U.S. patent number 3,722,596 [Application Number 05/216,845] was granted by the patent office on 1973-03-27 for fire protection system.
This patent grant is currently assigned to Factory Mutual Research Corporation. Invention is credited to William L. Livingston.
United States Patent |
3,722,596 |
Livingston |
March 27, 1973 |
**Please see images for:
( Certificate of Correction ) ** |
FIRE PROTECTION SYSTEM
Abstract
A method of fire protection in which extinguishant is delivered
to a plurality of discharge heads located in the space to be
protected from fire. The number of heads that are opened to deliver
extinguishant in response to a fire situation is limited to those
located in the immediate vicinity of the fire. In this manner the
opened heads are not robbed of valuable extinguishant, and water
damage to materials located in areas remote to the fire is
minimized. A discharge head utilized in the above method.
Inventors: |
Livingston; William L. (Sharon,
MA) |
Assignee: |
Factory Mutual Research
Corporation (Boston, MA)
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Family
ID: |
27490972 |
Appl.
No.: |
05/216,845 |
Filed: |
January 10, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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72333 |
Sep 15, 1970 |
3653444 |
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864612 |
Oct 8, 1969 |
3645338 |
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885501 |
Dec 16, 1969 |
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Current U.S.
Class: |
169/60; 169/37;
169/16 |
Current CPC
Class: |
A62C
37/08 (20130101) |
Current International
Class: |
A62C
37/08 (20060101); A62c 037/08 () |
Field of
Search: |
;169/1R,1A,1B,2R,5,14,15,16,37,38,42 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wood, Jr.; M. Henson
Assistant Examiner: Mar; Michael
Parent Case Text
CROSS REFERENCES TO RELATED APPLICATIONS
This application is a divisional of Ser. No. 72,333, filed Sept.
15, 1970, now U.S. Pat. No. 3,653,444, entitled Fire Protection
System, which is turn is a continuation-in-part of copending
application Ser. No. 864,612 filed Oct. 8, 1969, now U.S. Pat. No.
3,645,338, entitled Improved Fixed Fire Extinguishing System and
copending application Ser. No. 885,501 filed Dec. 16, 1969, now
abandoned, entitled Adaptive Sprinkler Head.
Claims
I claim:
1. A method of fire protection comprising the steps of disposing a
plurality of extinguishant dispersing heads in a space to be
protected, delivering extinguishant from a source of supply to all
of the heads in said space, actuating the heads in a sequence
dictated by information received from a fire developing in said
space, and controlling the opening of said heads in a manner to
reduce the total number of heads in said space which will be opened
to deliver extinguishant to the fire as compared to the total
number of heads in said space which would be opened by the same
information received from the fire acting on the same system
without said control means.
2. The method as defined in claim 1 wherein each head is
individually controlled in said step of controlling.
3. The method as defined in claim 1 wherein said step of
controlling comprises the step of preventing additional heads from
being actuated when the system reaches a predetermined condition
after a limited number of heads have been opened.
4. The method as defined in claim 1 wherein said step of
controlling is effected in response to a predetermined condition of
said extinguishant.
5. The method as defined in claim 4 wherein said step of
controlling comprises the step of maintaining unopened heads closed
when the pressure of the extinguishant in said system drops below a
predetermined level.
6. The method as defined in claim 4 wherein said step of
controlling is effected in response to the static pressure of the
extinguishant at each unopened head.
7. The method as defined in claim 1 wherein said step of
controlling comprises the step of regulating the point at which
said fire responsive means actuates said heads.
8. The method as defined in claim 1 wherein said step of delivering
comprises the step of delivering extinguishant at a maximum
delivery rate capacity sufficient to supply the reduced number of
heads which will be opened by the same information received from
the same fire and insufficient to supply the number of heads which
would be opened by the same information received from the same fire
acting on the same system without said control means.
9. The method as defined in claim 1 wherein the extinguishant is
discharged from each opened head directly down on the fire in a
solid cone spray pattern having a spray angle less 180.degree..
10. The method as defined in claim 1 wherein said step of
delivering comprises the step of supplying water to said heads and
introducing an ablative additive to the water to convert the water
to an ablative fluid to be dispersed from said heads.
11. The method as defined in claim 1 wherein said step of actuating
is done at all times and wherein said step of controlling comprises
the step of preventing the individual heads from opening after they
have been actuated.
12. The method as defined in claim 1 wherein said steps of
actuating and controlling together enable a predetermined number of
heads to be opened when actuated by the fire responsive means and
thereafter restrict the opening of additional heads.
13. A discharge head for a fire extinguishing system comprising a
body member having an inlet for connection to a source of
extinguishant and an outlet for discharging extinguishant, means
adapted to cooperate with said body member and move from a normal
position in which extinguishant discharge from said outlet is
prevented to a second position in which extinguishant discharge
from said outlet is permitted, and means responsive to a
predetermined fire condition and to an extinguishant pressure
greater than a predetermined pressure for permitting movement of
said first mentioned means to said second position, said responsive
means being independent of changes in said pressure after said
first mentioned means has moved to said second position.
14. The head of claim 13 wherein said first mentioned means
comprises plug means for said outlet and latching means for
normally latching said plug means in said outlet.
15. The head of claim 14 wherein said responsive means cooperates
with said latching means for causing said latching means to release
said plug means.
16. The head of claim 13 wherein said first mentioned means
comprises plug means for said outlet and retaining means for
normally retaining said plug means in said outlet.
17. The head of claim 16 wherein said responsive means cooperates
with said retaining means for causing said retaining means to
release said plug means.
