NZ203374A - Fire extinguishing system pressure controlled valve - Google Patents

Description

4 2 033 7 Frio my-:,.,,,: = .

Complete Specification Filed: Class: srrucrw Publication Date: P.O. Journal, No: !?r.l£ NEW ZEALAND PATENTS ACT, J 953 No.: Date: COMPLETE SPECIFICATION PRESSURE-CONTROLLED VALVES i/w,, CHUBB FIRE SECURITY LIMITED, a British Company of Pyrene House, Sunbury-on-Thames, Middlesex TW16 7AR, England.

C 8 ereby declare the invention for which 2 / we pray that a patent may be granted to «/M, and the method by which it is to be performed, to be particularly described in and by the following statement:- 20337 The present invention relates to fluid pressure-controlled valves and to combined fire detection and extinguishing systems incorporating such valves.

Fire detection and extinguishing systems are known in which the outlet of a container of fire extinguishant stored under pressure is normally kept closed by a pressure-controlled valve having a movable valve member which seats under the differential thrust generated by 10 the application of the stored pressure not only to the "upstream" face of the valve member but also to a control space on the "reverse" side of the valve member where such pressure acts over a larger effective area to oppose the unseating of the valve member. The control space 15 fluidly communicates with a fire detector which is located in the vicinity of the risk to be protected and which, when a fire is detected, is arranged to vent the control space with a consequent reduction of pressure therein sufficient to allow the valve member to unseat so 20 that the extinguishant is automatically supplied through a discharge conduit to the fire.

It is desirable that while a pressure-controlled valve as described above remains in readiness for operation the 25 interior of the container is permanently in communication with the control space to maintain a balance of pressure on the two sides of valve member throughout, and obviate any significant fluctuations in pressure which might otherwise occur in the relatively small volume of the 30 control space eg as the result of normal temperature changes. However, this can lead to undesirable pressure loss from the container through the control space when venting of the latter occurs on operation. Accordingly in one aspect the present invention seeks to provide a fluid pressure-controlled valve suitable for (though not restricted to) the service described above and which in particular is arranged reliably and swiftly to isolate the control space from the interior of the container when 5 the control space is vented - in the context of a fire detection and extinguishing system this is to avoid the risk of depleting the stored pressure required for ejection of the extinguishant.

In this aspect the invention provides a fluid pressure-controlled valve comprising: an inlet port for connection with a source of pressurised fluid; an outlet port for the discharge of said fluid; a valve seat separating said inlet and outlet ports; pressure-responsive means movable 15 within a chamber and including a valve member adapted to engage said valve seat to close the outlet port from the inlet port; the valve member being arranged such that the tendency of fluid pressure applied thereto from the inlet port is to unseat the valve member; a portion of the said 20 chamber defining a control space fluid pressure wherein acts upon the pressure-responsive means with a tendency to seat the valve member; the effective area of the pressure-responsive means over which fluid pressure within the control space acts tending to seat the valve 25 member exceeding the effective area of the valve member over which fluid pressure from the inlet port acts tending to unseat the valve member, whereby in use with equivalent fluid pressures within the control space and inlet port the valve member remains seated; a bleed 30 passage for connection with the source of pressurised fluid and opening through a bleed port in the wall of said chamber so as to communicate the pressure source with the control space when the pressure-responsive means is in the position in which the valve member is seated; and a 2 03 control port opening to the control space for connection with pressure-control means whereby, in use, if the control space is vented through the control port so as to reduce the fluid pressure therein to a predetermined 5 level in relation to the fluid pressure at the inlet port, the pressure-responsive means moves to unseat the valve member; and wherein a portion of the pressure-responsive means, when in the position in which the valve member is unseated, obstructs said bleed port to isolate 10 the control space from the bleed passage.

In a preferred embodiment the pressure-responsive means include a piston slidably sealed in a generally cylindrical chamber and carrying sealing means which when 15 the piston is in the position in which the valve member is seated permit the communication of the bleed port with the control space, but which when the piston moves into the position in which the valve member is unseated sealingly engage the wall of the chamber to isolate 20 the bleed port from the control space. In other embodiments a diaphragm may be employed in place of the piston, the diaphragm permitting the communication of the bleed port with the control space when in the position in which the valve member is seated, but having a portion 25 which seals over the bleed port when the diaphragm flexes to the position in which the valve member is unseated.

