if measures for isolation are not taken - diking of storage tanks and external technological installations; the presence of construction barriers with walls installed in the openings.
• Fires of gas liquids can be both local and volumetric, depending on the type, storage conditions, and volume. Since volumetric combustion intensively affects load-bearing elements buildings, structures, then it is necessary.

You should also:

• Install on air ducts ventilation systems premises where there are gas liquids to limit the spread of fire through them.
• Conduct for shift, operational/duty personnel, organize those responsible for the fire safety condition of storage, processing, transportation, transit of flammable liquids, gas, leading specialists, engineering staff; conducting regular practical training with members of the DPD of enterprises and organizations; tighten the process, carry out strict control over the place where they are held, incl. after finishing.
• Install on smoke and exhaust pipes of heating, power units, furnaces, install on pipelines of the technological chain for transporting flammable liquids and gases across the territory of production enterprises.

The list, of course, is far from complete, but all the necessary measures can be easily found in the regulatory and technical base of documents on industrial safety.

How to properly store flammable and liquid liquids is probably the question most people ask. The answer can be found in the “Technical Regulations on Fire Safety Requirements” dated July 22, 2008 No. 123-FZ, in Table 14 Categories of warehouses for storing oil and petroleum products. More detailed information on storage and distance to objects, is presented in. (SP 110.13330.2011)

Class B fires are extinguished, according to the standards, as follows:

• Air-mechanical foam obtained from aqueous solutions of a foaming agent. They are especially effective for extinguishing industrial and warehouse buildings.
• Fire extinguishing powder, what is it used for.
• Used for small premises and compartments, for example, fuel and lubricants warehouses, engine rooms.

The use of sprayed water to extinguish the flames of gasoline and other gas liquids with a low flash point is difficult, since drops of water cannot cool the heated surface layer below the flash point. The decisive factor in the mechanism of the fire extinguishing action of VMP is the insulating ability of the foam.

When the liquid combustion mirror is covered with foam, the flow of liquid vapor into the combustion zone stops, and combustion stops. In addition, the foam cools the heated layer of liquid with the released liquid phase - the compartment. The smaller the foam bubbles and the higher the surface tension of the foam solution, the higher the insulating ability of the foam. Inhomogeneity of the structure and large bubbles reduce the effectiveness of the foam.

Elimination of fires of flammable liquids and gases is also carried out for particularly important protection objects; as well as for premises with different types of fire loads, the fire of which is difficult or impossible to eliminate with one fire extinguishing agent.

Table of supply intensity of a 6 percent solution when extinguishing flammable liquids with air-mechanical foam based on foaming agent PO-1

According to . V.P. Ivannikov, P.P. Clews,

Notes:

The asterisk indicates that extinguishing with low expansion foam oil and petroleum products with a flash point below 280 C is allowed in tanks up to 1000 m 3, excluding low levels (more than 2 m from the upper edge of the tank side).

When extinguishing oil products using the foaming agent PO-1D, the intensity of supply of the foaming solution increases by 1.5 times.

The explosion and fire hazard of substances depends on their state of aggregation (gaseous, liquid, solid), physical and chemical properties, storage and use conditions.

The main indicators characterizing fire danger flammable gases are the concentration limits of ignition, ignition energy, combustion temperature, normal flame propagation speed, etc.

Combustion of a mixture of gas and air is possible within certain limits, called ignition concentration limits. The minimum and maximum concentrations of flammable gases in the air that can ignite are called the lower and upper flammability limits, respectively.

Ignition energy is determined by the minimum energy of an electric discharge spark that ignites a given gas-air mixture. The amount of ignition energy depends on the nature of the gas and its concentration. Ignition energy is one of the main characteristics of explosive environments when addressing issues of ensuring the explosion safety of electrical equipment and developing measures to prevent the formation of static electricity.

Combustion temperature- this is the temperature of the product of a chemical reaction during combustion of the mixture without heat loss. It depends on the nature of the combustible gas and the concentration of its mixture. The highest combustion temperature for most combustible gases is 1600-2000 °C.

