RU2129031C1 - Method of extinguishing the fire on surface of combustible liquid and device for its embodiment - Google Patents

Abstract

FIELD: methods and devices for extinguishing fires of storage tanks with highly inflammable and combustible liquids; applicable also in extinguishing fires of oil wells and in systems of automatic fire extinguishing. SUBSTANCE: as distinguished from the known methods of extinguishing of fires of highly inflammable and combustible liquids with fire extinguishing compounds, used in the claimed method is solid-fuel aerosol-forming substance in form of foam-pellets or foam-charges whose density does not exceed 800 kg/cu. m and their surface is coated with waterproofing compound that allows extinguishing of fire of highly inflammable and combustible liquids in boundary layer of aerosol formed above surface of firing liquid. The device for embodiment of the claimed method has sealed container body with fire-extinguishing substance and automatic lock. Said container is installed on manhole of storage tank with highly inflammable and combustible liquids. EFFECT: higher fire safety of storage tanks with highly inflammable and combustible liquids, high adaptability of device for manufacture, increased efficiency of fire extinguishing with use of insignificant means and efforts for fire extinguishing. 3 cl, 3 dwg

Description

 The invention relates to fire extinguishing, in particular to extinguishing combustible liquids in tanks - ground and underground in cars and railway tanks, river and sea tanks, and can also be used to extinguish oil wells in manual and automatic start-up installations, sprinkler and deluge systems water and powder fire extinguishing.

 There is a method of extinguishing burning liquids, which consists in supplying solid carbon dioxide in fragmented form to the fire, with a diameter of granules of 3-4 cm. The granules are fed under a layer of burning liquid in compact portions (1) - prototype.

 This method is described in the copyright certificate A 62 C 3/06, N 1687266 from 10.30.91, Bull. N 40.

 The disadvantages of the method of extinguishing burning liquids with solid carbon dioxide are that this method can successfully extinguish fires in open tanks and extinguishing becomes problematic in closed tanks or tanks with a settled roof.

 In addition, it will be very difficult to supply solid carbon dioxide to the burning tank through the discharge and loading process pipelines, as the rate of loss of mass of “dry ice” in water increases 600 times, compared with the loss of mass in air, and the storage of solid carbon dioxide in fire extinguishing warehouses will be very expensive for a protected enterprise.

 Also known is a powder-gas fire extinguisher designed to extinguish fires locally, containing a cannon-gun with fire-extinguishing powder, a gas-generating chamber with an explosive charge and a squib, an automatic control and monitoring system.

One of the features of a fire extinguisher is that experiments have shown that fire extinguishing powder heated by a flame in the gun’s mouth to a temperature of (100-120 ^o C) and introduced into the fire zone instantly eliminates combustion due to the inhibitory properties of the decomposition products of fire extinguishing powder and phlegmatization inert gas combustion zones. This increases the fire extinguishing efficiency of the heated powder by 3-5 times, compared with conventional cold powder.

 This fire extinguisher is described in the Recommendations of VNIIPO Ministry of Internal Affairs of the Russian Federation of the USSR, 1978, p. 12, 16, 30 fig. 5 and 4 (2).

The disadvantages of this fire extinguisher include the following:
1. The increased specific weight of the body of the fire extinguisher in relation to the weight of its fire extinguisher charge.

2. High pressure (100 MPa) and high temperature (1500-2000 ^o C in the gas generating chamber.

 3. High created pressure (10 MPa) in the body of the fire extinguisher.

 4. The complexity of using a fire extinguisher in technological installations due to the high expiration rate (up to 250 m / s) of the fire extinguishing composition and its increased danger to staff.

 Known installation of aerosol fire extinguishing, designed for volume extinguishing fires of flammable and combustible liquids (alcohols, gasoline, benzene, cyclohexane, ethers, etc.), containing a housing, inside which is placed a fire extinguishing aerosol forming substance and initiating means.

