U.S. patent number 3,590,924 [Application Number 04/786,659] was granted by the patent office on 1971-07-06 for dual nozzle sprinkler head.
This patent grant is currently assigned to Factory Mutual Research Corporation. Invention is credited to Howard W. Emmons, James B. Smith, Cheng Yao.
United States Patent |
3,590,924 |
Emmons , et al. |
July 6, 1971 |
DUAL NOZZLE SPRINKLER HEAD
Abstract
Method and apparatus 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.
Inventors: |
Emmons; Howard W. (Sudbury,
MA), Yao; Cheng (Weston, MA), Smith; James B.
(Wellesley Farms, MA) |
Assignee: |
Factory Mutual Research
Corporation (Boston-Providence Turnpike, MA)
|
Family
ID: |
25139241 |
Appl.
No.: |
04/786,659 |
Filed: |
December 24, 1968 |
Current U.S.
Class: |
169/16; 169/43;
239/545; 169/39; 169/70 |
Current CPC
Class: |
A62C
37/08 (20130101) |
Current International
Class: |
A62C
37/08 (20060101); A62c 037/12 () |
Field of
Search: |
;169/1,2,5,16,17,37,38,40,41 ;239/545 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wood, Jr.; M. Henson
Assistant Examiner: Mar; Michael Y.
Claims
I claim:
1. A sprinkler head for fixed fire-extinguishing systems, said head
comprising: a fitting having an inlet for connection to a source of
extinguishant and at least two outlets, first discharge means in
one of said outlets to disperse a finely divided spray of
extinguishant, second discharge means in the other of said outlets
to disperse relatively large droplets of extinguishant, and
temperature-responsive means to actuate said first and second
discharge means.
2. The apparatus recited in claim 1 including means for supplying
extinguishant from said inlet to said second discharge means at a
lower pressure than said first discharge means.
3. The apparatus recited in claim 2 wherein said means for
supplying extinguishant from said inlet to said second discharge
means comprises means establishing a restricted orifice in said
other outlet.
4. The apparatus recited in claim 1 wherein said
temperature-responsive means comprises separate fuse elements for
each of said first and second discharge means.
5. The apparatus recited in claim 4 wherein the fuse element for
said first discharge means is releasable at a lower temperature
than the fuse element for said second discharge means.
6. The apparatus recited in claim 1 comprising a valve member
normally blocking said inlet, said valve member being movable under
the control of said temperature-responsive means to an open
position establishing fluid communication between said inlet and
said first and second discharge means.
7. In a fixed fire-extinguishing system of the type in which an
extinguishant is supplied to automatically actuated sprinkler heads
located in a space to be protected, a plurality of coarse spray
nozzles to develop one extinguishant spray of droplets having a
size capable of penetrating a rising plume of combustion products,
and a plurality of fine spray nozzles to develop another
extinguishant spray of fine droplets which readily evaporate and
cool ambient atmosphere upon activation.
8. The apparatus recited in claim 7 wherein both said coarse spray
nozzles and said fine spray nozzles are included in each of a
plurality of sprinkler head units.
9. The apparatus recited in claim 7 including separate means for
supplying extinguishant to said fine and coarse nozzles
respectively.
10. The apparatus recited in claim 7 including first means
automatically responsive to a fire in said space for controlling
the opening of said coarse spray nozzles, and second means
automatically responsive to a fire in said space for controlling
the opening of said fine spray nozzles, said second means opening
said fine spray nozzles in advance of the opening of said coarse
spray nozzles by said first means.
11. The apparatus recited in claim 10 wherein said coarse and fine
spray nozzles and said first and second means are included in each
of a plurality of sprinkler head units, said first and seconds
means being responsive to heat generated by the fire.
Description
BACKGROUND OF THE INVENTION
This invention relates to improved sprinkler heads and methods for
operating fixed fire-extinguishing systems and, more particularly,
it concerns dual-nozzle sprinkler heads for such extinguishing
systems by 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.
