ASTM D6796-21e1

Standard Practice for Production of Coal, Coke and Coal Combustion Samples for Interlaboratory Studies

SIGNIFICANCE AND USE
5.1 The objective of this practice is to provide guidelines for the preparation of samples for interlaboratory studies to evaluate new test methods or for quality control purposes.  
5.2 Samples prepared using these guidelines may be used for the testing of the precision and bias mandatory for ASTM test methods. Such an evaluation is necessary to provide guidance to the user as to the reliability of measurements that can be expected by its use. The statements are developed on the basis of user experience (ordinarily through interlaboratory studies) with the test method.  
5.3 The availability of appropriate samples is a key requirement for interlaboratory studies.  
5.4 The homogeneity of the sample produced for interlaboratory studies must be small enough so that the variance caused by the sample is small compared to the variance of the test being performed.
SCOPE
1.1 This practice describes the essential activities that are required to produce samples for interlaboratory studies.  
1.2 The suitability of a particular interlaboratory sample developed using this guide will depend on the tests being made.  
1.3 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Mar-2021
• ICS: 75.160.10 - Solid fuels
• Technical Committee: D05 - Coal and Coke
• Drafting Committee: D05.24 - Statistics

Relations

• Refers: ASTM D7582-24 - Standard Test Methods for Proximate Analysis of Coal and Coke by Macro Thermogravimetric Analysis
• Effective Date: 01-Apr-2024
• Refers: ASTM D121-15(2024) - Standard Terminology of Coal and Coke
• Effective Date: 01-Mar-2024
• Refers: ASTM D7582-15(2023) - Standard Test Methods for Proximate Analysis of Coal and Coke by Macro Thermogravimetric Analysis
• Effective Date: 01-Dec-2023
• Refers: ASTM D2234/D2234M-19 - Standard Practice for Collection of a Gross Sample of Coal
• Effective Date: 01-Dec-2019
• Refers: ASTM D2234/D2234M-17 - Standard Practice for Collection of a Gross Sample of Coal
• Effective Date: 15-Oct-2017
• Refers: ASTM E178-16 - Standard Practice for Dealing With Outlying Observations
• Effective Date: 01-Jun-2016
• Refers: ASTM D2234/D2234M-16 - Standard Practice for Collection of a Gross Sample of Coal
• Effective Date: 01-Mar-2016
• Refers: ASTM D121-15 - Standard Terminology of Coal and Coke
• Effective Date: 01-Sep-2015
• Refers: ASTM E691-13 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-May-2013
• Refers: ASTM E826-08(2013) - Standard Practice for Testing Homogeneity of a Metal Lot or Batch in Solid Form by Spark Atomic Emission Spectrometry
• Effective Date: 01-Apr-2013
• Refers: ASTM D3302/D3302M-12 - Standard Test Method for Total Moisture in Coal
• Effective Date: 01-Apr-2012
• Refers: ASTM D2961-11 - Standard Test Method for Single-Stage Total Moisture Less than 15% in Coal Reduced to 2.36-mm (No. 8 Sieve) Topsize
• Effective Date: 01-Nov-2011
• Refers: ASTM E691-11 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Nov-2011
• Refers: ASTM D346/D346M-11 - Standard Practice for Collection and Preparation of Coke Samples for Laboratory Analysis
• Effective Date: 01-Oct-2011
• Refers: ASTM D3173-11 - Standard Test Method for Moisture in the Analysis Sample of Coal and Coke
• Effective Date: 01-Apr-2011

Overview

ASTM D6796-21e1 is a standard practice developed by ASTM International that outlines best practices for the production of coal, coke, and coal combustion samples for interlaboratory studies. This standard serves as an essential guideline to ensure the reliability, homogeneity, and appropriate composition of samples used when evaluating new test methods or conducting quality control for coal and coke analysis. The standard plays a critical role in providing consistent and precise sample preparation, which is fundamental for obtaining comparable data across different laboratories in the coal and coke industry.

Key Topics

• Sample Preparation Guidelines: Outlines activities necessary for producing samples suitable for interlaboratory testing. Ensures that methods align with recognized reference standards.
• Homogeneity and Stability: Defines requirements for the homogeneity of samples, emphasizing that the variance due to sample differences must be minimal relative to test variance.
• Sample Handling and Storage: Recommends procedures for storing and preserving coal and coke samples to maintain their characteristics and reduce oxidation or moisture content variation.
• Quality Control and Consistency: Provides recommendations for evaluating the precision and bias of test methods using prepared samples, thus supporting the reliability of laboratory measurements.
• Documentation and Record Keeping: Details the type of information that must be recorded for each sample, including origin, characteristics, and handling history.
• Safety and Regulatory Compliance: Reminds users to observe appropriate safety, health, and environmental practices, and to comply with local regulatory requirements when following this standard.

