ASTM D6621-00(2006)e1

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:D6621 −00(Reapproved2006)
StandardPractice for
Performance Testing of Process Analyzers for Aromatic
Hydrocarbon Materials
This standard is issued under the fixed designation D6621; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
´ NOTE—Fig. 1 was corrected editorially in November 2006.
1. Scope responsibility of the user of this standard to establish appro-
priate safety and health practices, and determine the applica-
1.1 This practice serves as a practical guide for the perfor-
bility of regulatory limitations prior to use.
mance testing of process stream analyzers specifically for
measuring chemical or physical characteristics of liquid aro-
2. Referenced Documents
matic hydrocarbon materials for production or certification of
2.1 ASTM Standards:
these materials. The practice may be applicable to other
D3764PracticeforValidationofthePerformanceofProcess
hydrocarbon stream analyzers as well.
Stream Analyzer Systems
1.2 Only external methods (complete substitution of the
D4177Practice for Automatic Sampling of Petroleum and
process stream with a standard) of control sample introduction
Petroleum Products
are included. Internal methods are beyond the scope of this
D6122Practice for Validation of the Performance of Multi-
practice.
variate Online,At-Line, and Laboratory Infrared Spectro-
1.3 Methods for resetting key operational parameters of
photometer Based Analyzer Systems
analyzers to match predefined limits are provided by vendors E456Terminology Relating to Quality and Statistics
and are not included in this practice.
E1655 Practices for Infrared Multivariate Quantitative
Analysis
1.4 Analyzer validation procedures are covered in Practices
D3764 and D6122, not in this practice.
3. Terminology
1.5 Procedures for statistically interpreting data from auto-
3.1 Definitions:
matic sampling process stream analyzers are outlined.
3.1.1 accuracy, n—closeness of agreement between a test
1.6 The implementation of this practice requires that the
result and an accepted reference value.
analyzer be installed according to APIRP-550 (1) , and be in
3.1.2 analyzer output, n—signal that is proportional to the
agreement with the analyzer supplier’s recommendations.
quality parameter being measured and suitable for input to
Also, it assumes that the analyzer is designed to monitor the
readout instrumentation.
specific material parameter of interest, and that at the time of
3.1.2.1 Discussion—It may be pneumatic, electrical, digital,
initial or periodic validation, the analyzer was operating at the
etc., and expressed as psi, mv, sec., etc.
conditions specified by the manufacturer and consistently with
3.1.3 analyzer result, n—numerical estimate of a physical,
the primary test method.
chemical, or quality parameter produced by applying the
1.7 The units of measure used in this practice shall be the
calibration model to the analyzer output signal.
same as those applicable to the test primary method used for
3.1.4 bias, n—the difference between the expectation of the
analyzer validation.
results and an accepted reference value.
1.8 This standard does not purport to address all of the
3.1.5 control sample, n—material similar to the process
safety concerns, if any, associated with its use. It is the
stream that is stable over long periods of time so that its
parametersmaybemeasuredreproduciblyinperformancetests
This practice is under the jurisdiction of ASTM Committee D16 on Aromatic
to characterize analyzer precision and accuracy.
Hydrocarbons and Related Chemicals and is the direct responsibility of Subcom-
mittee D16.09 on On-Line Analysis.
Current edition approved Jan. 1, 2006. Published January 2006. Originally
approved in 2000. Last previous edition approved in 2000 as D6621–00. DOI: For referenced ASTM standards, visit the ASTM website, www.astm.org, or
10.1520/D6621-00R06E01. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof Standards volume information, refer to the standard’s Document Summary page on
this practice. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D6621−00(Reapproved2006)
FIG. 1 Possible Process Analyzer Configurations
3.1.5.1 Discussion—May be a pure compound, standard in 20 (5% of the time) when the analyzer is operated on a
mixture, or a sample from the process stream. Its parameters
flowing sample of uniform quality.
are used to plot statistical process control charts to define
3.1.12 reproducibility of an analyzer, n—differencebetween
analyzer precision in normal operation.
