A fire in a tank starts, in most cases, with an explosion of the vapor-air mixture located under its roof. As a result of the explosion, the roof of the tank is completely torn off or partially destroyed and the liquid is ignited on the entire free surface. The strength of the explosion, as a rule, is greater in those tanks where there is a large gas space filled with a mixture of oil vapor with air (low liquid level). Depending on the strength of the explosion in a vertical metal tank, the following situation can be observed: --- - - the roof is completely torn off, it is thrown to the side at a distance of 20-30 m; the liquid burns over the entire area of ​​the tank.

The roof rises somewhat, opens fully or partially, then plunges into the burning liquid.

The roof is deformed and forms small gaps in the places of attachment to the tank wall, as well as in the welds of the roof itself.

The situation on fire as a result of depressurization of the roof of the tank.

In case of fire in reinforced concrete buried (underground) tanks from

explosion, the destruction of the roof occurs, in which large holes are formed, then, during the fire, the coating may collapse.

Collapse of the roof of a reinforced concrete buried (underground) reservoir.

In cylindrical horizontal tanks, during an explosion, one of the end walls most often ruptures, which often leads to the failure of the tank from the foundation, its overturning and spillage of liquid.

Consequences of an explosion in a horizontal cylindrical tank.

When burning petroleum products over the entire area of ​​the tank mirror, the height of the luminous part of the flame is 1.5-2 of the diameter of the tank and is more than 40 m. In windy conditions, the flame tilts at an angle to the horizon, sometimes touching the ground surface, and has approximately the same dimensions.

The released thermal energy is transferred to the walls of the reservoir,

the top layer of the oil product into the environment and causes heating of adjacent tanks and communications. As a result of this, it is possible: the formation of explosive concentrations in neighboring tanks, which can lead to an explosion and its ignition; flare combustion of vapors of oil products at breathing valves or leaks in the roof of neighboring tanks; heating of communications, their deformation, leakage and burning of liquid from them

12. Stationary fire extinguishing systems with air-mechanical foam. In warehouses of oil and oil products, it is necessary to provide for fire extinguishing with air-mechanical foam of medium and low expansion. Installations are provided: stationary automatic fire extinguishing, stationary non-automatic fire extinguishing and mobile. Buildings and premises of the SNS to be equipped with stationary automatic fire extinguishing installations are shown in the table.

Warehouse buildings	Premises to be equipped with automatic fire extinguishing installations
1. Buildings of product pumping stations (except for tank farms of main oil pipelines), sewerage pumping stations for pumping untreated industrial wastewater (with oil and oil products) and captured oil and oil products.	Premises for pumps and valve assemblies with a floor area of ​​300 m2 or more.
2. Buildings of pumping stations of tank farms of main oil pipelines.	Rooms for pumps and valve assemblies at stations with a capacity of 1200 m3/h and more.
3. Warehouse buildings for the storage of petroleum products in containers.	Warehouses with an area of ​​500 m2 or more for petroleum products with a flash point of 120 ° C and below, an area of ​​750 m2 or more - for other petroleum products.
4. Other warehouse buildings (bottling, packaging, etc.)	Industrial premises with an area of ​​more than 500 m2, in which there are oil and oil products in an amount of more than 15 kg/m2.

A stationary automatic fire extinguishing installation consists of a pumping station, tanks for water, a foam concentrate or its solution, foam generators installed on tanks and in buildings, pipelines for supplying a foam concentrate solution (solution pipelines) to foam generators and automation equipment.

A stationary non-automatic fire extinguishing installation consists of the same elements as a stationary automatic one, with the exception of permanently installed foam generators and automation equipment; on the mortar pipelines, fire hydrants or risers with connecting heads are provided for connecting fire hoses and foam generators for a fire.

13. AUTOMATION OF FIRE EXTINGUISHING SYSTEMS WITH AIR-MECHANICAL FOAM

The composition of the automatic fire extinguishing system a fire pumping station is included, the automation of which should provide: automatic start-up of a working pump;

automatic start of the reserve pump in case of failure of the working pump within the set time;

automatic switching on of shut-off valves with electric drive; automatic switching of control circuits from a working to a backup power supply with electrical energy (in the event of a power failure at the working input);

automatic start-up of the working dosing pump;

automatic start-up of the standby dosing pump in case of failure of the working pump within the set time;

formation of a command impulse for automatic shutdown of ventilation of technological equipment;

formation of a command impulse for automatic shutdown of energy receivers of the 3rd and 2nd category.

