RU2283674C2 - Method and system for fire extinguishment in special-purpose closed objects - Google Patents

Abstract

FIELD: fire protection, particularly to extinguish fires in special-purpose sealed objects.

SUBSTANCE: method involves determining volumetric oxygen content and total gaseous mixture pressure in closed object; supplying inert gas in the object to obtain volumetric oxygen content, which does not sustain combustion. Carbonic oxide content is also measured in the closed object to discover smoldering initiation along with controlling temperature, temperature difference and optical density of gaseous mixture to detect ignition process beginning. Inert gas is supplied under inert gas supply control to provide total pressure increase rate of not more than 8 kPa/s and to decrease volumetric oxygen content up to 15% under partial oxygen pressure of not less than 12 kPa. Total gas pressure does not exceed 0.4 MPa. Fire-extinguishing system comprises inert gas cylinders, standby inert gas sources, distribution manifolds with stop valve connected with control device, oxygen gas-analyzers, which determine oxygen content, fire alarms also linked to control device, hydrogen and carbonic oxide analyzers, which determine hydrogen and carbonic oxide content, pressure and temperature sensors, controllable gas discharge means attached to control device. The control device has data validity analyzing means, power supply unit, display and signaling unit, computer, commutation unit. Device also comprises inert gas supply limitation unit. Distribution manifold outlets are provided with means, which dilute inert gas at manifold outlets.

EFFECT: increased safety of people in air-tight altitude chambers, decompression chambers and other closed objects.

2 cl, 2 dwg

Description

The invention relates to fire safety.

Known methods and systems for extinguishing a fire by supplying sprayed water, foam, powder, halogen-hydrocarbon compositions of freons and inert gas to the combustion zone (see the reference book “Fire Safety. Explosion Safety” / Edited by A. N. Baratov: “Chemistry” ", 1987).

However, the well-known solution to the use of water, along with the advantages, has a high inertia and can lead to damage to electrical equipment, and when extinguishing a fire in a sealed object, to a dangerous increase in pressure up to an explosion. The use of foam or powder is a highly expensive fire extinguishing method and insufficiently effective due to the small protected area and the inability to supply a fire extinguishing agent to a fire site located in a remote place. The use of chladones is limited, since the products of thermal decomposition of chladones are highly toxic and highly corrosive.

In addition, the fire extinguishing ability of these substances under overpressure has been little studied. Therefore, it seems most appropriate to use gas fire extinguishing systems in closed specialized premises, based on the creation of a gaseous environment in the protected facility that does not support combustion.

A known fire extinguishing system in an enclosed space (RU No. 2066217 C1, class A 62 C 37/36, 1996), selected as a prototype, which uses an inert gas fire extinguishing method, which consists in controlling the fact of fire, oxygen concentration and supply of inert gas to the object upon ignition to reduce the volumetric oxygen content, at which the combustion process containing inert gas tanks, inert gas reserve sources, distribution pipelines with shut-off valves with actuators connected to the device stops control system, oxygen gas analyzer, fire detectors, also associated with the control device, and an inert gas flow control sensor.

The disadvantages of the prototype method and the system is the need to evacuate people from the enclosed space of the tunnel before applying nitrogen to the tunnel to extinguish the fire.

The objective of the invention is to ensure the fire safety of people in pressurized objects (pressure chambers, decompression chambers and other pressurized objects having a high density layout of power cables, electrical equipment, life support systems, etc. and difficult access to fire objects) by early fire detection, confirmation of reliability fire occurrence and volumetric fire extinguishing with a high degree of reliability. The technical result is achieved by the fact that in the method of extinguishing a fire in closed specialized facilities, which consists in determining the volumetric oxygen content and supplying an inert gas to the object until the volumetric oxygen content is reached, at which the combustion process stops, unlike the known one, the total pressure is measured gas mixture and the content of hydrogen and carbon monoxide in it, determining the beginning of the smoldering process, at the same time control the temperature, temperature gradient and optical the density of the gas mixture inside the object to determine the beginning of the ignition process, determine the location of the fire and regulate the inert gas supply with a rate of increase in total pressure of not more than 8 kPa / s to reduce the volumetric oxygen content below 15% at a partial oxygen pressure of not less than 12 kPa, not exceeding the absolute gas pressure of 0.4 MPa.

The technical result is achieved by the fact that in a fire extinguishing system in closed specialized facilities containing inert gas tanks, inert gas backup sources, distribution pipelines with shutoff valves connected to the control device, oxygen gas analyzers, fire detectors, also associated with the control device, unlike the known, hydrogen and carbon monoxide gas analyzers, pressure and temperature sensors in the pressurized compartment, adjustable means of gas discharge, all connected output control pipelines equipped with an inert gas restriction device, and at the outputs of the distribution pipelines, inert gas dilution devices are installed.

