1、Designation: D6543 14bStandard 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 standar
3、d 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Practice for Collection of a Gross Sampleof CoalD6518 Practice for Bias Testing a Mechanical Coal Sam-pling System (Withdrawn 2008)3D7430 Practice for Mechanical Sampling of CoalE178 Practice for Dealing With Outlying Obs
5、ervations3. 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 d
6、ata. Factors fromthe model are used in the online analyzer control software.3.1.3 Latent Variable Model, na mathematical model thatcan estimate each systems precision, when the analyzer iscompared to two independent reference systems.3.1.4 online analyzer, nan analytical tool consisting of aninstrum
7、ent and systems, which together provide measurements,or estimates, 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 popu
8、lation.3.1.6 reference material, nmaterial of stable compositionthat 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 onlineanalyze
9、r measurements are compared.3.1.8 standardization, ncalibration of 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
10、the standarddeviation and average of the measurements for a given 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. Sum
11、mary of Guide4.1 This guide describes how to measure performance 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 w
12、iththe analyses from the online analyzer for the same lots of coal.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. Thes
13、etechniques are useful for establishing a benchmark beforeconducting a comparative test. These techniques may also beused as diagnostic tests in accordance with methods recom-mended by online analyzer manufacturers and graphical andstatistical techniques included in this guide.1This guide is under t
14、he jurisdiction of ASTM Committee D05 on Coal andCoke and is the direct responsibility of Subcommittee D05.23 on Sampling.Current edition approved Sept. 1, 2014. Published October 2014. Originallyapproved in 2000. Last previous edition approved in 2014 as D6543-14a. DOI:10.1520/D6543-14b.2For refere
15、nced ASTM standards, visit the ASTM website, 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 onw
16、ww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15. Significance and Use5.1 Online analyzers are used to provide quality data on lotsof coal. The resulting quality data are used as a production toolor for some contractual a
17、pplication. 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 begathered. The test should be care
18、fully 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 (a) during routine use(quality
19、 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. Selection and Conduct of Performa
20、nce 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 time of installation, all of the
21、 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 performance measures that are gather
22、ed on a routinebasis, including mean analysis value of reference material,RMSD, etc.6.1.3 Whenever there is a major change to the operatingparameters, the configuration, the calibration, the processes, orthe hardware associated with the analyzer or the referencesystem, the user may wish to perform c
23、omparative tests. Inaddition to comparative tests, standardization or static tests, orboth, as recommended by the online analyzer manufacturer,may be helpful.6.1.4 Changes in coal characteristics may also impact ana-lyzer performance. Particle size, source of coal, miningtechniques, and degree of pr
24、eparation, which if changed fromprevious test periods and which are not in the analyzercalibration database, may affect analyzer precision and accu-racy.6.1.5 Additional changes which could merit performancetesting include a change in the material or width of theconveyor, or coal flow rates (in the
25、case of full-flow analyzers).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 deviati
26、onvalues, 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
27、analysis.6.2.1 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 availabl
28、e coal may 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 condi
29、tion ofanalyzer electronic components.6.2.2 It is essential that the length of the analysis period bedefined, (for example, one minute, two minutes, or fiveminutes) and be constant in the static stability test. Thestandard deviation resulting from the static stability test de-creases as the length o
30、f the analysis period 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 ana
31、lyzer. In these cases, 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 consis
32、t of 30 ormore comparisons, 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 analy
33、sis measurements can be made from each of aseries of batches of coal interrogated by the analyzer, theLatent Variable Model (LVM) 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 measure
34、ments are independent 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 labo
35、ratory analysis of 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.6.4 Sampling Considerations:6.4.1 Selection of Appropriate Sampling and Sample Prepa-ration MethodsDecisions rega
36、rding sample 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
37、 of theD6543 14b2analyzer, 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 P
38、ractice D7430,Part 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 samplin
39、g systemthat feeds 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
40、analyzer orthe analyzer 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 provid
41、e an independent sample, 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 collecti
42、ng separate samples from the analyzerfeed and discharge.6.4.2.4 In some instances, the discharge of the analyzer maybe fed to further stages of mechanical sampling. A single stageof sampling downstream of the analyzer is most common (seeFig. 5). In this case, the secondary save will provide aconveni
43、ent comparison sample. A test of such a system thatrequires more than one set of comparative data might incor-porate a series of samples (stopped belt or full stream cut)collected from the analyzer discharge or the secondary rejectstream, as well. In the relatively rare circumstances in whichFIG. 1
44、Key to SchematicsFIG. 2 Analyzer on Secondary RejectThree-Stage MechanicalSamplingFIG. 3 Analyzer on Secondary RejectTwo-Stage MechanicalSamplingFIG. 4 Single-Stage Mechanical SamplingD6543 14b3the analyzer discharge feeds two additional stages of sampling,the tertiary save is recommended for two-in
45、strument and biastesting, and a stopped belt 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 intr
46、oduced by crushing andtertiary sampling. For two instruments to be independent ofeach other, one or both instruments must interrogate the streamof interest without changing the characteristics of the stream.This may be true in some through-belt noncontacting configu-rations. In the case of flow-thro
47、ugh 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 instrument (see Fig. 6). In thiscase, the two systems may be evaluated by comparing theanalyzer values to the final save o
48、f 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 coal interrogated by the analyzer mustbe the same lot of coal measured by the reference system. Thisevaluation is usua
49、lly accomplished by sampling the coal streamafter it passes the analyzers analysis zone except for samplestream analyzers. Care should be taken to ensure that transporttimes within the coal-handling system of interest, withinmechanical sampling systems used to provide comparativemeasurements, and between sample collection and the analyzerbe measured and accounted for in any comparisons. Compari-sons in which intervening storage of the coal takes placebetween the analyzer and reference measurements should beavoided.6.4.4 Length of Comparison PeriodThe length o
