1、Designation: D 6796 02 (Reapproved 2008)Standard Practice forProduction of Coal, Coke and Coal Combustion Samples forInterlaboratory Studies1This standard is issued under the fixed designation D 6796; the number immediately following the designation indicates the year oforiginal adoption or, in the
2、case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice describes the essential activities that arerequired to produce samples fo
3、r interlaboratory studies.1.2 The suitability of a particular interlaboratory sampledeveloped using this guide will depend on the tests beingmade.1.3 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 stan
4、dard 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:2D 121 Terminology of Coal and CokeD 346 Practice for Collection and Preparation of CokeSamples for Laboratory AnalysisD 2013 P
5、ractice for Preparing Coal Samples for AnalysisD 2234/D 2234M Practice for Collection of a Gross Sampleof CoalD 2492 Test Method for Forms of Sulfur in CoalD 2961 Test Method for Single-Stage Total Moisture Lessthan 15 % in Coal Reduced to 2.36-mm (No. 8 Sieve)TopsizeD 3172 Practice for Proximate An
6、alysis of Coal and CokeD 3173 Test Method for Moisture in theAnalysis Sample ofCoal and CokeD 3302 Test Method for Total Moisture in CoalD 4596 Practice for Collection of Channel Samples of Coalin a MineD 5142 Test Methods for Proximate Analysis of the Analy-sis Sample of Coal and Coke by Instrument
7、al ProceduresD 5263 Test Method for Determining the Relative Degreeof Oxidation in Bituminous Coal by Alkali ExtractionE 178 Practice for Dealing With Outlying ObservationsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE 826 Practice for Testing Homo
8、geneity of Materials forDevelopment of Reference Materials33. Terminology3.1 DefinitionsFor definitions of terms used in this prac-tice, refer to Terminology D 121.4. Summary of Practice4.1 Test samples of adequately defined composition andhomogeneity are required for interlaboratory studies. Theses
9、amples should be typical in all respects to the samples forwhich the test method is applicable.4.1.1 The sample should be of sufficient quantity to performall necessary tests and replicates. Guidelines specifying mini-mum quantities are given in Practice D 2013.4.1.2 The top size must be consistent
10、for the test being run.4.2 Differences in results due to the homogeneity or oxida-tion, or both, of the test sample should be minimal with respectto other errors.5. Significance and Use5.1 The objective of this practice is to provide guidelines forthe preparation of samples for interlaboratory studi
11、es to evalu-ate new test methods or for quality control purposes.5.2 These samples prepared using these guidelines may beused for the testing of the precision and bias mandatory forASTM test methods. Such an evaluation is necessary toprovide guidance to the user as to the reliability of measure-ment
12、s that can be expected by its use. The statements aredeveloped on the basis of user experience (ordinarily throughinterlaboratory studies) with the test method.5.3 The availability of appropriate samples is a key require-ment for interlaboratory studies.5.4 The homogeneity of the sample produced for
13、 interlabo-ratory studies must be small enough so that the variance causedby the sample is small compared to the variance of the testbeing performed.1This practice is under the jurisdiction of ASTM Committee D05 on Coal andCoke and is the direct responsibility of Subcommittee D05.30 on QualityAssura
14、nce.Current edition approved Feb. 1, 2008. Published March 2008. Originallyapproved in 2002. Last previous edition approved in 2002 as D 679602.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards v
15、olume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6. Sample Selection and Preparation6.1 Collect samples using Practice D 2234, Practice D 45
16、96for coal, or D 346 for coke. Coal combustion products shouldbe sampled in a manner to provide a representative sample freefrom contamination. The sample should be typical of a certainclass of samples (for example, Eastern U.S. bituminous coal)or a certain value for a component (such as coals with
17、twopercent sulfur), or both, so that appropriate diversity of samplescan be identified for interlaboratory studies. See Note 1.6.2 Grind samples to the proper size required by the testmethod and properly homogenize and split. Prepare samplesusing Practice D 2013. Some coal combustion products maynot
18、 require grinding, but tests should be run to determine iffurther grinding is necessary.6.3 Both single-laboratory precision and between operator-laboratory precision should be evaluated. Material of adequatehomogeneity but of uncertain composition may be used todetermine precision of a given test m
