GB2280368A

GB2280368A - Fire sprinkler systems

Info

Publication number: GB2280368A
Application number: GB9315715A
Authority: GB
Inventors: Bernard Cain
Original assignee: Project Fire Engineers Ltd
Current assignee: Project Fire Engineers Ltd
Priority date: 1993-07-29
Filing date: 1993-07-29
Publication date: 1995-02-01
Anticipated expiration: 2013-07-29
Also published as: GB9315715D0; GB2280368B

Abstract

System has break tank means for water supplied to the system from a water main, at least one sprinkler, and pump means for supplying water from the break tank means to the sprinkler or sprinklers, the pump means being arranged to he operated so as to provide for supply of water to the sprinkler(s) at a flow rate substantially not greater than a predetermined flow rate.

Description

TITLE: Fire Sprinkler Systems Description of the Invention This invention relates broadly to fire sprinkler systems, and more particularly to the supply of water to fire sprinkler systems from water mains.

Fire sprinkler systems are well established as an effective means for the protection of buildings from fire. Sprinkler systems are also used for the fire protection of industrial plant and machinery installations, whether or not such installations are disposed within buildings. A typical sprinkler system includes a number of suitably positioned sprinklers of a type which is caused to commence operating upon detection, e.g. by melting of a fusible element, of the existence of a temperature of a predetermined level higher than normal ambient temperatures encountered at the sprinkler location, and the necessary pipes for supplying water to the sprinklers.

It is usual to supply a sprinkler system with water from a water main.

It is of course essential that the main should be able to supply water to the system at sufficient pressure to ensure satisfactory operation of the sprinklers and at a flow rate (volume . time) to supply all the sprinklers which have been brought into operation. It will be appreciated that for many fires not all the sprinklers of a system will be brought into operation as the operation of a sprinkler or sprinklers first brought into use will prevent spread of the fire beyond the area protected by such sprinkler(s).

One problem with the supply of water from mains to sprinkler systems is that water supply authorities are endeavouring to reduce mains water pressure to the minimum value which they are legally obliged to supply. The purpose of such reduction in pressure is to reduce waste of water by leakage from mains.

Whilst the ability of most mains is still adequate to meet the flow rate requirements of sprinkler systems, in many cases the pressure will no longer be sufficient for satisfactory operation. A further problem with reduction of mains pressure is that it is common to provide sprinkler systems with a means for detecting when one or more sprinklers are brought into operation by identifying a drop in pressure which occurs at a point or points in the system when one or more sprinklers commences operation. Such identification of sprinkler operation evidenced by pressure drop is used to provide an automatic signal to call out the fire brigade to the premises concerned. Reduced mains pressure can lead to false alarms which clearly is undesirable.Some water supply authorities bring in additional pumping machinery to increase mains pressure when there is a fire, but whilst this solves the problem of satisfactory sprinkler operation it does not eliminate the problem of false alarms if the prevailing mains pressure at normal times is low.

The standard method of providing a sprinkler system when mains pressure is low is to install a relatively large water storage tank and pumps to supply the sprinklers from such tank. The difficulty then is the necessary building and installation work for the tank and the space occupied thereby. Such a system incorporating a large storage tank is expensive.

It is broadly the object of the present invention to overcome or reduce the problems above described. Other objects and advantages of the invention will be pointed out more particularly hereafter.

According to one aspect of the present invention, we provide a fire sprinkler system comprising: means for connection to a water main, for supply of water to the system; break tank means for receiving said water; at least one sprinkler; and pump means for supplying water from said break tank means to said at least one sprinkler; wherein said pump means is arranged to be operated so as to provide for supply of water to said at least one sprinkler at a flow rate substantially not greater than a predetermined rate. Preferably said predetermined rate is the minimum sustainable flow rate of water available from said main.

According to another aspect of the present invention, we provide a method of operating a fire sprinkler system comprising means for connection to a water main, for supply of water to the system; break tank means for receiving said water; at least one sprinkler; and pump means for supplying water from said break tank means to said at least one sprinkler; said method comprising operating said pump means so as to supply water to said at least one sprinkler at a flow rate substantially not greater than a predetermined rate.

Preferably said predetermined rate is the minimum sustainable flow rate of water available from the main. Such minimum sustainable flow rate may be ascertained by enquiry of the water supply authority, by carrying out a test, or possibly by the provision of a device which is able to assess continuously or at intervals what is the minimum sustainable flow rate of water available from the main.

In a system according to the present invention, because the delivery of the pump means is substantially not greater than the ability of the water main to supply water, there is no need for a storage tank of high capacity. Whilst the break tank means of a system according to the invention provides storage for a quantity of water, such quantity can be relatively small, e.g. of the order of 2 cubic metres.

