1、Designation: D7808 12Standard Practice forDetermining the Site Precision of a Process StreamAnalyzer on Process Stream Material1This standard is issued under the fixed designation D7808; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisi
2、on, 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.INTRODUCTIONWhen a process stream analyzer is used to monitor or control a process, the results produced by theana
3、lyzer are typically used as surrogates for values that would otherwise have been obtained viaanalyses of process samples using a Primary Test Method (PTM). Successful application of theanalyzer requires that the Predicted Primary Test Method Result (PPTMR) produced by the analyzeragrees with the Pri
4、mary Test Method Result (PTMR) to within some user specified accuracy (bias andprecision). To achieve this goal, it is typically necessary to develop a correlation that relates raw,Uncorrected Analyzer Results (UARs) to PTMRs. The correlation and the analyzers performance arethen assessed during the
5、 analyzer validation to establish the expected agreement between the PPTMRand PTMR. In establishing the correlation, and assessing the performance, it is necessary to know theprecision of both the PPTMR and the PTMR. The precision of the PTMRs is typically establishedthrough statistical quality cont
6、rol procedures described in D6299. The precision of the PPTMRs isestablished via procedures described herein. The techniques used to determine process analyzer siteprecision can also be used for ongoing quality control of the analyzer measurement system.1. Scope1.1 This practice describes a procedur
7、e to quantify the siteprecision of a process analyzer via repetitive measurement of asingle process sample over an extended time period. Theprocedure may be applied to multiple process samples to obtainsite precision estimates at different property levels1.1.1 The site precision is required for use
8、of the statisticalmethodology of D6708 in establishing the correlation betweenanalyzer results and primary test method results using PracticeD7235.1.1.2 The site precision is also required when employing thestatistical methodology of D6708 to validate a process analyzervia Practices D3764 or D6122.1
9、.2 This practice is not applicable to in-line analyzers wherethe same quality control sample cannot be repetitively intro-duced.1.3 This practice is meant to be applied to analyzers thatmeasure physical properties or compositions.1.4 This practice can be applied to any process analyzersystem where t
10、he feed stream can be captured and stored insufficient quantity with no stratification or stability concerns.1.4.1 The captured stream sample introduction must be ableto meet the process analyzer sample conditioningrequirements, feed temperature and inlet pressure.1.4.2 This practice is designed for
11、 use with samples that aresingle liquid phase, petroleum products whose vapor pressure,at sampling and sample storage conditions, is less than or equalto 110 kPa (16.0 psi) absolute and whose D86 final boilingpoint is less than or equal to 400C (752F).NOTE 1The general procedures described in this p
12、ractice may beapplicable to materials outside this range, including multiphase materials,but such application may involve special sampling and safety consider-ations which are outside the scope of this practice.1.5 The values for operating conditions are stated in SI unitsand are to be regarded as t
13、he standard. The values given inparentheses are the historical inch-pound units for informationonly.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is the1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Product
14、s and Lubricants and is the direct responsibility of SubcommitteeD02.25 on Performance Assessment and Validation of Process Stream AnalyzerSystems.Current edition approved Oct. 1, 2012. Published January 2013. DOI: 10.1520/D7808-12.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, We
15、st Conshohocken, PA 19428-2959. United States1responsibility 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 Standards:2D86 Test Method for Distillation of Petro
16、leum Products atAtmospheric PressureD3764 Practice for Validation of the Performance of ProcessStream Analyzer SystemsD6122 Practice for Validation of the Performance of Multi-variate Online, At-Line, and Laboratory Infrared Spectro-photometer Based Analyzer SystemsD6299 Practice for Applying Statis
17、tical Quality Assuranceand Control Charting Techniques to Evaluate AnalyticalMeasurement System PerformanceD6708 Practice for Statistical Assessment and Improvementof Expected Agreement Between Two Test Methods thatPurport to Measure the Same Property of a MaterialD7235 Guide for Establishing a Line