Applications

ASTM D6796-21e1 is widely used in various scenarios within the coal, coke, and coal combustion industries:

• Development and Validation of Test Methods: Provides a uniform process for preparing samples that are critical for the validation, precision, and bias assessment of new or modified analytical procedures used on coal, coke, and combustion residues.
• Interlaboratory Studies: Enables multiple laboratories to participate in studies with consistent sample material, ensuring that inter-lab comparisons reflect actual testing variability rather than sample inconsistencies.
• Quality Assurance in Industrial Laboratories: Supports quality control processes by maintaining strict sample preparation and storage protocols, making it easier to compare results over time or across facilities.
• Regulatory Compliance and Reporting: Assists organizations in meeting international and national regulations for coal and coke testing by adhering to accepted standards for sample management.
• Sample Archiving for Retesting and Future Analysis: Recommends maintaining archived sample sets for retrospective evaluation, further research, or dispute resolution.

Related Standards

ASTM D6796-21e1 references and complements several other ASTM standards relevant to coal and coke sampling and analysis:

• ASTM D121: Terminology of Coal and Coke
• ASTM D2013/D2013M: Practice for Preparing Coal Samples for Analysis
• ASTM D2234/D2234M: Practice for Collection of a Gross Sample of Coal
• ASTM D346/D346M: Practice for Collection and Preparation of Coke Samples for Laboratory Analysis
• ASTM D4596: Practice for Collection of Channel Samples of Coal in a Mine
• ASTM D5192: Practice for Collection of Coal Samples from Core
• ASTM D7430/D7430M: Practice for Mechanical Sampling of Coal
• ASTM D3302/D3302M, D2961, D3173, D7582: Methods for Moisture Testing in Coal and Coke
• ASTM D5263: Test Method for Determining the Relative Degree of Oxidation in Bituminous Coal
• ASTM E178, E691, E826: Practices for Outlying Observations, Conducting Interlaboratory Studies, and Testing Homogeneity
• International Principles: Developed in accordance with World Trade Organization (WTO) TBT Committee principles.

