FIRE DETECTION & ALARM SYSTEMFIRE DETECTION & ALARM SYSTEM

RAVI SHANKAR SINGH(E6S304)

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Why are fire detection and alarm systems required?

Detect fire in the areas.Notify building occupants to take evasive action to escape the

dangers of a hostile fire.Summon organized assistance to initiate or assist in fire control

activities. Initiate automatic fire control & suppression systems & to sound

alarm.Supervise fire control & suppression systems to assure operational

status is maintained Initiate auxiliary functions involving environmental, utility & process controls

Systems may incorporate one or all of these functions

Block diagram of FDA systemBlock diagram of FDA system

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Input Devices

OutputDevices

Control Panel

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Input Devices

Fire Box (Manual Pull Station)When shorted trips an alarm (usually fire) Installed in the normal exit path

Types of Fire BoxSingle Action

Pull handle once

Glass Break Glass rod or plate is broken

Double Action Lifting of a cover or opening a door

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3.1) Heat detectors 1. fixed temp type heat detector2. rate-of-rise type heat detector

3.2) Smoke detectors1. Photoelectric2. Ionization

3.3) Flame detectors1. Ultraviolet light (UV)2. Infrared (IR)

3.4) Fire-gas detectors

FIRE DETECTORS

Input Devices

Heat Detectors

Smoke Detector

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Fixed temp. heat detectors Fixed temp. heat detectors

Detect heat by one or more of 3 primary principles of physics:

Expansion of heated material Melting of heated material Changes in resistance of heated material

Rate-of-rise heat detectorsRate-of-rise heat detectors Operate on the principle that the temperature in a room will

increase faster from fire than from atmospheric temperature Will initiate an alarm when the rise in temp. exceeds 12-15F (7-8C)

per minute Alarm can be initiated at a temp. far below that required for a fixed-

temp. device

◦Reliable devices, not subject to false activations◦But if not properly installed, they can be activated under non fire

conditions (eg. detector located too close to doorway and subject to extreme fluctuations in temperatures)

Pneumatic rate-of-rise spot detector Pneumatic rate-of-rise line detector Thermoelectric detector

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Photoelectric smoke detectorUses a photocell coupled with a specific light source.

Basically smoke entering the smoke detector chamber disrupts the

light beam causing an alarm signal to be initiated

More sensitive to smoldering fires

1: optical chamber2: cover3: case moulding4: Photodiode (detector)5: infrared LED

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Circuit of Photoelectric Smoke Detector

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Ionization smoke detectorInvisible products of combustion enter the chamber

decreasing the current between the –ve & +ve plates, thereby

initiating an alarm signal.

Generally responds faster to flaming fires versus smoldering

fires

Automatically resets when the atmosphere clears

Fire-gas detectorsFire-gas detectors

Monitors levels of carbon dioxide and carbon monoxide

(common to all fires)

More discriminating than other detectors – can be designed to

be sensitive only to gases produced by specific types of hostile

fires and ignores gases produced by friendly fires

Not many in use – very specialized applications

Combination detectorsCombination detectors

Single device can be designed to have more than 1 function eg.

heat/smoke, smoke/carbon monoxide detectors

Different combination make the detectors more versatile and

more responsive to fire conditions

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S.No PLANT AREA TYPE OF DETECTORS

1. Main control room, Computer room, Electronic cubicle room and control rooms in outlying areas.

Combination of -

Ionisation smoke detector

Optical type smoke detector

2. Switchgear rooms in main Plant and outlying areas, battery charger room, record and shift-in-charge engineers room

Ionisation type smoke detector.

3. Office rooms / storage rooms Ionisation type smoke detector

4. Battery rooms and chemically corrosive areas.

Corrosion resistant, Rate of rise of temperature heat detector with fixed temperature setting.

5. Cable gallery Combination of Optical type smoke detectors and Linear heat sensor running above all HV and LV power cable trays. Unless the vertical distance between cable tray is less than 500 mm in which case alternate trays (in addition to the top and bottom trays). The optical smoke detector and LHS detectors along with necessary number of interface units in the cable gallery will be cross zoned to actuate the water spray system

6. Station building / Plant area Infrared flame detectors (where oil tanks are located), spray tanks rate of rise of temp. detector with fixed element

Selection of Detectors for different Area

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7. Coal Conveyors Analogue Linear heat sensor cable, infra red spark / ember detectors and manual call points. If water spray system is provided the LHS cable and IR detector will be cross zoned to actuate the same

8. Dusty areas in coal handling plants like crusher house

Flame proof manual call points

9. Junction towers Flame proof heat detectors, flame proof manual call points

10. Conveyor tunnels Flame proof infrared detectors, flame proof MCPs, LHS cables

11. Hazardous plant areas such as fuel oil / lube oil, DG houses, H2 generating plants and hydrogen storage areas.

Flame proof rate of rise of temperature detector with fixed element and flame proof MCP

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Audible Output DevicesAn audible alarm signal lets people know

the alarm system has been activatedDevices may be mounted inside or outside

based on level of protection required May consist of:

SirensBells BuzzersHorns Voice Drivers

Output Devices

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Visual Output Devices

A visual signal lets users know the status of the alarm system if activated

Visual devices may be mounted inside or outside

May consist of...Strobe lightsLED’sOn / Off site printer

Output Devices

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Criteria to determine layout of the fire detectors

The design, construction and operational features of all types of

detectors shall be in accordance with relevant standards.