The outlet pipelines through which the gas is discharged when the object is purged are equipped with adjustable means of gas discharge installed at their outlet and connected to the control device.

An inert gas, such as nitrogen, is used to act on the ignition source. The supply of nitrogen to the object is controlled and regulated by a control device.

The essence of the method is to prevent the occurrence of a fire and, if it develops, to dilute the gaseous medium inside an airtight object or group of airtight objects with an inert gas with nitrogen to reduce the oxygen content of less than 15% while maintaining a partial oxygen pressure of at least 12 kPa and the rate of increase of gas pressure in a sealed object not more than 8 kPa / s, while not exceeding the absolute pressure in a sealed object more than 0.4 MPa. The choice of fire extinguishing process parameters is due to:

the need for early fire detection by the appearance in the gaseous medium of combustion products released during the decay of most substances, such as, for example, hydrogen and carbon monoxide;

the impossibility of maintaining the combustion process of most substances at a volume concentration of oxygen of less than 12-15%, with the exception of flammable substances, the presence of which in sealed objects designed to perform special tasks is significantly limited (see the reference book Fire Safety. Explosion Safety / Ed. Baratova A.N. M.: Chemistry, 1987, p. 134);

the need to limit the growth of total pressure when applying a sealed object with a diluent gas from the point of view of human physiology;

in the absence of the possibility of purging the sealed object with inert gas to reduce the volume fraction of oxygen and maintain the required level of its partial pressure, it will be necessary to pressurize the sealed object with nitrogen, which will increase the total pressure, since the partial pressure of oxygen is the product of its volume fraction by the total gas pressure mixtures. However, this increase in pressure is limited. At absolute pressures above 0.4 MPa, the narcotic effects of nitrogen begin to appear. In addition, after a person is in a gas environment with an excess pressure of up to 0.3 MPa, decompression will be required to remove dissolved nitrogen from the blood, the duration of which depends on the maximum gas pressure;

in cases where it is allowed to discharge gas from an object overboard, it is proposed to purge a sealed object in the absolute pressure range from 0.2 to 0.4 MPa by adjusting the ratio of the flow rate of the supplied nitrogen and the gas mixture removed from the compartment by the need to ensure an acceptable level of oxygen partial pressure in a gas mixture for normal human breathing;

the lower level of oxygen partial pressure is selected based on the ability of the human body to exist without functional disorders for no more than 3 days - a time sufficient to eliminate the fire;

the need for quick pressurization of an airtight object to eliminate the fire at a speed that is acceptable for a person to increase pressure;

the rate of increase in pressure is selected as maximum permissible from the point of view of human physiology, determined experimentally;

the need to save gas diluent consumption, especially in the case of autonomous functioning of a sealed object or a group of functionally connected sealed objects.

The essence of the invention is illustrated by drawings, which show:

figure 1 - fire extinguishing system;

figure 2 is an embodiment of a control device circuit.

The system contains inert gas containers (cylinders) 1, inert gas backup sources (cylinders) 2, protective filters 3, inert gas pressure sensors 4, total pressure sensors 5, gas temperature sensors 6, distribution pipelines with shut-off valves - valves 7, 24 -32, control device 8, gas analyzers of oxygen 9, gas analyzers of hydrogen and carbon monoxide 10, fire detectors - thermal linear 11, combined 12, autonomous sources of inert gas cylinders 13, adjustable means of gas discharge 14 with pipelines, arrangement Inert gas supply restriction 15, filling valves 16, at the outputs of the distribution pipelines, dilution devices for the inert gas 17 entering the outlet are installed.

The thermal linear fire detector 11 (thermal cable) is a cable that allows you to detect a heating source in any place along its entire length. The thermal cable is a single continuous sensor, which consists of two or three steel conductors, each of which is covered with thermoplastic material. The conductors are twisted together to create mechanical stress between them and additionally covered with an external protective sheath. The control current from the interface module is constantly passing through the thermal cable. At the response temperature, the thermoplastic material is forced through due to the mechanical tension of the conductors and they close.

Combined fire detectors 12 simultaneously monitor the ambient temperature, the rate of temperature increase and the optical density (degree of smoke) of the gas environment.

Inert gas supply restriction devices 15 are uncontrolled chokes, the design characteristics of which are selected to ensure an acceptable rate of pressure increase in a sealed object. The dilution device for the inert gas 17 that is output is made in the form of injectors with silencers.

Injectors are used to mix the flow of inert gas (nitrogen) with the gas medium inside the object in order to prevent the formation of zones with a high nitrogen content, which can be dangerous for breathing of people who are in these zones.

