IEC 62256:2017

Hydraulic turbines, storage pumps and pump-turbines - Rehabilitation and performance improvement

IEC 62256:2017 covers turbines, storage pumps and pump-turbines of all sizes and of the following types: Francis; Kaplan; propeller; Pelton (turbines only) and bulb turbines.
This document also identifies without detailed discussion, other powerhouse equipment that could affect or be affected by a turbine, storage pump, or pump-turbine rehabilitation. The object of this document is to assist in identifying, evaluating and executing rehabilitation and performance improvement projects for hydraulic turbines, storage pumps and pump-turbines. This document can be used by owners, consultants, and suppliers to define: needs and economics for rehabilitation and performance improvement; scope of work; specifications and evaluation of results. This document is intended to be: an aid in the decision process; an extensive source of information on rehabilitation; an identification of the key milestones in the rehabilitation process; and identification of the points to be addressed in the decision processes. This document is not intended to be a detailed engineering manual nor a maintenance document. This second edition cancels and replaces the first edition published in 2008. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: Tables 2 to 23 modified, completed and moved to Annex A; 7.3.2: subclauses moved with text changes; new subclauses on temperature, noise, galvanic corrosion, galling and replacement of components without assessment; 7.3.3: complete new subclause on residual life; Tables 29 to 32 moved to Annex C; New Annex B with assessment examples.
Key words: Turbines, Storage pump, Pump turbines, Rehabilitation, Performance.

Turbines hydrauliques, pompes d'accumulation et pompes-turbines - Réhabilitation et amélioration des performances

Spécifie comment préparer les spécifications particulières pour les transformateurs de puissance pour alimentations à découpage. Comprend une spécification particulière  cadre, qui montre la présentation et indique les essais appropriés  à considérer pour ce type de composant.

General Information

• Status: Published
• Publication Date: 29-May-2017
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 27.140 - Hydraulic energy engineering
• ICS: 29.100.10 - Magnetic components
• ICS: 29.180 - Transformers. Reactors
• Technical Committee: TC 4 - Hydraulic turbines
• Drafting Committee: MT 31 - TC 4/MT 31
• Current Stage: PPUB - Publication issued
• Start Date: 26-May-2017
• Completion Date: 30-May-2017

Relations

• Revises: IEC 62256:2008 - Hydraulic turbines, storage pumps and pump-turbines - Rehabilitation and performance improvement
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 62256 ®
Edition 2.0 2017-05
INTERNATIONAL
STANDARD
colour
inside
Hydraulic turbines, storage pumps and pump-turbines – Rehabilitation and
performance improvement
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 IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

IEC Central Office Tel.: [phone]
3, rue de Varembé Fax: [phone]
CH-1211 Geneva 20 [e-mail]
Switzerland www.iec.ch
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.

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bibliographical information on IEC International Standards, electrical terms containing 20 000 terms and definitions in
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and withdrawn publications. collected from earlier publications of IEC TC 37, 77, 86 and

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IEC 62256 ®
Edition 2.0 2017-05
INTERNATIONAL
STANDARD
colour
inside
Hydraulic turbines, storage pumps and pump-turbines – Rehabilitation and

performance improvement
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.140 ISBN 978-2-8322-4340-4

– 2 – IEC 62256:2017 © IEC 2017
CONTENTS
FOREWORD . 7
INTRODUCTION . 9
1 Scope . 10
2 Normative references . 10
3 Terms, definitions and nomenclature . 10
4 Reasons for rehabilitating . 12
4.1 General . 12
4.2 Reliability and availability increase. 14
4.3 Life extension and performance restoration . 14
4.4 Performance improvement . 14
4.5 Plant safety improvement . 14
4.6 Environmental, social and regulatory issues . 15
4.7 Maintenance and operating cost reduction . 15
4.8 Other considerations . 15
5 Phases of a rehabilitation project . 15
5.1 General . 15
5.2 Decision on organization . 17
5.2.1 General . 17
5.2.2 Expertise required . 17
5.2.3 Contract arrangement . 17
5.3 Level of assessment and determination of scope . 18
5.3.1 General . 18
5.3.2 Feasibility study – Stage 1 . 19
5.3.3 Feasibility study – Stage 2 . 19
5.3.4 Detailed study. 19
5.4 Contractual issues . 23
5.4.1 General . 23
5.4.2 Specification requirements . 24
5.4.3 Tendering documents and evaluation of tenders . 24
5.4.4 Contract award(s) . 25
5.5 Execution of project . 25
5.5.1 Model test activities . 25
5.5.2 Design, construction, installation and testing . 25
5.6 Evaluation of results and compliance with guarantees . 26
5.6.1 General . 26
5.6.2 Turbine performance evaluation. 26
5.6.3 Generator performance evaluation . 27
5.6.4 Penalties and/or bonuses assessment . 27
6 Scheduling, cost analysis and risk analysis . 27
6.1 Scheduling . 27
6.1.1 General . 27
6.1.2 Scheduling – Assessment, feasibility and detailed study phases . 28
6.1.3 Evaluating the scheduling component of alternatives . 28
6.1.4 Scheduling specification and tendering phase . 29
6.1.5 Scheduling project execution phases . 29
6.2 Economic and financial analyses . 29

