US2853139A - Methods of fighting fires - Google Patents

Description

Sept. 23, 1958 G BIRO METHODS OF FIGHTING FIRES Filed Feb. 3, 1955 Mm u Gun-mums B|Ro B). F MW w.

United States Patent G METHODS OF FIGHTING FIRES Guillaume Biro, Chaville, France Application February 3, 1955, Serial No. 485,959

Claims priority, application France February 5, 1954 Claims. (Cl. 169-1) A known method of fighting fires consists in projecting on the seat of the fire an incombustible or fire-extinguishing product to form a layer of pulverulent product adapted to isolate this seat from the combustion air. However, this method is not satisfactory in all cases. In fact, the desired result may be obtained only provided that the whole of the seat of a fire be covered with a layer of pulverulent product. As long as this requirement is not met, the uncovered portions of the seat of the fire will continue to burn and emit volatile gases to feed the fire. In all cases, the method in question does neither provide any cooling of the material on fire nor reduce the temperature in the vicinity of the seat of the fire, so that it is practically impossible to come near thereto.

Another known method of fighting fires consists in projecting onto the seat of the fire carbon dioxide snow" obtained by causing a charge of carbon dioxide gas under pressure to expand suddenly, this projection being effected by using a nozzle. The carbon dioxide snow, due to its very low temperature (70 F., for example) will cause the temperature to drop very strongly in close vicinity of the seat of the fire, so as to cool completely the material on fire and replace the combustion air with an inert gas, in this case carbon dioxide released from the carbon dioxide snow subsequent to its projection onto the seat of the fire. However, this method is not completely satisfactory because it is attended by at least three major inconveniences:

(a) The range of the jet of carbon dioxide snow is necessarily relatively short because the strong expansion of carbon dioxide gas which is required for freezing this gas and forming the carbonic snow will obviously destroy the initial velocity of the carbon dioxide gas under pressure. Besides, the very nature and consistency of the carbon dioxide snow make it impossible to obtain a long-range jet;

(b) One portion of the carbon dioxide snow evaporates in the atmosphere as it leaves the projection nozzle. In fact, the carbon dioxide snow particles positioned peripherally of the jet issuing from the nozzle are subjected to a strong heating action by the surrounding atmosphere and by the fire proper, so that these particles evaporate and one portion only of the projected carbon dioxide snow will actually reach the seat of the fire. The loss thus experienced is rather heavy and increases with the distance between the nozzle and the seat of the fire. Now, if the latter is of considerable importance, it is hardly possible to come near thereto and as the projection of fire-extinguishing product is effected from a relatively great distance the loss of carbon dioxide snow is very heavy;

(c) Due to the enormous heat usually released by the seat of a fire, even the carbon dioxide snow actually spread over this seat is partly evaporated. Consequently, a substantial quantity of carbon dioxide snow must be projected within a very short time to prevent the heat developed by the fire from evaporating the whole of the carbon dioxide snow, so that a minimum quantity thereof will remain to isolate the seat of the fire from the combustion air.

As will be seen from the foregoing, the drawbacks characterizing the two methods mentioned hereinabove are very important although both of them offer undeniable advantages. Nevertheless, in both cases the benefit arising from these advantages is destroyed by the drawbacks.

It is the essential scope of this invention to provide a novel method of fighting fires which combines the advantages of both prior art methods broadly set forth hereinabove without offering the inconveniences of these former methods.

In fact, this method consists in projecting onto the seat of a fire a pulverulent incombustible or fire-extinguishing product, particles of which are coated with a layer of frozen carbon dioxide gas. This projection of pulverulent material having its particles coated with frozen carbon dioxide gas is effected with a view to obtain simultane= ously:

A strong temperature drop in the vicinity of the seat of the fire, due to the action exerted by the frozen carbon dioxide gas; 5

A complete cooling of the material on fire, also by the action exerted by the frozen carbon dioxide gas;

The replacement of the combustion air with an inert gas, in this case the carbon dioxide gas released from the coating of the particles subsequently to their projection on the fire seat;

The formation, on the seat of the fire, of a layer of incombustible pulverulent product to isolate this seat from the combustion air.

It has been observed that the projection of a pulverulent product having its particles coated with frozen carbon dioxide gas makes it possible to meet all of these requirements. The effect produced by this projection on a. fire is therefore much better than that of the projection of an ordinary pulverulent material.

It is another object of this invention to provide a method of carrying out the method just described. This other method consists in feeding a pulverulent product to a projection nozzle and causing carbon dioxide gas under pressure to expand very suddenly within this nozzle, by employing a suitable jet orifice opening into this nozzle, so that the strong reduction in the gas temperature which results from its expansion will cause the gas to freeze around the particles of the pulverulent product. Thus, these particles, before issuing from the nozzle, will be coated with a layer of frozen carbon dioxide gas.