Silencers are required to suppress noise arising during the movement of gas in pipelines at high speeds when they flow out of containers with inert gas under high pressure (about 30 MPa).

Adjustable gas discharge means 14 are designed to reduce the oxygen content in the sealed object by less than 12% in the purge mode by maintaining a constant pressure in the sealed object when it is pressurized with inert gas and are adjustable chokes to ensure that excess gas is discharged at a rate equal to the inert gas supply to an object. The gas purge of the sealed object through adjustable gas discharge means 14 is terminated by commands from the control device 8 with a volumetric oxygen content of less than 12%, but no later than reaching a partial oxygen pressure of 12 kPa. The purge mode is more preferable in relation to the boost mode from the point of view of physiology, since after its completion no additional decompression will be required.

The control device 8 comprises (see FIG. 2) a power supply unit 18, a signal processing unit 19, a signal reliability analysis unit 20, an indication and signaling unit 21, a computing unit 22 and a switching unit 23.

The control device 8 is electrically connected (see figure 2) with inert gas pressure sensors 4, pressure sensors in objects 5, gas temperature sensors in objects 6, shutoff valves - valves 7, 24-32, oxygen gas analyzer 9, hydrogen and oxide gas analyzers carbon 10, fire detectors - thermal linear 11, combined 12 and adjustable means of gas discharge 14.

The control device includes a power supply connected to the signal processing unit 19, the inputs of which are also connected to gas analyzers of hydrogen and carbon monoxide 10 and fire detectors 11, 12, an oxygen analyzer 9, an inert gas pressure sensor 4, a pressure sensor 5 and gas temperature 6 in the compartments and the outputs are connected to the inputs of the signal reliability analysis unit 20, the indication and alarm unit 21 and the computing unit 22, which in turn is connected to the switching unit 23, the output of the signal reliability analysis unit 20 is connected to the other input of the indication and signaling unit 21, connected by the inputs and outputs to the computing unit 22, the switching unit 23 is further connected to the electric actuators of the valves of the shutoff valves 24-32 and adjustable means of gas discharge 14; the valve position indicators 33, which are part of the design of valves and connected to the signal processing unit 19.

The signal processing unit 19 receives information from hydrogen and carbon monoxide gas detectors 10 and fire detectors 11, 12, oxygen gas analyzers 9, inert gas pressure sensors 4, valve position sensors 33, pressure sensors 5 and gas temperature 6 in the compartments, translates it into a digital code and distributes to the signal reliability analysis block 20, where false signals from fire detectors 11, 12 are recognized and blocked, to the indication and alarm block 21, where the audiovisual system status is monitored we are fire extinguishing, as well as in computing unit 22, which produces:

continuous calculation of maximum boost pressure in case of fire,

determination of the current reserves of inert gas and the required amount for boosting the emergency facility,

selection of the preferred boost or blow mode and issuing recommendations to staff,

implementation of the algorithm of boost or blow mode when activated by the operator,

issuing commands to the switching unit 23 and further to the electric actuators of the valves of the shutoff valves 7, 24-32 and adjustable means of gas discharge 14.

Autonomous inert gas sources 13 with a distribution pipe with shut-off valves - valves 30, 31, inert gas tanks 1 and inert gas reserve sources 2 are located outside the sealed facility to increase operational safety, the rest of the equipment is inside the sealed facility to ensure autonomous operation.

The system operates as follows. From the moment of switching on, the control device 8 constantly receives information from hydrogen and carbon monoxide gas analyzers 10 and fire detectors 11, 12, pressure sensors 4, 5 and temperature 6, position indicators of valves 33 of shutoff valves and adjustable gas vents 14 and analyzes the fire situation in closed specialized facilities.

In the computing device 22, the maximum pressure is continuously calculated to which an emergency facility can be inflated to reduce the volumetric oxygen content of less than 12%. At the same time, the current reserves of inert gas are determined to select the source of inert gas in the event of a fire. The calculation results are received in the display and alarm unit 21.

When the gas 10 or thermal linear 11 fire detectors are triggered at the lower alarm level, the signal processing unit 19 gives a signal about the threat of a fire during local overheating or the onset of smoldering to the indication and alarm unit 21. The staff takes measures to eliminate the fire source, de-energizes the power equipment, uses fire extinguishers, etc. When a hydrogen gas analyzer and carbon monoxide 10 or a heat line 11 of a fire detector are triggered at the upper alarm level or when combined detectors 12 are triggered, the signal reliability analysis unit 20 checks the reliability of the signals and, when there is no false alarm, a fire signal is sent to the computing unit 22. Upon receipt of the signal, the computing unit 22 provides information on the location of the fire and recommendations to personnel on the process of volumetric fire extinguishing to the display and alarm unit 21.

