Method and device for suppressing an explosion-like fire, in par

Details Method and device for suppressing an explosion-like fire, in par Method and device for suppressing an explosion-like fire, in par

1997-04-18

1999-05-04

Anthony, Joseph D.

Fire extinguishers

Processes

Of extinguishing fire

169 47, 169 45, 169 56, 169 60, 169 33, A62C 3500, A62C 3564, A62C 3568

Patent

active

058992774

DESCRIPTION:

BRIEF SUMMARY
This invention relates to a method of suppressing an explosion-like fire, in particular of hydrocarbons, by means of a fire extinguishing agent which under pressure and with a speed adapted to the speed of propagation of the fire is distributed in the space directly surrounding the source of the fire, and to a device for carrying out such method.
For suppressing explosion-like fires, in particular in vehicles with internal combustion engines, it is known to use carbon halides, which with a speed adapted to the speed of propagation of explosion-like gasoline or oil fires are distributed in the space directly surrounding the source of the fire to be expected. This distribution of the fire extinguishing agent in fractions of a second is achieved by pyrotechnically opening a correspondingly pressurized pressure vessel, from which the carbon halide being used is discharged in the space to be protected under the acting pressure of the vessel. Due to an anticatalytic effect this carbon halide prevents an oxidation which would be sufficient for the propagation of the fire, without expelling the oxygen from the space to be protected to an extent that endangers a survival in this space. What is, however, disadvantageous in the use of such carbon halides is their adverse effect on the environment. In addition, the cooling of the source of the fire achieved in connection with carbon halides is comparatively poor.
It is therefore the object underlying the invention to improve a method of suppressing explosion-like fires, in particular of hydrocarbons, as described above such that a very efficient suppression of the fire can be ensured with an environmentally beneficial fire extinguishing agent.
This object is solved by the invention in that as fire extinguishing agent water possibly mixed with additives is distributed in a minimum amount of 0.03 l/m.sup.3 in the space directly surrounding the source of the fire by atomizing it to form a water mist.
The use of water or water mist for fighting a fire is of course known, but not for fighting hydrocarbon fires, where the use of water as fire extinguishing agent was avoided by all means. However, it was surprisingly found out that explosion-like fires of hydrocarbons can also be suppressed very efficiently by means of a water mist, when the water mist from an amount of water of at least 0.03 l /m.sup.3 is sprayed in the space directly surrounding the source of the fire. The use of water in the form of a water mist leads to a very large surface of the water droplets as compared to the amount of water used, so that this amount of water evaporates very quickly by taking up a corresponding heat of evaporation, which for fighting the fire involves a very advantageous cooling of the source of the fire, from which this heat of evaporation is withdrawn. This evaporation-related transition from the liquid to the gaseous state of the water droplets is in addition connected with a very large increase in volume (factor 1600), with the effect that the air and thus the oxygen in the direct vicinity of the source of the fire is expelled by the steam produced, which prevents the oxidation required for a propagation of the fire. This expulsion of oxygen must be sufficient, which with the given changes in volume in the transition from the liquid to the gaseous state requires a certain amount of water per unit volume. The droplet size of the water mist does not play a decisive role, as it can be assumed that in a water mist the water droplets do not exceed a certain average size of about 400 .mu.m, and that with this maximum droplet size the varying rate of evaporation as a result of varying droplet sizes has no decisive influence on the expulsion of oxygen.
What is, however, of major importance in the use of water mist for the suppression of explosion-like fires is the evaporation of the water droplets controlled by the fire itself, which occurs to an increased extent wherever there is an increased evolution of heat. As a result of the increased evaporation of the water mist with the increas

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