US3759331A

US3759331A - Fire protection system utilizing dry pipes normally maintained in a vacuum

Info

Publication number: US3759331A
Application number: US00248090A
Authority: US
Inventors: W Livingston
Original assignee: Factory Mutual Research Corp
Current assignee: Factory Mutual Research Corp
Priority date: 1972-04-27
Filing date: 1972-04-27
Publication date: 1973-09-18
Anticipated expiration: 1990-09-18

Abstract

A fire protection system in which a plurality of extinguishant discharge heads are disposed in elevated position in a space to be protected from fire and are connected by a piping system for supplying extinguishant to the heads. Flow of extinguishant to the heads is normally prevented until a predetermined increase in fluid pressure is affected in the piping system in response to a fire condition in the space.

Description

Unite States Patent 1 [111 3,759,331

Livingston 1 Sept. 18, 1973 1 FIRE PROTECTION SYSTEM UTILIZING 2,590,215 3/1952 Sausa 251/5 DRY PIPES NORMALLY MAINTAINED IN A VACUUM Inventor: William L. Livingston, Sharon, Mass.

Factory Mutual Research Corporation, Norwood, Mass.

Filed: Apr. 27, 1972 Appl. No.: 248,090

Assignee:

US. Cl 169/17, 169/20, 169/39 Int. Cl. A62c 35/00 Field of Search 169/1, 3, 5, 16,

References Cited UNITED STATES PATENTS Rider 169/20 Primary Examiner-M. Henson Wood, Jr. Assistant Examiner-Michael Mar Att0rneyJoseph M. Lane et a1.

[57] ABSTRACT A fire protection system in which a plurality of extinguishant discharge heads are disposed in elevated position in a space to be protected from fire and are connected by a piping system for supplying extinguishant to the heads. Flow of extinguishant to the heads is normally prevented until a predetermined increase in fluid pressure is affected in the piping system in response to a tire condition in the space.

9 Claims, 6 Drawing Figures 2 Sheets-Sheet 1 IIIIIIIIIIIF Patented Sept. 18,1973 3,759,331

2 Sheets-Sheet 2 FIRE FROTECTION SYSTEM UTILIZING DRY PIPES NORMALLY MAINTAINED IN A VACUUM BACKGROUND OF THE INVENTION tain the latter in a dry state to prevent possible damage I to the piping system as a result of the water freezing. Upon the occurrence of a fire, the valve is opened and the water flows through the piping system for discharge through the heads.

Several disadvantages are inherent in the use of these type systems. For example, the response time for the water to actually discharge from a head after the occur rence of a fire is relatively high due to the fact that the water must flow a relatively large distance from the valve to the heads before discharge. Also, air which accumulates in the dry portion of the piping system must first be purged out of the system before the water can discharge from the heads. A related problem is that a relatively high water pressure must be available in order to purge the air out, since the air can provide a relatively high resistance to water flow through the piping system.

As a result, delays as great as two minutes can occur between actuation of the system in response to a fire and the actual discharge of the extinguishant from the heads. This delay can often be disastrous, especially in connection with protection involving high challenges, such as in the use of warehouses, or the like.

Attempts have been made to offset this disadvantage by utilizing larger pipes, heads and/or water supplies in order to compensate for the above-mentioned delay. However, it is apparent that the economic consequences of this are often prohibitive.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a dry pipe system which eliminates the above mentioned delay in discharge of the extinguishant after actuation of one or more heads.

It is a further object of the present invention to provide a fire protection system of the above type in which water is continuously discharged from the piping system during inaction of same.

Toward the fulfillment of these and other objects, the present invention comprises a plurality of discharge heads disposed in an elevated position in a space to be protected from fire, a piping system connecting said heads, a source of extinguishant connected to said piping system, control means normally preventing the flow of extinguishant from said source to said heads, said control means being responsive to a predetermined increase in fluid pressure in said .piping system for permitting the fiow of extinguishant to said heads, and means responsive to a predetermined fire condition in said space for causing said predetermined increase in said pressure in said piping system.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic perspective view of a building having the system of the present invention installed therein;

FIG. 2 is an enlarged sectional view showing a portion of the system of FIG. 1;

FIGS. 3 and 4 are enlarged sectional views taken on the lines 33 and 4-4, respectively;

FIG. 5 is a perspective view of a discharge head utilized in the system of the present invention; and

FIG. 6 is an enlarged sectional view taken along the line 6-6 of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. I of the drawings, a building 10 is shown in phantom lines which is equipped with an automatic fixed fire protection system 12 embodying features of the present 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 piping system including a riser 18 connected to a crossmain 20 which, in turn, is connected to a plurality of branch lines 22. Each branch line has a plurality of discharge heads 24 mounted thereon which are operated automatically in response to a fire, as will be described, to deliver a spray of water to 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 crossmain 20 and the branch lines 22 are suspended near the ceiling of the building in a conventional manner.

As shown in FIG. 2, the riser 18 is divided into two portions 18a and 18b which are connected together by means of a pinch valve 26 which will be described in detail later.