The pressure-control means, so-called herein, by which the control space of a valve according to the invention 30 is vented in operation may take any convenient form appropriate to the use to which the valve is put, its essential requirement being that it is effective to achieve sufficient pressure reduction in the control space to initiate operation of the valve when a condition 2A 1 1 7 arises in which discharge of fluid from the pressurised source thereof is required.

In a second aspect the invention resides in a combined 5 fire detection and extinguishing system comprising a container of fire extinguishant stored under propellant fluid pressure and fitted with a pressure-controlled valve as defined above, the inlet port of which is in communication with the pressurised extinguishant, the 10 bleed passage of which is in communication with the pressurised propellant therefor (which may or may not be the same composition as the extinguishant), and the control port of which is in communication with pressure-control means in the form of a fire detector adapted to 15 vent the control space of the valve upon the detection of a fire condition. Fire detection and extinguishing systems in accordance with the invention may be found useful in the protection of a variety of risks, one class of risk with which such a system is particularly suited 20 for operation being deep fat frying troughs and the like equipment.

The invention will now be more particularly described, by way of example, with reference to the accompanying 2 5 drawings, in which: Figure 1 is a vertical section through a pressure-controlled valve in accordance with the invention, as employed in a combined fire detection and extinguishing 30 system; Figure 2 is a section on the line II-II of Figure 1; and 2 0 7 .'1 Figure 3 is a schematic diagram of a typical fire detection and extinguishing system employing the valve of Figures 1 and 2. For ease of illustration the relative positions of the various valve ports P1-P6 in Figure 3 5 differ from the true spatial arrangement of the ports as exhibited in Figures 1 and 2.

The valve 1 shown in Figures 1 and 2 comprises a two-part body 1A,1B threaded at its lower end for engagement with 10 the neck 2A of a container 2 charged with, for example, water, foam solution, dry powder or vaporising liquid fire extinguishant, under the pressure of an inert propellant gas. The valve has a main inlet passage 3 connecting with a dip tube 4 which extends to the lower 15 region of the fire extinguishant container. The passage 3 is also in permanent connection with a port PI, for a purpose to be described hereafter. The outlet port of the valve is indicated at P2 and this is normally closed from the passage 3 by the engagement of the conical head 20 5A of a valve member 5 with a seat 6 surrounding the passage 3. The valve member 5 is in the form of a stainless steel "jumper" which nests in a piston 7 slidable in a chamber 8 formed in the valve body.

The piston 7 carries a pair of 0-rings 9 and 10. The lower 0-ring 10 forms a sliding seal against the wall of the chamber 8 throughout the range of movement of the piston, although this is not the case for the upper Coring 9. Where the two body parts 1A and IB meet each has 30 a chamfered edge so that in this region there is a local increase in the diamter of the chamber 8, defining a shallow annular groove 11A. The lower surface of body part IB is also undercut where it mates with part 1A to 2033 define a second annular groove 11B extending radially outwards from the groove 11A. In the seated position of the valve member 5 as shown in Figure 1 the piston 0-ring 9 lies in the region of the groove 11A and hence does not 5 seal against the chamber wall. A second passage 12 extends through the valve body part 1A in parallel with the passage 3 and at its lower end opens to the ullage space within the container 2. At its upper end this passage has a small-bore restriction 13 which opens into 10 the groove 11B. A control space 14 is defined at the upper end of the chamber 8, ie on the side of the piston 7 remote from the valve member 5, and in the illustrated position of the piston this space communicates with the ullage space of the container 2 through the path provided 15 by the passage 12, restriction 13, groove 11B and groove 11A. A further port P3 opens to the control space 14 for the connection of a fire detector.

