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Ultra-High-Speed Optical Flame Detection and Releasing System Solutions Page 2 TECHNICAL PAPER HIGH-SPEED DETECTION AND RELEASING Ultra-high-speed optical flame detection SYSTEM and releasing system solutions By Michael J. Hosch, Senior Applications Engineer, Det-Tronics This paper will discuss solutions for the application of A review of optical flame detection ultra-high-speed optical flame detection and releasing Radiant energy-sensing flame detectors systems within munitions manufacturing plants and other 2.0 detect fire by sensing and analyzing the electromagnetic facilities requiring high-speed deluge fire suppression. It radiation that is emitted from fire. Different types of fires will also review optical flame detection technology and emit differing spectra of light energy that allow for their recent developments in a system that assists users in detection. The region of spectral emission to which a obtaining compliance with industry codes and standards. detector is sensitive is ideally tightly controlled to minimize the effects of the spectral emission from sunlight, ambient Introduction light, machinery and processing equipment. Figure 1 below 1.0 To meet overall system response time gives a broad view of the electromagnetic spectrum and requirements of ultra-high-speed industry codes and depicts the infrared (IR) and ultraviolet (UV) regions that are standards, the flame detection and releasing system favorable for the detection of flame. must be capable of detecting an event and providing A brief description of each technology that is suitable for a signal to the deluge system, which must respond in ultra-high-speed flame detection (UV, IR and UVIR) follows. 100 milliseconds (ms) or less from the presentation of the energy source at the detector to flow of water from the water spray nozzle. To be The Electromagnetic Spectrum considered high-speed, the system must operate in 500ms or less (reference National Fire Protection Association, NFPA 15). In applications that require these systems, a fire develops much Opacity too rapidly for the use of heat and Atmospheric smoke detectors, which may take many seconds to detect the fire. To understand the techniques used in applying ultra-high-speed optical flame detection in munition processing plants, a brief review of the basic operating principles of flame detection technology is Figure 1: Depiction of the electromagnetic spectrum and wavelengths of interest to ultra-high- warranted. speed optical flame detectors det-tronics.com +1 800.765.3473 Technical Paper | Ultra-high-speed optical flame detection and releasing system solutions Page 2 Figure 2: Relationship between ultraviolet sensors and solar radiation Optical flame detection technologies FIGURE 2 2.1 2.1.1 Ultraviolet (UV) UVUV flame flame detectors detectors utilize (Figure a sensor that3) can is comprised detect nearlyof UV every flame type detectors of fire (Figure and 3)are can capable detect nearly of responseevery type Geiger-Muellertimes under type 15mS vacuum in ideal tube. Thisconditions. sensor is typicallyBecause UVof fire sensors and are cancapable be ofmade response solar times-blind under and 15ms are in not designed to be responsive to an extremely narrow band ideal conditions. Because UVFIGURE sensors 2 can be made solar- ofaffected light energy by ofheat 1850-2450 radiation, Angstroms they (Å),can with be specialsuccessfully blind applied and are not in affected many applications.by heat radiation, they can be models available that extend to 2650Å. As shown in UV successfullyflame detectors (Figure applied 3) can in detect many nearly applications. every type of fire and are capable of response times under 15mS in ideal conditions. Because UV sensors can be made solar-blind and are not Figure 2, the UV sensitivity range is outside of the range affected by heat radiation, they can be successfully applied in many applications. of human visibility and is not influenced by sunlight. As UV radiation emitted from the fire comes in contact with the UV UV sensor, voltage pulses are generated with their frequency Sensor Sensor proportional to the intensity of the UV radiation. These pulses are signal-processed by a microprocessor where they are compared against programmed parameters. If the amount of processed voltage pulses exceeds a predetermined threshold, an alarm is activated. FIGURE 3: Det-Tronics X2200 UV technology optical flame detector Figure 3: Det-Tronics X2200 UV technology optical flame detector Page 4 of 22 det-tronics.com +1 800.765.3473 FIGURE 3: Det-Tronics X2200 UV technology optical@ 2018 Detector flame Electronics Corporation detector Page 4 of 22 @ 2018 Detector Electronics Corporation Technical Paper | Ultra-high-speed optical flame detection and releasing system solutions Page 3 ULTRAVIOLET SENSOR