The normal speed of flame propagation is the speed at which the boundary surface between the burnt and unburnt parts of the mixture moves relative to the unburned part. Numerically, the normal flame speed is equal to the amount (volume) of the combustible mixture burned per unit flame area per unit time. The normal flame speed depends on the nature of the gas and the concentration of its mixture. For most flammable gases, normal flame speed is in the range of 0.3-0.8 m/s.

Normal flame speed is one of the main physical and chemical characteristics that determine the properties of the mixture and determine the combustion rate and, accordingly, the explosion time. The higher the normal flame speed, the less time explosion and even more stringent its parameters.

Combustion of flammable and combustible liquids occurs only in vapor phase. Combustion of vapors in air, as well as gases, is possible in a certain concentration range. Since the maximum possible vapor content in the air cannot be greater than in the saturated state, the concentration limits of ignition can be expressed in terms of temperature. The liquid temperature values ​​at which the concentration of saturated vapors in the air above the liquid is equal to the concentration limits of ignition are called temperature limits of ignition (lower and upper, respectively).

Thus, for a liquid to ignite and burn, it is necessary that the liquid be heated to a temperature not less than the lower ignition temperature limit. Once ignited, the rate of evaporation must be sufficient to maintain continuous combustion. These features of the combustion of liquids are characterized by flash and ignition temperatures.

Flash point is the lowest value of liquid temperature at which a steam-air mixture is formed above its surface, capable of igniting from an external ignition source. In this case, stable combustion of the liquid does not occur.

Based on their flash point, liquids are divided into flammable liquids (flammable liquids). the flash point of which does not exceed 45 °C (alcohols, acetone, gasoline, etc.) and flammable fuels (GL), the flash point of which is more than 45 °C (oils, fuel oils, glycerin, etc.).

Ignition temperature is the lowest value of liquid temperature at which the intensity of its evaporation is such that after ignition external source independent flame combustion occurs. For flammable liquids, the ignition temperature is usually 1-5 °C higher than the flash point, and for flammable liquids this difference can reach 30-35 °C.

Steam-air mixtures, as well as gas-air mixtures, are explosive. Their explosiveness is characterized by parameters that determine the explosiveness of gas-air mixtures - ignition energy, combustion temperature, normal flame propagation speed, etc.

Fire danger solid combustibles substances and materials are characterized by the calorific value of 1 kg of the substance, combustion, self-ignition and ignition temperatures, burnout rate and combustion propagation over the surface of materials.

The fire and explosive properties of dusts are determined by the concentrations of the dust-air mixture, the presence of an ignition source with sufficient thermal energy, the size of dust particles, etc.

Small particles of solid flammable substances measuring 10~5-10~7 cm can remain suspended in the air for a long time, forming a dispersed system - an air suspension. To ignite an air suspension, it is necessary that the concentration of dust in the air is not less than the lower concentration limit of ignition. The upper concentration limit of ignition of the dust-air mixture in most cases is very high and difficult to achieve (for peat dust - 2200 g/m3, powdered sugar - 1350 g/m3).

The thermal energy of the ignition source to ignite the dust-air mixture must be on the order of several MJ or more.

Depending on the value of the lower concentration limit of ignition, dusts are divided into explosive and fire hazardous. Explosive dusts include dusts with a lower flammable concentration limit of up to 65 g/m3 (dust of sulfur, sugar, flour), and fire hazardous dusts include dusts with a lower flammable limit above 65 g/m3 (tobacco and wood dust).

The fire hazard of substances and materials is characterized by; and such properties as the tendency of some substances and materials to electrify and spontaneously ignite when in contact with air (phosphorus, sulfur metals, etc.). water (sodium, potassium, calcium carbide, etc.) and with each other (methane + chlorine, nitric acid + sawdust etc.).

The fire hazard of non-combustible substances and materials is determined by the temperature at which they are processed, the possibility of generating sparks, flames, radiant heat, as well as loss of load-bearing capacity and destruction.

