FIRE DETECTION & ALARM SYSTEMS-1.Why are fire detection & alarm systems required?

Why are fire detection & 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 system
Input
Devices
Output
Devices
Control
Panel

Input Devices
 Fire Box (Manual Pull Station)
 When shorted trips an alarm (usually fire)
 Installed in the normal exit path
 Types of Fire Box
 Single Action
 Pull handle once
 Glass Break
 Glass rod or plate is broken
 Double Action
 Lifting of a cover or opening a door

3.1) Heat detectors
1. fixed temp type heat detector
2. rate-of-rise type heat detector
3.2) Smoke detectors
1. Photoelectric
2. Ionization
3.3) Flame detectors
1. Ultraviolet light (UV)
2. Infrared (IR)
3.4) Fire-gas detectors
FIRE DETECTORS
Input Devices
Heat Detectors
Smoke Detector

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 detectors
 Operate on principle that temperature in a room will
increase faster from fire than from atmospheric temperature
 Will initiate an alarm when 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

Photoelectric smoke detector
 Uses a photocell coupled with a specific light source.
 Basically smoke entering the smoke detector chamber
disrupts the light beam causing alarm signal to be initiated
 More sensitive to smoldering fires
1: optical chamber
2: cover
3: case moulding
4: Photodiode (detector)
5: infrared LED

Ionization smoke detector
 Invisible 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 detectors
• Monitors levels of CO2 and CO(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 & ignores gases produced
by friendly fires
• Not many in use – very specialized applications

Combination detectors
 Single device can be designed to have more than one
function eg. heat/smoke, smoke/CO detectors
 Different combination make the detectors more versatile
and more responsive to fire conditions

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

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

Audible Output Devices
 An audible alarm signal lets people know the alarm system
has been activated
 Devices may be mounted inside or outside based on level
of protection required
 May consist of:
 Sirens
 Bells
 Buzzers
 Horns
 Voice Drivers
Output Devices

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 lights
 LED’s
 On / Off site printer
Output Devices

Criteria to determine layout of fire detectors
 Design, construction & 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
o total area to be protected
o type of building construction
o air movement & air velocity
o ceiling obstructions
o concentration of equipment in the area covered
o sensitivity required
 Area is divided into zones to be protected
 The zones of individual detectors should overlap and no
blind zone should be left.

 Areas above false ceiling & below false flooring shall be
considered as separate zones.
 Under ideal conditions of smooth ceiling & average room
size, one detector recommended to protect the area.
 Ionisation type detectors should be located where largest
combustible gas concentration can be expected.
 In air conditioned areas both ionisation & optical type
smoke detectors are used.
 Detectors must always be installed at highest point of
ceiling & minimum coverage indicated by manufacture
shall be considered.
 The number of detectors & their location should be so
selected that complete coverage is obtained

Initial quantity estimation - 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
SYSTEM
1. Conventional FDA System
2. µ-P Based Addressable FDA System

CONVENTIONAL 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.

• All 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.

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

Addressable µ-P based FDA system
• Addressable I/P devices
• Addressable O/P devices
• Control panel
• Constant power supply
• Emergency Battery supply

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

 Continuous supervision of detector connecting lines, individual
detector performance/operation & disconnection/removal of
detectors.
 Discrimination between real fire & false fire conditions by
incorporating signal verification and other features.
 Individual detector addressing capability.
 Detection of over/under sensitive detectors & automatic
calibration by increasing/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 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.

The Contractor shall be solely responsible for
obtaining required approval & clearance for different
components & systems of the fire detection & alarm
system from the following authorities as applicable.
1. Tariff Advisory Committee (TAC) of the Insurance
Association of India.
2. Dept. of Atomic Energy (DAE) Certification of safety from
radioactivity.
3. Central Building Research Institute (CBRI), Roorkee
4. Central Mining Research Station (CMRS), Dhanbad.
5. Local Fire Authority.

SOME 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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