ASTM D6796-02

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D 6796 – 02
Standard Practice for
Production of Coal, Coke and Coal Combustion Samples for
Interlaboratory Studies
This standard is issued under the fixed designation D6796; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope Development of Reference Materials
1.1 This guide describes the essential activities that are
3. Terminology
required to produce samples for interlaboratory studies.
3.1 Definitions—For definitions of terms used in this prac-
1.2 The suitability of a particular interlaboratory sample
tice, refer to Terminology D121.
developed using this guide will depend on the tests being
made.
4. Summary of Practice
1.3 This standard does not purport to address all of the
4.1 Test samples of adequately defined composition and
safety concerns, if any, associated with its use. It is the
homogeneity are required for interlaboratory studies. These
responsibility of the user of this standard to establish appro-
samples should be typical in all respects to the samples for
priate safety and health practices and determine the applica-
which the test method is applicable.
bility of regulatory limitations prior to use.
4.1.1 Thesampleshouldbeofsufficientquantitytoperform
2. Referenced Documents all necessary tests and replicates. Guidelines specifying mini-
mum quantities are given in Practice D2013.
2.1 ASTM Standards:
4.1.2 The top size must be consistent for the test being run.
D121 Terminology of Coal and Coke
4.2 Differences in results due to the homogeneity or oxida-
D346 Practice for Collection and Preparation of Coke
tion,orboth,ofthetestsampleshouldbeminimalwithrespect
Samples for Laboratory Analysis
2 to other errors.
D2013 Practice for Preparing Coal Samples for Analysis
D2234 Practice for Collection of a Gross Sample of Coal
5. Significance and Use
D2492 Test Methods for Forms of Sulfur in Coal
5.1 Theobjectiveofthispracticeistoprovideguidelinesfor
D2961 Test Method for Single Stage Total Moisture Less
the preparation of samples for interlaboratory studies to evalu-
than 15 % in Coal Reduced to 2.36-mm (No. 8 Sieve)
2 ate new test methods or for quality control purposes.
Topsize
5.2 These samples prepared using these guidelines may be
D3172 Practice for ProximateAnalysis of Coal and Coke
used for the testing of the precision and bias mandatory for
D3173 TestMethodforMoistureintheAnalysisSampleof
ASTM test methods. Such an evaluation is necessary to
Coal and Coke
2 provide guidance to the user as to the reliability of measure-
D3302 Test Method for Total Moisture in Coal
ments that can be expected by its use. The statements are
D4596 Practice for Collection of Channel Samples of Coal
2 developed on the basis of user experience (ordinarily through
in the Mine
interlaboratory studies) with the test method.
D5142 Test Methods for the Proximate Analysis of Coal
2 5.3 The availability of appropriate samples is a key require-
and Coke by Instrumental Procedures
ment for interlaboratory studies.
D5263 Test Method for Determining the Relative Degree
2 5.4 The homogeneity of the sample produced for interlabo-
of Oxidation in Bituminous Coal by Alkali Extraction
3 ratorystudiesmustbesmallenoughsothatthevariancecaused
E178 Practice for Dealing with Outlying Observations
by the sample is small compared to the variance of the test
E691 Practice for Conductiing an Interlaboratory Study to
3 being performed.
Determine the Precision of a Test Method
E826 Practice for Testing Homogeneity of Materials for
6. Sample Selection and Preparation
6.1 Collect samples using Practice D2234, Practice D4596
for coal, or D346 for coke. Coal combustion products should
This practice is under the jurisdiction of ASTM Committee D05 on Coal and
besampledinamannertoprovidearepresentativesamplefree
CokeandisthedirectresponsibilityofSubcommitteeD05.30onQualityAssurance.
Current edition approved April 10, 2002. Published July 2002.
