SIST ISO 15239:2006
(Main)Solid mineral fuels -- Evaluation of the measurement performance of on-line analysers
Solid mineral fuels -- Evaluation of the measurement performance of on-line analysers
This International Standard sets out practices for the evaluation of the measurement performance of all types of on-line analysers for solid mineral fuel. It presents information on the different types of analyser currently available and describes procedures for the evaluation of various aspects of measurement performance, appropriate methods of test and techniques for the statistical assessment of the data collected.
Combustibles minéraux solides -- Évaluation de la performance de mesure des analyseurs en ligne
Trdna mineralna goriva – Vrednotenje natančnosti meritev on-line analizatorjev
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INTERNATIONAL ISO
STANDARD 15239
First edition
2005-04-01
Solid mineral fuels — Evaluation of the
measurement performance of on-line
analysers
Combustibles minéraux solides — Évaluation de la performance de
mesure des analyseurs en ligne
Reference number
ISO 15239:2005(E)
©
ISO 2005
---------------------- Page: 1 ----------------------
ISO 15239:2005(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.
© ISO 2005
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2005 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 15239:2005(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope. 1
2 Normative references . 1
3 Terms and definitions. 1
4 Symbols and abbreviations . 4
5 Principle . 6
6 Analyser installations . 6
7 Evaluation techniques. 8
8 Instrument stability. 9
9 Calibration. 12
10 Operational measurement performance. 15
11 Application. 20
Annex A (informative) On-line analysis techniques for solid mineral fuels . 22
Annex B (informative) Sources of measurement variance. 26
Annex C (normative) Comparative test methods. 28
Annex D (normative) Statistical assessment procedures. 36
Annex E (informative) Reference standards . 47
Annex F (informative) Specimen calculations. 48
Bibliography . 61
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ISO 15239:2005(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 15239 was prepared by Technical Committee ISO/TC 27, Solid mineral fuels, Subcommittee SC 5,
Methods of analysis.
iv © ISO 2005 – All rights reserved
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ISO 15239:2005(E)
Introduction
There are now many instruments in use which have been developed to enable the rapid on-line measurement
of solid mineral fuels for a range of parameters that indicate coal quality. The principles on which they are
based differ from those currently in use for sampling and analysis and, in effect, constitute a completely
different approach to the measurement of solid mineral fuel quality.
This standard has been developed to specify methods by which the measurement performance of such
analysers can be evaluated.
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INTERNATIONAL STANDARD ISO 15239:2005(E)
Solid mineral fuels — Evaluation of the measurement
performance of on-line analysers
1 Scope
This International Standard sets out practices for the evaluation of the measurement performance of all types
of on-line analysers for solid mineral fuel.
It presents information on the different types of analyser currently available and describes procedures for the
evaluation of various aspects of measurement performance, appropriate methods of test and techniques for
the statistical assessment of the data collected.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 1213-2, Solid mineral fuels — Vocabulary — Part 2: Terms relating to sampling, testing and analysis
ISO 1988, Hard coals — Sampling
ISO 2309, Coke — Sampling
ISO 3534-1, Statistics — Vocabulary and symbols — Part 1: Probability and general statistical terms
ISO 5069 (all parts), Brown coals and lignites — Principles of sampling
ISO 13909 (all parts):2001, Hard coal and coke — Mechanical sampling
3 Terms and definitions
For the purposes of this document, the definitions given in ISO 1213-2, ISO 3534-1 and ISO 13909-1 and the
following apply.
3.1
accuracy
closeness of agreement between an observation and the “true” value
[ISO 1213-2:1992]
3.2
analyser dynamic precision
closeness of agreement between analyser values, obtained from solid mineral fuel interrogated by the
analyser under dynamic conditions and determined by a comparative test method which eliminates random
errors attributable to the reference test method
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ISO 15239:2005(E)
3.3
analyser test method
method of analysis which gives, for a solid mineral fuel process stream, values arising from the operation of
the on-line analyser, which are estimates of the true values for specified measurands
3.4
analyser value
value of a specified measurand in a test unit that is obtained from a test carried out by an analyser test
method
3.5
backscatter geometry
arrangement of an interrogation process in which a source of incident energy and a detector system are on
the same, or adjacent, sides of the solid mineral fuel passing through the interrogation zone
3.6
bias
systematic error which leads to the average value of a series of results being persistently higher or
persistently lower than those which are obtained using a reference test method
[ISO 13909-1]
3.7
bias of scale
bias that varies as a function of the range of values measured
3.8
bias of location
bias that is constant and independent of the range of values measured
3.9
comparative dynamic precision
closeness of agreement between analyser values obtained from solid mineral fuel interrogated by the analyser
under dynamic conditions and those determined by a comparative test method, which includes random errors
attributable to the reference test method
3.10
comparative test method
method of testing in which analyser values are compared with corresponding reference values
3.11
comparison period
period of time, during which a test unit is interrogated by an analyser to give an analyser value and is sampled
by a reference test method to obtain a reference value, for a measurand
NOTE The period can be based on the typical time to produce a particular mass of solid mineral fuel, e.g. a trainload,
or on a period which coincides with operations, e.g. a shift, or some other period that is convenient to, or preferred for, a
specific evaluation procedure.
