section a - product application
Contents
1. The graph in Fig 6 shows the detection range as a function of pan area for petrol fires It will be seen that this curve is approximately a square law that is to say that to obtain de tection at twice the distance the pan area must be multiplied by four 5 2 2 OTHER LIQUID HYDROCARBONS Ranges achieved with other fuels burning on 0 1m pans are as follows n heptane 18m Kerosene 18m Alcohol I M S 15m Diesel oil 15m Ethylene glycol 18m The detection range for other pan areas may be calculated using the square law relationship given in para 5 2 1 5 2 3 GAS FLAMES Most flammable gases contain carbon and the radiation pro duced when such gases burn is easily detected by the S161 Additionally tests have shown that accidental fires involving gases will produce sufficient flicker to give rapid alarm response from the detectors This is equally true for fires resulting from low pressure less than 0 5 lb in 0 035 kg cm2 leaks Typical results obtained by burning natural gas methane from a 1 inch 25 4mm diameter pipe are given below GAS PRESSURE DETECTION RANGE lb in2 kg cm2 metres 0 5 0 035 30 1 0 0 070 30 5 0 0 351 50 25 0 1 758 60 5 3 VOLTAGE DEPENDENCE The sensitivity of the detector is constant over the volt age range 18 0V to 24 0V d c The performance out side this range is not guaranteed 5 4 TEMPERATURE DEPENDENCE The range of the detector will vary by less than 10 over the2. 10 FIRST DETECTOR IN ZONE CONTROL EQUI PMENT LAST DETECTOR IN ZONE INTERFACE PZ DETECTOR Fig 3 Detector Wiring 3 DETECTOR WIRING Detectors will normally be connected in zones which may contain up to ten detectors All detectors on a zone are connected in parallel and some form of end of line device should be used to monitor line continuity The wiring between the detectors and control equipment must provide the required degree of mechanical protection but allow the detector alignment to be adjusted to suit the area to be protected The detector is fitted with two 4 way terminal blocks giv ing separate terminal blocks for incoming and outgoing lines The two 20mm cable entries provided permit con venient connection of the incoming and outgoing lines us ing metal flameproof cable glands with continuity of cable screens provided by the cable gland plate To ensure no moisture ingress to the detector during the time between Installation and Commissioning tighten the four hexagonal socket cover retaining screws to torque of 3 5 4 5N m 2 6 3 31bf ft The End of Line Resistor 0 6 Watt minimum 2k4 mini mum metal film 5 not smaller than 2 5mm diameter and 10mm long actual resistor value dependent on controller should be fitted at the EOL Terminal Block of the last de tector situated in the right hand side of the cover as shown in Fig 3 3 1 RECOMMENDED CABLE TYPES The cable selected for interconnection
3. a suitable surface The front section of the enclosure contains the encapsu lated electro optical assembly and the interface unit which is connected to the terminal blocks by a small ca bleform Two sapphire windows are fitted in the front of the housing The upper window allows infra red radia tion to fall on the sensor and the LED alarm indicator is visible through the lower window The front section of the enclosure is attached to the rear section by four captive screws A seal provided between the front and rear sections ensures protection to IP67 3 2 TECHNICAL DATA Dimensions 160mm x 160mm x 90mm without bracket see Figs 4 and 5 Weight 2 0kg with optional bracket Enclosure Glass reinforced polyester with an anti static graphite content interior amp exterior metal fittings of stainless steel Bright Stainless steel to BS 1449 Pt 2 316S16 Mounting Bracket Screws etc exposed to the elements Bright Stainless Steel to BS970 Pt1 316L 4 ENVIRONMENTAL 4 1 GENERAL The design and construction of the S161 is such that it may safely be used over a wide range of environmental conditions Relevant limits are given in para 4 2 4 2 TECHNICAL DATA 4 2 1 TEMPERATURE AND HUMIDITY Operating temperature range 20 C to 80 C 40 C with reduced range Storage temperature range 40 C to 80 C Relative humidity 95 100 intermit tent Enclosure Protection IP67 IEC529 BS5490 4 2 2 VI
4. be continually subjected to water drenching d in outdoor installations in areas of high so lar radiation some form of sunshade is recommended to prevent excess heating of the detector e wm the detector should not be sited in a posi tion in which it will be subject to severe ic ing f the detector must be mounted on a stable structure which is readily and safely ac cessible for maintenance staff The detector may be secured directly to the fixing surface with two or more M6 bolts studs or screws at the fixing centres shown in Fig 1 110 DETECTOR FIXING DIMENSIONS Fig 1 Detector Fixing Dimensions 2 2 MOUNTING BRACKET The detector mounting bracket is to be secured with two M8 bolts studs or screws at the fixing centres shown in Fig 1 A drilling template is provided to allow the opti mum selection of the fixing centres and the 2 5mm diam eter 3mm deep pivot hole The surface chosen for the mounting should be flat over the area of the bracket or detector to ensure a stable fixing The S161 may be operated in any position but the actual mounting point must obviously be chosen to allow suffi cient clearance for adjustment of the angle and must also allow space for the cable assembly A clearance of 200mm in all directions from the fixing point will nor mally be sufficient to allow the full range of adjustment Fig 2 refers TYPE A BRACKET Fig 2 Clearance Required for Full Adjustment