6.2.1 General . 29
6.2.2 Benefit-cost analysis . 30
6.2.3 Identification of anticipated benefits . 31
6.2.4 Identification of anticipated costs and benefits . 32
6.2.5 Sensitivity analysis . 33
6.2.6 Conclusions . 34
6.3 Risk analysis. 34
6.3.1 General . 34
6.3.2 Non-achievement of performance risk . 34
6.3.3 Risk of continued operation without rehabilitation . 35
6.3.4 Extension of outage risk . 35
6.3.5 Financial risks . 35
6.3.6 Project scope risk . 36
6.3.7 Other risks . 36
7 Assessment and determination of scope of the work . 37
7.1 General . 37
7.2 Assessment of the site . 37
7.2.1 Hydrology . 37
7.2.2 Actual energy production . 38
7.2.3 Environmental, social and regulatory issues . 38
7.3 The assessment of the turbine . 39
7.3.1 General . 39
7.3.2 Turbine integrity assessment . 39
7.3.3 Residual life. 52
7.3.4 Turbine performance assessment . 61
7.4 The assessment of related equipment . 83
7.4.1 General . 83
7.4.2 Generator and thrust bearing . 84
7.4.3 Turbine governor . 84
7.4.4 Turbine inlet and outlet valves, pressure relief valve . 85
7.4.5 Auxiliary equipment . 85
7.4.6 Equipment for erection, dismantling and maintenance . 86
7.4.7 Penstock and other water passages . 86
7.4.8 Consequences of changes in plant specific hydraulic energy (head) . 86
7.4.9 Grid integration . 87
8 Hydraulic design and performance testing options . 87
8.1 General . 87
8.2 Computational hydraulic design . 88
8.2.1 General . 88
8.2.2 The role of CFD . 88
8.2.3 The process of a CFD cycle . 89
8.2.4 The accuracy of CFD results . 89
8.2.5 How to use CFD for rehabilitation . 90
8.2.6 CFD versus model tests . 91
8.3 Model tests . 91
8.3.1 General . 91
8.3.2 Model test similitude . 92
8.3.3 Model test content . 93
8.3.4 Model test application . 93

– 4 – IEC 62256:20
...

IEC 62256 ®
Edition 2.0 2017-05
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Hydraulic turbines, storage pumps and pump-turbines – Rehabilitation and
performance improvement
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 IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

IEC Central Office Tel.: [phone]
3, rue de Varembé Fax: [phone]
CH-1211 Geneva 20 [e-mail]
Switzerland www.iec.ch
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.

IEC Catalogue - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
The stand-alone application for consulting the entire The world's leading online dictionary of electronic and
bibliographical information on IEC International Standards, electrical terms containing 20 000 terms and definitions in
Technical Specifications, Technical Reports and other English and French, with equivalent terms in 16 additional
documents. Available for PC, Mac OS, Android Tablets and languages. Also known as the International Electrotechnical
iPad. Vocabulary (IEV) online.

