IEC 60953-3:2022

IEC 60953-3 ®
Edition 2.0 2022-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Rules for steam turbine thermal acceptance tests –
Part 3: Thermal performance verification tests of retrofitted steam turbines

Règles pour les essais thermiques de réception des turbines à vapeur –
Partie 3: Essais de vérification des performances thermiques des turbines à
vapeur rénovées
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IEC 60953-3 ®
Edition 2.0 2022-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Rules for steam turbine thermal acceptance tests –

Part 3: Thermal performance verification tests of retrofitted steam turbines

Règles pour les essais thermiques de réception des turbines à vapeur –

Partie 3: Essais de vérification des performances thermiques des turbines à

vapeur rénovées
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.040 ISBN 978-2-8322-3974-2

– 2 – IEC 60953-3:2022 © IEC 2022
CONTENTS
FOREWORD . 8
INTRODUCTION . 10
1 Scope . 13
1.1 General . 13
1.2 Object . 13
1.3 Matters to be considered in the contract . 13
2 Normative references . 13
3 Units, symbols, terms and definitions . 14
3.1 General . 14
3.2 Symbols, units . 14
3.3 Subscripts, superscripts and definitions . 14
3.4 Guarantee parameters . 16
3.4.1 Guidance on guarantee parameters . 16
3.4.2 Thermal efficiency . 16
3.4.3 Heat rate . 16
3.4.4 Thermodynamic efficiency . 16
3.4.5 Steam rate . 16
3.4.6 Main steam flow capacity . 16
3.4.7 Power output . 16
3.4.8 Guarantee values for extraction and mixed-pressure turbines . 16
3.4.9 Thermal Load Capacity (for Nuclear applications) . 16
3.5 Additional guarantee parameters . 16
3.5.1 General . 16
3.5.2 Cylinder isentropic efficiency – expansion in superheated region . 16
3.5.3 Cylinder isentropic efficiency – expansion involving wet region . 17
3.5.4 Pressure loss . 19
3.5.5 Flow-passing capacity (FPC) . 19
4 Guiding principles . 19
4.1 Advance planning for test . 19
4.2 Preparatory agreements and arrangements for tests . 20
4.3 Planning of the test . 20
4.3.1 Time for verification tests . 20
4.3.2 Direction of acceptance tests . 21
4.4 Preparation of the tests . 21
4.4.1 Condition of the plant. 21
4.4.2 Condition of the steam turbine . 22
4.4.3 Condition of the condenser . 22
4.4.4 Isolation of the cycle . 22
4.4.5 Checks for leakage of condenser and feed water heaters . 22
4.4.6 Cleanliness of the steam strainers . 22
4.4.7 Checking of the test measuring equipment . 22
4.5 Comparison measurements . 22
4.6 Settings for test . 23
4.6.1 Load settings . 23
4.6.2 Special settings . 23
4.7 Preliminary tests . 23
4.8 Acceptance tests . 23

4.8.1 Constancy of test conditions . 23
4.8.2 Maximum deviation and fluctuation in test conditions . 23
4.8.3 Duration of test runs and frequency of reading . 23
4.8.4 Reading of integrating measuring instruments . 23
4.8.5 Alternative methods . 23
4.8.6 Recording of tests . 23
4.8.7 Additional measurement . 23
4.8.8 Preliminary calculations . 23
4.8.9 Consistency and number of tests . 24
4.9 Repetition of acceptance tests . 24
4.10 Guidance on retrofit guarantees . 24
4.10.1 General . 24
4.10.2 Absolute guarantees . 25
4.10.3 Relative guarantees . 26
5 Measuring techniques and measuring instruments . 27
5.1 Overview. 27
5.1.1 Instrument accuracy requirements . 27
5.1.2 Measuring instruments. 27
5.1.3 Measuring uncertainty . 27
5.1.4 Calibration of instruments . 27
5.1.5 Alternative instrumentation . 27
5.1.6 Consistency of pre- and post-retrofit tests. 27
5.2 Measurement of power . 27
5.2.1 Determination of mechanical turbine output . 27
5.2.2 Measurement of boiler feed pump power . 27
5.2.3 Determination of electrical power of a turbine generator . 28
5.2.4 Measurement of electrical power . 28
5.2.5 Electrical instrument connections . 28
5.2.6 Electrical instruments . 28
5.2.7 Instrument transformers . 28
5.2.8 Determination of electrical power of pre- and post-retrofit tests . 28
5.3 Flow measurement . 28
5.3.1 Determination of flows to be measured . 28
5.3.2 Measurement of primary flow . 29
5.3.3 Installation and location of flow measuring devices . 29
5.3.4 Calibration of primary flow devices for water flow . 29
5.3.5 Inspection of flow measuring devices . 29
5.3.6 Differential pressure measurements. 30
5.3.7 Water flow fluctuation . 30
5.3.8 Secondary flow measurements . 30
5.3.9 Occasional secondary flows . 31
5.3.10 Density of water and steam . 31
5.3.11 Determination of cooling water flow of condenser . 31
5.4 Pressure measurement (excluding condensing turbine exhaust pressure) . 31
5.4.1 Pressures to be measured . 31
5.4.2 Instruments . 31
5.4.3 Main pressure measurements . 31
5.4.4 Pressure tapping holes and connecting lines . 31
5.4.5 Shut-off valves. 32

