ASTM E1515-2014 Standard Test Method for Minimum Explosible Concentration of Combustible Dusts《可燃尘埃最低爆炸浓度的标准试验方法》.pdf

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1、Designation: E1515 07E1515 14Standard Test Method forMinimum Explosible Concentration of Combustible Dusts1This standard is issued under the fixed designation E1515; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last

2、revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONThis test method describes procedures for measuring the minimum concentration of a combustibledust (dispersed in air) that

3、is capable of propagating a deflagration. The tests are made in laboratorychambers that have volumes of 20 L or larger.1. Scope1.1 This test method covers the determination of the minimum concentration of a dust-air mixture that will propagate adeflagration in a near-spherical closed vessel of 20 L

4、or greater volume.NOTE 1The minimum explosible concentration (MEC) is also referred to as the lower explosibility limit (LEL) or lean flammability limit (LFL).1.2 Data obtained from this test method provide a relative measure of the deflagration characteristics of dust clouds.1.3 This test method sh

5、ould be used to measure and describe the properties of materials in response to heat and flame undercontrolled laboratory conditions and should not be used to describe or appraise the fire hazard or fire risk of materials, products,or assemblies under actual fire conditions. However, results of this

6、 test may be used as elements of a fire risk assessment that takesinto account all of the factors that are pertinent to an assessment of the fire hazard of a particular end use.1.4 The values stated in SI units are to be regarded as the standard. No other units of measurement are included in this st

7、andard.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 to use. Specific

8、precautionary statements are given in Section 8.2. 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 CokeE681 Test Method for Concentration Limits of Flammability of C

9、hemicals (Vapors and Gases)E1226 Test Method for Explosibility of Dust Clouds2.2 CEN/CENELEC Publications:3EN 140343 Determination of Explosion Characteristics of Dust Clouds Part 3: Determination of the Lower Explosion LimitLEL of Dust Clouds3. Terminology3.1 Definitions of Terms Specific to This S

10、tandard:3.1.1 dust concentration, nthe mass of dust divided by the internal volume of the test chamber.3.1.2 (dP/dt)ex, nthe maximum rate of pressure rise during the course of a single deflagration test.1 This test method is under the jurisdiction of ASTM Committee E27 on Hazard Potential of Chemica

11、ls and is the direct responsibility of Subcommittee E27.05 onExplosibility and Ignitability of Dust Clouds.Current edition approved Oct. 1, 2007Dec. 1, 2014. Published November 2007January 2015. Originally approved in 1993. Last previous edition approved in 20032007as E1515 03a.E1515 07. DOI: 10.152

12、0/E1515-07.10.1520/E1515-14.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from European Committ

13、ee for Standardization (CEN), Avenue Marnix 17, B-1000, Brussels, Belgium, http:/www.cen.eu.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 to the previous version. Becauseit may not be technically possib

14、le 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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West

15、 Conshohocken, PA 19428-2959. United States13.1.3 minimum explosible concentration (MEC), nthe minimum concentration of a combustible dust cloud that is capable ofpropagating a deflagration through a well dispersed mixture of the dust and air under the specified conditions of test.3.1.4 Pignition, n

16、the absolute pressure at the time the ignitor is activated, see Fig. 1.3.1.5 Pignitor, nthe pressure rise in the chamber due to the ignitor by itself in air at atmospheric pressure3.1.6 Pex,a, nthe maximum explosion pressure (absolute) reached during the course of a single deflagration test (see Fig

17、s. 1and 2).3.1.7 Pm, nmaximum 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 Test Method E1226, Sections X1.8 and X1.9).3.1.7.1 DiscussionWhen testing in the Siwek 20-Lvessel (see Test Me

18、thod E1226,Appendix X1) PR may be calculated using the corrected explosionpressure:PR 5Pm 1Pignition!Pignition (1)3.1.8 pressure ratio (PR), ndefined asas:PR 5Pex,a 1Pignitor!Pignition (2)PR = (Pex,aPignitor)/Pignition.4. Summary of Test Method4.1 Adust cloud is formed in a closed combustion chamber

19、 by an introduction of the material with air.The test is normally madeat atmospheric pressure.4.2 Ignition of this dust-air mixture is then attempted after a specified delay time by an ignition source located near the centerof the chamber.4.3 The pressure time curve is recorded on a suitable piece o

20、f equipment.5. Significance and Use5.1 This test method provides a procedure for performing laboratory tests to evaluate relative deflagration parameters of dusts.5.2 The MEC as measured by this test method provides a relative measure of the concentration of a dust cloud necessary foran explosion.5.

