1、Designation:E122610 Designation: E1226 12Standard Test Method forExplosibility of Dust Clouds1This 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 revision. A n
2、umber in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONParticulate solids of combustible materials present a significant risk of dust explosion if suspendedin air and subjected to an ignition
3、 source. The methods of this standard can be used to determine ifa dispersed dust cloud is “explosible” and, if so, to what degree it is explosible, i.e. that is, its“explosibility.” Knowledge that a dust may be explosible if dispersed as a dust cloud is important inthe conduct of a process hazard s
4、afety review. Contained herein is an explosibility or go/no-goscreening test procedure for the purpose of determining whether a dust sample is explosible.If a dust is explosible, the explosibility parameters, maximum explosion pressure, Pmax; maximumrate of pressure rise, (dP/dt)max; and explosibili
5、ty index, KSt, are useful in the design of explosionprevention and control measures as described in national (NFPA) and international (ISO, CEN andothers) explosion protection standards.1. Scope1.1 Purpose. The purpose of this test method is to provide standard test methods for characterizing the “e
6、xplosibility” of dustclouds in two ways, first by determining if a dust is “explosible,” meaning a cloud of dust dispersed in air is capable of propagatinga deflagration, which could cause a flash fire or explosion; or, if explosible, determining the degree of “explosibility,” meaning thepotential e
7、xplosion hazard of a dust cloud as characterized by the dust explosibility parameters, maximum explosion pressure,Pmax; maximum rate of pressure rise, (dP/dt)max; and explosibility index, KSt.1.2 Limitations. Results obtained by the application of the methods of this standard pertain only to certain
8、 combustioncharacteristics of dispersed dust clouds. No inference should be drawn from such results relating to the combustion characteristicsof dusts in other forms or conditions (e.g.,(for example, ignition temperature or spark ignition energy of dust clouds, ignitionproperties of dust layers on h
9、ot surfaces, ignition of bulk dust in heated environments, etc.)1.3 Use. It is intended that results obtained by application of this test be used as elements of an explosion risk assessment thattakes into account other pertinent risk factors; and in the specification of explosion prevention systems
10、(see, for example NFPA68, NFPA 69, and NFPA 654) when used in conjunction with approved or recognized design methods by those skilled in the art.NOTE 1Historically, the evaluation of the deflagration parameters of maximum pressure and maximum rate of pressure rise has been doneperformedusing a 1.2-L
11、 Hartmann Apparatus. Test Method E789, which describes this method, has been withdrawn. The use of data obtained from the test methodin the design of explosion protection systems is not recommended.1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are in
12、cluded in this standard.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior
13、to use.2. Referenced Documents2.1 ASTM Standards:2D3173 Test Method for Moisture in the Analysis Sample of Coal and CokeD3175 Test Method for Volatile Matter in the Analysis Sample of Coal and Coke1This test method is under the jurisdiction of ASTM Committee E27 on Hazard Potential of Chemicals and
14、is the direct responsibility of Subcommittee E27.05 onExplosibility and Ignitability of Dust Clouds.Current edition approved Jan. 1, 2010. Published March 2010. Originally approved in 1988. Last previous edition approved in 2009 as E122609. DOI: 10.1520/E1226-10.Current edition approved May 15, 2012
15、. Published July 2012. Originally approved in 1988. Last previous edition approved in 2010 as E1226 10. DOI:10.1520/E1226-12.2For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, re
16、fer to the standards Document Summary page on the ASTM website.1This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all
17、changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959
18、, United States.E789 Test Method for Dust Explosions in a 1.2-Litre Closed Cylindrical VesselE1445 Terminology Relating to Hazard Potential of ChemicalsE1515 Test Method for Minimum Explosible Concentration of Combustible Dusts2.2 NFPA Publication:3NFPA 68 Standard on Explosion Protection By Deflagr