Flammable liquids are liquids that emit vapors at a temperature of 61°C and below, for example ethyl ether, gasoline, acetone, alcohol.

Flammable liquids are liquids whose flash point exceeds 61°C. Heavy oil products such as diesel fuel and fuel oil are considered flammable liquids. The flash point range of these liquids is 61°C and above. Flammable liquids also include some acids, vegetable and lubricating oils, the flash point of which exceeds 61°C.

Flammability characteristics.

It is not the flammable liquids themselves that burn and explode when mixed with air, but their vapors. Upon contact with air, these liquids begin to evaporate, the rate of which increases when they are heated. To reduce the risk of fire, they should be stored in closed containers. When using liquids, care must be taken to ensure that exposure to air is as minimal as possible.

Explosions of flammable vapors most often occur in a confined space such as a container or tank. The force of the explosion depends on the concentration and nature of the steam, the amount of steam-air mixture and the type of container in which the mixture is located.

Flash point is the generally accepted and most important factor, which determines the danger posed by a flammable liquid.

The rates of combustion and flame propagation of flammable liquids are somewhat different from each other. The burnout rate of gasoline is 15.2-30.5, kerosene 12.7-20.3 cm of layer thickness per hour. For example, a layer of gasoline 1.27 cm thick will burn out in 2.5-5 minutes.

Combustion products.

During the combustion of flammable liquids, in addition to the usual combustion products, some specific combustion products are formed, characteristic of these liquids. Liquid hydrocarbons typically burn with an orange flame and produce thick clouds of black smoke. Alcohols burn with a clear blue flame, producing a small amount of smoke. The combustion of some ethers is accompanied by violent boiling on the surface of the liquid, and extinguishing them presents significant difficulty. When petroleum products, fats, oils and many other substances burn, acrolein is formed - a highly irritating toxic gas.

Extinguishing.

If a fire occurs, quickly shut off the source of flammable liquid. This will stop the flow of flammable substances to the fire, and people involved in fighting the fire will be able to use one of the fire extinguishing methods listed below.

Cooling. It is necessary to cool containers and areas exposed to fire using a spray or compact stream of water from the fire water main.

Extinguishing. A layer of foam is used to cover the burning liquid and prevent its vapors from reaching the fire. In addition, steam or carbon dioxide. By turning off ventilation, the supply of oxygen to the fire is reduced.

Slows down the spread of flames. Fire extinguishing powder must be applied to the burning surface.

When extinguishing fires involving the combustion of flammable liquids, the following should be followed:

1. If there is a slight spread of burning liquid, it is necessary to use powder or foam fire extinguishers or a spray of water.

2. In case of significant spreading of burning liquid, powder fire extinguishers, foam or spray jets of water, must be used. Equipment exposed to fire should be protected using a jet of water.

3. When a burning liquid spreads over the surface of water, it is necessary, first of all, to limit it. If you succeed in doing this, you need to create a layer of foam covering the fire. Alternatively, you can use a spray of water to

4. To prevent combustion products from escaping from inspection and measuring hatches, it is necessary to use foam, powder, high or medium expansion foam, or a spray of water applied horizontally across the hole until it can be closed.

5. To fight fires in cargo tanks, a deck foam extinguishing system and (or) a carbon dioxide extinguishing system or a steam extinguishing system, if available, should be used. For heavy oils, water spray can be used.

6. To extinguish a fire in the galley, carbon dioxide or powder fire extinguishers must be used.

7. If liquid fuel equipment burns, foam or spray water must be used.

Paints and packs

Storage and use of most paints, varnishes and enamels, except those that have water base, is associated with a high fire danger. Oils contained in oil paints, are not themselves flammable liquids. But these paints usually contain flammable solvents, the flash point of which can be as low as 32°C. All other components of many paints are also flammable. The same applies to enamels and oil varnishes.

Even after drying, most paints and varnishes continue to be flammable, although their flammability is significantly reduced when the solvents evaporate. The flammability of dry paint actually depends on the flammability of its base.

Flammability characteristics and combustion products.

