Fire extinguishers – Processes – Of extinguishing fire
Patent
1996-01-16
1998-12-08
Hoge, Gary C.
Fire extinguishers
Processes
Of extinguishing fire
169 9, 169 11, 169 16, A62C 300
Patent
active
058457143
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method and an installation for fighting fire, in particular for spaces involving risk for fire under a floor structure or in cabinets for electrical apparatuses, and which comprises at least one spray head or sprinkler for spraying a liquid fog.
Spaces in question are e.g. computer rooms with cable channels running under the floor and possibly communicating with different kinds of apparatus cabinets, or ship engine rooms with objects liable to catch fire under the floor in the so-called bilge space.
A serious problem with such spaces is that cable channels, apparatus cabinets etc. are narrow in general and, in addition, have cables, frameworks, pipes etc., whereby difficultly accessible corners are formed. It is very difficult to position spray heads or sprinklers in such a way that the liquid fog has access to all corners; an unproportionally large number of spray heads is required, resulting in an expensive installation, and because of the general narrowness the liquid fog does not come into its own but turns into large water drops which just run down the structures.
It is the object of the invention to provide a new method and a new installation for fighting fire, in order to solve the above problems.
According to the method of the invention, a liquid fog is sprayed in the major part of the space, which major part can be considered as a normal room, while a non-combustible gas, preferably heavier than air, is sprayed into the narrow partial spaces for cables etc. The gas in question can preferably be argon gas, but a suitable mixture of argon gas and nitrogen gas can also be contemplated, or in some cases even nitrogen gas only which is lighter than air. In principle, any gas having some kind of extinguishing effect can be utilized.
The gas is well capable of penetrating into and filling up all narrow spaces and thereby smothering occurring fires. Because those spaces into which gas is sprayed are of small volume in relation to the so-called normal room, into which a liquid fog is sprayed, it is avoided that the total concentration of gas rises to non-allowed high values which may present health hazard. If, e.g. in a telephone central office, argon in combination with a liquid fog is used, the gas is only about 5 % of the total volume, whereat the oxygen content in the room decreases from about 20 % to about 19 %, which is quite harmless.
If argon gas is used as extinguishing gas, the gas collects into a layer down in the space, the gas thus well remaining under the floor and in apparatus cabinets and the like. If, in a room with gas at the floor level, a spray or jet of liquid fog is sprayed down to the floor, the gas is pushed away towards the walls and the corners of the room and is pushed upwards, in particular along the corners right up to upper corner parts of the room whereto the liquid fog has certain difficulties to reach by itself. The liquid fog hereby also tends to push the gas into cabinets standing on the floor and into similar structures into which the liquid fog does not penetrate very easily. The concentration of e.g. argon gas can be chosen to about 10 % of the total volume, lowering the oxygen content from about 20 % to about 18 %, likewise quite harmless. An approximate general rule is that the concentration of argon gas, in order to achieve extinguishing by pushing away (replacing) air oxygen, shall within the partial space in question be 40-50 % of the volume. With this as a basis, the partial space in question may well be about 30 % of the total volume of the action space, whereat the hazard limit applied for a human being, 15 % oxygen of the total volume, is cleared with a safe margin.
Cable fires often generate PVC smoke gases which damage e.g. computer apparatuses. In e.g. computer rooms, the combination of extinguishing gas and liquid fog spray, according to the invention, which creates a suction along the ceiling of the room inwards to the liquid fog spray, has the effect that the gas pushes the smoke gases, including harmful PVC gases, up t
REFERENCES:
patent: 2097908 (1937-11-01), Allen
patent: 2341437 (1944-02-01), Getz
patent: 3548949 (1970-12-01), Groves et al.
patent: 4311198 (1982-01-01), Vasquez
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