18、ar Correlation Relation-ship Between Analyzer and Primary Test Method ResultsUsing Relevant ASTM Standard PracticesD7278 Guide for Prediction ofAnalyzer Sample System LagTimes3. Terminology3.1 Definitions:3.1.1 aliquot, nportion of sample being tested that is arepresentative portion of the whole.3.1
19、.2 analyzer, nall piping, hardware, computer, software,instrumentation and calibration model required to automati-cally perform the analysis of a process or product stream.D61223.1.3 site precision (R), nthe value below which theabsolute difference between two individual test results obtainedunder s
20、ite precision conditions may be expected to occur witha probability of 0.95 (95%). It is defined as 2.77 times thestandard deviation of results obtained under site precisionconditions. D62993.1.4 site precision conditions, nconditions under whichtest results are obtained by one or more operators in
21、a singlesite location practicing the same test method on a singlemeasurement system which may comprise multipleinstruments, using test specimens taken at random from thesame sample of material, over an extended period of timespanning at least a 15 day interval. D62993.1.5 process analyzer system, ns
22、ee analyzer.3.2 Acronyms:3.2.1 LPGliquefied petroleum gas3.2.2 PPTMR(s)predicted primary test method result(s)3.2.3 PTM primary test method3.2.4 PTMR(s)primary test method result(s)3.2.5 QCquality control3.2.6 UAR(s)uncorrected analyzer result(s)4. Significance and Use4.1 The analyzer site precision
23、 is an estimate of the vari-ability that can be expected in a UAR or a PPTMR producedby an analyzer when applied to the analysis of the samematerial over an extended time period.4.2 For applications where the process analyzer systemresults are required to agree with results produced from anindepende
24、nt PTM, a mathematical function is derived thatrelates the UARs to the PPTMRs. The application of thismathematical function to an analyzer result produces a pre-dicted PPTMR. For analyzers where the mathematicalfunction, that is, a correlation, is developed by D7235, theanalyzer site precision of th
25、e UARs is a required input to thecomputation.4.3 After the correlation relationship between the analyzerresults and primary test method results has been established, aprobationary validation (see D3764 and D6122) is performedusing an independent but limited set of materials that were notpart of the
26、correlation activity. This probationary validation isintended to demonstrate that the PPTMRs agree with thePTMRs to within user-specified requirements for the analyzersystem application. The analyzer site precision is a requiredinput to the probationary validation procedures.4.3.1 If the process str
27、eam analyzer system and the primarytest method are based on the same measurement principle(s),or, if the process stream analyzer system uses a direct andwell-understood measurement principle that is similar to themeasurement principle of the PTM then validation is done viaD3764. Practice D3764 also
28、applies if the process streamanalyzer system uses a different measurement technology fromthe PTM, provided that the calibration protocol for the directoutput of the analyzer does not require use of the PTM.4.3.2 If the process stream analyzer system utilizes anindirect or mathematically modeled meas
29、urement principlesuch as chemometric or multivariate analysis techniques wherePTMRs are required for the development of the chemometricor multivariate model, then validation of the analyzer is doneusing Practice D6122.4.3.3 Both the D3764 and D6122 validation practices utilizethe statistical methodo
30、logy of Practice D6708 to conduct theprobationary validation. This methodology requires that thesite precision for the PTM and the analyzer site precision beavailable.4.4 The procedures described herein also serve as the basisfor a process analyzer quality control system. A representativesample of t
31、he QC material is introduced into the analyzersystem in a repeatable fashion. Such sample introductionpermits capturing the effect of the analyzer system operatingvariables on the UAR and PPTMR output signal from theprocess analyzer. By comparing the observed analyzer re-sponses to the expected resp
32、onse for the QC sample, the fitnessfor use of the analyzer system can be determined.2For referenced 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 p
33、age onthe ASTM website.D7808 1225. Procedure5.1 QC Sample CollectionThe intent of this procedure isto capture samples that are representative of the process streamso that these QC samples can be used to establish and monitorthe precision of the analyzer system.5.1.1 Preferably, capture two QC sample
34、s whose propertylevels represent the bottom and top of the range of analyzerservice.5.1.2 For applications where the sample being analyzed isintended to be free of sediment and water, then the QC samplebeing analyzed should also be free of sediment and water.5.1.2.1 Capture the QC sample from a poin