Liquid paint burns very intensely, producing a large amount of thick black smoke. Burning paint can spread, so that fires associated with burning paints resemble burning oils. Due to the formation of dense smoke and the release of toxic fumes when extinguishing burning paint in indoors, breathing apparatus should be used.

Paint fires are often accompanied by explosions. Since paints are usually stored in tightly sealed cans or drums with a capacity of up to 150-190 liters, a fire in the area where they are stored can easily cause the drums to heat up, causing the containers to rupture. The paints contained in the drums ignite instantly in the presence of ignition sources and explode in the presence of oxygen in the air.

Extinguishing.

Because liquid paints contain solvents with low flash points, water is not always effective in extinguishing paint fires. To extinguish a fire associated with the burning of a large amount of paint, it is necessary to use foam. Water can be used to cool surrounding surfaces. When small amounts of paint or varnish catch fire, you can use foam, carbon dioxide or powder fire extinguishers. You can use water to extinguish dry paint.

1.3 Class "C" fires

Gases

Any gas that can burn at normal oxygen levels in the air (about 21%) should be considered a flammable gas. Flammable gases and vapors of flammable liquids are capable of burning only when their concentration in the air is within the flammability range, and the mixture (flammable gas + atmospheric oxygen) is heated to the ignition temperature.

In gases, molecules are not bound to each other, but are in free movement. As a result, the gaseous substance does not have its own shape, but takes the shape of the container in which it is enclosed.

Typically, flammable gases are stored and transported on ships in one of the following three states: compressed; liquefied; cryogenic

Compressed gas- this is a gas that, at normal temperature and pressure (+20°C; 740 mmHg) is completely in a gaseous state in a container under pressure

Liquefied gas is a gas that, at normal temperatures, is partly in a liquid and partly in a gaseous state in a container under pressure.

Cryogenic gas is a gas that is liquefied in a container at a temperature significantly below normal and at low and medium pressures.

Main hazards.

The hazards posed by gas in a container are different from those posed by gas escaping from the container. Let's look at each of them separately, although they can exist simultaneously.

Limited scope hazards. When gas is heated in a limited volume (cylinder, tank, tank, etc.), its pressure increases. If there is a large amount of heat, the pressure can increase so much that it will cause the container to rupture and leak gas. In addition, contact with fire may reduce the strength of the container material, which may also cause the container to rupture.

An explosion may occur if there is no safety devices or in case they don't work. The cause of an explosion can also be a rapid increase in pressure in the container when safety valve unable to reduce pressure at a rate that would prevent the build-up of pressure capable of causing an explosion. Tanks and cylinders can also explode when their strength is reduced as a result of flame contact with their surface. Sprinkling the surface of the container with water helps prevent rapid pressure growth, but does not guarantee the prevention of an explosion, especially if the flame also affects the walls of the container.

Capacity rupture. Ruptures of containers containing liquefied flammable gases due to fire are not uncommon. This type of destruction is called an explosion of expanding vapors of a boiling liquid. In this case, as a rule, it is destroyed top part containers where it comes into contact with gas.

Most explosions occur when the container is half to about three-quarters full of liquid. A small uninsulated container may explode within a few minutes, but a very large container, even if not cooled with water, may explode within a few hours. Uninsulated containers containing liquefied gas can be protected from explosion by spraying them with water. A film of water must be maintained on the top of the container where the vapor is located.

Hazards associated with gas escaping from a confined volume. These hazards depend on the properties of the gas and where they exit the container.

Toxic or poisonous gases are life-threatening. If they come out near a fire, they block access to the fire for people fighting the fire or force them to use breathing apparatus.

Oxygen and other oxidizing gases are not flammable, but they can cause flammable substances to ignite at temperatures below normal.

Contact of the gas with the skin causes frostbite, which can have serious consequences with prolonged exposure. Additionally, when exposed to low temperatures, many materials, such as carbon steel and plastics, become brittle and break down.