In the premises of the pumping station, a light and sound alarm should be provided:

on the presence of voltage at the main and backup inputs of power supply and grounding of phases to earth (on call);

on disabling the automatic start of pumps and the dosing pump; about the emergency level in the water reservoir and in the drainage pit.

At the same time, signals are sent to the room fire station or other premises with round-the-clock stay of duty personnel:

about the occurrence of a fire; about starting pumps;

on the start of work of sprinkler and deluge installations, indicating the direction in which water is supplied (foaming agent solution);

about turning off the sound alarm about a fire;

about a malfunction of the installation (disappearance of voltage at the main power supply input);

about the pressure drop in the hydropneumatic tank or in the impulse device;

about the emergency water level in the reservoir and drainage pit;

on the position of the valves;

Continuation 13 AUTOMATION OF FIRE EXTINGUISHING SYSTEMS WITH AIR-MECHANICAL FOAM

about damage to the control lines of the shut-off devices installed on the incentive pipelines of the control units of deluge plants and metering pumps.

Sound signals about a fire differ in tone (howlers, sirens) from sound signals about a malfunction (call).

Auto power on The system is duplicated by remote activation from the control panel of the system control station, as well as from the place of a possible fire.

The principle of operation of the fire column KPA is based on opening and closing the valve of a fire hydrant in order to supply water from the water supply. The KPA column is installed on the fire hydrant in such a way that the square key at the bottom of the column enters the square end end of the hydrant rod. The fire column is screwed onto the hydrant by rotating its body clockwise (the socket wrench does not turn). After that, the hydrant valve opens (with the column valves closed), by turning the socket wrench counterclockwise (the hydrant valve opens fully at 10-14 turns of the socket wrench) and water from the water supply network enters the cavity of the fire column. After the hoses are connected to the branch pipes of the fire column, the valves open and water from the fire column enters the hose line.

14. Fire detectors

Fire detectors are classified according to the activation parameter and the physical principle of detection. The following activation parameters are used for fire detection:

The concentration of smoke particles in the air;

Ambient temperature;

Open flame radiation.

There are five main types of fire detectors:

thermal fire detectors

smoke detectors

flame detectors

manual fire detectors

combined fire detectors

Thermal fire detectors respond to changes in ambient temperature. They are installed in the following cases:

When, in a controlled volume, the structure of the materials used is such that, when burned, it gives off more heat than smoke.

When the spread of smoke is difficult due to either close quarters [e.g. behind false ceilings] or external conditions [low temperature, high humidity, etc.]

When there is a high concentration of any aerosol particles in the air that are not related to combustion processes [for example, soot from working machines in a garage or flour in flour mills]

The simplest maximum thermal fire detectors consist of a soldered contact of two conductors. Typically, the maximum temperature set in them is 75 ° C.

More complex maximum thermal fire detectors are equipped with a temperature-sensitive semiconductor element

In all these cases, it is necessary to use thermal linear fire detectors.

An open flame contains characteristic radiation in both the ultraviolet and infrared parts of the spectrum. Accordingly, there are two types of these devices: ultraviolet and infrared flame detectors.

The infrared flame detector uses an IR sensing element and an optical focusing system to register characteristic

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Burning liquids.

All combustible liquids are capable of evaporation, and their combustion occurs only in the vapor phase located above the surface of the liquid. The amount of vapor depends on the composition and temperature of the liquid. Combustion of vapors in air is possible only at a certain concentration.

The lowest temperature of a liquid at which the concentration of its vapors in a mixture with air ensures the ignition of the mixture from an open source of ignition without subsequent stable combustion is called the flash point. At the flash point, stable combustion does not occur, since at this temperature the concentration of the liquid vapor mixture with air is not stable, which is necessary for such combustion. The amount of heat released during the flash is not enough to continue burning, and the substance is not yet heated enough. In order to ignite a liquid, not a short-term, but a long-acting ignition source is needed, the temperature of which would be higher than the auto-ignition temperature of the mixture of vapors of this liquid with air.

In accordance with GOST 12.1.004-76, a combustible liquid (FL) is understood as a liquid capable of burning independently after the ignition source is removed and having a flash point above +61 ° C (in a closed crucible) or + 66 ° C (in an open crucible).

