GB2184585A

GB2184585A - A fire and explosion detection and suppression system

Info

Publication number: GB2184585A
Application number: GB08531487A
Authority: GB
Inventors: Peter Edwin Moore; Brian David Powell
Original assignee: Graviner Ltd
Current assignee: Graviner Ltd
Priority date: 1985-12-20
Filing date: 1985-12-20
Publication date: 1987-06-24
Also published as: DE3640600A1; GB8531487D0; GB2184585B; US4718497A

Description

1 GB 2 184 585 A 1

SPECIFICATION

Fire and explosion detection and suppression The invention relates to f ire and explosion detection and suppression. More specifically, the invention relates to such systems employing sensors of electromagnetic radiation.

According to the invention, there is provided a fire and explosion detection and suppression system, comprising a plurality of radiation sensors each producing an electrical signal in responseto detection of at least a predetermined amount of a respective predetermined type of electromagnetic radiation, alarm means having a normal mode of operation and a modified mode of operation and connected to receivethe said electrical signals, the alarm means being operative in the said normal modeto produce an first alarm signal only in responseto the receipt of said electrical si gnaisfrom a predetermined number of thesensors including at leastonesensor responsiveto a firstsaid predetermined type of radiation and being operative inthe said modified modeto produce a second alarm signal in responsetothe receiptof one ormoresaid electrical signaisfrom a different predetermined numberof sensors and notincluding the said sensor responsive to the said first predeterminecitypeof radiation, and switching means operativeto switch the alarm meansfromthe normalto the modified mode in response to discharge into the vicinity of the said sensor responsive to the said first predetermined type of radiation of a f luid agentwhich attenuates radiation of the said first predetermined type.

According tothe invention,there is also provided a fire and explosion detection and suppression system, comprising,for each of a plurality of physical zones, a respective plurality of radiation sensors each producing a respective electrical signal in responseto detection of at least a predetermined amount of radiation of respectivetype, suppression meansfor each zone and normally operative only in responseto the simultaneous production by at leasttwo sensors in thatzone of their said electrical signals wherebyto discharge a suppressant agent intothatzonefor extinguishing fires orsuppressing explosions therein, the suppressant agent having the characteristic that it 105 attenuates radiation of the typeto which one of the said two sensors in each zone responds but does not significantly attenuate radiation of the type to which the other of the said two sensors responds, and modifying means operative in response to such discharge to temporarily modifythe suppression means of an adjacent said zone whereby to render it capable of operating in response to the production of its said electrical signal by onlythe said other of the said two sensors in that adjacentzone.

According to the invention, there is further provided a fire detection and suppression system for detecting and suppressing fires or explosions within an area divided into at leasttwo adjacent zones, comprising, for each said tone: a plurality of ultra-violet radiation responsive sensors each producing a first electrical signal in response to receipt of at least a predeter- mined amount of ultra-violet radiation, a plurality of infra-red radiation-responsive sensors each producing a second electrical signal in response to at least a predetermined amount of infra-red radiation, processing means connected to receive said first and second electrical signals and switchable between a normal mode in which it produces an alarm output onlywhen it simultaneously receives a predetermined plurality of said electrical signals which includes atleast one said firstelectrical signal and a modified mode in which it produces an alarm output in response to receipt of a different plurality of said electrical signals which does not include any said first electrical signals, suppressant discharge means responsiveto each said alarmsignal to cause discharge of an ultra-violet attenuating fire orexplosion suppressant into the said zone, and switching means responsiveto production of thesaid alarm signal when the processing means of thatzone is in the normal mode to temporarily switch the processing means of theotherzone intothe modified mode.

According to the invention,there isyetfurther provided a method of zone by zone protection against fires or explosions of a predetermined area, comprising the steps of detecting, within each of two adjacent zones, forthe simultaneous presence of at least predetermined respective amounts of two predetermined and differenttypes of electromagnetic radiation, responding thereto by releasing a predetermined fire or explosion suppressant into the zone in respect of which such detection takes place, the said suppressant being of a type which attenuates radiation of one said type, and for a predermined time thereafter detecting, in the adjacent said zone, forthe presence of the said respective amount of radiation of the other said type and releasing the said suppressant into that adjacentzone in response to such detection.

