ASTM D6543-00e1
(Guide)Standard Guide to the Evaluation of Measurements Made by On-Line Coal Analyzers
Standard Guide to the Evaluation of Measurements Made by On-Line Coal Analyzers
SCOPE
1.1 This guide provides techniques to be used for the evaluation of the measurement performance of on-line coal analyzers.
1.2 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 and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D 6543 – 00
Standard Guide to
the Evaluation of Measurements Made by On-Line Coal
Analyzers
This standard is issued under the fixed designation D 6543; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Figs. 7–10 were editorially corrected in December 2000.
1. Scope 3.1.3 Grubbs estimator, n—an estimate of the measurement
precision of an on-line analyzer (1-3).
1.1 This guide provides techniques to be used for the
3.1.4 on-line analyzer, n—an analytical tool consisting of
evaluation of the measurement performance of on-line coal
an instrument and systems, which together provide measure-
analyzers.
ments, or estimates, or both, of coal quality parameters.
1.2 This standard does not purport to address all of the
3.1.5 outlier, n—an extreme value that statistical tests
safety concerns, if any, associated with its use. It is the
indicate to be far enough from other results in a population
responsibility of the user of this standard to establish appro-
under consideration to cause suspicion that the value is not a
priate safety and health practices and determine the applica-
member of the population.
bility of regulatory limitations prior to use.
3.1.6 reference material, n—material of stable composition
2. Referenced Documents
that may be used to generate static analyzer measurements.
3.1.7 reference system, n—a measurement system used to
2.1 ASTM Standards:
measure the characteristics of a lot of coal that are also
D 121 Terminology of Coal and Coke
measuredbyanon-line-analyzer,andagainstwhichtheon-line
D 2013 Method of Preparing Coal Samples for Analysis
analyzer measurements are compared.
D 2234 Test Methods for Collection of a Gross Sample of
3.1.8 standardization, n—calibration of an instrument to a
Coal
reference material using static stability measurements.
D 4702 Guide for Inspecting Crosscut, Sweep Arm, and
3.1.9 static stability, n—an estimate of the measurement
Auger Mechanical Coal Sampling Systems for Conform-
precision of an instrument obtained on material that is not
ance with Current ASTM Standards
moving. The estimate normally is expressed as the standard
D 6518 Practice for Bias Testing Mechanical Coal Sam-
deviation and average of the measurements for a given period
pling Systems
of time.
E 177 Practice for Use of the Terms Precision and Bias in
3.1.10 synchronization error, n—an error that occurs from
ASTM Test Methods
comparing measurements made by an on-line analyzer and a
E 178 Practice for Dealing With Outlying Observations
reference system that are not measuring exactly the same lot
E 456 Terminology Relating to Quality and Statistics
because of temporal and/or spatial offsets.
3. Terminology
4. Summary of Guide
3.1 Definitions:
4.1 This guide outlines the evaluation of the measurement
3.1.1 analyzer system, n—a coal quality measurement sys-
performance of an on-line analyzer using comparative mea-
tem which includes an on-line coal analyzer and which may
surements. The comparative test uses a paired comparison of
include one or more stages of a coal-sampling system.
analysis from a reference method using ASTM sampling,
3.1.2 calibration, n—mathematical modeling of analyzer
sample preparation, and analysis methods for a lot of coal with
and comparative coal sampling and analysis data. Factors from
the analysis from the on-line analyzer for the same lot of coal.
the model are used in the on-line analyzer control software.
The data resulting from the comparative test may be evaluated
using graphical and statistical techniques outlined below.
This guide is under the jurisdiction of ASTM Committee D05 on Coal and
Coke and is the direct responsibility of Subcommittee D05.23 on Sampling.
Current edition approved April 10, 2000. Published May 2000.