5. of the com bustion process gives rise to a very high level of infra red radiation in the wavelength region between 4 2um and 4 7m The unique patented filtering system of the 161 Detector restricts the radiation reaching the sens ing cell to a narrow band of infra red radiation in the re gion of 4 4um The radiation from a fire flickers in a characteristic way and the detector uses this flicker signal to give extra dis crimination against interfering infra red sources The detector circuit analyses the signal within the flicker frequency region and if the amplitude of the signal is above a preset threshold level for three seconds then an alarm is signalled If the signal is below this threshold level then the detector will not alarm even after a long period of time The level of the signal depends upon the size of the flame and its distance from the detector For liquid fuels the level is roughly proportional to the surface area of the burning liquid For any type of fire the signal level var ies inversely with the square of the distance 3 TB2 TO NEXT SPARE 1 I UE VE DETECTOR I Fig 3 S161 Housing Showing Fixing Dimensions For convenience fire tests are normally carried out using liquid fuels burning in pans of known area in still air The sensitivity of a detector can then be conveniently ex pressed as the distance at which a particular fire size can be detected It is important
6. BRATION The S161 is designed to operate within specification and without false operation when subjected to vibration on any axis at the following levels 2 24Hz 1 27mm 24 55Hz 2 50g 55 100Hz 0 7g 4 2 3 RADIO FREQUENCY INTERFERENCE The detector is insensitive to radio frequency interference and will operate normally in field strengths of 10V m at fre quencies up to LOOOMHz It thus meets or exceeds the re quirements of BS6667 Part 3 1985 IEC 801 3 1984 severity level 3 severe electromagnetic environments 4 2 4 IONISING RADIATION The S161 like other infra red detectors is insensitive to X rays and gamma radiation as used in non destructive testing The detector will operate normally and will not false alarm when exposed to this type of radiation although long term exposure to high radiation levels will ultimately lead to permanent damage 5 PERFORMANCE CHARACTERISTICS 5 1 GENERAL A large number of fire tests have been carried out to deter mine the response limits of the S161 detector The results of these tests are summarised below In order to appreciate their significance an understanding of the mode of the oper ation of the detector is necessary and a brief explanation fol lows 160 140 VUE VE IN SPARE FROM ONTR 5 1 1 MODE OF OPERATION BEHAVIOUR IN FIRE TESTS Flaming fires involving carbonaceous materials produce large quantities of carbon dioxide This part
7. USER MANUAL Issue 2 IR S161 Date 01 94 SECTION A PRODUCT APPLICATION 1 INTRODUCTION The S161 is an infra red flame detector designed to provide early warning of flaming fires involving carbonaceous materials The detector makes use of state of the art infra red sensors and filters to provide major improvements in the rejection of deceptive phenomena while retaining the inher ent advantages of infra red detectors Special attention has been paid to the optimisation of the op tical bandwidth The detector uses optical filters which are made to THORN Security Limited s specification to restrict the response to a narrow bond in the region of 4 4mm The bandwidth chosen gives high sensitivity to hydrocarbon fires while minimising the response to other sources of in fra red radiation In particular the response to sunlight has been reduced to a level at which the detector can be consid ered completely solar blind The principles on which the detector is designed are pro tected by the following patterns US Patent No 4471221 Canadian Patent No 1191229 European Patent Application No 823107462 Japanese Patent Application No 62667 82 The detector is electrically compatible with most conven tional 2 wire fire detection systems The circuit techniques used together with the mechanical design allows the detec tor to be certified for use in hazardous atmospheres The hazardous area classification togethe