21、3 Since the MEC as measured by this test method may vary with the uniformity of the dust dispersion, energy of the ignitor,and propagation criteria, the MEC should be considered a relative rather than absolute measurement.5.4 If too weak an ignition source is used, the measured MEC would be higher t

22、han the “true” value. This is an ignitability limitrather than a flammability limit, and the test could be described as“ underdriven.”as “underdriven.” Ideally, the ignition energy isincreased until the measured MEC is independent of ignition energy. However, at some point the ignition energy may be

23、come toostrong for the size of the test chamber, and the system becomes “overdriven.” When the ignitor flame becomes too large relativeto the chamber volume, a test could appear to result in an explosion, while it is actually just dust burning in the ignitor flame withno real propagation beyond the

24、ignitor.FIG. 1 Typical Recorder Tracings for a Weak Dust Deflagration in a 20-L Chamber, using a 2500 J IgnitorE1515 1425.5 The recommended ignition source for measuring the MEC of dusts in 20-L chambers is a 2500 or 5000 J pyrotechnicignitor.4 Measuring the MEC at both ignition energies will provid

25、e information on the possible overdriving of the system.5 Toevaluate the effect of possible overdriving in a 20-L chamber, comparison tests may also be made in a larger chamber, such as a1 m3-chamber.5.6 If a dust ignites with a 5000 J ignitor but not with a 2500 J ignitor in a 20-L chamber, this ma

26、y be an overdriven system.5In this case, it is recommended that the dust be tested with a 10 000 J ignitor in a larger chamber, such as a 1 m3-chamber, todetermine if it is actually explosible.5.7 The values obtained by this test method are specific to the sample tested (particularly the particle si

27、ze distribution) and themethod used and are not to be considered intrinsic material constants.6. Interferences6.1 Unburned dust or combustion products remaining in the chamber or disperser from a previous test may affect results. Thechamber and disperser should both be cleaned thoroughly before each

28、 test is made.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 between 1.3:1 and 0.7:1) in shape.7.2 The vessel should be designed and fabricated in accordance with theASME B

29、oiler and Pressure Vessel Code, Section VIII.6A maximum allowable working pressure (MAWP) of at least 15 bar is recommended.7.3 The apparatus must be capable of dispersing a fairly uniform dust cloud of the material.7.4 Optical dust probes, such as those described in Footnotes7,8 7 and 8, may be use

30、d to monitor the uniformity of the dustdispersion.7.5 The pressure transducer and recording equipment must have a combined response rate that is greater than the maximummeasured rate of pressure rise.7.6 An example of a chamber and specific procedures that have been found suitable are shown in Appen

31、dix X1.NOTE 2Another 20 L chamber design is described in Appendix X1 of Test Method E1226.4 The pyrotechnic ignitors are available commercially from Cesana Corp., PO Box 182, Verona, NY13478, or from Fr. Sobbe, GmbH, Beylingstrasse 59, Postfach 140128,D-4600 Dortmund-Derne, Germany.5 Cashdollar, K.

32、L., and Chatrathi, K., “Minimum Explosible Dust Concentrations Measured in 20-L and 1-m3 Chambers,” Combustion Science and Technology, Vol 87,1993, pp. 157171/171.6 Available from American Society of Mechanical Engineers (ASME), ASME International Headquarters, Three Park Ave., New York, NY 10016-59

33、90, http:/www.asme.org.7 Cashdollar, K. L., Liebman, I., and Conti, R. S., “Three Bureau of Mines Dust Probes,” RI 8542, U.S. Bureau of Mines, 1981. 1981.8 Conti, R. S., Cashdollar, K. L., and Liebman, I., “Improved Optical Dust Probe for Monitoring Dust Explosions,” Review of Scientific Instruments