18. The head of claim 16 wherein said retaining means comprises a
latching assembly for normally latching said plug means in said
outlet and connecting means for normally connecting said plug means
relative to said body member.
19. The head of claim 18 wherein said responsive means comprises
first control means cooperating with said latching assembly for
releasing said plug means in response to said predetermined fire
condition, and second control means cooperating with said
connecting means for releasing said plug means in response to said
extinguishant pressure.
Description
BACKGROUND OF THE INVENTION
Automatic extinguishant discharge systems for protecting industrial
and commercial properties are almost exclusively sprinkler systems
and employ thermally releasable sprinkler heads located near the
top of the space being protected. The sprinkler heads are supplied
with a suitable extinguishant, such as water, by a pipe network of
mains, risers, cross mains and branches. Most sprinkler heads used
in automatic sprinkler systems have a one-half inch discharge
opening or throat normally closed by a plug retained by a thermal
fuse and collapsible linkage bridging an external loop or yoke.
Upon actuation of the head by collapse of the linkage, the
extinguishant stream issuing from the throat impinges against a
serrated deflector disc to form a hemispherical pattern of droplets
simulating the characteristics of rain.
Because of the high degree of head standardization, design
parameters for automatic sprinkler systems have, in the past, been
limited to a selection of head release temperatures, head spacing
and system supply capacity, including pipe sizes and the like. In
the selection of a head release temperature it has been
conventional practice to select sprinklers with higher temperature
ratings than those which would respond quickly to the existence of
a fire in the protected space. Although such a delayed response is
sometimes undesirable, the disadvantages are outweighed by such
advantages as avoidance of accidental release and potential loss by
water damage, and the avoidance of heads located remotely from the
actual fire being actuated by the effects of convection and the
circulation of hot combustion products throughout the protected
space. This latter factor is believed to be one of the principal
causes for failure of automatic sprinkler systems, particularly in
the case of intense high challenge fires where all available
extinguishant is needed on and near the burning fuel surfaces to
bring the fire under control.
The selections of head spacing and water supply capacity for water
sprinkler systems are predicated largely on the required water
density needed to extinguish the most intense fire anticipated and
on economic considerations. For example, since the maximum amount
of extinguishant capable of being delivered by one head is
relatively fixed by the size of its discharge orifice (usually
one-half inch in diameter), increased densities have been achieved
in the past by overlapping the floor areas to which extinguishant
is directed by each of the heads. In other words, where increased
densities are called for, the number of heads employed in the
system is increased and the spacing between heads reduced to
achieve overlapping coverage. The capacity of the water supply
required to supply such heads has in the past involved the
application of conventional principles of fluid flow, taking into
account the flow requirements of all of the sprinkler heads when
operating under the conditions presented by the most destructive
fire which is anticipated.
Although automatic sprinkler systems of the type described have
been an effective means for the protection of property against loss
or damage by fire, the trend during recent years to higher storage
enclosures coupled with the increased use of plastics has presented
new challenges for such systems. For example, recent extensive
studies with actual and synthetically produced fire plumes or
columns have shown that in enclosed spaces of 20 feet and higher,
the updraft or chimney effect caused by convection alone is
sufficient to prevent the free falling water droplets produced by
conventional sprinkler heads from penetrating the rising fire plume
and reaching the burning fuel surfaces. Because of this phenomenon,
such sprinkler systems merely operate to wet down or inhibit the
spread of a high challenge fire within the space and thus provide
what is referred to as exposures protection. However, the
temperatures reached in a high challenge fire are sufficient to
effect a self-drying of the fuel supplying the fire. Moreover,
where the fuel is plastic or plastic wrapped, it is not capable of
being pre-wet by the sprinkler heads around the fire plume and
hence burning proceeds substantially uninhibited.
Another factor to be accounted for occurs where the heat of a
localized high challenge fire establishing a fire column or plume
in excess of 20 feet in height flares out beneath the ceiling of
the protected space and actuates numerous sprinkler heads located
at such a distance from the fire that they are ineffective to
deliver water or other extinguishant to the fuel surfaces. This
contributes not only to redundant and flooding use of the water,
but more significantly, robs water from the heads over the fire
where it is needed to extinguish the fire.
It will be apparent, therefore, that conventional automatic
sprinkler systems, though adequate for the protection of buildings
and other spaces with relatively low ceilings, are less effective
in high challenge fire situations where there is adequate ceiling
height for a strong intense fire plume or column to develop.
SUMMARY OF THE INVENTION
In accordance with the present invention the basic approach to
fighting a fire with an automatic extinguishant discharge system is
changed drastically. The system is designed deliberately to limit
the number of extinguishant discharge heads which will be activated
by a fire. The heads are spaced apart greater distances and have
large outlet orifices to enable greater quantities of water or
other extinguishant to be delivered from each head at lower flow
rates. Preferably, the heads are in the form of wide angle spray
nozzles having 1 inch to 13/4 inch outlet orifices which develop a
downwardly directed spray having large size droplets as compared to
the droplets produced by the conventional one half inch sprinkler
heads.
With this arrangement, the first head actuated by the fire has a
much better possibility of extinguishing the fire because of the
increased ability of the larger droplets to penetrate the fire
plume of a high challenge fire. If the heat of the fire spreads,
additional heads are actuated to help the first head fight the fire
and to wet down areas surrounding the fire to provide exposure
protection to inhibit the spread of the fire. However, the
additional heads which are allowed to be actuated is limited to a
small number to avoid the prior art problems created by too many
heads being actuated; namely, interfering with the fire fighting
capabilities of those heads positioned immediately above the fire
and over the area immediately surrounding the fire, and causing
unnecessary water damage by allowing an excessive number of heads
to be actuated at points remote from the fire.