Preferably the system includes means for measuring the pressure and/or flow rate of water in a pipe leading to the at least one sprinkler, and means for controlling operation of the pump means in accordance with the flow rate and/or pressure thus measured.

The pump means preferably includes a pump operable to pressurise water in said pipe leading to the at least one sprinkler when no sprinklers are in operation, change of such pressure in the pipe providing an indication of operation of the bringing into operation of a sprinkler or sprinklers.

For supply of water to the sprinkler or sprinklers when in operation, the pump means may include a number of pumps, for example three, of which one or more are arranged to be brought into operation according to the number of sprinklers operating. Typically 90% of fires likely to occur in an area covered by a sprinkler system according to the invention will bring only one or a small number of sprinklers into operation whose water demand can be met by one pump. With three pumps, there are then two pumps in reserve. 95% of possible fires will bring into operation a number of sprinklers whose water demand can be met by operation of two pumps, whilst the operation of three pumps will meet the water demand of sprinklers operated by 98% of possible fires.Whilst it is always possible that a large fire could break out, bringing into operation a large number of sprinklers whose water demand cannot totally be met by three pumps, the possibility is remote and in any event such a fire is likely to be of greater severity than could be dealt with by a sprinkler system alone.

The break tank means preferably comprises a tank provided with a valve means operated in response to level of water in the tank, to control delivery of water from the main to the tank. Such valve means may comprise a float controlled valve or valves. The arrangement preferably provides a means whereby, as is usually required by water supply authorities, the possibility of flow back into the main, of water which has entered the tank, is eliminated.

Preferably the system includes means for providing an alarm signal in response to the operation of one or more sprinklers. Such means may comprise means for detecting a drop in pressure at a point of the system leading to one or more sprinklers, and means for detecting flow of water leading to the one or more sprinklers.

When a sprinkler operates, two conditions exist in consequence, one being a drop in pressure at the part of the system leading to the sprinkler or sprinklers and the other being a flow of water at such point at least equal to the flow through one sprinkler. When these conditions are established, the alarm signal may be given. A call out signal may be automatically sent to the fire brigade.

Preferably the system includes means for testing its satisfactory operation. Such means for testing the system may comprise means for simulating the bringing into operation of a sprinkler and means for checking to ensure that operation of the pump means follows, as above described.

Preferably the means for simulating operation of a sprinkler comprises means for releasing water from the pipe leading to the at least one sprinkler, and preferably the water released is returned to the break tank means so that no water is wasted. The means for releasing water may comprise a valve which may be electrically controlled and remotely operable, e.g. by a suitable control circuit responsive to a signal sent by way of a signal transmission means, e.g. a telephone line. The response of the system to such release of water may be recorded and/or transmitted to another location from which operation of the system is monitored.

The invention will now be described by way of example with reference to the accompanying drawing, which is a diagram of the components and connections therebetween of a system according to the invention.

Referring to the drawing, a water main bringing water from a water supply authority is indicated at 50. A pipe 51 is branched off the main 50, and contains an isolation valve 1 followed by a non-return valve 2. The pipe extends into an enclosure or equipment cabinet or room indicated generally at 53 which contains the components described hereafter, although it will be appreciated that if desired certain components may be mounted at locations other than in the enclosure 53.

Within the enclosure, a pipe 54 connected to the pipe 52 has a monitored valve 3, a pressure sensitive device 4, a pressure gauge 5, and leads to a valve assembly for discharge of water into a break tank 8. The valve assembly for such discharge of water may comprise small and large float operated valves 6, 7. The tank 8 is further provided with water level detectors 9 and 9a which are arranged to provide an alarm signal in the event of low or high water level in the tank 8. The tank further has a drain valve 10. The tank may provide for storage of a volume of about 2m3 of water.

Three pipes 55, 56, 57 lead from the tank 8 to respective booster pumps 11, 12, 13 and thence by respective non-return valves 14, 15, 16, to a manifold 58. From manifold 58 a pipe 59 having a monitored isolating valve 18 and an automatic sprinkler alarm valve 19 extends to an outlet 61 which would be connected to suitable pipework leading to one or more sprinklers. Valve 19 also prevents reverse flow in the pipe 60. Between valve 19 and outlet 61, the pipe 60 has a pressure gauge 30, pressure sensitive electrical switch 20 to provide a "low pressure alarm" signal, pressure responsive switch 21, and pressure responsive switch 22 for recording system pressure.Pressure responsive switch 21 is a switch having a "dead band" between the pressures at which it switches "on" and "off'. There is further a flow rate measuring device 23 which may be a device as known by the name "Annubar" and a signal transmitter 24 associated with the flow rate measuring device 23. There is also a monitored drain valve 31. The maximum output of the three booster pumps 11, 12, 13 together is substantially not greater than the minimum sustainable flow rate of water available from the main 50 to replenish the tank 8. Such flow rate may be ascertained by enquiring of the water supply authority.

