US2143311A

US2143311A - Method of fire extinguishing

Info

Publication number: US2143311A
Authority: US
Publication date: 1939-01-10
Anticipated expiration: 1956-01-10

Description

Jan. 10, 1939. E. GEERTZ 2,143,311

METHOD OF FIRE EXTINGUISHING Filed May 20, 1938 jjwuam fon t I 'ji f v 5520 Geerlz 54 I B cumw liquid. If

Patented Jan. 10, 1939 UNITED STATES PATENT OFFICE 2,143,311 METHOD OF FIRE EXTINGUISHING Application May 20, 1938, Serial No. 209.151'

9 Claims.

This invention relates to new and uselul improvements in a method of employing and making available for use liquid carbon dioxide as a fire extinguishing medium.

Carbon dioxide is commonly used at the present time as a fire extinguishing medium. When it is essential to have available for use large quantities carbon dioxide, the prevailing practice is to store the liquid carbon dioxide in comparatively small cylinders or drums which are arranged and interconnected to form a bank or battery. The carbon dioxide is discharged from the top of the several cylinders in the form of gas. The temperature of the carbon dioxide is permitted to vary in accordance with variations in the temperature 0! the surrounding atmosphere and, for that reason, the cylinders must be constructed to withstand high working pressures. Due to this lack of control of the temperature and pressure of the stored carbon dioxide, it has not been allowable to fill the internal volume of the cylinders with more than 68% of liquid. The container weight and cost per pound of capacity, therefore, is very high.

The effectiveness of carbon dioxide as a fire extinguishing medium. or course, depends on its ability to smother the fire by excluding oxygen. Carbon dioxide gas, although heavier than air, is seriously affected by the currents of heated air which rise from the fire and for that reason, the hotter the fire, the less efiective or efficient carbon dioxide gas is as an extinguishing medium. The discharge of carbon dioxide gas from the battery of cylinders will bring about evaporation of additional liquid in the cylinders. This vaporization of liquid carbon dioxide in the cylinders will result in refrigerating the remaining the discharge or gas continues for a sufllcient length of time, the temperature of the remaining carbon dioxide liquid will be lowered to -70 F., the temperature at which the liquid carbon dioxide will solidity, and further discharge of the extinguishing medium will cease. This solidification of the remaining liquid carbon dioxide will occur as a result of continuous or substantially continuous discharge 01' approximately three quarters of the original quantity of liquid.

Therefore, in addition to being unable to fill the entire internal volume of the cylinders with liquid carbon dioxide, approximately one quarter of the liquid which is stored in the cylinders is not available for use it the fire being extinguished is of a character to require discharge of more than three quarters of the original quantity.

The primary object of this invention is to provide a method of making carbondioxide available for use as a fire extinguishing medium without encountering the defects and disadvantages inherent in present day methods.

A further important object of the invention is to provide a method of employing and making available for use at a low storage cost, large quantities or liquid carbon dioxide at controlled constant sub-atmospheric temperatures and corresponding low vapor pressures.

A still further object of the invention is to provide a method of employing liquid carbon dioxide as a fire extinguishing medium in which the liquid is conditioned so as to produce a much higher percentage of yield of snow when discharged to the atmosphere than is possible with methods and apparatus now in common use.

Another object of the invention is to provide a method of employing carbon dioxide as a fire extinguishing medium wherein a larger quantity by weight of carbon dioxide per unit or container volume and weight is provided than has been possible heretofore.

Still another object of the invention is to provide a fire extinguishing medium which is especially effective in combating gasoline, oil, wood, electrical and coal mine fires; which is especially effective in preventing the occurrence of re-fiash in any type of fire, and which will enable fire fighters to more closely approach extremely hot fires.

Other objects and advantages or the invention will be apparent during the course of the following description.

In the accompanying drawing forming a part of this specification and in which like numerals are employed to designate like parts throughout the same,

The figure diagrammaticallyillustrates the fire extinguishing apparatus embodying this invention and its method of use to extinguish diflerent types or kinds of hostile fires.

