modern trends in fire protection system ver-4 aug,2003-paper

7/30/2019 Modern Trends in Fire Protection System Ver-4 Aug,2003-Paper

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MODERN TRENDS IN FIRE PROTECTION SYSTEMS

V.P.GUPTA, C.E. [E] B.S.N.L, NEW DELHI

E-mail: [email protected]

Website: www.electricalzone-bsnldelhi.com

(An ISO 9001:2000 Unit)

1.0 OBJECTIVE:

The objective of this paper is to understand the modern trends in fire detection

and extinguishing system, and to discuss its possible application in Telecom

installations. A telecom installation with high concentrations of cables and

electronics switching equipment within relatively small areas constitutes a HIGHRISK installation. The paper is broadly divided into following sections:

- BACKGROUND & EXISTING SYSTEMS.- MODERN TRENDS IN FIRE DETECTION SYSTEMS.

- MODERN TRENDS IN FIRE EXTINGUISHING SYSTEMS.

- CONCLUSION.

2.0 BACKGROUNDS & EXISTING SYSTEM:

2.1 Modern telecommunications network plays a key role in todays world and isrequired to be continuously operated even in the most adverse conditions. The

Engineering Services in the buildings housing modern telecommunications

network must perform to an exceptional degree of reliability so as to ensure thatthere are no breakdowns in the telecommunications system. The safety and well

being of the buildings, human inhabitants and its material contents including

Telecom equipment depend on the smooth and reliable operation of variousservices.

2.2 Fire has been acknowledged as the most powerful substance of the nature and the

fountainhead of human civilization. But an unforeseen circumstance may resultinto uncontrollable flames of fire that may raze to the earth the very edifice of

progress and shatters the hopes, leaving behind only a bitter taste of misery,

agony and despair.

2.3 Thus arises the most important question of preventing and controlling the fire

when it takes its worst form. For prevention of fire, it is necessary that the same isdetected by an early warning system so that fire fighting measures can be taken

before fire takes an uncontrollable form. The properties of the fire that it is

accompanied either by smoke or heat are used in a fire alarm and detectionsystem. The smoke or heat is used in a fire alarm and detection system. The

smoke and the heat detectors uses one of these properties of the fire and acts as

the sensors for generating the required alarm signals through a control panel. For

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extinguishing the fire, the oxygen at the point of fire is reduced from normal 22 %

concentration to below 16 % by covering the fire by suitable chemical, Blanket,

gas etc. or water is sprinkled / poured over the fire so as to reduce the temperaturebelow the combustion temperature.

2.4EXISTING SYSTEM:

As per the existing instructions in the department, all

exchanges of 1K and above are provided with fire

detection system. As per the departmental Fire protection Manual, issuedin November, 1997, these exchanges are provided with an automatic fire detection

system consisting of combination of heat, photo and ionization type, smoke

detectors, manual call boxes, response indicators, local control panels, main

control panels, public address system, along with talk back system to provide forcommunication between main control panel and local control panel and vice-

versa. The fire fighting appliances, as per the Fire manual of the departmentconsist of wetriser system for high-rise buildings, automatic sprinklers forbuildings exceeding 45 mts. and for basements, Portable fire extinguishers 4.5Kg

Carbon-di-oxide type and trolley type carbon-di-oxide fire extinguishers.

2.5 The fire detection installations are to be provided in such a manner that they are

efficiently maintained and gives a high degree of reliability so as to generate

reliable alarm and fire signals. It is seen over the years that a conventional firedetection system detects 95% of false alarms as fire alarms, thus, causing a lot of

inconvenience and disruption in the production process. The carbon -di-oxide

type extinguishers are also having limitations such as suffocation and reduced

visibility. In case of CO2, there could be chance of thermal shocks and generationof static electricity, which may damage telecom equipment. Because of

limitations of the existing system and in view of the development of modern fire

detection and fire protection system, it is necessary to examine the possibility ofusing some of the modern fire detection and protection system for protecting our

Telecom. Installations.

3.0 MODERN TRENDS IN FIRE DETECTION SYSTEM:

The modern trend is to provide one of the following automatic fire detection

systems for protecting the Telecom. Installations.

- HIGH SENSITIVITY SMOKE DETECTION SYSTEM [HSSD]

- LINEAR HEAT DETECTION CABLES [LHD]

- ANALOGUE ADDRESSABLE INTELLIGENT SYSTEM.

