IEC 62364:2019

Hydraulic machines - Guidelines for dealing with hydro-abrasive erosion in Kaplan, Francis and Pelton turbines

IEC 62364:2019 gives guidelines for:
a) presenting data on hydro-abrasive erosion rates on several combinations of water quality, operating conditions, component materials, and component properties collected from a variety of hydro sites;
b) developing guidelines for the methods of minimizing hydro-abrasive erosion by modifications to hydraulic design for clean water. These guidelines do not include details such as hydraulic profile shapes which are determined by the hydraulic design experts for a given site;
c) developing guidelines based on “experience data” concerning the relative resistance of materials faced with hydro-abrasive erosion problems;
d) developing guidelines concerning the maintainability of materials with high resistance to hydro-abrasive erosion and hardcoatings;
e) developing guidelines on a recommended approach, which owners could and should take to ensure that specifications communicate the need for particular attention to this aspect of hydraulic design at their sites without establishing criteria which cannot be satisfied because the means are beyond the control of the manufacturers;
f) developing guidelines concerning operation mode of the hydro turbines in water with particle materials to increase the operation life.
It is assumed in this document that the water is not chemically aggressive. Since chemical aggressiveness is dependent upon so many possible chemical compositions, and the materials of the machine, it is beyond the scope of this document to address these issues. It is assumed in this document that cavitation is not present in the turbine. Cavitation and hydro-abrasive erosion can reinforce each other so that the resulting erosion is larger than the sum of cavitation erosion plus hydro-abrasive erosion. The quantitative relationship of the resulting hydro-abrasive erosion is not known and it is beyond the scope of this document to assess it, except to suggest that special efforts be made in the turbine design phase to minimize cavitation. Large solids (e.g. stones, wood, ice, metal objects, etc.) traveling with the water can impact turbine components and produce damage. This damage can in turn increase the flow turbulence thereby accelerating wear by both cavitation and hydro-abrasive erosion. Hydro-abrasive erosion resistant coatings can also be damaged locally by impact of large solids. It is beyond the scope of this document to address these issues. This document focuses mainly on hydroelectric powerplant equipment. Certain portions can also be applicable to other hydraulic machines. This second edition cancels and replaces the first edition published in 2013. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
a) the formula for TBO in Pelton reference model has been modified;
b) the formula for calculating sampling interval has been modified;
c) the chapter in hydro-abrasive erosion resistant coatings has been substantially modified;
d) the annex with test data for hydro-abrasive erosion resistant materials has been removed;
e) a simplified hydro-abrasive erosion evaluation has been added.
Key words: Hydraulic Machines, Hydro-Abrasive Erosion, Kaplan, Francis, Pelton Turbines.

Machines hydrauliques - Lignes directrices relatives au traitement de l'érosion hydro-abrasive des turbines Kaplan, Francis et Pelton

L'IEC 62364:2019 donne des lignes directrices pour:
a) présenter les données disponibles concernant les taux d'érosion hydro-abrasive avec diverses combinaisons de qualité de l'eau, conditions d'exploitation, matériaux et propriétés des composants; ces données ayant été obtenues sur différents sites hydroélectriques;
b) développer des lignes directrices permettant de réduire au minimum l’érosion hydro-abrasive en apportant des modifications à la conception hydraulique normalement utilisée en l’absence de particules. Ces lignes directrices n’abordent pas les détails tels que les profils hydrauliques que les spécialistes en conception hydraulique déterminent pour un site donné;
c) développer des lignes directrices établies sur le «retour d’expérience» concernant la résistance relative de matériaux confrontés aux problèmes d’érosion hydro-abrasive;
d) développer des lignes directrices concernant la maintenabilité des matériaux résistant à l'érosion hydro-abrasive et des revêtements de surface durs;
e) développer des lignes directrices relatives à la recommandation d'une méthode, que les propriétaires pourraient appliquer, et dont il convient qu'ils l'appliquent effectivement, afin de s'assurer que les spécifications montrent la nécessité d'accorder une attention toute particulière à la conception des formes hydrauliques propres à leur site sans imposer des critères qui ne peuvent être satisfaits dans la mesure où les moyens à mettre en œuvre ne sont pas maitrisables par les constructeurs;
f) développer des lignes directrices concernant le mode de fonctionnement des turbines hydroélectriques en présence de particules afin d’accroître la durée de vie.
Ce document fait l'hypothèse d’une eau chimiquement non agressive; étant donné que cette agressivité dépend des diverses compositions chimiques possibles, ainsi que des matériaux constitutifs de la machine, le domaine d'application de ce document ne traite pas de cette question. Ce document fait également l'hypothèse de l'absence de cavitation au niveau de la turbine. En effet la cavitation et l'érosion hydro-abrasive peuvent se renforcer mutuellement de sorte que l'érosion résultante est plus importante que la somme des deux. Comme aucune formulation quantitative de cette érosion résultante n’est connue, ce document n'a pas pour objet de l'évaluer, sauf pour suggérer, lors de la phase de conception de la turbine, des efforts particuliers visant à minimiser la cavitation. Des objets solides de grandes dimensions (comme des pierres, du bois, de la glace, des objets métalliques, etc.) véhiculés par l'eau peuvent percuter les composants de la turbine et les endommager. Ces dommages peuvent pour leur part accroître la turbulence de l’écoulement et accélérer l'usure par cavitation et par érosion hydro-abrasive. Les revêtements durs résistant à l’érosion hydro-abrasive peuvent également être endommagés localement suite à l'impact de ces particules de grandes dimensions. Ce document ne traite pas de ces questions. Ce document se concentre principalement sur les équipements des centrales hydroélectriques. Certaines parties de ce document peuvent également s'appliquer à d'autres machines hydrauliques. Cette deuxième édition annule et remplace la première édition publiée en 2013. Cette édition constitue une révision technique. Cette édition inclut les modifications techniques majeures suivantes par rapport à l’édition précédente:
a) La formule pour le TBO du modèle de référence des turbines Pelton a été modifiée;
b) la formule pour le calcul de l’intervalle d’échantillonnage a été modifiée;
c) le chapitre sur les revêtements résistant à l'érosion hydro-abrasive a été substantiellement modifié;
d) l’annexe sur les données test pour les matériaux résistant à l’érosion hydro-abrasive a été supprimée;
e) une évaluation simplifiée de l’érosion hydro-abrasive a été ajoutée.
Mots-clés: machines hydrauliques, l’érosion hydro-abrasive, Kaplan, Francis, turbines Pelton