 One of the features of aerosol fire extinguishing installations (generators) is that in installations, a solid fuel aerosol forming substance is used as a fire extinguishing agent, where the aerosol contains a solid aerosol of alkali and alkaline earth metal salts and transition group metals formed during the combustion of condensed charges. In this case, the aerosol is able to remain in suspension in the fire zone for 20-50 minutes and inhibit chemical reactions in the fire flame, due to the death of radicals on the surface of the aerosol solid particles.

 This installation is described (3) in the Recommendations of VNIIPO Ministry of Internal Affairs and Moscow, 1992, p. 19, Fig. 1 and adopted as the closest analogue to the method of extinguishing a fire.

As the closest analogue to the claimed device for supplying a fire extinguishing medium to a burning surface of the liquid, the device according to the application of Great Britain N 1342820, cl. A 62 C 3/12, publ. 01/03/74
The disadvantages of volumetric aerosol fire extinguishing installations include the following:
1. Aerosol fire extinguishing installations are designed to extinguish fires in buildings and they are not focused on the protection of tanks with combustible liquids from fires.

2. Installations must not be installed directly in explosive rooms, since if they are fired and due to the high temperature of the outgoing gases (more than 800 ^o C), an explosion may occur in the room if an explosive concentration of vapors is found in the volume of the room to be protected flammable liquid (for gasoline from 0.76 to 8.12% by volume).

 3. It is useless to apply the generated aerosol to the tank to extinguish the fire through a layer of flammable liquid, since the aerosol loses its fire extinguishing properties.

 4. When transporting the generated aerosol through gas ducts (pipes), part of the aerosol (up to 50%) condenses on their walls and, accordingly, its quenching efficiency is reduced.

 5. Aerosol plants are supplied with disposable charges with a limited service life, therefore, when the protected premises are depressurized above 10%, the fire extinguishing effect drops sharply and the fire may not be extinguished.

The aim of the present invention is a method of extinguishing a fire on the surface of a combustible liquid, by supplying a solid fuel aerosol-forming substance to a burning surface, characterized in that in order to increase fire extinguishing efficiency, safety for firefighters in extinguishing fires of a tank with combustible liquids and reduce material and technical costs for extinguishing a fire solid propellant aerosol forming substance is supplied in the form of foam granules or foam cups with a specific gravity of not more than 80 n / m ³ , which corresponds to the density of foam granules street or foam cups of not more than 800 kg / m ³ , coated or impregnated with a waterproofing composition (resistant to water and to a protected combustible surface), as well as a device for implementing this method, containing a tank with a combustible liquid, a housing in the form of a sealed container with solid fuel aerosol-forming substance and an automatic shutter in which a sealed container is mounted on the hatch of the tank, its bottom is rigidly fastened to the container body by means of fusible locks, and a sealed lid is made in its upper part , Wherein the container walls are heat-insulated. At the same time, a removable protective casing is made over the upper part of the container.

 In FIG. 1 depicts one embodiment of a method for supplying foam granules to an open surface of a liquid of a burning tank using a powder extinguishing vehicle.

 In FIG. 2 - options for supplying foam granules for extinguishing a fire through technical pipelines for discharge and loading into a tank with a sagging roof, both from a pumping technological station and a fire tanker through a hydrant riser installed in the technological well.

 In FIG. 3 - a device with an automatic shutter (stationary, standby version) for supplying a fire extinguishing substance to a burning surface of a liquid.

The device contains mounted on the hatch 1 of the tank 2 with a combustible liquid 3, the housing 4, made in the form of a sealed container with solid propellant aerosol converting substance 5 and 6 and an automatic shutter. The bottom 7 of the housing 4 is rigidly bonded to the housing by means of a low-melting lock 8, consisting of a low-melting junction (72 ^o C) connecting the lower joint of the end part of the housing 4 with the bottom 7. In this case, a sealed cover 9 is made in the upper part of the housing 4, and the walls of the container body 4 are insulated with a protected layer 10 and a protective removable casing 11 is made over its upper part.