Flammable gases escaping from a container pose a risk of explosion, fire, or both. The escaping gas accumulates and mixes with air in limited space explodes. A gas will burn without exploding if the gas-air mixture accumulates in an amount insufficient to cause an explosion, or if it ignites very quickly, or if it is in an unconfined space and can disperse. If flammable gas leaks on an open deck, a fire may occur. But if a very large amount of gases leaks into the surrounding air, the ship's superstructure can limit its dispersion so much that an explosion occurs. This type of explosion is called an explosion outdoors. This is how liquefied non-cryogenic gases, hydrogen and ethylene, explode.

Extinguishing.

Fires involving the combustion of flammable gases can be extinguished using fire extinguishing powders or compact jets of water. For some types of gases, carbon dioxide and freons should be used. In case of fires caused by flammable gases, great danger For people fighting fire, it is a high temperature. In addition, there is a danger that gas will continue to escape after the fire has been extinguished, which could cause the fire to restart and cause an explosion. Powder and a stream of water create a reliable heat shield, while carbon dioxide and freons cannot create a barrier to thermal radiation generated during gas combustion.

It is recommended to allow the gas to burn until its flow can be stopped at the source. No attempt should be made to extinguish the fire unless this will stop the flow of gas. Until the flow of gas toward a fire cannot be stopped, firefighting efforts should be directed toward protecting surrounding combustible materials that may be ignited by the flames or heat generated during the fire. For these purposes, compact or spray jets of water are usually used. As soon as the flow of gas from the container stops, the flame should go out. But if the fire was extinguished before the end of the gas flow, care must be taken to prevent the escaping gas from igniting.

Fire associated with the combustion of liquefied flammable gases such as liquefied petroleum and natural gases, can be brought under control and extinguished by creating a dense layer of foam on the surface of the spread flammable substance.

1.4 Class "D" fires

Metals

It is generally accepted that metals do not ignite. But in some cases they can contribute to the intensification of the fire and fire danger. Sparks from cast iron and steel can ignite nearby flammable materials. Crushed metals can easily ignite at high temperatures. Some metals, especially when crushed, are prone to spontaneous combustion under certain conditions. Alkali metals such as sodium, potassium and lithium react violently with water to release hydrogen, producing heat sufficient to ignite the hydrogen. Most metals in powder form can ignite like a cloud of dust; a strong explosion is possible. In addition, metals can cause injury to people fighting a fire in the form of burns, injuries, and toxic fumes.

Many metals, such as cadmium, emit toxic fumes when exposed to high temperatures during a fire. When extinguishing any fires involving the burning of metals, you should always use breathing apparatus.

Characteristics of some metals.

It is a light silver-white metal, soft, fusible (density 0.862 g/cm 3, melting point 63.6°C). Potassium belongs to the group alkali metals. In air it quickly oxidizes: 4K + O 2 = 2 K 2 O. In contact with water, the reaction occurs violently, with an explosion: 2K + 2 H 2 O = 2 KOH + H 2. The reaction proceeds with the release of a significant amount of heat, which is sufficient to ignite the released hydrogen.

Aluminum.

It is a lightweight metal that conducts electricity well. In its normal form it poses no danger in the event of a fire. Its melting point is 660°C. This is a low enough temperature that in the event of a fire, destruction of unprotected structural elements made of aluminum can occur. Aluminum shavings and sawdust burn, and aluminum powder poses a risk of severe explosion. Aluminum cannot spontaneously ignite and is considered non-toxic.

Cast iron and steel.

These metals are not considered flammable. They do not burn in large products. But steel wool or powder can ignite, and powdered cast iron can explode when exposed to high temperature or flame. Cast iron melts at 1535°C, and ordinary structural steel at 1430°C.

It is a shiny white metal, soft, malleable, and capable of deformation when cold. It is used as a base in light alloys to give them strength and ductility. The melting point of magnesium is 650° C. Magnesium powder and flakes are highly flammable, but in the solid state it must be heated to a temperature above its melting point before it will ignite. It then burns very intensely, with a brilliant white flame. When heated, magnesium reacts violently with water and all types of moisture.

