US3684019A - Method for fighting a fire - Google Patents

Abstract

A method for dispersing a fire extinguishant in which dual nozzles are employed in each sprinkler head to form separately a fine mist for cooling and a spray of coarse droplets to penetrate a fire plume and reach fuel surfaces to extinguish a fire.

Description

United States Patent OR 356845019 5R Emmons et al. [451 Aug. 15, 1972 [54] METHOD FOR FIGHTING A FIRE [56] References Cited [72] Inventors: Howard W. Emmons, 233 Concord UNITED STATES PATENTS d,S db ,M .01776; Che g g. ass w w 3,604,510 9/1971 Tamsh ..l69/37 x 1; 3 3:3; fii g 3,590,924 7/1971 Emmons et a]. ..169/39 L R a w u FarmS 3,384,182 5/1968 Rotvand ..l69/l A e esey 2,724,614 11/1955 Rider ..l69/37X Mass. 02181 [22] Filed: May 7, 1971 Primary ExaminerAllen N. Knowles Assistant l'lxaminerlhomas C. Culp, Jr. [2!] Appl' L332 Attorney-Lane, Aitken, Dunner & Ziems A l' ti Ba filmi 57 ABSTRACT [62] Divi 'offfSer. No. 786,659, c. 24, 1968, f

Pt No. 3 590 924 I v A method for dispersing a re extmgulshant 1n WhlCh dual nozzles are employed in each sprmkler head to a form separately a fine mist for cooling and a spray of [52] US. I. 0A0 coarse droplets to penetrate a fire plume and reach [5 C fuel surfaces to extinguish a fire. [58] Field of Search....169/1 A, l R, 39, 37; 239/545 12 Claims, 7 Drawing Figures DROPS COMPLETELY EVAPORATED DROPS PENETRATE THE HOT PLUME TO SUPPRESS FIRE 3 FINE SPRAY IATEIITEnws I 5 I972 SHEET 1 [1F 3 CURVE II (HIGH PRESSURE) PRIOR A d 3 DROP DIAMETER IN MILLIMETERS (APPROXIMATED) DROPS PENETRATE THE HOT PLUME TO 'SUPPRESS FIRE D m w A m R R O O W P w v E Y L E w T L E A R n w m C P S S P D. O O R R D D 1:] RUN-OFF FINE SPRAY NOZZLE DROP DIAMETER IN MILLIMETERS INVENTORS HOWARD W. EMMONS, CHENG YAO 8| (APPROXIMATED) I 'JAMES B. SMITH PATENTEDws 15 I972 SHEEI 2 OF 3 INVENTORS HOWARD W. EMMONS, CHENG YAO 8 JAMES B. SMITH METHOD FOR FIGHTING A FIRE CROSS-REFERENCE TO RELATED APPLICATION This application is a division of applicants copending application Ser. No. 786,659, filed Dec. 24, 1968, and entitled Dual Nozzle Sprinkler Head, now US. Pat. No. 3,590,924 issued July 6, 1971.

BACKGROUND OF THE INVENTION This invention relates to an improved method for fighting a fire and, more particularly, it concerns a method in which the particle or drop size of an extinguishant spray released upon the occurrence of a fire in a closure protected by the system is regulated to provide optimum fire extinguishing capabilities in the system.

In accordance with conventional methods used to provide fire protection for a building enclosure and its contents, an extinguishant, such as water, is discharged through a plurality of nozzles incorporating a heat sensitive fusible releasing device and a deflector positioned immediately ahead of the nozzle. The deflector is designed to break up the solid jet of water issuing from the nozzle into a spray formed of small drops varying in size from less than 1 millimeter in diameter (e.g., several microns) to several millimeters in diameter. In this type of method the various drop size distributions within the extinguishing spray behave differently in the extinguishment of a fire. In the case of a large industrial fire, for example, fine drops in the spray, approximately 500 microns in diameter or less, tend to evaporate completely and serve the important function of cooling the ambient atmosphere particularly at the upper level of the building enclosure where the sprinkler heads are located. Larger drops, on the other hand, are required to penetrate the rising plume of combustion products over burning fuel surfaces to reach the surfaces and extinguish the fire. Such large diameter drops are, therefore, essential to effective extinguishment of a large or fast growing fire. In conventional sprays, however, there are a significant number of drops falling between these size ranges which perform neither of the useful functions aforementioned because they tend to be pushed away from the rising hot plume of combustion products and fall to the lower level of the enclosure outside the fire zone. These intermediatesize drops, therefore, contribute significantly to the amount of extinguishant run-off and unwanted water damage to the protected space.