3.12
interrogation process
procedure which elicits from the solid mineral fuel process stream a measurable response related, specifically
or by inference, to the quantity of the measurand
3.13
interrogation volume
volume of the solid mineral fuel process stream in which the detected response to the interrogation process
originates
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ISO 15239:2005(E)
3.14
interrogation zone
part of the analyser installation through which the solid mineral fuel process stream passes and in which it is
subjected to the interrogation process
3.15
mainstream configuration
configuration in which the whole of the process stream to be analysed is presented to, although not
necessarily analysed by, an on-line analyser
3.16
on-line analyser
instrument for the measurement, continuously, of one or more quality indicators of solid mineral fuel while it is
undergoing processing or handling, to give data rapidly and automatically
3.17
precision
closeness of agreement between independent results obtained under stipulated conditions
[ISO 3534-1:1993]
NOTE For the purposes of this International Standard, the index of precision used is ± ts, where t is the value of
Student's t (95 % confidence level, two-sided) and s is the standard deviation of the observations about the mean value.
3.18
reference test method
method of sampling, sample preparation and analysis which is expected to give, for a solid mineral fuel
process stream, values which are unbiased estimates of the true values for specified measurands
3.19
reference value
value of a specified measurand in a test unit that is obtained from a test carried out by a reference test method
and which serves as a reference for comparison with an analyser value
NOTE For the purposes of this International Standard, reference values are considered to be conventional true
values.
3.20
sample
quantity of fuel, representative of a larger mass, for which the quality is to be determined
[ISO 13909-1]
3.21
static repeatability
closeness of agreement between replicate analyser values obtained from a reference standard in the
interrogation zone of the analyser
3.22
sub-stream configuration
configuration in which a part of the process stream to be analysed is diverted by means of a suitable sampling
system for presentation to an on-line analyser
3.23
test unit
quantity of solid mineral fuel chosen for the determination of analyser and reference values
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ISO 15239:2005(E)
3.24
transmission geometry
arrangement of an interrogation process in which a source of incident energy and a detector system are on
opposite sides of the solid mineral fuel passing through the interrogation zone.
4 Symbols and abbreviations
4.1 Mathematical
4.1.1 Primary
β regression coefficient (slope)
C Cochran's criterion
d difference between pairs of values (other than duplicates)
D duplicate 1 reference test method value
1
D duplicate 2 reference test method value
2
D mean of duplicate reference test method values
δ test statistic (see D.16)
EIV errors in variables
E(ρ) expected number of runs
F F-distribution
f static/dynamic response factor
SDR
L confidence level
C
n number of values in a set
P precision
Q test statistic (see D.16)
R reference test method value
R reference test method 1 value
1
R reference test method 2 value
2
r linear correlation coefficient
ρ run
S reference standard 1 value
1
S reference standard 2 value
2
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ISO 15239:2005(E)
s standard deviation
s the expected (guaranteed) value of precision of the analyser at one standard deviation
g
s(ρ) standard error of number of runs
σ population standard deviation
t Student's t-distribution
V variance
ν degrees of freedom
X analyser test method value
A
x any value in a set
x difference between pairs of duplicate values
dup
2
χ chi-squared distribution
Z test statistic (see D.16)
z normal deviate
4.1.2 Subscripts
A set of analyser test method values
c critical value
d set of differences
dup set of duplicate differences
Dy set of dynamic calibration values
D1 set of duplicate reference 1 test method values
D2 set of duplicate reference 2 test method values
D set of means of duplicate reference test method values
g guaranteed value
i ith value
max maximum value
0 time zero
R1 set of reference test method 1 values
R2 set of reference test method 2 values
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ISO 15239:2005(E)
St set of static calibration values
S1 set of reference standard 1 values
S2 set of reference standard 2 values
τ time
1 set 1
2 set 2
4.2 Other abbreviations
GHz gigahertz
keV kilo-electron volt
MeV mega-electron volt
RF radiofrequency
5 Principle
The performance of an on-line analyser, which has been set up and calibrated, is evaluated by procedures
that address three main aspects of analyser operation. These are the stability of the instrumentation, the
validity of the calibration and the precision of measurement under operational conditions. Instrument stability
is assessed by static measurements made, in replicate, at operationally significant intervals of time. The
installed calibration is confirmed by making simultaneous comparative measurements with the analyser and a
reference method of analysis over a range of measurand values which encompasses at least the spread of
values encountered in normal operations. Operational performance is evaluated by comparison of analyser
values with reference values obtained from separate reference procedures.
