A Fire Disaster Intelligence Alarm System Applicable To Underground Space

A Fire Disaster Intelligence Alarm System Applicable To UndergroundSpaceYan ZhangLS Cable & System China R&D CenterRm. 4808, New World international Trade Center,No.568, Jianshe Avenue, Wuhan, Hubei, 430015, P. R. Chinawhuzhy@Keyword: Underground space, Fire-fighting, Intelligence systemAbstract . Like the building on the ground, there are also many factors causing fire disaster in the underground building. There the disaster often happened, e. g in 1972 and l980 in Japan and in 1969 and1988 in China, the fire disaster took place in the underground spate which brought about a large amount of loss of property and casualties. The paper proposed a fire disaster intelligence alarm system. It is composed of a main computer system and several branch computer unit and it is useful for preventing fire in the underground building.IntroductionIt has a long history that the mankind use the underground space. Especially nowadays, the population explosion, Land expensive, traffic jam and environment worsening, that even more further promote development and complication of the underground space. Some countries have formulated relevant law and regulation for underground space development and application, even taken the underground space as “new territory”. ITA (International Tunneling Association) also proposed a policy manifesto about underground space. Thus it can be seen that the mankind pay attention to development and application of the underground space.Like the building on the ground, there are also many factors causing fire disaster in the underground building. There the disaster often happened, e. g in 1972 and l980 in Japan and in 1969 and1988 in China, the fire disaster took place in the underground spate which brought about a large amount of loss of property and casualties.The characteristics of the underground Space fire disaster are that there is a huge amount of smoke and it spreads quickly a1ong the tunnels, the smoke difficultly vents to air over ground, and that the fire-fighters close with the fire field is difficult, the person at the disaster field evacuate is not easy. Therefore, there should be more rigorous fire preventing condition and better fire alarming System for the underground building than for any daylight bui1ding.Many people studied the problems about the fire safety in underground building. For example, Qiao Jin Xiu, T. Tasukami, Raysterling and John Carmody et al studied the fire preventing measure respectively[1,2,3,4]. On the basis of the a standard of BOCA (Building officials and Code Administrators ) , Thomas J. Frost analysed the fire grade for the used various underground space and reposed fire safety code of underground space[5]. Fystein Meland et al studied the fire safety and escape strategies for a rock cavern stadium and considered public evacuating method. Some ones mentioned the fire auto-alarming device , but few of them involved its details[6].It is known that there is a process from fire starting to its Spreading. If at the starting one can protected and given out fire alarm, it is possible to take relevant fire-fighting measure or organize public evacuating, thus avoiding or lowering the property loss and population casua1ties. The paper, just considering that, introduced a fire intelligence alarming system applicable to underground space.According to the Omens that it can result smoke, temperature-raising or fire Light at the fire starting, the sensors will transmit signals to the center control system and send out fire alarm. If the system isjoined with other fire-fighting facility they can become a complete fire auto-alarming and fighting system. We will expound the relevant technology details, as following.The Outline of the SystemWith the deve1oment and utilization of the underground space, it is becoming a protuberant problem to heighten the level of precautions against fire in underground space. It has become urgent matter in fire protection of underground building that to use technique for effectively forecasting and auto-extinguishing fire. The system is a fire alarm network that is composed of some number of extension branch system and a main center controller.The branch system also can be divided into n groups and each group is composed of m units, see fig. l.Fig. 1 Network circuit frameThe network system has some primary characteristics as follows;(1) In the system, the smoke-sensing temperature-sensing and light-sensing sensors are disturbed Little by the nature environment.(2) In the system the alarm for abnormal Situation is sent out if one of the smoke, temperature and fire light at the monitoring seat is increased sudden1y. The branch units will also report the situation to the main control system so that the main controller can take relevant measure.(3) In the system if any two among the smoke, temperature and light at some monitoring point are increased sharply, the units wil1 send out fire alarm to the main controller and the controller will make further logical decision.(4) After sending out fire a1arm signal. If the branch system didn't obtain the instruction from the main it would self-start the automatic fire extinguisher to put out a fire.(5) In order to prevent fire spreading, the main controller will indicate all branch units of the group (or in the air) open the fire extinguisher if the number of the alarming units in the same group exceeds the limit value.(6) In order to prevent the branch units from hardware fau1t of the smoke, temperature and fire light-sensors the se1f-checking circuit is set up, which self -checking with the detecting signal from the CPU Of units.(7) The main system can monitor and display the working state of every units, and can alsogroup 0……telecontrol every of them (e. g put out a fire, switch off or reset etc. ).(8) Serial communication interface is used between all branch units and main system.(9) When the main controller does simultaneously other works or takes place trouble, the each branch unit still can work indcpendent1y. When any unit takes place trouble the others and main system will still work and be not influenced.The Construction And Work Principle of the Network SystemThe block diagram of fire disaster intelligence network circuit is shown in fig 1.The circuit principle of the branch unit and the main controller are shown in fig.2 and in fig.3 respectively.Fig. 2 The principle of the branch system hardwareFig. 