General Information

• Status: Published
• Publication Date: 13-Jan-2019
• ICS: 23.100.10 - Pumps and motors
• ICS: 27.140 - Hydraulic energy engineering
• Technical Committee: TC 4 - Hydraulic turbines
• Drafting Committee: MT 29 - TC 4/MT 29
• Current Stage: PPUB - Publication issued
• Start Date: 14-Jan-2019
• Completion Date: 14-Dec-2018

Relations

• Revises: IEC 62364:2013 - Hydraulic machines - Guide for dealing with hydro-abrasive erosion in Kaplan, Francis and Pelton turbines
• Effective Date: 05-Sep-2023

Overview

IEC 62364:2019 - Hydraulic machines: Guidelines for dealing with hydro‑abrasive erosion in Kaplan, Francis and Pelton turbines provides practical, experience‑based guidance for managing wear caused by particles in turbine water flows. The standard focuses on presenting and using site data on hydro‑abrasive erosion rates, selecting and maintaining resistant materials and coatings, adapting hydraulic and mechanical design to reduce erosion for clean water environments, and establishing owner/operator practices for monitoring and specification. It assumes water is not chemically aggressive and excludes detailed treatment of cavitation, large‑solid impacts, and chemically aggressive waters.

Key topics and technical requirements

• Abrasion rate prediction and models
  • Reference and simplified hydro‑abrasive erosion evaluation methods for estimating erosion depth and time‑between‑overhaul (TBO).
  • Revised formulas (Pelton TBO, sampling interval) and a simplified evaluation added in this edition.
• Design guidance
  • Hydraulic and mechanical design strategies to minimize hydro‑abrasive erosion in Kaplan, Francis and Pelton turbines (e.g., water conveyance systems, valves, guide vane and runner design).
  • Practical recommendations for sealing, bypass design and achievable hydraulic modifications (without prescribing precise hydraulic profile shapes).
• Materials and coatings
  • Experience‑based guidance on relative resistance of materials and hardcoatings to hydro‑abrasive erosion.
  • Maintainability, repair strategies and quality control (including thermal spray WC‑CoCr guidance) for abrasion‑resistant coatings.
• Operation, monitoring and maintenance
  • Procedures for particle sampling, monitoring particle concentration/size/hardness, inspection records and criteria for overhaul.
  • Annexes with example calculation methods, sampling frequencies, inspection forms and measurement procedures.
• Assumptions and scope limits
  • Cavitation interaction and large‑solid impacts are acknowledged but not quantitatively addressed; chemical aggressiveness is out of scope.

Practical applications and users

IEC 62364:2019 is intended for:

• Turbine designers and hydraulic engineers optimizing Kaplan, Francis and Pelton turbine components for erosive environments.
• Plant owners, operators and maintenance teams setting inspection regimes, sampling plans and TBO decisions.
• Materials and coating manufacturers specifying and qualifying abrasion‑resistant solutions.
• Consultants and researchers performing erosion risk assessments or estimating lifecycle costs and refurbishment schedules.

Practical outputs include improved specification language for procurement, better prediction of wear rates, targeted inspection templates, and guidance on balancing design changes, coatings and operational strategies to extend component life.

Related standards and documents

Refer to other IEC and industry standards on hydraulic machines, material testing and coating qualification for complementary requirements (consult IEC catalogues and national committees for specific referenced documents).

Keywords: Hydraulic Machines, Hydro‑Abrasive Erosion, Kaplan Turbine, Francis Turbine, Pelton Turbine, abrasion‑resistant coatings, particle sampling, erosion prediction, turbine maintenance.

Standards Content (Sample)

IEC 62364 ®
Edition 2.0 2019-01
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Hydraulic machines – Guidelines for dealing with hydro-abrasive erosion
in kaplan, francis, and pelton turbines

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IEC 62364 ®
Edition 2.0 2019-01
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Hydraulic machines – Guidelines for dealing with hydro-abrasive erosion

in kaplan, francis, and pelton turbines

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 23.100.10; 27.140 ISBN 978-2-8322-6431-7

– 2 – IEC 62364:2019 RLV  IEC 2019
CONTENTS
FOREWORD . 6
INTRODUCTION . 8
1 Scope . 9
2 Terms, definitions and symbols. 9
3 Abrasion rate Prediction of hydro-abrasive erosion rate . 13
3.1 Model for hydro-abrasive erosion depth . 13
3.2 Reference model . 15
3.3 Simplified hydro-abrasive erosion evaluation . 15
4 Design . 16
4.1 General . 16
4.2 Selection of abrasion resistant materials with high resistance to hydro-
abrasive erosion and coating . 17
4.3 Stainless steel overlays . 18
4.4 Water conveyance system . 18
4.5 Valve . 18
4.5.1 General . 18
4.5.2 Protection (closing) of the gap between housing and trunnion. 19
4.5.3 Stops located outside the valve . 19
4.5.4 Proper capacity of inlet valve operator . 19
4.5.5 Increase bypass size to allow higher guide vane leakage . 20
4.5.6 Bypass system design . 20
4.6 Turbine . 20
4.6.1 General . 20
4.6.2 Hydraulic design . 20
4.6.3 Mechanical design . 22
5 Operation and maintenance . 29
5.1 Operation . 29
5.2 Spares and regular inspections . 30
5.3 Particle sampling and monitoring . 30
6 Abrasion resistant materials Materials with high resistance to hydro-abrasive
erosion . 32
6.1 Guidelines concerning relative abrasion hydro-abrasive erosion resistance of
materials including abrasion hydro-abrasive erosion resistant coatings . 32
6.1.1 General . 32
6.1.2 Discussion and conclusions . 33
6.2 Guidelines concerning maintainability of abrasion hydro-abrasive erosion
resistant coating materials . 34
6.2.1 Definition of terms used in this subclause . 34
6.2.2 Time between overhaul for protective coatings . 34
6.2.3 Maintenance Repair of protective coatings. 36
7 Guidelines on insertions into specifications. 37
7.1 General . 37
7.2 Properties of particles going through the turbine . 38
7.3 Size distribution of particles . 39
Mineral composition of particles for each of the above mentioned periods.
Annex A (informative) PL calculation example . 41