6 Analyser installations
6.1 General
There are many types of analyser, based on a variety of measurement principles and possible installation
configurations, which have been designed to measure one or more indicators of quality in a range of products
that occur in solid mineral fuel process streams.
The measurement principles on which analysers are based may be divided into four classes, as outlined in 6.2.
6.2 Analyser types
6.2.1 Absorption/scattering processes
The majority of on-line analysers for solid mineral fuel depend upon the existence of a quantitative relationship
between the measurand and the degree of absorption and/or scattering of a beam of electromagnetic
radiation or neutrons incident upon the solid mineral fuel flowing through the interrogation zone of the analyser.
Incident electromagnetic radiation, in the X-, gamma, microwave or optical energy regions, or neutron
radiation may be used; source, sample and detector may be arranged in transmission or backscatter
geometry.
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ISO 15239:2005(E)
6.2.2 Excitation processes
A second group depends on a quantitative relationship between the measurand and the emission of specific
electromagnetic radiation, (X- or gamma rays) arising as a result of excitation by an outside source of X-,
gamma or neutron radiation.
6.2.3 Natural radiation emission
In this class, the gamma radiation emitted by naturally occurring radioisotopes, present in the measurand in
relatively constant proportions, is measured.
6.2.4 Property changes
A few analysers depend upon an effect of the measurand on a selected electrical or physical property that is
measurable on line.
NOTE Annex A gives information on techniques for on-line analysis.
6.3 Methods of presentation
The solid mineral fuel to be analysed may be transported through or past the analyser on a conveyor belt or
other supporting platform, or within the confines of a container, chute or pipe. In most designs, the analyser
detection system is physically non-invasive and non-contacting with the solid mineral fuel.
The condition of the solid mineral fuel presented to the analyser varies, among the methods of analysis, from
material as it occurs in the process stream, to crushed, mixed and possibly dried material which has been
carefully profiled.
The solid mineral fuel may be presented to the analyser as a bulk solid or as a fuel-water slurry.
Two basic installation configurations for on-line analysers are possible (see Figure 1). The choice between the
two for any particular application depends on the type of analyser appropriate to the measurand and certain
parameters of the product and the plant, such as particle size and flow rate.
6.4 Installation configurations
6.4.1 Mainstream
A mainstream configuration is a system in which the whole of the process stream for which the analytical
information is required is presented to the analyser. The system can contain conditioning steps, such as
mixing and profiling, prior to interrogation by the analyser.
6.4.2 Sub-stream
A sub-stream configuration is a system in which a portion of the process stream is diverted to the analyser by
means of a suitable sampling process. The diverted portion of the stream may be subsequently subjected to
sample preparation procedures, such as crushing, dividing and conditioning before presentation to the
analyser. After interrogation the sub-stream is normally returned to the main process stream.
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ISO 15239:2005(E)
Figure 1 — Analyser configurations
7 Evaluation techniques
The procedures described in this International Standard are designed to allow the evaluation of analyser
performance in a range of situations and conditions of operation.
They are intended to be applied to an analyser after it has been set up and calibrated as recommended by the
manufacturer, with all instrumental parameters at their normal operational values for the particular installation.
In order to make a full evaluation of on-line analyser performance, it is necessary to address three
interdependent aspects of analyser operation:
instrument stability;
calibration confirmation;
operational measurement performance.
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ISO 15239:2005(E)
Since some of the measurement errors that are attributable to the analyser occur only as a result of
operations on, or interactions with, the moving process stream, it is essential for a full evaluation of
measurement performance to carry out tests under dynamic conditions.
Nevertheless, information from static tests, although more limited in its nature, is useful for monitoring some
aspects of analyser performance on a routine basis.
An understanding of the sources of variance that contribute to the errors of measurement of the analyser and
of any reference system with which it is compared, is necessary for the proper design of tests and the
evaluation of the results. Sources of variance are discussed in Annex B.
The procedures used vary with the situation but have many features in common. General considerations for
the design and operation of comparative tests are given in Annex C and techniques for the statistical analysis
of the data in Annex D.
The principal steps involved in an evaluation are as follows:
decide which aspect of analyser operation is to be evaluated (see Note);
choose an appropriate method of test and design a scheme of operation;
carry out the test procedure;
— apply appropriate statistical treatment to the data obtained from the test.
NOTE Frequently a situation will require more than one aspect to be considered (see Clause 11).
8 Instrument stability
8.1 General
It is a pre-requisite to accurate measurement by an on-line analyser that the instrumentation be stable and
contribute as little as possible to the total error of measurement. Errors arising from the instrumentation may
be random or systematic.
