ASTM D6621-00(2006)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D 6621 – 00 (Reapproved 2006)
Standard Practice 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This practice serves as a practical guide for the perfor- 2.1 ASTM Standards:
mance testing of process stream analyzers specifically for D3764 Practice for Validation of Process Stream Analyzer
measuring chemical or physical characteristics of liquid aro- Systems
matic hydrocarbon materials for production or certification of D4177 Practice for Automatic Sampling of Petroleum and
these materials. The practice may be applicable to other Petroleum Products
hydrocarbon stream analyzers as well. D6122 Practice for Validation of Multivariate Process In-
1.2 Only external methods (complete substitution of the frared Spectrophotometers
process stream with a standard) of control sample introduction E456 Terminology Relating to Quality and Statistics
are included. Internal methods are beyond the scope of this E1655 Practices for Infrared Multivariate Quantitative
practice. Analysis
1.3 Methods for resetting key operational parameters of
3. Terminology
analyzers to match predefined limits are provided by vendors
and are not included in this practice. 3.1 Definitions:
3.1.1 accuracy, n—closeness of agreement between a test
1.4 Analyzer validation procedures are covered in Practices
D3764 and D6122, not in this practice. result and an accepted reference value.
3.1.2 analyzer output, n—signal that is proportional to the
1.5 Procedures for statistically interpreting data from auto-
matic sampling process stream analyzers are outlined. quality parameter being measured and suitable for input to
readout instrumentation.
1.6 The implementation of this practice requires that the
3.1.2.1 Discussion—Itmaybepneumatic,electrical,digital,
analyzer be installed according to APIRP-550 (1) , and be in
agreement with the analyzer supplier’s recommendations. etc., and expressed as psi, mv, sec., etc.
3.1.3 analyzer result, n—numerical estimate of a physical,
Also, it assumes that the analyzer is designed to monitor the
specific material parameter of interest, and that at the time of chemical, or quality parameter produced by applying the
calibration model to the analyzer output signal.
initial or periodic validation, the analyzer was operating at the
conditions specified by the manufacturer and consistently with 3.1.4 bias, n—the difference between the expectation of the
results and an accepted reference value.
the primary test method.
1.7 The units of measure used in this practice shall be the 3.1.5 control sample, n—material similar to the process
stream that is stable over long periods of time so that its
same as those applicable to the test primary method used for
analyzer validation. parametersmaybemeasuredreproduciblyinperformancetests
to characterize analyzer precision and accuracy.
1.8 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the 3.1.5.1 Discussion—May be a pure compound, standard
mixture, or a sample from the process stream. Its parameters
responsibility of the user of this standard to establish appro-
priate safety and health practices, and determine the applica- are used to plot statistical process control charts to define
analyzer precision in normal operation.
bility of regulatory limitations prior to use.
3.1.6 external performance testing, n—procedure involving
complete substitution of the process/product stream measured
This practice is under the jurisdiction of ASTM Committee D16 on Aromatic
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 For referenced ASTM standards, visit the ASTM website, www.astm.org, or
approved in 2000. Last previous edition approved in 2000 as D6621–00. 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.
D 6621 – 00 (2006)
by the analyzer with a control sample stream to measure the Chemicals. It is meant as a practical guide for persons setting
analyzer’s precision and possibly accuracy (if the control up and maintaining these analyzers in a process (non-
sample’s true value is known). laboratory) environment. They should apply it, with their
3.1.7 internal performance testing, n—procedure involving knowledge of the analyzer’s operation and of how the process
the addition of a known quantity of a standard material analyzer results are to be used, to maintain and optimize
homogeneously into the process/product stream measured by analyzer operation.
the analyzer to measure the analyzer’s precision and possibly
5. Significance and Use
accuracy (if the sample material’s true value is known).
3.1.8 linearity, n—parameter ranges where the analyzer’s 5.1 Performance testing of on-line analyzers is critical to
their proper performance within predictable levels of precision
results do and do not approximate a straight line.
