FIRE SUPPRESSION SYSTEM

Abstract

There is provided a sprinkler device, comprising: a sprinkler bulb 100 comprising a sealed frangible housing 110, and a passive circuit device 120 within the housing 110, wherein the passive circuit device 120 comprises a wireless module 160; and a base station 200 configured to detect pressure changes inside the sprinkler bulb 110 via the wireless module 160. A method of testing integrity of a sprinkler bulb is also provided, comprising: monitoring a pressure change within the sprinkler bulb 100 via a wireless module 160 of a passive circuit device 120 inside a sealed frangible housing 110 of the sprinkler bulb 100; and determining that the sprinkler bulb is in working order if the pressure reaches a predetermined threshold; or determining that the sprinkler bulb is not in working order if the pressure does not reach the predetermined threshold.

Claims

1. A sprinkler device, comprising: a sprinkler bulb (100) comprising a sealed frangible housing (110), and a passive circuit device (120) within the housing (110), wherein the passive circuit device (120) comprises a wireless module (160); and a base station (200) configured to detect pressure changes inside the sprinkler bulb (110) via the wireless module (160).

2. A sprinkler device as claimed in claim 1, wherein the wireless module (160) comprises an inductor (170) and a capacitor (150) having a capacitance sensitive to pressure changes within the housing (110) of the sprinkler bulb (100), and wherein the base station (200) is configured to monitor changes in a resonant frequency of the wireless module (160) caused by changes in the capacitance of the capacitor (150) to thereby detect pressure changes inside the housing (110) of the sprinkler bulb (100).

3. A sprinkler device as claimed in claim 1, wherein the base station (200) is arranged to wirelessly provide power to the passive circuit device (120) via the wireless module (160).

4. A sprinkler device as claimed in claim 1, wherein the passive circuit device comprises a heating element (180) for heating fluid within the housing (110) of the sprinkler bulb (100).

5. A sprinkler device as claimed in claim 4, wherein the passive circuit device (120) is arranged so that the heating element (180) is activated only if a signal received by the wireless module (160) has an amplitude greater than a predetermined threshold.

6. A sprinkler device as claimed in claim 1, comprising a device controller (290) configured to test integrity of the sprinkler bulb (100).

7. A sprinkler device as claimed in claim 1, wherein the sprinkler bulb (100) has a diameter of less than 4 millimetres.

8. A fire suppression system comprising a plurality of sprinkler devices as claimed in claim 1, and a system controller configured to simultaneously test integrity of a plurality of the sprinkler bulbs (100) of the plurality of sprinkler devices.

9. A sprinkler bulb comprising a sealed frangible housing (110), and a passive circuit device (120) within the housing (110), wherein the passive circuit device (120) comprises a capacitor (150) and an inductor (170) arranged as a resonant circuit.

10. A method of testing integrity of a sprinkler bulb, comprising: monitoring a pressure change within the sprinkler bulb (100) via a wireless module (160) of a passive circuit device (120) inside a sealed frangible housing (110) of the sprinkler bulb (100); and determining that the sprinkler bulb is in working order if the pressure reaches a predetermined threshold; or determining that the sprinkler bulb is not in working order if the pressure does not reach the predetermined threshold.

11. A method as claimed in claim 10, wherein monitoring the pressure change within the sprinkler bulb (100) comprises monitoring a change in a resonant frequency of the wireless module (160) caused by a change in a capacitance of a capacitor (150) of the wireless module (160), and determining the pressure change based upon the change in the resonant frequency.

12. A method as claimed in claim 10, comprising wirelessly supplying power to the passive circuit device (120) sealed inside a housing (110) of the sprinkler bulb (100) using a base station (200).

13. A method as claimed in claim 10, comprising heating a fluid within the housing of the sprinkler bulb to increase pressure therein and thereby simulate a fire event.

14. A method as claimed in claim 10, comprising activating a heating element (180) of the passive circuit device (120) by sending a signal to the wireless module (160) having an amplitude greater than a predetermined threshold.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Certain embodiments of the invention are described below by way of example only and with reference to the figures in which:

[0039] FIG. 1 shows a sprinkler bulb comprising a housing and a passive circuit device inside the housing;

[0040] FIG. 2 shows a schematic diagram of communication between the passive circuit device of the sprinkler bulb of FIG. 1 and a base station;

[0041] FIG. 3 shows a perspective view of a capacitor for use as a pressure sensor in the passive circuit device of FIG. 2;

[0042] FIGS. 4A and 4B shows changes in resonant frequency of a wireless module of the passive circuit device as pressure inside the sprinkler bulb changes; and

[0043] FIG. 5 shows a schematic indicating characteristic pressure regions of the sprinkler bulb during heating.

