ASTM E1226-2009 Standard Test Method for Pressure and Rate of Pressure Rise for Combustible Dusts.pdf

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1、Designation: E1226 09Standard Test Method forPressure and Rate of Pressure Rise for Combustible Dusts1This standard is issued under the fixed designation E1226; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revis

2、ion. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONThe primary objective for the laboratory determination of the dust deflagration index, KSt, themaximum pressure, Pmax, and the m

3、aximum rate of pressure rise, (dP/dt)max, is the use of these valuesfor the design of protection systems. These parameters provide a measure of the potential severity ofa deflagration of a combustible dust-air mixture. These parameters are a function of many factors, suchas the turbulence, concentra

4、tion, and homogeneity of the dust-air mixture; the type, energy, andlocation of the ignition source; the geometry of the test vessel; the particle size distribution of the dust;and the initial temperature and pressure of the tested mixture. Therefore, it is necessary to develop astandard laboratory

5、test method, the data from which can be referenced against data from large-scaletesting. For information on the sizing of deflagration vents, see NFPA 68.This test method describes procedures for explosibility testing of dusts in laboratory chambers thathave volumes of 20 L or greater. It is the pur

6、pose of this test method to provide information that canbe used to predict the effects of an industrial scale deflagration of a dust-air mixture without requiringlarge-scale tests.1. Scope1.1 This test method is designed to determine the deflagra-tion parameters of a combustible dust-air mixture wit

7、hin anear-spherical closed vessel of 20 L or greater volume. Theparameters measured are the maximum pressure and themaximum rate of pressure rise.1.2 Data obtained from this test method provide a relativemeasure of deflagration characteristics. The data have alsobeen shown to be applicable to the de

8、sign of protectivemeasures, such as deflagration venting (1).21.3 This test method should be used to measure and describethe properties of materials in response to heat and flame undercontrolled laboratory conditions and should not be used todescribe or appraise the fire hazard or fire risk of mater

9、ials,products, or assemblies under actual fire conditions. However,results of this test may be used as elements of a fire riskassessment that takes into account all of the factors that arepertinent to an assessment of the fire hazard of a particular enduse.NOTE 1Historically, the evaluation of the d

10、eflagration parameters ofmaximum pressure and maximum rate of pressure rise has been doneusing a 1.2-L Hartmann Apparatus. Test Method E789, which describesthis method, has been withdrawn. The use of data obtained from the testmethod in the design of explosion protection systems is not recommended.1

11、.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Do

12、cuments2.1 ASTM Standards:3D3173 Test Method for Moisture in the Analysis Sample ofCoal and CokeD3175 Test Method for Volatile Matter in the AnalysisSample of Coal and CokeE789 Test Method for Dust Explosions in a 1.2-Litre ClosedCylindrical Vessel4E1515 Test Method for Minimum Explosible Concentrat

13、ionof Combustible Dusts1This test method is under the jurisdiction of ASTM Committee E27 on HazardPotential of Chemicals and is the direct responsibility of Subcommittee E27.05 onExplosibility and Ignitability of Dust Clouds.Current edition approved Nov. 15, 2009. Published January 2010. Originallya

14、pproved in 1988. Last previous edition approved in 2005 as E1226 051. DOI:10.1520/E1226-09.2The boldface numbers in parentheses refer to a list of references at the end ofthis test method.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at service

15、astm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Withdrawn. The last approved version of this historical standard is referencedon www.astm.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Consho

16、hocken, PA 19428-2959, United States.2.2 NFPA Publication:NFPA 68 Guide for Deflagration Venting52.3 VDI Standard:VDI-3673 Pressure Release of Dust Explosions62.4 ISO Standard:ISO 6184/1 Explosion Protection Systems, Part 1, Determi-nation of Explosion Indices of Combustible Dusts in Air73. Terminol

17、ogy3.1 Definitions of Terms Specific to This Standard:3.1.1 Pexthe maximum explosion pressure (above thepressure in the vessel at the time of ignition) reached during thecourse of a single deflagration test (see Fig. 1).3.1.2 Pmaxthe maximum pressure (above pressure in thevessel at the time of ignit

18、ion) reached during the course of adeflagration for the optimum concentration of the dust tested.Pmaxis determined by a series of tests over a large range ofconcentrations (see Fig. 2). It is reported in bar.3.1.3 (dP/dt)exthe maximum rate of pressure rise duringthe course of a single deflagration t