An estimate of random variations attributable to the instrumentation is obtained by determining the static
repeatability. A significant increase in this value with time is an indicator of changes in instrumental
characteristics that may need investigation and could lead to a worsening of the measurement performance of
the analyser. Static repeatability is also an indicator of the limiting value of accuracy achievable (base-line
performance).
Systematic instrumentation changes, which could affect the calibration if they are sufficiently large, are
indicated by changes in the level of response from reference standards. These changes can provide the
information needed to compensate for systematic instrumentation errors. In some analysers this process is
carried out automatically at intervals and a correction applied.
Random and systematic variations originating in the instrumentation can be measured simultaneously by a
relatively simple procedure that is amenable to routine use.
8.2 Objectives
The test methods and methods of data analysis described in 8.3, 8.4 and 8.5 are designed to achieve three
objectives:
to establish benchmarks against which subsequent tests for variations due to instrument instability may
be compared;
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ISO 15239:2005(E)
to determine and monitor the contribution made to the overall measurement performance of the analyser
by random variations in response originating in the instrumentation;
to monitor systematic changes in response, originating in the instrumentation, which may affect
calibration.
8.3 Test conditions
Test conditions require
a measurement period that will return an adequate precision to allow the testing of the significance of any
changes from previous measurements,
a minimum of 10 periods (see note).
NOTE A larger number of periods will increase the precision, but with diminishing returns; a practical maximum is
probably about 20.
8.4 Test procedure
Make an initial set of consecutive replicate measurements under the chosen test conditions with a reference
standard (see Notes 1 and 2) in the interrogation zone of the analyser. If it is required to detect systematic
changes, repeat with a second reference standard that offers a different level of response from the first one.
Designate these as measurements made at time 0. The levels of response from the standards chosen for the
detection of systematic changes should be representative of those which are obtained from values of
measurands close to each end of the calibration range. This will ensure that any shift of the calibration line
and/or change in slope is signalled.
After an interval, repeat the above procedure. Designate these as measurements made at time τ. A suitable
interval depends upon the usual operating programme of the analyser. The repeat test should normally be
part of a regular check routine at intervals of a shift or a day, for example. A special check should be
undertaken after any system changes (see Clause 11).
NOTE 1 Information on suitable reference standards is given in Annex E.
NOTE 2 Evaluation of instrument stability might not be possible with some designs of analysers that cannot accept a
reference standard. In others, a suitable response might be available from the empty interrogation zone.
8.5 Data analysis
8.5.1 General
Consider measurements made at time 0 to be benchmarks against which subsequent measurements made at
time τ are compared.
If, at time τ, the instrumental parameters in use when the benchmark performance was established have
changed, normalize the data obtained for the test at time τ with respect to those changes.
8.5.2 Measurement precision
8.5.2.1 For each set of observations calculate the following values:
variance, V and V (see D.2);
S1 S2
standard deviation, s and s (see D.3);
S1 S2
precision, P and P (see D.4).
S1 S2
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ISO 15239:2005(E)
8.5.2.2 Test the following for significance:
ratio of the variances, V and V (see D.5);
S1,0 S1,τ
ratio of the variances, V and V (see D.5).
S2,0 S2,τ
8.5.3 Changes in response level
8.5.3.1 For each set of observations, calculate the following:
mean values, S and S (see D.6);
1 2
differences of the means, S and S S and S .
1,0 1,τ 2,0 2,τ
8.5.3.2 Test the following for significance:
difference of the means, S and S (see D.7);
1,0 1,τ
difference of the means, S and S (see D.7).
2,0 1,τ
8.6 Results and interpretation
Record the following information:
the date of the test;
the identity of the reference standard(s) used;
relevant instrument parameters;
the conditions of the test;
the values of the individual observations;
the values calculated in 8.5;
the results of the significance tests.
The calculated value of P indicates the base-line performance of the analyser, i.e. a lower limiting value for
operational accuracy over a similar measurement period. In practice, this value cannot be achieved since
other sources of variation, outside the analyser instrumentation, also contribute to operational accuracy.
When an acceptable initial value for variance has been determined (see 11.2) or re-established (see 11.4),
designate it V . If a subsequent determination of variance, V , is not significantly different from V ,
S1,0 S1,τ S1,0
then the instrumentation may be considered to be stable with respect to its contribution to random errors in the
measurement of operational accuracy. If this is not the case, examine the instrumentation for the cause of the
change.
When acceptable initial values for variance have been determined or re-established, designate the mean
values of the observations as S and S . If, in a subsequent determination, at time τ , there is no
1,0 2,0
significant difference between S and S ,or between S and S then it can be concluded that the
,
1,0 1,τ 2,0 2,τ
instrumentation response has not changed in a way that will affect the calibration. If one or both differences
are significant, then there has been a change that could affect the calibration. Whether it will translate to a
detectable change in the calibration depends on the size of other sources of error outside the instrumentation
and the precision with which the calibration is defined. Consider confirmation of the calibration (see Clause 9).