DETAILED DESCRIPTION OF THE INVENTION

[0044] FIG. 1 shows a sprinkler bulb 100 comprising a sealed frangible housing 110 and a passive circuit device 120 disposed within the housing 110. The passive circuit device 120 is therefore sealed inside the housing 110. The housing 110 also contains a liquid 130 and a gas bubble 140.

[0045] In use, the bulb 100 is located in a sprinkler device (partially shown in FIG. 1), and is positioned to hold a seal, plug or the like in place to prevent fire suppression fluid from leaving the sprinkler device. The sprinkler device comprises a base station 200 (shown schematically in FIG. 2). The seal 210 of the sprinkler device is shown in FIG. 1. The sprinkler bulb 100 is arranged so that it prevents deployment of fire suppressant fluid unless it breaks. In the event of a fire near the sprinkler device, the liquid 130 in the housing 110 will be heated and therefore pressure within the housing 110 will increase. Once the liquid 130 reaches a predetermined temperature (e.g. indicative of being near a fire), the resulting pressure from the heated liquid 130 will break the frangible housing 110 and the seal 210 of the sprinkler device will no longer be held in place. Fire suppression fluid will then be discharged from the sprinkler device. The housing 110, liquid 130, and gas bubble 140 can be configured so that the housing 110 will break under predetermined conditions e.g. when the liquid 130 reaches a predetermined temperature, and hence when the housing 110 is exposed to a predetermined pressure thereby. The housing 110 may be formed of any suitable material, and may be formed of quartzoid.

[0046] If the housing 110 of the bulb 100 is damaged, for example by a crack, pressure increases in the liquid 130 inside the housing 110 may be able to normalise with ambient pressure outside the housing 110. For example, liquid 130 may leak out of the housing 110 and/or gas may leak into the housing 110. In that case, pressure within the housing 130 may not reach the level needed to cause the housing 110 to break, and therefore the sprinkler device may not be able to discharge fire suppressing fluid in the event of a fire. Thus, damage to or cracks in the housing 110 can jeopardize operational safety of the sprinkler device. Even micro-crackswhich may not be visible to an unaided human eyecan prevent proper functioning of the sprinkler blub 100.

[0047] Therefore, known methods of detecting cracks in sprinkler bulbs installed in sprinkler devices in the fieldwhich methods typically involve inspection of the bulbs by eyemay not be sufficient to ensure that a sprinkler device is in working order, and hence may not ensure operational safety of a fire suppression system. Further, such methods are time intensive. Methods which do not involve inspecting bulbs by eye are also known, but are unsuitable for use outside laboratory or factory conditions and with bulbs installed on site, and are typically unsuitable for testing bulbs en mass. Given that sprinkler devices are safety-critical, improvements in regard to testing are desirable.

[0048] To address the above matters, the sprinkler bulb 100 of FIG. 1 comprises a passive circuit device 120 sealed within the housing 110. The passive circuit device 120 comprises a wireless module 160 such as an LC circuit, comprising a capacitor 150 and an inductor 170. The sprinkler device also comprises a base station 200 arranged to wirelessly supply power to the passive circuit device 120 and monitor changes in a resonant frequency of the wireless module 160. The passive circuit device also comprises a heating element 180 and a pair of Zener diodes 190 arranged as a voltage dependent switch for controlling operation of the heating element 180.

[0049] The resonant frequency of the wireless module 160 is determined by properties of the inductor 170 and capacitor 150. The circuit device 120 therefore is responsive to signals over a certain bandwidth from the antenna 230 of the base station 200.

[0050] The passive circuit device 120 is disposed within the housing 110. It is necessary for proper operation of the sprinkler bulb 100 that the housing 110 is sealed to prevent any and all leaks (e.g. to prevent ingress of any fluid into the housing 110, and/or prevent egress of any fluid out of the housing 110) otherwise the housing 110 may not break in the event of an emergency, as described above. The passive circuit device 120 is therefore sealed within the housing 110 and cannot simply be provided with external connections e.g. for power and/or communication.