– 4 – IEC 60953-3:2022 © IEC 2022
5.4.6 Calibration of pressure measuring devices. 32
5.4.7 Atmospheric pressure . 32
5.4.8 Correction of readings . 32
5.5 Condensing turbine exhaust pressure measurement . 32
5.5.1 General . 32
5.5.2 Plane of measurement . 32
5.5.3 Pressure taps . 32
5.5.4 Manifolds . 32
5.5.5 Connecting lines . 32
5.5.6 Instruments . 32
5.5.7 Calibration . 32
5.6 Temperature measurement . 33
5.6.1 Points of temperature measurement . 33
5.6.2 Instruments . 33
5.6.3 Main temperature measurements . 33
5.6.4 Feed train temperature measurements (including bled steam) . 33
5.6.5 Condenser cooling water temperature measurement . 33
5.6.6 Thermometer wells . 33
5.6.7 Precautions to be observed in the measurement of temperature . 33
5.7 Steam quality determination . 33
5.7.1 General . 33
5.7.2 Tracer technique. 33
5.7.3 Condensing method . 33
5.7.4 Constant rate injection method . 33
5.7.5 Extraction enthalpy determined by constant rate injection method . 33
5.7.6 Tracers and their use . 34
5.7.7 Use of tracer techniques in retrofit applications . 34
5.8 Time measurement . 34
5.9 Speed measurement . 34
6 Evaluation of tests . 34
6.1 Preparation of evaluation . 34
6.2 Computation of results . 35
6.2.1 Calculation of average values of instrument readings . 35
6.2.2 Correction and conversion of averaged readings . 35
6.2.3 Checking of measured data . 35
6.2.4 Thermodynamic properties of steam and water . 36
6.2.5 Calculation of test results . 36
7 Corrections of test results and comparison with guarantee . 39
7.1 Guarantee values and guarantee conditions . 39
7.1.1 Guarantee values and guarantee conditions specific to retrofits . 39
7.2 Correction of initial steam flow capacity . 40
7.3 Correction of output . 40
7.3.1 Correction of maximum output . 40
7.3.2 Correction of Output with specified initial steam flow . 40
7.4 Correction of the thermal performance . 40
7.5 Definition and application of correction values . 40
7.6 Correction methods . 40
7.6.1 General . 40
7.6.2 Correction by heat balance calculation . 40