A flammable liquid (flammable liquid) is a liquid that can burn independently after the ignition source is removed and has a flash point not higher than +61 ° C (in a closed crucible) or + 66 ° C (in an open crucible).

The flash point is the lowest temperature at which a liquid becomes especially dangerous in terms of fire, therefore its value is taken as the basis for classifying flammable liquids according to their degree of fire hazard. The fire and explosion hazard of liquids can also be characterized by the temperature limits of ignition of its vapors.

The temperature of a liquid at which the concentration of saturated vapors in air in an enclosed space is capable of igniting when exposed to an ignition source is called the lower temperature ignition limit. The temperature of a liquid at which the concentration of saturated vapors in air in an enclosed space can still ignite when exposed to an ignition source is called the upper temperature ignition limit.

The temperature limits of ignition of some liquids are given in table. 29.

Table 29 Temperature limits of ignition of some liquids: acetone, gasoline A-76, benzene, tractor kerosene, ethyl alcohol.

Temperature limits show in what temperature range liquid vapors will form combustible mixtures with air.

Extinguishing fires of flammable and combustible liquids is based on the analysis of all options for their development. Fires that occur in tanks are longer, therefore they require a large amount of funds and forces to eliminate.

Storage tanks for flammable liquids and combustible liquids

For the purpose of storing flammable liquids and combustible liquids, containers made of metal, reinforced concrete, ice ground and synthetic material are used. The most popular are tanks made of steel. They are classified by design and capacity into:

• vertical in the form of a cylinder, having a conical or spherical roof, with a volume of 20 thousand cubic meters for storing flammable liquids and 50 thousand cubic meters for storing gaseous liquids;
• vertical in the form of a cylinder, with a stationary roof and a floating pontoon, with a volume of 50 thousand cubic meters;
• vertical in the form of a cylinder, with a floating roof, with a volume of 120 thousand cubic meters.

The process of developing a fire in a tank

Extinguishing fires in tank farms for storing flammable liquids and combustible liquids depends on the complexity of the ignition development process. Combustion begins due to the explosion of the gas-air mixture in the presence of an ignition source. The formation of a gassed environment occurs due to the properties of the GZh and flammable liquids, as well as operating modes and climatic conditions around the tank. Exploding, the gas-air mixture rushes up at high speed, often tearing off the roof of the container, after which ignition begins over the entire surface of the stored combustible liquid.

The further fate of the flame will depend on the area where it began, its dimensions, the fire resistance of the tank design, weather conditions, the actions of workers and fire protection systems.

When storing GZH and HFL, for example, in reinforced concrete tanks, a part of it is destroyed during an explosion, and combustion begins precisely in this area, which over the next 30 minutes leads to the complete destruction of the container and the spread of fire. The remaining types of containers, in the absence of cooling from the outside, are deformed within 15 minutes, provoking a spill of flammable liquids and the spread of fire.

Foam fire fighting

Extinguishing flammable and combustible liquids with low and medium expansion foam is the most popular way to fight a flame. The advantage of foam is that it isolates the surface of the combustible liquid from the flame, which leads to a decrease in its evaporation and, accordingly, the volume of combustible gases in the air. In this case, a solution of a foaming agent with cooling properties is formed. Thus, convective heat and mass transfer is achieved, and the temperature level becomes the same throughout the entire depth of the container in 15 minutes from the start of foam application.

Foam extinguishing

Extinguishing flammable liquids with a foam solution of various ratios depends on where the combustion occurs:

• low expansion rate for the lower part of the container, used for the “underlayer” method of extinguishing, the composition of the fire extinguishing agent contains a fluorine-containing film-forming foaming agent, due to which, when the foam rises through the layer of combustible content, it is not saturated with hydrocarbon vapors, retains fire extinguishing abilities; obtained with the help of trunks of low-expansion foam;
• average expansion rate for surface extinguishing, the foam is also inert, does not interact with flammable liquid vapors, cools the liquid, and helps to reduce the formation of an explosive air mixture; obtained with the help of specialized foam generators of the type of GPS.

After the extinguishing of the flammable liquid and the combustible liquid is completed, a thick foam layer forms on the surface of the liquid, protecting it from the resumption of combustion.

When applying fire extinguishing foam, the flame center should observe an intensity of 0.15 l / s.