In the drawing. wherein for the purpose of illustration are shown the preferred embodiments of this invention, the reference character 5 designates a building which is intended to be representative of all types and styles of building in which fire hazards may exist: for example, private residences, apartment houses. ofilce buildings, garages, service and repair shops, manufacturing plants, etc. Within this building 5, there is illustrated a room or confined space ll which the owner or occupant desires to protect from a hostile fire by means of a. sprinkling system 1,

with its discharge nozzles 8. or by means of an ambulant discharge which may take the form of a flexible hose 9 with a suitable discharge noz zle l0. Within the building 5. there also is illustrated an object II which may take the form of any stationary or substantially stationary piece of equipment or apparatus which can be protected by a non-ambulant discharge device l2 which may assume any desired and efllcient form for accomplishing the intended results.

Exteriorly of the build ng 5. there is illustrated a storage pile i3 which may be formed of any combustible material, such as coal, wood, grain, or the like. This storage pile i3 may be protected from flre hazards by means of a nonambulant system of discharge nozzles I4 associated with a supply line I5 or by means of an ambulant discharge device which may take the form of the long perforated pipe I6 which is connected to a flexible supply conduit l1.

While the objects designated by the reference characters 5, 6, ii and iii are representative of all different types of objects or things which should be protected from fire hazards, it is to be understood that the use of this fire extinguishing system and method is not in any way to be limited to the protection of objects and things of the character which has been illustrated, but is applicable to all objects and things which require fire protection. It is to be understood, also, that this system and method is not to be limited to the particular forms of discharge devices which have been diagrammatically illustrated.

Properly located with respect to the various sources of hostile fires is a heavily insulated container Iii of large capacity. This container unit may consist of one tank or a series of tanks enclosed in a single heat insulating shell. The container unit l8 preferably should have a capacity of several hundred pounds of liquid carbon dioxide, and may contain several tens of the liquid, depending upon the character of the hazard to be protected. Of course, where the system is employed to protect large apartment houses, ofllce buildings, or a factory, it may be necessary to provide two or more of the container units In. It is to be considered that such an expansion of the illustrated system falls within the scope of the invention. This container unit is should be designed to withstand a working pressure of approximately 500 pounds per square inch, or, inore specifically, the vapor pressure at 32 R, which is 505 pounds per square inch absolute. Of course. container units capable of withstanding a higher work ng pressure may be employed, but as the ability to withstand greater internal pressures is not essential or desirable, the use of container units adapted to withstand working pressures appreciably in excess of 500 pounds per square inch will materially add to the initial cost of the installation and will thereby eliminate from or deprive the system of one of its most valuable features.

Properly communicating with the lower portion of the container unit i8 is a pipe line I! which extends to a readily accessible location and is provided at its extremity with a coupling 2|) by means of which a transportable container, such as a railway tank car or road tank vehicle, may be connected to the said unit. The railway tank car or road vehicle is intended to transport from a suitable source of supply to the location of the coupling 20, liquid carbon dioxide mainta ned at a desired subatmospheric temperature, not to exceed 32 F., at the corresponding vapor pressure. This low temperature liquid carbon dioxide is charged by any suitable method or means into the storage container unit l8. By transporting the liquid carbon dioxide at this low temperature and vapor pressure, a great reduction in the weight of the transport container per ton of capacity may be provided, with the result that handling costs are considerably lower than can be obtained when the carbon dioxide is transported at the fluctuating temperatures and corresponding vapor pressures which would result if the temperature of the liquid carbon dioxide being transported were permitted to vary with the temperature variations of the surrounding atmosphere.