From manifold 58 there extends a further pipe 62 having a jockey pump 32 and non-return valve 33. This pipe 62 then rejoins the pipe 60 after the valve 19. A further connection to the manifold 58 is provided for fire brigade inlets 28, 29, by way of a monitored valve 27. The manifold 58 has a drain valve 17.

Between outlet 61 and the flow rate measuring device 23 a pipe 63 extends from the pipe 60 and has a motorised valve 25 and solenoid valve 26 connected in parallel with one another. From these valves, the pipe 63 leads to an outlet 64 to the storage tank 8. The pipe 63 may also have a branch 65 having a monitored valve 37, leading to waste.

Additionally shown in the drawing is, represented diagrammatically, a control panel 34. There is also an ambient temperature sensor 35 and an electrical heater 36 to warm the vicinity of the equipment above described to prevent freezing in cold weather. The control panel has associated with it suitable electrical and/or electronic circuits and devices for example including data processing means, to detect and control operation of the system components as described hereafter. Suitable indicating devices would be provided as required to indicate the status or condition of the components of the system, the pressures and/or flow rates existing at the different points of the system, and so on.

In use, provided none of the sprinklers connected to the outlet 61 is in operation and neither of the valves 25, 26 is open, jockey pump 32 operates in accordance with pressure responsive switch 21 to pressurise the pipe 60 leading to the outlet 61. A maximum water level within the storage tank 8 is established by float controlled valves 6, 7, and the system remains in equilibrium.

If one or more of the sprinklers connected to outlet 61 should be brought into operation, e.g. by the melting a fusible element in such sprinkler or sprinklers if a fire breaks out, the pressure at the outlet 61 will drop and this and the resulting flow of water to such sprinkler or sprinklers, initially provided by the jockey pump 32, will be detected by flow rate measurement device 23 and pressure switch 20. Firstly in response to such detection the effect is to bring the first pump 11 into operation, and if sufficient sprinklers are operating such that the pump 11 is not able to sustain the required flow rate and pressure at the outlet 61 the further pumps 12 and 13 are brought successively into operation.

As water is drawn from the tank 8 to be thus supplied to the sprinklers, the tank is replenished from the water main supply under the control of valves 6, 7.

At the same time as pump 11 first starts to operate, a fire alarm signal is caused to be generated, which may be arranged to operate an audible alarm and/or, preferably, cause a call-out signal to be transmitted to the fire brigade.

For testing the system, a signal, which may be sent from a remote location by telephone line or otherwise transmitted, is applied to the valve 25 or valve 26 to open it, which has the effect of simulating operation of one or more sprinklers connected to the outlet 61. Motorised valve 25 can provide a sufficient flow of water to simulate the operation of one or more sprinklers; while valve 26 can simulate operation of a large number of sprinklers, thus to test the full range of modes of operation of the system with the three pumps 11, 12, 13 successively brought into use. The water flowing through the valve 25 and/or valve 26 is returned to the storage tank 8 by way of outlet 64. The operation of the system as above described in response to opening of the valve 25 and/or valve 26 is checked.

The system may provide for the transmission to a remote location of the results of testing the system as above described, and/or recording of the testing results.

More particularly, the system may provide for the continuous monitoring of one or more of the following items: 1. The status of the mains electrical power supply to the system; 2. The state of the main isolating valve 3; 3. The settings of all pressure responsive switches in the system; 4. Whether the jockey pump 32 is running; 5. Whether each of the boost pumps 11 to 13 is running; 6. The level of water in the storage tank 8; 7. Mains water pressure; 8. The status of all electrically operable and/or monitored valves in the system; 9. The flow rate as measured by device 23.

Further additionally, there may be means for detecting and recording any entry into the enclosure 53 and/or control panel 34. The temperature sensor 35 and heater 36 may have their operation monitored, and an alarm signal may be provided if there is any danger of frost damage. There may be provided means for transmitting pre-recorded messages for communication to other locations and/or a public address system at the site of the sprinkler system installation.

Facilities may be provided for electrical connection to other equipment at the site of the installation or at other locations, e.g. to cause shut-down of fans, conveyors, and any other electrical equipment if there is a fire hazard condition existing.

There may be facilities for evacuating air from the system, if it is one where one or more pipes leading to sprinklers are not normally full of water.

In the event of a fire breaking out, the response of a system thereto is potentially useful information for the purpose of subsequent investigations.

