NEMA SB 23-2016 Guide for Application of Flame Detection.pdf

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1、NEMA Standards PublicationNational Electrical Manufacturers AssociationNEMA SB 23-2016Guide for Application of Flame DetectionNEMA Standards Publication SB 23-2016 Guide for Application of Flame Detection Published by: National Electrical Manufacturers Association 1300 North 17thStreet, Suite 900 Ro

2、sslyn, Virginia 22209 www.nema.org 2016 National Electrical Manufacturers Association. All rights, including translation into other languages, reserved under the Universal Copyright Convention, the Berne Convention for the Protection of Literary and Artistic Works, and the International and Pan Amer

3、ican copyright conventions. 2016 National Electrical Manufacturers Association NOTICE AND DISCLAIMER The information in this publication was considered technically sound by a consensus among persons engaged in its development at the time it was approved. Consensus does not necessarily mean there was

4、 unanimous agreement among every person participating in the development process. The National Electrical Manufacturers Association (NEMA) standards and guideline publications, of which the document herein is one, are developed through a voluntary standards development process. This process brings t

5、ogether volunteers and/or seeks out the views of persons who have an interest in the topic covered by this publication. Although NEMA administers the process and establishes rules to promote fairness in the development of consensus, it does not write the documents, nor does it independently test, ev

6、aluate, or verify the accuracy or completeness of any information or the soundness of any judgments contained in its standards and guideline publications. NEMA disclaims liability for any personal injury, property, or other damages of any nature, whether special, indirect, consequential, or compensa

7、tory, directly or indirectly resulting from the publication, use of, application, or reliance on this document. NEMA disclaims and makes no guaranty or warranty, express or implied, as to the accuracy or completeness of any information published herein, and disclaims and makes no warranty that the i

8、nformation in this document will fulfill any particular purpose(s) or need(s). NEMA does not undertake to guarantee the performance of any individual manufacturers or sellers products or services by virtue of this standard or guide. In publishing and making this document available, NEMA is not under

9、taking to render professional or other services for or on behalf of any person or entity, nor is NEMA undertaking to perform any duty owed by any person or entity to someone else. Anyone using this document should rely on his or her own independent judgment or, as appropriate, seek the advice of a c

10、ompetent professional in determining the exercise of reasonable care in any given circumstance. Information and other standards on the topic covered by this publication may be available from other sources, which the user may wish to consult for additional views or information not covered by this pub

11、lication. NEMA has no power, nor does it undertake to police or enforce compliance with the contents of this document. NEMA does not certify, test, or inspect products, designs, or installations for safety or health purposes. Any certification or other statement of compliance with any health- or saf

12、ety-related information in this document shall not be attributable to NEMA and is solely the responsibility of the certifier or maker of the statement. NEMA SB 23-2016 Page i 2016 National Electrical Manufacturers Association Foreword This application guide was developed by NEMAs Fire, Life Safety,

13、Security, and Emergency Communications Group (NEMA 3SB). Content is obtained by industry subject matter experts and leading manufacturers of flame-detection systems and devices. About NEMA 3SB The objective of NEMA 3SB is to serve as the primary source of technical, training, and educational materia

14、ls essential for the specification, application, and manufacture of reliable life safety products, as well as their installation, performance, and inspection. NEMA 3SB currently represents 21 manufacturers in support of the automatic fire detection and alarm industry and the health care communicatio

15、ns industry. Fire-detection and alarm products include life safety/fire alarm systems and devices that provide early warning of an impending or actual fire or gaseous hazard. The products detect, notify, and initiate control functions in case of hazard to life or property. For more information on li

16、fe safety, go to www.lifefiresafety.org. About the National Electrical Manufacturers Association (NEMA) Founded in 1926 and headquartered near Washington, D.C., NEMA represents nearly 400 member companies that manufacture products used in the generation, transmission and distribution, control, and e

17、nd use of electricity. These products are used in utility, industrial, commercial, institutional, and residential applications. The associations Medical Imaging however: 1) Do not use outdoors. If lightning lasts longer than the time delay, a shutdown will occur. 2) When welding or x-raying, bypass

18、the alarm system to avoid a shutdown. b) Some airborne contaminants absorb UV radiation. If there is potential for a lot of smoke before the fire, the UV detection might not detect the fire easily. c) Contaminants on the detector lens (steam, oil film, or smoke). If there is a buildup of contaminant