Sprinkler heads conventionally used in fire-extinguishing systems
of the type designed to protect a building enclosure and its
contents employ a nozzle through which an extinguishant such as
water is passed, 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. It is also known that 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 intermediate size drops, therefore, contribute
significantly to the amount of extinguishant runoff 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 droplets contributing to runoff 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 pounds 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- 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 runoff of
the type giving rise to severe water damage.
SUMMARY OF THE INVENTION
In accordance with the present invention, a fire-extinguishing
system is provided with two types of extinguishant nozzles, one of
which is designed to develop a fine spray consisting of droplets
almost entirely in a range where they completely evaporate to cool
the ambient atmosphere while the other nozzle of the head is
designed to develop droplets of a sufficiently large diameter that
they penetrate the plume of combustion products and reach the
burning fuel surface thereunder to extinguish the fire. Preferably,
the two types of nozzles referred to will be embodied in one
dual-nozzle sprinkler head but it is contemplated that the
invention may be practiced in systems using conventional,
single-nozzle heads in which fine spray heads are spaced between
coarse spray heads in the space to be protected by the system. In
some instances, it is contemplated that each of the nozzles will be
provided with its own temperature release device so that the
respective nozzles in each head 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 may be actuated by a common release device.
Accordingly, it is among the objects of the present invention to
provide a fixed fire-extinguishing system in which optimum drop
size distribution in fire extinguishant spray is developed; the
provision of a sprinkler head for fire extinguishing systems which
develops drop size distribution in an extinguishant spray which is
highly effective in the control and extinguishment of a fire
without excessive runoff and resulting water damage; the provision
of a dual-nozzle sprinker head in which one of the nozzles is a
high-pressure fine spray nozzle whereas the other is a low-pressure
coarse spray nozzle; the provision of a dual-nozzle sprinkler head
of the type aforementioned in which the respective nozzles thereof
may be released at different temperatures; and the provision of a
unique method for developing a fire extinguishant spray.
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 approximated 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 dual-nozzle
sprinkler head in accordance with the present invention;
FIG. 4 is a side elevation in partial cross section of another form
of dual-nozzle sprinkler head in accordance with this
invention;
FIG. 5 is a vertical cross section through still another
modification of the dual-nozzle sprinkler head of this
invention;
FIG. 6 is a schematic diagram showing an alternative form of
fire-extinguishing system in relation to a building space protected
thereby; 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
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
pounds 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.sub.c (approximately one-half millimeter) are completely
evaporated under the conditions of a fire. Those drops of a size
greater than d.sub.a (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.sub.a and d.sub.c 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 runoff.
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. 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 1 millimeter. The volume of the spray
issuing from the fine spray nozzle is depicted by the area A.sub.1
and C.sub.1 in FIG. 2. The coarse spray nozzle, on the other hand,
develops a spray with drop size diameters in excess of d.sub.a, the
volume of the spray issuing from the coarse spray nozzle being
represented by area B.sub.1 in FIG. 2. It will be noted that the
drops in the size range between d.sub.c and d.sub.a, the volume of
which is represented by the area D.sub.1 in FIG. 2, is
significantly reduced relative to the area D in FIG. 1 of the
drawings.
Alternative dual-nozzle sprinkler head embodiments for achieving
the drop size distribution represented by the curve in FIG. 2 are
illustrated in FIGS. 3--5 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 in the embodiment of FIG. 3 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 a dual-nozzle sprinkler head in accordance with this
invention is shown and 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 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 embodiment in FIG.
4 is essentially the same as that of FIG. 3 apart from the
particular types of nozzles employed, each of which, by itself, is
conventional.
In FIG. 5 a further modification of the invention is illustrated
wherein both fine spray and coarse nozzles are adapted to be
actuated by a common release 42. In this instance, the nozzles are
identical in type to the corresponding nozzles 10 and 17 in the
embodiment 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 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 this 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 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 existence of 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 this invention, there is
provided extremely effective method and apparatus for developing a
fire-extinguishing spray. By the use of fine and coarse spray
nozzles, the drop size distribution in the spray developed by the
sprinkler system is effective both from the standpoint of providing
a fine 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 runoff due both to
particle size distribution and unnecessary release of remote
sprinkler heads is reduced to a minimum.
It will be appreciated that various modifications can be made in
the present invention as described above. 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.
* * * * *