34、, Vol 53, 1982, pp.311313.FIG. 2 Typical Recorder Tracings for a Moderate Dust Deflagration in a 20-L Chamber, using a 2500 J IgnitorE1515 1438. Safety Precautions8.1 Prior to handling a dust, the toxicity of the sample and its combustion products must be considered. This information isgenerally obt

35、ained from the manufacturer or supplier. Appropriate safety precautions must be taken if the material has toxic orirritating characteristics. Tests using this apparatus should be conducted in a ventilated hood or other area having adequateventilation.8.2 Before initiating a test, a physical check of

36、 all gaskets and fittings should be made to prevent leakage.8.3 If chemical ignitors are used as an ignitor source, safety in handling and use is a primary consideration. Premature ignitionby electrostatic discharge must be considered a possibility. When handling these ignitors, eye protection must

37、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.8.4 All testing should initially be conducted with small quantities of sample to prevent overpressuriz

38、ation due to high energymaterial.8.5 Explosive, highly reactive, or easily decomposed materials should not be tested unless they have been characterized by priortesting. Procedures such as the use of barricades, hoods, and personal protective equipment should be used as judgment indicates.9. Samplin

39、g, 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 32.9

40、9.2 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 m).9.3 To achieve this particle fineness (95 % minus 200 mesh), the sample may be groun

41、d or pulverized or it may be sieved.NOTE 3The operator should consider the thermal stability and the friction and impact sensitivity of the dust during any grinding or pulverizing. Insieving the material, the operator must verify that there is no selective separation of components in a dust that is

42、not a pure substance.9.4 Dust samples that are much finer than 200 mesh (75 m) may have even lower MEC values.NOTE 4It may be desirable in some cases to conduct dust deflagration tests on materials as sampled from a process because process dust streamsmay contain a wide range of particle sizes or ha

43、ve a well-defined specific moisture content. Materials consisting of a mixture of chemicals may beselectively separated on sieves and certain fibrous materials that may not pass through a relatively coarse screen may produce dust deflagrations. Whena material is tested in the as-received state, it s

44、hould be recognized that the test results may not represent the most severe dust deflagration possible. Anyprocess change resulting in a higher fraction of fines than normal or drier product than normal may increase the explosion severity.9.5 The moisture content of the test sample should not exceed

45、 5 % in order to avoid test results of a given dust being noticeablyinfluenced.NOTE 5There is no single method for determining the moisture content or for drying a sample.ASTM lists many methods for moisture determinationin the Annual Book of ASTM Standards. Sample drying is equally complex due to t

46、he presence of volatiles, lack of or varying porosity (see Test MethodsD3173 and D3175), and sensitivity of the sample to heat. Therefore, each must be dried in a manner that will not modify or destroy the integrity of thesample. Hygroscopic materials must be desiccated.10. Calibration and Standardi

47、zation10.1 Because a number of factors (uniformity of dispersion, ignition energy, sample age, etc.) can affect the test results, any testvessel design other than that listed in Appendix X1 must be standardized using dust samples whose minimum explosibleconcentrations are known. A minimum of five du

48、st samples over a range of MEC values is required. The MEC for each dust mustagree to within 610 % or 5 g/m3, whichever is larger. The comparison must be made using the same dust, ignitor energy, andchamber volume.10.2 Representative MEC data in grams per cubic metre (g/m3) for five dusts samples ar

49、e listed as follows:Bureau of Mines Fike20-L ChamberA 1 m3 ChamberB2500 J 5000 J 10 000 JBituminous coal, Pocahontas seam 120 85 .Bituminous coal, Pittsburgh seam 80 60 80Lycopodium 45 30 42Gilsonite 35 30 36Polyethylene 32 28 .9 MNL 32, Manual on testing Sieving Methods, is available from ASTM Headquarters, 100 Barr Harbor Drive, West Conshohocken, PA 19428.E1515 144A 20-L Chamber at Pittsburgh, PA. See Appendix X1 and Cashdollar, K. L. and Hertzberg, M. “20-L Explosibility Test Chamber for Dusts and Gases,” Rev. Sci.Instrum.,Review of Scien