Foam fire extinguishing is allowed by three methods:

• delivery of the foaming agent using a foam lifter and other similar equipment;
• delivery of foam to the surface of burning flammable liquids and combustible liquids using monitors;
• delivery of foam by subsurface quenching.

Water fire extinguishing

If it is not possible to organize the extinguishing of fires of flammable liquids with the help of foam, it is allowed to use sprayed water, which helps to cool the combustible contents to a temperature at which it cannot flare up.

In this case, the rate of supply of the aqueous solution must be at least 0.2 l/s.

Powder extinguishing

Extinguishing fires in flammable liquid storage tank farms with the help of a powder is suitable for those situations where burning occurs in the area of ​​\u200b\u200bgate valves, flange connections or gaps between the roof and the tank wall. The feed rate must exceed 0.3 kg/s. The powder is not able to cool the liquid, therefore, repeated extinguishing of the flammable liquid may be required.

Powder extinguishing - only for small fires and quick extinguishing

To avoid such situations, powder fire extinguishing is combined with foam in the following ways:

• maximum extinguishing of the flame with a foam solution, after which individual flame centers are localized with the help of a powder;
• elimination of the flame with the help of a powder component, followed by the supply of a foaming agent to cool the damaged surface and prevent the resumption of combustion.

In this case, it is forbidden to reduce the volume of fire extinguishing agents supplied.

Tank fire fighting plan

It is advisable to start extinguishing flammable and combustible liquids in tanks with an assessment of the current situation, as well as with the calculation of the required means and forces. In the event of such an emergency, a voluntary fire brigade should be organized, the head of which will be the person responsible for managing the process of eliminating the flame and distributing tasks among the fire extinguishing participants.

The responsible person must determine the volume of the territory on which extinguishing work will be carried out, organize the removal of unauthorized persons to the danger zone.

Upon arrival at the fire site, the leader conducts reconnaissance and indicates to other fire extinguishing participants the areas where maximum forces should be thrown.

Throughout the work, the tasks of the manager also include providing all available forces and means of cooling flammable liquids and combustible liquids in tanks, as well as choosing the optimal method of fighting fire.

When the main forces are thrown to work with a burning tank, it is important to protect neighboring tanks in case the damaged one collapses, or the resulting gas-air mixture explodes. It is for this purpose that all fire engines are installed at a safe distance, and hose lines are laid to the place of work.

Extinguishing of tank farms of flammable liquids and combustible liquids directly depends on the duration of burning, the nature of the resulting destruction of the tanks, the volume of liquids stored in the damaged and neighboring tanks, the likelihood of an explosion and a subsequent accidental spill of the contents.

When designing and building tank farms, a sewerage system should be provided into which water can be drained into the fire extinguishing process, and devices are also designed for emergency pumping of the contents into a safe tank.

How tanks are cooled during fire fighting

Extinguishing fires of flammable liquids and combustible liquids in tanks must necessarily be accompanied by cooling the contents of the damaged container. The latter needs to be cooled along the entire length of its circumference. In relation to neighboring tanks, there is also a requirement for mandatory cooling, but only along the entire length of the semicircle of the tank on the side that faces the combustion zone. In some cases, it is allowed not to carry out the procedure for cooling adjacent containers if there is no threat of flame transfer. The water supply for cooling purposes must be at least 1.2 l/s.

To extinguish tanks with gaseous liquids and flammable liquids with a volume of 5 thousand cubic meters, it is recommended to use fire monitors, which not only provide the required water output, but also have a mode of irrigation of a burning object.

The sequence of work with neighboring undamaged tanks is such that those located on the leeward side of the fire are the first to be protected and cooled.

The duration of work is determined until the flame is completely eliminated, and the temperature level inside the tank is not normal.

Hazardous zones during fire in tank farms

Extinguishing fires of flammable liquids and combustible liquids should also be carried out taking into account hazardous factors and zones that can reduce the effectiveness of fire extinguishing measures:

1. Formation of zones where it is impossible to deliver fire extinguishing agent.
2. Warming up the combustible contents of the tank to a depth of 1 m or more.
3. Decreased air temperature around the fire site.
4. Ignition of several containers at the same time.

Extinguishing a real fire of spilling flammable liquids in a large area Angarsk 2014:

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Class "B" fires are the burning 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 they burn. 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 the vapors above it can flare up 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 affected by the ignition temperature, flammability range, evaporation rate, chemical activity under the influence of heat, vapor density and diffusion rate.