Extensive fire tests have established that the method of the
present invention employing more widely spaced, larger nozzle heads
fights high challenge fires far more effectively. Larger quantities
of water or other extinguishant are delivered to the fire in a
manner to penetrate the fire plume and fight the fire itself in a
more effective manner, and also provide an ample, but not
excessive, amount of exposure protection.
Not only does the method of the present invention improve the fire
fighting performance of automatic extinguishant discharge systems,
it also results in significant cost savings. The cost of automatic
extinguishant discharge systems can be broken down into inside the
building costs and outside the building costs. The latter includes
the buried mains for delivering water to the building from a
municipal water supply, and any water tanks and pumping equipment
which may be needed to augment the municipal water supply. These
tanks are large gravity feed tanks, or suction tanks having the
necessary pumping equipment for pumping the water from the tank to
the heads. The size and cost of these tanks increase in rural areas
which do not have municipal water available.
In accordance with the method of the present invention, outside the
building costs are reduced significantly because the water supply
capacity is designed to provide sufficient water for the limited
number of heads which will be actuated by a high challenge fire,
rather than, as in prior art systems, designed to provide
sufficient water for about 100 or more sprinkler heads supplied
from a single riser. Thus, even though the individual heads of the
system of the present invention deliver larger quantities of water
than individual prior art sprinkler heads, the total water
requirement is much less. The difference will be great enough in
many cases to enable municipal water to be used for supplying
automatic extinguishant discharge systems for certain size and type
buildings without the need for auxiliary equipment to increase the
water capacity. Obviously, eliminating the need for a large water
tank and the auxiliary equipment for delivering the water from
these tanks to the buildings will provide considerable cost
savings. For buildings located in rural areas where the municipal
water supply may not be sufficient, considerable savings can still
be realized because a smaller water tank can be used along with
less expensive auxiliary equipment for delivering the water from
the tank.
The method of the present invention also results in considerable
inside the building cost savings. In the preferred embodiment of
the method, the large nozzle heads are spaced apart a greater
distance than prior art systems to reduce the number of branch
lines needed. Also, the riser feeding the branch lines is reduced
to a 4 to 5 inch pipe size with threaded connections, rather than
the flanged joints required for the large pipe sizes used for
risers of prior art sprinkler systems. This not only provides
savings in the cost of the pipe involved, but also savings in labor
costs because less labor is required for installing threaded
piping.
Limiting the number of heads which will be actuated by the fire can
be accomplished in a number of ways. In accordance with a preferred
embodiment a pressure floor is established so that a minimum
pressure must exist at each head before it will open. The system is
designed so that this minimum pressure will not be reached until a
predetermined number of heads have been actuated.
In accordance with another embodiment, the number of heads which
will be actuated is limited by wetting the thermal fuse element of
each head after one of the heads has been actuated. This increases
the temperature required to actuate subsequent heads. The heads
closest to the fire will be elevated to a temperature sufficient to
actuate the heads, but the heads furthest from the fire will not be
actuated. Rather than wetting the thermal fuses, as just described,
small heat shields can be moved into position after one of the
heads has been actuated to shield the thermal fuses of the
remaining heads in a manner to require higher temperatures to
actuate the remaining heads.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic, perspective view of a building having an
automatic extinguishant discharge system employed in the method of
the invention;
FIG. 2 is a plan view of the cross main and branch lines of the
extinguishant discharge system of FIG. 1;
FIG. 3 is an enlarged, cross sectional view of one of the nozzle
heads of the system shown in FIG. 1;
FIG. 4 is a fragmentary view taken on line 4--4 of FIG. 3;
FIG. 5 is a schematic view of a fire extinguishing system
illustrating another embodiment of the method of the invention;
FIG. 6 is a fragmentary cross section taken on line 6--6 of FIG.
5;
FIG. 7 is a graph plotting water density ratios against
corresponding wetted area ratios;
FIG. 8 is en enlarged, cross sectional view of one of the nozzle
heads of the system illustrated in FIG. 5;
FIG. 9 is a plan view taken on line 9--9 of FIG. 8;
FIG. 10 is a lower end plan view taken on line 10--10 of FIG.
8.
FIG. 11 is a schematic view of a fire extinguishing system
illustrating still another embodiment of the method of the
invention; and
FIG. 12 is an enlarged, cross sectional view of the nozzle heads
shown in FIG. 11.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIGS. 1 and 2, a building 10 shown in phantom lines is
equipped with an automatic fixed fire protection system 12
embodying features of the invention. The system comprises a buried
feed main 14 connected to a municipal water supply line 16 for
delivering the extinguishant, in this case water, to a riser 18.
The riser 18 is connected to a cross main 20 which, in turn, is
connected to a plurality of branch lines 22. Each branch line has a
plurality of nozzle heads 24 which are operated automatically in
response to a fire, as will be described, to deliver a downwardly
directed spray of water droplets on the fire. The buried feed main
14 extends beyond the riser 18 and can be connected to risers of
other buildings or, in the case of a large building, to other
risers in the same building. The cross main and branch lines are
suspended near the ceiling of the building in a conventional
manner. The system as thus far described is similar to a
conventional automatic water sprinkler system employing sprinkler
heads.
