Detecting Systems

8/4/2019 Detecting Systems

1/18

FIRE SYSTEMSTYPE OF DETECTORS


2/18

CONVENTIONAL DETECTORS-

Smoke detectors

Heat detectors

Light obscuring detectors

Infrared detectors

UV detectors


3/18

SMOKEDETECTORS


4/18

TWO TYPES-

Ionisation smokedetector-

Light scatteringsmoke detector-


5/18

HEATDETECTORS

-Heat detectors are used

where smoking ispermitted.

-Response time is longer

than smoke detectors.


6/18

TWO TYPES-

Fusible type- Bi-metallic coil type-


7/18

LIGHTOBSCURING


8/18

WORKING-

A beam of light is projected across the protected area close to the ceiling. The light fallsonto a photo-electric cell. Smoke rising from a fire passes through the light beam toobscure and interrupt the amount of light falling on the photo-electric cell. The flow ofelectric current from the cell reduces sufficiently to activate an alarm relay.


9/18

INFRAREDDETECTORSFire also releases radiant energyin the form of visible light, infra-red and ultra-violet radiation.

Radiant energy travels in wavesfrom the fire.


10/18

WORKING-

Flames have a distinctive flicker, normally in the range of 4 to 15Hz. The filter is used to exclude signals outside of this range.


11/18

UVDETECTORS


12/18

WORKING-

reacts with ultra-violet radiation. When the bulb receives radiant thesedetectors have a gas-filled bulb which energy, the gas is ionised toproduce an electric current. When this current exceeds the set point ofthe amplifier the alarm circuit closes to operate the alarm system.


13/18

PLACING

THEDETECTORS


14/18

PLACING AREAS- Should be installed in all areas of the

protected premises.

should include all rooms, halls, storage areas,basements

attics, lofts, and spaces above suspendedceilings including plenum areas utilized aspart of the HVAC system.

All closets, elevator shafts, enclosed stairways,dumbwaiter shafts, chutes, and othersubdivisions and all accessible spaces.


15/18

when only one detector is required in a room or space, the detectorshould be placed as close to the center of the ceiling as possible.

If a center location is not possible, the detector may be placed nocloser than 4 inches from the wall.

Wall-mounted detectors should be located not less than 4 inches normore than 12 inches from the ceiling to the top of the detector, and atleast 4 inches from any corner wall junction.

Should not be placed in path of ducts and should maintain a distanceof atleat 3 feet because it can cause accumulation of dust.


16/18

DETECTOR SPACING-


17/18

WHERE NOT TO PLACEDETECTORS-

Excessively Dusty or Dirty Areas

Outdoors

Wet or Excessively Humid Areas

Elevator Lobbies

Extreme Temperatures

Areas with Combustion Particles

Manufacturing Areas

Fluorescent Light Fixtures


18/18

Submitted by-

PRIYA AGARWALSAURABH AGARWAL

Detecting Systems

Documents

Transcript of Detecting Systems