1、Designation: E2019 03 (Reapproved 2013)Standard Test Method forMinimum Ignition Energy of a Dust Cloud in Air1This standard is issued under the fixed designation E2019; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of la
2、st revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method determines the minimum ignitionenergy of a dust cloud in air by a high voltage spark.1.2 The Minimum Ig
3、nition Energy (MIE) of a dust-cloud isprimarily used to assess the likelihood of ignition duringprocessing and handling. The likelihood of ignition is used toevaluate the need for precautions such as explosion preventionsystems. The MIE is determined as the electrical energy storedin a capacitor whi
4、ch, when released as a high voltage spark, isjust sufficient to ignite the dust cloud at its most easily ignitableconcentration in air. The laboratory test method described inthis standard does not optimize all test variables that affectMIE. Smaller MIE values might be determined by increasingthe nu
5、mber of repetitions or optimizing the spark dischargecircuit for each dust tested.1.3 In this test method, the test equipment is calibrated usinga series of reference dusts whose MIE values lie withinestablished limits. Once the test equipment is calibrated, therelative ignition sensitivity of other
6、 dusts can be found bycomparing their MIE values with those of the reference dustsor with dusts whose ignition sensitivities are known fromexperience. X1.1 of this test method includes guidance on thesignificance of minimum ignition energy with respect toelectrostatic discharges.1.4 The values state
7、d in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 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
8、health practices and determine the applica-bility of regulatory limitations prior to use. Specific precau-tionary statements are given in Section 8.2. Referenced Documents2.1 ASTM Standards:2D3173 Test Method for Moisture in the Analysis Sample ofCoal and CokeD3175 Test Method for Volatile Matter in
9、 the AnalysisSample of Coal and CokeE582 Test Method for Minimum Ignition Energy andQuenching Distance in Gaseous MixturesE789 Test Method for Dust Explosions in a 1.2-Litre ClosedCylindrical Vessel (Withdrawn 2007)3E1226 Test Method for Explosibility of Dust CloudsE1445 Terminology Relating to Haza
10、rd Potential of Chemi-cals2.2 IEC Standards:41241-2-3, 1994 Electrical Apparatus for Use in the Presenceof Combustible Dusts, Part 2: Test Method, Section 3:Method for Determining Minimum Ignition Energy ofDust-Air Mixtures3. Terminology3.1 DefinitionsFor additional definitions, see Terminol-ogy E14
11、45.3.2 Definitions of Terms Specific to This Standard:3.2.1 spark discharge, ntransient discrete electricdischarge, which takes place between two conductors, whichare at different potentials. The discharge bridges the gapbetween the conductors in the form of a single ionizationchannel.3.2.2 minimum
12、ignition energy (MIE), nelectrical energydischarged from a capacitor, which is just sufficient to effectignition of the most easily ignitable concentration of fuel in airunder the specific test conditions.3.2.3 ignition delay time, nthe time between the onset ofdispersion of the dust sample into a c
13、loud and the activation ofthe ignition source.1This test method is under the jurisdiction of ASTM Committee E27 on HazardPotential of Chemicalsand is the direct responsibility of Subcommittee E27.05 onExplosibility and Ignitability of Dust Clouds.Current edition approved Oct. 1, 2013. Published Nove
14、mber 2013. Originallyapproved in 1999. Last previous edition approved in 2007 as E2019 03 (2007).DOI: 10.1520/E2019-03R13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, ref
15、er to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.4Available from International Electrotechnical Commission (IEC), 3 rue deVaremb, Case postale 131, CH-1211, Geneva 20, Switzerland, http:/www.iec.ch.Copyri
16、ght ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Summary of Test Method4.1 A dust cloud is formed in a laboratory chamber by anintroduction of the material with air.4.2 Ignition trials of this dust-air mixture are thenattempted, after a s
17、pecific ignition delay time, by a sparkdischarge from a charged capacitor.4.3 The stored energy discharged into the spark and theoccurrence or nonoccurrence of flame are recorded.4.4 The minimum ignition energy is sought by varying thedust concentration, the spark discharge energy and optionallythe
18、ignition delay time.4.5 Ignition is determined by visual observation of a flamepropagation away from the spark gap.5. Significance and Use5.1 This test method provides a procedure for performinglaboratory tests to determine the minimum ignition energy of adust cloud.NOTE 1For gases and vapors, see T
19、est Method E582.5.2 The data developed by this test method may be used toassess the spark ignitibility of a dust cloud. Additional guid-ance on the significance of minimum ignition energy is inX1.1.5.3 The values obtained are specific to the sample tested, themethod used and the test equipment used.