A vacuum pump 28 is connected to the riser portion 18a, and a manually operated gate valve 30 is connected to the riser portion 18b. Since the vacuum pump 28 and the gate valve 30 are of a conventional design, they are not shown, nor will be described, in any further detail.

The pinch valve 26 consists of a tubular boot 32 of an elastomeric material which is bolted at each end to flanges formed on the facing end portions of the riser portions 18a and 18b, as shown. One half portion of the boot 32 is maintained in a permanent pre-pinched condition by'means of a fixed pinch bar 34 which is affixed in a permanent position with respect to the riser 18 by means of a pair of

support brackets

36 and 38 which are also bolted to the flange of the riser portion 18b, as shown in connection with the support bracket 36 in FIG. 2.

A movable pinch bar 40 engages a portion of the boot 32 diametrically opposite from that portion enconnecting rod 57 connects the bracket 46 to the diaphragm 54 so that movement of the diaphragm causes a resultant movement of the bracket and therefore the pinch bar 40. A conduit 53 communicates the interior of the riser portion 16a with the chamber 56 for reasons that will be explained in detail later.

A valve 66 is associated with the actuator and is shown in detail in FIG. 4. The valve 6comprises a tubular insert 62 disposed in the wall of the housing 52 of the actuator 54 and having an arcuate flange portion formed on its inner wail to define a valve seat 64. A valve plunger is provided in the tubular insert 62 and consists of a disc-like valve head 66 adapted to seat on the valve seat 64, and a valve stem 68 connected at one end to the valve head 66 and supported for slidable movement within the tubular insert 62 by means of a support strut 70. A compression spring 72 extends between the valve head 66 and the support strut 70 to urge the valve head in a direction to the right as viewed in F IG. 4.

The details of each discharge head 24 are shown in FIGS. and 6. Each head consists of a base member 72 having a relatively large central opening 74 and several relatively small vent openings 75 extending therethrough, for reasons to be explained in detail later. A tubular fixture 76 projects from the upper surface of the base member 72 and registers with the central opening 74. The fixture 76 is externally threaded for connection to a branch line 22 of the fire protection system. A pair of spaced

circular flanges

78 and 80 are formed on the bottom surface of the base member 72, with the flange 78 being slightly greater in height than the flange 80. It is understood that the head 24 can be provided with a device, such as a swirl vane (not shown), or the like, for imparting a swirling action to the water as it discharges through the outlet defined by the central opening 74 of the base member 72, in a conventional manner.

A circular snap disc 82 extends over the outlet of the discharge head 24 defined by the central opening 74 and seats on the

flanges

78 and 80 in order to seal off the vent openings 75. The snap disc 82 is not flat but is normally biased by its own internal spring force to a position shown by the dashed lines in FIG. 6, while being adapted to attain an inverted position against this internal spring force as shown by the solid lines.

A yoke 83 is supported by, and extends downwardly from, the base member 72 and supports a pair of substantially T-

shaped lever arms

84 and 86. One projecting portion of the lever arm 84 engages the disc 82 to force it into the position shown by the solid lines in FIG. 6, while one projecting portion of the lever arm 86 is supported by the apex of the yoke 83. The other projecting portions of the

lever arms

84 and 86 engage each other, while the ends of the lever arms are engaged by a fusible link 90 extending thereover in a manner to apply a force to the lever arms of a sufficient amount to maintain them in the position shown. The fusible link 90 may be of any standard material which is adapted to fuse, or melt, at a predetermined elevated temperature, such as 286F. and release its engagement with the

lever arms

84 and 86.

In operation of the system of the present invention, the valve' 30 is manually closed and the system drained so that the riser portion 18a, along with the remainder of the piping system including the crossmain and the branch lines 22, are placed in a dry state, with the heads 24 being connected to the branch lines 22 in their position shown in FIGS. 5 and 6.

The vacuum pump 28 is then actuated in order to maintain the pressure in this dry portion of the system between a predetermined range such as between 11 pounds per square inch (hereinafter referred to as psi) and l2 psi. This negative pressure is imparted to the chamber 56 via the conduit 58, and the design of the pinch valve 26 and the actuator 50 are such that the latter pressure causes the diaphragm 54 and therefore the movable pinch bar 40 to move in the direction indicated by the arrows in FIGS. 2 and 3, with the pinch bar 40 thus compressing the tubular boot 32 to the position shown by the dashed lines in FIGS. 2 and 3. As a result, the pinch valve 26 operates to prevent water flow from the riser portion 38b to the riser portion 18a. The valve 30 is then opened to permit the water to flow to the immediate vicinity of the closed pinch valve 26. The system is then left in this condition in the space to be protected.

Upon a fire condition occurring in the space of a magnitude that causes a fusion of the fusible link 90 of one or more discharge heads 24, the link will release the

lever arms

84 and 86 from their engagement between the yoke 83 and the snap disc 82. As a result, the snap disc 82 will snap to the position shown by the dashed lines in FIG. 6 by virtue of its internal spring force, with the vacuum occurring in the system initially maintaining the disc against the flange 78. As a result, atmospheric pressure will be admitted into the system through the vent openings in the base member 72. This atmospheric pressure, which for the purpose of example will be assumed to be approximately 14.7 psi, will increase the pressure in the system to an extent that the vacuum pump 28 will not be able to maintain a sufficient negative pressure in the chamber 56 to maintain the valve 26 in its flow preventing position. As a result of this increase in pressure in the chamber 56, the force exerted by the, water pressure acting on the closed boot 32 will be sufficient to move the boot in a direction opposite to that shown by the arrows in FIGS. 2 and 3. As a result, water will immediately flow into the riser portion 18a and into the crossmain 20 and the branch lines 22 for discharge through the head or heads 24 that were previously opened.