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

Class B fires

Class B fires can result from the following materials:

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

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

Paints burn well, emitting large amounts of thick black smoke and toxic gases. When paints or varnishes ignite, 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 blue transparent 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.

In the process of burning petroleum products, oils and fats, a poisonous 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 ingress of liquid into the fire.

Surrounding objects and containers with burning liquids should be cooled with water. Class B fires can be extinguished in a number of ways:

• a small fire can be handled with a foam or powder fire extinguisher or a spray jet of water;
• in case of large spreading of flammable liquid, it is better to use powder fire extinguishers in conjunction with fire hoses for foam supply;
• if the liquid burns on the surface of the water, then first it is necessary to 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 water spray or foam.

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

Class B fires

• Materials that, when ignited, can lead to class B fires, are divided into three groups:
• flammable and combustible liquids,
• paints and varnishes,
• flammable gases.
• Let's consider each group separately.

Flammable and combustible liquids

Flammable liquids are liquids with a flash point of up to 60 ° C and below. Flammable liquids are liquids whose flash point exceeds 60°C. Flammable liquids include acids, vegetable oils and lubricating oils with a flash point exceeding 60°C.

Flammability characteristics:

When mixed with air and ignited, it is not the flammable and combustible liquids themselves that burn and explode, but their vapors. Upon contact with air, the evaporation of these liquids begins, the rate of which increases when the liquids 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 their exposure to air is as minimal as possible.

Explosions of flammable vapors most often occur in a confined space such as a container, tank. The strength 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.

The flash point is the generally accepted and most important, but not the only, factor in determining the hazard posed by a flammable or combustible liquid. The degree of danger of a liquid is also determined by the ignition temperature, flammability range, evaporation rate, chemical activity when contaminated or under the influence of heat, vapor density and diffusion rate. However, when a flammable or combustible liquid is burned for a short period of time, these factors have little effect on the combustibility characteristics.

The rates of combustion and flame propagation of various flammable liquids differ somewhat from each other. The burnout rate of gasoline is 15.2 - 30.5 cm, 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 and combustible liquids, in addition to the usual combustion products, some specific combustion products characteristic of these particular liquids are formed. Liquid hydrocarbons usually burn with an orange flame and give off thick clouds of black smoke. Alcohols burn with a clear blue flame, emitting a small amount of smoke. The combustion of some terpenes and esters is accompanied by vigorous boiling on the surface of the liquid, and their extinguishing presents considerable difficulty. The combustion of petroleum products, fats, oils and many other substances produces acrolein, a highly irritating toxic gas.

Flammable and combustible liquids of all types are transported by tankers as bulk cargo, as well as in portable containers, including their placement in containers.

Each ship has a large amount of flammable liquids in the form of fuel oil and diesel fuel, which are used to propel the ship and generate electricity. Fuel oil and diesel fuel become especially dangerous if they are heated before being fed to the nozzles. If there are cracks in the pipelines, these liquids flow out and are exposed to sources of ignition. Significant spreading of these liquids leads to a very strong fire.

Other places where flammable liquids are present include galleys, various workshops and areas where lubricating oils are used or stored. In the engine room, fuel oil and diesel fuel in the form of residues and films can be on and under the equipment.

Extinguishing

In the event of a fire, quickly shut off the source of flammable or combustible liquid. This will stop the flow of combustible substance to the fire, and people involved in the fight against fire will be able to use one of the following methods of extinguishing the fire. For this purpose, a layer of foam is used to cover the burning liquid and prevent the flow of oxygen to the fire. In addition, steam or carbon dioxide can be supplied to areas where combustion occurs. By turning off the ventilation, the supply of oxygen to the fire can be reduced.

Cooling. Fire-affected containers and areas should be cooled with a spray or compact jet of water from the fire main.

Flame retardation . To do this, fire extinguishing powder must be applied to the burning surface.

Due to the fact that there are no identical fires, it is difficult to establish a single method for extinguishing them. However, when extinguishing fires associated with the combustion of flammable liquids, it is necessary to be guided by the following.

1. With a small spread of the burning liquid, use powder or foam fire extinguishers or a sprayed jet of water.

2. With a significant spread of the burning liquid, powder fire extinguishers should be used with the support of fire hoses to supply foam or a spray jet. Protection of equipment exposed to fire should be carried out with a jet of water

3. When spreading a burning liquid over the surface of the water, it is necessary first of all to limit the spreading. If this succeeds, you need to create a layer of foam covering the fire. In addition, you can use a high-volume atomized water jet.

