HIGHLY EFFICIENT WATER MIST FIRE EXTINGUISHING SYSTEMS BASED ON AEROSPACE TECHNOLOGIES.

HIGHLY EFFICIENT FIRE EXTINGUISHING SYSTEMS WITH FINE-MISTRED WATER BASED ON AEROSPACE TECHNOLOGIES..

KARPYSHEV Aleksandr Vladimirovich, Candidate of Technical Sciences
SEGAL Mikhail Davydovich, Doctor of Technical Sciences
STEPANCHIKOV Vladimir Ivanovich, Candidate of Chemical Sciences

HIGHLY EFFICIENT FIRE EXTINGUISHING SYSTEMS WITH FINE-MISTRED WATER BASED ON AEROSPACE TECHNOLOGIES

Source: magazine «Special Equipment» No. 2 2006.

According to the Main Directorate of the State Fire Service of the Russian Emergencies Ministry, over 143,568 fires were registered in the Russian Federation in the first 8 months of 2005. 10,980 people died in fires, including 460 children, and 8,562 people were injured in fires. Material losses from fires amounted to almost 60 billion rubles. Cities accounted for 67.2% of the total number of fires, 60.5% of material damage, 57.7% of estimated losses, 57.5% of people killed in fires, and 69.7% of those injured. Most fires were registered in the residential sector: their share of the total number of fires in Russia was 72.8%, and material damage – 39.7% [1].

In terms of the number of deaths per thousand fires, Russia ranks first in the world, exceeding the same indicator in the USA by 33 times, and in England by 38 times.

In the state report of the Russian Emergencies Ministry “On the state of protection of the population and territories of the Russian Federation from emergency situations of natural and man-made nature” it was noted that due to the reduction in the number of GPS units, high wear and tear of fire-fighting equipment and the deterioration of the situation on the roads, the indicators of prompt response to fires have decreased.

The average time of arrival of the first fire unit to the scene of the call is constantly increasing and amounted to more than 8 minutes in cities, more than 19 minutes in rural areas.

It should be noted that these are some average figures, which may differ significantly in large cities. Due to the extremely difficult traffic situation in Moscow and mass violations of parking rules, the time of arrival of fire brigades and the beginning of firefighting operations may be quite long, which leads to a sharp increase in the area of ​​the fire.

As for the situation in other sectors of the economy, we can note the increasing fire hazard in industry, construction, energy facilities, communications, transport, mining and processing of minerals. This is due to both the use of significant quantities of fire hazardous substances and compounds, and the progressive wear and tear of equipment (in a number of industries, the wear and tear of fixed assets reaches 70-90%), deterioration of technological discipline and a decrease in the qualifications of personnel at potentially hazardous production facilities.

Major fires in Moscow (the dormitory of the Peoples' Friendship University, the buildings of the Variety Theatre, the Arbitration Court, and the Manezh) have shown that it is necessary to re-equip fire protection services and fire protection units with qualitatively new equipment. Such equipment can only be created on the basis of high technologies with the involvement of the resources and scientific potential of the military-industrial complex.

In this regard, domestic developments of new highly effective fire extinguishing systems with finely atomized water are acquiring a special role.

Based on the latest achievements in rocket and space technology, specialists have created gas-dynamic technologies for extinguishing fires with finely atomized water, which significantly surpass known analogues and a number of existing installations that have proven themselves in operation.

The most famous development is the backpack fire extinguishing installation RUPT-1-0.4 (photo 1) — designed for the rapid suppression of fires of solid flammable substances, flammable liquids and gases, as well as for extinguishing fires of electrical equipment under voltage up to 36 kV.

The installation uses the principle of gas-dynamic acceleration of a finely atomized (average water droplet size is about 100 microns) two-phase (water – air) flow, which allows for the rapid suppression of fires at an early stage of combustion with very high efficiency.

The unit is characterized by its small dimensions and weight (about 20 kg in full configuration), simplicity and reliability in operation, constant readiness for work, absolute environmental safety. Ordinary water or water with a foaming composition in the amount of about 12 liters is used as a fire extinguishing liquid. The unit operates from a 2 liter compressed air cylinder with an operating pressure of 300 atm, similar to those used in breathing apparatus for firefighters, which allows creating a jet of finely atomized liquid with a range of up to 15 m.