20、 The values are not tobe considered intrinsic material constants.5.4 The MIE of a dust as determined using this procedurecan be compared with the MIEs of reference dusts (using thesame procedure) to obtain the relative sensitivity of the dust tospark ignition. An understanding of the relative sensit
21、ivity tospark ignition can be used to minimize the probability ofexplosions due to spark ignition.6. Interferences6.1 Dust residue from previous tests may affect results. Thechamber must be cleaned before a new product is tested.6.2 Problems may arise due to electrical shortcircuits whenusing conduc
22、tive materials.7. Apparatus7.1 Test ApparatusAlthough a number of different testapparatuses are used in practice, they all have the followingcomponents in common: A test chamber, spark electrodes, anda spark generation circuit. Various configurations of the sparkgeneration circuits are provided in t
23、he Appendix X1. Thepurpose of the test chamber is to produce a uniform, nontur-bulent and known density dust cloud in air at the time ofignition. The clear plastic or glass Hartmann tube, typically 0.5or 1.2 L, and the 20-L sphere apparatus have been foundsuitable for this test method. These vessels
24、 are described inRefs (1-4)5and Test Methods E789 and E1226. These andother suitable chambers can be used provided that the calibra-tion requirements in 10.1 are met.7.2 Spark Generation CircuitThe Appendix describessome suitable forms of circuits, all of which shall have thefollowing characteristic
25、s:7.2.1 Electrode Material, such as tungsten, stainless steel,brass, or graphite.7.2.2 Electrode Diameter and Shape, 2 6 1 mm. Forcircuits in which high voltage is maintained across the sparkgap prior to spark breakdown, a significant fraction of theenergy stored in the capacitor may drain away as c
26、oronadischarges from sharp electrode tips prior to the spark dis-charge. This is increasingly important at low stored energies.Electrodes with rounded tips can be used to reduce coronaeffects that can occur with pointed electrodes, which may giveincorrect values of spark energy. If pointed electrode
27、s are used,corona effects should be considered carefully.7.2.3 Electrode GapThe optimum spacing is typically ofthe order of 6 mm. For certain materials at low ignition energyvalues, however, the gap spacing may need to be reduced inorder to initiate the spark. Under these circumstances, the sparkgap
28、 can be reduced and the tests carried out with the largest gappossible, but the gap should not be less than 2 mm.NOTE 2The capacitance of the electrodes and associated high voltagecables between the storage capacitor and the electrodes should be as lowas possible. It should be noted that cable capac
29、itance may be of the order40pF/m depending on its construction, which represents significantadditional stored energy at low storage capacitance and high voltage. Thestray capacitance of these components must be measured to determine ifit needs to be taken into account when calculating the stored cir
30、cuitenergy.NOTE 3Insulation resistance between electrodes should be sufficientlyhigh to prevent leakage currents prior to discharge. Typically, a minimumresistance between the electrodes of 1012 is required for a minimumignition energy of 1 mJ, and 1010 for a minimum ignition energy of 100mJ. Insula
31、tion resistance may decrease over time due to contamination ofthe surface with carbon and other materials.The resistance may be directlymeasured across the electrodes. Alternatively, a decrease may be inferredby the inability to hold constant voltage on the isolated storage capacitorfor the timescal
32、e of a test.NOTE 4Almost all electrostatic discharges in plant installations arecapacitive with negligible inductance. It has been found that for equalstored energies many dusts can be ignited more easily when a resistor oran inductance is placed in the discharge circuit to create longer durationspa
33、rks. Ideally, the MIE should correspond to circuits whose dischargeduration has been optimized for the dust in question using, for example,an inductance.8. Safety Precautions8.1 Prior to handling a test material, the toxicity of thesample and its combustion products must be considered. Thisinformati
34、on is generally obtained from the manufacturer orsupplier. Appropriate safety precautions must be taken if thematerial has toxic or irritating characteristics. MIE-tests shouldbe conducted in a ventilated hood or other area havingadequate ventilation.8.2 Before initiating a test, check and secure th
