1、Designation: D6543 14Standard Guide tothe Evaluation of Measurements Made by Online CoalAnalyzers1This standard is issued under the fixed designation D6543; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision.
2、 A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide provides techniques to be used for theevaluation of the measurement performance of online coalanalyzers.1.2 This standard
3、 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 appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM
4、Standards:2D2013 Practice for Preparing Coal Samples for AnalysisD2234/D2234M Practice for Collection of a Gross Sampleof CoalD6518 Practice for Bias Testing a Mechanical Coal Sam-pling System (Withdrawn 2008)3D7430 Practice for Mechanical Sampling of CoalE178 Practice for Dealing With Outlying Obse
5、rvations3. Terminology3.1 Definitions:3.1.1 analyzer system, na coal quality measurement sys-tem which includes an online coal analyzer and which mayinclude one or more stages of a coal-sampling system.3.1.2 calibration, nmathematical modeling of analyzerand comparative coal sampling and analysis da
6、ta. Factors fromthe model are used in the online analyzer control software.3.1.3 Grubbs estimator, nan estimate of the measurementprecision of an online analyzer (1-3).43.1.4 online analyzer, nan analytical tool consisting of aninstrument and systems, which together provide measurements,or estimates
7、, or both, of coal quality parameters.3.1.5 outlier, nan extreme value that statistical tests indi-cate to be far enough from other results in a population underconsideration to cause suspicion that the value is not a memberof the population.3.1.6 reference material, nmaterial of stable compositiont
8、hat may be used to generate static analyzer measurements.3.1.7 reference system, na measurement system used tomeasure the characteristics of a lot of coal that are alsomeasured by an online analyzer, and against which the onlineanalyzer measurements are compared.3.1.8 standardization, ncalibration o
9、f an instrument to areference material using static stability measurements.3.1.9 static stability, nan estimate of the measurementprecision of an instrument obtained on material that is notmoving. The estimate normally is expressed as the standarddeviation and average of the measurements for a given
10、 periodof time.3.1.10 synchronization error, nan error that occurs fromcomparing measurements made by an online analyzer and areference system that are not measuring exactly the same lotbecause of temporal and/or spatial offsets.4. Summary of Guide4.1 This guide describes how to measure performance
11、of anonline analyzer using comparative measurements. The perfor-mance evaluation consists of a paired comparison of analysesfrom a reference method using ASTM sampling, samplepreparation, and analysis methods for several lots of coal withthe analyses from the online analyzer for the same lots of coa
12、l.The data resulting from the comparative test may be evaluatedusing graphical and statistical techniques outlined below.4.2 Various techniques are recommended by online analyzermanufacturers for standardization or static testing. These1This guide is under the jurisdiction of ASTM Committee D05 on C
13、oal andCoke and is the direct responsibility of Subcommittee D05.23 on Sampling.Current edition approved March 1, 2014. Published May 2014. Originallyapproved in 2000. Last previous edition approved in 2012 as D654300(2012).DOI: 10.1520/D6543-14.2For referenced ASTM standards, visit the ASTM website
14、, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.4The boldface numbers in parent
15、heses refer to the list of references at the end ofthis standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1techniques are useful for establishing a benchmark beforeconducting a comparative test. These techniques may also beused
16、as diagnostic tests in accordance with methods recom-mended by online analyzer manufacturers and graphical andstatistical techniques included in this guide.5. Significance and Use5.1 Online analyzers are used to provide quality data on lotsof coal. The resulting quality data are used as a production
17、 toolor for some contractual application. This guide provides themeans of evaluating the analyzer system and the data pro-duced.5.2 Become familiar with the documents terminology andlayout. The section on test design and data collection willprovide the means by which all the analysis data will begat
18、hered. The test should be carefully designed to ensure theusers requirements are met.5.3 The procedures defined in this guide can be used toestimate the accuracy and precision of an online analyzer, (1)to conduct acceptance testing following installation and (2) tomonitor the accuracy and precision