Annual Book of ASTM Standards, Vol 05.06
3 4
Annual Book of ASTM Standards, Vol 14.02. Annual Book of ASTM Standards, Vol 03.05
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 6796
from contamination. The sample should be typical of a certain 7.2 Test samples must be sufficiently homogeneous to
class of samples (for example, Eastern U.S. bituminous coal) evaluate the test method.The degree of homogeneity is related
or a certain value for a component (such as coals with two to the size of the sample analyzed. Hence the minimum size of
percentsulfur),orboth,sothatappropriatediversityofsamples a sample meeting a specified homogeneity must be stated, and
can be identified for interlaboratory studies. See Note 1. this must be equal to or smaller than the size of the sample
specified in the test method. Also, different tests may require
6.2 Grind samples to the proper size required by the test
different sample sizes to achieve homogeneity. Tests for
method and properly homogenize and split. Prepare samples
homogeneity should be made. An acceptable method for
using Practice D2013. Some coal combustion products may
measuring homogeneity is given in Appendix X1.
not require grinding, but tests should be run to determine if
further grinding is necessary. 7.3 The uncertainties in homogeneity, moisture, or sample
composition, or a combination thereof, should not exceed one
6.3 Both single-laboratory precision and between operator-
laboratory precision should be evaluated. Material of adequate third of the measurement uncertainties they are expected to
evaluate. When this specification is met, sample uncertainties
homogeneity but of uncertain composition may be used to
determine precision of a given test method. make a negligible contribution to the variance of the test
results. While replicate samples may be used in practical
NOTE 1—The use of materials of demonstrated adequate homogeneity
analysistoaverageoutsamplevariations,thisisnotfeasiblein
and known value for the test enables evaluation of the precision and bias
the case of samples for Interlaboratory Studies; hence, homo-
of a test method. Materials of known value for the test are required to
geneity should be attained as far as possible.
identify biases. Consensus values obtained as the result of interlaboratory
studies are not adequate to permit quantitative evaluation of biases,
7.4 Samples not meeting the homogeneity requirements
although they may show that such exist.
above for a given test should not be used in interlaboratory
studies unless they are re-mixed (all samples must be recom-
6.4 Usesixormorematerialsforeachinterlaboratorystudy.
bined and the entire sample rehomogenized, see 6.2) and
See Notes 1-3.
retested. In some cases, samples that are inhomogeneous for
6.5 Eachlaboratoryshallreceiveitsownsampleandatleast
one test may be homogeneous for other tests.
one sample shall be archived by the interlaboratory study
7.5 Top size of the sample must be consistent with required
coordinator.
top size or reduced to the appropriate size.
6.6 The bulk sample should be available in sufficient quan-
7.6 Sample stability may be determined. See Note 4.
tityfortherequirementsoftheinterlaboratorystudy,totestfor
7.6.1 Moisture—For most tests moisture should be deter-
homogeneity and to permit further examination by other
techniques. mined and compared to other results and calculated to a
common basis.
6.7 Sample preparation and distribution should provide
enough material and time so that laboratories can perform test 7.6.2 Oxidation—Coals (particularly those of low rank)
runs on new or unfamiliar methods. This is very important
storedforalongperiodoftimemaybecomeoxidized.Ifpyrite
because only laboratories that are thoroughly familiar and becomes oxidized it may affect forms of sulfur determinations
experienced with the procedure can be considered qualified to
(see Test Methods D2492). Bituminous coals are generally
participate in the interlaboratory study. stable for long periods of time but the degree of oxidation of
6.8 Sample stability (see 7.6), storage and future accessibil- bituminous coals can be determined using Test Method
D5263.
ity should be considered.
NOTE 2—Practice E691 paragraph 10.2.2 states, “An interlaboratory
8. Sample Storage and Preservation
study of a test method should include at least three materials, and for
development of broadly applicable precision statements, six or more
8.1 Samples should be stored in such a way to maintain
materials should be included in the study.” Because of the peculiarities of
sample stability for the characteristics being measured. See
different ranks of coal, more than the minimum six materials are needed
Note 4.
to develop precision statements applicable to all coal types. Under no
8.1.1 Changes of values in ultimate analysis should be less
circumstances should the final statement of precision of a test method be
than 1% over a 10 year period.
based on acceptable test results for each material from fewer than 6
laboratories.
8.1.2 Moisture should be determined by an appropriate
NOTE 3—In preparing an interlaboratory sample, the range of values of
method (D3172, D3173, D5142, D3302, or D2961) prior to
the property being measured should be considered, the ranks of coal to
each analysis. It should not be assumed that moisture content
which the method will be applied, the difficulty and expense of preparing
will remain constant from day to day especially for low rank
anddistributingsamples,thelengthoftimeandexpenseinperformingthe
coals.
test and the commercial or legal need for reliable estimates of precision
8.1.3 Exceptformoisture,thelargestabsolutedifferencesin
when choosing the number of materials to be used.
parametervaluechangesarelikelytobeforpercentcarbondue
7. Determining the Suitability of the Sample for the Test
to oxidation.