19、ation VentingNFPA 69 Standard on Explosion Prevention SystemsNFPA 654 Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling ofCombustible Particulate Solids2.3 VDI Standard:VDI-3673 Pressure Release of Dust Explosions42.4 ISO Standard:ISO 6184/1 Exp
20、losion Protection Systems, Part 1, Determination of Explosion Indices of Combustible Dusts in Air53. Terminology3.1 For determination of terms relating to hazard potential of chemicals see Terminology E1445.3.2 Definitions of Terms Specific to This Standard:3.2.1 Pexthe maximum explosion pressure ri
21、se (above the pressure in the vessel at the time of ignition) reachedproducedduring the course of a single deflagration test (see Fig. 1).3.2.2 Pmaxthe maximum pressure (above pressure in the vessel at the time of ignition) reached during the course of adeflagration for the optimum concentration of
22、the dust tested. PmaxPmmaximum pressure rise produced during the course of asingle deflagration test that is corrected for the effects of ignitor pressure and cooling in the 20-L vessel (see Sections X1.8 andX1.9).3.2.3 Pex,athe maximum absolute pressure produced during the course of a single deflag
23、ration test, n Pex,a= Pex+ Pignition.3.2.4 Pmaxthe maximum pressure rise (above pressure in the vessel at the time of ignition) 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
24、 Fig. 2). It is reported in bar.3Available from National Fire Protection Association (NFPA), 1 Batterymarch Park, Quincy, MA 02169-7471, http:/www.nfpa.org.4Available from Beuth Verlag, D-1000 Berlin, Federal Republic of Germany or American National Standards Institute (ANSI), 25 W. 43rd St., 4th Fl
25、oor, New York, NY10036, http:/www.ansi.org.5Available from International Organization for Standardization (ISO), 1, ch. de la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http:/www.iso.ch.or from Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor
26、, New York, NY 10036, 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-LChamberE1226 1223.2.33.2.5 Pignitionthe absolute pressure in the vessel at the time of ignition.3.2.6 Pignitionthe pressure rise above
27、Pignitioncaused by activation of the ignitior(s) with no dust present in the chamber.3.2.7 (dP/dt)exthe maximum rate of pressure rise during the course of a single deflagration test (see Fig. 1).3.2.43.2.8 (dP/dt)maxmaximum value for the rate of pressure increase per unit time reached during the cou
28、rse of a deflagration forthe optimum concentration of the dust tested. It is determined by a series of tests over a large range of concentrations (see Fig.2). It is reported in bar/s.NOTE 2Recorder tracings of pressure (absolute) and rate of pressure rise for a typical dust deflagration in a 20-L ch
29、amber are shown in Fig. 1. Themaximum values, Pmaxand ( dP/dt)maxfor a dust are determined by testing over a large range of concentrations as shown in Fig. 2.3.2.53.2.9 deflagration index, KStmaximum dP/dt normalized to a 1.0-m3volume. It is measured at the optimum dustconcentration. KStis defined i
30、n accordance with the following cubic relationship:KSt5 dP/dt!maxV1/3(1)E1226-12_1where:P = pressure, bar,t = time, s,V = volume, m3, andKSt= bar m/s.3.2.10 explosiblea material with a Pressure Ratio equal or greater than 2.0 in any test when tested using the Explosibility orGo/No-go Screening Test
31、described in Section 13.NOTE 3An explosible dust when dispersed in air is capable of propagating a deflagration, which could cause a flash fire or explosion depending onthe level of confinement.3.2.63.2.11 ignition delay time, tdexperimental parameter defined as the time interval between the initiat
32、ion of the dustdispersion procedure (the time at which the dispersion air starts to enter the chamber) in an experimental apparatus and theactivation of the ignition source (see Fig. 1). The ignition delay time characterizes the turbulence level prevailing at ignition underthe defined test condition
33、s.3.2.7Pressure Ratio (PR)3.2.12 pressure ratio (PR), nPR=(Pex,aPignitor)/PignitionPR=(Pex,aPignitor)/PignitionFIG. 2 Pmaxand (dP/dt)maxas a Function of Concentration for aTypical Dust in a 20-L ChamberE1226 123NOTE 4When testing in the Siwek 20-L vessel (see Appendix X1) PR may be calculated using
34、the corrected explosion pressure,nPR=(Pm+Pignition)/Pignition.4. Summary of Test Method4.1 A dust cloud is formed in a closed combustion chamber by an introduction of the material with air.4.2 Ignition of this dust-air mixture is then attempted after a specified delay time by an ignition source loca