It is pointed out that this freezing of the carbon dioxide gas on the surface of the particles of pulverulent product does not occur immediately as this gas issues from its expansion jet orifice. In fact, as the gaseous flow impinges against the particles of pulverulent product the freezing action is retarded, but this delay has a very advantageous consequence in that it makes it possible for the carbon dioxide gas firstly to exert a strong dynamic thrust on the particles of pulverulent product, and subsequently to effectively freeze around the particles. Of course, the jet orifice through which the carbon dioxide gas is expanded will preferably be directed in the nozzle toward the outlet of this nozzle.

From the foregoing, it will be readily understood that in addition to the advantages already listed hereinabove in connection with the prior art methods, other, very important features are obtained which may be described as follows:

(1) The projection jet is a long-range one, due to the dynamic thrust exerted by the carbon dioxide gas on the particles of pulverulent product, the complete expansion and the freezing of this gas being retarded Patented Sept. 23, 1958 by its impact against the particles of pulverulent product. This range is much greater as the material projected through the nozzle outlet is not carbon dioxide snow but consists of particles of pulverulent product acting somewhat as a support for frozen carbon dioxide gas. In fact, these particles are much more liable to be thrown at a relatively very high initial speed and to maintain this speed;

(2) If the coating of frozen carbon dioxide gas covering the particles of pulverulent product which are positioned in the peripheral region of the jet issuing from the nozzle is partly evaporated owing to the heat released by the fire and to the action of the surrounding atmosphere, the particles of the pulverulent product itself are not affected and will reach the seat of the fire unaltered. Besides, the evaporation of frozen carbon dioxide gas is much less important than in the case of carbonic snow projected separately. In fact, the frozen carbon dioxide carried by a solid support, in this case the particles of pulverulent product, will evaporate to a considerably lesser extent than free carbon dioxide snow, i. e. carbon dioxide snow without any solid support, the thermal transfer occurring at a much slower rate in the case of a solid substance;

(3) If the importance of the seat of the fire is such that the major portion of the frozen carbon dioxide gas evaporates after the particles have reached the seat of the fire, the particles of pulverulent product will remain on this fire to form a layer adapted to isolate it completely from the surrounding combustion air, as the seat of the fire has been cooled from the very beginning of the projection by the frozen dioxide gas;

(4) The total quantity of material projected is considerably greater with the method of this invention than in those cases where carbon dioxide snow alone is projected.

A suitable device for carrying out the two methods broadly set forth hereinabove comprises essentially a relatively large-sized tubular nozzle connected at one end to a duct for supplying a pulverulent product and a jet for expanding compressed carbon dioxide gas, this jet being preferably directed toward the nozzle outlet.

Other features and advantages of this invention will appear as the following description proceeds with the methods according to this invention with reference to two embodiments of a device. These methods are described by way of example with reference to the attached drawing showing very diagrammatically:

In Fig. 1, a nozzle shown in part-sectional elevation, and in Fig. 2, a modified embodiment also shown in partsectional elevation.

The device illustrated in Fig. 1 consists essentially of a nozzle member 1 properly of relatively substantial diameter; at an inlet end 2 of the nozzle which is opposite to the outlet aperture 3 thereof are provided on the one hand a duct 4 for supplying the nozzle with pulverulent product 6 and a jet for ensuring the expansion of compressed carbon dioxide gas. The duct 4 and jet 5 are conveniently directed toward the front or outlet aperture 3 of the nozzle.

The device illustrated in Fig. 2 differs from that of Fig. 1 only in that the end or outlet portion of the jet 5' for expanding the carbon dioxide gas is disposed coaxially to the duct 4 through which the pulverulent product is fed to the nozzle.

Of course, both devices illustrated in the drawing comprise means (not shown) for controlling the inlets of the duct 4 and jet 5. The duct 4 obviously communicates with a container filled with pulverulent product. This container may be positioned in close proximity of the nozzle 1, and in this case the pulverulent product will flow by gravity to the nozzle. However, this container may also be positioned remotely from the nozzle 1; in this case the pulverulent product will be subjected to a gas pressure, the latter being just suflicient to ensure 4 the transfer of pulverulent product from the container to the nozzle 1.

Regarding the jet 5, it communicates with a cylinder containing carbon dioxide gas compressed to about 700 lbs/p. s. i. at 60 F.; more particularly, the carbon dioxide gas is contained in its liquefied state in this cylinder. The carbon dioxide gas is brought in this liquefied state to the outlet end of the jet 5. The cross-sectional area of this jet is relatively small and that of the nozzle 1 relatively large; for example, the jet size may be about 4 millimeters and the nozzle inner diameter may be about 58 millimeters. Thus, a strong expansion of the carbon dioxide gas takes place as it flows from the jet 5 to the chamber constituted by the nozzle 1. This expansion is such that 1.4 litres of liquefied carbon dioxide in the jet 5 corresponds to about 500 litres of gaseous carbon dioxide in the nozzle 1.