 The proposed method is implemented as follows.

 For fire protection of automobile and railway tanks with flammable and combustible liquids, reservoirs of gas stations, technological reservoirs of oil refineries and other reservoirs, the automatic shutter device shown in FIG. 3.

 For this purpose, fire extinguishing foam granules 5 or foam checkers 6, the outer surface of which is covered with a thin layer (0.1-0.5 mm) of the waterproofing composition, are loaded into the casing 4 of the sealed container. Foam granules 5, before loading them into a container, it is recommended to pre-pack, for example, in polyethylene sealed bags with a capacity of 0.5-1.5 l, in order to avoid excessive loss of extinguishing agent during loading and unloading and to protect it from moisture, as well as possible operational use bags with foam granules and foam cups for throwing them on the open surface of the liquid of a burning tank.

In the event of a fire in the tank 2, a fire flame (800-1000 ^o C) heats the bottom 7 and the lower part of the housing 4 of the sealed container, which are fastened together by a low-melting 8 junction (72 ^o C). The fusible joint 8 melts and the bottom 7 under its own weight falls down, together with the extinguishing agent 5 and 6, onto the burning surface of the combustible liquid 3.

From the temperature of the fire, the plastic bags melt (100 ^o C) and the foam granules scatter along the surface of the burning liquid, which helps to reduce the rate of vaporization of the upper layer of the combustible liquid and reduce its burning activity.

When the upper parts of the foam granules are heated to their ignition temperature (120-140 ^o C). The self-ignition temperature of the foam granules, without open flame, is above 500 ^o C, (3 p. 6) they ignite and form a fire extinguishing agent in the form of an aerosol, which inhibits reactions in a fire flame due to the death of their radicals on the surface of aerosol solid particles. Thus, a protective, boundary layer of aerosol is formed above the surface of the combustible liquid, which extinguishes the fire flame in 2-3 seconds.

The experiments on quenching of kerosene with foam granules with a diameter of 8-10 mm, with a specific gravity of 0.6 kg dm.cub. (with a density of 600 kg / m ³ ) showed that after burning kerosene and introducing foam granules onto its burning surface, they flared up after 20-30 seconds and after 1.5-2 seconds the burning of kerosene stopped. At the same time, the foam granules did not burn completely, and due to the reactive moment arising, they partially immersed in a combustible liquid and went out. After re-ignition of kerosene, its combustion continued for 1.5-2 minutes, then the foam granules ignited and extinguished the fire for 1.5-2 seconds.

 After eliminating the fire in the tank 2, (Fig. 3), the casing 11, which is weatherproof, is removed from the hatch 1, the container body 4 is removed and replaced with another, with a fire extinguishing charge.

 In the event of a fire, for example, a semi-underground tank 12 (Fig. 1), the overlap of which was partially destroyed by the explosion and there was free burning above the surface of the combustible liquid 3, the tank is extinguished either manually or using a powder fire extinguishing vehicle 13.

 When manually extinguishing a fire in tank 12, firefighters throw foam bags or pouches into the open opening of the tank, which get into the fire flame zone and ignite and the resulting aerosol force interrupts the combustion chain reaction (not shown in the drawing).

 It is known from the technical literature (see passport of the P-5 Purga fire-extinguishing aerosol generator (5, p. 3) that in order to achieve a fire-extinguishing effect in the boundary layer or volume of the protected object, it is necessary to introduce the required amount of extinguishing agent (foam granules) into the combustion zone within 0,063 kg / m3

 For example, to extinguish flammable liquid on the surface of an open reservoir of the RVS-3000 type, whose mirror area is 375 square meters, it will be necessary to throw bags with foam granules or foam dampers with a total weight of 24 kg within one minute, over its entire surface.

 Foam granules or foam cups during combustion form around them a fire extinguishing force of an aerosol, the volume of which is 1600 times their original volume in the solid state.