In accordance with the present invention, large nozzle heads are
used in place of sprinkler heads, and the spacing of the nozzle
heads is greater than the normal 10 foot head spacing of prior art
sprinkler systems. In the embodiment shown schematically in FIG. 1,
the building height is about 30 feet, the nozzle heads on each
branch line are spaced about 15 feet apart, the spacing between
branch lines is about 15 feet, and about 200 nozzle heads are
supplied by the riser 18.
Referring to FIGS. 3 and 4 the construction of one of the nozzle
heads 24 is shown in greater detail. Each nozzle head comprises a
cylindrical body 26 having an internally threaded upward end 28. A
pair of spiral vanes 30 and 32 are fixed within the body 26 for
swirling water flowing downwardly therethrough when the nozzle is
opened as will be described. The vanes 30 and 32 support a hollow
central hub 34 which, in turn, slidably supports a rod 36 having a
piston head 38 fixed on the lower end thereof. A pair of sealing
rings 40 and 42 are positioned about the periphery of the head 38
and sealingly engage the wall of the outlet orifice 43 in the
reduced lower end portion of the nozzle body 26.
The rod 36 is latched in the position shown in FIG. 3 by a rod 44
which extends slidably through an externally threaded boss 46
projecting from the side of the body 26. The left end of the rod 44
extends through the vane 32 and the wall of the central hub 34 into
a slot 48 in the rod 36 to latch it in the position shown in FIG.
3.
A sleeve 50 is threaded on the end of the boss 46. The outer end of
the sleeve is closed off by an externally threaded stub shaft 52
having a ring or yoke 54 thereon. The rod 44 slidably extends
through the stub shaft 52 and the right end thereof engages a
conventional thermal fuse element 56 positioned within the ring 54.
The fuse element prevents movement of the rod 44 to the right, as
will be described, until the heat of a fire fuses the element 56 so
that it collapses. Since the thermal fuse element 56 is the
standard type commonly used in conventional sprinkler heads now on
the market, it will not be described in greater detail.
The rod 44 has a piston head 58 mounted thereon which slidably
engages the internal wall of the sleeve 50. A spring 60 is
positioned between the piston head 58 and the end of the stub shaft
52 to bias the piston head and rod 44 to the left with a
predetermined biasing force. A passage 62 is formed in the boss 46
to communicate the space on the left side of the piston head 58
with the interior of the valve body 26. This allows the system
water pressure which is about 40 psi. to bias the piston head 58 to
the right against the opposing spring force to exert a positive
pressure on the thermal fuse element 56. With this arrangement, the
rod 44 will be driven to the right as soon as the fuse element 56
collapses in response to the heat of the fire to unlatch the rod
36. This enables the system pressure to act on the piston head 38
to expel it and the rod 36 from the nozzle and allow the water to
spray out through the outlet orifice 43. If the system pressure in
the nozzle 26 drops below a predetermined minimum pressure level,
as will be described in greater detail hereinafter, the biasing
force of the spring 60 will maintain the piston head 58 and rod 44
in the position illustrated in FIG. 3 against the force developed
by the reduced water pressure so that the rod 36 will not be
unlatched when the thermal fuse element 56 collapses. Consequently,
even if the heat of the fire is sufficient to collapse the thermal
fuse element 56, the nozzle 26 will remain closed until or unless
the system water pressure in the nozzle exceeds the minimum
predetermined pressure level to overcome the spring 60 and move the
rod 44 to the right to unlatch the rod 36.
The lower end 64 of the valve body 24 extends downwardly to form a
square end with four notches 66 at the corners thereof (three of
which are visible in FIG. 3). The transformation of the circular
outlet orifice 44 into a squared end portion, in combination with
the swirling of the water produced by the vanes 30 and 32 produces
a downwardly directed, solid cone, square spray pattern in a well
known manner.
Referring again to FIGS. 1 and 2, good municipal water systems
commonly provide 40 to 50 pounds of water at the main 16. With this
in mind the riser 18, in accordance with the present invention,
would employ 4 to 5 inch piping, the cross main 20 would employ 3
to 4 inch piping and the branch lines 22 would employ 2 to 3 inch
piping. The outlet orifice 43 (FIG. 3) of each of the nozzle heads
24 would be about 1 inch to 1 3/4 inches in diameter. With this
arrangement the system of the present invention is designed to
provide a minimum flow through the riser 18 of 550 gallons per
minute and a maximum flow of 750 gallons per minute when 7 to 12
nozzle heads are opened.
In the specific embodiment shown in FIG. 1, the pressure supplied
by the municipal water main 16 is 40 psi., the riser 18 is made of
4 1/2 inch piping, the cross main 20 is made of 3 1/2 inch piping,
the branch lines 22 are made of 2 1/2 inch piping, and the outlet
orifice 44 of each of the nozzle heads 24 is 1 3/8 inches in
diameter. The spring 60 (FIG. 3) of each of the nozzle heads 24 is
designed to hold the piston head 58 in the position shown in FIG. 3
after the thermal fuse element 56 collapses if the static water
pressure in the unopened nozzle heads 24 drops below 10 psi. static
pressure.
HIgh challenge fire tests conducted with the system 12 designed as
just described, established that about seven heads will be actuated
by a high challenge fire starting in a typical manner. Each head
will provide about 100 gallons per minute of water at about 10 psi.
dynamic (flowing) pressure and will cover a floor area of about 225
square feet. The individual branch lines carry about 300 gallons
per minute when three heads are operating on each branch line. The
remaining heads on the same branch line will not be operating
because the static pressure level at each of these heads will be
below the aforementioned minimum static pressure floor.