It can be appreciated that the pinch valve 26 opens at a relatively fast rate due to the force of the water pressure acting on the boot 32 as well as the rapid deterioration of the negative pressure in the chamber 56. Also, once the water passes the pinch valve 26, it incurs very little resistance to flow due to the absence of any appreciable air pressure or the like in the dry portion of the system due to the existence of the negative pressure.

In order to provide an even more rapid opening of the pinch valve 26, the valve 60 comes into operation. In particular, the force exerted on the valve head 66 by the compression spring 72 can be designed so that the valve head will move to the opened position shown by the dashed lines in FIG. 4 in response to a slight rise in the pressure in the dry portion of the system as a result of the opening of one or more heads 24. As an example of the latter, assuming that the vacuum pump maintains the pressure in the dry portion of the system at an upper limit of -11 psi, and that the atmospheric pressure acting on the exposed surface of the valve head 66 is 14.7 psi, the compression spring 72 can be designed to exert an effective pressure of 25 psi on the valve head 66 which, during inaction of the system, is insufficient to open the valve head. However, when the pressure in the dry portion of the system rises to a predetermined value above ll psi, such as to l0 psi, in response to the actuation of one or more heads 24, the 25 psi pressure exerted by the spring 72 will be sufficient to open the valve head 66. As a result, atmospheric pressure will rush directly into the chamber 56 and accelerate the deterioration of the negative pressure therein and thus increase the rate of movement of the pinch valve 26 to the open position asdiscussed above.

it can be appreciated that the system of the present invention eliminates any appreciable delay in discharge of extinguishant after actuation of one or more heads and therefore provides a substantial improvement over prior art dry pipe systems.

Also, the system of the present invention insures that the dry portion of the system is in fact maintained in a substantially completely dry state during inaction of the system due to the presence of the vacuum pump.

Of course, variations of the specific construction and arrangement of the system disclosed above can be made by those skilled in the art without departing from the invention as defined in the appended claims.

I claim:

1. A fire protection system comprising a plurality of discharge heads disposed in an elevated position in a space to be protected from fire, a piping system connecting said heads, a source of extinguishant connected to said piping system, means for normally maintaining the fluid pressure in said piping system below a predetermined maximum value, control means normally preventing the flow of extinguishant from said source to said heads, said control means being responsive to an increase in said fluid pressure above said maximum value for permitting the flow of extinguishant to said heads, and means responsive to a predetermined fire condition in said space for causing said increase in said 6 fluid pressure.

2. The system of claim 1 wherein said predetermined maximum value of said fluid pressure is atmospheric pressure.

3. The system of claim 1 wherein said means for causing said increase in said pressure comprises means for venting said piping system to atmosphere.

4. The system of claim 3 wherein said venting means comprises a venting assembly associated with each of said heads.

5. The system of claim 4 wherein each venting assembly comprises a spring loaded cap extending over the outlet of its respective head, a thermal link normally maintaining its respective cap in an extinguishant discharge preventing position relative to said outlet, each of said links adapted to release its respective cap in response to said predetermined fire condition, whereby said cap moves from said extinguishant discharge preventing position to a venting position by virtue of its spring force.

6. The system of claim 1 wherein said means for normally maintaining the fluid pressure in said piping system below a predetermined maximum value comprises a vacuum pump connected to said piping system.

7. The system of claim 1 wherein said control means comprises a pinch valve disposed in said piping system, and an actuator responsive to the pressure in said piping system being below said predetermined maximum value for closing said valve, and responsive to said increasein pressure for opening said valve.

8. The system of claim 7 wherein said means for causing said increase in said pressure comprises means for venting said piping system to atmosphere.

9. The system of claim 7 wherein said actuator comprises a housing, a diaphragm defining a chamber in said housing and movable in said housing in response to fluid pressure variations in said chamber, means connecting said diaphragm to said pinch valve, and means communicating said chamber with said piping system.

Claims

1. A fire protection system comprising a plurality of discharge heads disposed in an elevated position in a space to Be protected from fire, a piping system connecting said heads, a source of extinguishant connected to said piping system, means for normally maintaining the fluid pressure in said piping system below a predetermined maximum value, control means normally preventing the flow of extinguishant from said source to said heads, said control means being responsive to an increase in said fluid pressure above said maximum value for permitting the flow of extinguishant to said heads, and means responsive to a predetermined fire condition in said space for causing said increase in said fluid pressure.

7. The system of claim 1 wherein said control means comprises a pinch valve disposed in said piping system, and an actuator responsive to the pressure in said piping system being below said predetermined maximum value for closing said valve, and responsive to said increase in pressure for opening said valve.