Annex B (informative) Measuring and recording abrasion hydro-abrasive erosion
damages . 43
B.1 Recording abrasion hydro-abrasive erosion damage . 43
B.2 Pelton runner without coating . 44
B.3 Needle tip and mouth piece without coating . 44
B.4 Pelton runner with hardcoating . 44
B.5 Needle tip, seat ring and nozzle housing with coating . 44
B.6 Francis runner and stationary labyrinth without coating . 45
B.7 Francis runner with coating and stationary labyrinth . 45
B.8 Guide vanes and facing plates without coating . 46
B.9 Guide vanes and facing plates with coating . 46
B.10 Stay vanes . 46
B.11 Francis labyrinth seals uncoated . 47
B.12 Kaplan uncoated . 47
B.13 Kaplan coated . 47
B.14 Sample data sheets . 47
B.15 Inspection record, runner blade inlet . 49
B.16 Inspection record, runner blade outlet . 50
B.17 Inspection record, runner band . 51
B.18 Inspection record, guide vanes . 52
B.19 Inspection record, facing plates and covers . 53
B.20 Inspection record, upper stationary seal . 54
B.21 Inspection record, upper rotating seal . 55
B.22 Inspection record, lower stationary seal . 56
B.23 Inspection record, lower rotating seal . 57
B.24 Inspection record, runner bucket . 58
B.25 Inspection record, Pelton runner splitter . 59
Annex C (informative) Monitoring of particle concentration and properties and water
sampling procedure . 60
C.1 General . 60
C.2 Sampling before building a power station . 60
C.3 Sampling in existing power stations . 61
C.4 Logging of samples . 61
Annex D (informative) Procedures for analysis of particle concentration, size,
hardness and shape . 62
D.1 General . 62
D.2 Particle concentration . 62
D.3 Particle size distribution . 62
D.4 Mineralogical composition of the particles . 62
D.5 Particle geometry . 63
Annex E (informative) Tests of abrasion resistant materials .
Annex E (informative) Frequency of sediment sampling . 76
Annex F (informative) Typical criteria to determine overhaul time due to abrasion
hydro-abrasive erosion . 77
F.1 General . 77
F.2 Parameters which are observable while the unit is in operation . 77
F.3 Criteria that require internal inspection of the unit . 78
Annex G (informative) Example to calculate the amount of erosion in the full model the
hydro-abrasive erosion depth . 79

– 4 – IEC 62364:2019 RLV  IEC 2019
Annex H (informative) Examples to calculate the TBO in the reference model . 81
Annex I (informative) Background for hydro-abrasive erosion depth model . 84
I.1 Theorical model Model background and derivation . 84
I.2 Introduction to the PL variable. 85
I.3 Survey results Calibration of the formula . 88
Annex J (informative) Quality control of thermal sprayed WC-CoCr . 89
J.1 Specification . 89
J.2 Quality control . 89
Bibliography . 90

Figure – Development of spiral pressure over time .
Figure 1 – Estimation of the characteristic velocities in guide vanes, W , and runner,
gv
W , as a function of turbine specific speed . 13
run
Figure 2 – Simplified evaluation of risk of hydro-abrasive erosion for first assessment . 15
Figure 3 – Example of protection of transition area . 17
Figure 4 – Runner blade overhang in refurbishment project . 19
Figure 5 – Example of "mouse ear" cavitation on runner band due to thicker blades . 20
Figure 6 – Detailed Example of design of guide vane trunnion seals . 21
Figure 7 – Example of fixing of facing plates from the dry side (bolt to the left) . 23
Figure 8 – Head cover balancing pipes with bends . 24
Figure 9 – Step labyrinth with optimized shape for hardcoating . 26
Figure 10 – Sample plot of particle concentration versus time . 29
Figure D.1 – Typical examples of particle geometry . 58
Figure I.1 – Example of flow pattern in a Pelton injector at different load . 71

Table – Form for mineral composition of particles for each of the above mentioned
periods .
Table 1 – Values of K and p for various components . 13
f
Table 2 – Overview over the feasibility for repair C on site . 32
Table 3 – Form for properties of particles going through the turbine . 34
Table 4 – Form for size distribution of particles . 35
Table A.1 – Example of documenting sample tests . 36
Table A.2 – Example of documenting sample results . 37
Table B.1 – Inspection record, runner blade inlet form . 43
Table B.2 – Inspection record, runner blade outlet form . 44
Table B.3 – Inspection record, runner band form . 45
Table B.4 – Inspection record, guide vanes form . 46
Table B.5 – Inspection record, facing plates and covers form . 47
Table B.6 – Inspection record, upper stationary seal form . 48
Table B.7 – Inspection record, upper rotating seal form . 49
Table B.8 – Inspection record, lower stationary seal form . 50
Table B.9 – Inspection record, lower rotating seal form . 51
Table B.10 – Inspection record, runner bucket . 52
Table B.11 – Inspection record, Pelton runner splitter . 53

Table G.1 – Calculations . 65
Table H.1 – Pelton turbine calculation example . 66
Table H.2 – Francis turbine calculation example . 67
Table I.1 – Data analysis of the supplied questionnaire Analysis of the calibration
constant Kf and p . 73
Table J.1 – Recommended items to include in HVOF inspection . 74

– 6 – IEC 62364:2019 RLV  IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
HYDRAULIC MACHINES –
GUIDELINES FOR DEALING WITH HYDRO-ABRASIVE
EROSION IN KAPLAN, FRANCIS, AND PELTON TURBINES

FOREWORD
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This redline version of the official IEC Standard allows the user to identify the changes
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International Standard IEC 62364 has been prepared by IEC technical committee 4: Hydraulic
turbines.
This second edition cancels and replaces the first edition published in 2013. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) the formula for TBO in Pelton reference model has been modified;
b) the formula for calculating sampling interval has been modified;
c) the chapter in hydro-abrasive erosion resistant coatings has been substantially modified;
d) the annex with test data for hydro-abrasive erosion resistant materials has been removed;
e) a simplified hydro-abrasive erosion evaluation has been added.
The text of this International Standard is based on the following documents:
FDIS Report on voting
4/351/FDIS 4/366/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://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.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 8 – IEC 62364:2019 RLV  IEC 2019
INTRODUCTION
Many owners of hydroelectric plants contend with the sometimes very aggressive
deterioration of their machines due to particle abrasion. Such owners must find the means to
communicate to potential suppliers of machines for their sites, their desire to have the
particular attention of the designers at the turbine design phase, directed to the minimization
of the severity and effects of particle abrasion.
The number of hydro power plants with hydro-abrasive erosion is increasing worldwide.
An overall approach is needed to minimize the impact of this phenomenon. Already at the
start of the planning phase an evaluation should be done to quantify the hydro-abrasive
erosion and the impact on the operation. For this, the influencing parameters and their impact
on the hydro-abrasive erosion have to be known. The necessary information for the evaluation
comprises among others the future design, the particle parameters of the water, which will
pass the turbine, the reservoir sedimentation and the power plant owner’s framework for the
future operation like availability or maximum allowable efficiency loss, before an overhaul
needs to be done.
Based on this evaluation of the hydro-abrasive erosion, an optimised solution can then be
found, by analysing all measures in relation to investments, energy production and
maintenance costs as decision parameters. Often a more hydro-abrasive erosion-resistant
design, instead of choosing the turbine design with the highest efficiency, will lead to higher
revenue. This analysis is best performed by the overall plant designer.
With regards to the machines, owners should find the means to communicate to potential
suppliers for their sites, their desire to have the particular attention of the designers at the
turbine design phase, directed to the minimization of the severity and effects of hydro-
abrasive erosion.
Limited consensus and very little quantitative data exists on the steps which the designer
could and should take to extend the useful life before major overhaul of the turbine
components when they are operated under severe particle abrasion hydro-abrasive erosion
service. This has led some owners to write into their specifications, conditions which cannot
be met with known methods and materials.