Because the operating parameters of conventional sprinkler heads are fixed, control over the size of drops in a fire extinguishant spray has been limited heretofore by variations in extinguishant pressure, which in turn determines the velocity at which the extinguishant is emitted from the sprinkler head nozzle. In general, for a given orifice size higher pressures produce a larger number of small droplets in the spray whereas coarse or large diameter droplets are developed in sprays generated under lower pressures. Pressure regulation of the water jet issuing from the nozzle is inadequate from the standpoint of developing the most efficient drop size distribution in a fire extinguishant spray, however, since an increase in pressure to produce a larger number of fine droplets results in sacrificing the number of large droplets in the spray which would penetrate the plume of combustion products and reach the fuel surfaces to extinguish the fire. Correspondingly, lowering the pressure to increase the number of large diameter drops in the spray results in the sacrifice of the ambient air-cooling function of the fine droplets whereas a compromise between high and low pressure results in an increase of the intermediate size particles contributing to run-off and water damage.

The problem of pressure balancing conventional sprinkler heads is further illustrated by tests conducted with such heads operated at normal pressures of about 40 lb. per square inch. It was found that at this normal operating condition, less than 24 percent of the drops in the spray, which was discharged about 14 feet directly above the fire, were large enough to penetrate the rising plume of a 1.5 gallons per minute gasoline spray fire. Further tests under these operating conditions indicate that an 8 foot by 6 foot gasoline pan fire burning at a rate of about 4 gallons per minute would normally open or release up to 20 to 30 sprinkler heads spaced at 10 foot intervals in two normal directions, the vast majority of which were positioned remotely from the fire. Obviously, the remote sprinkler heads not only contributed very little to ambient air-cooling but also accomplished nothing insofar as extinguishment of the fire was concerned. Hence, substantially all of the water issuing from the remote sprinkler heads constituted waste run-off of the type giving rise to severe water damage.

SUMMARY OF THE INVENTION In accordance with the method of the present invention, the extinguishant is discharged in two different forms, one being a fine spray consisting of droplets almost entirely in a range where they completely evaporate to cool the ambient atmosphere, and the other being a coarse spray of droplets of a sufficiently large diameter to penetrate the plume of combustion products and reach the burning fuel surface thereunder to extinguish the fire. Preferably, the two sprays referred to are discharged from one dual nozzle sprinkler head but it is contemplated that the method of the present invention may be practiced in systems using conventional, single nozzle heads in which fine spray nozzles are spaced between coarse droplet nozzles in the space to be protected. In some instances, it is contemplated that the respective nozzles may be actuated at different temperatures. For example, the nozzle from which the fine spray is emitted may be equipped with a low temperature release to inhibit the spread of a fire whereas the coarse spray nozzle may be equipped with a high temperature release so that it will be actuated upon the development of a plume of combustion products. However, it is also possible, in accordance with this invention, that both nozzles be actuated by a common release device.

Accordingly, it is among the objects of the present invention to provide a method for extinguishing a fire in which optimum drop size distribution in fire extinguishant spray is developed which is highly effective in the control and extinguishment of a fire without excessive run-off and resulting water damage.

Other objects and further scope of applicability of the present invention will become apparent from the detailed description to follow, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic illustration of three drop size distribution curves in which approximate drop diameter in an extinguishant spray is plotted against the occurrence frequency of drops by volume at the respective approximate drop diameters for conventional fire extinguishing sprinkler head;

FIG. 2 is a schematic diagram similar in type to FIG. 1 but depicting the spray developed in accordance with the present invention;

FIG. 3 is a vertical cross-section through one form of a dual nozzle sprinkler head utilized in accordance with the method of the present invention;

FIG. 4 is a side elevation in partial cross-section of another form of dual nozzle sprinkler head utilized in accordance with the method of the present invention;

FIG. 5 is a vertical cross-section through still another modification of the dual nozzle sprinkler head utilized in accordance with the method of the present invention;

FIG. 6 is a schematic diagram showing a fire extinguishing system utilized to practice the method of the present invention; and