19、(a) during routine use(quality control), (b) when significant changes are made to theanalyzer, and (c) when a significant change in the coal beinganalyzed occurs (e.g., a different seam at a mine, or a new coalsource at a power plant). These procedures can also be used forcalibration purposes.6. Sel
20、ection and Conduct of Performance Evaluations6.1 Introduction:6.1.1 Several techniques can be used to evaluate the perfor-mance of an online analyzer. These techniques provide datathat can be evaluated by using the graphical and statisticalmethods described in Section 7 of this guide.6.1.2 At the ti
21、me of installation, all of the graphical andnumerical methods outlined in this guide may prove useful. Ona routine basis, conducting any of the instrument stabilitychecks and comparative evaluations that do not disrupt normaloperations may prove useful. Control charts may be applied toall the perfor
22、mance measures that are gathered on a routinebasis, including mean analysis value of reference material,RMSD, etc.6.1.3 In the event that there is a change to the operationalparameters or the equipment associated with the analyzer or thereference system, comparative checks should be performed. Inadd
23、ition to comparative checks, standardization or staticchecks, or both, as recommended by the online analyzermanufacturer may be helpful.6.1.4 Changes in the following may impact performanceevaluations. Coal characteristics, such as particle size, sourceof coal, mining techniques, degree of preparati
24、on, and so forth,which if changed from previous test periods and are not in theanalyzer calibration database, may affect analyzer precisionand accuracy:6.1.4.1 Analyzer components;6.1.4.2 Coal-handling system;6.1.4.3 Laboratory services;6.1.4.4 Sampling technique;6.1.4.5 Coal flow rates; and6.1.4.6
25、Power disturbances.6.2 Static Stability Measurements for BaselineAssessmentA reference material may be used to provide abaseline assessment of static measurement precision. Thereference material may be used to compare current mean andstandard deviation values with mean and standard deviationvalues,
26、previously collected in the same manner. The resultingcomparative data may help determine whether any apparentdecline in analyzer dynamic performance may be attributed toa change in the operating characteristics of the analyzer, in theabsence of the influence of sampling, preparation, and analysis.6
27、.2.1 The results of this evaluation can indicate whetheranalyzer precision has significantly degraded or whether a biasmay have occurred. If so, it may be possible to adjust theanalyzer to restore initial performance. If the user wishes onlyto measure current static stability, any available coal may
28、 beused in the analysis zone of the analyzer. Note, however, thatthe actual standard deviation in static stability tests might beinfluenced by the composition or mass of the coal beingexamined or analyzer factors, such as the strength of theradioactive sources used by the analyzer or condition ofana
29、lyzer electronic components.6.2.2 It is essential that the length of the analysis period bedefined, (for example, 1 minute, 2 minutes, or 5 minutes) andbe constant in the static stability test. The standard deviationresulting from the static stability test decreases as the length ofthe analysis peri
30、od increases.6.3 Comparison of Analyzer System to Reference SystemMeasurements:6.3.1 Once an analyzer installation has been completed andcalibration adjustments have been made, the analyzer ownermay require acceptance testing. Also, the analyzer owner maydecide to relocate the analyzer. In these cas
31、es, comparisonteststhat is, to compare the analyzer system results to conven-tional sampling and analysis techniqueswill provide the usercalibration verification data and/or data that could be used forrecalibration of the analyzer.6.3.2 Since performance evaluations usually consist of 30 ormore comp
32、arisons, with each of these lasting from 30 minutesto three hours, these comparisons may be conducted in a batchover several hours or days, or continuously throughout theoperational life of the analyzer system.6.3.3 If two independent conventional coal-sampling andlaboratory analysis measurements ca
33、n be made from each of aseries of batches of coal interrogated by the analyzer, methodsdeveloped by Grubbs (1-3) can be used to provide unbiasedestimates of the measurement precision of the analyzer and ofthe conventional sampling and analysis systems.6.3.4 Any two series of measurements are indepen
34、dent iftheir measurement errors are uncorrelated. Correlation ofmeasurement errors can be avoided and independence assuredby use of a true random selection of physical increments orsamples of material or by using different schemes and equip-ment for collection, preparation, and laboratory analysis o