HYDRAULIC MACHINES –
GUIDELINES FOR DEALING WITH HYDRO-ABRASIVE
EROSION IN KAPLAN, FRANCIS, AND PELTON TURBINES

1 Scope
This document gives guidelines for:
a) presenting data on particle abrasion hydro-abrasive erosion rates on several combinations
of water quality, operating conditions, component materials, and component properties
collected from a variety of hydro sites;
b) developing guidelines for the methods of minimizing particle abrasion hydro-abrasive
erosion by modifications to hydraulic design for clean water. These guidelines do not
include details such as hydraulic profile shapes which should be are determined by the
hydraulic design experts for a given site;
c) developing guidelines based on “experience data” concerning the relative resistance of
materials faced with particle abrasion hydro-abrasive erosion problems;
d) developing guidelines concerning the maintainability of abrasion resistant materials with
high resistance to hydro-abrasive erosion and hard facing coatings;
e) developing guidelines on a recommended approach, which owners could and should take
to ensure that specifications communicate the need for particular attention to this aspect
of hydraulic design at their sites without establishing criteria which cannot be satisfied
because the means are beyond the control of the manufacturers;
f) developing guidelines concerning operation mode of the hydro turbines in water with
particle materials to increase the operation life.
It is assumed in this document that the water is not chemically aggressive. Since chemical
aggressiveness is dependent upon so many possible chemical compositions, and the
materials of the machine, it is beyond the scope of this document to address these issues.
It is assumed in this document that cavitation is not present in the turbine. Cavitation and
abrasion may hydro-abrasive erosion can reinforce each other so that the resulting erosion is
larger than the sum of cavitation erosion plus abrasion hydro-abrasive erosion. The
quantitative relationship of the resulting abrasion hydro-abrasive erosion is not known and it is
beyond the scope of this document to assess it, except to recommend suggest that special
efforts be made in the turbine design phase to minimize cavitation.
Large solids (e.g. stones, wood, ice, metal objects, etc.) traveling with the water may can
impact turbine components and produce damage. This damage may can in turn increase the
flow turbulence thereby accelerating wear by both cavitation and abrasion hydro-abrasive
erosion. Abrasion Hydro-abrasive erosion resistant coatings can also be damaged locally by
impact of large solids. It is beyond the scope of this document to address these issues.
This document focuses mainly on hydroelectric powerplant equipment. Certain portions may
can also be applicable to other hydraulic machines.
2 Terms, definitions and symbols
For the purposes of this document, the following terms and definitions and symbols apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
– 10 – IEC 62364:2019 RLV  IEC 2019
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
NOTE 1 Terms and definitions are also based, where relevant, on IEC TR 61364.
NOTE 2 The International System of Units (S.I.) is adopted throughout this document but other systems are
allowed.
Sub- Term Definition Symbol Unit
clause
specific specific energy of water available between the high and
2.2.1 E J/kg
hydraulic low pressure reference sections 1 and 2 of the machine
energy of a
machine
Note 1 to entry: For full information, see IEC 60193.
acceleration local value of gravitational acceleration at the place of 2
2.2.2 g m/s
due to gravity testing
Note 1 to entry: For full information, see IEC 60193.
turbine head available head at hydraulic machine terminal
2.2.3 H m
pump head
H = E/g
reference reference diameter of the hydraulic machine
2.2.4 D m
diameter
Note 1 to entry: For Pelton turbines this is the pitch
diameter, for Kaplan turbines this is the runner chamber
diameter and for Francis and Francis type pump
turbines this is the blade low pressure section diameter
at the band
Note 2 to entry: See IEC 60193 for further information.
hub diameter the diameter of runner hub for Kaplan turbines
2.2.5 D mm
h
abrasion depth of metal layer that has been removed from a
2.2.56 S mm
hydro-abrasive component due to particle abrasion material removed
erosion depth (measured perpendicular to the original surface) from a
component due to hydro-abrasive erosion
characteristic characteristic velocity defined for each machine
2.2.67 W m/s
velocity component and used to quantify particle abrasion hydro-
abrasive erosion damage
Note 1 to entry: See also 2.2.20 to 2.2.24.
particle mass concentration of all solid particles per m of water 3
2.2.78 C kg/m
concentration solution particles, i.e. the mass of solid particles per
volume of water-particle mixture
Note 1 to entry: In case the particle concentration is
expressed in parts per million (ppm) it is recommended
to use the mass of particles per mass volume of water,
so that 1 000 ppm approximately corresponds to 1
kg/m .
Sub- Term Definition Symbol Unit
clause
particle load 3
2.2.89 the particle concentration integrated over the time, T, PL kg × h/m
that is under consideration
the integral of the modified particle concentration over
time:
T
PL = C(t) × K (t) × K (t) × K (t)dt
size shape hardness
∫
N
 
