ASTM D7235-05

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D7235 – 05
Standard Guide for
Establishing a Linear Correlation Relationship Between
Analyzer and Primary Test Method Results Using Relevant
ASTM Standard Practices
This standard is issued under the fixed designation D7235; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Operation of a process stream analyzer system typically involves four sequential activities: (1)
Analyzer Calibration—When an analyzer is initially installed, or after major maintenance has been
performed, diagnostic testing will typically be performed to demonstrate that the analyzer meets
manufacturer’sspecificationsandhistoricalperformancestandards.Thesediagnostictestsmayrequire
that the analyzer be adjusted so as to provide predetermined output levels for certain reference
materials. (2) Correlation to Primary Test Method—For process stream analyzer systems that are not
primary test methods (PTM), once the diagnostic testing is completed, process stream samples will
typically be analyzed using both the analyzer system and the corresponding primary test method. A
mathematical function will be derived that relates the analyzer output to the primary test method
(PTM).TheapplicationofthismathematicalfunctiontoananalyzeroutputproducesapredictedPTM
result. (3) Initial Validation—Once the relationship between the analyzer output and primary test
method results has been established, an initial validation is performed using an independent data set
to demonstrate that the predicted PTM results agree with those from the primary test method within
the tolerances established from the Correlation activities and with no observable systemic bias. (4)
Continual Validation—During normal operation of the process analyzer system, quality assurance
testing is conducted to demonstrate that the agreement between analyzer and primary test method
results during the Initial Validation is maintained. This document provides guidance for item (2)
above.
1. Scope correlation to further improve the agreement over the complete
operating range of the analyzer. For instances where there is
1.1 Thisguidecoversageneralmethodologytodevelopand
insufficient variation in property level to apply the Practice
assess the linear relationship between results produced by a
D6708 multi-level methodology, users are referred to Practice
total analyzer system versus the results produced by the
D3764 to perform a level specific bias evaluation. The corre-
corresponding primary test method (PTM) that the analyzer
lation relationship information obtained in the application of
system is intended to emulate, using the principles and ap-
this guide is applicable only to the material type and property
proaches outlined in relevant ASTM standard practices and
range of the materials representative of those used to perform
guides.
the assessment. Users are cautioned against extrapolation of
1.2 This guide describes how the statistical methodology of
the relationship beyond the material type and property range
Practice D6708 can be employed to assess agreement between
being studied.
the PTM and analyzer results, and, if necessary, develop linear
1.3 This guide applies if the process stream analyzer system
and the primary test method are based on the same measure-
This guide is under the jurisdiction of ASTM Committee D02 on Petroleum
ment principle(s), or, if the process stream analyzer system
Products and Lubricants and is the direct responsibility of Subcommittee D02.25 on
usesadirectandwell-understoodmeasurementprinciplethatis
Performance Assessment and Validation of Process Stream Analyzer Systems for
similar to the measurement principle of the primary test
Petroleum and Petroleum Products.
Current edition approved Dec. 1, 2005. Published February 2006. DOI: 10.1520/
method. If the process stream analyzer system uses a different
D7235-05.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D7235 – 05
measurement technology from the primary test method, pro- Ignition Engine Fuels Using Mid Infrared Spectroscopy
vided that the calibration protocol for the direct output of the D6299 Practice for Applying Statistical Quality Assurance
analyzer does not require use of the PTM, this practice also and Control Charting Techniques to Evaluate Analytical
applies. Measurement System Performance
1.4 This guide does not apply if the process stream analyzer D6624 Practice for Determining a Flow-Proportioned Av-
system utilizes an indirect or mathematically modeled mea- erage Property Value (FPAPV) for a Collected Batch of
surement principle such as chemometric or multivariate analy- Process Stream Material Using Stream Analyzer Data
sis techniques where results from PTM are required for the D6708 PracticeforStatisticalAssessmentandImprovement
chemometric or multivariate model development. Users should of Expected Agreement Between Two Test Methods that
refertoPracticesE1655andD6122fordetailedcorrelationand Purport to Measure the Same Property of a Material
model validation procedures for these types of analyzer sys- E1655 Practices for Infrared Multivariate Quantitative
tems. Analysis
2.2 American Petroleum Institute Document:
NOTE 1—For example, this guide would apply for the comparison of
API TP-550 Manual on Installation of Refinery Instruments
benzenemeasurementsfromamid-infraredprocessanalyzersystembased
and Control Systems, Part II, Process Stream Analyzers
on Test Method D6277 to those obtained using PTM Test Method D3606,
2.3 ASTM Adjuncts:
a gas chromatography based test method. For each sample, the mid-
infrared spectrum is converted into a single analyzer result using meth-
ADJD6708 CompTM Version 1.0.21
odology (Test Method D6277) that is independent of the primary test
method (Test Method D3606). However, when the same analyzer uses a 3. Terminology
multivariate model to correlate the measured mid-infrared spectrum to
3.1 All of the terminology as defined in Practices D3764,
Test Method D3606 reference values using the methodology of Practice
D6122, and D6708 are adopted for this guide.
