الفصل 10
كشف اللهب
منشور
- How flame detectors work: UV, IR, UV/IR and multi-spectrum IR
Flame detectors look for the radiation a fire emits: solar-blind ultraviolet, the hot CO2 band near 4.4 µm, and the 1 to 20 Hz flicker of flames. How UV, IR, UV/IR and multi-spectrum IR detectors work, what they miss and how to choose.
- Flame detector placement and cone of vision
A flame detector only sees fires inside its cone of vision, large enough for the distance and in direct line of sight. How field of view, the inverse square law, obstructions, coverage mapping and mounting decide where flame detectors go.
- False alarms in flame detectors: common sources and how to avoid them
Sunlight and its reflections, welding arcs, hot and moving machinery, flares, lightning and ionising radiation cause most flame detector false alarms. Why each source fools UV or IR detectors and how technology, aiming, settings and work permits prevent them.
- Detecting hydrogen fires and other invisible flames
Hydrogen burns with a nearly invisible, smokeless flame that emits UV and hot water vapour bands but no CO2, so standard IR flame detectors miss it. How UV, water-band IR and thermal cameras detect hydrogen and methanol fires, and what to watch out for.
- Flame detector performance standards: EN 54-10, FM 3260 and response time
EN 54-10 sorts flame detectors into Class 1, 2 or 3 by the distance at which they detect two reference fires within 30 s; FM 3260 verifies the distance, field of view and response time the maker declares. How to read the numbers on a datasheet.
- Video and thermal imaging for flame and smoke detection
Video fire detection analyses camera images for the colour, motion and flicker of flames or the spread of smoke; thermal imaging measures surface temperature to find hot spots before they burn. How both work, where they fit, their limits and the standards that test them.