19、s, the detector will not respond to the fire. NEMA SB 23-2016 Page 9 2016 National Electrical Manufacturers Association 4.1.2 Infrared (IR) Detectors 4.1.2.1 General IR single- and dual-frequency detectors were introduced to solve problems associated with UV detectors. They are operated by detecting

20、 the heat element of a fire and analyzing amplitude and flicker frequency. As these devices are rarely used today, but were an interim development between UV detectors and UV/IR and IR3 detectors, this description is for reference purposes only. 4.1.2.2 Strengths IR flame detectors solve a number of

21、 the false alarm problems associated with UV detection and are not affected by hydrocarbon films. 4.1.2.3 Limitations a) Black-body radiation becomes a false-alarm issue for IR detectors. b) Water on the optical surfaces absorbs and scatters the heat energy from a fire, decreasing the overall sensit

22、ivity of the device. c) The majority of IR devices use the CO2emissions from a fire, so the device is sensitive to hydrocarbon fires only. The wavelength is typically approximately 4.4 microns, which coincides with the hot CO2emission peak of all burning carbonaceous materials. 4.1.3 Ultraviolet/Inf

23、rared (UV/IR) Detectors 4.1.3.1 General UV/IR detectors normally require both sensors to respond to a fire before an alarm signal is generated. This increases their false alarm immunity, removing the effects of each false alarm that generally upsets IR and UV detectors individually. However, the adv

24、antages, as well as the disadvantages, of both technologies are realized. UV/IR detectors will detect only hydrocarbon fires and are blinded by water, ice, oil films, and airborne solvents. Water, ice, and oil films in an outdoor environment can cause so many optical faults that, in time, the faults

25、 are simply ignored. This is dangerous, since the fault indicates that the device is potentially blinded to a fire condition. 4.1.3.2 Strengths a) Sensitive to hydrocarbons. b) Improved false alarm immunity. The detector requires a UV and an IR sensor to be satisfied so it can avoid UV-only or IR-on

26、ly nuisance alarms. c) Suitable for indoors or outdoors. With the improved false alarm immunity, the detector can be mounted outdoors and will not give false alarms. 4.1.3.3 Limitations a) Since the UV/IR detector must pick up the UV radiation, it has the same contamination limitations as a UV-only

27、detector. b) If there is a buildup of contaminants on the detector lens (steam, oil film, or smoke), the detector will not respond to a fire. NEMA SB 23-2016 Page 10 2016 National Electrical Manufacturers Association 4.1.4 Triple IR (IR3) Detectors 4.1.4.1 General With the advent of IR3 detectors, g

28、uard bands were added to the 4.3 M IR channel to improve differentiation of flame sources from non-flame background radiation, thereby reducing false alarms and increasing sensitivity. The sensor signals are correlated at either two or three optical wavelengths. They operate at moderate speed, typic

29、ally 10 seconds or less, with a range of up to 200 ft.plus from the flame source, when set at their highest sensitivity level, indoors and outdoors. This type of flame detector is well-suited to locations where combustion sources produce smoky fires. IR3 technology detects three distinct infrared wa

30、velengths (25 micron range) emitted by CO, CO2and a proprietary reference wavelength. Once the detector sees the three wavelengths, it decides if the radiation it is seeing is actually a fire or a nuisance alarm. Unlike UV and UV/IR, the IR3 does not alarm simply because radiation is present. In add

31、ition, it runs a series of algorithms that analyze the flame source for flicker frequency, magnitude ratios of the signals, and wavelength phase relationships. 4.1.4.2 Strengths a) Advanced false-alarm immunity. Immunity to false alarms from welding, lightning, x-rays, sparks/arcs, and sunlight. b)

32、Long detection range. IR3 has a longer range, when compared with UV or UV/IR. 4.1.4.3 Limitations a) Might be sensitive to very strong, close by, modulated energy sources. b) Cannot detect hydrogen or metal fires. c) Heater is required to keep snow, water, or moisture off the lens. d) Can detect ref

33、lected radiation from process relief flares. e) Can detect hot CO2emissions from gas turbine and vehicle engine exhausts. f) Responds to welding rod flux burning during arc welding operations. g) Exposure to black-body radiation affects the ratio between the sensors, causing the devices to desensiti

34、ze and, in some cases, become completely blind. h) Reflected sun radiation off water has a similar effect. Additionally, partial obscuration of one of the sensors due to water contamination can result in the fire being missed. NEMA SB 23-2016 Page 11 2016 National Electrical Manufacturers Associatio