One of the features of this invention is to maintain the liquid carbon dioxide stored in the container unit ill at a sub-atmospheric temperature which will not exceed 32 F., and preferably to maintain the stored liquid at the temperature at which it is charged into the unit l8. In view of this fact, it is possible to substantially fill the internal volume of the unit it with liquid carbon dioxide notwithstanding the low working pressure of the unit. This makes possible the storage of a much larger quantity by weight of carbon dioxide per unit of container volume than would be possible if the carbon dioxide were stored at atmospheric temperature. It also makes possible a much lower cost per unit of storage capacity.

Associated with the container unit It are two diiTerent means for maintaining the liquid carbon dioxide at its charging temperature. One of these means consists of a standard commercial refrigerating plant 2i which has its evaporator coil 22 arranged within a dome 23 which is in open communication with the top of the container unit i8. As it is impossible to insulate the container unit against the penetration of any heat whatsoever, the heat which does penetrate will cause some of the liquid carbon dioxide to evaporate. The gas which forms as a result of this vaporization will rise from the liquid bath and will contact the coil 22. This contacting of the gas with the surface of the coil will cause the gas to condense and the condensation will be returned by gravity to the liquid bath. It has been determined that a coil of much less surface area can be employed with this arrangement than would be possible if the coil 22 were located beneath the surface of the liquid bath. By such refrigeration storage of any quantity of carbon dioxide may be had over indefinite periods with no gas loss whatsoever.

The second means for maintaining the liquid carbon dioxide at the sub-atmospheric tempera ture at which it is charged in the container unit i 8 consists of the pop-oi! or relief valve 24. This valve 24 may be of any desired and well known construction and is intended to be set or adiusted to open at the predetermined vapor pressure which corresponds with the temperature at which it is desired to maintain the liquid carbon dioxide.

As heat penetrates the insulation surrounding the container unit it, some of the liquid is vaporized and the vapor pressure will rise to the point at which the value 24 will operate. when the valve opens, carbon dioxide gas will be 'discharged therethrough to the atmosphere. This bleeding of gas to the atmosphere will be accompanied by vaporization of a like amount of the remaining liquid carbon dioxide. This vaporization is accompanied by or results from absorption of heat from the remaining liquid and brings about refrigeration of this liquid. This refrigeration of the liquid lowers its temperature and the corresponding vapor pressure until the pressure drops below the operating pressure of the valve 21.

It will be appreciated, therefore, that at the expense of the loss of a comparatively small fraction of the stored liquid, the remaining liquid may be maintained at the desired storage temperature. This loss of carbon dioxide is not excessive and can be readily calculated since it would be the ratio of the heat loss in B. t. 12. per hour to the latent heat of carbon dioxide at the stored temperature. For example, at 0 R, the latent heat is 120 B. t. u. per pound. A typical storage unit of approximately eight tons liquid carbon dioxide capacity has a rate of heat penetration through the insulation of approximately 1,200 B. t. u. per hour. Thus, the gas loss involved in maintaining the low pressure in the container unit would be a ratio of l,200:l20, or approximately ten pounds per hour. The loss in this typical case amounts to approximately l /2% in each twenty-four hours. This loss is less than the sublimation loss usually encountered in storing and handling solid carbon dioxide in the form of dry ice.

It will be appreciated that the refrigerating unit 2i and its cooling coil 22 may be employed in combination with the pop-off or relief valve 24 to provide several different modes of operation. For example, it is very desirable to employ a pop-oil valve 24 as a safety device which will function in the event of failure of the refrigerating apparatus. It will be appreciated, of course, that the refrigerating apparatus will be provided with any conventional form of temperature or pressure control which will cause the refrigeratlng apparatus to operate periodically only when it is necessary to extract heat from the carbon dioxide stored in the unit It. This automatic control, not shown, for the refrigerating unit can be set to maintain the carbon dioxide at a desired sub-atmospheric temperature. The relief valve 24, operating in combination with the refrigerating apparatus, can be set to open at a pressure in excess of the pressure at which the refrigerating apparatus will start to operate. Therefore, in the event of failure of the refrigerating apparatus, the valve 24 will operate to effect cooling of the carbon dioxide as a result of bleeding of gas to the atmosphere.