≈ C × K × K × K × T 
∑
n size,n shape,n hardness,n s,n
 n=1 
C(t) = 0 if no water is flowing through the turbine.
If the unit is at standstill with pressurized spiral case
then C(t)=0 when calculating PL for runner and labyrinth
seals, but C(t)≠0 when calculating PL for guide vanes
and facing plates.
Note 1 to entry: For Francis turbines C(t) = 0 when
calculating PL for runner and labyrinth seals, if the unit
is at standstill with pressurized spiral case, but C(t) ≠ 0
when calculating PL for guide vanes and facing plates.
size factor factor that characterizes how the abrasion hydro-
2.2.910 K
size
abrasive erosion relates to the size of the abrasive
particles = median particle size dP in mm
shape factor factor that characterizes how the abrasion hydro-
2.2.1011 K
shape
abrasive erosion relates to the shape of the abrasive
particles
Note 1 to entry: See Annex D.
hardness factor that characterizes how the abrasion hydro-
2.2.1112 K
hardness
factor abrasive erosion relates to the hardness of the abrasive
particles
for 13Cr4Ni stainless steel: K = fraction of
hardness
particles harder than Mohs 4,5.
for hard coated surfaces: K = fraction of particles
hardness
harder than Mohs 7,0.
material factor factor that characterizes how the abrasion hydro-
2.2.1213 K
m
abrasive erosion relates to the material properties of the
base material
flow coefficient coefficient that characterizes how the abrasion hydro- 3,4
2.2.1314 K mm×s
f
abrasive erosion relates to the water flow around each
𝛼𝛼
kg×h×m
component
sampling time interval between two water samples taken to
2.2.1415 T h
s
interval determine the concentration of abrasive particles in the
water
yearly particle Total load (PL) for 1 year of operation, i.e. PL for T = 8 3
2.2.1516 PL kg × h/m
year
load 760 h calculated in accordance with 2.2.89
maximum 3
2.2.16 the maximum concentration of abrasive particles over a C kg/m
max
concentration
specified time interval
maximum maximum value of the integrand in the PL integral 3
2.2.17 PL kg/m
max
particle load during a specified time interval, i.e. the maximum value
of the following expression
PL = C(t )× K (t )× K (t )× K (t )

max size shape hardness
– 12 – IEC 62364:2019 RLV  IEC 2019
Sub- Term Definition Symbol Unit
clause
particle median diameter of abrasive particles in a sample, i.e.
2.2.1718 dP mm
median such diameter that the particles with size smaller than
diameter the value under consideration represent 50 % of the
total mass of particles in the sample
wear abrasion depth or volume of a reference material
2.2.18 WRI -
resistance (generally some version stainless steel) divided by the
index abrasion depth or volume of the material in question,
tested under the same conditions
o
impingement angle between the particle trajectory and the surface of
2.2.19
angle the substrate
characteristic flow through unit divided by the minimum flow area at
2.2.20 W m/s
gv
velocity in the guide vane apparatus estimated at best efficiency
Francis guide point
vanes
Q
W =
gv
a × Z × B
characteristic 0 0
velocity in
Kaplan guide
vanes
characteristic
2.2.21 speed of the water flow at guide vane location W m/s
gv
velocity in
guide vanes of
W = 0,5 × 2× E
gv
Kaplan,
Francis or
tubular
turbines
characteristic speed of the water flow at injector location
2.2.2221 W m/s
inj
velocity in
Pelton injector
W = 2× E
inj
characteristic relative velocity between the water and the runner blade
2.2.2322 W m/s
run
velocity in estimated with below formulas at best efficiency point
Kaplan or
Francis tubular
2 2
turbine runner
W = u + c
run 2 2
u = n ×π × D
Q × 4
c = (Francis)
π × D
Q × 4
c = (Kaplan)
2 2
π × (D − D )
h
Note 1 to entry: In calculation of c for Kaplan
turbines, the hub diameter has been neglected in the
interest of simplicity.
characteristic
2.2.2423 speed of the water flow at a Pelton runner W m/s
run
velocity in
relative velocity between the water and the runner
Pelton runner
bucket
W = 0,5 × 2 × E
run
discharge volume of water per unit time passing through any 3
2.2.2524 Q m /s
(volume flow section in the system
rate)
guide vane average shortest distance between adjacent guide
2.2.2625 a m
opening vanes (at a specified section if necessary)
Note 1 to entry: For further information, see
IEC 60193.
number of total number of guide vanes in a turbine
2.2.2726 z
guide vanes
Sub- Term Definition Symbol Unit
clause
distributor height of the distributor in a turbine
2.2.2827 B m
height
rotational number of revolutions per unit time
2.2.2928 n 1/s
speed
specific speed commonly used specific speed to of a hydraulic machine
2.2.3029 n rpm
s
60 × n × P
n =
s
5 / 4
H
P and H are taken in the rated operating point and given
in kW and m respectively
output output of the turbine in the rated operating point
2.2.3130 P kW
actual estimated actual depth of metal that will be removed S
2.2.3231 target, mm
abrasion from a component of the target turbine due to particle
actual
hydro-abrasive
abrasion hydro-abrasive erosion
erosion depth
of target unit
Note 1 to entry: For use with the reference model.
actual the actual hydro-abrasive erosion depth of metal that S