asingleresultfromeachoftwoidenticalanalyzersystemsthat
3.1.6 external performance testing, n—procedure involving
wouldbeexceededinthelongruninonly1casein20(5%of
complete substitution of the process/product stream measured
the time) when the two systems are operated at different sites
by the analyzer with a control sample stream to measure the
by different operators, but on identical samples.
analyzer’s precision and possibly accuracy (if the control
3.1.13 rule violation, n—condition when a point value or
sample’s true value is known).
pattern of points in a statistical process control chart statisti-
3.1.7 internal performance testing, n—procedure involving
cally exceeds the defined probability of its occurrence, as
the addition of a known quantity of a standard material
defined by the Western Electric rules (2) being used.
homogeneously into the process/product stream measured by
the analyzer to measure the analyzer’s precision and possibly
3.1.14 spot sample, n—representative material resembling
accuracy (if the sample material’s true value is known).
the stream being monitored, an identical portion of which is
3.1.8 linearity, n—parameter ranges where the analyzer’s
analyzedbothinaprocessanalyzerandbyalaboratoryteston
results do and do not approximate a straight line.
a non-scheduled basis for periodic validation testing.
3.1.9 performance testing of an analyzer, n—mechanical
3.1.14.1 Discussion—May be the same material as the
and statistical procedure for routinely checking the accuracy control sample.
and precision of an analyzer’s results against historical accu-
3.1.15 validation of an analyzer, n—process to identify how
racy and precision for a control sample.
comparableananalyzer’sresultsarestatisticallytoresultsfrom
3.1.10 precision, n—closeness of agreement of independent
the primary method, or to define how the analyzer’s results
testresultsofthesamechemicalorphysicalpropertyofagiven
compare to the primary method’s results in precision and
material obtained under stipulated conditions.
accuracy.
3.1.10.1 Discussion—Expressed in terms of dispersion of
3.1.15.1 Discussion—Must be done when the analyzer is
test results around the arithmetic mean, usually as variance,
firstconfiguredorreconfigured(initialvalidation),andthenon
standard deviation, repeatability or reproducibility, or both.
a periodic basis (periodic validation), as described in Practice
3.1.11 repeatability of an analyzer, n—difference between
D3764.
two successive analyzer results measured in a short time
interval that would be exceeded in the long run in only 1 case 3.2 For additional definitions, see Appendix X1.
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D6621−00(Reapproved2006)
4. Summary of Practice 7.4 Determine the linearity of the process analyzer by using
at least three calibration standard materials with known
4.1 This practice standardizes aromatic hydrocarbon
compositions/responses for the components of interest. Each
process-analyzer performance testing practices, or processes
component should be present at a high, low, and medium
formaintainingaccurateandpreciseanalyzermeasurements.It
concentration/amount level with respect to the concentration/
is used with methods for the measurement and certification of
amount range expected for the parameter (analyzer operating
aromatic hydrocarbon materials applied to continuous on-line
range). A plot of the component concentration/amount versus
analyzers. These methods are generally under the control of
analyzer response will determine if the analyzer has a linear
Committee D16 on Aromatic Hydrocarbons and Related
response over the concentration range of interest. If analyzer
Chemicals. It is meant as a practical guide for persons setting
response is nonlinear, additional calibration standards must be
up and maintaining these analyzers in a process (non-
analyzed to clearly determine the nonlinear behavior of each
laboratory) environment. They should apply it, with their
analyzer and component, if the analyzer is to be used in the
knowledge of the analyzer’s operation and of how the process
nonlinear range.
analyzer results are to be used, to maintain and optimize
analyzer operation. 7.5 If a process analyzer is to be used only for trend
information, the data generated by it is in a form that does not
5. Significance and Use
impart compositional information, but relative information
only, that is, peak area, peak height, counts, millivolts, etc.
5.1 Performance testing of on-line analyzers is critical to
Initial validation and frequent performance testing are still
their proper performance within predictable levels of precision
required to define precision, as well as to maintain proper
andaccuracy.Thispracticecanaffectproductionefficiencyand
analyzer operation.
certification of aromatic hydrocarbon materials.