FIG. 7 is a schematic diagram illustrating the system of FIG. 6 in elevation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS To'facilitate an understanding of the concepts underlying the method of the present invention, reference is made to the drop size distribution curves shown respectively in FIGS. 1 and 2 of the drawings. In FIG. 1, three such curves are shown depicting the approximate drop size distribution in a fire extinguishant spray issuing from a conventional sprinkler head. Specifically, Curve I represents the drop size distribution for normal pressures on the order of 40 lb. per square inch; Curve II represents the drop diameter distribution at relatively higher pressures, and Curve III the drop diameter distribution at low pressures, it being assumed that the same sprinkler head is used in each instance. It might be mentioned also that these curves were developed using the drop diameter in millimeters as the horizontal coordinate or abscissa and plotting the number of drops at each size respectively as the vertical axis or ordinate in terms of the relative volume of extinguishant represented by the respective drop sizes. In an extinguishant spray from a conventional sprinkler head, therefore, the drops represented by the area A in FIG. 1 or less than the diameter d (approximately one-half millimeter) are completely evaporated under the conditions of a fire. Those drops of a size greater than d (approximately 2.8 millimeters) and larger are represented by the area B and in practice are believed to penetrate the fire plume to reach the burning fuel source. Droplets between the diameters d and d are depicted by the areas C and D in FIG. 1 which areas respectively represent droplets partially evaporated and those which tend to be pushed away from a rising hot plume of combustion products over a burning fuel source. The relatively large size of the area D as compared with the areas A, B and C is significant in that it represents the proportion of extinguishant in the spray from a conventional sprinkler head which not only contributes very little to the fire extinguishing function of the spray, but moreover contributes to water damage as run-off. On the other hand, the droplets represented by the areas A and C contribute to the fire extinguishing function by virtue of cooling ambient atmosphere through evaporation and thus inhibit the spread of the fire. Similarly, the large size droplets represented by the area B in FIG. 1 contribute to the fire extinguishing function of the spray by penetrating the plume and reaching the burning fuel surfaces.

Curves II and III in FIG. 1 further illustrate the problem of varying the pressure at which a spray is emitted from the nozzle of a conventional sprinkler head in that increased pressure to augment the cooling effect of the spray results in a sacrifice of available extinguishant to put out the fire at its source. Similarly, lowering the pressure to produce larger droplets within the spray gives rise to a sacrifice of the cooling by evaporation.

The distribution curve in FIG. 2 illustrates the drop diameter size distribution in a fire extinguishant spray in accordance with this invention. By employing two separate nozzles, that is, a fine spray nozzle and a coarse spray nozzle, the fine spray nozzle can be selected to develop a spray in which the drop diameters are essentially all smaller than I millimeter. The volume of the spray issuing from'the fine spray nozzle is depicted by the area A and C in FIG. 2. The low pressure nozzle, on the other hand, develops a spray with drop size diameters in excess of d,,, the volume of the spray issuing from the coarse spray nozzle being represented by area B in FIG. 2. It will be noted that the drops in the size range between d and d the volume of which is represented by the area D in FIG. 2, is significantly reduced relative to the area D in FIG. 1 of the drawings.

Alternative dual nozzle sprinkler heads for achieving the drop size distribution represented by the curve in FIG. 2 are illustrated in FIGS. 35 of the drawings. In the embodiment of FIG. 3, the fine nozzle is a standard opposed jet nozzle 10 connected to one outlet of a T- fitting 12 having its inlet connected to a vertically disposed water supply pipe 14. A quartz bulb release 16 normally prevents the issuance of water or other extinguishant through the opposed jet nozzle 10 but ruptures upon a temperature increase to open the nozzle. The coarse nozzle in the embodiment of FIG. 3 takes the form of a conventional pendant nozzle 17 having a discharge opening 18 and a serrated distributor plate 20 positioned thereunder. The release in this instance is a conventional link lever release 22 having a fuse 24 and a cap 26 which moves out of the opening 18 when the temperature about the fuse 24 exceeds a predetermined amount. Since the supply of water or other extinguishant from the pipe 14 to both nozzles 10 and 17 is under the same pressure head, a restricted orifice is positioned ahead of the outlet tube 18 of the coarse nozzle. The restricted orifice 28 will operate to reduce the velocity and thus the effective pressure at which the extinguishant is issued from the pendant coarse nozzle 17.

The quartz bulb release 16 is preferably designed to release at a lower temperature than the fusible link 24 of the nozzle 17. In this manner, as the heat of the fire initially develops, the nozzle 10 will first open to develop a fine spray or mist, the droplets of which will immediately evaporate to cool the ambient atmosphere. This cooling action tends to slow down the release of sprinkler heads positioned in the building enclosure remotely from the fire. Then as the temperature rises the fuse link 24 releases to permit the extinguishant to pass through the pendant nozzle 17 in relatively large or coarse droplets capable of penetrating the fire plume beneath the sprinkler head to extinguish the fire.