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3.1 HSSD SYSTEM DESCRIPTION:3

4 High sensitivity smoke detector is a relatively new form of smoke detector. It isan aspirating detection system which comprises of:

-Pipe work to collect samples of Air from the protected area.

- High sensitivity Detector capable of detecting smoke concentrations as

low as 0.01% per meter.

- A fan to draw air through the pipe network.

- A display and control card to show increased smoke levels in increments

from 1-10 and provide the necessary alarm outputs.

HSSD system provides smoke detection sensitivities upto 500 times greater than

conventional point detectors. Fig. (1) illustrates the incipient stages of fire and

contrast the relative response of detectors.

3.1.1 HSSD PRINCIPLE OF OPERATION:

HSSD is a digital particle counter utilising advance optics and electronics. A fanthrough a ducting / pipe system continuously draws air from the high value

components. A laser is focussed by a lens assembly to provide a high intensity

spot of light within the centre of the air stream. This spot is 100 micron indiameter, which provide good light intensity to be scattered by a particle entering

at this point. Focussed at this point is the light receive optics which transfers the

photons of lights scattered by each particle to the receive electronics. Thethroughput of particles is effectively counted through integration circuitry, which

then convert the digital system to an analogue where smoke density is displayed

on 1 to 10 segments Bar Graph. The electronic of the system ignores pulsesgenerated from particles over 10 microns, thus, effectively, discriminating against

false alarms due to dust or environmental conditions.

The system has been used in some Telecom. Applications in West [M/S KIDDEUK]. System has FM approval.

3.1.2 HSSD CAPABILITIES:

HSSD is capable of detecting smoke as low as 0.01% obscuration per mt. - which

contrasts with conventional point detector operating in the 3% to 5% obscuration

per mt. range. HSSD is particularly suited for protection of High value [high risk]areas and can supplement the conventional point smoke detection system. It

provides the earliest indication of any smoulder long before visible smokeconfirms the presence of fire. Thus, it can sense just an overheating cable or

component of Telecom. Equipment well before the outbreak of fire. Early

detection means that the user has time to automatically respond and shut down of

local power and air handling systems and HSSD thus, can pre-emptive the realfire. This system provides 3 levels of indication from the Control panel:

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. ALERT

. ACTION

. ALARM

There are volt free contacts and can be set against any bar graph display of thecontrol panel, which gives visual indication of increase in smoke level in 10%

increments. The system is normally used in conjunction with conventional

automatic fire detection system. However, in case it is used as stand alone type,then two levels of alarms shall be permissible, designated as pre-alarm and fire.

3.2 LINEAR HEAT DETECTION CABLES:

3.2.1 LHD SYSTEM DESCRIPTION:

Linear heat detection [LHD] cable based system provides economical temperature

monitoring thereby fire detection capabilities at the precise point of risk. They arereliable, flexible and have ability to detect abnormal temperature variations of fire

before the break out. LHD system is a continuous heat detection cable capable ofmeasuring and reporting adverse changes in temperature at a spot location. Linear

Heat detection is

- Continuous heat detector in the form of cable.

- Analogue [Alarm line] averaging heat detector or rate of rise.

- Digital [KIDDE BICC] Point of risk heat detector Fixed temperature.

3.2.2 LHD PRINCIPLE OF OPERATION:

ANALOGUE [ALARM LINE]: Alarm Line high resistance sensor cable is a 4-

core cable. Two cores for monitoring and two cores for sensing temperature

changes. An increase in temperature reduces the resistance value of the cable.This value is measured by associated electronic interfaced unit, which provides

the alarm indication once the pre-determined alarm level has been reached. The

cable senses the rate of rise of temperature and not the fixed temperature.

DIGITAL [KIDDE BICC]:Digital heat sensor cable is a twin conductor cablewith temperature sensitive insulation. The cable operates by melting [thereby

short-circuiting] once the temperature of sensor cable is exceeded. Unlike

analogue [alarm line] the operating temperature is fixed within the temperaturerating of the temperature sensitive insulation. The temperature alarm setting

depending upon the outer sheet of the cable used and the requirement can be seenas under:

ALARM COATING

70 C Polythene

90 C Polythene

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113 C PVC

180 C PVC

238 C Fluoro Polymer

The digital cables can be directly connected into a fire panel as a zone.

These cables can be effectively installed to protect the cable runways or the

telecom racks. M/S KIDDE UK LHD has FM approval.