35、t in the analyzersystem after filtration and coalescing have been doneNOTE 2Ideally, sample capture should be at the boundary between theprocess analyzer and the local ambient environment, that is, at the exteriorwall where the sample enters the process analyzer. Sample capture at theexterior wall o
36、f the process analyzer ensures that all variations attributableto the sample conditioning system are accounted for. If sample capture atthe exterior wall of the process analyzer is not possible, sample captureshould occur as close to the exterior wall of the process analyzer aspossible.5.1.2.2 If fi
37、ltering and coalescing that is part of the normaltreatment for process samples is not done when the QC sampleis captured, it needs to be done when the QC sample isintroduced into the analyzer. A larger volume of sample will beneeded to account for the volume of the filter and coalescer andthe requir
38、ed size of the QC sample storage vessel will beincreased.5.1.2.3 Removal of water and other contaminants can im-prove the QC samples storage stability.NOTE 3Care must be exercised that removal of water and othercontaminants does not compromise the integrity of the sample withrespect to the measured
39、parameter(s) of interest.5.1.2.4 Entrained and free water can adversely affect somesample vessel materials of construction.NOTE 4Sample vessel used to store QC materials shall be constructedof materials that do not interact with the sample so as to alter measuredparameter(s) of interest.5.1.3 For ap
40、plications where the sample being analyzed isintended to include sediment or water, or both, then the QCsample should also include sediment or water, or both.5.1.3.1 For such multiphase QC samples, the sample mustbe homogenized prior to introduction into the analyzer.5.1.3.2 A common application of
41、this type would be themeasurement of sediment or water, or both, in crude and fueloil.5.1.4 The process analyzer system should include a linesample collection facility to permit capture of aliquots of theprocess stream for analysis by the PTM.5.1.4.1 The line samples can be used to assess the validi
42、ty ofthe sample collected before starting the process analyzer siteprecision data collection process.5.1.4.2 Using the line samples permits the PTM site preci-sion determination using the same sample as the processanalyzer.5.1.4.3 The line samples can be used to test the stability ofthe sample strea
43、m during the sample collection process.5.1.5 This practice assumes the delivery of a stable repre-sentative sample from the process through the sample deliverysystem to the sample vessel.5.1.6 It is highly preferred to have the process streamquality held constant during the QC sample collection proc
44、ess.5.1.6.1 If the sample quality collected from a process unitcan change during the sample collection process then the QCsample vessel must be equipped with mixers to ensure that theQC sample is homogeneous.5.1.6.2 Systems where the QC sample is obtained from afinished homogeneous blend stock or ot
45、her bulk homogeneousQC sample may not require mixing.5.1.6.3 This practice assumes that post-mixed QC samplesdo not stratify during storage.5.1.7 In general, sample shall be collected as close aspossible to ambient temperatures.5.1.8 Collect a minimum QC sample volume sufficient for20 valid process
46、analyzer analyses for each measured param-eter of interest. Twenty (20) valid analyses for each measuredparameter of interest translate into 19 degrees of freedom. Thecollected volume shall take into account any required replicateindividual quality control measurements needed to generate avalid resu
47、lt.NOTE 5The size of the collected volume is directly related to theintroduction flow rate to be employed and the expected sample flushvolume required to ensure that the reported process analyzer resultrepresents the introduced sample. The size of the collected volume is alsorelated to the lag time
48、between the sample introduction point and theprocess analyzer as well as the process analyzer cycle time and responsetime. See Guide D7278 for details.NOTE 6Pure compounds are not recommended for use as siteprecision samples since they do not represent the inherent variability insampling of a proces
49、s stream.NOTE 7Quality control samples containing stability additives canpotentially impact the process analyzer or laboratory test method, or both.5.2 QC Sample Storage:5.2.1 The sample storage vessel shall be designed and usedso as to have no effect on the measured parameter(s) of interest.NOTE 8Knowledge of the process analyzer and PTM test principle iscritical when selecting the type and design of the sample vessel.5.2.1.1 Samples stored above or within 14C (26F) of itsflash point shall use a zero headspace storage vessel underpositive pressure.5.2.1.2 Sa