Fire and explosion detection and suppression systems and methods according to the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawingsinwhich:

Figure 1 is a diagrammatic view of an area to be protected by the system, showing sensors of the system installed; Figure 2 is a block circuit diagram of the system; Figure 3 is a view corresponding to Fig. 1 but showing a modified form of the system; and Figure 4 is a block circuit diagram of the modified system.

As shown in Figure 1, an area 5 is to be protected from fires or explosions. The area 5 may, for example, The drawing(s) originally filed was (were) informal and the print here reproduced is taken from a later filed formal copy. The claims were filed later than the filing date within the period prescribed by Rule 25(1) of the Patents Rules 1982. This print reflects (an) amendment(s) to the request for grant effected pursuant to Rule 35 of the Patents Rules 1982.

2 bean enclosed building. As shown in Figure 1, the area is divided into two zones, Zone A and Zone B. Two electromagnetic radiation sensors, 10A and 12A, are suitably mounted within Zone A so as to be able to monitor substantially the whole of the Zone and detect radiation arising in it. Two similar sensors, 10B and 12B are correspondingly mounted within Zone B. The sensors 1 OA, 1 OB, 12A, 12B are of a type which produces an electrical signal related to the electro- magnetic radiation received.

The sensors 1 OA and 1 OB a re sensors of u ltra-violet radiation. They may be of any suitable type but are preferably of the gas discharge or solid state avalanche detector type, such as cold cathode gas discharge tu be. They are arranged to be responsiveto ultraviolet radiation of the wavelength or wavelengths likely to be emitted by fires or explosions of the type to be detected and suppressed.

The sensors 12A and 12B are arranged to be sensitive to infra-red radiation within a wavelength range likelyto be emitted by fires or explosions to be detected and suppressed. The sensors 12B can be of any suitable type. They may, for example, be of the photo- diode type orthey may be thermopiles.

In each case, the sensors may be arranged to view the respective zones through radiation filters having appropriate wavelength bands.

Within each zone are mou nted one or more su ppression u nits 14A and 1413. Fou r such units a re shown in each zone, butthere may of course be more or less than this. They are positioned so as to be able to discharge suppressant over substantially the whole of the corresponding zone, the suppressant being of a suitable type to extinguish the fires and explosions detected " In a manner to be explained, the su ppression u nits are activated, to discharge their suppressant, in response to operation of the sensors, that is, in response to the sensors receiving radiation indicating the presence of a fire or explosion to be suppressed.

Figure 2 shows a block diag ra m of the system. As shown, it corn prises two sections, a section 20A corresponding to Zone A and a section 20B corresponding to Zone B. As shown, in Section 20A, the electrical output of sensor 1 OA isfed to an amplifying and processing unit 22A. This basically amplifies the signal from sensor 1 OA but may also process it in a suitable way. If the sensor 1 OA is of the cold cathode gas discharge tube type, its operation will involve it "avalanching" in responseto incidence of ultra-violet radiation above a certain level, resulting in the emission of an electrical pulse. In such a case, the circuit unit 22A can be arranged to produce an output signal in response to occurrence of a certain number of such pulses within a certain time interval, so as to reduce false warnings such as may be caused by ultra-violet radiation from othersources (e.g. solar radiation). The electrical signal from the circuit unit 22A, which will be dependent on the level of radiation received bythe sensor, isfed to a threshold unit 23A which produces an output (of fixed level) only if the incoming signal has such magnitude as indicates thatthe received radiation is above a predetermined level. The output of the unit 23A is fed to one input of an OR gate 24A whose outputfeeds one input of an AND gate 26A.

GB 2 184 585 A 2 The electrical output of the infra-red sensor 12A is fed to a suitable amplifying and processing circuit unit 28A. The output, which will be dependent on the level of radiation received by the sensor andlor its time dependent variation, is fed to a threshold unit 29A which produces an output (of fixed level) only if the incoming signal has such magnitude as indicates that the received radiation is above a predetermined level. The outputof unit29A isfed to the second inputof the AND gate 26A.

The output of the AND gate 26A isfedto a suppressor actuating unit30A. When operated by a signalfrom the output of theAND gate,the unit30A producesfour outputsignals on output lines 32A which are respectivelyfed to thefour suppressor units 14A (Figure 1) and causethem to dischargetheir suppressant into Zone A.