3 The principle of the main system hardwareThe main system can be composed of severa1 branch systems which are joined to the main Control system with serial communication. Each unit can work under unified management of the main system and also can be operated independently at the most forward position of the fire field. The branch units can be divided into several groups (or in preventing zone). When fire happened, at some monitored site or zone the unit can alarm and start the fire-extinguishing device sensitively and rapidly.The work principle of the fire intelligence alarm branch unit. The fire intelligence alarming branch unit is composed of monolithic CPU, smoke-sensor, temperature-sensor, fire light-sensor, alarm circuit, control circuit of fire-extinguishing, serial communication interface, fire alarming telephone and button, and program storage, etc. The microcomputer system gathers the signa1 from smoke-, temperature- and fire light-sensors, and makes logical decision and sends out different alarming signal. When working, the micro computer system sends out the detecting signal continuously, which is attached to the Sensors by interface circuit in order to monitor thesmoke, temperature and fire light at the field. The feedback signals from the detectors are delivered to monolithic microcomputer system. Contrasting the returning signals from the smoke, temperature and light-sensors with the normal limit value, the units system can get judgment thatis one of the four states, i.e. normal, trouble, abnormal and fire disaster, then the relevant management is taken through the interface circuit. If fire disaster is confirmed, the unit wi1l send out sound and light a1arrning signal, and inform the main control system. In addition , it will report the address code of the accident site, the type and degree of the trouble to the main system. After confirming the fire disaster the main gontro1ler will back feed signa1 to the branch units and Start the fire-extinguishing device. Simultaneously the main system also will inform this group of units to send out a1arming signal, that shows that the fire has happened there, and warns one’s attention to take relevant emergency measures, e. g to disperse population, save the confidential documents and valuable property. If the detectors are out of order or there is troublein the fire-alarming circuit, ones can use the fire-alarming button and telephone to report directly the fire signal to the controller System.Sensor.(1) The temperature-sensor. It uses the composite (temperature difference and fixed temperature) detector, the detector is composed of two types of material which have different coefficient of expansion. When temperature raises rapid1y, if the rate reaches or exceeds the set rate of the detector, the thermo-block will start and send out alarming signal immediately.(2) Smoke-sensor. It is composed of the checking ionization chamber, the compensation ionization chamber, the signal magnifying circuit, the switch changing circuit, the fife simulated circuit, the trouble auto-detecting 1oop and confirming lamp Loop etc. When there is no smoke the voltage between the both end of the checking chamber and the compensation chamber is almost equal. When the smoke comes into the checking chamber, the ionization e1ectric charge moving rate will drop and the ionization e1ectric current wi1l reduce, thus the equivalent impedance of the checking chamber will increase and the impedance in the compensation chamber will keep cons1ant, therefore the ratio of the divided voltage in the ionization chamber is caused changing and that brings about at the inputting end of the signal manufacturing loop. When the voltage increased and reached some fixed value, the switch changing circuit would act immediately.(3) The light-sensor. It is a special sensor that can distinguish between the fire light and other light source. It will identify the fire light from many types of light source. Meanwhile it can also distinguish between strong and weak of the light, and whether or not the fire light source in the daily life, when it is verified to be fire disaster Light source the fire alarming signal will be sent out to branch system.The interface between the monolithic micro-computer of the unit and the fire alarming system. The monolithic micro-computer system of the unit is the least application system of the MCS-5l monolithic microcomputer, it is joined with P1interface. The fire alarming interfacesci1cuit is respectively: P1,0collecting the temperature-sensing signa1, P1,1collecting the smoke-sensing signal , P1,2 collecting the fire light-sensing signal, P1,3 to P1,7 are control signalsof the alarming circuit, they are respectivel1y that: P1,3 is output end of the trouble signal of the temperature sensor, P1,4 output end of the trouble signal of the smoke sensor, P l,5 the output endof the temperature abnormal signal , P1,6 is the output end of the smoke abnormal signal P1,7 is the output end of fire alarm. When P1,3 to P1,7 are high level it is shown that abnormal situation will take place (trouble, abnormal or fire disaster).The composition of the maim controller for fire disaster intelligence alarming. The fire disaster intelligence alarming main system is composed of CPU, the program memory RAM, the data memory ROM, the alarming circuit, the display circuit and the serial communication interface circuit, etc.The Application SoftwareThe branch unit software. The main program block diagram of the branch unit is shown in fig. 4. The steps are:Program initiating, set up probe signal, distinguish whether or not sensor normal, input smoke signal, distinguish whether of not high temperature occurrence, input light signal, distinguish whether or not fire light, occurrence. When the signals all or any two of them are valid, the fire disaster will take place. At this time it will give fire alarming, otherwise there is abnormal at the monitored site. The communication between branch unit and main system uses the interrupt way of serial interface the flow chart of the interrupt program, is omit ell.Fig. 4 The main program of the unitThe software of the main system. The function of the main system is detecting the work stateof each unit. At first, the initial state of every units must be set, then every units are checked in back and forth. If abnormal situation is found the corresponding management will be taken, immediately, the checking block diagram of the main program for the main system is shown in fig. 5. Its executing process is: to set the number n of groups, the number m of units in each group, to check units whether or not normal, if they are normal then the number of the unit is added 1, or else if abnormal there is trouble or the fire disaster. After managed appropriately, the unit number is added 1. In this way every units are checked.Fig. 5 The checking frame in main program of main systemConclusionPreventing fire is one of the problems that are worth attaching great importance to for development and utilization of underground space. The paper recommended a fire disaster intelligence alarm system which is composed of the main system and some branch-system. The state in the underground building is monitored by the smoke-, temperature- and light-sensors set at the field and the signal back feed to main system, then the main system should alarm and start fire-fighting device, if fire happened. The system is applicable to general underground building.Reference[1] Qiao Jingxu: Underground space (in Chinese ), V ol. 12, No. 4 (1992)[2] Keji Kojima Tunneling and underground space Technology V ol. 5, No.4 (1990)[3] T. Tatsukami, TUST. V ol. 1, No. 1 (1986)[4] Raysterling et al, TUST V ol. 7, No. 2 (1992)[5] Fystein Meland et al, TUST V ol. 9, No. 1 (1994_[6] Thomas J. Frost, Underground space V ol. 9, No. 4 (1985)。