The present invention relates to a method of and an apparatus for putting out fires under pressure, in particular fires of oil wells and the like.
The main feature of such a system is that of using in combination the extinguishing effect of suitable compositions and the pressure wave directed to the fire so as to dispense instantaneously and homogeneously such compositions on the whole area on fire causing fire to extinguish at once.
Techniques and devices for putting fires out are well known and tested. Generally, difficulties and failures are due to the particular conditions of the fuel (shape and size, pressure in case of a fluid, a.s.o.) rather than to the inefficiency of the used compositions, which extinguishing features in the specific application field are very good.
Putting out a burning oil well, where the favourable circumstance of the limited extension of the burning area is made useless by the particular violence of the fire fed by a pressure liquid with high degree of inflammability, is particularly complex.
Under such conditions putting out systems using extinguishing compositions do not find any application because unlike "extended" fires, (where it is possible to put out fire "progressively" by a continuous, progressive extinguishment of the flames), in case of burning oil wells it is necessary to extinguish fire at once so that the oil continuously fed from the well does not fire any longer.
Methods and means known at the present status of art for putting out burning oil wells envisage the following three different categories of operations:
Such techniques, however, are expensive from the economical and operational point of view.
Therefore, the present invention seeks to solve the problem of easily and economically putting out fires under pressure avoiding the drawbacks involved by the present methods. The object is attained by releasing at once a predetermined amount of an extinguishing composition or mixture of compositions at a suitable pressure and in such a position as to be effective against the fire.
It is known from WO -A-80/01987, a fire extinguisher comprising a container with halogen hydro-carbons as extinguishing means and adapted to open by an inner overpressure, in such a way that the gas generated by heating is released to fill the surrounding room and soffocate the fire.
Unlike the known systems, the present method is based upon the combination of the extinguishing effect of the used compositions and the homogeneous, effective, instant distribution of said compositions over the whole front of the fire because of a shock wave.
This has been achieved according to the invention through the combined use of a composition or a mixture of liquefied compositions having extinguishing and/or inert capability and a container of such compositions having two peculiar operation features:
In practice, both the shape and size of the container may be varied and fitted to the characteristics of the fire to be put out provided that the cone of diffusion formed as a result of the collapse is able to cover the whole front of the fire.
Therefore this invention consists according to claim 1 of a method of putting out fires fed by a pressurised medium having a high degree of inflammability, in particular fires of oil wells, wherein a shock wave is used to dispense an extinguishing composition at once and homogeneously over the whole front of the fire, the method including the use of a container of an extinguishing composition or with a mixture of extinguishing an/or inert compositions alone or in any combination with one another, said container being adapted to collapse at a predetermined break line relative to the shape of the container as a result of the increase of the internal pressure of the contained composition(s) due to the thermal gradient created by the fire to be put out, thereby creating said shock wave, whereby a preferential and effective distribution of said composition(s) over the front of the fire to be put out is obtained thus causing concurrently the fire to be put out.
The invention consists also of an apparatus according to claims 3 and 4 .
Further features and advantages of this invention will be made apparent from the following detailed description with reference to the accompanying drawings illustrating, by way of a non-limitative example, two preferred embodiments. In the drawings:
With reference to Figure 1, the empty container 4 is formed as a hemisphere 8 having walls of thickness d1 and a conical body 6 of thickness d2 overlapped thereto and provided at the top with a hook means 14.
The thicknesses d1 and d2 are designed as a function of the material of which the container is made so that the container collapses under the effect of the increasing pressure generated by the temperature gradient causing the expansion of the compositions contained therein and it releases at once and at a predetermined pressure the extinguishing mixture which is conveyed to the whole front of the fire.
The container may be formed of any material provided that it is uninflammable. By way of example, containers of aluminum and alloys thereof, copper and bronze have been used in the experimental tests.
The loading of the compositions to be used is carried out through common sealing input means 10 and 12 which are usually provided under safety conditions.
All of the extinguishing compositions alone or in combination with one another and with inerts may be used. The best results have been achieved by the use of compositions having a very low boiling point, i.e. under liquefied form. Among the latter there are the halogen derivatives of methane and ethane, in particular C₂F₅Cl, CHClF₂, CCl₂F₂, CHF₃, used alone or in combination with one another, at varying relative proportions and with or without liquid nitrogen which besides the extinguishing characteristic has also a propellant effect causing a more effective diffusion of the used compositions.
Also the effectiveness of liquid nitrogen or other inert gas with high expansion capacity alone or in combination with said compositions has been tested.
The putting out method according to the present invention is extremely easy and immediate: after having partially filled the container with the composition or mixture of extinguishing compositions, the sealed container is suitably placed over the fire by any known means. As a result of the high thermal gradient the inner pressure of the container is quickly increased, and when the value determined by the characteristics of the material and by the thickness of the thinner walls is reached, the container collapses and spreads vapours of the contained compositions under pressure onto the fire through the broken sheet. As illustrated in fig. 1, the collapse occurs at the lower portion of the container as the walls of the hemishere have a lower thickness than that of the overlapped conical body. This upper part of the container above the predetermined break line remains integral after the collapse of the container and prevents the vapours from dissipating upwards so that said vapours are conveyed downwards to attack the flames and put fire out.
In order to avoid that parts of the broken sheet are thrown all around the place of operation, it is useful to put said apparatus into a cage made of any material having a mesh pattern resistant to the operating conditions.
An alternate embodiment of the device of the invention is shown in Figure 2. In such case the container has a spherical geometry without prejudice to the difference in the thicknesses d1 and d2 of the two hemispheres 8 and 8a, respectively, and has a predetermined break line at the section of largest diameter.