7.6.3 Correction by use of correction curves prepared by the manufacturer . 41
7.6.4 Tests to determine correction values . 41
7.7 Variables to be considered in the correction of specific turbine cycles. 41
7.7.1 Scope of corrections . 41
7.7.2 Turbines with regenerative feed-water heating . 41
7.7.3 Turbines which have no provision for the addition or extraction of steam
after partial expansion . 41
7.7.4 Turbines with steam extraction for purposes other than feed-water
heating (extraction turbines) . 41
7.7.5 Other types of turbine . 41
7.8 Guarantee comparison . 41
7.8.1 Tolerance and weighting . 41
7.8.2 Guarantee comparison with locus curve . 41
7.8.3 Guarantee comparison with guarantee point . 41
7.8.4 Guarantee comparison for turbines with throttle governing. 41
7.8.5 Guarantee comparison for extraction turbines . 41
7.8.6 Additional consideration for retrofit guarantee comparison . 42
7.9 Deterioration of turbine performance (ageing) . 42
7.9.1 Timing to minimise deterioration . 42
7.9.2 Correction with comparison tests . 42
7.9.3 Correction without comparison tests . 42
7.9.4 Deterioration of performance of retrofitted components . 42
8 Measuring uncertainty . 43
8.1 General . 43
8.2 Determination of measuring uncertainty of steam and water properties . 43
8.2.1 Pressure . 43
8.2.2 Temperature . 43
8.2.3 Enthalpy and enthalpy difference . 43
8.3 Calculation of measuring uncertainty of output . 43
8.3.1 Electrical measurement . 43
8.3.2 Mechanical measurement . 43
8.3.3 Additional uncertainty allowance because of unsteady load conditions . 43
8.4 Determination of measuring uncertainty of mass flow . 44
8.4.1 Measuring uncertainty of mass flow measurements . 44
8.4.2 Measuring uncertainty of multiple measurements of primary flow . 44
8.4.3 Uncertainty allowance for cycle imperfections . 44
8.5 Calculation of measuring uncertainty of results . 44
8.5.1 General . 44
8.5.2 Measuring uncertainty of thermal efficiency . 44
8.5.3 Measuring uncertainty of thermodynamic efficiency . 44
8.5.4 Uncertainty of corrections . 44
8.5.5 Guiding values for the measuring uncertainty of results . 44
8.6 Example uncertainty calculation . 44
Annex A (normative) Feedwater heater leakage and condenser leakage tests . 45
A.1 Feedwater heater leakage tests . 45
A.2 Condenser leakage tests . 45
Annex B (normative) Evaluation of multiple measurements, compatibility . 46
Annex C (normative) Mass flow balances . 47
C.1 General . 47

– 6 – IEC 60953-3:2022 © IEC 2022
C.2 Flows for further evaluations (informative) . 47
Annex D (informative) Short-statistical definition of measuring uncertainty and error
propagation in acceptance test . 48
Annex E (informative) Temperature variation method . 49
E.1 Description of the problem . 49
E.2 Possibility to determine the leakage flow . 49
E.3 Applied example . 49
Annex F (normative) Measuring uncertainty of results – retrofit application . 50
Annex G (informative) Retrofit improvement calculation – numerical examples (fossil
and nuclear) . 53
G.1 General . 53
G.2 Example of retrofitting a fossil-fired reheat turbine . 53
G.2.1 General . 53
G.2.2 HP cylinder retrofitting . 57
G.2.3 LP cylinder retrofitting with relative guarantee on heat rate(treated

separately from the HP case) . 58
G.2.4 Effect of retrofit on associated plant performance . 59
G.3 Example of retrofitting a nuclear turbine . 65
G.3.1 General . 65
G.3.2 Retrofit scenario and testing procedure . 66
G.3.3 Correction curves . 66
G.3.4 Application of correction curves . 67
G.3.5 Comparison of the measured values to the guarantees . 69
Annex H (informative) Uncertainty calculation – numerical examples (fossil and
nuclear) . 78
H.1 General . 78
H.2 Fossil case study . 78
H.2.1 General . 78
H.2.2 Evaluation . 79
H.3 Nuclear case study . 90
H.3.1 General . 90
H.3.2 Evaluation . 90

Figure 1 – Isentropic efficiency of the HP cylinder . 17
Figure 2 – LP turbine expansion line . 18
Figure G.1 – HP cylinder expansion . 54
Figure G.2 – LP cylinder expansion . 55
Figure G.3 – Original heat balance diagram (or base line) . 60
Figure G.4 – Correction curves . 61
Figure G.5 – Pre-retrofit test . 62
Figure G.6 – Pre-retrofit test: HP cylinder replaced . 63
Figure G.7 – Pre-retrofit test: LP cylinder replaced . 64
Figure G.8 – Leaving loss curve . 65
Figure G.9 – Correction curve of heat rate due to live steam pressure . 70
Figure G.10 – Correction curve of heat rate due to thermal power. 71
Figure G.11 – Correction curve of heat rate due to exhaust pressure . 71
Figure G.12 – Correction curve of heat rate due to quality of live steam . 72