In use of the illustrated valve in a fire detection and 20 extinguishing system the outlet port P2 is connected through a tube 17 to a series of discharge nozzles 18 directed at the risk to be protected, exemplified in Figure 3 as a fat fryer 19. The port P3 is connected through a small-bore tube 20 to a fire detector 21 25 sensitive to the temperature in the vicinity of the risk to be protected, the detector comprising eg a fusible link which normally seals the end of the tube 20 but which melts to vent the tube 20 (and thus also the control space 14 in the valve 1} to atmosphere when 30 overheated as the result of a fire in the fryer 19.

Alternatively the tube 20 may itself act as the detector, comprising for example a sealed length of nylon or other heat-destructible material extending in the vicinity of the risk. ^ ^ -<y \j/ «V..- In the normal operational condition of the valve, the control space 14 and the tube 20 are pressurised to the same level as the container 2, and the pressure in the space 14/tube 20 is maintained in balance with the 5 container pressure by virtue of the restricted path 12/13/llB/llA which allows propellant gas to bleed between the container 2 and space 14, thereby obviating any significant fluctuations in pressure which might otherwise occur in the relatively small volume of the 10 control space 14 and tube 20, eg as the result of normal temperature changes, if the control space and tube were sealed off from the container 2. As will be appreciated, the tendency of the fluid pressure continuously applied to the valve member 5 from the passage 3 is to unseat the 15 valve member while the tendency of the pressure applied to the piston 7 from the control space 14 is to seat the valve member. Since the effective area of the piston exposed to the space 14 exceeds the effective area of the valve member exposed to the passage 3, so long as the 20 pressures on the opposing sides of the piston/valve member assembly remain in balance the net thrust on that assembly will always act in the direction to maintain the valve member seated. In a preferred embodiment the effective area ratio between the two sides of the 25 piston/valve member assembly is approximately 4:1.

However, as previously explained, when a fire is detected the tube 20 and space 14 are vented to atmosphere. As a consequence the pressure in space 14 drops rapidly, the 30 restriction 13 permitting an insufficient flow of gas into the space 14 to compensate for the gas escaping through the now-open detector, and the pressure force on the valve member 5 overcomes the reduced pressure force on the opposite side of the piston, to lift the valve 203374 member/piston assembly so that the extinguishant from container 2 is automatically supplied through port P2 and tube 17 to the fire. The conical shape of the valve head 5A assists in directing the flow of extinguishant 5 smoothly through the 90° bend between the passage 3 and port P2. Furthermore, as the piston lifts its O-ring 9 comes into contact with the cylindrical wall of the chamber 8 above the groove 11B so as now to seal the bleed passage 12 from the space 14, thereby preventing 10 any further loss of propellant from the container 2 through the open detector via the space 14.

As shown in Figure 1, the port PI is fitted with a nonreturn valve 2 2 of the kind marketed under the 15 Trade Mark SCHRADER, through which the container 2, space 14 and tube 20 are initially pressurised with propellant gas when commissioning the system. Until this pressurisation is completed the valve member 5 is held on its seat by means of a plunger 23 slidably sealed in a 20 bore 24 in the top of the valve body IB and pressed down on top of the piston 7 by a screw 25 threaded into a continuation 24A of the plunger bore. The propellant (eg air or nitrogen) introduced through the valve 22 passes through the tube 4 to fill the ullage space of the 25 container 2, and thence through the passage 12 to the space 14 and tube 20. When this action has been completed the.screw 25 is removed and the plunger lifts into its position illustrated in Figure 1 under the action of the pressure in space 14. The valve member is 30 now held on i^ts seat by the differential pressure force on the valve member/piston assembly as previously described. A short plug can be screwed into the continuation bore 24A to prevent subsequent tampering with the plunger 23. 2 "?7 > Another port P4 opens from the passage 12 for the connection of a pressure gauge 26.