Photo 1. Backpack fire extinguishing unit RUPT-1-0.4

During certification tests of the unit in Russia and abroad, it was confirmed that the unit can be successfully used to eliminate:

• fires of solid combustible materials with a combustion surface area of ​​up to 61 m2, which corresponds to the area of ​​an average apartment, including smoldering combustion; during these tests, a fire in an apartment was extinguished with 9 liters of liquid;
• fires of flammable liquids (gasoline, kerosene, heptane, various oils, etc.) with an area of ​​up to 7.3 m2, and in case of spills — even a larger area, while during the tests it was shown that 9 liters of fire extinguishing agent is enough to extinguish more than 200 liters of burning gasoline,
• fires of electrical equipment under voltage of up to 36 kV from a distance of more than 1 m.

These properties of the installation distinguish it from existing fire extinguishing means, since they allow:

• to exclude flooding of premises with a large amount of water and completely avoid secondary damage, which is especially important in case of fires in the residential sector, when up to a ton of water is spent on extinguishing a fire in one average apartment and subsequent flooding;
• extinguish fires in the presence of personnel, which is impossible when using gas, powder and aerosol fire extinguishing systems;
• conduct prompt extinguishing of fires in electrical installations without disconnecting the power supply.

The RUPT-1-0.4 unit can be successfully used to improve fire protection for industrial facilities, residential buildings and premises, offices, cultural institutions, stores, healthcare facilities, as well as in crowded places where powder, gas and aerosol fire extinguishing agents cannot be used until people have been evacuated.

The unit is effective for use in all enterprises where flammable liquids are used or produced, as well as in garages, fuel and lubricants warehouses, gas stations and parking lots. Special fire tests conducted in France showed that the unit with a water reserve of 9 liters is capable of completely extinguishing a burning passenger car in 3-4 minutes.

A particularly important advantage of the installation is the ability to extinguish electrical equipment without disconnecting the power supply. This, firstly, allows for a time gain in the event of a fire, and secondly, will help avoid the failure of expensive electronic and electrical equipment, which is inevitable when using powder or aerosol fire extinguishing systems.

Based on statistical data on the area of ​​the fire by the time fire crews arrive, it can be stated that almost 90% of all fires can be successfully extinguished using the RUPT installation, which will avoid significant material damage.

The installation has a European certificate, a Russian fire safety certificate, was awarded gold medals at the 48th World Salon “Brussels-Eureka 99” and the 28th International Salon (April 2000, Geneva), as well as the Russian Federation Government Prize for 2000.

At present, new technical means of extinguishing fires with finely atomized water have been created and tested, which can find the widest application at various economic facilities and, what is especially important, at energy and transport facilities.

As a result of a complex of scientific research and development works, a highly effective air-emulsion fire extinguisher was created, generating a jet of finely atomized liquid with a range of up to 7-8 m, allowing extinguishing of solid substance fires of up to 6A rank (including smoldering combustion), flammable liquids of up to 183V rank and electrical equipment under voltage of up to 1 kV. The weight of the fire extinguisher in a complete set is 9 kg, the volume of the extinguishing agent is 6 liters (photo 2).

Photo 2. Air-emulsion
fire extinguisher

The operating temperature range of the fire extinguisher is from –30 to +50? C. The extinguishing agent used in the fire extinguisher is safe for people, which is confirmed by the corresponding hygienic certificate.

In May 2005, the first fire tests of the fire extinguisher were conducted in a tunnel of the Moscow Metro at a working voltage of 825 V DC on the contact rail. The purpose of the tests was to experimentally confirm the complete safety of using the fire extinguisher to extinguish fires under voltage. During the tests, fires (rags soaked in kerosene) were ignited under the protective box of the contact rail and on the rigid base of the track under the contact rail. The operator extinguished from a distance of 2 m from the contact rail, without using any personal protective equipment. All fires were successfully extinguished within about 25 s.

For prompt extinguishing of fairly large fires and spills of flammable liquids with an area of ​​more than 30 – 40 m2 developed a water mist fire extinguishing system, which moves on wheels, with a water or extinguishing agent reserve of up to 50 liters. The main hydrodynamic characteristics of the finely atomized liquid flow in this device are similar to a knapsack one. The use of such a device allows not only to quickly extinguish fires of classes A, B and E, but also to use it in combination with a portable breathing apparatus AIR, which allows you to stay at least an hour in the fire.

For prompt arrival at the fire site, a first aid fire truck (FAF) based on the Gazelle chassis has been developed, which is a highly mobile compact complex for extinguishing the most common fires. The vehicle is equipped with a portable monitor and hand-held nozzles for supplying finely dispersed fire extinguishing liquid, RUPT backpack units, auxiliary and rescue equipment. The water or fire extinguishing liquid reserve is 350 liters, the nozzles provide the supply of fire extinguishing composition with a flow rate of up to 2 l/s with a range of up to 30 m. A motor pump allows for water intake from an external source. The combat crew is 5 people.