If its granule has time to burn when flying in a fire flame, then it falls onto the surface of a combustible liquid, drowns in it and goes out due to its cooling, and then floats to the surface. Since the boiling point of, for example, burning alcohol is 78.4 ^o C, and the ignition temperature of the foam granules is 120-140 ^o C, the foam granule will go out when the surface is wetted with a combustible liquid, and then, with subsequent combustion, if the fire was not completely extinguished, foam granules reignite from a flame of a burning liquid and extinguish a fire.

 When extinguishing a reservoir 12 with a burning liquid 3, foam granules from a reservoir of a fire-extinguishing powder fire truck 13 are supplied either from its fire monitor barrel or from hand barrels, the length of the hose lines of which is 30 m (not shown in the drawing).

 In the event of a fire in the ground tank 14 (Fig. 2), in which the roof is partially damaged or it has subsided and it is difficult to enter extinguishing agents onto its burning surface, then foam granules are fed into the tank through its process pipelines 15 and 16 through a layer of flammable liquid 3.

 For this purpose, a container 18 for storing fire-extinguishing foam granules is equipped in the pumping station 17 and in case of fire, the tank is connected to the process pipe 15 of the burning tank and by means of compressed inert gas or water from the fire-water supply system, or from the booster pump of the fire-water supply system of the foam granule from the tank 18 are transferred to the burning tank 14. Foam granules float to the surface of the burning liquid 3, are heated by a fire flame and ignited, the aerosol of which volumetric mode eliminates combustion.

 The fire in the tank 14 can also be eliminated with the help of fire fighting equipment, a special tank 19 loaded with foam granules and a fire tanker 20. At the same time, a technological hydrant 22 is installed on the discharge and loading pipelines 15 or 16, in the technological well 21. During a fire, fighters install on the hydrant 22, the fire column 23 and flexible fire hoses connect it to the tank 19 and from the tank 20, water is supplied through the fire hose and the foam granules are forced out into the pipeline 16 and to the burning tank 14.

 The implementation of a fire extinguishing, solid propellant aerosol-forming substance in the form of foam granules or foam cups allows more efficiently and in the initial stage of the development of a fire to eliminate fires in tanks with flammable and combustible liquids, and an environmentally friendly substance.

 The implementation of a device for supplying a fire extinguishing medium to a burning surface of liquid, made in the form of a tank of a combustible liquid mounted on the hatch, of a case of a sealed container with a fire extinguishing substance and an automatic shutter, enhances the fire safety of transport and the transport of combustible liquid in transport tanks and helps to reduce the fire hazard of technological reservoirs in which the flammable liquid is constantly subject to stirring or unloading, in addition, the absence of foam granules and foam cups of initiating ignitors excludes their probability of false operation (ignition).

 Performing a protective removable casing over the upper part of the container increases the reliability and durability of the device and extinguishing agent (at least 10 years) and protects the extinguishing agent from thermal solar radiation and precipitation.

 Savings from the use of the proposed fire extinguishing agent and device for its implementation is obtained due to the manufacturability of their manufacture and the effectiveness of fire fighting, with little involvement of forces and means.

Claims (3)

1. A method of extinguishing a fire on the surface of a combustible liquid by supplying a solid fuel aerosol forming substance to the burning surface, characterized in that the solid fuel aerosol forming substance is supplied in the form of foam granules or foam cups with a specific gravity of not more than 80 n / m ³ coated with a waterproofing composition.  2. A device for supplying a fire extinguishing medium to a burning liquid surface, comprising a housing in the form of a sealed container with a fire extinguishing agent and an automatic shutter installed on a tank with combustible liquid, characterized in that the sealed container is mounted on the hatch of the tank, its bottom is rigidly fixed to the container body by fusible locks, and in its upper part a sealed cover is made, and the walls of the container are thermally insulated.  3. The device according to claim 2, characterized in that a protective removable casing is made over the upper part of the container.

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