Two further ports P5 and P6 may optionally be provided in 5 the valve body 1A (see Figure 2), for two further control functions. Each one connects through a respective bore 27,28 with the downstream side of the valve seat 6, so they are normally unpressurised. However, when the valve member 5 unseats to supply the pressurised extinguishant 10 to port P2 in response to the detection of fire, the full container pressure is applied also to ports P5 and P6. In the system exemplified in Figure 3 port P5 connects through a capillary tube 29 with a pressure-responsive device 30 for automatically shutting down the heat source 15 31 of the fat fryer 19 when the valve 1 responds to a fire condition - the device 30 being for example a pressure valve to shut off the fuel supply if the heat source 31 is a gas burner, or a pressure switch to shut-off the power supply if an electric heater is employed. 20 The port P6 connects through a capillary tube 32 with a pressure switch 3 3 which automatically switches power to an electric alarm sounder 34 when the valve 1 responds to a fire condition.

Claims (6)

CO i "1 ^4- 203374 ... . • " : -11- ■WHAT-J/WE CLAIM IS: -CLAIMS

1. A fluid pressure-controlled valve comprising: an inlet port for connection with a source of pressurised fluid; 5 an outlet port for the discharge of said fluid; a valve seat separating said inlet and outlet ports; pressure-responsive means movable within a chamber and including a valve member adapted to engage said valve seat to close the outlet port from the inlet port; the valve member 10 being arranged such that the tendency of fluid pressure applied thereto from the inlet port is to unseat the valve member; a portion of the said chamber defining a control space wherein fluid pressure acts upon the pressure-responsive means with a tendency to seat the 15 valve member; the effective area of the pressure- responsive means over which fluid pressure within the control space acts tending to seat the valve member exceeding the effective area of the valve member over which fluid pressure from the inlet port acts tending to 20 unseat the valve member, whereby in use with equivalent fluid pressures within the control space and inlet port the valve member remains seated; a bleed passage for connection with the source of pressurised fluid and opening through a bleed port in the wall of said chamber 25 so as to communicate the pressure source with the control space when the pressure-responsive means is in the position in which the valve member is seated; and a control port opening to the control space for connection with pressure-control means whereby, in use, if the 30 control space is vented through the control port so as to reduce the fluid pressure therein to a predetermined level in relation to the fluid pressure at the inlet port, the pressure-responsive means moves to unseat the valve member; and wherein a portion of the -■ ff y lh

2^ *"& "7 -12- responsive means, when in the position in which the valve member is unseated, obstructs said bleed port to isolate the control space from the bleed passage. 5 2. A valve according to claim 1 wherein the pressure- responsive means include a piston slidably sealed in a generally cylindrical chamber and carrying sealing means which when the piston is in the position in which the valve member is seated permit the communication of the 10 bleed port with the control space, but which when the piston moves into the position in which the valve member is unseated sealingly engage the wall of the chamber to isolate the bleed port from the control space. 15

3. A valve according to claim 1 or claim 2 comprising a further port opening to said bleed passage to which a pressure gauge is connected.

4. A valve according to any preceding claim comprising a 20 further port opening to said inlet port to which a non return valve is connected to permit pressurisation of said source and said control space from an external agency. 25

5. A fluid pressure-controlled valve substantially as hereinbefore described with reference to Figure 1 or Figures 1 and 2 of the accompanying drawings.

6. A combined fire detection and extinguishing system 30 comprising a container of fire extinguishant stored under propellant fluid pressure and fitted with a pressure-controlled valve in accordance with any preceding claim the inlet port of which is in communication with the pressurised extinguishant, the bleed passage of which is 35 in communication with the pressurised propellant therefor 2 0 3 3 ■7 4 13 • 5 10 15 9. 20 and the control port of which is in communication with pressure-control means in the form of a fire detector adapted to vent the control space of the valve upon the detection of a fire condition. A system according to claim 6 wherein the said valve comprises a further port opening to the outlet side of said valve seat to which is connected pressure-responsive means for initiating an alarm when the valve member is unseated. A system according to claim 6 or claim 7 wherein said fire detector is located in the vicinity of heated equipment and wherein the said valve comprises a further port opening to the outlet side of said valve seat to which is connected pressure-responsive means for interrupting the heat source of said equipment. A system according to claim 6 and substantially as hereinbefore described with reference to Figure 3 of the accompanying drawings.