4. Foam, powder, high speed or low speed water spray applied horizontally across the opening should be used to prevent combustion products from escaping from inspection and measurement hatches until it can be closed.

5. To fight fires in cargo tanks, a deck-mounted foam extinguishing system and (or) a carbon dioxide extinguishing system or a vapor extinguishing system, if any, should be used. For heavy oils, water mist can be used.

6. To extinguish a fire in the galley, use carbon dioxide or powder fire extinguishers.

7. If liquid fueled equipment is on fire, foam or water spray should be used.

Paints and varnishes

The storage and use of most paints, varnishes and enamels, other than those that are water-based, is associated with a high fire hazard. The oils contained in oil paints are not themselves flammable liquids (linseed oil, for example, has a flash point of over 204°C). But 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 combustible. The same applies to enamels and oil varnishes.

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

Flammability characteristics and combustion products

Liquid paint burns very intensely, with a lot of thick black smoke. Burning paint can spread, so that the fire associated with the burning of paints resembles the burning of oils. Due to the formation of dense smoke and the release of toxic fumes, breathing apparatus should be used when extinguishing burning paint in an enclosed space.

Paint fires are often accompanied by explosions. Since paints are usually stored in tightly closed cans or drums with a capacity of up to 150 - 190 liters, a fire in the storage area can easily cause the drums to heat up, causing these containers to burst. The paints contained in the drums instantly ignite and explode when exposed to air.

Normal location on board

Paints, varnishes and enamels are stored in the paint rooms located in the bow or stern of the vessel under the main deck. Painting rooms should be made of steel or fully sheathed with metal. These spaces may be served by a fixed carbon dioxide extinguishing system or other approved system.

Extinguishing

Since liquid paints contain solvents with a low flash point, water is unsuitable for extinguishing burning paints. 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. If small amounts of paint or varnish ignite, carbon dioxide or powder fire extinguishers can be used. You can use water to extinguish dry paint.

flammable gases. In gases, the molecules are not bound to each other, but are in free motion. As a result, the gaseous substance does not have its own form, but takes the form of the container in which it is enclosed. Most solids and liquids, if the temperature rises sufficiently, can be turned into a gas. This term "gas" means the gaseous state of a substance under conditions of so-called normal temperatures (21°C) and pressure (101.4 kPa).

Any gas that burns at normal oxygen levels in the air; called flammable gas. Like other gases and vapours, flammable gases only burn when their concentration in air is within the flammability range and the mixture is heated to ignition temperature. As a rule, flammable gases are stored and transported on ships in one of the following three states: compressed, liquefied and cryogenic. Compressed gas is a gas that is completely in a gaseous state in a pressurized container at normal temperature. Liquefied gas is a gas that, at normal temperatures, is partly liquid and partly gaseous in a pressurized container. Cryogenic gas is a gas that is liquefied in a container at a temperature well below normal at low and medium pressures.

Main dangers

The dangers presented by the gas in the container are different from those that arise when it leaves the container. Let's consider each of them separately, although they can exist simultaneously.

Dangers of limited scope. When a gas is heated in a limited volume, its pressure increases. In the presence of a large amount of heat, the pressure may increase so much that it will cause a gas leak or a container rupture. In addition, in contact with fire, a decrease in the strength of the material of the container may occur, which also contributes to its rupture.

To prevent explosions of compressed gases, safety valves and fusible links are installed on tanks and cylinders. As the gas expands in the container, it causes the safety valve to open, which reduces the internal pressure. The spring-loaded device will close the valve again when the pressure drops to a safe level. A meltable metal insert can also be used, which will melt at a certain temperature. The insert plugs the hole, usually located in the upper part of the container body. The heat generated by the fire threatens the container containing the pressurized gas, causes the insert to melt, and allows the gas to escape through the orifice, thereby preventing it from building up pressure that leads to an explosion. But since such an opening cannot be closed, the gas will escape until the container is empty.