With the head arrangement shown in FIGS. 1 and 2, the
aforementioned seven heads will cover a total area of about 1,575
square feet. With the system of the present invention, it is
assumed that the fire will not get beyond the 1,575 square foot
area before the seven heads are on, and that no fire will be able
to get beyond the 1,575 square foot area after these heads are on.
This is based on testing experience which shows that a typical high
challenge fire occupies less than 100 square feet of floor area
when the first head opens.
The system 12 functions automatically to provide useful water flow
to the heads over and around the fire with a minimum water density
of 0.15 gallons per minute per square foot of floor area. At the
same time, the system denies water to unopened heads if the static
pressure at these heads is below the minimum pressure floor,
because the opening of these heads would jeopardize the fire
fighting capability of the heads which have already been opened.
This also avoids wetting remote floor areas to cause unnecessary
water damage as in prior art systems. Thus, no matter how many
thermal fuse elements 56 collapse due to the heat of the fire, the
system 12 will provide sufficient water to supply the nozzles in
the best position to actually fight the fire and provide useful
exposure protection by wetting areas immediately surrounding the
fire. This is accomplished with a 4 1/2 inch riser 18 having a
maximum water flow rate of about 700 gallons per minute.
Referring to FIG. 5, a fire extinguishing system 100 is shown which
illustrates another embodiment of the invention. The system is
depicted as installed in a building space generally designated by
the reference numeral 110 and defined by a floor 112 a ceiling 114
and side walls 116. The stacks of piles bearing reference letters
A-G represent combustible material or fuel piles stored within the
space 110 as in a conventional warehouse, storage facility or the
like.
Supported in depending fashion from the ceiling 114 are a plurality
of spaced nozzle heads 118 each having a thermally responsive
fusable element 120 and a discharge orifice 122, as will be
described in greater detail hereinafter. When the ambient
temperature in the vicinity of a fusable element 120 of a head 118
reaches a predetermined point, the discharge orifice 122 on that
head is opened to disperse a solid cone spray S of extinguishant.
The extinguishant is delivered to the respective nozzles by a
riser, cross main and branch lines similar to those illustrated in
FIG. 1. In the schematic showing of FIG. 5, the riser 124 is shown
and one of the branch lines 126 which it supplies.
In this embodiment, the fire extinguishing system 100 incorporates
the additive injection system disclosed in copending application
Ser. No. 864,757, filed on Oct. 8, 1969 and entitled Additive
Injection System. An additive slurry of a water swellable polymer
or gelling agent is injected automatically into a line 130 which
supplies the riser 124 with water from a water supply main 132
through auxiliaries such as cut-off valves and the like. This forms
an ablative gell in the riser 124 as fully disclosed in the
aforementioned copending application, and reference is made to this
application for a detailed description of this injection
apparatus.
In general, however, and as depicted by the legend bearing blocks
in FIG. 5, the injection apparatus operates to sense the flow of
water called for by the opening of a nozzle 118 and to energize a
power source, such as a motor, to pump or inject the additive
through a mixer to the line 130. As fully described in the
aforementioned copending application, the injection system operates
on a no-inject failure mode to insure that at least an adequate
supply of plain water will pass from the water supply main 132
through the line 130, riser 124 and branch lines 126 to the heads
118.
Referring to FIGS. 8-10, the construction of one of the nozzles 118
is shown in greater detail. The nozzle comprises a body 141 having
an inlet portion 142, an intermediate portion 143, and a discharge
portion 144. The inlet portion 142 is internally threaded as at 146
to facilitate attachment to an externally threaded fitting
connected to and depending from the branch line 126. The inlet
portion 142 defines an inlet area which is relatively large
compared to the area defined by the discharge portion 144. This
minimizes pressure losses at the inlet and provides a potentially
large supply of extinguishant to the discharge portion when the
nozzle head is actuated.
A threaded nipple member 170 defining an opening 171 is engaged
with an internally threaded opening 172 in a boss 173 positioned at
the transition between the inlet end portion 142 and the
intermediate portion 143 of the nozzle. The opening 171 is sized to
permit axial movement of a rod 160 relative thereto.
A coupling member 175 having an interior cavity 176, a first
internally threaded opening 177 and a second internally threaded
opening 178 is threadably mounted on the nipple 170. A first
annular member 180, such as a washer, is provided about an
intermediate portion of the rod 160 and rests against a surface 182
defined by the end of the nipple 170. A spring 184, also located
about an intermediate portion of the rod 160, is contained within
the cavity 176 and includes a first end 185 abutting the first
annular member 180 and a second end 186 abutting a second annular
member 187, such as a washer, located about the rod 160. A third
annular member 189 provides a shoulder for retaining the rod 160 in
the latched position shown in FIG. 8 with the spring 184 in a
compressed state. The annular member 189 may constitute an integral
part of the rod 160, or may be eliminated if the head portion 190
of the rod 160 has a diameter which is sufficiently great to
provide a shoulder against which the annular member 187 may
rest.
A conventional fire detector, designated generally at 192,
comprises a housing 193 secured to a base 194 having a threaded
portion 195 in threaded engagement with the mating threads in the
opening 178 of the coupling member 175. The base 194 and the
portion of the housing 193 adjacent thereto together define an
opening 197 for slidably receiving the head portion 190 of the rod
160.
It is an advantage of the system to use conventional fire detectors
for either water discharge systems or ablative gell discharges
systems because such detectors are presently approved by fire
protection agencies, insurance companies, trade associations and
other interested authorities. In this manner, the accumulated
experience and the low cost of the conventional fire detectors may
be used to great benefit. However, this system is not confined to
actuation by either the illustrated thermally actuated device 192
or by known fire detection elements.
