Numerous industries such as those involved in manufacturing, processing, storing or transportation of flammable materials, and commercial centers rely on a flame monitoring system for safety. At the core of the system is a crucial component - the flame detector. The flame detector is basically an optical sensor which detects the heat and communicates to a control board.
The optical sensor is designed to be sensitive to radiation emitted at diverse wavelengths in different spectral bands. One key advantage of the optical flame detector is its remote detection ability of even a small size fire from a long distance.
Types of Flame Detectors
There are many different types of flame detectors available in the market today. Some of the key types are briefly described below:
- Ultraviolet (UV) detectors – They have the ability to detect fires and explosions in about 3-4 ms. The UV detector can accurately distinguish the type of flame the moment it spots a small flame. The downside is that these detectors detect even sunlight, radiation, arc welding and lightning, and short wave UV cannot penetrate dust, smoke, fuel particles and oil films.
- Infrared flame detectors – These sensors operate by using an infrared band. A small thermal imaging camera in these detectors can instantly detect the presence of hot gasses released anywhere near the infrared detector. In certain cases, other sources of hot gas that occur near the infrared flame detector can cause it to set off a false alarm. Infrared waves can penetrate dust, smoke, fuel particles and oil films.
- UV/IR detectors - A combination of both UV and infrared technology is quite popular for detection of heat as the detector is able to collect information from both an UV perspective and an infrared perspective. This helps to minimize false alarms.
- IR/IR flame detectors – These detect flames within two infrared frequencies.
- Closed circuit video cameras – They can detect any flame or fire. However, the chances for false alarm are very high as the cameras can be triggered by any kind of smoke or fog. This type of detectors is not very reliable.
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Working Principle
Sophisticated flame sensing technologies are designed to detect common industrial fuels such as alcohols, kerosene, diesel, gasoline, hydrogen, ethylene, LNG/LPG, paper/wood, textiles, solvents, sulfur, and jet fuels.
They are also built to distinguish between actual flames and radiation from sunlight, lightning, hot objects, arc welding, and other non-flame sources. False alarms cause productivity loss and increase in costs.
Flame detectors comprise an electronic circuit with an electromagnetic radiation receiver. They are activated when they receive electromagnetic radiation from one or more defined wave lengths according to their design in the UV or infrared spectrum. Advanced flame detector models offer fields of view of about 90° to 120°.
The IR detector can detect low-frequency flickering IR radiation ranging from 1 to 15 Hz during combustion. It uses the IR flame flicker techniques, which enables the sensor to operate through a layer of oil, water vapor, dust, or ice. Most IR flame sensors are designed to respond to 4.3µm light emitted by hydrocarbon flames.
Applications
The following are the key applications of flame detectors:
- Fume cupboards, MDF factories, felt manufacture
- Atria, coal handling, waste handling
- Nuclear industry, pharmaceuticals, metal fabrication
- Agriculture, power flands and power plants
- Printing, spray booths, tunnels
- Aircraft hangars, clothing dryers and high voltage equipment
- Gas fuelled cookers and domestic heating systems
- Industrial heating and drying systems, and furnaces
- Industrial gas turbines and oil refineries
- Engine test facilities and engine rooms
- Generators and storage tanks.
Sources and Further Reading
This information has been sourced, reviewed and adapted from materials provided by Teledyne Gas and Flame Detection.
For more information on this source, please visit Teledyne Gas and Flame Detection.