3.1.9 performance testing of an analyzer, n—mechanical andaccuracy.Thispracticecanaffectproductionefficiencyand
certification of aromatic hydrocarbon materials.
and statistical procedure for routinely checking the accuracy
and precision of an analyzer’s results against historical accu-
6. System Components
racy and precision for a control sample.
6.1 Process analyzers for measuring the chemical composi-
3.1.10 precision, n—closeness of agreement of independent
tion of aromatic hydrocarbons, their purity, or physical prop-
testresultsofthesamechemicalorphysicalpropertyofagiven
erties often replace existing laboratory test methods, using the
material obtained under stipulated conditions.
same or similar chemical measurement techniques. Fig. 1
3.1.10.1 Discussion—Expressed in terms of dispersion of
shows several possible analyzer configurations for on-line
test results around the arithmetic mean, usually as variance,
process testing of aromatic hydrocarbon materials. Aromatic
standard deviation, repeatability or reproducibility, or both.
hydrocarbon stream analyzers are often based on chromatog-
3.1.11 repeatability of an analyzer, n—difference between
raphy, but they may also perform physical measurements, wet
two successive analyzer results measured in a short time
chemistry, or other methods described in new or existing
interval that would be exceeded in the long run in only 1 case
Committee D16 methods. This practice is intended to be
in 20 (5% of the time) when the analyzer is operated on a
generally applicable to any of them.
flowing sample of uniform quality.
3.1.12 reproducibility of an analyzer, n—difference be-
7. Performance Guidelines Before Calibration
tween a single result from each of two identical analyzer
7.1 At startup, validate any process analyzer against an
systems that would be exceeded in the long run in only 1 case
existing analytical method, typically in this case, one overseen
in 20 (5% of the time) when the two systems are operated at
by Committee D16.
different sites by different operators, but on identical samples.
7.2 The capability measurement (c ) for a given analyzer
3.1.13 rule violation, n—condition when a point value or m
(3) shall be less than 0.2, as defined in Eq 1:
pattern of points in a statistical process control chart statisti-
2 2
cally exceeds the defined probability of its occurrence, as
c 5s / s <0.2 (1)
m a p
defined by the Western Electric rules (2) being used.
3.1.14 spot sample, n—representative material resembling where:
s = standard deviation of the analyzer measurement, and
the stream being monitored, an identical portion of which is
a
s = standard deviation of the process.
analyzedbothinaprocessanalyzerandbyalaboratoryteston
p
The variance (standard deviation squared) of the analyzer
a non-scheduled basis for periodic validation testing.
should be less than 20% of the variance of the process, so that
3.1.14.1 Discussion—May be the same material as the
the analyzer measurement can be useful for detecting changes
control sample.
in the process. The expected capability for a process analyzer
3.1.15 validation of an analyzer, n—processtoidentifyhow
measurement may be available from the vendor for a specific
comparableananalyzer’sresultsarestatisticallytoresultsfrom
application before installation of the analyzer (advertised
the primary method, or to define how the analyzer’s results
analyzer capability). Actual process stream measurement ca-
compare to the primary method’s results in precision and
pability should be measured on the process/product stream,
accuracy.
usually after initial analyzer validation.
3.1.15.1 Discussion—Must be done when the analyzer is
7.3 Automated analyzer sampling practices for aromatic
firstconfiguredorreconfigured(initialvalidation),andthenon
hydrocarbon liquid streams shall follow those referenced in
a periodic basis (periodic validation), as described in Practice
Practice D4177.
D3764.
