1、Designation: E 1226 05Standard Test Method forPressure and Rate of Pressure Rise for Combustible Dusts1This standard is issued under the fixed designation E 1226; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last rev
2、ision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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 th
3、e maximum 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, concen
4、tration, 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 laborato
5、ry 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
6、purpose 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
7、within 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
8、 design 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 ma
9、terials,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 1The evaluation of the deflagration
10、 parameters of maximumpressure and maximum rate of pressure rise can also be done using a 1.2-LHartmann Apparatus. Test Method E 789, has been published regardingthis application; however, the use of these data in the design ofdeflagration venting and containment systems is not recommended.1.4 This
11、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 Documents2
12、.1 ASTM Standards:3D 3173 Test Method for Moisture in theAnalysis Sample ofCoal and CokeD 3175 Test Method for Volatile Matter in the AnalysisSample of Coal and CokeE 789 Test Method for Pressure and Rate of Pressure Risefor Dust Explosions in a 1.2-Litre Closed CylindricalVesselE 1515 Test Method f
13、or Minimum Explosible Concentra-tion of Combustible Dusts2.2 NFPA Publication:NFPA 68 Guide for Deflagration Venting41This test method is under the jurisdiction of ASTM Committee E27 on HazardPotential of Chemicals and is the direct responsibility of Subcommittee E27.05 onDusts.Current edition appro
14、ved Sept. 15, 2005. Published November 2005. Originallyapproved in 1988. Last previous edition approved in 2000 as E 1226 00e1.2The 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, orcont
15、act ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Available from National Fire Protection Association, Batterymarch Park,Quincy, MA 02269.1Copyright ASTM International, 100 Barr Harbor D
16、rive, PO Box C700, West Conshohocken, PA 19428-2959, United States.2.3 VDI Standard:VDI-3673 Pressure Release of Dust Explosions52.4 ISO Standard:ISO 6184/1 Explosion Protection Systems, Part 1, Determi-nation of Explosion Indices of Combustible Dusts in Air63. Terminology3.1 Definitions of Terms Sp
17、ecific 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 ignition) reached during the course
18、 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 test (see Fig. 1).3.1.4 (dP/dt)
19、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/s.NOTE 2Recorder tracings of p
20、ressure (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, KStmaximum dP/dt normalizedto
21、 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 parameter de-fined as the time interva
22、l 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 prevailing at ignitionunder the def
23、ined 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 centerof the chamber.4.3 The pre
24、ssure time curve is recorded on a suitable pieceof equipment.5. Significance and Use5.1 This test method provides a procedure for performinglaboratory tests to evaluate deflagration parameters of dusts.5Available from Beuth Verlag, D-1000 Berlin, Federal Republic of Germany orfrom American National
25、Standards Institute, 1430 Broadway, NY, NY 10018.6Available from ISO Case Postale 56, CH-1211, Geneva, 20, Switzerland orfrom ANSI.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
26、 of Concentration for aTypical Dust in a 20-L ChamberE12260525.2 The data developed by this test method may be used forthe purpose of sizing deflagration vents in conjunction with thenomographs published in NFPA 68, ISO 6184/1, or VDI 3673.5.3 The values obtained by this testing technique are spe-ci
27、fic 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 chamber, as discussed inE 1515 and Ref 2. If a dust has measurable (nonzero) Pmax- andKSt-values with a 50
28、00 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 chamber such as a 1-m3chamber to determine if it is actually explosible.6. Interferences6.1 In certain in
29、dustrial situations where extreme levels ofturbulence may be encountered, such as the rapid introductionof expanding gases resulting from combustion in connectedpiping or operations where hybrid mixtures (combustible dustsand combustible gases or vapors) are encountered, the use ofthe deflagration i
30、ndices 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 least 20 L, spherical orcylindrical (with a length to diameter ratio of approximately1:1) in shape.7.2 The
31、 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 maximummeasured rates of pressure rise.7.4 An example of a chamber and specific procedures thathave been found su
32、itable 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 Precautions8.1 Prior to handling a dust material, the toxicity of thesample and its combustion products
33、 must be considered. Thisinformation is generally obtained from the manufacturer orsupplier. Appropriate safety precautions must be taken if thematerial has toxic or irritating characteristics. Tests using thisapparatus should be conducted in a ventilated hood or otherarea having adequate ventilatio
34、n.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 ground. Shielded cables should beused.8.4 If chemical ignitors are used as an ignition source, safetyin hand
35、ling 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, conductive tabletop is recommended forpreparation. Federal, state, and local regulations for the pro-curemen
36、t, 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 In assembling the electrical circuitry for this apparatus,standard wiring and grounding procedures must b
37、e 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 a protected location incase of vessel or electrical failure.8.8 The vessel should be designed and fabri
38、cated 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 Units9.1 It is not practical to specify a single method of samplingdust for test purposes because the ch
39、aracter of the material andits available form affect selection of the sampling procedure.Generally accepted sampling procedures should be used asdescribed in MNL 32.79.2 Tests may be run on an as-received sample. However,due to the possible accumulation of fines at some location in aprocessing syste
40、m, 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 besieved.NOTE 3The operator should consider the thermal stability of the dustduring any grinding or pulverizin
41、g. 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 dust deflagrationtests on materials as sampled from a process because process dust streamsmay contain a wid
42、e 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 maynot pass through a relatively coarse screen may produce dust deflagra-tions. When a material is teste
43、d 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 normal or drier product than normal may increase the explosionseverity.9.4 The moisture content of the
44、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 sample. ASTM lists many methods for moisturedetermination in the Annual Book of ASTM Standards. Sample drying
45、 isequally complex due to the presence of volatiles, lack of or varyingporosity (see Test Methods D 3173 and D 3175), 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.7M
46、NL 32 ASTM Manual on Test Sieving Methods is available from ASTMHeadquarters, 100 Barr Harbor Drive, W. Conshohocken, PA 19428.E122605310. Calibration and Standardization10.1 The objective of this test method is to develop data thatcan be correlated to those from the 1-m3chamber (described inISO 618
47、4/1 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 results, the test vessel to be used for routine workmust be standardized using dust samples whose KStand P
48、maxparameters 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 % wi
49、th 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 within certain dustclasses, it is permissible to reduce the number of standardiza-tion dusts tested in these ranges.10.4 The calibration and standardization procedure for achamber will normally involve varying the dispersion proce-dure (especially the dispersion and delay time) so that themeasured data are comparable to those from the 1-m3chamber.Once the specific dispersion procedures (that produce datacomparab
