1、Designation: E1226 10Standard 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 parentheses
2、 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. The methods
3、 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. its “explosibility.”Knowledge that a dust may be explosible if dispersed as a dust cloud is important in the conduct ofa process hazard safety review. Contained herei
4、n is a screening test procedure for the purpose ofdetermining 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, are useful in the design of explosionprev
5、ention 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 providestandard test methods for characterizing the “explosibility” ofdust clouds in two ways, first by determi
6、ning if a dust is“explosible,” meaning a cloud of dust dispersed in air iscapable of propagating a deflagration; or, if explosible, deter-mining the degree of “explosibility,” meaning the potentialexplosion hazard of a dust cloud as characterized by the dustexplosibility parameters, maximum explosio
7、n pressure, Pmax;maximum rate of pressure rise, (dP/dt)max; and explosibilityindex, KSt.1.2 Limitations. Results obtained by the application of themethods of this standard pertain only to certain combustioncharacteristics of dispersed dust clouds. No inference should bedrawn from such results relati
8、ng to the combustion character-istics of dusts in other forms or conditions (e.g., ignitiontemperature or spark ignition energy of dust clouds, ignitionproperties of dust layers on hot surfaces, ignition of bulk dustin heated environments, etc.)1.3 Use. It is intended that results obtained by applic
9、ation ofthis test be used as elements of an explosion risk assessmentthat takes into account other pertinent risk factors; and in thespecification of explosion prevention systems (see, for exampleNFPA 68, NFPA 69, and NFPA 654) when used in conjunctionwith approved or recognized design methods by th
10、ose skilledin the art.NOTE 1Historically, the evaluation of the deflagration parameters ofmaximum pressure and maximum rate of pressure rise has been doneusing a 1.2-L Hartmann Apparatus. Test Method E789, which describesthis method, has been withdrawn. The use of data obtained from the testmethod i
11、n the design of explosion protection systems is not recommended.1.4 The values stated 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
12、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 Documents2.1 ASTM Standards:2D3173 Test Method for Moisture in the Analysis Sample ofCoal and CokeD3175 Test Meth
13、od for Volatile Matter in the AnalysisSample of Coal and Coke1This test method is under the jurisdiction of ASTM Committee E27 on HazardPotential of Chemicals and is the direct responsibility of Subcommittee E27.05 onExplosibility and Ignitability of Dust Clouds.Current edition approved Jan. 1, 2010
14、. Published March 2010. Originallyapproved in 1988. Last previous edition approved in 2009 as E1226 09. DOI:10.1520/E1226-09.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information,
15、refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.E789 Test Method for Dust Explosions in a 1.2-Litre ClosedCylindrical Vessel3E1445 Terminology Relating to Hazard Potenti
16、al of Chemi-calsE1515 Test Method for Minimum Explosible Concentrationof Combustible Dusts2.2 NFPA Publication:4NFPA68 Standard on Explosion Protection By DeflagrationVentingNFPA 69 Standard on Explosion Prevention SystemsNFPA 654 Standard for the Prevention of Fire and DustExplosions from the Manuf
17、acturing, Processing, and Han-dling of Combustible Particulate Solids2.3 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 For determination of
18、terms relating to hazard potentialof chemicals see Terminology E1445.3.2 Definitions of Terms Specific to This Standard:3.2.1 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).3.2.2 Pmaxthe
19、maximum pressure (above pressure in thevessel 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 Fig. 2). It is reported in bar.3.2.3 (dP/dt)exthe maximum
20、 rate of pressure rise duringthe course of a single deflagration test (see Fig. 1).3.2.4 (dP/dt)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 l
21、arge range of concen-trations (see Fig. 2). It is reported in bar/s.NOTE 2Recorder tracings of pressure (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 ra
22、nge of concentrations as shown in Fig. 2.3.2.5 deflagration index, KStmaximum dP/dt normalizedto 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,3Withdrawn. The
23、last approved version of this historical standard is referencedon www.astm.org.4Available from National Fire Protection Association (NFPA), 1 BatterymarchPark, Quincy, MA 02169-7471, http:/www.nfpa.org.5Available from Beuth Verlag, D-1000 Berlin, Federal Republic of Germany orAmerican National Stand
24、ards Institute (ANSI), 25 W. 43rd St., 4th Floor, NewYork,NY 10036, http:/www.ansi.org.6Available from International Organization for Standardization (ISO), 1, ch. dela Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http:/www.iso.ch. or fromAvailable fromAmerican National Standards I
25、nstitute (ANSI),25 W. 43rd St., 4th Floor, 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-LChamberFIG. 2 Pmaxand (dP/dt)maxas a Function of Concentration for aTypical Dust in a 20-L Cha
26、mberE1226 102V = volume, m3, andKSt= bar m/s.3.2.6 ignition delay time, tdexperimental parameter de-fined as the time interval 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 th
27、e ignition source (see Fig. 1). The ignition delaytime characterizes the turbulence level prevailing at ignitionunder the defined test conditions.3.2.7 Pressure Ratio (PR), nPR=(Pex,aDPignitor)/Pignition4. Summary of Test Method4.1 A dust cloud is formed in a closed combustion chamberby an introduct
28、ion 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 pressure time curve is recorded on a suitable pieceof equipment.5. Significance and Use5.1 This test method provides a pr
29、ocedure for performinglaboratory tests to evaluate deflagration parameters of dusts.5.2 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 testi
30、ng technique are spe-cific 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 inE1515 and Ref 2. If a dust has measurable (nonzero) Pmax- a
31、ndKSt-values with a 5000 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. Interfer
32、ences6.1 In certain industrial 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 us
33、e ofthe deflagration indices 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 approximatel
34、y1:1) in shape.7.2 The 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
35、thathave been found suitable 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 i
36、ts combustion products 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 havi
37、ng adequate ventilation.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
38、 source, safetyin handling 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 regulatio
39、ns for the pro-curement, 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 groun
40、ding procedures must be 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
41、 be designed and fabricated 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 p
42、urposes because the character 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 locatio
43、n in aprocessing system, 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.7MNL 32 ASTM Manual on Test Sieving Methods is available from ASTMHeadquarters,
44、 100 Barr Harbor Drive, W. Conshohocken, PA 19428.E1226 103NOTE 3The operator should consider the thermal stability of the dustduring any grinding or pulverizing. In sieving the material, the operatormust verify that there is no selective separation of components in a dustthat is not a pure substanc
45、e.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 wide range of particle sizes or have a well-defined specificmoisture content, materials consisting of a mixture of chemicals may beselectively
46、separated on sieves and certain fibrous materials which maynot pass through a relatively coarse screen may produce dust deflagra-tions. When a material is tested in the as-received state, it should berecognized that the test results may not represent the most severe dustdeflagration possible. Any pr
47、ocess 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 test sample should notexceed 5 % in order to avoid test results of a given dust beingnoticeably influenced.NOTE 5There is no single method f
48、or determining the moisturecontent or for drying a sample. ASTM lists many methods for moisturedetermination in the Annual Book of ASTM Standards. Sample drying isequally complex due to the presence of volatiles, lack of or varyingporosity (see Test Methods D3173 and D3175), and sensitivity of thesa
49、mple to heat. Therefore, each must be dried in a manner that will notmodify or destroy the integrity of the sample. Hygroscopic materials mustbe desiccated.10. 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 6184/1 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 wor
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