An explosion can occur if safety devices are not present or if they do not work. An explosion can also be caused by a rapid build-up of pressure in the vessel when the pressure relief valve is unable to reduce the pressure at a rate that would prevent the build-up of pressure capable of causing an explosion. Tanks and cylinders may also explode if their strength is reduced by the contact of the flame with their surface. The impact of the flame on the walls of the container, which are above the liquid level, is more dangerous than contact with the surface that is in contact with the liquid. In the first case, the heat radiated by the flame is absorbed by the metal itself. In the second case, most of the heat is absorbed by the liquid, but this also creates a dangerous situation, since the absorption of heat by the liquid can cause a dangerous, although not so rapid increase in pressure. Irrigation of the surface of the container with water prevents a rapid increase in pressure, but does not guarantee the prevention of an explosion, especially if the flame also affects the walls of the container.

Capacity rupture. Compressed or liquefied gas has a large amount of energy contained in the container in which it is located. When the capacitance breaks, this energy is usually released very quickly and violently. The gas escapes, and the container or its elements scatter.

Explosions of containers containing liquefied flammable gases under the influence of fires are not uncommon. This type of destruction is called an explosion of expanding vapors of a boiling liquid. In this case, as a rule, the upper part of the container is destroyed, in the place where it comes into contact with the gas. The metal is stretched, thinned and torn along the length.

The strength of the explosion depends mainly on the amount of evaporating liquid during the destruction of the container and the mass of its elements. Most explosions occur when the container is filled with liquid from 1/2 to about 3/4 of its height. A small uninsulated container may explode in a few minutes, and a very large container, even if it is not cooled by water, only after a few hours. Uninsulated containers containing liquefied gas can be protected from explosion by supplying water to them. A film of water must be maintained at the top of the vessel where the vapors are.

Hazards associated with the release of gas from a limited volume. These hazards depend on the properties of the gas and where it leaves the container. All gases, except oxygen and air, are dangerous if they displace the air required for breathing. This is especially true for odorless and colorless gases such as nitrogen and helium, since there is no sign of their occurrence.

Toxic or poisonous gases are life threatening. If they go outside near a fire, they block access to the fire for people who are fighting it, or force them to use breathing apparatus.

Oxygen and other oxidizing gases are non-flammable, but they can ignite combustibles at temperatures below normal.

Contact with the gas on the skin causes frostbite, which can be serious if exposed for a long time. In addition, when exposed to low temperatures, many materials such as carbon steel and plastics become brittle and break.

Flammable gases escaping from a container present a risk of explosion and fire, or both. The escaping gas, when accumulated and mixed with air in a confined space, explodes. The gas will burn without exploding if there is not enough gas-air mixture to explode, or if it ignites very quickly, or if it is in an unlimited space and can be dispersed. Thus, when a flammable gas escapes onto the open deck, a fire usually starts. But when a very large amount of gas escapes, the surrounding air or the ship's superstructure can restrict its dispersion so much that an explosion occurs, called an open air explosion. This is how liquefied non-cryogenic gases, hydrogen and ethylene explode.

Properties of some gases.

The following are the most important properties of some flammable gases. These properties explain the varying degrees of the dangers that arise in the case of accumulation of gases in a limited volume or when they spread.

Acetylene. This gas is transported and stored, as a rule, in cylinders. For safety reasons, a porous filler is placed inside the acetylene cylinders - usually diatomaceous earth, which has very small pores or cells. In addition, the aggregate is impregnated with acetone, a flammable material that readily dissolves acetylene. Thus, acetylene cylinders contain much less gas than it seems. Several fusible links are installed in the upper and lower parts of the cylinders, through which the gas escapes into the atmosphere in case the temperature or pressure in the cylinder rises to a dangerous level.

The release of acetylene from the cylinder may be accompanied by an explosion or fire. Acetylene ignites more easily than most flammable gases and burns more quickly. This contributes to the amplification of explosions and makes it difficult for ventilation to prevent an explosion. Acetylene is only slightly lighter than air, so it mixes easily with air as it exits the bottle.

Anhydrous ammonia. Consists of nitrogen and hydrogen and is used mainly for the production of fertilizers, as a refrigerant and a source of hydrogen necessary for the heat treatment of metals. It is a rather toxic gas, but its inherent pungent odor and irritant effect are good warning signs of its presence. Strong leaks of this gas caused the rapid death of many people before they could leave the area of ​​​​its appearance.

Anhydrous ammonia is transported in trucks, railway tank wagons and barges. It is stored in cylinders, tanks and in a cryogenic state in insulated containers. Explosions of expanding vapors of boiling liquid in uninsulated cylinders containing anhydrous ammonia are rare, due to the limited flammability of the gas. If such explosions do occur, they are usually associated with fires of other combustible substances.