In accordance with the recommendations, the staff chooses manual or automatic fire extinguishing. The automatic fire extinguishing program available in the computing unit 22 provides for the implementation of both boost mode and purge mode. Moreover, in the boost mode, the emergency compartment is pressurized up to 0.4 MPa abs., And in the purge mode, the total pressure in the compartment is constant at a volumetric oxygen content of less than 12% by volume and a partial oxygen pressure of at least 12 kPa. The purge mode is more comfortable for the body, but longer. The choice of modes is carried out by the operator depending on the rate of fire development.

When the boost mode is started, the control unit 8 determines the emergency object, the required amount of nitrogen for the required pressure increase and the amount of nitrogen in the inert gas tanks 1, in the reserve inert gas sources 2 and in the autonomous inert gas sources 13 and sets the priority for their use.

Then, the computing unit 22 issues commands to the switching unit 23 to turn on the corresponding valve actuators of the stop valves to open the valves providing gas from the selected containers or sources of inert gas to the emergency facility. To pressurize one of the sealed compartments GO1-GO4, for example, the compartment GO1, valves 19, 28, 29 are opened sequentially from inert gas tanks 1 and gas through inert gas flow restriction devices 15 enters the dilution device for inert gas 17 and further dumped in GO1.

If the pressure monitored by pressure sensors 4 in the inert gas source decreases to a minimum value, for example, in tanks 1, the computing unit 22 issues commands to the switching unit to close valve 19 and switch to supplying inert gas from the backup source 2 and to open valves 7 and 24.

Upon reaching the design pressure in the object, the computing unit 22 issues commands to close all valves of the shutoff valves. In order to avoid supercharging when pressure reaches 0.4 + 0.5 MPa, the safety valves are automatically opened in the emergency facility (not shown in FIG. 1 as not related to the fire extinguishing system and included in the design of the facility).

When the purge mode is started, the computing unit 22, after prioritizing the use of inert gas sources, determines the sequence of signal output to the switching unit 23 to control the corresponding valves of the shutoff valves 7, 24-32 and adjustable means of gas discharge 14 to fulfill the conditions indicated above.

In the event of a failure of the control device, personnel can extinguish the fire using duplicate manual actuators of shut-off valves and adjustable means of gas discharge 14 located inside the sealed object.

The main purpose of autonomous inert gas sources 13 is to extinguish a fire in an airtight object where the control device 8 is located, in case it is impossible to function due to a fire. The inert gas supply from an autonomous source can be additionally carried out using manual valves of shutoff valves located outside the sealed object.

During the implementation of the proposed technical solution is provided:

regulating the supply of an inert gas extinguishing agent with a person’s safe rate of pressure increase and limiting the permissible maximum pressure and maintaining the volumetric oxygen content at a level that excludes the continuation of the combustion process and the partial oxygen pressure at the level necessary to preserve the life of personnel in an emergency facility during a fire response;

prompt supply of inert gas, taking into account the physiological capabilities of the human body, the economical use of inert gas and, if necessary, the use of reserve reserves of inert gas;

automatic and manual modes of volumetric fire extinguishing;

maximum integrity of equipment in an emergency tight facility;

additional capabilities of volumetric fire extinguishing due to autonomous inert gas reserves.

Claims (2)

1. A method of extinguishing a fire in closed specialized facilities, which consists in determining the volumetric oxygen content and supplying an inert gas until the volumetric oxygen content is reached at which the combustion process is stopped, characterized in that the total pressure of the gas mixture and its hydrogen content are measured and carbon monoxide, determining the beginning of the smoldering process, simultaneously control the temperature, temperature gradient and optical density of the gas mixture to determine the beginning of the process ca ignition and controlled supply of inert gas at a rate higher overall pressure is not more than 8 kPa / s to reduce the bulk oxygen content below 15% at an oxygen partial pressure of not less than 12 kPa and not exceeding the value of gas pressure 0.4 MPa absolute. 2. Fire extinguishing system in closed specialized facilities, containing inert gas tanks, reserve inert gas sources, distribution pipelines with shutoff valves connected to the control device, oxygen gas analyzers, fire detectors, also associated with the control device, characterized in that introduced gas analyzers of hydrogen and carbon monoxide, pressure and temperature sensors, adjustable means of gas discharge, all connected to a control device equipped with an analysis unit fidelity signals, power supply, display and alarm unit, computing unit, switching unit, the output distribution lines are equipped with devices limiting the supply of inert gas, and at the outputs of the distribution pipes installed dilution device entering the inert gas outlet.

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