8. ange check the resistance between the circuit and earth if the reading obtained is greater than 1 meg ohm record the reading and proceed to c otherwise locate and rectify the earth fault remove the short circuit at the end furthest from the control equipment measure the resistance between the zone conductors if the reading obtained is greater than 1 meg ohm record the reading otherwise locate and rectify the insulation fault replace the cover 11 12 SECTION D COMMISSIONING USER MANUAL Issue 2 IR S161 Date 01 94 1 SYSTEM CHECKS Before connecting the zone wiring to the control equip ment or to the detectors a general inspection of the system should be carried out In particular the positions of the de tectors should be checked to ensure that the requirements given in the System Design and Installation sections are met 2 CONNECTING AND COMMISSIONING THE DETECTORS TESTS ON WIRING IN HAZARDOUS AREAS When carrying out tests on wiring in hazardous areas it is essential than an INTRINSICALLY SAFE INSULATION TESTER is used Further guidance on testing systems in hazardous areas can be found in BS5345 Part 1 2 1 2 2 COMMISSIONING PROCEDURE WARNING ENSURE THE SUPPLY TO THE DETECTOR IS ISOLATED BEFORE OPENING THE COVER Carry out the following procedure a Repeat the HV and LV insulation and con tinuity tests carried out by the installation engineer Record the results o
9. btained b connect the loop wiring at each detector terminal block c check the correct value EOL resistor is fit ted at the EOL terminal block in the last detector d fit the front cover assembly to the rear sec tion care should be taken to ensure that the internal wiring is not trapped between the terminal blocks and the front assembly It should be noted that a rubber seal is provided between the front and rear sections of the housing and this seal must be clean and dry before assembly It is also important to ensure that no moisture is trapped inside the housing Tighten the four hexagonal socket retaining screws to a torque of 3 5 4 5 N m 2 6 3 31bf ft e at this stage the angle of the detector should be adjusted to view the required area and the fixing nuts and bolts finally tightened The cable from the circuit to the detector should then be routed using cable ties or clips as necessary to minimise the risk of physical damage f commission the controller as necessary 2 3 DETECTOR TESTING HAZARDOUS AREAS The use of naked flames for detector testing in hazardous areas is obviously unacceptable The T110 Test Source has been designed specifically for the on site testing of the S100 Series on infra red flame detectors in hazardous are as When testing the S161 the correct adaptor plate must be fitted to the T110 Test Source S161 Adaptor Plate Stock Code No 592 001 005 Note The T110 has a charg
10. ds including petroleum products alcohol and glycol etc b flammable gases including methane c paper wood and packing materials d coal e plastics These substances ignite readily and burn rapidly pro ducing flame often accompanied by large volumes of dark smoke Note The detectors are not designed to respond to flames emanating from fuels which do not contain carbon e g hydrogen ammonia metals and should not be used for such risks without satisfactory fire testing The S161 by virtue of its construction and rejection of spurious radiation is suitable for use both indoors or out doors in a wide range of applications 3 2 USE IN HAZARDOUS ATMOSPHERES The detector design uses the techniques of intrinsic safe ty encapsulation and increased safety to achieve a clas sification of Ex e s ib IIC T5 This classification allows the detector to be used without a zener safety barrier as a direct replacement for detectors certified Ex d flame proof How ever the circuit wiring must comply with Ex d or Ex e requirements and the use of BASEEFA cer tified glands rated Ex e is mandatory 4 BENEFITS OF THE S161 5 ORDERING INFORMATION Infra red flame detectors offer certain benefits over detec The S161 is supplied without a fitted bracket as in some ap tors working in the visible or ultra violet regions of the plications detectors are bolted directly onto a bulkhead spectrum For example they are A separate s
11. e discharge circuit which take several seconds to recharge Consequently the T110 does not test the re sponse time of a detector but only tests for re sponse to a flame The T110 tests the S161 with a defined energy at a opened distance indicating reliably when the S161 is operating above 75 of its specified performance levels SECTION E MAINTENANCE USER MANUAL IR S161 Issue 2 Date 01 94 1 GENERAL The S161 detector contains encapsulated electronic assem blies There are no replaceable or adjustable components within the housing which should not be opened once in stalled and commissioned Routine maintenance is therefore limited to cleaning and testing the detectors 1 1 ROUTINE INSPECTION At regular intervals of not more than 3 months detectors should be visually inspected to confirm that no physical damage has occurred and that the alignment of the detectors has not been disturbed The detector windows should be checked to confirm that they are not blocked and that no physical obstructions have been placed between the detector and the protected area In addition at intervals of not more than 1 year each detec tor should be checked for correct operation Any excessive deposits of dirt oil etc should be removed from the detector housing as described in 1 2 Note The inspection frequency specified above should be considered as a minimum require ment to be applied in the average environment The in
