Field Instrumentation

What is a flame detector and how does it work

A flame detector is a type of sensor that can detect and respond to the flame presence. This device is capable to determine smokeless liquid and smoke that can create open fire. In boiler furnaces flame detectors are widely used, mostly a flame detector can detect heat, smoke, and fire. This device also does fire detection according to the air temperature and air movement. The flame detectors are usually optical devices so they can respond to flame in less than a second. The flame detector would respond to the flame according to the installation, it would sound an alarm and also deactivate the fuel line or it would activate a fire suppression system.

What are the components of a flame monitoring system? How does a flame detector work

The major component of a flame detector system is a flame detector and it consists of photoelectric detective circuits, signal conditioning circuits, microprocessor systems, I/O circuits, and wind cooling systems.

The sensors in the flame detector will sense the radiation that is sent by the flame, the sensor of the flame detector would be a photoelectric sensor and this sensor would convert the radiant intensity signal of the flame to a relevant voltage signal and this signal would be converted after that it would be processed in a single chip microcomputer and is converted as output.

How many types of flame detectors are there and how do they work


This type of flame detector works by detecting the UV radiation at the instant of ignition. Mostly all fires emit UV radiations, so in case of the flame, the sensor would detect it and creates a series of the pulse which is converted by detector electronics into an alarm output. According to the detection range, a false alarm could also happen.

What are the advantages of UV detector

  • High-speed response
  • It would respond to hydrocarbon, hydrogen, and metal fires

What are the disadvantages of UV detectors

  • It would respond to welding at long range
  • It could also respond to lightning, sparks, etc.


The infra-red flame detector works by checking the infrared spectral band for specific patterns that are released by hot gases, this device would need the flickering motion of the flame. The IR radiation is not only emitted by flames, it could also be radiated from ovens, lamps, etc. So there is a chance for the false alarm


This type of detector is capable to detect both the UV and IR radiations, so it has both the UV and IR sensor. The two sensors individually operate the same as described above, but additional circuitry processes signals from both sensors. So the combined detector has better false alarm rejection capability than the individual UV or IR detector.

What are the advantages of UV/IR flame detector?

  • High-speed response
  • Immune to the false alarm

What are the disadvantages of UV/IR flame detector

  • It cannot be used for non-carbon fires
  • This device will only detect fires that emits both the UV/IR radiation

How to select a flame detector

  • It must be selected according to the nature of fire there are many types of flame detectors available so select one of them
  • According to the protected area
  • Environmental conditions
  • It must be selected according to the detector capability
  • It must be selected according to the dimensions of the protected area
  • It must be selected according to the radiation characteristics of the flame
  • It must be selected according to detectors response time
  • Rejection of false alarm

How to install a flame detector

  • It must be installed according to the viewing angle of the detector
  • Detection range
  • We must also consider obstructions such as beams, girders, etc.
  • High-risk fire ignition areas
  • We must also consider the mounting height too.

What do we connect a flame detector to?

The detector can be connected to a fire alarm panel and it can be a part of the site detection system. Warning device and suppression system can be operated and the power supply to the detector can be monitored too. The detector can be connected to a flame detector control panel and this is only done if the site does not have a fire alarm panel. A flame detector can also be connected to a site monitoring system.

What are the applications of flame detector

  • Industrial warehouses
  • Chemical production plants
  • Chemical stores
  • Petrol storage and pump stations
  • Arc welding workshops
  • Power plants
  • Transformer stations
  • Underground tunnels
  • Motor testbeds
  • Wood stores


post-graduate in Electronics & communication.

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