E1655, this guide does not apply. In this case, the direct output of the
analyzer is the spectrum, and the conversion of this multivariate output to
4. Significance and Use
an analyzer result require results from the primary test method.
4.1 This guide is intended to be used in conjunction with
1.5 This guide assumes that the analyzer sampling system is
Practice D3764 (Case 1) and Practice D6122 (Case 2). Meth-
fit for use, and both analyzer and lab systems are in statistical
odology in this guide can be used to determine if a linear
control during the execution of the required tasks. Procedures
correlation can improve the performance of the total analyzer
fortestingforproperfunctionoftheanalyzersamplingsystem,
system in terms of its ability to predict the results that the PTM
and ascertaining whether the systems are in statistical control
would have been if applied to the same material. This meth-
are beyond the scope of this guide.
odology, which is based on the same statistical data treatment
1.6 Software program CompTM Version 1.0.21
as Practice D6708, is use to derive the parameters of the linear
(ADJD6708) performs the necessary computations recom-
relationship and to assess the degree of improvement.
mended by this guide.
4.2 This guide provides developers or manufacturers of
1.7 This standard does not purport to address all of the
process stream analyzer systems with useful procedures for
safety concerns, if any, associated with its use. It is the
developing the capability of newly designed systems for
responsibility of the user of this standard to establish appro-
industrial applications that require reliable prediction of mea-
priate safety and health practices and determine the applica-
surements of a specific property by a primary test method of a
bility of regulatory limitations prior to use.
flowing component or product.
4.3 This guide provides purchasers of process stream ana-
2. Referenced Documents
lyzer systems with some reliable options for specifying perfor-
2.1 ASTM Standards:
mance requirements for process stream analyzer systems that
D3606 Test Method for Determination of Benzene and
are used in applications requiring reliable prediction of mea-
Toluene in Finished Motor and Aviation Gasoline by Gas
surements of a specific property by a primary test method of a
Chromatography
flowing component or product.
D3764 Practice for Validation of the Performance of Pro-
4.4 This guide provides the user of a process stream
cess Stream Analyzer Systems
analyzer system with useful information on the work process
D4177 Practice for Automatic Sampling of Petroleum and
for establishing the PTM prediction relationship and prediction
Petroleum Products
performance.
D5191 Test Method for Vapor Pressure of Petroleum Prod-
4.5 Prediction (correlation) relationship obtained in the
ucts (Mini Method)
application of this guide is applicable only to the material type
D6122 Practice for Validation of the Performance of Mul-
and property range of the materials used to perform the study.
tivariate Process Infrared Spectrophotometer Based Ana-
Selection of the property levels and the compositional charac-
lyzer Systems
teristics of the samples must be suitable for the application of
D6277 TestMethodforDeterminationofBenzeneinSpark-
the analyzer system. Users are cautioned against extrapolation
2 3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Available from American Petroleum Institute (API), 1220 L. St., NW, Wash-
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM ington, DC 20005.