35、f thesamples, or both. A complete treatment of the subject ofindependence of measurements and the various means ofassuring independence is beyond the scope of this guide.D6543 1426.4 Sampling Considerations:6.4.1 Selection of Appropriate Sampling and Sample Prepa-ration MethodsDecisions regarding sa
36、mple collection shouldbe governed by Practices D2234/D2234M and D7430 asappropriate. The method to be used for sample preparationshould be determined before the beginning of incrementcollection. Sample preparation techniques should remain con-sistent (see Practice D2013). Before installation of thea
37、nalyzer, consideration should be given to the ability to obtainrepresentative samples for comparison to analyzer measure-ments and the regimen for sample handling and analysis. Forthe use of mechanical sampling systems, inspection (seePractice D7430, Part C) and bias testing (see Practice D7430,Part
38、 D) are good methods for evaluation of the systemssuitability for the test.6.4.2 Selection of Reference Sample Point(s):6.4.2.1 Comparative tests can be used to evaluate theperformance of either the analyzer itself or the “analyzersystem” (consisting of the analyzer and the sampling systemthat feeds
39、 it). The comparative evaluations of the analyzersystem can be used to determine the ability of the analyzersystem to measure the characteristics of the main coal stream.The selection of the reference system sample point(s) deter-mines whether the comparative tests will assess the analyzer orthe ana
40、lyzer system.6.4.2.2 The most direct and practical two-instrument test,when the analyzer is fed the secondary reject of a mechanicalsampling system, uses the final save to compare directly to theanalyzer. A manual or mechanical sample collected from theanalyzer discharge may provide an independent s
41、ample, whichmay be used to assess the performance of the analyzer (seeFigs. 1-3).6.4.2.3 There are instances when there is no save sample(see Fig. 4) associated with the system feeding the analyzer. Inthis case, it is possible to construct a test with severalcomparisons by collecting separate sample
42、s from the analyzerfeed and discharge. Since independence of the samples isimportant for three instrument evaluations, subsequent prepa-ration and analyses should be performed at different times bydifferent parties.6.4.2.4 In some instances, the discharge of the analyzer maybe fed to further stages
43、of mechanical sampling. A single stageof sampling downstream of the analyzer is most common (seeFig. 5). In this case, the secondary save will provide aconvenient comparison sample. A test of such a system thatrequires more than one set of comparative data might incor-porate a series of samples (sto
44、pped belt or full stream cut)collected from the analyzer discharge or the secondary rejectstream, as well. In the relatively rare circumstances in whichthe analyzer discharge feeds two additional stages of sampling,the tertiary save is recommended for two-instrument and biastesting, and a stopped be
45、lt or full stream cut of the secondaryor tertiary rejects of the analyzer discharge may be used as athird instrument. Practical considerations of increment collec-tion at the secondary reject should be balanced with consider-ations of sampling variances introduced by crushing andtertiary sampling. F
46、or two instruments to be independent ofeach other, one or both instruments must interrogate the streamof interest without changing the characteristics of the stream.FIG. 1 Key to SchematicsFIG. 2 Analyzer on Secondary RejectThree-Stage MechanicalSamplingFIG. 3 Analyzer on Secondary RejectTwo-Stage M
47、echanicalSamplingD6543 143This may be true in some through-belt noncontacting configu-rations. In the case of flow-through analyzers that require asample, the independence of systems is obtained in a case inwhich the primary coal stream is sampled by one instrumentbefore being sampled by another ins
48、trument (see Fig. 6). In thiscase, the two systems may be evaluated by comparing theanalyzer values to the final save of the mechanical system. Theanalyzer itself may be evaluated by comparison to samplescollected at its discharge.6.4.3 SynchronizationTo evaluate the analyzersperformance, the lot of
49、 coal interrogated by the analyzer mustbe the same lot of coal measured by the reference system.Generally, this is accomplished by sampling the coal streamafter it passes the analyzers analysis zone. Care should betaken to ensure that transport times within the coal-handlingsystem of interest, within mechanical sampling systems used toprovide comparative measurements, and between sample col-lection and analyzer be measured and accounted for in anycomparisons. Comparisons in which intervening storage of thecoal takes place between the analyzer and reference mea