Anhydrous ammonia can explode and burn when exiting a cylinder, but its high lower explosive limit and low calorific value greatly reduce this hazard. The release of large quantities of gas when used in refrigeration systems, as well as storage at unusually high pressures, can lead to an explosion.

Ethylene. It is a gas composed of carbon and hydrogen. It is usually used in the chemical industry, for example, in the manufacture of polyethylene; in smaller quantities it is used for fruit ripening. Ethylene has a wide flammability range and burns quickly. Being non-toxic, it is an anesthetic and asphyxiant.

Ethylene is transported in a compressed form in cylinders and in a cryogenic state in thermally insulated trucks and railway tank cars. Most ethylene cylinders are protected from overpressure by burst discs. Ethylene cylinders used in medicine may have fusible links or combined safety devices. Safety valves are used to protect tanks. Cylinders can be destroyed by fire, but not by expanding vapors of boiling liquid, since there is no liquid in them.

Explosion and fire are possible if ethylene is released from the cylinder. This is facilitated by the wide flammability range and high burning rate of ethylene. In a number of cases, associated with the release of a large amount of gas into the atmosphere, explosions occur.

Liquefied natural gas. It is a mixture of substances consisting of carbon and hydrogen, the main component of which is methane. In addition, it contains ethane, propane and butane. Liquefied natural gas used as fuel is non-toxic, but it is an asphyxiant.

Liquefied natural gas is transported in a cryogenic state on gas carrier ships. Stored in insulated containers protected from overpressure by safety valves.

The release of liquefied natural gas from a cylinder into an enclosed space may be accompanied by an explosion and fire. Test data and experience show that liquefied natural gas explosions do not occur in the open.

LPG

This gas is a mixture of substances consisting of carbon and hydrogen. Industrial LPG is usually propane or normal butane, or a mixture of both, with small amounts of other gases. It is non-toxic, but is an asphyxiant. It is mainly used as bottled fuel for domestic use.

Liquefied petroleum gas is transported as liquefied gas in uninsulated cylinders and tanks on trucks, railway tank cars and gas carrier ships. In addition, it can be transported by sea in a cryogenic state in thermally insulated containers. It is stored in cylinders and heat-insulated tanks. Relief valves are commonly used to protect LPG tanks from overpressure. Some cylinders install fusible links, and sometimes safety valves and fusible links together. Most of the containers can be destroyed by explosions of expanding vapors of a boiling liquid.

The release of liquefied petroleum gas from the tank may be accompanied by an explosion and fire. Because this gas is used primarily indoors, explosions are more common than fires. The danger of an explosion is increased due to the fact that 75 - 84 m 3 of gas is obtained from 3.8 liters of liquid propane or butane. If a large amount of liquefied petroleum gas is released into the atmosphere, an explosion may occur.

Normal location on board

Liquefied flammable gases, such as liquefied petroleum and natural gases, are transported in bulk on tankers. On cargo ships, flammable gas cylinders are transported on deck only.

Extinguishing

Fires associated with the ignition of flammable gases can be extinguished with fire extinguishing powders. For some types of gases, carbon dioxide and freons should be used. In fires caused by the ignition of flammable gases, a great danger to people fighting the fire is the high temperature, as well as the fact that the gas will continue to escape after the fire is extinguished, and this can cause a fire to resume and an explosion. The powder and the sprayed jet of water create a reliable thermal screen, while carbon dioxide and freons cannot create a barrier to thermal radiation generated during gas combustion.

It is recommended that the gas be allowed to burn until its flow cannot be shut off at the source. No attempt should be made to extinguish the fire unless this will stop the flow of gas. As long as the flow of gas to the fire cannot be stopped, the efforts of firefighters should be focused on protecting the surrounding combustible materials from: being ignited by the flame or the high temperature generated during the fire. For this purpose, compact or sprayed jets of water are usually used. As soon as the flow of gas from the tank stops, the flame should go out. But if the fire was extinguished before the end of the outflow of gas, it is necessary to monitor the prevention of ignition of the outgoing gas.

A fire associated with the combustion of liquefied flammable gases, such as liquefied petroleum and natural gases, can be controlled and extinguished by creating a dense layer of foam on the surface of the spilled combustible substance.