RU2458716C1 - Combined method of isolation and extinguishing creeping forest and grassland fires - Google Patents

Abstract

FIELD: fire-fighting means.

SUBSTANCE: method is implemented with the help of pressure hose charge. At a safe distance for operators-fire fighting personnel from the fire-front a reference surveying rod is set. In accordance with the intensity of the fire the flame height is estimated, and the charge is placed behind the surveying rod at a distance Δ in the direction of fire. The distance Δ is determined by the ratio

where: T₁ - is flame temperature, T* - is the temperature of destruction of the charge shell, T₀ is the temperature of the environment, H - is height of the flame, T' - is temperature of the pyrolysis zone. When approaching the edge of the fire to the reference surveying rod the charge is exploded. Certain flame sources are extinguished with a disintegrator.

EFFECT: combined method allows to increase the effectiveness of firefighting and provides safety of operations.

4 dwg

Description

The invention relates to environmental protection, and in particular to methods of extinguishing forest bottom and steppe fires.

A known method of localization of lower forest and steppe fires is that a hose charge is placed on the soil in front of the fire front, then it is blown up and thus a mineralized barrage strip is created [1].

The disadvantage of this method is its use in the "passive" (waiting) mode, since the mineralized strip is created in advance, before the front of the forest or steppe fire arrives. This does not take into account the conditions affecting the spread of the fire. So, an unexpected increase in wind or a change in its direction can, in turn, change the direction of fire propagation, regardless of the location of natural combustible materials (PGM), terrain, and other factors. In addition, the “passive” method of localization contributes to the additional destruction of forest and steppe ecosystems, since a certain amount of PGM is burnt in part of the forest or steppe territory.

Closest to the proposed invention is a combined method of localization and extinguishing using standard overhead hose charges [2].

In this method, a hose charge of explosive (BB) is placed in the immediate vicinity of the fire front, undermining it at the leading edge of the moving front so that the shock wave acts on the pyrolysis zone and detonates it. Due to the sharp increase in pressure (Fig. 1), the flame is broken and the combustion front is destroyed. The remaining small foci of burning and decay are extinguished with water. The method selected for the prototype.

The disadvantage of the prototype method is to undermine the charge directly on the leading edge of the fire front. In this case, the heat from the flame, acting on the material of the shell of the charge, can destroy it and cause an unauthorized explosion of the charge. In this case, the most vulnerable part of the torch — the pyrolysis zone — may be outside the zone of action of the shock wave. Undermining the charge at the edge of the fire front creates the prerequisites for transferring burning particles through the mineralized strip to new sections of the PGM cover, and the fire can continue. In the event of an unauthorized explosion of an explosive charge, there is a threat of defeat for operators who are in the zone of action of the shock wave.

In addition, the extinguishing of the remaining burning foci is usually carried out using knapsack forest fire extinguishers (RLO), the use of which in conditions of forests and steppes is extremely difficult due to the lack of ponds. RLOs are also inefficient and curb weight. For continuous air injection into the tank, the muscular power of the operator is expended, which leads to his physical fatigue. Therefore, the efficiency and safety of fire localization and extinguishing is reduced.

An object of the invention is to increase the efficiency and safety of localization and extinguishing of lower forest and steppe fires.

The problem is solved in that the hose charge is undermined when the combustion front reaches the reference milestone, which is installed in the path of the combustion front, and the charge is placed behind the reference mantle at a distance A, which is determined from the relation

where H is the height of the flame; T ₁ - flame temperature; T 'is the temperature of the pyrolysis zone; T * is the temperature of the destruction of the shell of the charge; T ₀ - ambient temperature. In addition, the remaining combustion sites are extinguished by the disintegrator.

The essence of the method is illustrated by diagrams. Figure 1 shows a graph of the dependence of pressure P on time t in the absence of combustion (solid line) and during the combustion of PGM (dashed line)

Figure 2 shows the layout of the explosive charge when fighting a fire.

Figure 3 shows a diagram of the localization of explosives relative to the pyrolysis zone.

Figure 4 illustrates the extinguishing of the remaining foci of combustion using disintegrators [5].

The numbers indicate: 1 - explosive charge; 2 - flame torch; 3 - cover PGM; 4 - pyrolysis zone; 5 - plot burned PGM; 6 - shock wave; 7 - the remaining foci of flame; 8 - disintegrator.

The method is implemented as follows.

In a forest fire zone, firefighters determine its intensity and classify by type: weak, medium strength, strong [3]. After that, assess the height of the torch and at a safe distance from the fire in front of the front [4] on the ground cover establish a benchmark (figure 2). As a reference branch there can be a pole with a flag. Then, on the ground cover 3, a hose charge 1 is placed at a distance Δ from the pole. The distance Δ is determined in such a way as to prevent the destruction of the material of the shell of the charge from exposure to a heat wave, to prevent unauthorized undermining of the charge and to ensure the effective action of the shock wave on the pyrolysis zone.