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ISO 15239:2005(E)
9 Calibration
9.1 General
Since on-line analysers can only make measurements by reference to values obtained by some other method,
the establishment and maintenance of a sound calibration is vital to accurate measurements.
The procedures de
...
SLOVENSKI STANDARD
SIST ISO 15239:2006
01-oktober-2006
7UGQDPLQHUDOQDJRULYD±9UHGQRWHQMHQDWDQþQRVWLPHULWHYRQOLQHDQDOL]DWRUMHY
Solid mineral fuels -- Evaluation of the measurement performance of on-line analysers
Combustibles minéraux solides -- Évaluation de la performance de mesure des
analyseurs en ligne
Ta slovenski standard je istoveten z: ISO 15239:2005
ICS:
75.160.10 Trda goriva Solid fuels
SIST ISO 15239:2006 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST ISO 15239:2006
---------------------- Page: 2 ----------------------
SIST ISO 15239:2006
INTERNATIONAL ISO
STANDARD 15239
First edition
2005-04-01
Solid mineral fuels — Evaluation of the
measurement performance of on-line
analysers
Combustibles minéraux solides — Évaluation de la performance de
mesure des analyseurs en ligne
Reference number
ISO 15239:2005(E)
©
ISO 2005
---------------------- Page: 3 ----------------------
SIST ISO 15239:2006
ISO 15239:2005(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.
© ISO 2005
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2005 – All rights reserved
---------------------- Page: 4 ----------------------
SIST ISO 15239:2006
ISO 15239:2005(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope. 1
2 Normative references . 1
3 Terms and definitions. 1
4 Symbols and abbreviations . 4
5 Principle . 6
6 Analyser installations . 6
7 Evaluation techniques. 8
8 Instrument stability. 9
9 Calibration. 12
10 Operational measurement performance. 15
11 Application. 20
Annex A (informative) On-line analysis techniques for solid mineral fuels . 22
Annex B (informative) Sources of measurement variance. 26
Annex C (normative) Comparative test methods. 28
Annex D (normative) Statistical assessment procedures. 36
Annex E (informative) Reference standards . 47
Annex F (informative) Specimen calculations. 48
Bibliography . 61
© ISO 2005 – All rights reserved iii
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SIST ISO 15239:2006
ISO 15239:2005(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 15239 was prepared by Technical Committee ISO/TC 27, Solid mineral fuels, Subcommittee SC 5,
Methods of analysis.
iv © ISO 2005 – All rights reserved
---------------------- Page: 6 ----------------------
SIST ISO 15239:2006
ISO 15239:2005(E)
Introduction
There are now many instruments in use which have been developed to enable the rapid on-line measurement
of solid mineral fuels for a range of parameters that indicate coal quality. The principles on which they are
based differ from those currently in use for sampling and analysis and, in effect, constitute a completely
different approach to the measurement of solid mineral fuel quality.
This standard has been developed to specify methods by which the measurement performance of such
analysers can be evaluated.
© ISO 2005 – All rights reserved v
---------------------- Page: 7 ----------------------
SIST ISO 15239:2006
---------------------- Page: 8 ----------------------
SIST ISO 15239:2006
INTERNATIONAL STANDARD ISO 15239:2005(E)
Solid mineral fuels — Evaluation of the measurement
performance of on-line analysers
1 Scope
This International Standard sets out practices for the evaluation of the measurement performance of all types
of on-line analysers for solid mineral fuel.
It presents information on the different types of analyser currently available and describes procedures for the
evaluation of various aspects of measurement performance, appropriate methods of test and techniques for
the statistical assessment of the data collected.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 1213-2, Solid mineral fuels — Vocabulary — Part 2: Terms relating to sampling, testing and analysis
ISO 1988, Hard coals — Sampling
ISO 2309, Coke — Sampling
ISO 3534-1, Statistics — Vocabulary and symbols — Part 1: Probability and general statistical terms
ISO 5069 (all parts), Brown coals and lignites — Principles of sampling
ISO 13909 (all parts):2001, Hard coal and coke — Mechanical sampling
3 Terms and definitions
For the purposes of this document, the definitions given in ISO 1213-2, ISO 3534-1 and ISO 13909-1 and the
following apply.
