1、Designation: D 6796 02Standard 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 case of revision,
2、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 guide describes the essential activities that arerequired to produce samples for interlaboratory stu
3、dies.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 standard to establish app
4、ro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:D 121 Terminology of Coal and Coke2D 346 Practice for Collection and Preparation of CokeSamples for Laboratory Analysis2D 2013 Practice for Preparin
5、g Coal Samples for Analysis2D 2234 Practice for Collection of a Gross Sample of Coal2D 2492 Test Methods 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)Topsize2D 3172 Practice for Proximate Analysis of Coal and Coke
6、2D 3173 Test Method for Moisture in the Analysis Sample ofCoal and Coke3D 3302 Test Method for Total Moisture in Coal2D 4596 Practice for Collection of Channel Samples of Coalin the Mine2D 5142 Test Methods for the Proximate Analysis of Coaland Coke by Instrumental Procedures2D 5263 Test Method for
7、Determining the Relative Degreeof Oxidation in Bituminous Coal by Alkali Extraction2E 178 Practice for Dealing with Outlying Observations3E 691 Practice for Conductiing an Interlaboratory Study toDetermine the Precision of a Test Method3E 826 Practice for Testing Homogeneity of Materials forDevelopm
8、ent of Reference Materials43. 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. Thesesamples should be typical in all
9、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 for the test being run.4.2 Diffe
10、rences 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 studies to evalu-ate new test methods
11、 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-ments that can be expected by its us
12、e. 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 interlabo-ratory studies must b
13、e small enough so that the variance causedby the sample is small compared to the variance of the testbeing performed.6. Sample Selection and Preparation6.1 Collect samples using Practice D 2234, Practice D 4596for coal, or D 346 for coke. Coal combustion products shouldbe sampled in a manner to prov
14、ide a representative sample free1This practice is under the jurisdiction of ASTM Committee D05 on Coal andCoke and is the direct responsibility of Subcommittee D05.30 on Quality Assurance.Current edition approved April 10, 2002. Published July 2002.2Annual Book of ASTM Standards, Vol 05.063Annual Bo
15、ok of ASTM Standards, Vol 14.02.4Annual Book of ASTM Standards, Vol 03.051Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.from contamination. The sample should be typical of a certainclass of samples (for example, Eastern U.S. bitumin
16、ous coal)or a certain value for a component (such as coals with 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 sa
17、mplesusing Practice D 2013. Some coal combustion products maynot 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
18、 composition may be used todetermine precision of a given test method.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. Consen
19、sus values obtained as the result of interlaboratorystudies are 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
20、sample shall be archived by the interlaboratory studycoordinator.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 shou
21、ld provideenough material and time so that laboratories can perform 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
22、stability (see 7.6), storage and future accessibil-ity should be 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 i
23、ncluded in the study.” Because of the peculiarities ofdifferent 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
24、 for each material from fewer than 6laboratories.NOTE 3In preparing 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
25、time and expense in performing thetest and the commercial or legal 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 b
26、e used for tests other than for what itwas originally prepared, 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 meet
27、ing a specified homogeneity must be stated, andthis must be equal 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
28、is given in Appendix X1.7.3 The uncertainties in homogeneity, moisture, 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
29、variance of the testresults. While replicate samples may be used 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 requiremen
30、tsabove for a given test should not be used in interlaboratorystudies 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
31、sample must be consistent with requiredtop size or reduced to the 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
32、low rank)stored for a long period of time may become oxidized. If 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 Me
33、thodD 5263.8. Sample Storage and Preservation8.1 Samples should 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 ap
34、propriatemethod (D 3172, D 3173, D 5142, D 3302, or D 2961) prior 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 fo
35、r percent carbon dueto oxidation.8.1.4 For less stable 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.D 679628.2.1 Samples m
36、ay be stored under nitrogen or argon tominimize oxidation. 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 recommen
37、dedthat samples be frozen as this might change to pore structure 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
38、 moisture coals,coke and stable combustion products can 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
39、 oxidize rapidly. This oxidation may continuefor months 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
40、time within the bottle.9. Record Keeping9.1 Characteristics 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. S
41、ample location, sample type (run of mine;D 121, channel 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
42、beenmaintained.9.3 A list of samples currently available 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; quali
43、ty controlAPPENDIXES(Nonmandatory Information)X1. TEST FOR 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. P
44、referably a method with a knownprecision and bias shall 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 labo
45、ratory samples is rolled in its containerat least 5 turns 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
46、 from the samecontainer.X1.1.3 If the number of containers 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
47、 be measured (see7.3.3) select the containers to be measured as follows: From atable of random numbers (see Table X1.1 and the Warning notebelow ) pick an arbitrary starting place and select any directionfor reading the numbers provided the direction is fixed inadvance and is independent of the numb
48、ers occurring. Selectthose containers for testing that match the numbers read fromthe 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 an
49、d 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 outliers according to Practice E 178.(See warning note below.) If outliers occur, repeat the completetest, as provisions are not made for missing data in themathematical treatment.WarningThe use of Practice E 178 dealing with outliersshould be done