The number of fire detectors to be installed is governed by

total area to be protected

type of building construction

air movement & air velocity

ceiling obstructions

concentration of equipment in the area covered

sensitivity required

Area is divided into zones to be protected

The zones of individual detectors should overlap and no blind zone

should be left.

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Areas above false ceiling and below false flooring shall be

considered as separate zones.

Under ideal conditions of smooth ceiling and average room size, one

detector is recommended to protect the area.

Ionisation type detectors should be located where the largest

combustible gas concentration can be expected.

In the air conditioned areas both ionisation and optical type smoke

detectors are used.

Detectors must always installed at the highest point of the ceiling

and minimum coverage indicated by manufacture shall be

considered.

The number of detectors and their location should be so selected that

complete coverage is obtained

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Initial quantity estimation of smoke / heat detectors

35 to 40 sq.m per detector for general application. 20 to 25 sq.m per detector for main control room, electronic

cubicle room, computer room, etc., in view of high valve concentration

The exact requirement shall calculated based on relevant IS/NFPA standard

TYPES OF FIRE DETECTION SYSTEMTYPES OF FIRE DETECTION SYSTEM

A. Conventional FDA System

B. µ-P Based Addressable FDA System

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CONVENTIONAL FIRE DETECTION AND ALARM SYSTEMCONVENTIONAL FIRE DETECTION AND ALARM SYSTEM

Conventional fire sensors and manual call points shall provide for continuous

surveillance the area.

Main fire alarm panel shall derive signals from the zone indicating panels and

audible and visual annunciation shall be provided in the event of fire.

Repeater panel shall be located in security house / fire station to alert fire

fighting / security personnel.

Fire detectors shall be selected depending on the type of fire expected in a

particular area.

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All the fire alarm circuits shall be of modular design using electronic printed card circuits to facilitate easy replacement.

The system design shall be such that operation / resetting of alarms for one zone / detector will not block availability of alarm for any other zone.

the alarm / system resetting shall be by common push button and not by individual switches for different zones / detectors.

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Addressable Fire Detection & Alarm System

It is an automatic fire detection & alarm system consists of fire detectors & manual call points positioned in Zones/ loop through out a building(Area).

These are wired to control & indicating equipment which shows the location of alarm call, & actuates audible alarm sounders.

Industrial/ Non Industrial Buildings

Institutional Buildings

Residential Apartments

Hotel & Hospitals

All Industries

Mall & Multi Storied Complexes

Offices & Control Rooms

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Addressable µ-P based FDA system

Addressable I/P devices

Addressable O/P devices

Control panel

Constant power supply

Emergency Battery supply

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Microprocessor Based control Panel

Processor(CPU)

Adequate number of loop modules for detector loops

A coloured VDU monitor with keyboard

Output modules for alarm

Output control & interlocks

Communication modules for interfacing

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Continuous supervision of the detector connecting lines, individual

detector performance / operation and disconnection / removal of

detectors.

Discrimination between a real fire and false fire conditions by

incorporating signal verification and other features.

Individual detector addressing capability.

Detection of over / under sensitive detectors and automatic calibration by

increasing or decreasing their sensitivity levels based on environmental

conditions like air movement, fumes, humidity, etc.

Pre-alarm in case of any detector / detectors requiring maintenance.

Facility shall be provided for alteration programme according to needs.

BENEFITS OF µ-P BASED ADDRESSABLE FDA SYSTEM

CLEARANCE AND APPROVALSCLEARANCE AND APPROVALS

All detectors and sensors shall be approved by any of the

following bodies as applicable :

A. Under writers’ Laboratories (UL) – USA

B. Fire Officers Committee (FOC) – UK

C. Any other internationally recognised body acceptable to

Purchaser / Consultant. Approval certificates shall be

furnished with the bid.

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The Contractor shall be solely responsible for obtaining the required approval and clearance for the different components and systems of the fire detection and alarm system from the following authorities as applicable.

A. Tariff Advisory Committee (TAC) of the Insurance Association of India.

B. Dept. of Atomic Energy (DAE) Certification of safety from radioactivity.

C. Central Building Research Institute (CBRL), RoorkeeD. Central Mining Research Station (CMRS), Dhanbad.E. Local Fire Authority.

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SOME APPLICABLE STANDARDSSOME APPLICABLE STANDARDS

Code of practice for selection, installation & maintenance of

automatic fire alarm & detection system-IS-2189,BS-5839

PART1,ANSI-NFPA-72,FOC RULES

Code of practice for fire safety of buildings - IS-1646

Smoke detectors for use in automatic fire alarm system-IS-11360,

BS-5445 PART-7, ANSI-UL268

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