3.1
accuracy
closeness of agreement between an observation and the “true” value
[ISO 1213-2:1992]
3.2
analyser dynamic precision
closeness of agreement between analyser values, obtained from solid mineral fuel interrogated by the
analyser under dynamic conditions and determined by a comparative test method which eliminates random
errors attributable to the reference test method
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3.3
analyser test method
method of analysis which gives, for a solid mineral fuel process stream, values arising from the operation of
the on-line analyser, which are estimates of the true values for specified measurands
3.4
analyser value
value of a specified measurand in a test unit that is obtained from a test carried out by an analyser test
method
3.5
backscatter geometry
arrangement of an interrogation process in which a source of incident energy and a detector system are on
the same, or adjacent, sides of the solid mineral fuel passing through the interrogation zone
3.6
bias
systematic error which leads to the average value of a series of results being persistently higher or
persistently lower than those which are obtained using a reference test method
[ISO 13909-1]
3.7
bias of scale
bias that varies as a function of the range of values measured
3.8
bias of location
bias that is constant and independent of the range of values measured
3.9
comparative dynamic precision
closeness of agreement between analyser values obtained from solid mineral fuel interrogated by the analyser
under dynamic conditions and those determined by a comparative test method, which includes random errors
attributable to the reference test method
3.10
comparative test method
method of testing in which analyser values are compared with corresponding reference values
3.11
comparison period
period of time, during which a test unit is interrogated by an analyser to give an analyser value and is sampled
by a reference test method to obtain a reference value, for a measurand
NOTE The period can be based on the typical time to produce a particular mass of solid mineral fuel, e.g. a trainload,
or on a period which coincides with operations, e.g. a shift, or some other period that is convenient to, or preferred for, a
specific evaluation procedure.
3.12
interrogation process
procedure which elicits from the solid mineral fuel process stream a measurable response related, specifically
or by inference, to the quantity of the measurand
3.13
interrogation volume
volume of the solid mineral fuel process stream in which the detected response to the interrogation process
originates
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3.14
interrogation zone
part of the analyser installation through which the solid mineral fuel process stream passes and in which it is
subjected to the interrogation process
3.15
mainstream configuration
configuration in which the whole of the process stream to be analysed is presented to, although not
necessarily analysed by, an on-line analyser
3.16
on-line analyser
instrument for the measurement, continuously, of one or more quality indicators of solid mineral fuel while it is
undergoing processing or handling, to give data rapidly and automatically
3.17
precision
closeness of agreement between independent results obtained under stipulated conditions
[ISO 3534-1:1993]
NOTE For the purposes of this International Standard, the index of precision used is ± ts, where t is the value of
Student's t (95 % confidence level, two-sided) and s is the standard deviation of the observations about the mean value.
3.18
reference test method
method of sampling, sample preparation and analysis which is expected to give, for a solid mineral fuel
process stream, values which are unbiased estimates of the true values for specified measurands
3.19
reference value
value of a specified measurand in a test unit that is obtained from a test carried out by a reference test method
and which serves as a reference for comparison with an analyser value
NOTE For the purposes of this International Standard, reference values are considered to be conventional true
values.
3.20
sample
quantity of fuel, representative of a larger mass, for which the quality is to be determined
[ISO 13909-1]
3.21
static repeatability
closeness of agreement between replicate analyser values obtained from a reference standard in the
interrogation zone of the analyser
3.22
sub-stream configuration
configuration in which a part of the process stream to be analysed is diverted by means of a suitable sampling
system for presentation to an on-line analyser
3.23
test unit
quantity of solid mineral fuel chosen for the determination of analyser and reference values
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3.24
transmission geometry
arrangement of an interrogation process in which a source of incident energy and a detector system are on
opposite sides of the solid mineral fuel passing through the interrogation zone.
4 Symbols and abbreviations
4.1 Mathematical
4.1.1 Primary
β regression coefficient (slope)
C Cochran's criterion
d difference between pairs of values (other than duplicates)
D duplicate 1 reference test method value
1
D duplicate 2 reference test method value
2
D mean of duplicate reference test method values
δ test statistic (see D.16)
EIV errors in variables
E(ρ) expected number of runs
F F-distribution
f static/dynamic response factor
SDR
L confidence level
C
n number of values in a set
P precision
Q test statistic (see D.16)
R reference test method value
R reference test method 1 value
1
R reference test method 2 value
2
r linear correlation coefficient
ρ run
S reference standard 1 value
1
S reference standard 2 value
2
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s standard deviation
s the expected (guaranteed) value of precision of the analyser at one standard deviation
g
s(ρ) standard error of number of runs
σ population standard deviation
t Student's t-distribution
V variance
ν degrees of freedom
X analyser test method value
A
x any value in a set
x difference between pairs of duplicate values
dup
2
χ chi-squared distribution
Z test statistic (see D.16)
z normal deviate
4.1.2 Subscripts
A set of analyser test method values
c critical value
d set of differences
dup set of duplicate differences
Dy set of dynamic calibration values
D1 set of duplicate reference 1 test method values
D2 set of duplicate reference 2 test method values
D set of means of duplicate reference test method values
g guaranteed value
i ith value
max maximum value
0 time zero
R1 set of reference test method 1 values
R2 set of reference test method 2 values
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St set of static calibration values
S1 set of reference standard 1 values
S2 set of reference standard 2 values
τ time
1 set 1
2 set 2
4.2 Other abbreviations
GHz gigahertz
keV kilo-electron volt
MeV mega-electron volt
RF radiofrequency
5 Principle
The performance of an on-line analyser, which has been set up and calibrated, is evaluated by procedures
that address three main aspects of analyser operation. These are the stability of the instrumentation, the
validity of the calibration and the precision of measurement under operational conditions. Instrument stability
is assessed by static measurements made, in replicate, at operationally significant intervals of time. The
installed calibration is confirmed by making simultaneous comparative measurements with the analyser and a
reference method of analysis over a range of measurand values which encompasses at least the spread of
values encountered in normal operations. Operational performance is evaluated by comparison of analyser
values with reference values obtained from separate reference procedures.