A fire responsive element, designated generally as 199, comprises a
first fusable link portion 200 and a second fusable link portion
201 mounted in the housing 193 between a first supporting member
202 and the end of the head portion 190. The element 199 is
designed to forsake its structural rigidity at a predetermined
temperature, thus permitting the head portion 190 of the rod 160 to
extend axially under the influence of the spring 184 thereby
freeing the rod 160 from its restraining influence on a rod 150. In
the absence of a fire or thermal actuation, the transverse shear
strength of the fusable link portions 200 and 201 is sufficiently
great to withstand the force of the spring 184 acting on the rod
160 and thus retain the rod 160 in the position illustrated in FIG.
8.
A fusable nut 205, responsive to a predetermined temperature, is
located adjacent to a plug 151 in a discharge opening 122 of the
nozzle head. The fusable nut 205 provides a safeguard against the
expulsion of rod 150 in the event that the fusable link 199 is
inadvertently actuated. It also prevents an accumulation of dirt
and grime in the discharge opening 122 which may otherwise affect
the expulsion of the rod 150 from the nozzle head in the event of
fire.
If both the fusable element 199 and the fusable nut 205 have been
thermally actuated, the nozzle head is opened to permit the
extinguishant to be discharged from the discharge opening 122 in a
predetermined spray pattern. A fusing of the link portions 200 and
201 permits the rod 160 to be displaced axially by the force of the
spring 184 exerted through the member 187 against the shoulder of
the annular member 189. The limited axial movement of the rod 160
is sufficient to free the protuding end portion 161 from its
engagement with an opening 162 in the expellable rod 150. The
pressure of the extinguishant against the plug 151 causes the plug
and rod 150 to be expelled from the discharge opening 122.
A pressurized bellows assembly, designated generally at 206 is
provided which comprises a fixed member 207 secured to a pair of
accordion bellows members 208 and 209 which, in turn, are secured
to an axially displaceable movable member 210. The accordion
members 208 and 209 define a closed annular cavity 215 which
contains a predetermined quantity of compressable material, for
example, an inert gas. When the pressure of the extinguishant at
the inlet to the nozzle head is at its maximum for the system, for
example, when no other nozzle heads have been actuated, the volume
of the closed cavity 215 is at a minimum since the pressure within
the cavity seeks to balance the inlet pressure of the
extinguishant. Under this condition, the distance between the fixed
member 207 and the movable member 210 is at a minimum, permitting a
maximum flow of extinguishant to the nozzle orifice 212 through the
passage designated generally at 213.
When the inlet pressure of the extinguishant decreases, for
example, from increased demands on the system by the actuation of
other nozzle heads, the flow modulating assembly 206 operates to
achieve a hydrostatic balance. Since the quantity of compressable
fluid in cavity 215 is fixed, the volume of the cavity increases
until the pressure exerted from within the cavity is equal to the
pressure of the extinguishant on the exterior of the cavity.
Because the cavity 215 is incapable of circumferential expansion,
the distance between the fixed member 207 and the movable member
210 increases to a maximum, thus constricting the effective
discharge passage 213 leading to the nozzle orifice 212. When the
passage to the nozzle orifice is thus constricted, the flow rate of
extinguishant is reduced, so that the spray pattern of the
extinguishant from the nozzle head is maintained. Also, the inlet
pressure to the nozzle head is increased to maintain a higher inlet
pressure to the overall system.
Referring to FIG. 10, a plurality of radially extending, generally
V-shaped notches 219 are in communication with the discharge
opening 122 and with the exterior of the nozzle head. The extent of
the spray pattern produced by the nozzle head is determined by the
maximum width of the notches, the depth of the notches, the flow
rate of the extinguishant and the like. These notches, in
combination with the swirling produced by swirling vanes 147,
produce a rectangular, downwardly diverging pyramid shape spray
pattern indicated by the phantom lines z in FIG. 6. Although this
particular rectangular or square configuration of the spray is not
essential, it is desirable that the area developed at the
intersection of the spray with the horizontal plane define a
polygon capable of complementing adjacent similarly configured
areas.
In the event the inlet pressure falls below a predetermined level,
the movable member 210 closes off the nozzle orifice 212 to prevent
flow of extinguishant even though the thermal fuse element has been
collapsed to unlatch the rod 150. As described in connection with
the first embodiment, this pressure can be set slightly below 10
pounds static pressure. As will be described in greater detail
hereinafter, this keeps the total demand for extinguishant from the
supply system within the capabilities of the system.
To facilitate clearer understanding of the fire extinguishing
system 100 of FIGS. 5 and 6 reference is made to the graph in FIG.
7. In the graph, the ratio of actual delivered density of the
extinguishant to the design or optimum density is assigned
numerical values on the ordinate, whereas the ratio of actual area
of coverage to design or optimum area of coverage for a nozzle head
operating under given conditions of orifice size and line pressure
is indicated numerically on the abscissa. A curve on the graph is
plotted for a single nozzle head delivering extinguishant at
uniform flow rates. Thus, at the point O on the curve X, where
actual to design density and actual to design area of coverage are
at unity, optimum efficiencies are achieved in terms of nozzle
operation corresponding to design parameters. If however the actual
area increases relative to the area for which the nozzle is
designed, the ratio of actual to design densities falls off quickly
as indicated by that portion of the curve to the lower right of the
point O. On the other hand, where the ratio of actual area covered
to design area of coverage is less than 1, the actual density
relative to design density increases quite shrply as indicated by
the curve above the point O. In terms of the curve illustrated in
FIG. 7 therefore, the system 100 departs from traditional fixed
fire extinguishing systems of the type heretofore available by
operating each nozzle in the portion of the curve to the upper left
of the point O, or in a manner such that any error or departure
from design parameters is towards the side of increasing the
density of extinguishant reaching the fuel surfaces even though
some area of coverage may be sacrificed.