12. factured by THORN Security Limited where the The reset facility is implemented as follows a For fast reset to operate it is necessary for the supply to be removed for a min imum of 0 5 seconds 2 2 TECHNICAL DATA 7 the supply must fall by greater than 5 Supply Voltage 18 0V to 24 0V d c polarity Volts conscious c the detector or Zone must have an Quiescent Current 100mA max at 20V d c end of line resistor with a resistance of less than 100k Alarm Output Mode 2 wire latching 720 ohm in OK series with typically 4V d the noise immunity on the line ripple switched across supply is less than 3 Volts peak TB1 SPARE SPARE I NTERFACE UE CONTROL UNIT UE IN E EOL O T6 UE TERMI NAL NEXT DETECTOR UE SPARE EOL 2k4 MINIMUM SPARE FITTED IN LAST DETECTOR ONLY Fig 1 S161 Connection and Internal Wiring Including EOL THORN Securjty Limited e ExesibIIC TS BABEEFA No Ex87Y3550 Umax 250U ISOLATE malta BEFORE OPENING THIS COVER ereciRperic HAZARD CLEAN ONLY WITH DAMP CLOTH FSTHORN 161 J UK PAT 1550334 US PAT 4471221 160 EOL TERMINAL BLOCK UIEW ON REAR OF FRONT COVER Fig 2 S161 Cover 3 MECHANICAL CHARACTERISTICS 3 1 GENERAL The detector comprises a two part moulded plastic enclo sure as shown in Figs 2 and 3 The rear section of the housing is attached to an optional adjustable mounting bracket or the detector may be fitted directly to
13. lage involved a less volatile material such as kerosene the spread of flame from the ig nition point would be much slower The detector would then respond in a time independent on the distance from the fire At 18 metres for example an alarm would be given when the fire had reached 0 1m and at 36 metres when the fire had grown to 0 4m 6 3 DETERMINING NUMBER OF DETECTORS It will be clear that the number of detectors required for a particular risk will depend on the area involved and the fire size at which detection is required Large areas or small fires require large numbers of detectors There are as yet no agreed rules for the application of flame detectors and the overall system sensitivity must therefore be agreed between the installer and the end user Once this agreement has been reached the system designer can determine the area covered by each detector using a scaled plot based on Fig 7 and the fire test data This plot is best drawn to the same scale as the site plan so that direct imposition can be used to determine de tector coverage In carrying out the design certain factors should be kept in mind a For area rather than spot protection the best coverage will normally be obtained mounting the detectors on the perimeter of the area and pointing into the area b as the S161 is a line of sight detector any object within the detector s field of view will cause a shadow in the protected area Even s
14. mall objects close to the de tector can cause large shadows c the S161 may be used to look vertically downwards on to a risk area since smoke blocking is minimal d the detectors are passive devices and will not react with one another They may therefore be positioned with their fields of view overlapping 7 APPROVALS AND COMPLIANCE WITH STANDARDS 7 1 SAFETY The S161 has been certified by BASEEFA for use in haz ardous atmospheres under certificate number Ex 87Y3550 Itis classified Ex e s ib IIC T5 indicating a pri mary means of protection of Ex e increased safety It is therefore suitable for use in zone 1 or zone 2 areas if in stalled to the requirements of BS5345 Parts 6 and 8 7 2 OTHER STANDARDS The S161 is a development from S111 offering a more ro bust housing The 111 has been submitted to independ ent tests which show that it meets all the requirements of the C E A Test Methods for Point Infra red Flame Detec tors up to its designed angle of vision of 90 7 3 OTHER APPROVALS The complete list of approvals for ALL equipment is given in THORN Publication O05A 01 G1 which is updated at regular intervals q DETECTOR 30 30 80 80 70 20 60 602 50 50 40 40 Fig 7 Relative Range vs Angle of Incidence SECTION C INSTALLATION IR 161 Date 01 94 USER MANUAL Issue 2 1 GENERAL The S161 detector is supplied with the option of an adjust able m