6 Analyser installations
6.1 General
There are many types of analyser, based on a variety of measurement principles and possible installation
configurations, which have been designed to measure one or more indicators of quality in a range of products
that occur in solid mineral fuel process streams.
The measurement principles on which analysers are based may be divided into four classes, as outlined in 6.2.
6.2 Analyser types
6.2.1 Absorption/scattering processes
The majority of on-line analysers for solid mineral fuel depend upon the existence of a quantitative relationship
between the measurand and the degree of absorption and/or scattering of a beam of electromagnetic
radiation or neutrons incident upon the solid mineral fuel flowing through the interrogation zone of the analyser.
Incident electromagnetic radiation, in the X-, gamma, microwave or optical energy regions, or neutron
radiation may be used; source, sample and detector may be arranged in transmission or backscatter
geometry.
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6.2.2 Excitation processes
A second group depends on a quantitative relationship between the measurand and the emission of specific
electromagnetic radiation, (X- or gamma rays) arising as a result of excitation by an outside source of X-,
gamma or neutron radiation.
6.2.3 Natural radiation emission
In this class, the gamma radiation emitted by naturally occurring radioisotopes, present in the measurand in
relatively constant proportions, is measured.
6.2.4 Property changes
A few analysers depend upon an effect of the measurand on a selected electrical or physical property that is
measurable on line.
NOTE Annex A gives information on techniques for on-line analysis.
6.3 Methods of presentation
The solid mineral fuel to be analysed may be transported through or past the analyser on a conveyor belt or
other supporting platform, or within the confines of a container, chute or pipe. In most designs, the analyser
detection system is physically non-invasive and non-contacting with the solid mineral fuel.
The condition of the solid mineral fuel presented to the analyser varies, among the methods of analysis, from
material as it occurs in the process stream, to crushed, mixed and possibly dried material which has been
carefully profiled.
The solid mineral fuel may be presented to the analyser as a bulk solid or as a fuel-water slurry.
Two basic installation configurations for on-line analysers are possible (see Figure 1). The choice between the
two for any particular application depends on the type of analyser appropriate to the measurand and certain
parameters of the product and the plant, such as particle size and flow rate.
6.4 Installation configurations
6.4.1 Mainstream
A mainstream configuration is a system in which the whole of the process stream for which the analytical
information is required is presented to the analyser. The system can contain conditioning steps, such as
mixing and profiling, prior to interrogation by the analyser.
6.4.2 Sub-stream
A sub-stream configuration is a system in which a portion of the process stream is diverted to the analyser by
means of a suitable sampling process. The diverted portion of the stream may be subsequently subjected to
sample preparation procedures, such as crushing, dividing and conditioning before presentation to the
analyser. After interrogation the sub-stream is normally returned to the main process stream.
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Figure 1 — Analyser configurations
7 Evaluation techniques
The procedures described in this International Standard are designed to allow the evaluation of analyser
performance in a range of situations and conditions of operation.
They are intended to be applied to an analyser after it has been set up and calibrated as recommended by the
manufacturer, with all instrumental parameters at their normal operational values for the particular installation.
In order to make a full evaluation of on-line analyser performance, it is necessary to address three
interdependent aspects of analyser operation:
instrument stability;
calibration confirmation;
operational measurement performance.
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Since some of the measurement errors that are attributable to the analyser occur only as a result of
operations on, or interactions with, the moving process stream, it is essential for a full evaluation of
measurement performance to carry out tests under dynamic conditions.
Nevertheless, information from static tests, although more limited in its nature, is useful for monitoring some
aspects of analyser performance on a routine basis.
An understanding of the sources of variance that contribute to the errors of measurement of the analyser and
of any reference system with which it is compared, is necessary for the proper design of tests and the
evaluation of the results. Sources of variance are discussed in Annex B.
The procedures used vary with the situation but have many features in common. General considerations for
the design and operation of comparative tests are given in Annex C and techniques for the statistical analysis
of the data in Annex D.