OPERATING PRINCIPLES Ultraviolet Sensor Operating Principles: Ultraviolet Sensor Operating Principles: Utilizes solar• Utilizes-blind solar-blind wavelengths wavelengths of of 1850Å 1850Å to to 2650Å 2650Å UVUtilizes photons •solar UV strike photons-blind tube strikewavelengths cathode tube cathode of 1850Å to 2650Å CathodeUV photons releases strike electron tube cathode • Cathode releases electron Optical Integrity ElectronCathode strikes releases gas electron molecule Test Source CascadeElectron effect• strikes Electron occurs gasstrikes molecule to gas anode molecule DischargeCascade• effect is Cascade quenched occurs effect occursandto anode a to pulse anode is created PulseDischarge output is is quenched measured and in caounts pulse piser created second (CPS) • Discharge is quenched and a pulse is created DesignedPulse output and ismanufactured measured in bycounts Det -pTronicser second since (CPS) 1973 Designed• Pulseand manufacturedoutput is measured by in countsDet-Tronics per second since (CPS) 1973 • Designed and manufactured by Det-Tronics since 1973 As with anyAs detector with any detectortechnology, technology, there there are are advantages advantages and disadvantages. UV flame detectors As with any detector technology, there are advantages and disadvantages. UV flame detectors are sensitiveand to disadvantages. lightning, welding UV flame and detectors x-rays. are Partialsensitive physicalto obstruction of the fire or the are sensitivelightning, to lightning, welding and welding x-rays. Partialand x physical-rays. Partialobstruction physical obstruction of the fire or the presence of smoke and/or UV-absorbing vapors may delay or possibly even prevent detection. presence ofof smokethe fire and/oror the presence UV-absorbing of smoke and/orvapors UV-absorbing may delay or possibly even prevent detection. See Figure 4 below. See Figurevapors 4 below may. delay or possibly even prevent detection. See Figure 4 below. Figure 4: Potential benefits and limitations of UV flame detection technology Less affected by elements Speed of response Potential limitations of a UV detector UV detector Welding / lightning / X-rays / Vapors & oil film nuclear radiation Detects most fire types Unaffected by hot objects Potential benefits of a UV detector UV detector Partially obstructed fires Smoke det-tronics.com FIGURE 4: Potential benefits and limitations of UV flame detection+1 technology800.765.3473 Page 6 of 22 @ 2018 Detector Electronics Corporation FIGURE 4: Potential benefits and limitations of UV flame detection technology Page 5 of 22 Page 5 of 22 Page 6 of 22 @ 2018 Detector Electronics Corporation@ 2018 Detector Electronics Corporation @ 2018 Detector Electronics Corporation 2.1.2 INFRARED (IR) IR flame detectors utilize a sensor that is typically comprised of a pyroelectric detector. An optical interference filter is utilized within the pyroelectric detector to establish a bandpass region that is favorable for the exclusive detection of fire. These filters are selected depending upon the desired wavelength of interest, typically 4.2 – 4.8 micrometers (µm) within the CO2 emission band. As shown in Figure 5, the IR sensitivity range is outside of the range of human visibilityTechnical Paperand |not Ultra-high-speed influenced optical by sunlight. flame detection and releasing system solutions Page 4 Figure 5: Relationship between infrared sensors and solar radiation 2.1.2 Infrared (IR) If the emitted electromagnetic energy includes FIGUREwavelengths 5 that will pass through the bandpass IR flame detectors utilize a sensor that is typically interference filter, the light will encounter a single- comprised of a pyroelectric detector. An optical crystalline element. The element generates a small interference filter is utilized within the pyroelectric signal that is proportional in magnitude and frequency detector to establish a bandpass region that is favorable to the electromagnetic radiation that is being emitted for the exclusive detection of fire. These filters are from the fire. This signal is further signal-processed by a selected depending upon the desired wavelength of IR flame detectorsmicroprocessor (Figure 6) where can detect the firesresulting that are signal preceded is compared by smoke or contain vapors more interest, typically 4.2 – 4.8 micrometers (μm) within readily thanagainst detectors predetermined that utilize UV thresholds, technology. andResponse if the times signal can be less than 15mS in ideal the CO2 emission band. As shown in Figure 5, the IR conditions.qualifies, Because IRa sensorsfire alarm can beis madeactivated. solar-resistant and are not affected by UV radiation, sensitivity range is outside of the range of human visibilitythey can be successfully applied in many applications that challenge UV detectors.
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