19、est (see Fig. 1).3.1.4 (dP/dt)maxmaximum value for the rate of pressureincrease per unit time reached during the course of a deflagra-tion for the optimum concentration of the dust tested. It isdetermined by a series of tests over a large range of concen-trations (see Fig. 2). It is reported in bar/

20、s.NOTE 2Recorder tracings of pressure (absolute) and rate of pressurerise for a typical dust deflagration in a 20-L chamber are shown in Fig. 1.The maximum values, Pmaxand ( dP/dt)maxfor a dust are determined bytesting over a large range of concentrations as shown in Fig. 2.3.1.5 deflagration index,

21、 KStmaximum dP/dt normalizedto a 1.0-m3volume. It is measured at the optimum dustconcentration. KStis defined in accordance with the followingcubic relationship:KSt5 dP/dt!maxV1/3(1)where:P = pressure, bar,t = time, s,V = volume, m3, andKSt= bar m/s.3.1.6 ignition delay time, tdexperimental paramete

22、r de-fined as the time interval between the initiation of the dustdispersion procedure (the time at which the dispersion air startsto enter the chamber) in an experimental apparatus and theactivation of the ignition source (see Fig. 1). The ignition delaytime characterizes the turbulence level preva

23、iling at ignitionunder the defined test conditions.4. Summary of Test Method4.1 A dust cloud is formed in a closed combustion chamberby an introduction of the material with air.4.2 Ignition of this dust-air mixture is then attempted after aspecified delay time by an ignition source located at the ce

24、nterof the chamber.5Available from National Fire Protection Association (NFPA), 1 BatterymarchPark, Quincy, MA 02169-7471, http:/www.nfpa.org.6Available from Beuth Verlag, D-1000 Berlin, Federal Republic of Germany orAmerican National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, NewYork,NY

25、 10036, http:/www.ansi.org.7Available from International Organization for Standardization (ISO), 1, ch. dela Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http:/www.iso.ch. or fromAvailable fromAmerican National Standards Institute (ANSI),25 W. 43rd St., 4th Floor, New York, NY 1003

26、6, http:/www.ansi.org.FIG. 1 Typical Recorder Tracings of Absolute Pressure, P, andRate of Pressure Rise, dP/dt, for a Dust Deflagration in a 20-LChamberFIG. 2 Pmaxand (dP/dt)maxas a Function of Concentration for aTypical Dust in a 20-L ChamberE1226 0924.3 The pressure time curve is recorded on a su

27、itable pieceof equipment.5. Significance and Use5.1 This test method provides a procedure for performinglaboratory tests to evaluate deflagration parameters of dusts.5.2 The data developed by this test method may be used forthe purpose of sizing deflagration vents in conjunction with thenomographs p

28、ublished in NFPA 68, ISO 6184/1, or VDI 3673.5.3 The values obtained by this testing technique are spe-cific to the sample tested and the method used and are not to beconsidered intrinsic material constants.5.4 For hard-to-ignite dusts with low KSt-values, a verystrong ignitor may overdrive a 20-L c

29、hamber, as discussed inE1515 and Ref 2. If a dust has measurable (nonzero) Pmax- andKSt-values with a 5000 or 10 000-J ignitor but not with a2500-J ignitor in a 20-L chamber, this may be an overdrivensystem. In this case, it is recommended that the dust be testedwith a 10 000-J ignitor in a larger c

30、hamber such as a 1-m3chamber to determine if it is actually explosible.6. Interferences6.1 In certain industrial situations where extreme levels ofturbulence may be encountered, such as the rapid introductionof expanding gases resulting from combustion in connectedpiping or operations where hybrid m

31、ixtures (combustible dustsand combustible gases or vapors) are encountered, the use ofthe deflagration indices based on this test method for the sizingof deflagration vents may not be possible.7. Apparatus7.1 The equipment consists of a closed steel combustionchamber with an internal volume of at le

32、ast 20 L, spherical orcylindrical (with a length to diameter ratio of approximately1:1) in shape.7.2 The apparatus must be capable of dispersing a fairlyuniform dust cloud of the material.7.3 The pressure transducer and recording equipment musthave a combined response rate greater than the maximumme

33、asured rates of pressure rise.7.4 An example of a chamber and specific procedures thathave been found suitable are shown in Appendix X1. Thischamber has been calibrated as described in Section 10.7.5 Examples of other test chambers that have not yet beencalibrated are listed in Appendix X2.8. Safety