19、ethod.NOTE 1The use of materials of demonstrated adequate homogeneityand known value for the test enables evaluation of the precision and biasof a test method. Materials of known value for the test are required toidentify biases. Consensus values obtained as the result of interlaboratorystudies are
20、not adequate to permit quantitative evaluation of biases,although they may show that such exist.6.4 Use six or more materials for each interlaboratory study.See Notes 1-3.6.5 Each laboratory shall receive its own sample and at leastone sample shall be archived by the interlaboratory studycoordinator
21、.6.6 The bulk sample should be available in sufficient quan-tity for the requirements of the interlaboratory study, to test forhomogeneity and to permit further examination by othertechniques.6.7 Sample preparation and distribution should provideenough material and time so that laboratories can perf
22、orm testruns on new or unfamiliar methods. This is very importantbecause only laboratories that are thoroughly familiar andexperienced with the procedure can be considered qualified toparticipate in the interlaboratory study.6.8 Sample stability (see 7.6), storage and future accessibil-ity should be
23、 considered.NOTE 2Practice E 691 paragraph 10.2.2 states, “An interlaboratorystudy of a test method should include at least three materials, and fordevelopment of broadly applicable precision statements, six or morematerials should be included in the study.” Because of the peculiarities ofdifferent
24、ranks of coal, more than the minimum six materials are neededto develop precision statements applicable to all coal types. Under nocircumstances should the final statement of precision of a test method bebased on acceptable test results for each material from fewer than 6laboratories.NOTE 3In prepar
25、ing an interlaboratory sample, the range of values ofthe property being measured should be considered, the ranks of coal towhich the method will be applied, the difficulty and expense of preparingand distributing samples, the length of time and expense in performing thetest and the commercial or leg
26、al need for reliable estimates of precisionwhen choosing the number of materials to be used.7. Determining the Suitability of the Sample for the TestMethod7.1 After the sample has been prepared, or if a previouslyprepared sample is to be used for tests other than for what itwas originally prepared,
27、the homogeneity of the sample mustbe determined.7.2 Test samples must be sufficiently homogeneous toevaluate the test method. The degree of homogeneity is relatedto the size of the sample analyzed. Hence the minimum size ofa sample meeting a specified homogeneity must be stated, andthis must be equa
28、l to or smaller than the size of the samplespecified in the test method. Also, different tests may requiredifferent sample sizes to achieve homogeneity. Tests forhomogeneity should be made. An acceptable method formeasuring homogeneity is given in Appendix X1.7.3 The uncertainties in homogeneity, mo
29、isture, or samplecomposition, or a combination thereof, should not exceed onethird of the measurement uncertainties they are expected toevaluate. When this specification is met, sample uncertaintiesmake a negligible contribution to the variance of the testresults. While replicate samples may be used
30、 in practicalanalysis to average out sample variations, this is not feasible inthe case of samples for Interlaboratory Studies; hence, homo-geneity should be attained as far as possible.7.4 Samples not meeting the homogeneity requirementsabove for a given test should not be used in interlaboratoryst
31、udies unless they are re-mixed (all samples must be recom-bined and the entire sample rehomogenized, see 6.2) andretested. In some cases, samples that are inhomogeneous forone test may be homogeneous for other tests.7.5 Top size of the sample must be consistent with requiredtop size or reduced to th
32、e appropriate size.7.6 Sample stability may be determined. See Note 4.7.6.1 MoistureFor most tests moisture should be deter-mined and compared to other results and calculated to acommon basis.7.6.2 OxidationCoals (particularly those of low rank)stored for a long period of time may become oxidized. I
33、f pyritebecomes oxidized it may affect forms of sulfur determinations(see Test Methods D 2492). Bituminous coals are generallystable for long periods of time but the degree of oxidation ofbituminous coals can be determined using Test MethodD 5263.8. Sample Storage and Preservation8.1 Samples should
34、be stored in such a way to maintainsample stability for the characteristics being measured. SeeNote 4.8.1.1 Changes of values in ultimate analysis should be lessthan 1 % over a 10 year period.8.1.2 Moisture should be determined by an appropriatemethod (D 3172, D 3173, D 5142, D 3302,orD 2961) prior