The principal steps involved in an evaluation are as follows:
decide which aspect of analyser operation is to be evaluated (see Note);
choose an appropriate method of test and design a scheme of operation;
carry out the test procedure;
— apply appropriate statistical treatment to the data obtained from the test.
NOTE Frequently a situation will require more than one aspect to be considered (see Clause 11).
8 Instrument stability
8.1 General
It is a pre-requisite to accurate measurement by an on-line analyser that the instrumentation be stable and
contribute as little as possible to the total error of measurement. Errors arising from the instrumentation may
be random or systematic.
An estimate of random variations attributable to the instrumentation is obtained by determining the static
repeatability. A significant increase in this value with time is an indicator of changes in instrumental
characteristics that may need investigation and could lead to a worsening of the measurement performance of
the analyser. Static repeatability is also an indicator of the limiting value of accuracy achievable (base-line
performance).
Systematic instrumentation changes, which could affect the calibration if they are sufficiently large, are
indicated by changes in the level of response from reference standards. These changes can provide the
information needed to compensate for systematic instrumentation errors. In some analysers this process is
carried out automatically at intervals and a correction applied.
Random and systematic variations originating in the instrumentation can be measured simultaneously by a
relatively simple procedure that is amenable to routine use.
8.2 Objectives
The test methods and methods of data analysis described in 8.3, 8.4 and 8.5 are designed to achieve three
objectives:
to establish benchmarks against which subsequent tests for variations due to instrument instability may
be compared;
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to determine and monitor the contribution made to the overall measurement performance of the analyser
by random variations in response originating in the instrumentation;
to monitor systematic changes in response, originating in the instrumentation, which may affect
calibration.
8.3 Test conditions
Test conditions require
a measurement period that will return an adequate precision to allow the testing of the significance of any
changes from previous measurements,
a minimum of 10 periods (see note).
NOTE A larger number of periods will increase the precision, but with diminishing returns; a practical maximum is
probably about 20.
8.4 Test procedure
Make an initial set of consecutive replicate measurements under the chosen test conditions with a reference
standard (see Notes 1 and 2) in the interrogation zone of the analyser. If it is required to detect systematic
changes, repeat with a second reference standard that offers a different level of response from the first one.
Designate these as measurements made at time 0. The levels of response from the standards chosen for the
detection of systematic changes should be representative of those which are obtained from values of
measurands close to each end of the calibration range. This will ensure that any shift of the calibration line
and/or change in slope is signalled.
After an interval, repeat the above procedure. Designate these as measurements made at time τ. A suitable
interval depends upon the usual operating programme of the analyser. The repeat test should normally be
part of a regular check routine at intervals of a shift or a day, for example. A special check should be
undertaken after any system changes (see Clause 11).
NOTE 1 Information on suitable reference standards is given in Annex E.
NOTE 2 Evaluation of instrument stability might not be possible with some designs of analysers that cannot accept a
reference standard. In others, a suitable response might be available from the empty interrogation zone.
8.5 Data analysis
8.5.1 General
Consider measurements made at time 0 to be benchmarks against which subsequent measurements made at
time τ are compared.
If, at time τ, the instrumental parameters in use when the benchmark performance was established have
changed, normalize the data obtained for the test at time τ with respect to those changes.
8.5.2 Measurement precision
8.5.2.1 For each set of observations calculate the following values:
variance, V and V (see D.2);
S1 S2
standard deviation, s and s (see D.3);
S1 S2
precision, P and P (see D.4).
S1 S2
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8.5.2.2 Test the following for significance:
ratio of the variances, V and V (see D.5);
S1,0 S1,τ
ratio of the variances, V and V (see D.5).
S2,0 S2,τ
8.5.3 Changes in response level
8.5.3.1 For each set of observations, calculate the following:
mean values, S and S (see D.6);
1 2
differences of the means, S and S S and S .
1,0 1,τ 2,0 2,τ
8.5.3.2 Test the following for significance:
difference of the means, S and S (see D.7);
1,0 1,τ
difference of the means, S and S (see D.7).
2,0 1,τ
8.6 Results and interpretation
Record the following information:
the date of the test;
the identity of the reference standard(s) used;
relevant instrument parameters;
the conditions of the test;
the values of the individual observations;
the values calculated in 8.5;
the results of the significance tests.
The calculated value of P indicates the base-line performance of the analyser, i.e. a lower limiting value for
operational accuracy over a similar measurement period. In practice, this value cannot be achieved since
other sources of variation, outside the analyser instrumentation, also contribute to operational accuracy.
When an acceptable initial value for variance has been determined (see 11.2) or re-established (see 11.4),
designate it V . If a subsequent determination of variance, V , is not significantly different from V ,
S1,0 S1,τ S1,0
then the instrumentation may be considered to be stable with respect to its contribution to random errors in the
measurement of operational accuracy. If this is not the case, examine the instrumentation for the cause of the
change.
When acceptable in
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