Of course, other methods of employing a relief valve in combination with a refrigerating unit may be used. For example, the cooling coil 22 may be connected in a refrigerating system which is employed for other purposes in connection with the building in which it is housed. This refrigerating system may be operated with minimum and maximum load periods. It may be desirable, therefore, to operate the coil 22 for maintaining the carbnn dioxde refrigerated only during the minimum load period of the refrigerating apparatus. The relief valve then would be a more important adjunct to the successful operation of the fire extinguishing apparatus. In any mode of operation where a relief valve is employed at least in part to maintain the carbon dioxide refrigerated, the container unit it should be serviced periodically by a distributor of the low temperature carbon dioxide for the purpose of maintaining the container unit it properly filled with the fire extinguishing medium.

Suitable manually controlled valves 25 are located at strategic points in the main supply or pipe lines 28 while a conventional expansion valve 25' is employed in the lines 21 of the refrigeratlng apparatus. By means of valves 25, selective delivery of the refrigerating medium to the various pipes of discharge devices may be provided as desired.

It has been determined by extensive experimental work that liquid carbon dioxide discharged at a temperature which does not exceed 32 F., is a much more efficient and efiective fire extinguishing medium than carbon dioxide gas released at atmospheric temperature. For example, a much higher percentage of yield of snow is obtained with the liquid carbon dioxide released at a sub-atmospheric temperature. Theoretically, carbon dioxide gas released at 70 F. produces 29% snow, while liquid carbon dioxide released to the atmosphere at 0 F. produces snow. 0! course, the lower the temperature at which the liquid carbon dioxide is discharged, the greater the percentage of yield of snow. This increased yield of snow provides a heavier blanket for smothering the fire by excluding oxygen from the same, and is not displaced by the natural air currents rising from the fire. This great yield of snow provides the discharge medium with greater mass which permits the medium to be directed at a fire with a greater velocity to more effectively penetrate the rising air currents and to permit the medium to be projected greater distances.

The snow sublimes at a relatively slow rate and thus prolongs the time it will be effective to exclude oxygen from the material which has been burning. This feature plus the availability of the lower temperature of the liquid carbon dioxide to cool the parts which have been heated by the tire, are very effective in preventing reflash. The increased cooling effect the larger yield of snow has upon the material being consumed by the fire, permits fire fighters to more closely approach the location of the fire. The density of carbon dioxide stored at low temperatures as compared to its density when released to the atmosphere gives a much greater increase in volume than is provided when the carbon dioxide is stored at atmospheric temperature. The density of liquid carbon dioxide at 8 F. is 64 pounds per cubic foot, and when expanded in the atmosphere, its density is 0.12 pound per cubic foot. Carbon dioxide stored at this low temperature, therefore, increases in volume 540 times. The expansion of carbon dioxide stored at F. is only about one-half as great as the expansion which occurs when the carbon dioxide is stored at 0 F.

It is to be understood that the forms of this invention herewith shown and described are to be taken as preferred examples of the same, and that various changes in the shape, size, and arrangement of parts may be resorted to without departing from the spirit of the invention or the scope of the subjoined claims.

Having thus described the invention, I claim:-

I. A method of employing carbon dioxide as a fire extinguishing medium which comprises charging an insulated storage space of large volumetric capacity with liquid carbon dioxide cooled to a sub-atmospheric temperature and its corresponding vapor pressure, maintaining said liquid carbon dioxide at a substantially constant subatmosphcric temperature and pressure during its entire period of storage, and conducting said carbon dioxide as a liquid at the stored subatmospheric temperature and pressure to the point 01' discharge onto the fire to be extin guished.