By following ASTM D6796-21e1, laboratories and researchers can enhance the credibility of their analytical results, facilitate industry benchmarking, and maintain compliance with global standards on the production of coal and coke samples for interlaboratory studies.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
´1
Designation: D6796 − 21
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 (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—Editorial corrections were made to X1.1.13, X1.1.14, and X2.2.2 in June 2021.
1. Scope D2492TestMethodforFormsofSulfurinCoal(Withdrawn
2021)
1.1 This practice describes the essential activities that are
D2961PracticeforSingle-StageTotalMoistureLessthan15
required to produce samples for interlaboratory studies.
% in Coal Reduced to 2.36mm [No. 8 Sieve] Topsize
1.2 The suitability of a particular interlaboratory sample
D3173Test Method for Moisture in theAnalysis Sample of
developed using this guide will depend on the tests being
Coal and Coke
made.
D3302/D3302MTest Method for Total Moisture in Coal
D4596Practice for Collection of Channel Samples of Coal
1.3 Units—The values stated in SI units are to be regarded
asstandard.Nootherunitsofmeasurementareincludedinthis in a Mine
D5192Practice for Collection of Coal Samples from Core
standard.
D5263Test Method for Determining the Relative Degree of
1.4 This standard does not purport to address all of the
Oxidation in Bituminous Coal by Alkali Extraction
safety concerns, if any, associated with its use. It is the
D7430/D7430MPractice for Mechanical Sampling of Coal
responsibility of the user of this standard to establish appro-
D7582Test Methods for Proximate Analysis of Coal and
priate safety, health, and environmental practices and deter-
Coke by Macro Thermogravimetric Analysis
mine the applicability of regulatory limitations prior to use.
E178Practice for Dealing With Outlying Observations
1.5 This international standard was developed in accor-
E691Practice for Conducting an Interlaboratory Study to
dance with internationally recognized principles on standard-
Determine the Precision of a Test Method
ization established in the Decision on Principles for the
E826Practice for Testing Homogeneity of a Metal Lot or
Development of International Standards, Guides and Recom-
Batch in Solid Form by Spark Atomic Emission Spec-
mendations issued by the World Trade Organization Technical
trometry
Barriers to Trade (TBT) Committee.
3. Terminology
2. Referenced Documents
3.1 Definitions—For definitions of terms used in this
2.1 ASTM Standards:
practice, refer to Terminology D121.
D121Terminology of Coal and Coke
4. Summary of Practice
D346/D346MPractice for Collection and Preparation of
Coke Samples for Laboratory Analysis
4.1 Test samples of adequately defined composition and
D2013/D2013MPractice for Preparing Coal Samples for
homogeneity are required for interlaboratory studies. These
Analysis
samples should be typical in all respects to the samples for
D2234/D2234MPractice for Collection of a Gross Sample
which the test method is applicable.
of Coal
4.1.1 Thesampleshouldbeofsufficientquantitytoperform
all necessary tests and replicates. Guidelines specifying mini-
mum quantities are given in Practice D2013/D2013M.
This practice is under the jurisdiction of ASTM Committee D05 on Coal and 4.1.2 The top size must be consistent for the test being run.
Coke and is the direct responsibility of Subcommittee D05.24 on Statistics.
4.2 Differences in results due to the homogeneity or
Current edition approved April 1, 2021. Published April 2021. Originally
approved in 2002. Last previous edition approved in 2016 as D6796–16. DOI: oxidation, or both, of the test sample should be minimal with
10.1520/D6796-21E01.
respect to other errors.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on The last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D6796 − 21
5. Significance and Use 6.7 Sample preparation and distribution should provide
enough material and time so that laboratories can perform test
5.1 Theobjectiveofthispracticeistoprovideguidelinesfor
runs on new or unfamiliar methods. This is very important
the preparation of samples for interlaboratory studies to evalu-
because only laboratories that are thoroughly familiar and
ate new test methods or for quality control purposes.
experienced with the procedure can be considered qualified to
5.2 Samples prepared using these guidelines may be used
participate in the interlaboratory study.
for the testing of the precision and bias mandatory for ASTM
6.8 Sample stability (see 7.6), storage, and future accessi-
test methods. Such an evaluation is necessary to provide
bility should be considered.
guidance to the user as to the reliability of measurements that
NOTE 2—Practice E691 paragraph 10.2.2 states, “An ILS of a test
canbeexpectedbyitsuse.Thestatementsaredevelopedonthe
method should include at least three materials representing different test
levels,andfordevelopmentofbroadlyapplicableprecisionstatements,six
basis of user experience (ordinarily through interlaboratory
or more materials should be included in the study.” Because of the
studies) with the test method.
peculiarities of different ranks of coal, more than the minimum six
materialsareneededtodevelopprecisionstatementsapplicabletoallcoal
5.3 The availability of appropriate samples is a key require-
types. Under no circumstances should the final statement of precision of
ment for interlaboratory studies.
a test method be based on acceptable test results for each material from
fewer than 6 laboratories.
5.4 The homogeneity of the sample produced for interlabo-
NOTE 3—In preparing an interlaboratory sample, the range of values of
ratorystudiesmustbesmallenoughsothatthevariancecaused
the property being measured should be considered, the ranks of coal to
by the sample is small compared to the variance of the test
which the method will be applied, the difficulty and expense of preparing
being performed.
anddistributingsamples,thelengthoftimeandexpenseinperformingthe
test and the commercial or legal need for reliable estimates of precision
when choosing the number of materials to be used.
6. Sample Selection and Preparation
7. Determining the Suitability of the Sample for the Test
