Fire extinguishers – Processes – With mixing of extinguishing compounds
Reexamination Certificate
1998-09-30
2001-01-16
Kashnikow, Andres (Department: 3752)
Fire extinguishers
Processes
With mixing of extinguishing compounds
C169S015000, C169S060000, C169S046000, C239S310000, C239S398000
Reexamination Certificate
active
06173790
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process and a device for mixing liquid inert gas with a liquid extinguishing medium (e.g., water) and for subsequent atomization of the mixture for the purpose of fire fighting. The present invention is suitable for stationary, and mobile, fire extinguisher units.
2. Description of the Related Art
Usually, sprinkler, foam, water spray and gas extinguisher units are used for extinguishing fires.
These extinguisher units have disadvantages for particular applications. For example, a great deal of water is used in sprinkler and water spray extinguisher units. This can lead to considerable damage. Moreover, large supplies of water and machine outputs must be installed. Foam extinguisher units entail increased technical expense, and this leads to high installation costs. High costs for disposal are also incurred. Gas extinguisher units, which work, for example, by lowering the oxygen concentration by means of inertization in the extinguishing area, require considerable safety expenditure, particularly in the case of CO
2
extinguisher units, due to the danger to personnel. Certain other extinguishing gases that were previously used, e.g., halon, can no longer be used due to legal restrictions. Other extinguishing mediums, e.g., argon, are relatively expensive.
Reference WO95/24274 discloses a process and a device for atomizing liquid extinguishing medium with a feed for extinguishing medium, a distributing device for gas, a reservoir and a mixing unit. The referenced process functions with a plug flow, which does not assume a pulsing character until the nozzle exit. Moreover, at the mixing unit, the two media have the same pressure, because the gaseous medium from the container is used as a propellant for the extinguishing medium. The use of liquid inert gas is not described.
SUMMARY OF THE PRESENT INVENTION
An object of the present invention is to reduce, particularly in a stationary water spray extinguisher unit, the amount of liquid extinguishing medium, as commonly used in a conventional extinguisher units, needed to extinguish a fire.
This object is attained by adding an inert gas in liquid form to the liquid extinguishing medium upstream of a nozzle producing a liquid extinguishing medium mixture. Here, the term “inert gas” does not refer to an aggregate state at the time of addition to the liquid extinguishing medium; rather, the inert gas is preferably added as a liquid to the liquid extinguishing medium.
The addition of the liquid inert gas can be carried either by mixing in the liquid inert gas at an increased pressure relative the liquid extinguishing medium, or by adding the liquid extinguishing medium at an increased pressure relative to the liquid inert gas.
The liquid extinguishing medium typically water, is usually conducted in a conduit network at a pressure of 8-10 bar, regardless of the water source, e.g., municipal water network, water tanks, etc.
Advantageously, the liquid inert gas is fed to the conduit network at a higher pressure. This leads, in conjunction with suitable mixing devices and devices for controlling the pressure in the conduit network (e.g., non-return valves, blocking valves, media control valves), to an increase in pressure at a device for distributing the liquid extinguishing medium mixture, e.g., the nozzle. Typically, the distributing device includes several nozzles.
As a result of the increased pressure, at the nozzles, there is an increase not only in the water exit velocity, but also in the droplet distribution and the range.
Droplet size and the range are influenced by means of different nozzles. Specifically, ranges of up to 10 m can be attained.
Preferably, the liquid inert gases and CO
2
, the liquid extinguishing medium, is water.
It should be noted that a two-phase bubble flow is produced by the inventive process, in that more inert gas is added than can go into solution. This two-phase bubble flow in the tubular conduit system in a simple fashion produces at the nozzle an aerosol with optimal droplet size for fire fighting.
One advantage of the present invention is that the liquid inert gas largely dissolves in the liquid extinguishing medium under high pressure and is conveyed to the fire by means of the produced droplets, since a dynamic process of degasification takes longer than the transport time. This improves the extinguishing effect, because the droplets split again en route to the fire. Advantageously, the fire is better extinguished with the very fine water mist that is produced.
Although the physical-chemical processes are not yet fully understood, it has been determined that, due to the process according to the invention, the flame is separated from a combustible gas by the kinetic energy of the liquid extinguishing medium and by the degasification of the inert gas at the location of the fire.
As a result of the formation of micro-droplets in the area of the fire, particularly due to the separation of the liquid extinguishing medium and the inert gas, the surface of the liquid extinguishing medium is considerably enlarged. In addition, the inert gas (e.g., CO
2
) absorbs radiated energy, and vaporization of the liquid extinguishing medium removes energy from the fire. In this way, energy surplus in an area of the fire is reduced so far that a high extinguishing effect, which could not be attained solely by the use of micro-droplets without the mixing in of preferably liquid inert gas, is attained.
The amount of inert gas added is optimized. When CO
2
is used, as preferred, optimization can be carried out during projecting, in that a maximum quantity of CO
2
relative to the object being extinguished is determined.
It is preferable, however, to control the amount of the inert gas, in particular, the liquid inert gas, e.g., CO
2
, added in dependence on a concentration of the inert gas in the extinguishing area during the extinguishing, so that a maximum MAK value of 10,000 ppm or the maximum value usual in inergenic extinguisher units (<4% by volume) is not exceeded.
According to a further preferred process, the amount of liquid inert gas added is also controlled based on the course of the fire.
The object is further attained by means of a device according to the invention, which, includes the supply for the liquid extinguishing medium and the distributing devices for the liquid extinguishing medium, mixture. The device has a reservoir for the liquid inert gas and a mixing unit for mixing the liquid extinguishing medium and the liquid inert gas. This special mixing unit is preferably mounted horizontally or vertically upstream of the nozzles in the tubular conduit network.
Preferably, the device is connected to a detector to determine the concentration of the inert gas in the extinguishing area. The detector is connected to an evaluation device, which is connected to a control device to control the amount of the liquid inert gas.
Also preferred is a device wherein a detector is arranged to determine the course of the fire.
In another embodiment, this detector forms a unit with the detector that determines the concentration of the inert gas in the extinguishing area. The unit is embodied, in particular, as a combined measurement device for electro-magnetic radiation as well as on the principle of smoke alarms and heat alarms.
In a further preferred embodiment of the present invention opening angles of the distributing devices for the liquid extinguishing medium mixture are adjustable, whereby the opening angles are determined by the quantity of mixed-in liquid inert gas. The process and device according to the invention are described in greater detail in reference to a schematic drawing of an example.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by it uses, reference should be had to the drawing and descriptive m
Aebischer Frederic
Russwurm Manfred
Cohen & Pontani, Lieberman & Pavane
Ganey Steven J.
Kashnikow Andres
Minimax GmbH
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