15. ounting brackets for fixing to a convenient rigid surface All electrical connections are made via the two 4 way terminal blocks and an end of line terminal block inside the detector housing Two 20mm cable entries are provided Guidance on mounting and wiring the detectors is given below A cable gland plate secured inside the housing by metal Ex d flameproof cable glands provides screen continuity 2 MOUNTING A DETECTOR The location of each detector should have been deter mined at the system design stage according to the princi ples detailed in Section B marked on the site plan The detector may be mounted on a horizontal or vertical surface The actual mounting position must however be decided during installation and in choosing the position the principles following together with the original system requirements should be followed 2 1 CHOICE OF MOUNTING POSITION The following points must be observed when choosing the mounting position a The detector must be positioned such that a Clear line of sight is provided to all parts of the risk area Roof trusses pipework supporting columns etc in front of the de tector can cause significant shadowing and should be avoided b ma if supervision of an area immediately be low the detector is required it is essential that the angle between the detector and the horizontal is not less than 40 c wm the detector should not be sited in a posi tion where it will
16. r with the mechan ical design allows the detector to be used as a replacement for flameproof detectors using existing Ex d wiring 2 GENERAL CONSTRUCTION The detector is of robust construction to allow its use in harsh environments The infra red sensor and other circuit components are mounted on a single printed circuit board within a stainless steel screening box The box is filled with epoxy resin to form a rugged opto electronic assembly The encapsulated assembly along with an encapsulated in terface unit is in turn contained within an impact resistant glass reinforced moulded plastic housing designed to give a level of ingress protection to IP67 The moulding mix con tains graphite to eliminate the possibility of generating a static charge during cleaning with a dry cloth Two 20mm cable entries are provided in one side of the housing and all electrical connections are made to two 4 way blocks and an end of line terminal block housing A ca ble gland plate secured inside the metal cable glands not provided enable screen continuity The complete detector may be mounted on an optional stainless bracket which allows a wide range of adjust ments in two axes 3 APPLICATION 3 1 GENERAL The detector is intended for the protection of high risk areas in which accidental fires are likely to result in flam ing combustion with the production of carbon dioxide Typical materials in this type of risk are a Flammable liqui
17. range of 20 C to 70 C 5 5 DIRECTIONAL SENSITIVITY The sensitivity of the S161 is at a maximum on the de tector axis The variation of range with angle of inci dence is shown in Fig 7 6 DESIGN OF SYSTEM 6 1 GENERAL Using the information given in paras 2 to 5 it is possible to design a flame detection system having a predictable performance Guidance on the application of the above data and on siting of detectors of given below 6 2 USE OF FIRE TEST DATA It has been explained in Para 5 that the sensitivity of the detector is most easily specified in terms of its response to well defined test fires Tests are conveniently carried out using a 0 1m pan Sensitivity to other pan areas is calculated from the square law relationship Accidental fires by their very nature rarely of a well de fined size It is still possible however to judge the re sponse to a p fire using the fire test data For a example A spillage fire involving a highly volatile liquid such as petrol will spread very quickly from the point of ignition to cover the complete surface of the pool Such a spillage would normally cover 2m or so Using the data for petrol fires and extrapolating to an area of 2m we would expect the S161 to respond within 10 seconds at a distance of about 80 metres At a distance of 20 metres the response time would only be a few sec onds less and in any event can never be less than 3 sec onds If on the other hand the spil
18. spection frequency should be increased for dirtier environments or those which present a higher risk of physical dam age 1 2 DETECTOR CLEANING The S161 Infra red detector is relatively tolerant of accu mulations of dirt on the sensor window However thick deposits of dirt and oil will cause a loss of sensitivity It is recommended that detectors be cleaned using water or a detergent solution A stiff bristle not wire brush may be sued to remove heavy deposits Note The act of cleaning or polishing the detector face and window may cause a detector to produce an alarm it is important therefore that before the window is cleaned the de tector should be isolated By isolating the relevant circuit at the control unit The cir cuit must be de isolated as soon as clean ing is complete 13
