1、NFPA274 Standard Test Method to Evaluate Fire Performance Characteristics of Pipe Insulation 2013 Edition NFPA, 1 Batterymarch Park, Quincy, MA 02169-7471 An International Codes and Standards Organization IMPORTANT NOTICES AND DISCLAIMERS CONCERNING NFPADOCUMENTSNOTICE AND DISCLAIMER OF LIABILITY CO
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29、d.NFPA274StandardTest Method to Evaluate Fire Performance Characteristicsof Pipe Insulation2013 EditionThis edition of NFPA 274, Standard Test Method to Evaluate Fire Performance Characteristics ofPipe Insulation, was prepared by the Technical Committee on Fire Tests. It was issued by theStandards C
30、ouncil on November 27, 2012, with an effective date of December 17, 2012, andsupersedes all previous editions.This edition of NFPA 274 was approved as an American National Standard on Decem-ber 17, 2012.Origin and Development of NFPA 274NFPA 274, Test Method to Evaluate Fire Performance Characterist
31、ics of Pipe Insulation, was devel-oped by the Technical Committee on Fire Tests to fill the need for a standard method ofdetermining the fire performance of pipe insulation materials. Other codes and standardshave identified the issue of the installation of such materials in air-handling plenums. Al
32、-though NFPA 274 does not prescribe pass/fail criteria, suggested acceptance criteria areprovided in Annex B for consideration by the other referencing codes and standards.The 2009 edition included a new requirement for a quantifiable determination of thepresence of flames at the top of the exhaust
33、chase using thermocouples.The 2013 edition is a reconfirmation of the previous edition.2741NFPA and National Fire Protection Association are registered trademarks of the National Fire Protection Association, Quincy, Massachusetts 02169.Technical Committee on Fire TestsBarry L. Badders, Jr., ChairSou
34、thwest Research Institute, TX RTFarid Alfawakhiri, American Iron and Steel Institute,IL MJesse J. Beitel, Hughes Associates, Inc., MD SERhonda P. Byrne, QAI Laboratories, CA RTGordon H. Damant, Inter-City Testing in such a case, it is notnecessary to remove the CO2from the oxygen line. The advan-tag
35、e is that the chemical scrubbing agent, which is costly andneeds careful handling, can be avoided.C.1.2 In this annex, equations are provided that should beused when CO2is measured but not scrubbed out of the sam-pling lines. Two cases are considered. In the first case, part ofthe dried and filtered
36、 sample stream is diverted into infraredCO2and CO analyzers. In the second case, a water vapor ana-lyzer is also added. To avoid condensation when measuringwater vapor concentration in the flow of combustion prod-ucts, a separate sampling system with heated filters, heatedsampling lines, and a heate
37、d analyzer is needed.C.2 Symbols. The following symbols are used in this annex(in addition to those in Section 8.2):Ma= molecular weight of air (kg/kmol)Me= molecular weight of the combustion products(kg/kmol)me= exhaust duct mass flow rate (kg/sec)td1= time delay of the CO2analyzer (sec)td2= time d
38、elay of the CO analyzer (sec)td3= time delay of the water vapor analyzer (sec)dotnospXCO20 = initial CO2reading, mole fraction27411ANNEX C2013 EditiondotnospXCO0= initial CO reading, mole fractiondotnospXHO02= initial water vapor reading, mole fractiondotnospXaO2= ambient oxygen mole fraction (mol/m
39、ol)dotnospXCO21= CO2reading before delay time correction, molefractiondotnospXCO1= CO reading before delay time correction, molefractiondotnospXHO21= water vapor reading before delay time correction,mole fractiondotnospXCO2= CO2reading after delay time correction, molefractiondotnospXCO= CO reading
40、after delay time correction, molefractiondotnospXHO2= water reading after delay time correction, molefraction = oxygen depletion factorC.3 Where CO2and CO Are Measured.C.3.1 As in the case of the oxygen analyzer, measurements ofCO2and CO should be time-shifted to take transport time inthe sampling l
41、ines into account as follows:dotnospdotnospdotnospdotnospdotnospdotnospXt XttXtXttXtXttdddOOCO COCO CO2222() ()() ()()=+=+=+111122()The delay times for the CO2and CO analyzers are usuallydifferent (smaller) from the delay time for the oxygen (O2)analyzer.C.3.2 The exhaust duct flow is determined as
42、follows:dotnospmCPTee=C.3.3 The rate of heat release now can be determined asfollows:dotnospdotnospdotnospdotnospqHrXXXc a= 1 100 172 11 1 084022.()()+OCOOdotnospmeC.3.4 The oxygen depletion factor is calculated as follows:=dotnospdotnospdotnospdotnospdotnospdotnosp dotnosp dotnospdotnospXXXXXX X XX
43、O0CO CO O CO0O0CO CO O22 2222 2111( )( )( )C.3.5 The ambient mole fraction of oxygen (O2) is deter-mined as follows:dotnosp dotnospdotnospX XXaO HO0O02221=( )( )C.3.6 The second value in the numerator of the factor inbrackets in the equation in C.3.3 is a correction factor forincomplete combustion o
44、f some carbon to CO instead of CO2.In fact, XCOis usually very small, so that it can be disregardedin the equations in C.3.3 and C.3.4. The practical implicationof this value is that a CO analyzer will generally not result in anoticeable increase in accuracy of heat release rate measure-ments. Conse
45、quently, the equations in C.3.3 and C.3.4 can bepermitted to be used even if no CO analyzer is present byusing the setting XCO= 0.C.4 Where Water Vapor Is Also Measured.C.4.1 In an open combustion system, such as that used in thistest method, the flow rate of air entering the system cannot bemeasure
46、d directly but is inferred from the flow rate measuredin the exhaust duct. An assumption regarding the expansiondue to combustion of the fraction of the air that is fully de-pleted of its oxygen is necessary. This expansion depends onthe composition of the fuel and the actual stoichiometry of thecom
47、bustion. A suitable average value for the volumetric ex-pansion factor is 1.084, which is the factor for propane.C.4.2 This expansion factor value is already incorporatedwithin the equation in 8.4.2 and the equation in C.3.3. It canbe assumed that the exhaust gases consist primarily of nitro-gen, ox
48、ygen, CO2, water vapor, and CO; thus, measurementsof these gases can be used to determine the actual expansion.(It is assumed that the measurements of oxygen, CO2, and COrefer to a dry gas stream, while the water vapor measurementcorresponds to total stream flow.) The mass flow rate in theexhaust du
49、ct is then more accurately determined by the fol-lowing equation:dotnospmCPTMMeeea=C.4.2.1 The molecular weight, Me, of the exhaust gases isdetermined as follows:M X XXe= +( )( )45 1 25 4 4dotnosp dotnospdotnospHO O CO2 22+C.4.2.2 Using 28.97 as the value for Ma, the heat release rateis determined as follows:dotnospdotnospdotnosp dotnospdotnospdotnospdotnospqtHrXX XXXc()( )( )=1 10 11.0HOO0O COO022 2221 XXXmeCO0 O22dotnospC.4.3 The water vapor readings used in the equation inC.4.2.2 are time-shifte