2.2.3332 ref, actual mm
abrasion has been removed from a component of the reference
hydro-abrasive turbine due to particle abrasion hydro-abrasive erosion
erosion depth
of reference
Note 1 to entry: For use with the reference model.
unit
number of number of nozzles in a Pelton turbine z z
2.2.3433 0 jet
nozzles
bucket width bucket width in a Pelton runner B
2.2.3534 2 mm
number of number of buckets in a Pelton runner z
2.2.3635 2
buckets
time between time between overhaul for target unit TBO
2.2.3736 target h
overhaul for
target unit
Note 1 to entry: For use with the reference model.
time between time between overhaul for reference unit TBO
2.2.3837 ref h
overhaul for
reference unit
Note 1 to entry: For use with the reference model.
turbine reference size for calculation curvature dependent RS
2.2.3938 m
reference size effects of hydro-abrasive erosion
Note 1 to entry: For Francis turbines, it is the
reference diameter, D (see 2.2.4).
Note 2 to entry: For Pelton turbines it is the inner
bucket width, B .
Note 3 to entry: For further information in the inner
bucket width, B , see IEC 60609-2.
size exponent exponent that describes the size dependant effects of p
2.2.4039
hydro-abrasive erosion in evaluating RS
exponent numerical value of 0,4-p that balances units for K α
2.2.4140 f
3 Abrasion rate Prediction of hydro-abrasive erosion rate
3.1 Model for hydro-abrasive erosion depth
The following formula can be used to estimate the hydro-abrasive erosion depth in a Francis
turbine:
– 14 – IEC 62364:2019 RLV  IEC 2019
3,4 p
S = W × PL × K × K / RS
m f
• The characteristic velocity, W, is defined in 2.2.20 to 2.2.23. If detailed data to calculate W
is not available it can be estimated based on Figure 1,
• PL, K and RS are defined in 2.2.9, 2.2.13 and 2.2.38 respectively,
m
• For uncoated components of Francis turbines K and p are taken from Table 1 below.
f
For additional information of the background for this formula please refer to Annex I. A sample
calculation is found in Annex G.
2,5
0,5
W = (0,25 + 0,003 × n ) × (2 × g × H)
run s
1,5
0,5
W = 0,55 × (2 × g × H)
gv
0,5
0 100 200 300 400 500 600 700 800
Turbine specific speed, n (using m, kW)
s
IEC
NOTE Values of n and H in this figure refer to the rated operating point while the characteristic velocities are
s
given for the points noted in Clause 2.
Figure 1 – Estimation of the characteristic velocities in guide vanes, W ,
gv
and runner, W , as a function of turbine specific speed
run
Table 1 – Values of K and p for various components
f
Component K Exponent p
f
(for RS)
-6
Francis guide vanes 1,06 × 10 0,25
-6
Francis facing plates 0,25
0,86 × 10
-6
Francis labyrinth seals 0,75
0,38 × 10
-6
Francis runner inlet 0,90 × 10 0,25
-6
Francis runner outlet 0,75
0,54 × 10
Characteristic velocity coefficient W , W
gv run
3.2 Reference model
In the reference model presented in this document the TBO of two turbines are compared to
each other. To do this the TBO of one turbine (here called reference turbine) and the
differences in the influencing parameters to another turbine (here called target turbine) have
to be known to calculate the TBO of the target turbine. Note that the same overhaul criteria
have to be applied for both the target and reference turbines.
The aim of the reference model is not to calculate the hydro-abrasive erosion depth (S).
Therefore a calibrated model for the depth is not necessary. The criteria for the TBO can be
the relative amount of damage, the efficiency loss or some other criteria but has to be the
same for both turbines.
There are a few differences in the way the formula is built up between the reference model
and the absolute model as follows:
• since the reference model does not calculate the hydro-abrasive erosion depth of
individual components, constants valid for the whole turbine are used instead of different
constants for different components;
• a larger turbine can normally withstand more abrasion hydro-abrasive erosion depth than
a small turbine before it needs overhaul. For this reason the exponent for turbine
reference size, p, is chosen as 1 in the reference model;
• for Pelton turbines, it is assumed that the critical component for overhaul is the runner. In
addition to the factors described above, the K for Pelton runners is assumed to be
f
proportional to the number of nozzles and the speed and inversely proportional to the
number of buckets;
• for Pelton turbines the reference size is taken as the bucket width, B , instead of the
runner diameter.
The TBO for the target turbine can be calculated as follows:
3,4 3,4
TBO / TBO = W / W × PL / Pl × K / K × K / K ×
target ref ref target ref target m,ref m,target f,ref f,target
p p
RS / RS
target ref
In this equation, we use the following values for the relationships:
Pelton turbines:
K / K =
f, ref f, target
z × n × z / (z × n × z ) z × z / (z × z )
0,ref ref 2,target 0,target target 2,ref jet,ref 2,target jet,target 2,ref
Francis and Kaplan turbines: K / K = 1
f,ref f,target
Size exponent: p = 1
The accuracy of the reference model might decrease when the differences between the
reference and target turbines become
...

IEC 62364 ®
Edition 2.0 2019-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Hydraulic machines – Guidelines for dealing with hydro-abrasive erosion
in kaplan, francis, and pelton turbines

Machines hydrauliques – Lignes directrices relatives
au traitement de l'érosion hydro-abrasive des turbines kaplan, francis et pelton

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IEC 62364 ®
Edition 2.0 2019-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Hydraulic machines – Guidelines for dealing with hydro-abrasive erosion

in kaplan, francis, and pelton turbines

Machines hydrauliques – Lignes directrices relatives

au traitement de l'érosion hydro-abrasive des turbines kaplan, francis et pelton

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 23.100.10; 27.140 ISBN 978-2-8322-6286-3

– 2 – IEC 62364:2019  IEC 2019
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Terms, definitions and symbols. 8
3 Prediction of hydro-abrasive erosion rate . 12
3.1 Model for hydro-abrasive erosion depth . 12
3.2 Reference model . 13
3.3 Simplified hydro-abrasive erosion evaluation . 14
4 Design . 15
4.1 General . 15
4.2 Selection of materials with high resistance to hydro-abrasive erosion and
coating . 16
4.3 Stainless steel overlays . 16
4.4 Water conveyance system . 16
4.5 Valve . 17
4.5.1 General . 17
4.5.2 Protection (closing) of the gap between housing and trunnion. 17
4.5.3 Stops located outside the valve . 17
4.5.4 Proper capacity of inlet valve operator . 18
4.5.5 Increase bypass size to allow higher guide vane leakage . 18
4.5.6 Bypass system design . 18
4.6 Turbine . 18
4.6.1 General . 18
4.6.2 Hydraulic design . 18
4.6.3 Mechanical design . 20
5 Operation and maintenance . 26
5.1 Operation . 26
5.2 Spares and regular inspections . 28
5.3 Particle sampling and monitoring . 28
6 Materials with high resistance to hydro-abrasive erosion . 29
6.1 Guidelines concerning relative hydro-abrasive erosion resistance of
materials including hydro-abrasive erosion resistant coatings . 29
6.1.1 General . 29
6.1.2 Discussion and conclusions . 30
6.2 Guidelines concerning maintainability of hydro-abrasive erosion resistant
coating materials . 30
6.2.1 Definition of terms used in this subclause . 30
6.2.2 Time between overhaul for protective coatings . 30
6.2.3 Repair of protective coatings . 31
7 Guidelines on insertions into specifications. 32
7.1 General . 32
7.2 Properties of particles going through the turbine . 33
7.3 Size distribution of particles . 34
Annex A (informative) PL calculation example . 35
Annex B (informative) Measuring and recording hydro-abrasive erosion damages . 37
B.1 Recording hydro-abrasive erosion damage . 37

