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Detection
The armored vehicle's volume is packed with munitions and propellants, hydraulic fluids, fuel and lubricants that if ignited will result in a slow or rapid growing fireball that can evolve in an explosion. The explosion/fire scenarios of the vehicles various compartments are different (based on the combustible materials in each compartment) and as a result, so are the detection means.
Once the ignition occurs and the fireball develops - its energy is dissipated in the form of pressure waves (masses of gases and particles propagating at high velocities), heat energy (either from the hot particles or from chemical reactions between the gases and combustion products) and optical radiation (emitted by chemical reactions in the gas phase and vibration/rotation of the gas molecules in the propagating fireball). Various fuels and different fire scenarios determine the detector selection, either fast response Optical Flame Detectors or in areas where direct line of sight is difficult the use of Spot or Linear Heat Detectors.
Fast-response Optical Flame Detectors detect the ultraviolet and infrared emission radiation of the explosion/fire event. These patented UV/IR detectors comprise optical sensors with special narrow band filters and perform a unique spectral analysis of the radiation signals.
Each sensor's band pass filter has been carefully selected to ensure the greatest degree of spectral matching to the radiant energy emissions of fire, and the lowest degree of matching to non-fire stimuli. The signals from both sensors in the UV/IR detector are analyzed for frequency, intensity and duration. Simultaneous matching of radiant energy in both the UV and IR sensors triggers an alarm signal.
Heat detectors that are normally slower in response to fire (heat transfer takes longer time than light) are used in constricted areas where optical detectors cone of vision is obstructed. Spot heat detectors are selected for local heat sensing in remote points and Linear heat detectors are selected for area heat sensing over a predetermined distance, for example in the engine compartment of armored vehicles.
The heat detector employs two independent methods of detection: rate-of-rise and fixed temperature. The rate-of-rise method detects fires that rapidly grow in intensity. This method responds to abnormally fast temperature increases. The fixed-temperature method detects fires that build temperatures to a high level at a slow rate. This method responds to a specific temperature setting.
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