1、Designation: D6621 00 (Reapproved 2017)Standard Practice forPerformance Testing of Process Analyzers for AromaticHydrocarbon Materials1This standard is issued under the fixed designation D6621; the number immediately following the designation indicates the year oforiginal adoption or, in the case of
2、 revision, the year of last revision. 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 practice serves as a practical guide for the perfor-mance testing of process stream analyz
3、ers specifically formeasuring chemical or physical characteristics of liquid aro-matic hydrocarbon materials for production or certification ofthese materials. The practice may be applicable to otherhydrocarbon stream analyzers as well.1.2 Only external methods (complete substitution of theprocess s
4、tream with a standard) of control sample introductionare included. Internal methods are beyond the scope of thispractice.1.3 Methods for resetting key operational parameters ofanalyzers to match predefined limits are provided by vendorsand are not included in this practice.1.4 Analyzer validation pr
5、ocedures are covered in PracticesD3764 and D6122, not in this practice.1.5 Procedures for statistically interpreting data from auto-matic sampling process stream analyzers are outlined.1.6 The implementation of this practice requires that theanalyzer be installed according to APIRP-550 (1),2and be i
6、nagreement with the analyzer suppliers recommendations.Also, it assumes that the analyzer is designed to monitor thespecific material parameter of interest, and that at the time ofinitial or periodic validation, the analyzer was operating at theconditions specified by the manufacturer and consistent
7、ly withthe primary test method.1.7 The units of measure used in this practice shall be thesame as those applicable to the test primary method used foranalyzer validation.1.8 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility
8、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.1.9 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the D
9、ecision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:3D3764 Practice for Validation of the Performance of ProcessStream Analyzer Sys
10、temsD4177 Practice for Automatic Sampling of Petroleum andPetroleum ProductsD6122 Practice for Validation of the Performance of Multi-variate Online, At-Line, and Laboratory Infrared Spectro-photometer Based Analyzer SystemsE456 Terminology Relating to Quality and StatisticsE1655 Practices for Infra
11、red Multivariate QuantitativeAnalysis3. Terminology3.1 Definitions:3.1.1 accuracy, ncloseness of agreement between a testresult and an accepted reference value.3.1.2 analyzer output, nsignal that is proportional to thequality parameter being measured and suitable for input toreadout instrumentation.
12、3.1.2.1 DiscussionIt may be pneumatic, electrical, digital,etc., and expressed as psi, mv, sec., etc.3.1.3 analyzer result, nnumerical estimate of a physical,chemical, or quality parameter produced by applying thecalibration model to the analyzer output signal.3.1.4 bias, nthe difference between the
13、 expectation of theresults and an accepted reference value.1This practice is under the jurisdiction of ASTM Committee D16 on Aromatic,Industrial, Specialty and Related Chemicals and is the direct responsibility ofSubcommittee D16.04 on Instrumental Analysis.Current edition approved July 1, 2017. Pub
14、lished July 2017. Originally approvedin 2000. Last previous edition approved in 2012 as D6621 00 (2012). DOI:10.1520/D6621-00R17.2The boldface numbers in parentheses refer to the list of references at the end ofthis practice.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcon
15、tact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international stan
16、dard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.13.1.5
17、 control sample, nmaterial similar to the processstream that is stable over long periods of time so that itsparameters may be measured reproducibly in performance teststo characterize analyzer precision and accuracy.3.1.5.1 DiscussionMay be a pure compound, standardmixture, or a sample from the proc
18、ess stream. Its parametersare used to plot statistical process control charts to defineanalyzer precision in normal operation.3.1.6 external performance testing, nprocedure involvingcomplete substitution of the process/product stream measuredby the analyzer with a control sample stream to measure th
19、eanalyzers precision and possibly accuracy (if the controlsamples true value is known).3.1.7 internal performance testing, nprocedure involvingthe addition of a known quantity of a standard materialhomogeneously into the process/product stream measured bythe analyzer to measure the analyzers precisi