34、 Precautions8.1 Prior to handling a dust material, the toxicity of thesample and its combustion products must be considered. Thisinformation is generally obtained from the manufacturer orsupplier. Appropriate safety precautions must be taken if thematerial has toxic or irritating characteristics. Te

35、sts using thisapparatus should be conducted in a ventilated hood or otherarea having adequate ventilation.8.2 Before initiating a test, a physical check of all gasketsand fittings should be made to prevent leakage.8.3 All enclosures containing electrical equipment shouldbe connected to a common grou

36、nd. Shielded cables should beused.8.4 If chemical ignitors are used as an ignition source, safetyin handling and use is a primary consideration. Ignition byelectrostatic discharge must be considered a possibility. Whenhandling these ignitors, eye protection must be worn at alltimes. A grounded, cond

37、uctive tabletop is recommended forpreparation. Federal, state, and local regulations for the pro-curement, use, and storage of chemical ignitors must befollowed.8.5 All testing should initially be conducted with smallquantities of sample to prevent overpressurization due to highenergy material.8.6 I

38、n assembling the electrical circuitry for this apparatus,standard wiring and grounding procedures must be followed. Ifa high-voltage spark circuit is used, it presents an electricshock hazard and adequate interlocking and shielding must beemployed to prevent contact.8.7 The operator should work from

39、 a protected location incase of vessel or electrical failure.8.8 The vessel should be designed and fabricated in accor-dance with the ASME Boiler and Pressure Vessel Code,Section VIII. A maximum allowable working pressure(MAWP) of at least 15 bar is recommended.9. Sampling, Test Specimens, and Test

40、Units9.1 It is not practical to specify a single method of samplingdust for test purposes because the character of the material andits available form affect selection of the sampling procedure.Generally accepted sampling procedures should be used asdescribed in MNL 32.89.2 Tests may be run on an as-

41、received sample. However,due to the possible accumulation of fines at some location in aprocessing system, it is recommended that the test sample be atleast 95 % minus 200 mesh (75 m).9.3 To achieve this particle fineness ($95 % minus 200mesh), the sample may be ground or pulverized or it may besiev

42、ed.NOTE 3The operator should consider the thermal stability of the dustduring any grinding or pulverizing. In sieving the material, the operatormust verify that there is no selective separation of components in a dustthat is not a pure substance.NOTE 4It may be desirable in some cases to conduct dus

43、t deflagrationtests on materials as sampled from a process because process dust streamsmay contain a wide range of particle sizes or have a well-defined specificmoisture content, materials consisting of a mixture of chemicals may beselectively separated on sieves and certain fibrous materials which

44、maynot pass through a relatively coarse screen may produce dust deflagra-tions. When a material is tested in the as-received state, it should berecognized that the test results may not represent the most severe dustdeflagration possible. Any process change resulting in a higher fraction offines than

45、 normal or drier product than normal may increase the explosionseverity.9.4 The moisture content of the test sample should notexceed 5 % in order to avoid test results of a given dust beingnoticeably influenced.NOTE 5There is no single method for determining the moisturecontent or for drying a sampl

46、e. ASTM lists many methods for moisture8MNL 32 ASTM Manual on Test Sieving Methods is available from ASTMHeadquarters, 100 Barr Harbor Drive, W. Conshohocken, PA 19428.E1226 093determination in the Annual Book of ASTM Standards. Sample drying isequally complex due to the presence of volatiles, lack

47、of or varyingporosity (see Test Methods D3173 and D3175), and sensitivity of thesample to heat. Therefore, each must be dried in a manner that will notmodify or destroy the integrity of the sample. Hygroscopic materials mustbe desiccated.10. Calibration and Standardization10.1 The objective of this

48、test method is to develop data thatcan be correlated to those from the 1-m3chamber (described inISO 6184/1 and VDI 3673) in order to use the nomograms (see5.2).10.2 Because a number of factors (concentration, unifor-mity of dispersion, turbulence of ignition, sample age, etc.) canaffect the test res

49、ults, the test vessel to be used for routine workmust be standardized using dust samples whose KStand Pmaxparameters are known in the 1-m3chamber. Samples used forstandardization should provide a wide range of KStvalues. Aminimum of five different dust samples are required over eachof the following three KStranges: 1200, 201300, and 300bar m/s. The Pmaxvalue for each dust must agree to within610 % with the 1-m3value and the KStvalue must agree towithin 620 %.10.3 In cases where the test apparatus will not be used todetermine deflagration indices of dusts with