[0051] FIG. 2 shows a schematic of the base station 200 provided proximate the passive circuit device 120 to control, communicate with, and power the passive circuit device 120. The base station 200 comprises a resonance tracking unit 220 for detecting and tracking changes in a resonant frequency of the wireless module 160. It also comprises an antenna 230 for emitting to, and receiving signal from, the wireless module 160. A power supply 240 is provided to power to the base station 200, and also to power the passive circuit device 120 via interaction of the antenna 230 and wireless module 160. A communication and integration module 150 is provided to communicate with and integrate into a system architecture comprising e.g. a system controller and other sprinkler devices. A device controller 290 is provided to control operation of the base station 200 and passive circuit device 120. Communication between the base station 200 and the passive circuit device 120 is shown schematically by the lines of magnetic flux 260. The device controller 290 may control operation of the sprinkler device autonomously, or may control operation of the sprinkler device under the control of a remote system controller arranged to control e.g. a plurality of sprinkler devices and sprinkler bulbs.

[0052] Using the arrangement of FIG. 2, the housing 110 of the bulb 100 may be tested for cracks using the passive circuit device 120. The device controller 290 is configured to control operation of the passive circuit device 120 in order to carry out such a test. During a test, the device controller 290 instructs the antenna 230 to emit a signal which is received by the wireless module 160. The signal has an amplitude greater than a predetermined threshold and large enough to active the voltage switch provided by the two Zener diodes 190. The heating element 180 is therefore activated and the liquid 130 within the housing 110 is heated so that pressure inside the sprinkler bulb increases. The resulting pressure increase in the liquid 130 causes the capacitor 150 to deform and hence changes its capacitance.

[0053] FIG. 3 shows an example of a standard capacitor 300 for use as the capacitor 150 of the wireless module 160 of the passive circuit device 120. The capacitor 300 comprises a plurality of conductive sheets 310 (i.e. electrodes) separated by a predetermined distance 320 using a dielectric material 330. An active area 312 of the capacitor is defined by an overlap of the conductive sheets 310. If the capacitor 300 is subjected to a change in pressure (shown schematically by the arrow P) it will deform and the predetermined distance 320 between the conductive sheets 310 will change, thereby changing the capacitance of the capacitor 300. The greater the change in the predetermined distance 320, the greater the change in the capacitance.

[0054] The capacitance of a capacitor may be expressed as:

C=.Math.(n.Math.A)/d

[0055] where is the dielectric permittivity, n is the number of conductive sheets 310 of the capacitor, A is the active area of one of the sheets 310, and d is the predetermined distance 320 between the sheets 310.

[0056] From the above expression, it can be seen that as d decreases with increasing pressure, the capacitance of the capacitor 300 will increase (since the other factors do not change for a given capacitor 300). The distance d (i.e. the predetermined distance 320) as function of pressure p may be expressed as:

d(p)=d_0 (1p/E)

[0057] where E is Young's modulus of the capacitor in a direction normal to the active area, p is the hydrostatic pressure, and d0 is the original predetermined distance 320 between the conductive sheets 310 of the capacitor 300. Therefore, from the above expressions the pressure within the housing 110 of the sprinkler bulb is known as a function of capacitance capacitor 150.

[0058] The resonant frequency of the LC circuit 160 is a two-variable function of the inductance of the inductor 170 and of the capacitance of the capacitor 150. However, the inductance of the inductor 170 is substantially insensitive to changes in ambient pressure. As the pressure in the sprinkler bulb 100 increases and the capacitance of the capacitor 150 changes, the resonant frequency of the LC circuit 160 will change correspondingly. The greater the change in pressure, the greater the change in the capacitance and resulting change in the resonant frequency of the wireless module 160.

[0059] Therefore, by being arranged to monitor the resonant frequency of the wireless module 160, the base station 200 is thereby able to monitor the pressure of the liquid 130 within the housing 110. The base station 200 measures the resonant frequency using the resonance tracking unit 220 and the device controller 290 correlates the resonant frequency with a pressure inside the sprinkler bulb. The device controller 290 therefore determines pressure in the sprinkler bulb via the wireless module 160.

[0060] FIGS. 4A and 4B show examples of how the resonant frequency of the LC circuit changes with pressure. In FIG. 4A, the three curves show the frequency as a function of gain. Therein, the resonant frequency shifts from 263.49 kHz, through 257.13 kHz, to 251.58 kHz as pressure (and the capacitance of the capacitor) increases. FIG. 4B shows frequency against phase for the same situation, and the change in the resonant frequency is shown to be the same as for FIG. 4A.

[0061] The sprinkler device may therefore measure pressure and/or monitor pressure changes within the housing of the sprinkler bulb where the wireless module is located. The sprinkler device is then also able to test integrity of the sprinkler bulb using the heating element 180.