19. tainless steel 316 bracket is available for better a Highly sensitive to flame thus increasing applications probability of early detection of hydrocar Stock Code Number bon fires f S161 Detector 516 009 022 b not greatly affected by window contami nation by dirt and oil deposits thus de Stainless Steel Bracket 517 001 184 creasing maintenance frequency leading to operating cost reduction c able to see flames through smoke and able to see flames through high densities of sol vent vapours thus increasing the probabil ity of early detection of hydrocarbon fires over other ultra violet detectors in the same conditions The S161 has all the above benefits and additionally it is d completely solar blind in normal condi tions thus eliminating false alarms due to direct or indirect sunlight e insensitive to electric areas thus eliminat ing false alarms from welding operations f insensitive to artificial light sources g suitable for use in hazardous atmospheres as a direct replacement for detectors certi fied Ex d flameproof h sealed to IP67 when suitable cable glands are used ensuring long term reliability in harsh environments USER MANUAL Issue 2 SECTION B SYSTEM DESIGN INFORMATION IR S161 Date 01 94 1 INTRODUCTION In rush Current The design of a system incorporating S161 flame detectors must take account of the detector s electrical mechanical and environmental characteris
20. tics and its detection per formance This information is given below together with guidance on detector siting Alarm Indication Reset Time Reset Voltage 2 ELECTRICAL CHARACTERISTICS GENERAL The S161 is a two wire device which is designed to operate on any fire detection control equipment currently manufac tured by THORN Security Limited or similar fire detection controllers The quiescent current drain is very small and the alarm condition is latched in the detector and signalled by a large increase in current demand Resetting is achieved by removing the supply voltage for a period of at least five seconds An interface unit is located inside the front cover adjacent to the detector module Stabilisation Time End of Line Resistors 2 1 ne A NEATA ats reset is short The Interface Unit is advice which limits the power trans ferred to the detector module to a safe level The end to end resistance of the Interface Unit is nominally 373 ohms 800mA peak decreasing with a time constant of 250ms to the quiescent current red LED visible from front of detector Not greater than 1 second Supply must be reduced to less than 2V 20 seconds typical 0 6 Watt minimum 2k4 minimum metal film 5 not smaller than 2 5mm diameter and 10mm long actual resistor value dependent on controller Detectors from serial number 16000 onwards have been modified to facilitate their use with control panels not manu
21. to the control equipment should meet the requirements of BS5345 parts 1 amp 6 or relevant approval bodies Cables should not nor mally have a cross sectional area of less than 1mm for solid conductors or 0 5mm for stranded conductors The terminal block accepts cables up to 4mm2 cross sectional area 4 INITIAL WIRING CHECK After installing the wiring as detailed above and be fore connecting any detectors or end of line devices the following tests should be carried out 4 1 TESTS ON WIRING IN HAZARDOUS AREAS When carrying out tests on wiring in hazardous areas it is essential than an INTRINSICALLY SAFE INSU LATION TESTER is used Further guidance on test ing systems in hazardous areas can be found in BS5345 Part 1 4 2 CONTINUITY TESTS To check continuity proceed as follows a Nar Short together the bare tails of the to and to at each detector b ma short together the pair at the end fur thest from the control equipment c wm using an ohmmeter set to its lowest range check the loop resistance at the control equipment end d wm if the reading obtained is less than 50 ohms record the reading obtained and proceed to para 4 3 e wm if the reading obtained is greater than 50 ohms locate and rectify continuity faults by quartering the system 4 3 INSULATION TESTS To check the insulation proceed as follows a b c d Using an ohmmeter set to its highest r
22. to think in terms of distance rather than time because of the different burning characteristics of different fuels Fig 5 shows the response to two different fuels which ultimately produce the same signal level ASSEMBLY SHOWING DETECTOR VERTICAL ADJUSTMENT Fig 4 Mounting Bracket SIGNAL LEVEL 0 10 20 a PETROL FIRE 0 1m AT 18m RANGE b KEROSENE FIRE 0 1m AT 18m RANGE The signal level given by petrol quickly reaches its maxi mum and produces an alarm within about six seconds of ignition Kerosene on the other hand being less volatile takes about a minute to reach equilibrium and an alarm is given in about 55 seconds from ignition The time taken by the fire to reach equilibrium depends of course on the ini tial temperature of the fuel If the Kerosene were to be pre heated to a temperature above its flash point then its behav iour would be equivalent to that of petrol at 25 C The test data presented below refers to fires which have reached their equilibrium condition 2 te 50 ADJUSTMENT WALL MOUNTING BRACKET SHOWING HORIZONTAL ADJUSTMENT Stockcode 517 001 184 a 30 40 50 60 TIME SECONDS Fig 5 Response to Fires 40 30 RANGE METRES 20 10 PAN AREA m Fig 6 Detection Ranges vs Pan Area Petrol 5 2 FIRE TEST DATA 5 2 1 PETROL The most convenient fuel for fire tests is petrol gasoline since it is readily available and quickly reaches its equilibri um burning rate
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