35、e apparatus,fittings and gaskets to prevent leakage.8.3 All enclosures containing electrical equipment must beconnected to a common ground.5The boldface numbers in parentheses refer to the list of references at the end ofthis standard.E2019 03 (2013)28.4 The test method should not be used with recog
36、nizedexplosives, such as gunpowder or dynamite; pyrophoric sub-stances; or, substances or mixtures of substances, which mayunder some circumstances behave in a similar manner withoutconsidering the special hazards. Where any doubt exists aboutthe existence of a hazard due to explosive properties, ex
37、pertadvice should be sought.8.5 Because the apparatus consists of a circuit with highvoltage components, adequate safeguards must be employed toprevent electrical shock to personnel.8.6 The operator should work from a protected location,such as from outside a closed fume hood, in case of vessel orel
38、ectrical failure.8.7 Care should be taken not to clean acrylic Hartmanntubes with incompatible solvents, which can lead to embrittle-ment and cracking.9. Sampling9.1 It is not practical to specify a single method of samplingdust for test purposes because the character of the material andits availabl
39、e form affect selection of the sampling procedure.9.2 Minimum ignition energy decreases with decreasingparticle size (see Fig. 1). Although tests may be run on an“as-received” sample, explosible dust clouds often consistlargely of sub-200 mesh dust, which accumulates in suspensionwhen coarser bulk p
40、owder is handled. Therefore, it is recom-mended that the test sample be at least 95 % minus 200 mesh(75 m). In general, the sample tested should be at least as fineas the dust at the location being considered, which, in somecases, may require testing of sub-325 mesh or even finer dust.9.3 To achieve
41、 this particle fineness (95 % minus 200mesh) the sample may be ground or pulverized, or it may besieved.NOTE 5The operator should consider the thermal stability of the dustduring grinding or pulverizing.NOTE 6In some cases, it may be desirable to conduct dust deflagrationtests on material as sampled
42、 from a process because process dust streamsmay contain a wide range of particle sizes or have a well-defined specificmoisture content. When a material is tested in the as-received state, itshould be recognized that the test results may not represent the mostsevere ignition hazards possible. Any pro
43、cess change resulting in a higherfraction of fines or drier product may result in a lower MIE for theproduct.NOTE 7The possible reduction of the particle size due to attrition bythe dust dispersion system of the test apparatus should be considered.NOTE 8In sieving the material, the operator must ver
44、ify that there isno selective separation of components in a dust that is not a puresubstance. Materials consisting of a mixture of chemicals may beseparated selectively on sieves and certain fibrous materials, which maynot pass through a relatively coarse screen may produce dust deflagra-tions.9.4 M
45、inimum ignition energy for some dusts increases withincreased moisture content (see Fig. 2). Dusts should be testedeither in the dry state or approximating the moisture contentunder the handling conditions of interest. “Dry” samplesshould be transported to the test laboratory in sealed containersund
46、er dry air or nitrogen, and then stored in a desiccator.Desiccants, such as phosphorus pentoxide, may be moreeffective than silica gel in removing residual moisture.NOTE 9There is no single method for determining the moisturecontent or for drying a sample. Sample drying equally is complex due tothe
47、presence of volatiles, lack of or varying porosity (see Test MethodsD3173 and D3175), and sensitivity of the sample to heat; therefore, eachmust be dried in a manner that will not modify or destroy the integrity ofthe sample. Hygroscopic materials must be desiccated.10. Calibration and Standardizati
48、on10.1 Calibration tests should be carried out on at least threedifferent reference dusts. The results shall be within thefollowing ranges (measured without inductance):FIG. 1 Correlation of Median Particle Size and MIE (5)FIG. 2 Influence of the Humidity (Water Content) of CombustibleDusts (5)E2019
49、 03 (2013)3Irganox 1010:6MIE=1to6mJAnthraquinone: MIE=1to11mJLycopodium:7MIE=10to30mJPittsburgh coal:8MIE = 30 to 140 mJ10.2 In addition to the initial calibration and standardizationprocedure, at least one standard dust should be retestedperiodically to verify that the dispersion and turbulence char-acteristics of the chamber have not changed.11. Procedure11.1 Test Description:11.1.1 Inspect equipment to be sure it is cleaned thoroughlyand in good operational condition.11.1.2 The combustible dust to be tested is dispersed in airat laboratory ambient test co
