Heat detectors are very vital devices when it comes to fire detection and safety. Heat detectors are quite different from smoke detectors and both these have very different applications and uses. Since an outbreak of fire on a construction site can be quite fatal, it is very vital to understand how heat detectors work. You must ensure that heat detectors are installed properly, work efficiently and are tested regularly.
About Heat Detectors
As we know, heat detectors are activated when there is a fire and do not respond to smoke. Heat detectors are basically of two kinds: Rate-of-rise (ROR) heat detectors and fixed temperature heat detectors. Heat detectors are used in areas where smoke alarms are not suitable. Heat detectors are quite hardy and can withstand very harsh environmental conditions. They are very useful in areas where there are high levels of fumes and dust.
Heat detectors must not be installed in areas that have very high humidity levels as the humidity may prevent the heat from entering the heat detector unit and may cause the alarm to fail and not get activated. Also, installing heat detectors in areas where temperatures may rise above 100°F, fall below -10 °F or near fluorescent lights, may affect its operations.
Rate-of-rise or (ROR) Heat Detectors
ROR heat detectors work on the rapid increase in the element temperature of around 12°F – 15°F per minute. This rise in temperature does not depend on the initial temperature. ROR heat detectors work on the principle of thermistors or thermocouples. The ROR detector has two thermocouples that are sensitive to heat. One of the thermocouples monitors heat that is transferred by radiation or convection. The other thermistor responds to the ambient temperature. The heat detector is activated when the temperature of the first thermocouple increases relative to the second one.
ROR heat detectors may not respond to slowly developing fires. In order to detect slowly developing fires, usually a fixed temperature element is added to the ROR detector which will be activated when the element reaches the pre-set threshold temperature.
Fixed Temperature Heat Detectors
These types of heat detectors are the most commonly used. Fixed temperature heat detectors work when the element that is sensitive to heat reaches the point where a solid changes to liquid. The heat is accumulated at the sensitive element due to a thermal lag. This causes the temperature of the device to reach its operating temperature a while after the surrounding air temperature exceeds the device temperature. When this happens, the detector is activated and an alarm is sounded.
Selection of a Heat Detector
Heat detectors are not life safety devices. However, they are very useful in detecting and notifying when a fire occurs in places where smoke detectors cannot be installed. Use of heat detectors help to gain extra time to put out the fire or evacuate the workplace in case of a fire.
Each kind of heat detector has its advantages over the other and each has its own set of uses and benefits. The choice of the heat detector depends on the premises where it is being used and the layout of the worksite.
When it comes to heat detection equipment and fire protection, Cygnus’s top quality heat detectors offer superior protection of your worksites, workforce as well as your assets against the ravages of fire.