B.2 Pelton runner without coating . 37
B.3 Needle tip and mouth piece without coating . 38
B.4 Pelton runner with hardcoating . 38
B.5 Needle tip, seat ring and nozzle housing with coating . 38
B.6 Francis runner and stationary labyrinth without coating . 39
B.7 Francis runner with coating and stationary labyrinth . 39
B.8 Guide vanes and facing plates without coating . 39
B.9 Guide vanes and facing plates with coating . 40
B.10 Stay vanes . 40
B.11 Francis labyrinth seals uncoated . 40
B.12 Kaplan uncoated . 40
B.13 Kaplan coated . 41
B.14 Sample data sheets . 41
B.15 Inspection record, runner blade inlet . 42
B.16 Inspection record, runner blade outlet . 43
B.17 Inspection record, runner band . 44
B.18 Inspection record, guide vanes . 45
B.19 Inspection record, facing plates and covers . 46
B.20 Inspection record, upper stationary seal . 47
B.21 Inspection record, upper rotating seal . 48
B.22 Inspection record, lower stationary seal . 49
B.23 Inspection record, lower rotating seal . 50
B.24 Inspection record, runner bucket . 51
B.25 Inspection record, Pelton runner splitter . 52
Annex C (informative) Monitoring of particle concentration and properties and water
sampling procedure . 53
C.1 General . 53
C.2 Sampling before building a power station . 53
C.3 Sampling in existing power stations . 54
C.4 Logging of samples . 54
Annex D (informative) Procedures for analysis of particle concentration, size,
hardness and shape . 55
D.1 General . 55
D.2 Particle concentration . 55
D.3 Particle size distribution . 55
D.4 Mineralogical composition . 55
D.5 Particle geometry . 55
Annex E (informative) Frequency of sediment sampling . 58
Annex F (informative) Typical criteria to determine overhaul time due to hydro-
abrasive erosion . 59
F.1 General . 59
F.2 Parameters which are observable while the unit is in operation . 59
F.3 Criteria that require internal inspection of the unit . 60
Annex G (informative) Example to calculate the hydro-abrasive erosion depth . 61
Annex H (informative) Examples to calculate the TBO in the reference model . 63
Annex I (informative) Background for hydro-abrasive erosion depth model . 66
I.1 Model background and derivation. 66
I.2 Introduction to the PL variable. 67
I.3 Calibration of the formula . 69

– 4 – IEC 62364:2019  IEC 2019
Annex J (informative) Quality control of thermal sprayed WC-CoCr . 71
J.1 Specification . 71
J.2 Quality control . 71
Bibliography . 72

Figure 1 – Estimation of the characteristic velocities in guide vanes, W , and runner,
gv
W , as a function of turbine specific speed . 13
run
Figure 2 – Simplified evaluation of risk of hydro-abrasive erosion for first assessment . 15
Figure 3 – Example of protection of transition area . 17
Figure 4 – Runner blade overhang in refurbishment project . 19
Figure 5 – Example of cavitation on runner band due to thicker blades . 20
Figure 6 – Example of design of guide vane trunnion seals . 21
Figure 7 – Example of fixing of facing plates from the dry side (bolt to the left) . 23
Figure 8 – Head cover balancing pipes with bends . 24
Figure 9 – Step labyrinth with optimized shape for hardcoating . 26
Figure 10 – Sample plot of particle concentration versus time . 28
Figure D.1 – Typical examples of particle geometry . 57
Figure I.1 – Example of flow pattern in a Pelton injector at different load . 68

Table 1 – Values of K and p for various components . 13
f
Table 2 – Overview over the feasibility for repair C on site . 31
Table 3 – Form for properties of particles going through the turbine . 33
Table 4 – Form for size distribution of particles . 34
Table A.1 – Example of documenting sample tests . 35
Table A.2 – Example of documenting sample results . 36
Table B.1 – Inspection record, runner blade inlet form . 42
Table B.2 – Inspection record, runner blade outlet form . 43
Table B.3 – Inspection record, runner band form . 44
Table B.4 – Inspection record, guide vanes form . 45
Table B.5 – Inspection record, facing plates and covers form . 46
Table B.6 – Inspection record, upper stationary seal form . 47
Table B.7 – Inspection record, upper rotating seal form . 48
Table B.8 – Inspection record, lower stationary seal form . 49
Table B.9 – Inspection record, lower rotating seal form . 50
Table B.10 – Inspection record, runner bucket . 51
Table B.11 – Inspection record, Pelton runner splitter . 52
Table G.1 – Calculations . 62
Table H.1 – Pelton turbine calculation example . 63
Table H.2 – Francis turbine calculation example . 64
Table I.1 – Analysis of the calibration constant K and p . 70
f
Table J.1 – Recommended items to include in HVOF inspection . 71

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
HYDRAULIC MACHINES –
GUIDELINES FOR DEALING WITH HYDRO-ABRASIVE
EROSION IN KAPLAN, FRANCIS, AND PELTON TURBINES

FOREWORD
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International Standard IEC 62364 has been prepared by IEC technical committee 4: Hydraulic
turbines.
This second edition cancels and replaces the first edition published in 2013. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) the formula for TBO in Pelton reference model has been modified;
b) the formula for calculating sampling interval has been modified;
c) the chapter in hydro-abrasive erosion resistant coatings has been substantially modified;
d) the annex with test data for hydro-abrasive erosion resistant materials has been removed;
e) a simplified hydro-abrasive erosion evaluation has been added.

– 6 – IEC 62364:2019  IEC 2019
The text of this International Standard is based on the following documents:
FDIS Report on voting
4/351/FDIS 4/366/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
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INTRODUCTION
The number of hydro power plants with hydro-abrasive erosion is increasing worldwide.
An overall approach is needed to minimize the impact of this phenomenon. Already at the
start of the planning phase an evaluation should be done to quantify the hydro-abrasive
erosion and the impact on the operation. For this, the influencing parameters and their impact
on the hydro-abrasive erosion have to be known. The necessary information for the evaluation
comprises among others the future design, the particle parameters of the water, which will
pass the turbine, the reservoir sedimentation and the power plant owner’s framework for the
future operation like availability or maximum allowable efficiency loss, before an overhaul
needs to be done.
Based on this evaluation of the hydro-abrasive erosion, an optimised solution can then be
found, by analysing all measures in relation to investments, energy production and
maintenance costs as decision parameters. Often a more hydro-abrasive erosion-resistant
design, instead of choosing the turbine design with the highest efficiency, will lead to higher
revenue. This analysis is best performed by the overall plant designer.
With regards to the machines, owners should find the means to communicate to potential
suppliers for their sites, their desire to have the particular attention of the designers at the
turbine design phase, directed to the minimization of the severity and effects of hydro-
abrasive erosion.
Limited consensus and very little quantitative data exists on the steps which the designer
could and should take to extend the useful life before major overhaul of the turbine
components when they are operated under severe hydro-abrasive erosion service. This has
led some owners to write into their specifications, conditions which cannot be met with known
methods and materials.
– 8 – IEC 62364:2019  IEC 2019
HYDRAULIC MACHINES –
GUIDELINES FOR DEALING WITH HYDRO-ABRASIVE
EROSION IN KAPLAN, FRANCIS, AND PELTON TURBINES