Figure G.13 – Correction curve of heat rate for Δp of the moisture separator/reheaters . 72
Figure G.14 – Correction curve of heat rate due to temperature of the reheat steam . 73
Figure G.15 – Correction curve of heat rate due to quality of steam after the moisture
separator . 73
Figure G.16 – Curve of live steam pressure before the valves of the turbine as a

function of thermal power . 74
Figure G.17 – Baseline heat balance . 75
Figure G.18 – Guarantee heat balance . 76
Figure G.19 – Post-retrofit test re-calculated heat balance . 77
Figure H.1 – Instrumentation for a fossil plant . 81
Figure H.2 – Instrumentation for a nuclear plant . 92

Table 1 – Maximum deviations and fluctuations in operating conditions from specified
and relative data . 21
Table 2 – Guarantee alternatives . 25
Table 3 – Apportionment of unaccounted leakages . 36
Table 4 – Typical effects of cylinder efficiency on heat rate. 43
Table G.1 – Main parameters of the heat balances (Figure G.17 to Figure G.19) . 68
Table G.2 – Comparison between guaranteed and post-test re-calculated heat balance . 68
Table G.3 – Measured and corresponding calculated values from the post-test . 69
Table G.4 – Corrections due to differences between measured and calculated values
(from post re-calculated heat balance, Figure G.19) . 69
Table G.5 – Summary of corrections . 70
Table H.1 – Assumed total measured variable uncertainty for pressure, temperature
and generator output. 78
Table H.2 – Uncertainty percentage of calculated results at different flow

measurement uncertainty levels for a fossil plant . 80
Table H.3 – Uncertainty percentage of calculated results at different correlation levels
for a fossil plant . 80
Table H.4 – Heat Rate uncertainty of a fossil plant . 82
Table H.5 – HP isentropic efficiency uncertainty of a fossil plant . 84
Table H.6 – IP isentropic efficiency uncertainty of a fossil plant . 86
Table H.7 – LP isentropic efficiency uncertainty of a fossil plant . 88
Table H.8 – Uncertainty percentage of calculated results at different flow
measurement uncertainty levels for a nuclear plant . 91
Table H.9 – Uncertainty percentage of calculated results at different correlation levels

for a nuclear plant . 91
Table H.10 – Heat Rate uncertainty of a nuclear plant . 93
Table H.11 – HP isentropic efficiency uncertainty of a nuclear plant . 95
Table H.12 – LP isentropic efficiency uncertainty of a nuclear plant . 97

– 8 – IEC 60953-3:2022 © IEC 2022
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
RULES FOR STEAM TURBINE THERMAL ACCEPTANCE TESTS –

Part 3: Thermal performance verification tests
of retrofitted steam turbines
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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IEC 60953-3 has been prepared by subcommittee WG11/MT14: Thermal Acceptance Test, of
IEC technical committee 5: Steam turbines. It is an International Standard.
This second edition cancels and replaces the first edition published in 2001. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) The Reference Standard has changed from IEC 60953-2 to IEC 60953-0 and therefore all
changes made in IEC 60953-0 are relevant to this revised Supplementary Standard;
b) Further detailed guidance is given for guarantee types in Clause 4.10;
c) Annex H – Measuring uncertainty of results has been revised to more closely align with the
ISO/IEC Guide 98: Uncertainty of measurement;
d) Annex K – Tracer technique has been deleted;
e) Annex L – Temperature variation method has been moved to IEC 60953-0.

The text of this International Standard is based on the following documents:
Draft Report on voting
5/249/FDIS 5/252/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This part of IEC 60953 is to be read in conjunction with IEC 60953-0, and the words 'verification
test' are to be read in place of 'acceptance test'. IEC 60953-0 is taken as a Reference Standard.
A list of all parts in the IEC 60953 series, published under the general title Rules for steam
turbine thermal acceptance tests, can be found on the IEC website.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 10 – IEC 60953-3:2022 © IEC 2022
INTRODUCTION
Retrofitting steam turbines in an existing power plant frequently involves an improvement of
performance. IEC 60953-0, which defines the rules for steam turbine thermal acceptance tests
in power plants, does not cater for all the requirements specific to retrofit projects. It has,
therefore, been deemed necessary to draw up a Supplementary Standard (this document) for
guidance on the thermal acceptance tests of retrofitted steam turbines.
However, a large number of the provisions and recommendations of IEC 60953-0 are still
applicable to retrofits and, therefore, in order to avoid a repetitive and bulky document, only the
retrofit-specific addenda will be
...