3.2.3 LHD PROPERTIES:

The properties of the two type of cables are as under:

ANALOGUE ALARM LINE DIGITAL KIDDE-BICC

1. Rate of rise Average Heat detector. Fixed temperature. Point detection.

2.Recoverable up to 150 C Temp. Not recoverable as it melts/ short circuit.3.Open & short circuit fault indicator. Only open circuit fault indicator.

4.Minimum Alarm Temp. 35 C Minimum alarm temp. 61 C

5.Maximum alarm Temp. 105 C Maximum Alarm temp. 238 C

6.Maximum length 1000 mt. Maximum length 10,000 mt.

7.Event Location {Due to 2 core of

Monitoring]

No event location.

3.3 ANALOGUE ADDRESS INTELLIGENT FIRE SURVEILLANCE SYSTEM:

3.3.1 SYSTEM DESCRIPTION:

- Analogue The feedback from the sensors is in the form of Analogue Counts. The

value of these counts changes depending upon fire, fault, dust conditions and can

be analysed by the micro processor.

- Addressable The detectors have a fixed address which can be read by the

control panel and the sensor can be addressed by the control panel.

- Intelligent The micro processor in the control panel provides the intelligence and

the decision making is through this micro processor.

The system hardware (fig. 2.0) depends upon the actual requirement and usually

has combination of the following:

[a] Control panel

[b] Sensors

[c] Bells/ Sounders[d] System Wiring and Fittings.

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[e] Power Supply Unit.

[f] Optional Items:- Repeater Control Unit, External status Interface, Personal

Computer/ Networking.

CONTROL PANEL: The Control panel {figure 3.0] is having micro processor

on a PCB that automatically controls the system. The control panel holds acombination of electronic circuit cards as per the site requirements for pulse bells

and sensors. They also provide interface to external facilities through peripherals

printed circuit boards. The key pad on the control panel enables certainsupervisory function to be undertaken. It also provides for authorised only coded

access to enable certain system functions to be interrogated for maintenance.

Access to the control panels itself is by key. A built in printer is a standard item

on the control panel.

SENSORS: As per the site requirement combination of following sensors also

termed as field units/input devices is provided:

- Analogue Addressable ionisation smoke detectors with dual ionisation

chamber.

- Analogue Addressable optical smoke detectors, photo electric type using

internal infrared light source.

- Analogue Addressable fixed temperature, heat detector and rate of risehear detectors.

- Analogue addressable manual call Point / Breakglass Unit:- With frangible

glass, splinter protected for activation by manually breaking the glass.

BELLS / SOUNDERS: The externally wired bells and electronic sounders/ PA

system provide audible warning to emergencies. The Bells/Sounders can createdisturbances on the system and thus, have to be properly chosen.

SYSTEM WIRING AND FITTINGS: Two wire cable is used for linking the

sensors and the control panel and for the PA system / interface unit etc. etc. Thewiring is looped [fig. 4.0] and in some cases, a standby [loop] is also provided so

as to make the system fool proof. Fittings such as short circuit isolators are fixed

at strategic position to isolate sensors section in case of break or fault. Generallyone isolator is provided for every 20 devices.

POWER SUPPLY UNIT: Two 12 volts sealed lead acid batteries provide the

24volt DC supply to operate the system. The batteries are on constant charge froman integral charging unit fed through AC MAINS.

OPTIONAL ITEMS:

Repeator control unit for monitoring of system at strategic or remote locations can

be provided. Status interface can be provided for linking the system with personal

computer., in networking or external building management system.

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3.3.2 PRINCIPLE OF OPERATION:

The Analogue addressable intelligent fire surveillance system uses state of-

the-art microprocessor control with built in Software programmes to maintain

automatic two ways communication with a large number of remote sensors whichdetects fire and smoke. The system provides for an activation signal to be

transmittted by any sensor to the control unit and also enables the operational

readiness of each sensor to be routinely monitored.

The detectors used in the system are addressable analogue detectors. Unlike the

conventional detectors, the analogue detector does not operate on the threshold

basis. The analogue voltage signal produced by the activation of the detector isconverted into a analogue count by the electronic circuitory and transmitted to the

control panel on interrogation. The unique address [1 to 126] of the sensor

provided by means of XPERT CARD/ DIL [DUAL INPUT LINE] switch

[fig.5] is read by the microprocessor whenever the sensor is addressed by thecontrol panel.