35、toeach analysis. It should not be assumed that moisture contentwill remain constant from day to day especially for low rankcoals.8.1.3 Except for moisture, the largest absolute differences inparameter value changes are likely to be for percent carbon dueto oxidation.D 6796 02 (2008)28.1.4 For less s
36、table coals or coals with high moisturecontents, or both, more aggressive storage or preservationprocedures may be employed. See Note 5.8.2 Samples may be conditioned (preoxidized) prior tosplitting and bottling. See Appendix X2.8.2.1 Samples may be stored under nitrogen or argon tominimize oxidatio
37、n. Nitrogen is cheaper but argon is less likelyto react with coal components.8.2.2 Samples may be refrigerated to minimize oxidation.Samples should be maintained at about 4C. Care must betaken to minimize changes in moisture. It is not recommendedthat samples be frozen as this might change to pore s
38、tructure ofthe coal.8.2.3 Depending on the characteristics of the coal to bemeasured, high moisture coals may be stored in water.NOTE 4Storing samples in darkness or brown bottles can reducephotochemical changes. Air-dried relatively stable-low moisture coals,coke and stable combustion products can
39、be stored in tightly sealed glassor plastic containers at room temperature for long periods of time withoutsignificant change of most coal characteristics.NOTE 5Lower rank coals (subituminous and lignite) generally havehigh moisture content and oxidize rapidly. This oxidation may continuefor months
40、but will slow with time. Moisture values in these samples maydepend on the time the sample is taken and the relative humidity of thelaboratory and may change within seconds after the sample is removedfrom the bottle and over a longer period of time within the bottle.9. Record Keeping9.1 Characterist
41、ics of the sample should be recorded. At aminimum the rank, percent ash, top size, approximate moisturecontent, special handling comments, amount of sample avail-able and original purpose for which the standard was collectedshall be recorded. Sample location, sample type (run of mine;D 121, channel
42、sample; D 4596, etc). Maintain all results withthe samples until they are published, at which time only thereference need be maintained.9.2 Record when the sample was collected, record when thesample was prepared, and record how the sample has beenmaintained.9.3 A list of samples currently available
43、 with the informa-tion listed in 8.1 and 8.2 should be accessible to interestedparties who may wish to use them for interlaboratory studies.10. Keywords10.1 ash; coal; coke; combustion residue; homogeneity;laboratory; moisture; oxidation; quality controlAPPENDIXES(Nonmandatory Information)X1. TEST F
44、OR HOMOGENEITYX1.1 Test for homogeneity shall be conducted by a singlelaboratory in a manner similar to that given in Practice E 826prior to sample distribution.X1.1.1 Conduct all tests by the best available procedureunder optimum conditions. Preferably a method with a knownprecision and bias shall
45、be used.X1.1.2 If the samples have been split into less than 15laboratory samples, sub-samples from each laboratory sampleshall be measured for the test of interest.X1.1.2.1 Whenever possible the test portions should betaken only after the laboratory samples is rolled in its containerat least 5 turn
46、s followed by inverting the sample 5 times.(1) This process should be repeated at least 3 times.(2) A sample can then be taken from the top.X1.1.2.2 The steps in X1.1.2.1 should be repeated for allsubsequent test portions even if they are taken from the samecontainer.X1.1.3 If the number of containe
47、rs is so large that testportions from each container cannot be measured, a minimumof 8 % but not less than 15 should be tested for homogeneity.X1.1.4 Label all containers consecutively (that is, 01, 02,03, .c). If all sample containers will not be measured (seeX1.1.3) select the containers to be mea
48、sured as follows: Froma table of random numbers (see Table X1.1 and the Warningnote below ) pick an arbitrary starting place and select anydirection for reading the numbers provided the direction isfixed in advance and is independent of the numbers occurring.Select those containers for testing that
49、match the numbers readfrom the tables.WarningTable A1 included herein is for example, only.Use the more complete table in when actually using this testprocedure.X1.1.5 Whenever possible at least 4 separate sub-samplestaken from each container and labeled with the containernumber and sub- sample number (that is, 02-1 for container 02sub-sample 1). All sub-samples with the same extension (forexample, XX-1) shall be determined together as a sample setwith appropriate standards and reference materials.X1.1.6 Examine the data and discard any values that havebeen determined to be
