Fire extinguishers – Fluid systems – Gas-pressure discharge
Patent
1995-04-19
1997-10-14
Hoge, Gary C.
Fire extinguishers
Fluid systems
Gas-pressure discharge
169 71, A62C 3502
Patent
active
056762100
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method and an installation for fighting fire.
A problem with fighting a fire in a room by means of a preferably automatically releasable installation for fighting fire is that the main fire seat, and secondary fire seats and smaller fires in general as well, may not be totally extinguished but can remain smouldering.
Difficult smouldering fires are in particular fires in the upper region of a room where the walls meet the ceiling, e.g. cable fires.
The object of the invention is to provide a new method and a new installation for fighting fire, including difficult smouldering fires.
The method according to the invention is mainly characterized in that the fire is initially, in a first step, fought by means of at least one fog-like liquid spray having comparatively large droplets and a good penetration power, in order to at least suppress the fire, and thereafter, in a second step, the initially utilized fog-like liquid spray is scattered, by mixing a pressurized non-combustible gas into the liquid, to form a turbulent liquid fog for filling the fire room at least essentially evenly and for extinguishing smouldering fire seats.
By a fog-like spray is meant a spray of small droplets having a diameter typically 30 to 150 microns and preferably set in a strong whirling motion. As earlier mentioned, by a high charge pressure is here in general meant from about 30 bar up to about 300 bar, as compared to an operating pressure of generally 2 to 10 bar in conventional sprinkler installations which produce a rain-like spray. It shall be noted, however, that the values given above are not absolute; definite limiting values are difficult to present.
Large fires are extinguished or are at least suppressed to a great extent by the effect of steam generation; the steam prevents oxygen from entering into the fire and the generation of steam binds large amounts of heat. For smaller fires and smouldering fires it is essential that the air sucked into the fire seat shall have a liquid content sufficient for cooling.
Preferably the initially utilized fog-like liquid spray is scattered by intermixing therein such a gas which is lighter than air, preferably nitrogen, so that the intermixed gas, preferably drive gas from at least one hydraulic high pressure accumulator, rises and brings liquid droplets to the ceiling of the room, in order to ensure that fire seats in the upper regions of a room are extinguished by the combined effect of the gas itself and of the liquid droplets following with the gas.
When nitrogen gas accumulates up under the ceiling, together with small droplets which due to the turbulence remain airborne for a comparatively long time, e.g. smouldering cable fires and the like at the ceiling level are effectively smothered.
By successively, or step-wise, increasing the amount of intermixed gas in relation to the liquid, accordingly smaller droplets are obtained, with a prolonged airborne time in spite of a gradually decreasing turbulence.
If there is reason to assume that a somewhat greater concentration in the lower region of the room would be of advantage in the final stage of the extinguishing process, e.g. argon gas can be used as intermixing gas.
A preferred embodiment of the installation according to the invention comprises
at least one spray head capable of producing a fog-like liquid spray at a high operating pressure and having a good penetration power,
a drive unit with at least one hydraulic accumulator chargeable to a high initial drive pressure,
the liquid being arranged to be driven out through a tube which starts at the bottom portion of the liquid space of the accumulator and extends through the gas space of the accumulator to the outlet thereof, and
said tube having at least one aperture in its wall, at a predetermined distance from the outlet end of the tube and with a predetermined diameter, so that drive gas flows into the tube through said at least one aperture in the wall, when the liquid level in the hydraulic accumulator has reached said aperture,
in or
REFERENCES:
patent: 4069873 (1978-01-01), McClure
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