Built in programmes address and interrogate in turn each sensor in the system.

The interval between addressing any sensor is 2 to 3 seconds depending upon the

number per loop. Each sensor responds with a signal indicating that it is inoperational readiness. Though the principle of operation may vary from

manufacturer to manufacturer, a commonly employed method is on the pulse

position modulation principle. Each and every detector is scanned by the pulses

generated [fig. 6.0] from the control panels and feedback is processed by thecontrol panel to generate the required signals. Intelligent pulses of 5 to 9 volts are

super-imposed on the DC supplies 17-26 volts on the two wires.

Since there is a constant communications between the Control Panel and the

various detectors, the exact condition of the detector is conveyed to the Panel in

the form of an Analogue count [1 to 126]. It gives the information that thedetector is non-functional / fault/ dead [count of 1 to 12], normal/ healthy[15 to

40]. A count of 40 to 55 is a pre-alarm stage which is generally due to non-

maintenance of the detectors or the poor environmental conditions. This

information is extremely important because timely action by the supervisor canprevent the false-alarm. A condition beyond 55 is generally an alarm condition. It

is this feature of the intelligent system which is the most important , useful and

powerful in comparison to the conventional system.

The programmes routinely execute supervisory commands within the control unit

to validate the operational readiness of the electronic curcuits. On . switching on,the control unit automatically calibrates each sensor against its ambient

temperature or particular level as appropriate, ensuring constant sensitivity of

sensors throughout the systems. The calibration, together with lamp testing is

performed routinely every day at a fixed time.[say 1200 hours]. Through systemsoftware.

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The system is able to discriminate between a false alarm and the real fire

conditions by analysing various fire characteristics and environmental conditions.[ref. Fig. 7.0]

EXAMPLE A: Is it a fire or not [Cigarettes , toast smoke or transient]

Smoke enters the detector for a short time [time scale : seconds] , the

concentration rises and drops quickly, whereas a simple detector system couldregrettably register this as a fire alarm. Addressable panel recognise the

characteristic behaviour pattern and inhibit an alarm.

EXAMPLE B: Reaction to a genuine fire:

When a genuine fire develops, the smoke [or heat] concentration grows rapidly

for a longer period [time scale: Seconds/minutes] . The response from addressable

analogue, detector with its stored behaviour pattern decides that the alarm mustbe raised without delay.

EXAMPLE C: Reaction to smoldering fire [Burning of plastic cables/ wires etc.

etc.:].

The gradual build up of smoke in the detector is recognised as the precursor to afire and alarm limit is lowered, so as to speed up response and ensure the earliest

possible help [Time Scale: Minutes, Hours].

EXAMPLE D: The slow build up of dirt in detectors is recognised and the

control panel raises the alarm limit so as to extend service intervals, without

compromising reliability of detection. Pre Warning of a detectors dirty conditionis given well before a false alarm occurs [Time Scale : Months/Years].

3.3.3 ANALOGUE ADDRESSABLE INTELLIGENT SYSTEM CAPABILITIES:

The system is stand alone type, but can be interfaced with virtually any fire

detection installations if required to provide a coordinated fire survillance system.

The system has following capabilities.

[a] Activation of first and second stage alarm.

[b] Sequential display of alarm and system function with 2 X 40 character

[even higher] [simultaneous display of 2 alarm in some cases][c] Operation of public address and other systems.

[d] Operation of automatic shutdown of air conditioning plants, hazardous /vulnerable process, fire doors etc. etc.

[e] Delayed action of specified function [for example release of halon gas] for

protection of evacuating personnel.[f] Operation of halon gas and other fire protection system including

activation of wet riser system.

[g] Debarring of security exit.

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[h] Print out of the alarm with time and date.

[i] The micro processor memory automatically stores 200 or more latest

system events and these are available for interrogation through Keypad.[j] Optional interface when connected with the systems can provide for the

following additional capabilities.

Outward communications by modem via public telephone system /

private network to any remote point to provide status information and

or to initiate an action.

Outward communication to external information management system

through a Personal Computer Control which can include graphics ,

displays and annunciation devices , including public address.

Remote control of the systems.

Record of Electrical parameters like Voltage Fluctuation, Frequency

fluctuation , Tripping off of ACB etc. etc., with the help of Auxilary

Contacts.