6. System Components 8. Performance Test Procedure
6.1 Process analyzers for measuring the chemical composi-
8.1 Determine analyzer performance using external check
tion of aromatic hydrocarbons, their purity, or physical prop-
samples, which are substituted for the process material stream
erties often replace existing laboratory test methods, using the
during performance test runs.
same or similar chemical measurement techniques. Fig. 1
8.2 Process analyzers are routinely performance tested by
shows several possible analyzer configurations for on-line
using control samples. These may be primary or secondary
process testing of aromatic hydrocarbon materials. Aromatic
standard materials, or actual portions from the process stream.
hydrocarbon stream analyzers are often based on chromatog-
These portions must be representative of normal process
raphy, but they may also perform physical measurements, wet
conditions, and be stored to remain physically and chemically
chemistry, or other methods described in new or existing
stable over time. The control sample should be repeatedly
Committee D16 methods. This practice is intended to be
analyzed by the process analyzer, and then using statistical
generally applicable to any of them.
process control (SPC), to define the actual analyzer result’s
precision.
7. Performance Guidelines Before Calibration
8.3 Analyzer performance test frequency can be done at a
7.1 At startup, validate any process analyzer against an
fixed time interval, based on analyzer reliability and operator
existing analytical method, typically in this case, one overseen
experience.Typically,oncepershift,day,orweekareused,but
by Committee D16.
it may be more or less frequent. Unscheduled control sample
7.2 The capability measurement (c ) for a given analyzer
m
analyses may be performed whenever the unit operator feels
(3) shall be less than 0.2, as defined in Eq 1:
that something has changed in the process or process analyzer,
2 2
c 5s /s ,0.2 (1) or at a convenient time.
m a p
8.4 Thecontrolsamplematerialcontainershallbelocatedat
where:
a point in the process to allow for its simple and regular
s = standard deviation of the analyzer measurement, and
a
introduction into the process analyzer’s sample introduction
s = standard deviation of the process.
p
system (if appropriate) by the process operator. A sufficient
The variance (standard deviation squared) of the analyzer
quantity must be available for many repetitive analyses.
should be less than 20% of the variance of the process, so that
8.5 Perform an external analyzer performance test by
the analyzer measurement can be useful for detecting changes
in the process. The expected capability for a process analyzer switching the analyzer sample source from the process stream
tothecontrolsample,followedbysamplingandanalysisofthe
measurement may be available from the vendor for a specific
application before installation of the analyzer (advertised control sample.
analyzer capability). Actual process stream measurement ca-
8.6 Monitor the analyzer’s output from the control sample
pability should be measured on the process/product stream,
until it stabilizes, that is, the difference between successive
usually after initial analyzer validation.
readingsisatorbelowtherepeatabilityoftheanalyzer,(which
7.3 Automated analyzer sampling practices for aromatic is measured as described in 8.10). If this does not occur, the
hydrocarbon liquid streams shall follow those referenced in repeatability of the analyzer has changed and should be
Practice D4177. remeasured.
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D6621−00(Reapproved2006)
8.7 Afterstabilizationoftheanalyzer,measureatleastthree made available to persons receiving data from the analyzer.
successive results on the control sample and average the Any large changes in an analyzer’s precision should immedi-
results. Plot the average of these three results in a SPC chart ately be brought to the attention of the user of the analyzer’s
using any statistically correct method of data handling and data.
control chart construction (4).
8.11 Perform periodic analyzer validation on a scheduled
8.8 SPC charts of the control sample data shall be used to basisoveralongertime(forexample,weeklyormonthly)than
performance testing, or whenever some significant aspect of
help decide if the analyzer needs to have its response param-
eters reset, (5) or if it is working within previous statistical the analyzer has changed (see Table 1). This activity reestab-
lishes the analyzer’s statistical performance with the primary
levels and should be left alone. SPC results and operator
experience should be used to determine subsequent actions, method.
such as determining the cause for any rule violation and
9. Analyzer Parameter Adjustment
correcting it.
9.1 Adjust analyzer response parameters only when the
8.9 SPC charts of control samples help the operator to
analyzer’scontrolsampleSPCchartindicatesoneormorerule
differentiate between normal (
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