Method
8.1.4 For less stable coals or coals with high moisture
contents, or both, more aggressive storage or preservation
7.1 After the sample has been prepared, or if a previously
procedures may be employed. See Note 5.
prepared sample is to be used for tests other than for what it
was originally prepared, the homogeneity of the sample must 8.2 Samples may be conditioned (preoxidized) prior to
be determined. splitting and bottling. See Appendix X2.
D 6796
8.2.1 Samples may be stored under nitrogen or argon to 9. Record Keeping
minimizeoxidation.Nitrogenischeaperbutargonislesslikely
9.1 Characteristics of the sample should be recorded. At a
to react with coal components.
minimumtherank,percentash,topsize,approximatemoisture
8.2.2 Samples may be refrigerated to minimize oxidation.
content, special handling comments, amount of sample avail-
Samples should be maintained at about 4°C. Care must be
able and original purpose for which the standard was collected
taken to minimize changes in moisture. It is not recommended
shall be recorded. Sample location, sample type (run of mine;
thatsamplesbefrozenasthismightchangetoporestructureof
D121, channel sample; D4596, etc). Maintain all results with
the coal.
the samples until they are published, at which time only the
8.2.3 Depending on the characteristics of the coal to be
reference need be maintained.
measured, high moisture coals may be stored in water.
9.2 Recordwhenthesamplewascollected,recordwhenthe
NOTE 4—Storing samples in darkness or brown bottles can reduce
sample was prepared, and record how the sample has been
photochemical changes. Air-dried relatively stable-low moisture coals,
maintained.
coke and stable combustion products can be stored in tightly sealed glass
9.3 A list of samples currently available with the informa-
or plastic containers at room temperature for long periods of time without
tion listed in 8.1 and 8.2 should be accessible to interested
significant change of most coal characteristics.
parties who may wish to use them for interlaboratory studies.
NOTE 5—Lower rank coals (subituminous and lignite) generally have
high moisture content and oxidize rapidly. This oxidation may continue
formonthsbutwillslowwithtime.Moisturevaluesinthesesamplesmay
10. Keywords
depend on the time the sample is taken and the relative humidity of the
10.1 ash; coal; coke; combustion residue; homogeneity;
laboratory and may change within seconds after the sample is removed
from the bottle and over a longer period of time within the bottle. laboratory; moisture; oxidation; quality control
APPENDIXES
(Nonmandatory Information)
X1. TEST FOR HOMOGENEITY
X1.1 Test for homogeneity shall be conducted by a single Warning—Table A1 included herein is for example, only.
laboratory in a manner similar to that given in Practice E826 Use the more complete table in when actually using this test
prior to sample distribution. procedure.
X1.1.5 Whenever possible at least 4 separate sub-samples
X1.1.1 Conduct all tests by the best available procedure
taken from each container and labeled with the container
under optimum conditions. Preferably a method with a known
number and sub- sample number (that is, 02-1 for container 02
precision and bias shall be used.
sub-sample 1). All sub-samples with the same extension (for
X1.1.2 If the samples have been split into less than 15
example, XX-1) shall be determined together as a sample set
laboratory samples, sub-samples from each laboratory sample
with appropriate standards and reference materials.
shall be measured for the test of interest.
X1.1.6 Examine the data and discard any values that have
X1.1.2.1 Whenever possible the test portions should be
been determined to be outliers according to Practice E178.
takenonlyafterthelaboratorysamplesisrolledinitscontainer
(Seewarningnotebelow.)Ifoutliersoccur,repeatthecomplete
at least 5 turns followed by inverting the sample 5 times.
test, as provisions are not made for missing data in the
(1) This process should be repeated at least 3 times.
mathematical treatment.
(2) A sample can then be taken from the top.
Warning—The use of Practice E178 dealing with outliers
X1.1.2.2 The steps in X1.1.2.1 should be repeated for all
should be done with extreme care to ensure that values are not
subsequent test portions even if they are taken from the same
discarded that may be valid for the analysis.
container.
X1.1.7 When a test is complete, data should be tabulated
X1.1.3 If the number of containers is so large that test
according to Table X1.2. Data may be used in its raw form or
portions from each container cannot be measured, a minimum
normalized to a reference mate
...