3.3.4 THE ADVANTAGES OF ANALOGUE ADDRESSABLE SYSTEM OVER

CONVENTIONAL SYSTEM CAN BESUMMARISED AS BELOW:

- Large number of detectors in one loop and flexibility:

In the conventional system , in a zone we can connect maximum 20 detectors and

alarm indication is on area wise basis. Whereas in intelligent system, we canconnect large number of detectors [1 to 126] (even upto200) in one loop and each

detector point is represented independently on the panel. Additional sensors can

be added without major design or wiring changes.

STATUS DISPLAY:

In the conventional system , the indication is through LED, whereas in the

microprocessor system, the indication is through 2 X 40 (or 2X80) characters

Fluroscent Matrix display by which exact location can be read.

PROGRAMMINGFOR EXACT LOCATION OF FIRE:

In the conventional system, no programming can be done to feed data to facilitatethe security people to know from the Control panel itself, the exact location of

fire. Whereas in intelligent micro processor system, the complete programming ispossible to know at the panel, the exact location of the fire / alarm like Floornumber, Room number, Detector number etc. etc.

HEALTHINESS OF THE DEVICES AND ADJUSTMENT OF DETECTOR

SENSITIVITY:

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In the conventional system , it is not known whether a particular smoke detector is

in a working condition or not, therefore, it needs periodical check of each detector

for its functionability which is impossible in a big complex. Whereas in aintelligent system, the status of each and every detector is checked up and if any

detector goes bad the indication comes on the panel. In addition to above, the

sensitivity of detectors can be changed.

DIRTY PRE-WARNING FOR DETECTORS:

In the conventional system, it is not possible to check the sensitivity of the

detector because of which after sometime, the system starts giving false alarm

because of dust accumulation. Whereas in a addressable system, the sensitivity of

each detector is checked. Pre Warning Alarms are generated if a Detectorbecomes hyper sensitive and needs cleaning , thereby reducing false alarms and

maintenance problems.

CONNECTION WITH WET RISE FIRE FIGHTING SYSTEM:

You can connect in the same loop of detectors, the pressure switches , levelswitches etc. of Hydrant and Sprinkler System through Interface unit which is not

possible in the conventional systems.

SIMPLE CABLING:

The Repeater panel / Zonal panel is connected through wires for the signal to be

transmitted to the Main panel. In a conventional system multicore cables arerequired and there is a limitation of number of detectors connected in a zone,

whereas in the Addressable system 2 core cable is sufficient for large number of

detectors.

ORIGIN / FLOW OF FIRE:

In conventional system, the origin of fire cannot be ascertained, whereas in

computerised system even the area of fire and its origin can be identified

alongwith the flow of fire.

DISCRIMINATION BETWEEN GENUINE FIRE AND OTHER

CONDITIONS:

For every genuine fire conventional system gives about 24 unwanted or false

alarms. False alarms are eliminated as explained in examples [fig. 7.0].

ISOLATION OF FAULTY DETECTORS / OUTPUT DEVICES/ AREAS

UNDER MTCE. :

Faulty detectors/devices or areas under mtc can be isolated by providingisolators.

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LOGGING OF PAST EVENTS:

200 past events are stored and automatically updated when new events are

reported. Whereas no such facilities are available in the conventional system.

EASE OF MAINTENANCE:

Pre-Warning , automatic monitoring of devices and less cabling reduces themaintenance efforts.

3.3.5 COST COMPARISON WITH THE CONVENTIONAL FIRE DETECTION

SYSTEM:

An attempt is made to compare the cost of analogue addressable intelligent fire

survellience system with a conventional fire detection system for a MAINTelephone Exchange Building which normally consisting of three stories with

half basement.

It is assumed that only one new technology exchange is to be installed in the

building. The rates for comparison purpose has been taken from the market onoral enquiry and may slightly vary.

Sl.No

.

Item Quantity Analog addressable

System

Unit rate Total

[in Rs.] [in Rs.]

Conventional Fire

Detection System.

Unit rate Total

[in Rs.] [in Rs.]