[0062] If during heating, pressure within the housing 110 reaches a predetermined level (e.g. a pressure nearly sufficient to break the housing 110) after the liquid 130 has been heated for a time, the device controller 290 may then determine that there is no pressure loss and therefore that there are no cracks in the housing 110. Thus, the bulb 100 may be determined to be in working order. Alternatively, if the pressure within the housing 110 does not reach the predetermined level after the liquid 130 has been heated for a time, the device controller 290 may determine that there is a pressure loss and hence a crack or the like in the housing. The blub 100 may then be determined not to be in working order.

[0063] FIG. 5 shows an example of various diagnostic ranges during a process for detecting a cracked sprinkler bulb. Different ranges, zones, and values may be used for different configurations of a particular sprinkler bulb. For example, the curves a and b of FIG. 5 are a function of the volume of liquid and gas in the housing 110, the type of liquid and gas, the type of material used for the frangible housing 110 etc.

[0064] FIG. 5 shows pressure changes in the housing 110 measured by device controller 290 during testing of the sprinkler bulb 100 and heating of the liquid 130. The horizontal axis indicates the time after the heating element 180 is activated, and the vertical axis indicates the pressure that is measured at a particular time. In a sprinkler bulb 100 that is in working order, the heating element 180 is expected to raise the temperature of the liquid 130, and hence increase the pressure in the housing 110, by a certain amount within a predetermined time period t1. The point t1 can therefore be used as a reference point to test the integrity of the bulb 100.

[0065] During testing, the pressure starts in an initial pressure zone 410, indicative of a pressure range at which the bulb 100 is ready for use e.g. prior to heating or a fire event. The pressure of the bulb 100 would be expected to be in this range if intact and when not heated. If the bulb 100 is in working order (i.e. not damaged) the pressure will increase approximately along curve a. That is, the pressure increases with increasing time (i.e. increasing temperature) while heated. Heating of the liquid 130 is stopped at time t1, and the pressure in the housing then falls again as the liquid 130 cools. The pressure therefore does not reach zone 440, wherein the housing 110 of the sprinkler bulb 100 is expected to break e.g. as would be the case in a fire event. However, curve a shows that the pressure does enter zone 430 in which the pressure of the liquid 130 increases with time and reaches a relatively high level. Zone 430 is therefore indicative of an intact bulb 100, and hence a bulb 100 which is in working order. The predetermined threshold for determining that the sprinkler bulb 100 is in working order, may be at a level in zone 430 e.g. near its upper range.

[0066] If the bulb 100 is not in working order (e.g. it is cracked) the pressure will increase approximately along curve b. On curve b, the pressure starts to increase with heating but soon plateaus. It is therefore evident that the pressure in the housing 110 will not reach zone 440, or even zone 430, and will not be sufficient to cause the housing 110 to shatter, despite the continued application of heat to the liquid 130 of the sprinkler bulb 100. Therefore, the sprinkler bulb 100 is not safe to use because it will be unlikely to break in the event of a fire.

[0067] The passive circuit device 120 is clearly a safety-critical component and should therefore be highly reliable. It is also preferable that the capacitor 150 be sensitive to pressure changes over a relatively wide pressure range e.g. from about 0 bar (i.e. 0 Pa) to about 25 bar (i.e. 2.5 MPa). Further, sprinkler devices are typically a conventional size, and sprinkler bulbs therefore have a conventional size which is relatively small, so the passive circuit device should be sufficiently small and correctly shaped to be housed within a conventional sprinkler bulb. Finally, sprinkler bulbs are single use items so the cost of the passive circuit device should not be prohibitive.

[0068] The sprinkler device described herein addresses the above requirements by use of the passive circuit device which does not require complicated electronics or expensive components. It therefore does not need a micro-processor, controller, memory or the like. It does not rely on RFID technology or the like and does not require digital communication. It may therefore be made simply and cheaply. It may also be reliable because of its simplicity. It may also be made small enough to fit within all conventional sprinkler bulbs because it requires so few components.

[0069] Thus, according to the disclosure herein, autonomous, reliable and remote testing of sprinkler bulbs 100 may be accomplished, and may be performed en mass. Bulbs 100 may be checked regularly by a central system and faulty bulbs 100 may be flagged for replacement. The disclosure herein provides a simple and reliable mechanism for measuring pressure within a sprinkler bulb by recognising that the resonant frequency of a wireless module in the bulb may change with pressure.