7.4 Determine the linearity of the process analyzer by using
3.2 For additional definitions, see Appendix X1.
at least three calibration standard materials with known
4. Summary of Practice
compositions/responses for the components of interest. Each
4.1 This practice standardizes aromatic hydrocarbon component should be present at a high, low, and medium
process-analyzer performance testing practices, or processes concentration/amount level with respect to the concentration/
formaintainingaccurateandpreciseanalyzermeasurements.It amount range expected for the parameter (analyzer operating
is used with methods for the measurement and certification of range). A plot of the component concentration/amount versus
aromatic hydrocarbon materials applied to continuous on-line analyzer response will determine if the analyzer has a linear
analyzers. These methods are generally under the control of response over the concentration range of interest. If analyzer
Committee D16 on Aromatic Hydrocarbons and Related response is nonlinear, additional calibration standards must be
D 6621 – 00 (2006)
FIG. 1 Possible Process Analyzer Configurations
D 6621 – 00 (2006)
analyzed to clearly determine the nonlinear behavior of each 8.9 SPC charts of control samples help the operator to
analyzer and component, if the analyzer is to be used in the differentiate between normal (random) and abnormal (nonran-
nonlinear range. dom) analyzer variation due to changes in analyzer operation.
7.5 If a process analyzer is to be used only for trend 8.9.1 Charts may be maintained manually or with commer-
cially available SPC software, preferably as part of the ana-
information, the data generated by it is in a form that does not
impart compositional information, but relative information lyzer data acquisition and control software.
8.9.2 Control limits should be set at three (3) sigma (stan-
only, that is, peak area, peak height, counts, millivolts, etc.
Initial validation and frequent performance testing are still darddeviations)fromthemeanvalue,warninglimitsattwo(2)
sigma, and suitable Western Electric rules (2) invoked, consis-
required to define precision, as well as to maintain proper
analyzer operation. tent with plant/facility statistical policy.
8.9.3 Allruleviolationsshallbeinvestigatedandeliminated
if possible, with all causes and actions documented with the
8. Performance Test Procedure
charts.
8.1 Determine analyzer performance using external check
8.9.4 If a cause cannot be determined, analyzer operation
samples, which are substituted for the process material stream
should continue without any parameter adjustment until the
during performance test runs.
next performance test.
8.2 Process analyzers are routinely performance tested by
8.9.5 If there are no rule violations, analyzer parameter
using control samples. These may be primary or secondary
adjustment is not needed.
standard materials, or actual portions from the process stream.
8.9.6 If a rule violation’s cause is determined and elimi-
These portions must be representative of normal process
nated,andiftheoperatorfeelsthattheanalyzer’saccuracyhas
conditions, and be stored to remain physically and chemically
changed as a result, proceed to reset analyzer parameters, as
stable over time. The control sample should be repeatedly
discussed in Section 9. If precision needs to be redefined for
analyzed by the process analyzer, and then using statistical
the analysis process, follow the procedure listed in 8.10.
process control (SPC), to define the actual analyzer result’s
8.10 To determine the repeatability of the analyzer, follow
precision.
the following procedure:
8.3 Analyzer performance test frequency can be done at a
8.10.1 Switch a control sample into the analyzer and wait
fixed time interval, based on analyzer reliability and operator
for stabilization as discussed in 8.6.
experience.Typically,oncepershift,day,orweekareused,but
8.10.2 Measure at least eleven (6) successive analyses on
it may be more or less frequent. Unscheduled control sample
the control sample over at least1hor reasonable interval on
analyses may be performed whenever the unit operator feels
the same day. The control sample should be switched into and
that something has changed in the process or process analyzer,
out of the analyzer stream for each determination.
or at a convenient time.
8.10.3 The 95% repeatability limit of the measurement for
8.4 Thecontrolsamplematerialcontainershallbelocatedat
the analyzer equals the standard deviation of these 11 succes-
a point in the process to allow for its simple and regular
sive runs multiplied by 2.8, in accordance with Terminology
introduction into the process analyzer’s sample introduction
E456.
system (if appropriate) by the process operator. A sufficient
8.10.4 Recalculate the analyzer’s control limits based on
quantity must be available for many repetitive analyses.
this new set of data, and reset the SPC chart’s parameters.
8.5 Perform an external analyzer performance test by
Continue to collect data for subsequent p
...