Fire extinguishing with finely atomized water at nuclear and radiation hazardous facilities

Due to the particular acuteness of the population's perception of the danger of radioactive contamination from nuclear industry enterprises, in this article we will pay attention to some features of fire extinguishing at nuclear industry enterprises and the possibility of using technical devices that generate jets of finely atomized water and finely atomized fire extinguishing agents.

The uniqueness of the fire hazard of enterprises in this industry compared to other industries is determined by the following factors:

• the performance of fire extinguishing tasks should not lead to disruptions or loss of control and management of the reactor facility for reasons of nuclear and radiation safety;
• in some cases, difficulty or impossibility of access to the fire site (risk of radiation, need for special protective equipment, limited stay);
• the need to maintain a certain level of hermetic sealing of protective shells of nuclear and radiation hazardous facilities (NRFH) in order to limit the release of radioactivity into the environment. Even a minor fire at vulnerable facilities in the industry (nuclear reactor, radiochemical plant (RCP), spent nuclear fuel storage facilities) can lead to an uncontrolled release of radioactive materials into the atmosphere;
• restrictions in the choice of means that can be used for fire extinguishing. The appearance of excess amounts of water during fire extinguishing in some areas of nuclear power plant units, research reactor installations, critical assemblies, fuel element storage facilities may affect the neutron-physical characteristics of the installations, and in some cases lead to the emergence of a self-sustaining chain reaction;
• during the extinguishing process, the formation of “secondary” radioactive waste is possible, which also requires special handling, in particular, they must be analyzed and then isolated.

As the analysis of the fire situation at nuclear industry enterprises in Russia shows, it remains quite complicated. Thus, over the last five years, 27 fires have occurred at NPPs. The largest number of fires occurred at the following nuclear power plants: Novovoronezh — 8, Kursk — 7 and Smolensk — 6. In 1999, 4 fires were registered — at the Kursk, Kalinin, Smolensk and Novovoronezh NPPs. At the same time, at the Kalinin NPP, 3 people died in a fire, 1 received third- and fourth-degree burns, 3 were poisoned by combustion products. In 1993, a fire occurred at the radiochemical plant of the Siberian Chemical Combine in Tomsk-7 for reprocessing spent fuel elements [3 — 5].

Of the 158 fires at NPPs with light-water reactors, about 25% of the fires could have resulted in consequences associated with a nuclear hazard. In 9% of fires, a safety-related function of the equipment was suppressed. In 16%, a fire occurred that could have damaged the safety-related equipment if it had not been quickly detected and extinguished [4, 5].

The most dangerous areas at nuclear power plants include cable rooms, machine rooms, and electrical equipment. The main combustible material in the first case is cable insulation, in the second case it is turbine oil, and in all cases the amount of combustible material in one room is measured in tons, and the possible burning area is tens and even hundreds of square meters. A common feature of fire development in the rooms in question is the release of a large amount of smoke containing toxic products.

Most often, fires occur due to malfunctions and violations of the operating rules of electrical installations (26.1%), during fire work (21.4%), due to careless handling of fire (17.8%), from process equipment (13.8%), household electrical appliances (13.2%), i.e. in most cases from causes that could have been prevented [4].

All nuclear fuel cycle enterprises in its broad sense include potentially fire-hazardous objects already considered earlier for nuclear power plants, such as cable lines, switchboards, etc., with their characteristic fire extinguishing features.

According to many experts, finely atomized water is the most effective and promising means of extinguishing fires at nuclear power plants, primarily in machine rooms, cable mezzanines and passages, in rooms with oil-filled equipment, and RDES rooms.

The high efficiency of the RUPT backpack fire extinguishing system was demonstrated during fire tests on extinguishing electric cables at the VNIIPO site. During the tests, two cable bundles were ignited, each consisting of 10 sections of cable with a diameter of 25 mm (PVC insulation) and a length of 3.5 m. The bundles were located one above the other in a horizontal plane and ignited with gasoline. The free burning time was about 3 — 5 minutes. Extinguishing was carried out with tap water without additives. As a result of the tests, the cable bundles were extinguished with 6.5 liters of water in about 25 seconds. Repeated No fire was observed during the tests.

There are a significant number of rooms in the industry equipped with electronic and electrical equipment with permanent presence of personnel, including control and management systems. For such rooms, the use of gas fire extinguishing systems recommended by regulatory documents requires special equipment in order to exclude impact on personnel. For example, placing equipment elements (blocks, consoles, panels) in special sealed cabinets equipped with modular gas fire extinguishing systems. Due to the complete safety of finely sprayed water fire extinguishing systems, it is possible to quickly extinguish a fire without preliminary evacuation of personnel, which is especially important from the point of view of maintaining nuclear and radiation safety of the facility, since in a number of rooms the permanent presence of personnel is required.