The manner in which the principles expressed by the curve in FIG. 7
are carried out in practice according to the present invention may
be seen by reference to FIGS. 5 and 6 of the drawings. As
previously indicated, each of the nozzles 118 delivers a downwardly
diverging pyramid shaped spray S, the angle of divergence being
designated in FIG. 5 by the reference letter .alpha.. As the spray
intersects a horizontal reference plane depicted by the dashed line
P in FIG. 5, it establishes in the reference plane an area of
coverage Z or an area of head responsibility as shown in FIG. 6 of
the drawings. It is important that the reference plane P be
selected so that it lies at or near the upper most surface of fuel
within the space 110 to be protected, and that the perimeters of
the areas of responsibility Z for each nozzle be spaced for the
perimeters of corresponding areas for adjacent nozzles as may be
seen in FIGS. 5 and 6 of the drawings. Such spacing or underlap
between the area Z may vary depending on the spray angle .alpha. of
the nozzles 118. For example, if the spray angle is less than
90.degree. the spacing between the areas or the underlap may be in
the order of 1 1/2 feet whereas if the spray angle is more than
90.degree. the underlap may be increased to the order of 2 1/2
feet. While the precise maximum spray angle .alpha. may vary
somewhat depending upon the height of the space to be protected,
the maximum spray angle to be used for most efficient operation of
the system 100 is 140.degree. for each nozzle head.
In the operation of the system, assuming a fire develops in the
fuel pile B, the temperature above the burning fuel will increase
quickly to release the fuse 120 on the nozzle head directly above
the pile B. Because the density of the spray S from the actuated
nozzle head is designed for the highest fuel pile in the space 110,
extinguishant at densities at least as great as the designed
density will be delivered directly down on the pile to extinguish
the fire. Should a fire develop in a lower pile such as, for
example, the pile A as shown in FIG. 5 of the drawings, the
extinguishant is reaching the pile A from the same head will be at
a substantially lower density due to the spread of the
extinguishant as it falls downwardly. Because the lower height of
the pile A constitutes a significantly lower fire hazard as
compared with the pile B, the fall off in density will be of little
consequence in terms of extinguishing the fire.
Referring to FIG. 11 of the drawings, a fixed fire extinguishing
system 300 is shown which illustrates still another embodiment of
the invention. The system 300 includes a plurality of nozzle heads
310a -310f positioned in spaced relation below a ceiling 312 of an
enclosed space 314 being protected by the system. In conventional
fashion, nozzles 310 are supplied by a fluid extinguishant such as
water from a municipal water main (not shown) through a riser,
cross main and branch lines as previously described. In the
schematic showing of FIG. 11, a riser 316 is shown along with one
of the branch lines 318. The system is maintained with an
extinguishant under pressure designated by the arrow P. Each of the
nozzles 310 is maintained in a closed position under the control of
a fire responsive element 322 as will be described in more detail
hereinafter.
For purposes of illustration, the space 314 shown in FIG. 11
contains combustible material or fuel piles designated by the
reference letters F. As in the previous embodiments, when a fire
exists within the space, the heat rising therefrom will be sensed
by the fire responsive element 322 associated with the head or
heads 310 immediately above the fire to bring about actuation of
the system. Hence, the development of a fire in the fuel piles
beneath the head 310b, for example, will actuate that head to
disperse extinguishant directly down on the fire. Depending upon
the magnitude of the fire and particularly the magnitude of the
heat generated thereby, a certain amount of time will elapse
between the start of the fire and the actuation of the head 310b
and then the heads 310a and 310c to bring about its
extinguishment.
With smaller fires, it is possible that the activation of only a
few heads will deliver a sufficient amount of extinguishant to
extinguish the fire. With larger fires, however, where an extreme
amount of heat is developed, the circulation of the heat by
convection within the space 314 as depicted by the arrows H in FIG.
11 will actuate heads positioned remotely from the actual fire,
such as for example, the heads 10e and 10f. Quite obviously, the
actuation of such remote heads will have little or no effect upon
the extinguishment of the original fire and moreover will reduce
the pressure available for those heads already dispersing
extinguishant to the fire in such a manner that the overall system
is rendered ineffective to extinguish the fire. The nozzle heads
310 are specifically designed to inhibit the activation of remotely
located heads and thus overcome this problem.
Referring to FIG. 12, the construction of one of the nozzle heads
310 is shown in detail. It can be observed that it is basically the
same nozzle shown in FIG. 8 with a pressure actuated heat shield
added thereto. Briefly, the nozzle comprises a body 324 having an
inlet 326 adapted to be connected directly to a conduit 320 (FIG.
11) extending downwardly from the branch line 318. An outlet
orifice 328 at the lower end of the body is normally closed by an
expellable plug 330 mounted on the lower end of a rod 332. A
transversely slidable rod 334 latches the rod 332 against
displacement from a discharge orifice 328 under the influence of
line pressure. Swirling vanes 336 and a pressure responsive bellows
338 are provided as previously described in connection with the
nozzle 118 of FIG. 8. The rod 334 is held against the bias of a
compression spring 340 acting on a collar 342 secured on the rod by
a collapsable linkage assembly including arms 344 secured against
collapse by a fusable link 346, the latter assembly itself being
well known in the fire sprinkler art.