1. IONISATION 150 2550 382500 1200 180000

2. PHOTO 50 2250 112500 1150 57500

3. HEAT 50 2100 105000 1100 55000

4MANUAL CALL

POINT

10 2500 25000 475 4750

5 HOOTER 10 2200 22000 500 5000

6RESPONSE

INDICATOR

100 - - 100 10000

7ISOLATOR

MODULE

20 2250 45000 - -

8 PANEL MAIN 1 250000 250000 50000 50000

9ZONAL [4 NOS. 10

ZONE EACH]

4 - - 20000 80000

10. CONDUIT WIRE1000MT.2x15

@Rs.55/-

55000 2500 Mt.2X1.5

@Rs.55/-

137500

11. PA SYSTEM 2 X 1 5000 5000

GRAND TOTAL 1002000 584750

Difference 4,17,250/-

3.3.6 The analogue addressable system can further be linked to a computer and can also

have a networking facilities at extra cost. It is seen that in the Indian conditions,

the cost of the analogue addressable system is roughly 1.71 times that of a

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conventional system. However addressable system control panel can

accommodate upto 120 detectors in each loop and upto 8 loops ie., total of 120 X

8 = 960 Detectors, whereas conventional panel taken in the above table canaccommodate total of 15 detectors in each zone and with 4 zonal panel total

become 4 X10X15=600 Detectors. Thus, with a system having about 900

detectors, the cost of the system may be equal.

4.0 MODERN TRENDS IN FIRE EXTINGUISHING SYSTEMS:

- FIRE TRACE EXTINGUISHING SYSTEM.

- HALON ALTERNATIVE EXTINGUISHING SYSTEM

(A) TOTAL FLOODING AGENTS

(B) PORTABLE FIRE EXTINGUISHERS

- WET RISER & SPRINKLERS.

4.1 FIRE TRACE EXTINGUISHING SYSTEM

4.1.1 SYSTEM DESCRIPTION:

The system consists of following:

- A specialized flexible Fire detection and Fire extinguishing Delivery tube.

- The tube is wrapped around or installed within the Protected equipmentExchange Racks, cabinets etc. etc.

- [Avoiding surface above 80 C]

-Fire extinguishing media cylinder connected at one end of the tube, thus,the tube is charged with extinguishing media.

4.1.2 PRINCIPLE OF OPERATION:

When an area is overheated or should a small fire take place the tube adjacent or

above the fire will soften and burst at hottest point allowing swift and accurate

delivery of the extinguisher directly to the source of the fire.

4.1.3 FIRE TRACE ADVANTAGES:

The system does not require Electricity / or battery supply for operating thedetection system. It has no wiring, detectors or control panel. It can be connected

to any extinguishing agent depending upon application and has been approved by

LOSS PREVENTION CONTROL BOARD

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4.2 HALON ALTERNATIVE EXTINGUISHING SYSTEM:

4.2.1 Halon is a very effective fire extinguishing agent. However, because of the high

ozone depletion potential, its use has to be phased out as per the provisions in

Montreal protocol without comprising with Fire safety. As per Government ofIndia Ministry of Home affairs & DGCD [Fire Cell] letter dated 6.12.99, the

following HALON alternatives have been identified.

[A] ALTERNATIVE FOR HALON 1211 PORTABLE FIRE

EXTINGUISHERS ARE:

(I) ABC Powder extinguisher.(II) Co2 squeeze grip type extinguisher.

(III) HCPC based compounds like NAF P IV, Halotron , FE-36 etc.

[B] ALTERNATIVE FOR HALON 1301 FIXED FIRE PROTECTIONSYSTEMS ARE:

[i] CO2 fire extinguishing in-cabinet and subfloor systems, including low

Pressure CO2 systems.

[ii] Inert gas extinguishing systems [nitrogen based][iii] Water mist fire extinguishing system.

[iv] Fast response sprinklers.

[v] Halocarbons such as HFC 227 ea(FM-200), PE-13, HCFC blends,

The HALON alternatives as above can be classified und[NAFS 111]er following

categories.

[i] TRADITIONAL FIRE PROTECTION AGENTS:

The use of traditional non-halon fire protection materials such as dry chemical,

CO2, water sprinkler and foams to protect special hazards has been promoted as a

mean of replacing halon use. The degree to which these traditional, not-in-kind

alternatives can successfully replace halon will depend on the details of hazardbeing protected.

[ii] HALOCARBON AGENTS:

These are chemicals agents that contain chlorine, fluorine, or iodine eitherindividually or in chlorofluorocarbons. Classes of agents include

hydroperfluorocarbons [HCFCs], hydrofluorocarbons [HFCs] , perfluorocarbons

[PFCs] and fluroiodocarbons [FLCs]. These agents share several common

characteristics, with the details varying between chemicals. These commoncharacteristics include the following:

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- All are electrically non-conductive.