This strong expansion causes a considerable drop in the carbon dioxide gas temperature as the latter may fall as low as 70 F. This temperature drop tends to freeze the carbon dioxide gas. However, this freezing does not occur immediately upon the discharge of carbon dioxide gas from the jet 5. In fact, due to the impact produced between the gaseous stream and the particles of pulverulent product issuing from the duct 4, the carbon dioxide gas will freeze only at a certain distance away from the jet 5. In the rearmost portion of the nozzle 1 the pulverulent product meets the carbon dioxide gas flow and the former is thoroughly stirred by the latter. This stirring action ensures a uniform distribution of the solid particles in the gaseous stream. Moreover, due to the violent gas expansion produced in the nozzle the carbon dioxide gas will impress to the particles of pulverulent product a substantial acceleration and these particles are thus ejected with a high impetus from the nozzle 1 in the form of a long-range jet.

The freezing of the carbon dioxide which results from the substantial temperature drop produced by the powerful expansion taking place in the nozzle 1 occurs actually at a certain distance from the outlet of the carbon dioxide gas expansion nozzle. Yet, this carbon dioxide gas freezing is effective around particles of pulverulent product, i. e. the carbon dioxide gas coats particles with a layer of frozen carbon dioxide gas. Elaborate tests have proved that this freezing takes place on particles of pulverulent product due to the perfect diffusion of the latter in the nozzle chamber.

Therefore, the pulverulent product ejected through the outlet aperture 3 of the nozzle 1 has particles coated with a layer of frozen carbon dioxide gas. Thus, the seat of a fire may be efiiciently spread with a pulverulent product of which particles are coated with a layer of frozen carbon dioxide gas, the particles of pulverulent product acting as a supporting material to the frozen carbon dioxide gas, so that the projection jet may have a relatively long range. In fact, due to its inherent character, carbon dioxide gas if used separately, i. e. without any support, cannot possess a substantial kinetic energy. With the method of this invention, on the contrary, the frozen carbon dioxide gas may have a considerable kinetic energy since it is carried by a solid support consisting of the particles of pulverulent product of which the initial speed is imparted by the carbon dioxide gas under pressure.

This novel method of fighting fires is attended by many substantial advantages with respect to prior art or conventional methods of projecting an ordinary pulverulent product, and also with respect to methods whereby car bon dioxide snow alone is projected. The method of this invention meets all the requirements set forth hereinabove and is furthermore characterized by the advantages indicated in the foregoing.

Consequently, this novel method of fighting fires is quite remarkable.

Of course, many detail modifications and alterations may be brought to the method employed for carrying out the fire-fighting method disclosed hereinabove, i. e. the method of forming a frozen layer of carbon dioxide gas on the particles of a pulverulent product intended to be projected onto the seat of a fire, without however departing from the spirit and scope of the invention.

What I claim as new is:

1. A flame extinguishing method comprising the steps of coating particles of a pulverulent non-combustible material with frozen carbon dioxide, and projecting a stream of the thus-coated particles into the flame to be extinguished.

2. In a flame extinguishing method, the step of simultaneously introducing into an expansion chamber particles of a pulverulent non-combustible material and carbon dioxide under such pressure that upon entry into said expansion chamber the carbon dioxide expands and cools to a temperature at which it solidifies, thereby coating the particles.

3. A flame extinguishing method comprising the steps of expanding carbon dioxide under pressure, in the presence of particles of a pulverulent non-combustible material, to such an extent that the carbon dioxide freezes and coats the particles; and projecting a stream of the thus coated particles into the flame to be extinguished.

4. A flame extinguishing method comprising the steps of introducing particles of a pulverulent non-combustible material into an expansion chamber; simultaneously introducing into said expansion chamber a jet of carbon dioxide under such pressure that upon entry into said expansion chamber the carbon dioxide expands and cools to a temperature at which it solidifies, thereby coating the particles, whereby a stream of coated particles may be expelled through an orifice of said expansion chamber which is in alignment with the jet of carbon dioxide.-

5. The method defined in claim 4 wherein the pulverulent material and the jet of carbon dioxide are introduced into said expansion chamber through respective inlets which are located near each other.

References Cited in the file of this patent UNITED STATES PATENTS 1,148,763 Fagan Aug. 3, 1915 1,771,151 Treichel July 22, 1930 2,441,700 Hammell May 18, 1948

Claims (1)

1. A FLAME EXTINGUISHING METHOD COMPRISING THE STEPS OF COATING PARTICLES OF A PULVERULENT NON-COMBUSTIBLE MATERIAL WITH FROZEN CARBON DIOXIDE, AND PROJECTING A STREAM OF THE THUS-COATED PARTICLES INTO THE FLAME TO BE EXTINGUISHED.

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