20、on and possiblyaccuracy (if the sample materials true value is known).3.1.8 linearity, nparameter ranges where the analyzersresults do and do not approximate a straight line.3.1.9 performance testing of an analyzer, nmechanicaland statistical procedure for routinely checking the accuracyand precisio
21、n of an analyzers results against historical accu-racy and precision for a control sample.3.1.10 precision, ncloseness of agreement of independenttest results of the same chemical or physical property of a givenmaterial obtained under stipulated conditions.3.1.10.1 DiscussionExpressed in terms of di
22、spersion oftest results around the arithmetic mean, usually as variance,standard deviation, repeatability or reproducibility, or both.3.1.11 repeatability of an analyzer, ndifference betweentwo successive analyzer results measured in a short timeinterval that would be exceeded in the long run in onl
23、y 1 casein 20 (5 % of the time) when the analyzer is operated on aflowing sample of uniform quality.3.1.12 reproducibility of an analyzer, ndifference betweena single result from each of two identical analyzer systems thatwould be exceeded in the long run in only 1 case in 20 (5 % ofthe time) when t
24、he two systems are operated at different sitesby different operators, but on identical samples.3.1.13 rule violation, ncondition when a point value orpattern of points in a statistical process control chart statisti-cally exceeds the defined probability of its occurrence, asdefined by the Western El
25、ectric rules (2) being used.3.1.14 spot sample, nrepresentative material resemblingthe stream being monitored, an identical portion of which isanalyzed both in a process analyzer and by a laboratory test ona non-scheduled basis for periodic validation testing.3.1.14.1 DiscussionMay be the same mater
26、ial as thecontrol sample.3.1.15 validation of an analyzer, nprocess to identify howcomparable an analyzers results are statistically to results fromthe primary method, or to define how the analyzers resultscompare to the primary methods results in precision andaccuracy.3.1.15.1 DiscussionMust be don
27、e when the analyzer isfirst configured or reconfigured (initial validation), and then ona periodic basis (periodic validation), as described in PracticeD3764.3.2 For additional definitions, see Appendix X1.4. Summary of Practice4.1 This practice standardizes aromatic hydrocarbonprocess-analyzer perf
28、ormance testing practices, or processesfor maintaining accurate and precise analyzer measurements. Itis used with methods for the measurement and certification ofaromatic hydrocarbon materials applied to continuous on-lineanalyzers. These methods are generally under the control ofCommittee D16 onAro
29、matic, Industrial, Specialty and RelatedChemicals. It is meant as a practical guide for persons settingup and maintaining these analyzers in a process (non-laboratory) environment. They should apply it, with theirknowledge of the analyzers operation and of how the processanalyzer results are to be u
30、sed, to maintain and optimizeanalyzer operation.5. Significance and Use5.1 Performance testing of on-line analyzers is critical totheir proper performance within predictable levels of precisionand accuracy. This practice can affect production efficiency andcertification of aromatic hydrocarbon mater
31、ials.6. System Components6.1 Process analyzers (Fig. 1) for measuring the chemicalcomposition of aromatic hydrocarbons, their purity, or physicalproperties often replace existing laboratory test methods, usingthe same or similar chemical measurement techniques. showsseveral possible analyzer configu
32、rations for on-line processtesting of aromatic hydrocarbon materials. Aromatic hydrocar-bon stream analyzers are often based on chromatography, butthey may also perform physical measurements, wet chemistry,or other methods described in new or existing Committee D16methods. This practice is intended
33、to be generally applicable toany of them.7. Performance Guidelines Before Calibration7.1 At startup, validate any process analyzer against anexisting analytical method, typically in this case, one overseenby Committee D16.7.2 The capability measurement (cm) for a given analyzer(3) shall be less than
34、 0.2, as defined in Eq 1:cm5 a2/p2,0.2 (1)where:a= standard deviation of the analyzer measurement, andp= standard deviation of the process.The variance (standard deviation squared) of the analyzershould be less than 20 % of the variance of the process, so thatthe analyzer measurement can be useful f