It is a strong white metal, lighter than steel. Melting point 2000°C. It is part of steel alloys, allowing them to be used at high operating temperatures. In small products it is highly flammable, and its powder is a strong explosive. However, large pieces pose little fire hazard.

Titanium is not considered toxic.

Extinguishing.

Extinguishing fires involving the combustion of most metals presents significant difficulties. Often these metals react violently with water, which leads to the spread of fire and even an explosion. If a small amount of metal is burning in a confined space, it is recommended to allow it to burn out completely. Surrounding surfaces should be protected using water or other suitable extinguishing agent.

Some synthetic liquids are used to extinguish metal fires, but as a rule, they are not available on board. Some success in fighting such fires can be achieved by using fire extinguishers with universal fire extinguishing powder. Such fire extinguishers are usually found on ships.

Sand, graphite, various powders and salts are used to extinguish metal fires with varying degrees of success. But none of the extinguishing methods can be considered completely effective for fires involving the combustion of any metal.

Water and fire extinguishing agents water-based materials such as foam should not be used to extinguish flammable metal fires. Water can cause a chemical reaction resulting in an explosion. Even chemical reaction does not occur, drops of water falling on the surface of the molten metal will decompose with an explosion and spray the molten metal. But, in some cases, water can be used carefully: for example, when large pieces of magnesium are burning, water can be applied to those areas that are not yet on fire to cool them and prevent the spread of the fire. Water should never be applied to the molten metals themselves, but rather to areas at risk of fire spread.

This is due to the fact that water falling on the molten metal dissociates, releasing hydrogen and oxygen 2H 2 O ® 2H 2 + O 2. Hydrogen in the fire zone burns explosively.

1.5 Class "E" fires

Electrical equipment

Electrical faults that may cause a fire.

1. Short circuit.

When the insulation that separates two conductors is damaged, short circuit, at which the current strength is high. Electrical overload and dangerous overheating occur in the network. This may cause a fire.

This is an electric shock air gap in the chain. Such a gap can be created intentionally (by turning on a switch) or accidentally (for example, when a contact on a terminal is loosened). In both cases, when an arc occurs, intense heating occurs and hot sparks and red-hot metal can be scattered, which, if they come into contact with flammable substances, causes a fire.

In addition, during the operation of ship electrical equipment there may be other causes of fire, such as contact resistance, overloads, as well as fires caused by violations of rules technical operation electrical installations and units: leaving electric heating devices turned on without supervision, contact of heated parts of electric drives with combustible objects (fabrics, paper, wood) and other reasons.

Hazards associated with electrical fires.

1. Electric shock.

An electric shock can occur as a result of contact with a live object. The lethal value of current flowing through a person is 100 mA (0.1A). People fighting a fire face two dangers: firstly, when moving in the dark or in smoke, they can touch a conductor who is under tension; secondly, the stream of water or foam can become a conductor of electrical current from energized equipment to the people supplying the water or foam. In addition, the danger and severity of electric shock increases when firefighting personnel stand in water.

During an electrical fire, a significant portion of the injuries are burns. Burns can result from direct contact with hot conductors or electrical equipment, the skin being exposed to sparks flying from them, or exposure to an electric arc.

3. Toxic fumes released when insulation burns.

Insulation electrical cables usually made of rubber or plastic. When burned, they produce toxic fumes, and polyvinyl chloride, also known as PVC, produces hydrogen chloride, which can have very serious effects on the lungs. It is also believed to contribute to the intensification of fires and increase the hazards associated with such fires.

Extinguishing.

If the fire has spread to any electrical equipment, the corresponding circuit must be de-energized. But regardless of whether the circuit is de-energized or not, when extinguishing a fire, only non-conductive substances should be used. electricity, such as fire extinguishing powder, carbon dioxide or freon. Persons responding to a Class E fire must always assume that the electrical circuit is energized. The use of water in any form is not permitted. In a room where electrical equipment is on fire, you should use breathing apparatus, since burning insulation releases toxic fumes.