35、n 4.1.5 Multi-Spectrum Infrared (MSIR) Detectors 4.1.5.1 General MSIR detectors sensor arrays use high-speed and wide temperature range photoconductive quantum sensors with four distinct wide spectral bands that include the 4.3-micron bandwidth: a) Wide Band IR: 35 microns b) Near Band IR: 0.71.1 mi

36、crons c) Visible Band: 0.40.7 microns 4.1.5.2 Strengths MSIR detectors employ wide band sensors, which can detect a greater variety of flames, including those from non-hydrocarbon fires such as silane, hydrogen, and metal fires. They are not limited to conventional hydrocarbon fires. They are also l

37、ess susceptible to false alarms from hot process and facilities where CO2emissions can desensitize or activate IR3 detectors. 4.1.5.3 Limitations MSIR detectors can be affected by atmospheric contaminants, such as fog, rain, and steam. As they employ multiple sensors looking at multiple wavelengths,

38、 they can also be affected by smoke or oil in the area being protected. Since it takes all sensors to detect their particular wavelength, if one or more of the sensors is affected, it could prevent detection of a fire. 4.2 VIDEO FLAME DETECTION (VFD) TECHNOLOGIES 4.2.1 General VFDs employ standard c

39、omplementary metal-oxide semiconductor (CMOS) image sensors, commonly used in CCTV cameras, combined with flame detection algorithms to establish the presence of fires. The imaging algorithms process the live video image from the CMOS array and analyze the shape and progression of would-be fires to

40、discriminate between flame and non-flame sources. VFD sensitivity is 200 ft. to a 1 sq. ft. pan fire of gasoline under absolute ideal conditions. The difference between this technology and conventional detection is that at 45 the off axis sensitivity is not reduced by 50% but remains at 100% of the

41、on axis sensitivity. This increases the coverage per point by up to 20%, which can mean fewer detectors are required. 4.2.2 Strengths a) Unlike IR or UV flame detectors, VFDs do not depend on emissions from CO2, water, and other products of combustion to detect fires; nor are they influenced by fire

42、s radiant intensity. As a result, they are commonly found in installations where flame detectors are required to discriminate between process fires and fires resulting from an accidental release of combustible material. b) By the very nature of the device looking for bright images within its FOV, it

43、 can be seen that black-body radiation and hot CO2emissions will have no effect. Water is less a problem, as the detectors are not looking for heat energy and light is easily transported through water. c) The output from a VFD provides not only indication of a fire, it also provides a live video ima

44、ge in the control room, giving operators real-time information that allows them to make correct decisions without endangering personnel. NEMA SB 23-2016 Page 12 2016 National Electrical Manufacturers Association d) False alarm immunity to hot CO2emissions is assured. Gas turbines emit strong exhaust

45、 gases at 4.3 M, the prime detection wavelength for IR detectors, causing them to false alarm. Since a VFD looks for bright images, it ignores the emission. e) VFDs are specifically designed to ignore flare radiation reflections false alarms. Black-body radiation emits radiation at 4.3 m, but again,

46、 it is not bright so the VFD ignores it. Arc welding is bright but doesnt form an image that has a fire-like shape, therefore no false alarms. f) A VFD system can be accessed remotely, enabling multiple authorized users to view live and recorded video at any time and from anywhere in the world. This

47、 is advantageous if users want a third party, such as a security firm for monitoring or an installer for system commissioning and maintenance, to gain access. 4.2.3 Limitations a) VFDs cannot detect flames that are invisible to the naked eye, such as hydrogen or methanol flames. Heavy smoke also imp

48、airs the detectors ability to detect fire, since visible radiation from fire is one of the technologys fundamental requirements. b) The device will respond only to a fire that is bright, and the response time is normally slightly slower (typically 78 seconds). NEMA SB 23-2016 Page 13 2016 National E

49、lectrical Manufacturers Association Section 5 HOW TO SELECT A FLAME DETECTOR 5.1 GENERAL Process and plant engineers in the oil and gas industry, and a wide range of other hazardous process and manufacturing industries, require continuous flame monitoring to prevent catastrophic fires. In order to select the correct detection equipment, users should endeavor to understand the principles of flame detection and review the types of detectors available today. Armed with this knowledge, they will be better able to match the appropriate flame detector to process an