2 4
Annual Book of ASTM Standards, Vol 05.06. The boldface numbers in parentheses refer to the list of references at the end of
Annual Book of ASTM Standards, Vol 14.02. this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D6543–00
4.2 Various techniques are recommended by on-line ana- 6.2 Static Stability Measurements for Baseline
lyzer manufacturers for standardization or static testing. These Assessment—A reference material may be used to provide a
techniques are useful for establishing a benchmark before baseline assessment of static measurement precision. The
conducting a comparative test. These techniques also may be reference material may be used to compare current mean and
used as diagnostic tests in accordance with methods recom- standard deviation values with previous mean and standard
mended by on-line analyzer manufacturers and graphical and deviation values, previously collected in the same manner. The
statistical techniques included in this guide. resulting comparative data may be used to assess whether any
change in the mean or standard deviation of the static mea-
surements may be attributed to a change in the operating
5. Significance and Use
characteristics of the analyzer, in the absence of the influence
5.1 On-line analyzers are used to provide quality data on
of sampling and analysis.
lots of coal. The resulting quality data are used as a production
6.2.1 Reference materials may include actual coal in a
tool or for some contractual application. This guide provides
sealed container, cast high-carbon solids, or other materials
means of evaluating the system and data produced.
which may be provided by the analyzer manufacturer. The
5.2 The user should become familiar with the document’s
primary characteristic of these materials is that they not be
terminology and layout. The section on test design and data
subject to changes in composition.
collectionwillprovidethemeansbywhichalltheanalysisdata
6.2.2 The results of this evaluation can indicate whether
will be gathered. The test design should be carefully consid-
analyzer performance has significantly degraded or whether a
ered so as to assure meeting the user’s requirements.
shift may have occurred. If so, it may be possible to adjust the
5.3 The procedures defined in this guide can be used to test
analyzer to restore initial performance. If the user wishes only
the accuracy and precision of an on-line analyzer, for accep-
to measure current static repeatability, any available coal may
tance after its installation, to check precision and accuracy
be used in the analysis zone of the analyzer. Note, however,
during routine use (quality control), when changes are made to
that the actual standard deviation in static repeatability tests
the system, when the nature of the coal being tested changes,
might be influenced by the composition of the coal being
and to determine mathematical factors to be used for calibra-
examined or analyzer factors, such as the strength of the
tion of the on-line analyzer.
radioactive sources used by the analyzer or condition of
analyzer electronic components.
6. Selection and Conduct of Performance Evaluations
6.2.3 It is essential that the length of the analysis period be
6.1 Introduction:
defined, for example, 1, 2, or 5 min, and be constant in the
6.1.1 Several techniques can be used to evaluate the perfor-
static stability test.The static standard deviation resulting from
mance of an on-line analyzer. These techniques provide data
the static stability test decreases as the length of the analysis
that can be evaluated by using the graphical and statistical
period increases. Static stability testing may be conducted on
methods described in Section 7 of this guide.
the same day(s) as comparative tests. One type of static test
6.1.2 At time of installation, all of the graphical and
involves a comparison of the analyzer to static coal over many
numerical methods outlined in this may prove useful. On a
hours.
routine basis, conducting any of the instrument stability checks
6.3 Comparison of Analyzer System to Reference System
and comparative evaluations that do not disrupt normal opera-
Measurements:
tionsmayproveuseful.Controlchartsmaybeappliedtoallthe
6.3.1 Once an analyzer installation has been completed and
performance measures that are gathered on a routine basis, for
calibration adjustments have been made, the analyzer owner
example, mean analysis value of reference material, RMSD,
may require acceptance testing. Also, the analyzer owner may
and so forth.
decide to relocate the analyzer. In these cases, comparison
6.1.3 In the event that there is a change to the operational
tests, that is, to compare the analyzer system results to
parametersortheequipmentassociatedwiththeanalyzerorthe
conventional sampling and analysis techniques, will provide
reference system, comparative checks should be performed. In
the user calibration verification data and/or data that could be
addition to comparative checks, standardization or static
used for recalibration of the analyzer.
checks, or both, as recommended by the on-line analyzer
6.3.2 Depending upon the comparative technique chosen,
manufacturer may be helpful.
there may be need for more than one comparison. These
6.1.4 Changes in the following may impact performance
comparisonsmaybeconductedinabatchoverseveralhoursor
evaluations. Coal characteristics, such as particle size, source
days or continuously throughout the operational life of the
of coal, mining techniques, degree of preparation, and so forth,
analyzer system.
which if changed from previous test periods and are not in the
analyzer calibration database, may affect analyzer precision 6.3.3 If two independent conventional coal-sampling and
and accuracy: laboratory analysis measurements can be made from each of a
series of batches of coal interrogated by the analyzer, methods
6.1.4.1 Analyzer components;
6.1.4.2 Coal-handling system; developed by Grubbs (1-3) can be used to provide unbiased
estimates of the measurement precision of the analyzer and of
6.1.4.3 Laboratory services;
the conventional sampling and analysis methods.