Itwill therefore be a ppa rent that simultaneous occurrence of ultraviolet and infra-red radiation ata level above respective thresholds set bythethreshold units 23A and 29Awill causeAND gate 26Ato produce an outputsignal which will result in the suppressor units 14A discharging suppressant into Zone A. Such receiptof radiation is assumed to indicate presence of a fire orexplosion to be suppressed.

Section 20B is similar in construction and operation, and will not be separately described; parts in Section 20B corresponding tothose in Section 20A are similarly referenced exceptforthe use of the suffix "B" instead of "A". Therefore, detection by sensors 1 OB and 12B of ultraviolet and infra-red radiation above thresholds respectively set bythe threshold units 23B and 29B will result in AND gate 26B causing the suppressor units 14B to discharge suppressant into Zone B. The radiation wavelengths to which the sensors are responsive are selected so as to minimise false alarms due to extraneous sources of radiation: e.g. solar radiation, lighting within the building, hot surfaces, and the like. Thus, such extraneous sources of radiation are unlikelyto actuate both of each pair of detectors simultaneously.

Varioustypes of suppressant may be used. One suitableform of suppressant is Halon, However, one of the characteristics of Halon isthat it considerably attenuates ultra- violet radiation. Therefore, in the system as so far described, there is a riskthat operation of the suppressor units in one zone, Zone A, say, as a result of simultaneous detection of the appropriate levels of ultra-violet and infra-red radiation bythe sensors 1 OA and 12A in the manner described, will impair, at least temporarily, the readiness of the ultra-violet sensor in the other zone. Thus, discharge of Halon into Zone A may result in some of the Halon entering Zone B and obscuring the area of view of the ultra- violet radiation sensor 1013. Therefore, if a fire orexplosion should occurwithin Zone B, sensor 10B may not detectthe resultant ultra-violet radiation because of the attenuating effectof this drifting Halon. Even though the infra-red radiation sensor 12B may detect infra-red radiation above the required threshold, this will not of course be sufficient to enable the AND gate 2613to operatethe suppressors units. The same problem could obviously arise inthe event of discharge of suppressant bythe suppressor 3 GB 2 184 585 A 3 units 14B (in response to operation of the detectors 10B and 1213); that is, Halon drifting into Zone A could impair its subsequent operation by attenuating ultra violet radiation reaching detector 10A.

In order to deal with this problem, the two Sections 70 20A and 20B of the circuit diagram (Figure 2) are inter] inked. Thus, the output of the AND gate 26A is fed to a latching circuit 34A, such as a monostable multi-vibrator. The output of the latching circuit 34A is fed on aline 36A to the second input of the OR gate 24B 75 in the Section 20B. Correspondingly, the output of the AND gate 26B is fed to a similar latching circuit3413 whose output on line 36B feeds the second input of the OR gate 24A in Section 20A.

Therefore, in the event of sensors 1 OA and 12A 80 detecting sufficient levels of radiation, so as to cause AND gate 26Ato actuate the suppressors 14A (Fig 1) via the suppressor actuator 30A, the latch 34A will also be set and will produce an output signal on its line 36A for a predetermined length of time. This output signal will thus enable the AND gate 26B th rough the OR gate 24B. Therefore, forthe length of the predetermined latching time of the latch 34A, the circuit arrangement of Section 20B only requires detection of sufficient infra-red radiation by sensor 12B in orderto actuate the suppressor units 1413. In otherwords, AND gate 26B will produce an output merely in response to detection of a sufficient level of infra-red radiation by thesensorl2B.

The predetermined length of time of latch 34A is arranged to be at least sufficientto enable the ultra-violet radiation-attenuating effect of any Haion drifting into Zone B from Zone Ato have dissipated.

ItwiiI be apparent that latch 34B has a correspond- ing effect on the circuit section 20A in the event of the sensors 1 OA and 12B simultaneously detecting sufficient respective levels of uitra- violet and infra-red radiation. Thus, this will cause actuation of the suppressor units 14B and atthe sametime switch the Section 20A so that, forthe duration of the predeter- mined latching time of latch 3413, Section 20a only requires detection of sufficient infra-red radiation by sensor 12B to cause suppressor units 14Ato be operated.

Effectively, therefore,the latch 34A or3413 of one 110 zone respectively operates to renderthe operation of the circuitry in the other zone temporarily indepen dent of ultra-violet radiation.