35、or detecting changesin the process. The expected capability for a process analyzermeasurement may be available from the vendor for a specificapplication before installation of the analyzer (advertisedD6621 00 (2017)2analyzer capability). Actual process stream measurement ca-pability should be measur
36、ed on the process/product stream,usually after initial analyzer validation.7.3 Automated analyzer sampling practices for aromatichydrocarbon liquid streams shall follow those referenced inPractice D4177.7.4 Determine the linearity of the process analyzer by usingat least three calibration standard m
37、aterials with knowncompositions/responses for the components of interest. Eachcomponent should be present at a high, low, and mediumconcentration/amount level with respect to the concentration/amount range expected for the parameter (analyzer operatingrange). A plot of the component concentration/am
38、ount versusanalyzer response will determine if the analyzer has a linearresponse over the concentration range of interest. If analyzerresponse is nonlinear, additional calibration standards must beanalyzed to clearly determine the nonlinear behavior of eachanalyzer and component, if the analyzer is
39、to be used in thenonlinear range.7.5 If a process analyzer is to be used only for trendinformation, the data generated by it is in a form that does notimpart compositional information, but relative informationonly, that is, peak area, peak height, counts, millivolts, etc.Initial validation and frequ
40、ent performance testing are stillrequired to define precision, as well as to maintain properanalyzer operation.8. Performance Test Procedure8.1 Determine analyzer performance using external checksamples, which are substituted for the process material streamduring performance test runs.8.2 Process an
41、alyzers are routinely performance tested byusing control samples. These may be primary or secondarystandard materials, or actual portions from the process stream.These portions must be representative of normal processconditions, and be stored to remain physically and chemicallystable over time. The
42、control sample should be repeatedlyanalyzed by the process analyzer, and then using statisticalprocess control (SPC), to define the actual analyzer resultsprecision.8.3 Analyzer performance test frequency can be done at afixed time interval, based on analyzer reliability and operatorexperience. Typi
43、cally, once per shift, day, or week are used, butit may be more or less frequent. Unscheduled control sampleanalyses may be performed whenever the unit operator feelsthat something has changed in the process or process analyzer,or at a convenient time.8.4 The control sample material container shall
44、be located ata point in the process to allow for its simple and regularintroduction into the process analyzers sample introductionsystem (if appropriate) by the process operator. A sufficientquantity must be available for many repetitive analyses.8.5 Perform an external analyzer performance test bys
45、witching the analyzer sample source from the process streamto the control sample, followed by sampling and analysis of thecontrol sample.8.6 Monitor the analyzers output from the control sampleuntil it stabilizes, that is, the difference between successivereadings is at or below the repeatability of
46、 the analyzer, (whichis measured as described in 8.10). If this does not occur, therepeatability of the analyzer has changed and should beremeasured.FIG. 1 Possible Process Analyzer ConfigurationsD6621 00 (2017)38.7 After stabilization of the analyzer, measure at least threesuccessive results on the
47、 control sample and average theresults. Plot the average of these three results in a SPC chartusing any statistically correct method of data handling andcontrol chart construction (4).8.8 SPC charts of the control sample data shall be used tohelp decide if the analyzer needs to have its response par
48、am-eters reset, (5) or if it is working within previous statisticallevels and should be left alone. SPC results and operatorexperience should be used to determine subsequent actions,such as determining the cause for any rule violation andcorrecting it.8.9 SPC charts of control samples help the opera
49、tor todifferentiate between normal (random) and abnormal (nonran-dom) analyzer variation due to changes in analyzer operation.8.9.1 Charts may be maintained manually or with commer-cially available SPC software, preferably as part of the ana-lyzer data acquisition and control software.8.9.2 Control limits should be set at three (3) sigma (stan-dard deviations) from the mean value, warning limits at two (2)sigma, and suitable Western Electric rules (2) invoked, consis-tent with plant/facility statistical policy.8.9.3 All rule vio