In FIG. 4 another dual nozzle sprinkler head which may be utilized in the method of the present invention is shown which is adapted for use with a horizontal line 30. In this instance an X-type fitting 32 is employed with the pendant low pressure nozzle 17 extending from a lower outlet arm 34 thereof and the fine spray 'nozzle coupled to the upwardly extending branch 36 of the fitting. The fine spray nozzle in this instance takes the form of a radial spray or fog nozzle 38 equipped with a link lever fuse release 40. The operation of the head in FIG. 4 is essentially the same as the head of FIG. 3 apart from the particular types of nozzles employed, each of which, by itself, is conventional.

In FIG. 5 another head that can be utilized in the method of the present invention is illustrated, and features the actuation of both fine spray and coarse nozzles by a common release 42. In this instance, the nozzles are identical in type to the corresponding nozzles and 17-in the head of FIG. 3. However, a valve member 44 having a serrated skirt 46 and a stem 48 is adapted to be seated upwardly against the supply line 14. Upon actuation, the valve moves downwardly so that the serrated skirt 46 thereof rests on the restricted orifice plate 28, thereby opening both nozzles. The operation of the device to develop the fine and coarse sprays as aforementioned is the same as that described above with respect to FIG. 3, with the exception of the difference in release temperatures afforded by the embodiment of FIG. 3.

The use of dual nozzle sprinkler heads of the type shown in FIGS. 3-5 of the drawings is preferred in the method of the present invention because of the facility offered thereby for installation. In other words, each of the dual nozzle sprinkler heads, being a unit by itself, is simply installed according to specification without having to rely on individual workmen to effect proper positioning of the respective fine and coarse spray nozzles. It is possible, however, that separate single nozzle heads be used and arranged in a manner to effect the basic fire extinguishing technique of the method of the present invention. Such an arrangement is shown in FIGS. 6 and 7 of the drawings.

As shown in FIG. 6, a plurality of coarse nozzle sprinkler heads 50 are arranged in conventional fashion beneath the ceiling 52 of a building space 54 to be protected. An extinguishant such as water is supplied to the coarse nozzle heads 50 in conventional fashion by main and branch lines 56 and 58, respectively. Also provided in the ceiling of the building enclosure 54 are fine spray nozzle heads 60 evenly spaced between the coarse spray heads 50. Although the fine spray heads 60 could be supplied with an extinguishant such as water from the pipes 56 and 58 through use of suitable connections, the fine spray nozzle heads 60 in the system shown in FIG. 6 are supplied with extinguishant by independent pipes depicted by dash lines 62. The

use of separate supply lines is advantageous in that the line pressures supplying the respective coarse and fine nozzle heads 50 and 60 can be adjusted independently. The operation of the system shown in FIGS. 6 and 7, which is essentially similar to that of the dual nozzle sprinkler heads described above, is depicted in FIG. 7 of the drawings. As shown, the existenceof a fire plume 63 will activate automatically one or more of the coarse heads 50 thereover to provide a spray of large droplets 64 to penetrate the fire plume 63, reach the burning fuel surfaces 66 and extinguish the fire. In the meanwhile, fine nozzle sprinkler heads 60 in the vicinity of the activated coarse nozzle head or heads 50 will be activated to disperse a fine spray 68 consisting essentially of small droplets which evaporate readily. The evaporation of these fine droplets will tend to cool the interior of the building space 54 particularly along the ceiling 52 thereof. As a result, only those coarse nozzle sprinkler heads 50 which are required to extinguish the fire 63 will be activated. Not only will this mode of operation avoid unnecessary water damage due to remote sprinkler heads being actuated ineffectively, but also the inactive condition of the remote sprinkler heads will serve to ensure an ample supply of water to the sprinkler heads actuated directly by the heat of the fire.

Thus it will be appreciated that by the use of a fine and coarse spray in accordance with the method of the present invention, the drop size distribution in the spray developed by the sprinkler system is effective both from the standpoint of providing a spray or mist for cooling the atmosphere over a fire and as well to provide drop sizes sufficiently large in size to penetrate a fire plume and reach the burning fuel surfaces thereof. Also and equally significant, the amount of extinguishant run-off due both to particle size distribution and unnecessary release of remote sprinkler heads is reduced to a minimum.

It is understood that various other means of discharging the extinguishant may be utilized in the method of the present invention as long as the principles disclosed above are followed and that still other modifications can be made in the method of the present invention, without departing from the scope thereof. Accordingly, it is expressly intended that the foregoing description is illustrative of preferred embodiments only, not limiting, that the true spirit and scope of the present invention be determined by the appended claims.