2. A method oi employing carbon dioxide as a ilre extinguishing medium which comprises charging an insulated storage space of large volumetric capacity with liquid carbon dioxide cooled to a temperature not to exceed 32 F. and at its corresponding vapor pressure, maintaining said liquid carbon dioxide at substantially its charging temperature and pressure during its entire period of storage, and conducting said carbon dioxide as a liquid at the stored sub-atmospheric temperature and pressure to the point of discharge onto the tire to be extinguished.

3. A method of employing carbon dioxide as a fire extinguishing medium which comprises charging an insulated storage space of large volumetric capacity with liquid carbon dioxide cooled to a sub-atmospheric temperature and its corresponding vapor pressure, refrigerating said carbon dioxide at a rate Just sufiicient to maintain it at a substantially constant subatmospheric temperature and pressure during its entire period of storage, and conducting said carbon dioxide as a liquid at the stored sub-atmospheric temperature and pressure to the point of discharge onto the tire to be extinguished.

4. A method of employing carbon dioxide as a fire extingusihlng medium which comprises charging an insulated storage space of large volumetric capacity with liquid carbon dioxide cooled to a sub-atmospheric temperature and its corresponding vapor pressure, condensing and returning the vapors released from the liquid at a rate suflicient to maintain the liquid at its charging temperature and pressure during its entire period of storage, and conducting said carbon dioxide as a liquid at the stored sub-atmospheric temperature and pressure to the point of discharge onto the tire to be extinguished.

5. A method of employing carbon dioxide as a fire extinguishing medium comprising charging an insulated storage space 01' large volumetric capacity with liquid carbon dioxide cooled to a sub-atmospheric temperature and its corresponding vapor pressure, maintaining said liquid carbon dioxide at substantially its charging temperature and pressure during its entire period of storage by bleeding to the atmosphere, when the vapor pressure of the stored carbon dioxide reaches a predetermined value, a suflicient quantity of gas to eflect refrigeration or the remaining liquid, and conducting said carbon dioxide as a liquid at the stored sub-atmospheric temperature and pressure to the point of discharge onto the fire to be extinguished.

6. A method of employing carbon dioxide as a fire extinguishing medium comprising charging an insulated storage space of large volumetric capacity with liquid carbon dioxide cooled to a temperature not to exceed 32 F. and at its corresponding vapor pressure. refrigerating said liquid carbon dioxide at a rate just suflicient to maintain it at its charging temperature and pressure during its entire period of storage, and conducting said carbon dioxide as a liquid at the stored sub-atmospheric temperature and pressure to the point of discharge onto the fire to be extinguished.

7. A method of employing carbon dioxide as a tire extinguishing medium comprising charging an insulated storage space of large volumetric capacity with liquid carbon dioxide cooled to a temperature not to exceed 32 F. and at its corresponding vapor pressure, condensing and returning the vapors released from the liquid at a rate suiiicient to maintain the liquid at its charging temperature and pressure during its entire period of storage, and conducting said carbon dioxide as a liquid at the stored subatmospheric temperature and pressure to the point of discharge onto the fire to be extinguished.

8. A method of employing carbon dioxide as a tire extinguishing medium which comprises charging an insulated storage space of large volumetric capacity with liquid carbon dioxide cooled to a temperature not to exceed 32 F. and at its corresponding vapor pressure, maintaining said liquid carbon dioxide at substantially its charging temperature and pressure during its entire period oi storage by bleeding to the atmosphere, when the vapor pressure of the stored carbon dioxide reaches a predetermined value, a sufficient quantity of gas to eiifect refrigeration of the remaining liquid, and conducting said carbon dioxide as a liquid at the stored sub-atmospheric temperature and pressure to the point of discharge onto the tire to be extinguished.

9. A method of employing carbon dioxide as a tire extinguishing medium which comprises maintaining a supply of liquid carbon dioxide at a substantially constant subatmospheric temperature and pressure during its entire period oi? storage, and conducting said carbon dioxide as a liquid at the stored subatmospheric temperature and pressure to the point of discharge onto the tire to be extinguished.

ERIC GEERTZ.