Interview Questions on Smoke detection system

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1.What are the types of ‘smoke detectors’ in use in P.D.O.?

Two types of smoke detectors are used in PDO. They are:

1. Optical type, 2. Radioactive type, 3. Ionisation type.

2.Explain the operating principle of the different types of smoke detectors.

Optical type: when the smoke cuts the optical detection path, and unbalance in the detector current loop raises a smoke alarm. These type detectors are sensitive to larger particles of combustion 0.5 to 10 microns. It is suitable for applications where thermal turbulence can be expected.

Interview Questions on Smoke detection system

Radio active type: when the smoke is detected by the radio active substance, the unbalance in the detector current loop raises a smoke alarm. This type of detectors are sensitive to air movement greater than 5m/sec. It is normally installed with the photoelectric (optical type) type smoke detectors.

3.Why is a smoke detector as important as a ‘heat switch’ and ‘UV detector’?

Smoke detectors are used in confined areas such as control rooms and electrical switch rooms.

4.Where are smoke detectors generally installed in P.D.O.?

Smoke detectors are used in confined areas such as control rooms and electrical switch rooms.

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5.What happens when a smoke detector detects smoke?

When a smoke detector detects smoke, the detector loop current changes. The unbalance in the loop current is detected as smoke.

Once in every 10 secs the L.E.D on each smoke detector blinks as self loop check. On detection of smoke, this L.E.D remains continuous on (bright).

6.name the manufacturers of smoke detection systems.

Name of the smoke detector manufactures are Firecheta, Cloride Gent…etc.

7.why are periodic checks and maintenance required on smoke detection system?

Particularly on the optical type smoke detectors, the collection of dust in the sensor path may result in a false alarm. Also the periodic maintenance ensures the reliability of the detection system.

8.What are the common problems faced when maintaining a smoke detection system?

False alarm due to accumulation of dust, floor cleaning, water vapour

Loose connection results in the fluctuation of the detector loop current.

Improper base plug-in connection.

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