6.1.4.4 Sampling technique;
6.1.4.5 Coal flow rates; and
6.3.4 Any two series of measurements are independent if
6.1.4.6 Power disturbances. their measurement errors are uncorrelated. Correlation of
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D6543–00
measurement errors can be avoided and independence assured more than one comparison will be made. Since this type of
by use of a true random selection of physical increments or sample does not allow statistical inferences to be drawn in a
samples of material or by using different schemes and equip- rigorous manner, its use is discouraged. Indeed, the only use of
ment for collection, preparation, and laboratory analysis of the this type of comparison might be for control charting purposes
samples, or both. A complete treatment of the subject of relative to an historical reference.
independence of measurements and the various means of 6.4.2 Selection of Reference Sample Point(s):
assuring independence is beyond the scope of this guide. 6.4.2.1 Comparative tests can be used to evaluate the
performance of either the analyzer itself or the “analyzer
6.4 Sampling Considerations:
system” (consisting of the analyzer and the sampling system
6.4.1 Selection of Appropriate Sampling and Sample Prepa-
that feeds it). The comparative evaluations of the analyzer
ration Methods—The following increment collection methods
system can be used to determine the ability of the analyzer
(see Test Methods D 2234) are listed in general order of
system to measure the characteristics of the main coal stream.
preference; this preference is not rigid. Often, practical con-
The selection of the reference system sample point(s) deter-
siderations may supercede increment selection decisions. The
mines whether the comparative tests will assess the analyzer or
methodtobeusedforsamplepreparationshouldbedetermined
the analyzer system.
before the beginning of increment collection. Sample prepara-
6.4.2.2 The most direct and practical two-instrument test,
tiontechniquesshouldremainconsistent(seeMethodD 2013).
when the analyzer is fed the secondary reject of a mechanical
Before installation of the analyzer, consideration should be
sampling system, uses the final save to compare directly to the
given to the ability to obtain representative samples for
analyzer. A manual or mechanical sample collected from the
comparison to analyzer measurements and the regimen for
analyzer discharge may provide an independent sample, which
sample handling and analysis. For the use of mechanical
may be used to assess the performance of the analyzer (see
sampling systems, inspection (see Guide D 4702) and bias
Figs. 1-3).
testing (see Practice D 6518) are good methods for evaluation
6.4.2.3 There are instances when there is no save sample
of the system’s suitability for the test.
(see Fig. 4) associated with the system feeding the analyzer. In
6.4.1.1 Full Stream Cuts—Whenever possible, the full
this case, it is possible to construct a test with several
stream cut method of increment collection should be used in
comparisons by collecting separate samples from the analyzer
the evaluation of an on-line analyzer. This is imperative for
feed and discharge. Since independence of the samples is
drawing inference using statistical techniques.
important for three instrument evaluations, subsequent prepa-
6.4.1.2 Stopped Belt Cut—Although using “stopped belt”
ration and analyses should be performed at different times by
increments allows drawing statistical inferences from the data,
different parties.
the stopped belt increment has limited applicability in the
6.4.2.4 In some instances, the discharge of the analyzer may
evaluation of on-line analyzers. This especially is true in
be fed to further stages of mechanical sampling.Asingle stage
collection of a sample from the lot interrogated by an analyzer
of sampling downstream of the analyzer is most common (see
operating in conjunction with a mechanical sampling system.
Fig. 5). In this case, the secondary save will provide a
The stopped belt increment may have applicability in instances
convenient comparison sample. A test of such a system that
in which the analyzer is used in conjunction with mechanical
requires more than one set of comparative data might incor-
sampling, and the discharge of the analyzer may be metered
porate a series of samples (stopped belt or full stream cut)
onto a belt that is subject to stopping without interference with
collected from the analyzer discharge or the secondary reject
th
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