Flame detector

A flame detector is a detector that uses optical sensors to detect flames.

Types

Ultraviolet

Ultraviolet (UV) detectors work with wavelengths shorter than 300 nm. These detectors detect fires and explosions within 3–4 milliseconds due to the UV radiation emitted at the instant of their ignition. False alarms can be triggered by UV sources such as lightning, arc welding, radiation, and sunlight. In order to reduce false alarm a time delay of 2-3 seconds is often included in the UV Flame detector design.

Infrared

Infrared (IR) flame detectors work within the infrared spectral band. Hot gases emit a specific spectral pattern in the infrared region, which can be sensed with a thermal imaging camera (TIC) a type of thermographic camera. False alarms can be caused by other hot surfaces in the area. A typical frequency where single frequency IR flame detector is sensitive is in the 4.4 micrometre range. Typical response time is 3-5 seconds.

UV/IR

UV and IR flame detectors compare the threshold signal in two ranges in "AND" configuration and their ratio to each other to confirm the fire signal and minimize false alarms.

IR/IR flame detection

Dual IR (IR/IR) flame detectors compare the threshold signal in two infrared ranges. In this case one sensor looks at the 4.4 micrometre range and the other sensor at a reference frequency.

IR/IR/IR flame detection

Triple IR flame detectors compare three specific wavelength bands within the IR spectral region and their ratio to each other to reliably detect flames and minimize false alarms. In this case one sensor looks at the 4.4 micrometre range and the other sensors at a reference frequencies.

Visible sensors

In some detectors a sensor for visible radiation is added to the design in order to be able to discriminate against false alarms better or improve the detection range. Example: UV/IR/vis, IR/IR/vis, IR/IR/IR/vis flame detectors.

Video

Closed-circuit television or a web camera can be used for video detection ( wavelength between 0.4 and 0.7 µm). Like humans, the camera can be blinded by smoke or fog.

IR Array

IR array flame detectors, also known as visual flame detectors employ flame recognition technology to confirm fire by analyzing near IR radiation via the pixel array of a charge-coupled device (CCD). IR array addresses the problems of single, dual and triple 4.4µm IR flame detectors susceptibility to spurious trips, de-sensitization and blinding caused by environmental or industrial phenomena.

Applications

UV/IR flame detectors are used on hydrogen stations.

On Air

Today