Approximately, the distance Δ from the leading edge of the fire to the location of the overhead hose charge is determined from the above ratio. Upon reaching the leading edge of the front of the benchmark, the charge is undermined by an electric detonator. Undermining the charge 1 and the explosion of the pyrolysis zone 4 by the shock wave 6 leads to the disruption of the flame and the destruction of the fire front (figure 3).

The remaining small foci of combustion 7 are extinguished using disintegrators 8 (figure 4).

Thus, in addition to the main features of the prototype method, milestones are installed parallel to the fire front, the height of the flame is determined by the intensity of the fire, then the distance at which the heat wave does not destroy the explosive charge shell material is calculated, where the hose charge is laid. In contrast to the prototype, the extinguishing of the remaining foci of flame 7 after the blasting is performed using disintegrators 8, which form a shock wave capable of knocking down the flame [5].

An example implementation of the method. Upon arrival at the work site, firefighters determine the fire intensity and flame height N. Let us estimate the value of Δ. Let the fire be small, medium strength, strong, then H is respectively 0.5 m; 1.5 m and 2.5 m [4]. It is known that the explosive hose charges have a shell made of nylon or cardboard. For kapron, the flash point is 632 K, and for cardboard, 686 K [6, 7]. From the ratio given above, the distance Δ is determined taking into account the fact that the pyrolysis zone has a temperature of about 753 K [2]. Calculations show that for cardboard Δ can vary within the following limits: for a low ground fire (H = 0.5 m) 0.30≤Δ <0.3 6 m; for a ground fire of medium strength (H = 1.5 m) 0.9≤Δ <1.1 m; for a strong ground fire (H≥2.5 m) 1.5≤Δ <1.8 m. For the nylon shell of the charge, respectively, for H = 0.5 m we get 0.33 m ≤Δ <0.36 m ; for H = 1.5 m 0.98 m ≤Δ <1.1 m and for H≥ = 2.5 m we get 1.62 m ≤Δ <1.8 m.

From the above data it can be seen that for shells made of cardboard or kapron, the safe distances Δ are almost the same. The calculations were performed without taking into account the duration of the heat flux on the shell material.

If we compare the effectiveness of extinguishing, for example, using the well-known device ORP-A [8] and using a disintegrator [5], it should be noted that one operator using ORP-A in 10 minutes can process the edge of the fire up to 30 m long, moreover the curb weight of the ORP-A is 20 kg. Estimates show that with the help of a disintegrator, the operator processes up to 40 m of the edge of the fire in 4.5 min with the weight of the device 4 kg.

It can be seen from the example that this combined method of localization and quenching can be implemented in practice, which indicates the compliance of the invention with the criterion of industrial applicability. The technical result is to increase the efficiency of fire fighting and ensuring the safety of work.

Information sources

1. Kurbatsky N.P., Valendik E.N. Localization of forest fires with overhead cord charges // Questions of forest pyrology. Krasnoyarsk: Publishing House "Krasnoyarsk Worker", 1970. S.320-340.

2. Grishin A.M. Mathematical modeling of forest fires and new ways to deal with them. Novosibirsk: Science. 1994. S.194-197.

3. Grishin A.M. Physics of forest fires. Tomsk: Publishing House Tom. University, 1994.218 s.

4. Vensky S.M., Speransky V.N. Evaluation of the effectiveness of forest fire extinguishers // Forest fires and technical means of dealing with them / Sat. scientific labor. L .: LenNIILKh, issue 19, 1974. 181 p.

5. Grishin A.M., Winter V.P. Certificate PM No. 10582 "Disintegrator of the front of a lower forest fire with a fire extinguishing cartridge." Priority utility model from 02.11.1998. Registered in the register of utility models on 08.16.1998. Bulletin No. 8, 1998.

6. Fire and explosion hazard of substances and materials and their extinguishing agents: Handbook ed. In 2 books, pr. 1 / A.N. Baratov, A.Ya. Korolchenko, G.N. Kravchuk, etc. M .: Chemistry. 1990.496 s.

7. A.E. Zabolotny, M. M. Zabolotnaya, Yu.A. Zabolotnaya, etc. Determination of the safety zone for the use of solid fuel generators of fire-extinguishing aerosols / Vopr. specialist. mash. Iss. 7-8, 1995. S.15-22.

8. Kurbatsky N.P., Krasavina N.N. Extinguishing forest fires with chemicals. L .: TSNIILH. 1954. 22 p.

Claims (1)

A combined method of localization and extinguishing of lower forest and steppe fires, including placing and detonating an overhead hose charge on the path of the combustion front and extinguishing the remaining combustion sites with water, characterized in that the hose charge is undermined when the combustion front reaches the reference weight, which is installed on the path of the combustion front, moreover, the charge is placed behind the benchmark at a distance Δ, which is determined from the ratio

,
where T ₁ - flame temperature;
T * is the temperature of the destruction of the shell of the charge;
T ₀ - ambient temperature;
H - flame height;
T 'is the temperature of the pyrolysis zone,
after which the remaining foci of fire are extinguished by the disintegrator.

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