1、Designation: E1226 12E1226 12aStandard 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 number in pa
2、rentheses 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 source. Th
3、e methods of this standard can be used to determine ifa dispersed dust cloud is “explosible” and, if so, to what degree it is explosible, 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 safety review. Co
4、ntained 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 explosibility index, KSt, a
5、re 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 “explosibility” of
6、 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 explosion hazard
7、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 combustionchar
8、acteristics of dispersed dust clouds. No inference should be drawn from such results relating to the combustion characteristicsof dusts in other forms or conditions (for example, ignition temperature or spark ignition energy of dust clouds, ignition propertiesof dust layers on hot surfaces, ignition
9、 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 (see, for example NFP
10、A68, 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 performed usinga 1.2-L Hartmann Apparatus. Test
11、 Method E789, which describes this method, has been withdrawn. The use of data obtained from the test method inthe 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 included in this standard.1
12、.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 to use.2. Referenced Docu
13、ments2.1 ASTM Standards:2D3173 Test Method for Moisture in the Analysis Sample of Coal and Coke1 This test method is under the jurisdiction of ASTM Committee E27 on Hazard Potential of Chemicals and is the direct responsibility of Subcommittee E27.05 onExplosibility and Ignitability of Dust Clouds.C
14、urrent edition approved May 15, 2012Dec. 1, 2012. Published July 2012January 2013. Originally approved in 1988. Last previous edition approved in 20102012 asE1226 10.E1226 12. DOI: 10.1520/E1226-12.10.1520/E1226-12A.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM
15、Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This 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 t
16、o the previous version. Becauseit may not be technically possible to adequately depict all 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.Copyrig
17、ht ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1D3175 Test Method for Volatile Matter in the Analysis Sample of Coal and CokeE789 Test Method for Dust Explosions in a 1.2-Litre Closed Cylindrical Vessel (Withdrawn 2007)3E1445 Terminology Rel
18、ating to Hazard Potential of ChemicalsE1515 Test Method for Minimum Explosible Concentration of Combustible Dusts2.2 NFPA Publication:4NFPA 68 Standard on Explosion Protection By Deflagration VentingNFPA 69 Standard on Explosion Prevention SystemsNFPA 654 Standard for the Prevention of Fire and Dust
19、 Explosions from the Manufacturing, Processing, and Handling ofCombustible Particulate Solids2.3 VDI Standard:VDI-3673 Pressure Release of Dust Explosions52.4 ISO Standard:ISO 6184/1 Explosion Protection Systems, Part 1, Determination of Explosion Indices of Combustible Dusts in Air63. Terminology3.
20、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 pressure rise (above the pressure in the vessel at the time of ignition) produced during the course ofa single deflagration test (see F
21、ig. 1).3.2.2 Pmmaximum pressure rise produced during the course of a single deflagration test that is corrected for the effects ofignitor pressure and cooling in the 20-L vessel (see Sections X1.8 and X1.9).3.2.3 Pex,athe maximum absolute pressure produced during the course of a single deflagration
22、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. Pmax is determined by a series of tests over a large range ofconcentrations (see Fig
23、. 2). It is reported in bar.3 The last approved version of this historical standard is referenced on www.astm.org.4 Available from National Fire Protection Association (NFPA), 1 Batterymarch Park, Quincy, MA 02169-7471, http:/www.nfpa.org.5 Available from Beuth Verlag, D-1000 Berlin, Federal Republi
24、c of Germany or American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY10036, http:/www.ansi.org.6 Available 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 A
25、vailable from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.FIG. 1 Typical Recorder Tracings of Absolute Pressure, P, and Rate of Pressure Rise, dP/dt, for a Dust Deflagration in a 20-L ChamberE1226 12a2FIG. 2 Pmax and (dP/dt)max as a
26、 Function of Concentration for a Typical Dust in a 20-L ChamberE1226 12a3E1226 12a4E1226 12a5E1226 12a63.2.5 Pignitionthe absolute pressure in the vessel at the time of ignition.3.2.6 Pignitionthe pressure rise above Pignition caused by activation of the ignitior(s) with no dust present in the chamb
27、er.3.2.7 (dP/dt)exthe maximum rate of pressure rise during the course of a single deflagration test (see Fig. 1).3.2.8 (dP/dt)maxmaximum value for the rate of pressure increase per unit time reached during the course of a deflagration forthe optimum concentration of the dust tested. It is determined
28、 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 chamber are shown in Fig. 1. Themaximum values, Pmax and (dP/dt)max for a dust are determ
29、ined by testing over a large range of concentrations as shown in Fig. 2.3.2.9 deflagration index, KStmaximum dP/dt normalized to a 1.0-m3 volume. It is measured at the optimum dustconcentration. KSt is defined in accordance with the following cubic relationship:KSt5dP/dt!max V1/3 (1)where:P = pressu
30、re, 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 described in Section 13.NOTE 3An explosible dust when dispersed in air is capable of propagating
31、a deflagration, which could cause a flash fire or explosion depending onthe level of confinement.3.2.11 ignition delay time, tdexperimental parameter defined as the time interval between the initiation of the dust dispersionprocedure (the time at which the dispersion air starts to enter the chamber)
32、 in an experimental apparatus and the activation of theignition source (see Fig. 1). The ignition delay time characterizes the turbulence level prevailing at ignition under the defined testconditions.3.2.12 pressure ratio (PR), nPR = (Pex,aPignitor)/PignitionNOTE 4When testing in the Siwek 20-L vess
33、el (see Appendix X1) PR may be calculated using the corrected explosion pressure, n PR = (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 af
34、ter a specified delay time by an ignition source located 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.
35、5.2 The data developed by this test method may be used 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 an
36、d are not to beconsidered intrinsic material constants.5.4 For hard-to-ignite dusts with low KSt-values, a very discrepancies have been observed between tests in 20-L and 1-m3chambers. A strong ignitor may overdrive a 20-L chamber, as discussed in Test Method E1515 and RefRefs (11-3).7 If a dust has
37、measurable (nonzero) Pmax- and KSt-values with a 5000 or 10 000-J ignitor but not with a 2500-J ignitor in a 20-L chamber, thismay be an overdriven system. In this case, it is recommended that the dust be tested with a 10 000-J ignitor in a larger chambersuch as a 1-m3 chamber to determine if it is
38、actually explosible.NOTE 5Ref (2) concluded that dusts with KSt-values below 45 bar m/s when measured in a 20-L chamber with a 10 000-J ignitor, may not beexplosible when tested in a 1-m3 chamber with a 10 000-J ignitor. Ref (2) and unpublished testing has also shown that in some cases the KSt-value
39、smeasured in the 20-L chamber can be lower than those measured in the 1-m3 chamber. Refs (1) and (3) found that for some dusts, it was necessary touse lower ignition energy in the 20-L chamber in order to match MEC or MIC test data in a 1-m3 chamber. If a dust has measurable (nonzero) Pmax-and KSt-v
40、alues with a 5000 or 10 000-J ignitor when tested in a 20-L chamber but no measurable Pmax- and KSt-values with tests conducted using anignition source less than or equal to 2500 J, it may be helpful to test the material in a larger chamber such as a 1-m3 chamber using at least a 10 000-Jignition so
41、urce to further characterize the materials explosibility in dust cloud form.7 The boldface numbers in parentheses refer to a list of references at the end of this standard.E1226 12a76. Interferences6.1 In certain industrial situations where extreme levels of turbulence may be encountered, such as th
42、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
43、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
44、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
45、 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
46、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
47、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
48、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
49、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 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