Although the problem discussed above has been discussed in relation to the attenuating effect of Halon, 115 other suppressants may have a correspondingly attenuating effect on ultra- violet radiation and the circuitry described can similarly be used to overcome this.

Itwill also be appreciated thatthe circuitry may easily be modified to take account of suppressant agentswhich might have an attenuating effect on infra-red radiation.

Modified forms of the system described may involvethe use of two sensors in each zone but both of 125 which are responsive to the same basictype of radiation: for example, both sensors in each zone could be responsive to infra-red radiation but in respectively different infra-red radiation bandwidths.

If the suppressant agent used were such that it 130 significantly attenuated infra-red radiation in one bandwidth, but not in the other,then itwill be appreciated thata circuit of the general form shown in Figure 2 could likewise be used.

in the system described, it has been assumed that there are merelytwo zones. However, there could of course be morethan two zones. In such a case, simultaneous detection of suitable levels of appropriate radiation bythe two sensors in one zonewould be arranged (besides operating the suppressor units of thatzone) to modifythe operation of the circuit in not merely one adjacentzone but in two (or more) adjacentzones into both or all of which the suppressant might drift. Thus, in both or all of such adjacent zones, itwould renderthe circuitry operative to set off the suppressor units in thatzone merely in responseto detection of an appropriate level of radiation by only one of the sensors (the one not adversely affected by the drifting suppressant).

Figs. 3 and 4 illustrate a modified form of the system and items in these Figures corresponding to items in Figures 1 and 2 havethe same references.

As shown in Figure 3, each zone has four pairs of sensors 10A, 12A (or 1 OB, 12B in the case of Zone B), each pairof sensors forming a single detector. Such an arrangement provides bettertotal coverage of the area being protected.

As shown in Figure 4, within each circuitsection (Section 20A or20B) each sensor is connected via a processing unit22A and a threshold unit23A (for Section 20X orvia a processing unit 22B and a threshold unit 23B (for Section 2013) to a respective voting unit 50A or 5013. Each voting unit produces a respective output onlywhen it receives a predeter- mined pattern of inputs (that is, a predetermined number of inputs from LIV sensors and a predetermined number of inputs from IR sensors). The output of each voting unit is fed to the respective suppressor actuator unit30A, 30B. It is thus not necessaryfor ail the sensors within a zone to have detected the necessary amount of the appropriate radiation in orderto set off the suppressor units. As long as at least a predetemined number of UV sensors and at least a predetermined number of]R sensors have detected the necessary amount of radiation, the voting unit will fire the suppressor units.

When the voting unit 50A produces its output, to the suppressor actuator 30A, this is also fed via latch 34A and line 36Ato the voting unit 50B. There it reconfigures the voting regime of the unitso thatforthe duration of the latch outputthe voting unit 50B can produce its output (to fire the suppressor units 1413) in response to a different pattern of input signals and one which does not require inputsfrom any LIV sensor 1 OB

Claims

in Zone B. Thus the attenuating effect on the operation of the sensors 1 OB caused by any Haion which may have drifted into Zone B from the suppressors 14A is overcome. Similarly, of course, production of an outputfrom voting unit 5013, in responseto receipt of its normal pattern of votes, reconfigures thevoting regime of the voting unit 50A (via latch 34B and line 3613). CLAIMS

1. Afire and explosion detection and suppression system, comprising a plurality of radiation sensors 4 each producing an electrical signal in responseto detection of at least a predetermined amountof a respective predetermined type of electromagnetic radiation, alarm means having a normal mode of operation and a modified mode of operation and connected to receive the said electrical signais,the alarm means being operative in the said normal mode to produce a first alarm signal only in responseto the receipt of said electrical signals from a predetermined number of the sensors including at least one sensor responsive to a firstsaid predetermined type of radiation and being operative in the said modified mode to produce a second alarm signal in response to the receipt of one or more said electrical signals f rom a different predetermined number of sensors and not including the said sensor responsiveto the said first predetermined type of radiation, and switching means operativeto switch the alarm means from the normal to the modified mode in response to discharge into the vicinity of the said sensor responsive to the said first predetermined type of radiation of a fluid agent which attenuates radiation of the said first predeter minecitype.