6.1 Collect samples using Practices D2234/D2234M,
Method
D4596, D5192, and D7430/D7430M for coal, or Practice
D346/D346M for coke. Coal combustion products should be 7.1 After the sample has been prepared, or if a previously
sampled in a manner to provide a representative sample free
prepared sample is to be used for tests other than for what it
from contamination. The sample should be typical of a certain was originally prepared, the homogeneity of the sample must
source and class of samples (for example, Eastern U.S.
be determined.
bituminous coal) or a certain value for a component (such as
7.2 Test samples must be sufficiently homogeneous to
coals with two percent sulfur), or both, so that appropriate
evaluate the test method.The degree of homogeneity is related
diversity of samples can be identified for interlaboratory
to the size of the sample analyzed. Hence the minimum size of
studies. See Note 1. To ensure diversity, verify the important
a sample meeting a specified homogeneity must be stated, and
values and the rank of coal samples through additional testing
this must be equal to or smaller than the size of the sample
prior to distribution.
specified in the test method. Also, different tests may require
different sample sizes to achieve homogeneity. Tests for
6.2 Grind samples to the proper size required by the test
homogeneity should be made. An acceptable method for
method and properly homogenize and split. Prepare samples
measuring homogeneity is given in Appendix X1.
using Practice D2013/D2013M. Some coal combustion prod-
ucts may not require grinding, but tests should be run to
7.3 The uncertainties in homogeneity, moisture, or sample
determine if further grinding is necessary.
composition, or a combination thereof, should not exceed one
third of the measurement uncertainties they are expected to
6.3 Both single-laboratory precision and between operator-
evaluate. When this specification is met, sample uncertainties
laboratory precision should be evaluated. Material of adequate
make a negligible contribution to the variance of the test
homogeneity but of uncertain composition may be used to
results. While replicate samples may be used in practical
determine precision of a given test method.
analysistoaverageoutsamplevariations,thisisnotfeasiblein
NOTE 1—The use of materials of demonstrated adequate homogeneity
the case of samples for Interlaboratory Studies; hence, homo-
and known value for the test enables evaluation of the precision and bias
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
7.4 Samples not meeting the homogeneity requirements
studies are not adequate to permit quantitative evaluation of biases,
above for a given test should not be used in interlaboratory
although they may show that such exist.
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
one test may be homogeneous for other tests.
6.5 Eachlaboratoryshallreceiveitsownsampleandatleast
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.
tity for the requirements of the interlaboratory study, to test for 7.6.1 Moisture—For most tests, moisture should be deter-
homogeneity and to permit further examination by other mined and compared to other results and calculated to a
techniques. common basis.
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D6796 − 21
7.6.2 Oxidation—Coals (particularly those of low rank) 8.2.3 Depending on the characteristics of the coal to be
storedforalongperiodoftimemaybecomeoxidized.Ifpyrite measured, high moisture coals may be stored in water.
becomes oxidized, it may affect forms of sulfur determinations
NOTE 4—Storing samples in darkness or brown bottles can reduce
photochemical changes. Air-dried relatively stable-low moisture coals,
(see Test Method D2492). Bituminous coals are generally
coke, and stable combustion products can be stored in tightly sealed glass
stable for long periods of time, but the degree of oxidation of
or plastic containers at room temperature for long periods of time without
bituminouscoalscanbedeterminedusingTestMethodD5263.
significant change of most coal characteristics.
NOTE 5—Low rank coals (subbituminous and lignite) generally have
8. Sample Storage and Preservation
high moisture content and oxidize rapidly. This oxidation may continue
formonthsbutwillslowwithtime.Moisturevaluesinthesesamplesmay
8.1 Samples should be stored in such a way to maintain
depend on the time the sample is taken and the relative humidity of the
sample stability for the characteristics being measured. See
laboratory and may change within seconds after the sample is removed
Note 4.
from the bottle and over a longer period of time within the bottle.
8.1.1 Changes of values in ultimate analysis should be less
than 1% over a 10 year period.
9. Record Keeping
8.1.2 Moisture should be determined by an appropriate
method (Test Method D3173, Test Methods D7582, Test 9.1 Characteristics of the sample should be recorded. At a
minimum, the rank, percent ash, top size, approximate mois-
Method D3302/D3302M, or Practice D2961) prior to each
analysis. It should not be assumed that moisture content will ture content, special handling comments, amount of sample
available, and original purpose for which the sample was
remain constant from day to day especially for low rank coals.
8.1.3 Exceptformoisture,thelargestabsolutedifferencesin collected shall be recorded, that is, sample location, sample
type (run of mine; Terminology D121, channel sample; Prac-
parametervaluechangesarelikelytobeforpercentcarbondue
tice D4596, etc). Maintain all results with the samples until
to oxidation.
they are published, at which time only the reference need be
8.1.4 For less stable coals or coals with high moisture
maintained.
contents, or both, more aggressive storage or preservation
procedures may be employed. See Note 5.
9.2 Recordwhenthesamplewascollected,recordwhenthe
8.2 Samples may be conditioned (preoxidized) prior to
sample was prepared, and record how the sample has been
splitting and bottling. See Appendix X2.
maintained.
8.2.1 Samples may be stored under nitrogen or argon to
9.3 A list of samples currently available with the informa-
minimizeoxidation.Nitrogenischeaperbutargonislesslikely
tion listed i
...