We claim:

1. A method of fighting a fire comprising the step of discharging at least two streams of extinguishant towards said fire in response to information received from said fire, one of said streams being comprised substantially of finely divided droplets of extinguishant which evaporate readily to cool the ambient atmosphere, and at least one other of said streams being comprised substantially of relatively large droplets of extinguishant capable of penetrating a rising plume of combustion products to reach the burning fuel surfaces of a fire.

2. The method recited in claim 1 wherein substantially all of the droplets of said one stream are less than 1 millimeter in diameter and wherein the droplets of said other stream are larger than approximately 2 millimeters in diameter.

3. The method recited in claim 1 wherein said one stream is discharged in advance of said other stream.

4. The method recited in claim 1 wherein said streams are simultaneously discharged from the same source.

5. The method as recited in claim 4 further comprising the step of reducing the pressure of the extinguishant of said other stream relative to the pressure of the extinguishant of said one stream before the discharge of said streams from said source.

6. The method recited in claim 1 wherein said streams are discharged from separate sources.

7. The method recited in claim 1 wherein said one stream and said other stream are discharged in response to different information received from the fire.

8. The method recited in claim 1 wherein said one stream and said other stream are discharged in response to the same information received from the fire.

9. The method recited in claim 1 wherein a plurality of each of said streams is discharged, said one streams providing maximum cooling effect near the ceiling of the building being protected, said other streams providing maximum fire fighting capability, said one streams inhibiting the activation of said other streams to reduce the number of other streams to those over the fire area and thereby help insure an ample supply of water for fighting the fire.

10. The method of claim 1 further comprising the step of mounting a plurality of extinguishant discharge heads in an elevated position in the space to be protected from fire, each of said heads adapted to discharge said two streams of extinguishant.

11. The method of claim 10 wherein said one stream and said other stream are discharged from each head in response to different information received from the fire.

12. The method as recited in claim 11 further comprising the step of reducing the pressure of the extinguishant of said other stream relative to the pressure of the extinguishant of said one stream before the discharge of said streams from said head.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent; 3,684,019 Dated August 15, 1972 Howard W. Emmons et a1. Inventor (s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the Title Page insert:

-- [73] Assignee: Factory Mutual Research Corporation,

Boston-Providence Turnpike, Mass.

Signcd and Scaled this Thirtieth D y f ay 1978 |sm|.|

Arm-r.-

RLTH MASON I.U'IRI-II.I.E F. PARKER Am'sling ()jficer Acting ('ommixxioner of Parents and Trademarks

Claims (12)

1. A method of fighting a fire comprising the step of discharging at least two streams of extinguishant towards said fire in response to information received from said fire, one of said streams being comprised substantially of finely divided droplets of extinguishant which evaporate readily to cool the ambient atmosphere, and at least one other of said streams being comprised substantially of relatively large droplets of extinguishant capable of penetrating a rising plume of combustion products to reach the burning fuel surfaces of a fire.

2. The method recited in claim 1 wherein substantially all of the droplets of said one stream are less than 1 millimeter in diameter and wherein the droplets of said other stream are larger than approximately 2 millimeters in diameter.

3. The method recited in claim 1 wherein said one stream is discharged in advance of said other stream.

4. The method recited in claim 1 wherein said streams are simultaneously discharged from the same source.

5. The method as recited in claim 4 further comprising the step of reducing the pressure of the extinguishant of said other stream relative to the pressure of the extinguishant of said one stream before the discharge of said streams from said source.

6. The method recited in claim 1 wherein said streams are discharged from separate sources.

7. The method recited in claim 1 wherein said one stream and said other stream are discharged in response to different information received from the fire.

8. The method recited in claim 1 wherein said one stream and said other stream are discharged in response to the same information received from the fire.

9. The method recited in claim 1 wherein a plurality of each of said streams is discharged, said one streams providing maximum cooling effect near the ceiling of the building being protected, said other streams providing maximum fire fighting capability, said one streams inhibiting the activation of said other streams to reduce the number of other streams to those over the fire area and thereby help insure an ample supply of water for fighting the fire.

10. The method of claim 1 further comprising the step of mounting a plurality of extinguishant discharge heads in an elevated position in the space to be protected from fire, each of said heads adapted to discharge said two streams of extinguishant.

11. The method of claim 10 wherein said one stream and said other stream are discharged from each head in response to different information received from the fire.

12. The method as recited in claim 11 further comprising the step of reducing the pressure of the extinguishant of said other stream relative to the pressure of the extinguishant of said one stream before the discharge of said streams from said head.

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