2. A system according to claim 1, in which the said fluid agent is afire or explosion suppressant agent. 90

3. A system according to claim 1, in which the said plurality of sensors are for positioning in a first physical zone and including first suppressant dis charge means responsive to the said alarm signal produced bythe said alarm means for discharging a su ppressant agent into that zone, and including a second similar plurality of said sensors for positioning in an adjacent physical zone, similar said alarm means connected to receive the electrical signa Is from the sensors of the adjacent zone, and similarsaid switching means for the alarm means of the adjacent zone, and second suppressant discharge means for discharging a suppressant agent into the adjacent zone in response to a said alarm signal from the alarm means of that zone, each said switching means being operative in response to production of a said first alarm signal by the alarm means of the otherzone, the said fluid agent being the suppressant agent.

4. Asystem according to anyone of claims 1 to 3, in which the said first predetermined type of radiation is ultra-violet radiation.

5. A system according to claim 4, in which an orthe other said predetermine type of radiation is inf ra-red radiation.

6. Afire and explosion detection and suppression system, comprising, for each of a plurality of physical zones, a respective plurality of radiation sensors each producing a respective electrical signal in response to detection of at least a predetermined amount of radiation of respective type, suppression means for each zone and normally operative only in responseto the simultaneous production by at leasttwo sensors in thatzone of their said electrical signals whereby to discharge a suppressant agent into thatzonefor extinguishing fires orsuppressing explosions therein, the suppressant agent having the characteristic that it attenuates radiation of thetypeto which one of the said two sensors in each zone responds butdoes not significantly attenuate radiation of thetypeto which the other of the saidtwo sensors responds, and GB 2 184 585 A 4 modifying meansoperative in responseto such dischargeto temporarily modifythe suppression meansof an adjacent said zone whereby to renderit capable of operating in responsetothe production of itssaid electrical signal byonlythesaid otherof the saidtwo sensors in that adjacent zone.

7. Afire detection and suppression system for detecting and suppressing fires or explosions within an area divided into at least two adjacent zones, comprising, for each said zone: a plurality of ultraviolet radiation-responsive sensors each producing a first electrical signal in response to receipt of at least a predetermined amount of ultra-violet radiation, a plurality of inf ra-red radiation-responsive sensors each producing a second electrical signal in response to at least a predetermined amount of infra-red radiation, processing means connected to receive said first and second electrical signals and switchable between a normal mode in which it produces an alarm output only when it simultaneously receives a predetermined plurality of said electrical signals which includes at least one said first electrical signal and a modified mode in which it produces an alarm output in response to receipt of a different plurality of said electrical signals which does not include any said first electrical signals, suppressant discharge means responsive to each said alarm signal to cause discharge of an ultra-violet attenuating fire or explosion suppressant into the said zone, and switching means responsive to production of the said alarm signal when the processing means of thatzone is in the normal mode to temporarily switch the processing means of the other zone into the modified mode.

8. A method of zone by zone protection against fires or explosions of a predetermined area, comprising the steps of detecting, within each of two adjacent zones, forthe simultaneous presence of at least predetermined respective amounts of two predetermined and differenttypes of electromagnetic radia- tion, responding thereto by releasing a predetermined fire or explosion suppressant into the zone in respect of which such detection takes place, the said suppressant being of a type which attenuates radiation of one said type, and for a predetermined time thereafter detecting, inthe adjacent said zone, forthe presence of the said respective amount of radiation of the other said type and releasing the said suppressant into that adjacent zone in response to such detection.

9. A method according to claim 8, in which the said one type of radiation is ultra-violet radiation.

10. A method according to claim 9, in which the said othertype of radiation is infra-red radiation.

11. A system or method according to any preceding claim. in which the said agent is Halon.

12. Afire or explosion detection and suppression system, substantially as described with reference to Figures 1 and 2 of the accompanying drawings.

13. Afire or explosion detection and suppression method, substantially as described with reference to Figures land 2 of the accompanying drawings.

14. Afire or explosion detection and suppression system, substantially as described with referenceto Figures 3 and 4 of the accompanying drawings.

15. Afire or explosion detection and suppression method, substantially as described with reference to Figures 3 and 4 of the accompanying drawings.

Printed in the United Kingdom for Her Majesty's Stationery Office by the Tweeddale Press Group, 8991685, 6187 18996. Published at the Patent Office, 25 Southampton Buildings, London WC2A lAY, from which copies may be obtained.

J 1 GB 2 184 585 A 5