Thus the system may also provide for monitoring and recording one or more of the following items: 1. The time of operation of the first sprinkler to operate; 2. Confirmation that the jockey pump 32 has been operating satisfactorily; 3. Confirmation that the low pressure switch 20 has operated satisfactorily; 4. Confirmation that the first and subsequent ones of the booster pumps 11 to 13 have been brought into operation, and the time thereof. This relates to the time that each sprinkler comes into operation, as the flow rate changes as further sprinklers operate; 5. The time a call-out signal was sent to the automatic 999 dialler or similar equipment; 6. The time a connection was made to the inlet 28 or 29; 7. The time any entry was made to the panel 34 for closing down the system.

All such information is additional to the regular testing carried out other than in response to the breaking out of a fire, which will confirm that the system was in satisfactory condition before the fire.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. A fire sprinkler system comprising: means for connection to a water main, for supply of water to the system; break tank means for receiving said water; at least one sprinkler; and pump means for supplying water from said break tank means to said at least one sprinkler; wherein said pump means is arranged to be operated so as to provide for supply of water to said at least one sprinkler at a flow rate substantially not greater than a predetermined flow rate.

2. A system according to Claim 1 wherein said predetermined flow rate is a value of a sustainable flow rate of water available from the water main.

3. A system according to Claim 1 or Claim 2 further comprising means for measuring the pressure and/or flow rate of water in a pipe leading to said at least one sprinkler, and means for controlling operation of the pump means in accordance with the flow rate and/or pressure thus measured.

4. A system according to any one of the preceding claims wherein the pump means includes a pump operable to pressurise water in said pipe leading to the at least one sprinkler when no sprinklers are in operation, whereby change of such pressure in the pipe provides an indication of the bringing into operation of a sprinkler or sprinklers.

5. A system according to any one of the preceding claims wherein the pump means includes a number of pumps of which one or more are arranged to be brought into operation according to the number of sprinklers operating.

6. A system according to any one of the preceding claims wherein the break tank means comprises a tank provided with a valve means operable in response to level of water in the tank, to control delivery of water from the water main to the tank.

7. A system according to Claim 6 wherein the valve means comprises a float controlled valve or valves.

8. A system according to Claim 6 or Claim 7 further comprising means whereby the possibility of flow back into the main, of water which has previously entered the tank, is eliminated.

9. A system according to any one of the preceding claims including means for providing an alarm signal in response to the operation of one or more sprinklers.

10. A system according to Claim 9 wherein said means for providing an alarm signal comprises means for detecting a drop in pressure at a point of the system leading to one or more sprinklers, and means for detecting flow of water leading to said one or more sprinklers.

11. A system according to any one of the preceding claims further comprising means for testing its satisfactory operation.

12. A system according to Claim 11 wherein said means for testing the satisfactory operation comprises means for simulating the operation of a sprinkler, and means for checking to ensure that operation of the pump means follows said simulated operation of a sprinkler.

13. A system according to Claim 12 wherein said means for simulating operation of a sprinkler comprises means for releasing water from a pipe leading to said at least one sprinkler.

14. A system according to Claim 13 wherein said released water is returned to the break tank means.

15. A system according to Claim 13 or Claim 14 wherein said means for releasing water comprises a valve which is electrically operable.

16. A system according to Claim 15 wherein said valve is operable in response to a signal sent from a remote location by way of a signal transmission means.

17. A system according to any one of Claims 13 to 16 comprising means for recording and/or transmitting to another location in response of the system to such release of water.

18. A method of operating a fire sprinkler system comprising means for connection to a water main for supply of water to the system, break tank means for receiving said water, at least one sprinkler and pump means for supplying water from said break tank means to said at least one sprinkler; said method comprising operating said pump means so as to supply water to said at least one sprinkler at a flow rate substantially not greater than a predetermined rate.

19. A method according to Claim 18 wherein said predetermined rate is a sustainable flow rate of water available from the main.

20. A method according to Claim 18 or Claim 19, comprising measuring and pressure and/or flow rate of water in a pipe leading to said at least one sprinkler, and means controlling operation of the pump means in accordance with the flow rate and/or pressure thus measured.

21. A method according to any one of Claims 18 to 20 comprising pressurising water in the pipe leading to said at least one sprinkler when no sprinklers are in operation, and using the change of such pressure in the pipe to provide an indication of the bringing into operation of a sprinkler or sprinklers.

22. A method according to any one of Claims 18 to 21 comprising providing an alarm signal in response to the operation of one or more sprinklers.

23. A method according to Claim 22 comprising detecting a drop in pressure at a part of the system leading to one or more sprinklers, and detecting a flow of water leading to said one or more sprinklers, to provide said alarm signal.

24. A fire sprinkler system substantially as hereinbefore described with reference to the accompanying drawings.

25. A method of operating a fire sprinkler system substantially as hereinbefore described.

26. Any novel feature or novel combination of features described herein and/or in the accompanying drawings.