When temperature in the vicinity of the fusable link 346 reaches a
predetermined point, the linkage including the arms 344 collapse
out of the way, permitting the spring 340 to move the rod 334 out
of engagement with the rod 332 to open the discharge orifice of the
head 328, assuming of course that the pressure at the inlet orifice
326 is high enough to prevent the bellows 338 from closing the
outlet orifice 328 as previously described in connection with the
nozzle head 118 of FIG. 8.
The temperature at which the fusible link 346 is released is made
dependent on line pressure by means of a heat shield 348 which can
be moved between the dotted and full line positions as shown. The
heat shield 348 is supported on one arm of a bell crank 350 pivoted
from a lug 352 extending from a bushing 354 enclosing the rod 334
and connected to the body 324. The other arm 356 of the bell crank
is formed with a slot 358 which receives a connecting pin 360 on
the end of a plunger 362. The opposite end of the plunger 362
extends within a chamber 364 defined by a cap 365 threaded in a
boss 366 on the body 324 and is connected to a flexible diaphragm
368. A port 370 in the boss 366 places the chamber 364 in fluid
communication with the interior of the body 324 and thus with line
pressure existing at the inlet 326 to the nozzle 310.
A compression spring 372 acting between the cap 365 and a collar
374 on the plunger 362 biases the plunger and the bell crank 350
and the heat shield 348 to the solid line position shown in FIG.
12. Line pressure, in the chamber 364 acting against the diaphragm
368 tends to urge the plunger in a direction opposing the bias of
the spring 372, or to the phantom line position indicated in FIG.
12. Thus, when line pressure existing within the body 324 is
sufficient to overcome the biasing effect of the spring 372, the
heat shield will be held in the position illustrated in phantom
lines in FIG. 12 away from the fusable link 346. When line pressure
drops below about 10 psi. static pressure, the force exerted by the
spring is larger than that developed by fluid pressure acting
against the diaphragm 368 and the heat shield 348 moves to the
solid line position to encircle and shield the fusible link
346.
Initially, the line pressure P (FIG. 11) throughout the system is
at the pressure provided by the municipal water main which, as in
the embodiment of FIG. 1, is about 40 psi. This maintains the heat
shields 348 associated with the nozzle heads 310 in the phantom
line position so that they do not shield the fusible links 346. In
this condition, should a fire develop, each of the nozzle heads in
the system is equally responsive to the temperatures resulting from
the fire. Upon the development of the fire, the head or heads
nearest the fire will be actuated to disperse the extinguishant
downwardly on to the burning fuel surface. If however, the line
pressure at the unopened heads drops below a static pressure of 10
psi., as it may after a certain number of heads are opened, such as
about seven as in the system of FIG. 1, the heat shields are moved
automatically to the solid line position to shield the fusible
links 346 of the unopened heads so as to delay or inhibit actuation
of these heads positioned remotely from the fire.
The heat shield 348 as shown in FIG. 12 is in the form of a metal
trough-like structure capable of deterring the effect of increased
ambient temperatures on the fusible links 346. As an alternative to
the heat shield, the fusible links 346 may be cooled directly by
the drip tube technique disclosed in FIGS. 3-6 of may
aforementioned copending application Ser. No. 885,501. In
accordance with this technique, water from the system is dripped my
on the fusible links 346 when the static pressure at unopened heads
drops below the aforementioned minimum value to cool the fusible
links which then require a higher temperature to fuse them.
From the foregoing, it will be apparent that each of the systems
12, 100 and 300 described above effectively limits or controls the
number of heads which will be actuated by a high challenge fire.
This is accomplished by control means associated with each head, in
addition to the conventional temperature responsive means, for
determining whether the heads will be opened to spray extinguishant
on the fire. This also can be accomplished by control means located
apart from the nozzle heads. For example, a flowmeter could be
mounted on the riser 18 of FIG. 1 to provide an electrical signal
when the flow through the riser reaches the aforementioned 700
gallons per minute when about seven nozzle heads are opened by a
fire. The electrical signal could then be transmitted to suitable
solenoid actuated latch mechanisms associated with each of the
nozzle heads to prevent the unopened heads from opening even if
their thermal fuse elements subsequently are fused by the fire.
Because the number of heads which will open is limited, the 40 psi.
water pressure supplied by the municipal water main 16 of FIG. 1,
for example, is adequate for supplying the branch lines connected
to the riser 18 without having to resort to a gravity or suction
feed tank to provide additional capacity. This results in
significant outside the building cost savings as mentioned at the
outset of this application. The resultant smaller piping with
threaded connections and the reduction in the number of branch
lines reduces the material and labor costs to provide the
aforementioned inside the building cost savings.
Further, the effectiveness of the systems 12, 100 and 300 is
superior to prior art sprinkler systems because these systems put
larger quantities of extinguishant on and immediately around the
fire in large drop sizes which can penetrate fire plumes of high
challenge fires. Also, the unnecessary water damage caused by the
actuation of remotely located heads is eliminated.
As will be seen from the system 100 shown in FIGS. 5-10, the method
of the present invention is well suited for use with ablative fluid
systems. The ablative fluids are thicker than plain water but can
be handled effectively by the large direct spray nozzles disclosed
herein which pass larger quantities of fluid at lower flow rates.
With this type nozzle the ablative fluids produce larger, heavier
droplets having superior fire plume penetrating capability as
compared to plain water. However, should the injection apparatus
fail to inject the slurry additive to the water, the system 100
fails safe by spraying water on the fire in a more effective manner
than prior art sprinkler systems.
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