IEC publications search - www.iec.ch/searchpub IEC Glossary - std.iec.ch/glossary
The advanced search enables to find IEC publications by a 65 000 electrotechnical terminology entries in English and
variety of criteria (reference number, text, technical French extracted from the Terms and Definitions clause of
committee,…). It also gives information on projects, replaced IEC publications issued since 2002. Some entries have been
and withdrawn publications. collected from earlier publications of IEC TC 37, 77, 86 and

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IEC 62256 ®
Edition 2.0 2017-05
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Hydraulic turbines, storage pumps and pump-turbines – Rehabilitation and

performance improvement
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.140 ISBN 978-2-8322-4433-3

– 2 – IEC 62256:2017 RLV © IEC 2017
CONTENTS
FOREWORD . 7
INTRODUCTION . 9
1 Scope . 10
2 Normative references . 10
3 Terms, definitions and nomenclature . 10
4 Reasons for rehabilitating . 12
4.1 General . 12
4.2 Reliability and availability increase. 14
4.3 Life extension and performance restoration . 14
4.4 Performance improvement . 14
4.5 Plant safety improvement . 14
4.6 Environmental, social and regulatory issues . 15
4.7 Maintenance and operating cost reduction . 15
4.8 Other considerations . 15
5 Phases of a rehabilitation project . 15
5.1 General . 15
5.2 Decision on organization . 17
5.2.1 General . 17
5.2.2 Expertise required . 17
5.2.3 Contract arrangement . 17
5.3 Level of assessment and determination of scope . 18
5.3.1 General . 18
5.3.2 Feasibility study – Stage 1 . 19
5.3.3 Feasibility study – Stage 2 . 19
5.3.4 Detailed study. 19
5.4 Contractual issues . 23
5.4.1 General . 23
5.4.2 Specification requirements . 24
5.4.3 Tendering documents and evaluation of tenders . 24
5.4.4 Contract award(s) . 25
5.5 Execution of project . 25
5.5.1 Model test activities . 25
5.5.2 Design, construction, installation and testing . 25
5.6 Evaluation of results and compliance with guarantees . 26
5.6.1 General . 26
5.6.2 Turbine performance evaluation. 26
5.6.3 Generator performance evaluation . 27
5.6.4 Penalties and/or bonuses assessment . 27
6 Scheduling, cost analysis and risk analysis . 27
6.1 Scheduling . 27
6.1.1 General . 27
6.1.2 Scheduling – Assessment, feasibility and detailed study phases . 28
6.1.3 Evaluating the scheduling component of alternatives . 28
6.1.4 Scheduling specification and tendering phase . 29
6.1.5 Scheduling project execution phases . 29
6.2 Economic and financial analyses . 29

6.2.1 General . 29
6.2.2 Benefit-cost analysis . 30
6.2.3 Identification of anticipated benefits . 31
6.2.4 Identification of anticipated costs and benefits . 32
6.2.5 Sensitivity analysis . 33
6.2.6 Conclusions . 34
6.3 Risk analysis. 34
6.3.1 General . 34
6.3.2 Non-achievement of performance risk . 34
6.3.3 Risk of continued operation without rehabilitation . 35
6.3.4 Extension of outage risk . 35
6.3.5 Financial risks . 35
6.3.6 Project scope risk . 36
6.3.7 Other risks . 36
7 Assessment and determination of scope of the work . 37
7.1 General . 37
7.2 Assessment of the site . 37
7.2.1 Hydrology . 37
7.2.2 Actual energy production . 38
7.2.3 Environmental, social and regulatory issues . 38
7.3 The assessment of the turbine . 39
7.3.1 General . 39
7.3.2 Turbine integrity assessment . 39
7.3.3 Residual life. 53
7.3.4 Turbine performance assessment . 63
7.4 The assessment of related equipment . 85
7.4.1 General . 85
7.4.2 Generator and thrust bearing . 86
7.4.3 Turbine governor . 87
7.4.4 Turbine inlet and outlet valves, pressure relief valve . 87
7.4.5 Auxiliary equipment . 87
7.4.6 Equipment for erection, dismantling and maintenance . 88
7.4.7 Penstock and other water passages . 88
7.4.8 Consequences of changes in plant specific hydraulic energy (head) . 89
7.4.9 Grid integration . 89
8 Hydraulic design and performance testing options . 89
8.1 General . 89
8.2 Computational hydraulic design . 90
8.2.1 General . 90
8.2.2 The role of CFD . 91
8.2.3 The process of a CFD cycle . 91
8.2.4 The accuracy of CFD results . 92
8.2.5 How to use CFD for rehabilitation . 92
8.2.6 CFD versus model tests . 93
8.3 Model tests . 94
8.3.1 General . 94
8.3.2 Model test similitude . 94
8.3.3 Model test content . 95
8.3.4 Model test application . 96

--------------------
...