35、ted at the center ofthe chamber.4.3 The pressure time curve is recorded on a suitable piece of equipment.5. Significance and Use5.1 This test method provides a procedure for performing laboratory tests to evaluate deflagration parameters of dusts.5.2 The data developed by this test method may be use
36、d for the purpose of sizing deflagration vents in conjunction with thenomographs and equations published in NFPA 68, ISO 6184/1, or VDI 3673.5.3 The values obtained by this testing technique are specific to the sample tested and the method used and are not to beconsidered intrinsic material constant
37、s.5.4 For hard-to-ignite dusts with low KSt-values, a very strong ignitor may overdrive a 20-L chamber, as discussed in E1515and Ref 2. and Ref (1).6If a dust has measurable (nonzero) Pmax- and KSt-values with a 5000 or 10 000-J ignitor but not with a2500-J ignitor in a 20-L chamber, this may be an
38、overdriven system. In this case, it is recommended that the dust be tested witha 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 industrial situations where extreme levels of turbulence may be encountered, such as th
39、e rapid introduction ofexpanding gases resulting from combustion in connected piping or operations where hybrid mixtures (combustible dusts andcombustible gases or vapors) are encountered, the use of the deflagration indices based on this test method for the sizing ofdeflagration vents may not be po
40、ssible.7. Apparatus7.1 The equipment consists of a closed steel combustion chamber with an internal volume of at least 20 L, spherical orcylindrical (with a length to diameter ratio of approximately 1:1) in shape.7.2 The apparatus must be capable of dispersing a fairly uniform dust cloud of the mate
41、rial.7.3 The pressure transducer and recording equipment must have a combined response rate greater than the maximum measuredrates of pressure rise.7.4 An example of a chamber and specific procedures that have been found suitable are shown in Appendix X1. This chamberhas been calibrated as described
42、 in Section 10.7.5 Examples of other test chambers that have not yet been calibrated are listed in Appendix X2.8. Safety Precautions8.1 Prior to handling a dust material, the toxicity of the sample and its combustion products must be considered. Thisinformation is generally obtained from the manufac
43、turer or supplier. Appropriate safety precautions must be taken if the materialhas toxic or irritating characteristics. Tests using this apparatus should be conducted in a ventilated hood or other area havingadequate ventilation.8.2 Before initiating a test, a physical check of all gaskets and fitti
44、ngs should be made to prevent leakage.8.3 All enclosures containing electrical equipment should be connected to a common ground. Shielded cables should be used.8.4 If chemical ignitors are used as an ignition source, safety in handling and use is a primary consideration. Ignition byelectrostatic dis
45、charge must be considered a possibility. When handling these ignitors, eye protection must be worn at all times.A grounded, conductive tabletop is recommended for preparation. Federal, state, and local regulations for the procurement, use,and storage of chemical ignitors must be followed.8.5 All tes
46、ting should initially be conducted with small quantities of sample to prevent overpressurization due to high energymaterial.8.6 In assembling the electrical circuitry for this apparatus, standard wiring and grounding procedures must be followed. If ahigh-voltage spark circuit is used, it presents an
47、 electric shock hazard and adequate interlocking and shielding must be employedto prevent contact.8.7 The operator should work from a protected location in case of vessel or electrical failure.8.8 The vessel should be designed and fabricated in accordance with theASME Boiler and Pressure Vessel Code
48、, Section VIII.A maximum allowable working pressure (MAWP) of at least 15 bar is recommended.6MNL 32 ASTM Manual on Test Sieving Methods is available from ASTM Headquarters, 100 Barr Harbor Drive, W. Conshohocken, PA 19428.6The boldface numbers in parentheses refer to a list of references at the end
49、 of this standard.E1226 1249. Sampling, Test Specimens, and Test Units9.1 It is not practical to specify a single method of sampling dust 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 as describedin 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 system, it is recommended that the test sample be at least 95 % minus 200 mesh (75