- All are clean agents [vaporize readily and leave no residue]

- All are liquefied gases or compressible liquids.

[iii] INERT GASES:

Inert gas systems are designed to reduce the ambient oxygen concentration in aprotected space to between 10 14%, a level that is breathable but will not support

flaming combustion. These systems use inert gases such as argon and nitrogen,

either as mixtures or alone. Inert gases are electrically non-conductive cleanagents.

[iv] WATER MISTS:

Water mist systems using small amount of water released as tiny droplets under

low medium or high pressure. These systems use specifically designed nozzles toproduce much smaller droplets than are produced by traditional water-spray

systems or conventional sprinklers. The smaller droplets are more effective in

extinguishing fires; therefore, less water is needed.

[v] POWDERED AEROSOLS:

A category of new technologies being developed and introduced are those

conventional solid particulate and aerosols. The difference between powderedaerosol systems include pyrotechnically generated aerosols and dry chemical /

halocarbon agent mixtures. Another unique category of fine particulate

technology is gelled halocarbon / dry chemical suspensions. Dynameco , NAF

SIII as flooding agent, NAFP IV as streaming agent.

4.2.2 THE ENVIRONMENTAL ISSUES:

Montreal protocol deals with ozone depletion potential [ODP] of halon. However

now it is recognised that halon replacements can have significant effect on Global

climate due to their Global warming potential [GWP] and Atmospheric life time[ALT] as they can remain active in the stratosphere for many years. The table

below compares Environmental Critical parameters for some of extinguishing

agent

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[A] TOTAL FLOODING AGENTS

CRITICAL

PARAMETERS

NAF SIII [Aerosol] FM-2000 Halon 1301

Ozone DepletingPotential [ODP]CFCII= 1

0.036 0 16-20

Global WarmingPotential [GWP]

Co2= 100 Years.

1444 3300 5600

Atmospheric Life

Time [ALT]

12 years 42 years 65 years.

[B] TOTAL STREAMING AGENTS

CRITICAL

PARAMETERS

NAF PIV HALON 1211 PFC

ODP

CFCII=1

0.01 5.1 0

GWP

CO2-100 years]

340 Not avail 6800

ALT 1.7 25 3200

4.3 WET RISER & SPRINKLERS:

These are continued to be provided for high-rise buildings and basements as perlocal Fire byelaws and Fire Protection manual of the department.

5.0 CONCLUSION:

5.1 HSSD and LHD fire detectors systems are very advanced and recent system.Though they have been used in some Telecom installations in western countries,

but they have not been adopted for use in developing countries so far. It will be

better to study these systems in detail before they are considered for use in our

telecom installations.

2.1 It is noticed that it has become increasingly difficult for the maintenance staff to

effectively maintain a conventional fire detection system and as can be seen fromthe advantages of the fully addressable analogue system, the analogue intelligent

system is a self-correcting system and can provide for highly reliable fire, alert or

fault alarms. The system also provides advance indications for carrying out thecleaning of the detectors/ sensors. The system has networking facilities and the

system conditions can be monitored from a centralised location. However, it is

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seen that the system is to be provided in an environment wherein the temperatures

are within -10 to 45 C with up to 95% relative humidity. Thus, it is mandatory

that the main control panel of a intelligent system is provided in a controlledenvironment as against the existing practice of providing conventional fire alarm

panels at the entrance in the buildings. The systems are now available in India and

have been provided in some departmental installation. They are now cost effectivefor high-rise buildings / large areas and for these areas they can be encouraged.

5.3 FIRE TRACE CABLES:

These cables are to be connected with total flooding agents. In the departmental

telecom. Installations, total flooding has not been adopted so far. However, as

these cables are to be provided only for a limited area i.e., equipment rack anddoes not require any electricity or power back up, it is recommended that on trial

basis we may provide this system in one or two Exchanges.

5.4 HALON ALTERNATIVE EXTINGUISHING SYSTEM:

As per the Fire Manual of the Department, so far we have been using only CO2type of extinguishers. However, some of the extinguishing medium like FM200,

NAF S III, NAF PIV, Nitrogen based inert gases system can be provided on

experimental basis for some of the Key Telephone Exchanges.

5.5 REMOTE MONITORING OF FIRE DETECTION SYSTEMS:

For rural telephone exchanges remote monitoring of fire detection systems to beintroduced.

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Figure 6.0

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Figure 7.0

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modern trends in fire protection system ver-4 aug,2003-paper

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