IEC 62256 ®
Edition 2.0 2017-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Hydraulic turbines, storage pumps and pump-turbines – Rehabilitation and
performance improvement
Turbines hydrauliques, pompes d'accumulation et pompes-turbines –
Réhabilitation et amélioration des performances

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 IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

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About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.

IEC Catalogue - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
The stand-alone application for consulting the entire The world's leading online dictionary of electronic and
bibliographical information on IEC International Standards, electrical terms containing 20 000 terms and definitions in
Technical Specifications, Technical Reports and other English and French, with equivalent terms in 16 additional
documents. Available for PC, Mac OS, Android Tablets and languages. Also known as the International Electrotechnical
iPad. Vocabulary (IEV) online.

IEC publications search - www.iec.ch/searchpub IEC Glossary - std.iec.ch/glossary
The advanced search enables to find IEC publications by a 65 000 electrotechnical terminology entries in English and
variety of criteria (reference number, text, technical French extracted from the Terms and Definitions clause of
committee,…). It also gives information on projects, replaced IEC publications issued since 2002. Some entries have been
and withdrawn publications. collected from earlier publications of IEC TC 37, 77, 86 and

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IEC 62256 ®
Edition 2.0 2017-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Hydraulic turbines, storage pumps and pump-turbines – Rehabilitation and

performance improvement
Turbines hydrauliques, pompes d'accumulation et pompes-turbines –

Réhabilitation et amélioration des performances

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.140 ISBN 978-2-8322-5201-7

– 2 – IEC 62256:2017 © IEC 2017
CONTENTS
FOREWORD . 7
INTRODUCTION . 9
1 Scope . 10
2 Normative references . 10
3 Terms, definitions and nomenclature . 10
4 Reasons for rehabilitating . 12
4.1 General . 12
4.2 Reliability and availability increase. 13
4.3 Life extension and performance restoration . 13
4.4 Performance improvement . 14
4.5 Plant safety improvement . 14
4.6 Environmental, social and regulatory issues . 14
4.7 Maintenance and operating cost reduction . 15
4.8 Other considerations . 15
5 Phases of a rehabilitation project . 15
5.1 General . 15
5.2 Decision on organization . 17
5.2.1 General . 17
5.2.2 Expertise required . 17
5.2.3 Contract arrangement . 17
5.3 Level of assessment and determination of scope . 18
5.3.1 General . 18
5.3.2 Feasibility study – Stage 1 . 18
5.3.3 Feasibility study – Stage 2 . 19
5.3.4 Detailed study. 19
5.4 Contractual issues . 23
5.4.1 General . 23
5.4.2 Specification requirements . 23
5.4.3 Tendering documents and evaluation of tenders . 24
5.4.4 Contract award(s) . 24
5.5 Execution of project . 24
5.5.1 Model test activities . 24
5.5.2 Design, construction, installation and testing . 25
5.6 Evaluation of results and compliance with guarantees . 25
5.6.1 General . 25
5.6.2 Turbine performance evaluation. 25
5.6.3 Generator performance evaluation . 26
5.6.4 Penalties and/or bonuses assessment . 26
6 Scheduling, cost analysis and risk analysis . 26
6.1 Scheduling . 26
6.1.1 General . 26
6.1.2 Scheduling – Assessment, feasibility and detailed study phases . 27
6.1.3 Evaluating the scheduling component of alternatives . 27
6.1.4 Scheduling specification and tendering phase . 28
6.1.5 Scheduling project execution phases . 28
6.2 Economic and financial analyses . 29

6.2.1 General . 29
6.2.2 Benefit-cost analysis . 29
6.2.3 Identification of anticipated benefits . 30
6.2.4 Identification of anticipated costs and benefits . 31
6.2.5 Sensitivity analysis . 32
6.2.6 Conclusions . 32
6.3 Risk analysis. 32
6.3.1 General . 32
6.3.2 Non-achievement of performance risk . 33
6.3.3 Risk of continued operation without rehabilitation . 33
6.3.4 Extension of outage risk . 34
6.3.5 Financial risks . 34
6.3.6 Project scope risk . 34
6.3.7 Other risks . 35
7 Assessment and determination of scope of the work . 35
7.1 General . 35
7.2 Assessment of the site . 36
7.2.1 Hydrology . 36
7.2.2 Actual energy production . 36
7.2.3 Environmental, social and regulatory issues . 37
7.3 The assessment of the turbine . 37
7.3.1 General . 37
7.3.2 Turbine integrity assessment .
...