Standards volume information, refer to the standard’s Document Summary page on Available from ASTM International Headquarters. Order Adjunct No.
the ASTM website. ADJD6708.
D7235 – 05
of the prediction relationship beyond the material type and 6.1.1.1 The material type and property range for which the
property range used to obtain the relationship. analyzer system results are to be assessed versus the primary
4.6 The degree-of-agreement assessment promoted in this test method is defined.
guide is based on the statistical principles articulated in 6.1.1.2 The recommended sample set design criteria for this
Practice D6708, which is purely statistical in nature. No assessment are:
attempt is made in assessing the degree of similarity in the (1) A minimum of six replicates at each major product/
analytical technique between the process analyzer and the
property level combination,
PTM;hence,resultsbetweenthePTMandanalyzerunitcanbe (2) The range of major product/property levels exceed at
highly correlated, but their measurement principles may be
least two times the published reproducibility of the PTM, and
completely different, and may not be the principal cause for
(3) A minimum of 30 total samples.
correlation. Users are therefore cautioned that a high degree of
6.1.1.3 Replication at a specific level/product combination
correlation between results does not necessarily imply a high
can be different batches of production material that are nomi-
degree of similarity in the measurement principles; nor does it
nally similar in property level (within 1.2 times the ASTM
imply a similar degree of agreement can be expected in future
reproducibility of the PTM) and composition.
measurements. In general, if sample-specific biases are de-
6.1.2 Obtain site precision information for the analyzer
tected, it suggests that the measurement principles may be
system and PTM for the material type and range defined in
different, and may affect the degree-of-agreement in future use
accordance with the procedures outlined in Practice D6299.If
of the scaling/bias-correction equation. Presence or absence of
analyzer system precision cannot be obtained using the meth-
sample-specific effect can be used as a measure of the
odology in Practice D6299, manufacturer’s published repeat-
robustnessofthecorrelationequationtosamplecompositionor
ability precision or site precision from other similar systems
matrix differences.
may be used as a surrogate. Users are cautioned to ensure
4.7 Implementation of this guide requires that the process
consistency in statistical definitions between the manufactur-
stream analyzer system complies with the following condi-
er’s published repeatability and the site precision statistic as
tions:
defined in Practice D6299 for the PTM.
4.7.1 Meets the principles set forth in PART II Process
Stream Analyzers of API TP-550,
SAMPLING METHOD
4.7.2 Meets the supplier’s recommendation,
6.1.3 Line Sampling (Preferred)—Samples meeting the re-
4.7.3 Complies with operating conditions specified by the
quirements of the sample set design criteria above are taken in
manufacturer,
accordance with Practice D3764, Line Sample Procedure, at
4.7.4 A predicted PTM algorithm has already been estab-
the crosscheck sample points of the analyzer system (see Fig.
lished if necessary, and
1), after the sample conditioning subsystem, at a frequency of
4.7.5 Meets applicable quality assurance, data collection
no more than once per day. Avoid taking this sample at the
and data telemetry protocols.
same time of day to ensure any time-of-day related effect is
4.8 After installation or major maintenance, conduct such
captured in the dataset.
diagnostic tests as recommended by the manufacturer to
6.1.4 Automated Composite Sampling—For installations
demonstrate that the analyzer meets manufacturer’s specifica-
that have automated composite sampling systems meeting the
tions,historicalperformancelevelsorboth.Ifnecessary,adjust
requirement of Practice D4177 (or equivalent), and, the appli-
the analyzer system components so as to obtain recommended
cationisintendedtoprovideapredictedPTMresultforabatch
analyzer output levels for specified reference materials.
of homogenous production material using an Flow-
4.9 Inspect the entire analyzer system to ensure it is in-
ProportionedAveragePropertyValue(FPAPV)calculatedfrom
stalled properly, is in operating condition, and is properly
the analyzer system as per Practice D6624, the correlation
adjusted after completion of the initial commissioning proce-
equation can be established using samples taken from the
dures.
composite sample accumulator at the end of each batch of
production meeting the requirements of the sample set design
5. Calibration
above. While this approach is theor
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