At the same time, fire extinguishing is carried out with minimal water consumption, which helps avoid secondary damage and equipment failure.

It is important to note that, in accordance with the established procedure, GPS units can begin extinguishing installations under voltage of 0.36 kV and higher only after disconnecting electrical equipment. At the same time, it is impossible to de-energize all electrical equipment and cables in the zone and on the approaches to the fire zone in some cases due to the power supply conditions and safety of the reactor installation. Such a disconnection can lead to loss of control and management of the reactor installation, the impossibility of cooling the reactor, as well as the inoperability of emergency systems and fire extinguishing installations.

Tests of the RUPT backpack installation on special electrical stands at Mosenergo OJSC and the Scientific Research Institute of Science and Technology at the Moscow Aviation Institute confirmed the electrical safety of the installation at alternating current voltages of up to 36 kV.

The prospects of using technologies for generating finely atomized liquid jets for nuclear industry facilities are confirmed by the fact that the procedure for using water mist fire extinguishing systems for a number of NPP premises is set out in the recently published regulatory document “Fire Protection of Nuclear Power Plants. Design Standards” – NPB 114-2002 [6].

According to this document, it is recommended to supply fire extinguishing agents in a finely atomized form (atomized and finely dispersed water, air-mechanical foam) in the form of powerful pulsed jets with a low consumption of fire extinguishing agents for fire protection:

• oil tanks of turbo units and feed pumps (irrigation intensity 0.2 l/m2 s);
• oil systems of high and low pressure cylinders of turbines (irrigation intensity not less than 0.3 l/m2 s);
• transformers, autotransformers (irrigation intensity 0.2 l/m2 s).

In the industry, fire-fighting equipment that reduces the time between the outbreak of a fire and the start of its extinguishing is of great importance. These are sprinkler and deluge automatic fire extinguishing systems.

Backpack and mobile fine-mist water fire extinguishing systems can be used as an additional means of fire extinguishing in the event of failure of automatic systems (or as an additional means of localizing a fire), as well as in the absence of water in fire hydrants.

Table 1 shows the possibilities of using these systems in the nuclear industry [2 – 5, 8].

Conclusion

Many domestic and foreign experts believe that the most promising are fire extinguishing technologies using finely atomized water. They are currently developing at an accelerated pace.

Our country has a significant scientific and technological reserve in this area due to the use of the latest achievements of domestic aerospace technologies.

Further development of work on fire extinguishing technologies using finely atomized water will allow:

• to maintain world leadership in the field of creating the latest fire extinguishing systems;
• re-equip the fire departments of the Russian Emergencies Ministry with the latest fire-fighting equipment, which will improve the efficiency of fire extinguishing and reduce material damage from fires;
• reduce the risk of the occurrence and development of major fires at potentially hazardous enterprises and facilities (fuel and energy complex enterprises, nuclear power plants and nuclear fuel cycle facilities, chemical and petrochemical enterprises), as well as life support systems facilities;
• implement measures to improve fire protection of subway facilities, transport tunnels and high-rise buildings and structures.

Successful development of the scientific, technological and production base for the creation of new fire extinguishing systems based on domestic high technologies will be a significant contribution to ensuring the security of the Russian Federation, will increase the prestige of the state in the world arena, will ensure the workload and development of a number of domestic high-tech enterprises.

Table 1. Possibility of using technical devices generating jets of finely atomized water for fire extinguishing in the nuclear industry

Literature

1. Website of the State Fire Service of the Ministry of Emergency Situations of Russia. mchs.gov.ru
2. Karpyshev AV, Dushkin AL, Segal M., Stepanchikov VI Highly efficient water mist fire extinguishing systems based on aerospace technologies. Safety issues in emergency situations. Issue 4, Moscow, 2003.
3. Lartsev SG, Paskevich DV Fire safety at nuclear power plants of the Main Directorate of the State Fire Service of the Ministry of Internal Affairs of Russia. Website: “Publications”.
4. Mikeev AK Fire protection of nuclear power plants. Moscow: Energoatomizdat, 1990, 431 p.: ill.
5. Mikeev AK Fires at radiation hazardous facilities. Facts. Conclusions. Recommendations. Moscow, 2000, 346 p.: ill.
6. Fire protection of nuclear power plants. Design standards. NPB 114-2002.
7. Fire safety rules for the operation of nuclear power plants (NPB-AS-95).
8. Nuclear fuel cycle safety. Nuclear Energy Agency. Organization for Economic Cooperation and Development. OECD, 1993.