Heat detector is a type of detector that has two types of metal elements that can detect (consisting of two thick strips and a thin strip). Thin strips are more sensitive to temperature rises than thick trips. If there is a sudden rise in temperature, then the thin strip responds faster than the thick strip, the two strips can come into contact with each other. During the normal temperature rise the two strips will experience the same deflection and thus do not show any touch and reaction. Usually if the rate of increase is less than 10oC in half an hour, the detector will not give an alarm. But if the level rises to 75oC or more, the two strips will touch because of deflection, triggering an alarm.
This heat detector operates by detecting an increase in temperature starting from the initial temperature, which is 12 ° to 15 ° F (6.7 ° to 8.3 ° C) and continues to increase per minute. This heat detector consists of two heat-sensitive thermocouples or thermistors. A thermocouple is used to monitor heat transferred through convection or radiation. Other thermocouples respond to ambient temperature. The heat detector will respond each time the temperature of the first thermocouple rises relative to other thermocouples. Rate-of-Rise Heat Detectors cannot respond to low energy release. The combination of this heat detector is to add a fixed temperature element that can be used to detect fire slowly.
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Read more : Principle of heat detectors for ship; Types of fire extinguishers for ship; Causes of fire on the ship; Flame detectors on ships; Fire prevention considerations on board; Air Ducting for Marine