Flame Detectors: Principles and Applications

Introduction:

Flame detectors play a crucial role in fire detection systems, offering rapid response and sensitivity to specific characteristics of combustion. This document explores the different types of flame detectors, their operating principles, and their applications in various settings.

Types of Flame Detectors:

1. Infrared (IR) Detectors: Sensitive to radiant energy below the visible spectrum (above 7700 Angstroms). Respond quickly to hydrocarbon fires through photovoltaic or photo resistive cells. Ideal for protection in environments requiring fast detection and extinguishing (e.g.,?rocket fuel facilities). Detect reflected infrared waves,?making them suitable for spark/ember detection applications (e.g.,?conveyors). Not effective for fires involving metals,?ammonia,?hydrogen,?or sulfur due to low radiation within their sensitivity range.
2. Ultraviolet (UV) Detectors: Respond to radiant energy above the visible spectrum (below 4000 Angstroms). Detect direct line-of-sight ultraviolet waves only. Sensitive to most fire types,?including hydrocarbon,?metals,?ammonia,?and hydrogen. Activated by sources like arc welding,?X-rays,?and lightning,?requiring careful placement. Utilize solid-state devices or gas-filled tubes for sensing. "Solar-blind" due to Earth's atmosphere filtering solar radiation in their sensitivity range (1850-2450 Angstroms). Prone to attenuation by UV-absorbing gases and vapors or oil films on the detector window.
3. Photoelectric Flame Detectors: Utilize photocells that change electrical properties upon exposure to radiant energy. May not differentiate between fire and other light sources unless equipped with flame flicker detection (4-30 Hz).

Applications:

• Surveillance of vulnerable areas (conveyor belts,?storage sites,?chemical plants).
• Leak detection of ignitable liquids in hydrocarbon and chemical facilities.
• Integration with smoke detectors in cross-zone fire protection systems.
• Automatic activation of fire suppression systems (e.g.,?monitor nozzles for large-scale liquid storage).
• Aircraft hangar protection against fuel spill fires (using IR or UV detectors).

Conclusion:

Flame detectors offer valuable tools for early fire detection in diverse applications. Understanding their principles and limitations is crucial for selecting the appropriate technology for each specific hazard and environment.

I hope this is helpful!