1 Scope
This document gives guidelines for:
a) presenting data on hydro-abrasive erosion rates on several combinations of water quality,
operating conditions, component materials, and component properties collected from a
variety of hydro sites;
b) developing guidelines for the methods of minimizing hydro-abrasive erosion by
modifications to hydraulic design for clean water. These guidelines do not include details
such as hydraulic profile shapes which are determined by the hydraulic design experts for
a given site;
c) developing guidelines based on “experience data” concerning the relative resistance of
materials faced with hydro-abrasive erosion problems;
d) developing guidelines concerning the maintainability of materials with high resistance to
hydro-abrasive erosion and hardcoatings;
e) developing guidelines on a recommended approach, which owners could and should take
to ensure that specifications communicate the need for particular attention to this aspect
of hydraulic design at their sites without establishing criteria which cannot be satisfied
because the means are beyond the control of the manufacturers;
f) developing guidelines concerning operation mode of the hydro turbines in water with
particle materials to increase the operation life.
It is assumed in this document that the water is not chemically aggressive. Since chemical
aggressiveness is dependent upon so many possible chemical compositions, and the
materials of the machine, it is beyond the scope of this document to address these issues.
It is assumed in this document that cavitation is not present in the turbine. Cavitation and
hydro-abrasive erosion can reinforce each other so that the resulting erosion is larger than
the sum of cavitation erosion plus hydro-abrasive erosion. The quantitative relationship of the
resulting hydro-abrasive erosion is not known and it is beyond the scope of this document to
assess it, except to suggest that special efforts be made in the turbine design phase to
minimize cavitation.
Large solids (e.g. stones, wood, ice, metal objects, etc.) traveling with the water can impact
turbine components and produce damage. This damage can in turn increase the flow
turbulence thereby accelerating wear by both cavitation and hydro-abrasive erosion. Hydro-
abrasive erosion resistant coatings can also be damaged locally by impact of large solids. It is
beyond the scope of this document to address these issues.
This document focuses mainly on hydroelectric powerplant equipment. Certain portions can
also be applicable to other hydraulic machines.
2 Terms, definitions and symbols
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
NOTE 1 Terms and definitions are also based, where relevant, on IEC TR 61364.
NOTE 2 The International System of Units (S.I.) is adopted throughout this document but other systems are
allowed.
Sub- Term Definition Symbol Unit
clause
specific specific energy of water available between the high and
2.2.1 E J/kg
hydraulic low pressure reference sections 1 and 2 of the machine
energy of a
machine
Note 1 to entry: For full information, see IEC 60193.
acceleration local value of gravitational acceleration at the place of 2
2.2.2 g m/s
due to gravity testing
Note 1 to entry: For full information, see IEC 60193.
turbine head available head at hydraulic machine terminal
2.2.3 H m
pump head
H = E/g
reference reference diameter of the hydraulic machine
2.2.4 D m
diameter
Note 1 to entry: For Pelton turbines this is the pitch
diameter, for Kaplan turbines this is the runner chamber
diameter and for Francis and Francis type pump
turbines this is the blade low pressure section diameter
at the band
Note 2 to entry: See IEC 60193 for further information.
hub diameter the diameter of runner hub for Kaplan turbines
2.2.5 D mm
h
hydro-abrasive depth of material removed (measured perpendicular to
2.2.6 S mm
erosion depth the original surface) from a component due to hydro-
abrasive erosion
characteristic characteristic velocity defined for each machine
2.2.7 W m/s
velocity component and used to quantify hydro-abrasive erosion
damage
Note 1 to entry: See also 2.2.20 to 2.2.24.
particle mass concentration of particles, i.e. the mass of solid 3
2.2.8 C kg/m
concentration particles per volume of water-particle mixture
Note 1 to entry: In case the particle concentration is
expressed in parts per million (ppm) it is recommended
to use the mass of particles per volume of water, so that
1 000 ppm approximately corresponds to 1 kg/m .

– 10 – IEC 62364:2019  IEC 2019
Sub- Term Definition Symbol Unit
clause
particle load the integral of the modified particle concentration over 3
2.2.9 PL kg × h/m
time:
T
PL = C(t) × K (t) × K (t) × K (t)dt
size shape hardness
∫
N
 
≈ C × K × K × K × T
 
∑
n size,n shape,n hardness,n s,n
n=1
 
C(t) = 0 if no water is flowing through the turbine.
Note 1 to entry: For Francis turbines C(t) = 0 when
calculating PL for runner and labyrinth seals, if the unit
is at standstill with pressurized spiral case, but C(t) ≠ 0
when calculating PL for guide vanes and facing plates.
size factor factor that characterizes how the hydro-abrasive erosion
2.2.10 K
size
relates to the size of the abrasive particles = median
particle size dP in mm
shape factor factor that characterizes how the hydro-abrasive erosion
2.2.11 K
shape
relates to the shape of the abrasive particles
Note 1 to entry: See Annex D.
hardness factor that characterizes how the hydro-abrasive erosion
2.2.12 K
hardness
factor relates to the hardness of the abrasive particles
for 13Cr4Ni stainless steel: K = fraction of
hardness
particles harder than Mohs 4,5.
for hard coated surfaces: K = fraction of particles
hardness
harder than Mohs 7,0.
material factor factor that characterizes how the hydro-abrasive erosion
2.2.13 K
m
relates to the material properties of the base material
flow coefficient coefficient that characterizes how the hydro-abrasive 3,4
2.2.14 K mm×s
f
erosion relates to the water flow around each
𝛼𝛼
kg×h×m
component
sampling time interval between two water samples taken to
2.2.15 T h
s
interval determine the concentration of abrasive particles in the
water
yearly particle Total load (PL) for 1 year of operation, i.e. PL for T = 8
2.2.16 PL
kg × h/m
year
load 760 h calculated in accordance with 2.2.9
maximum maximum value of the integrand in the PL integral 3
2.2.17 PL kg/m
max
particle load during a specified time interval, i.e. the maximum value
of the following expression
PL = C(t )× K (t )× K (t )× K (t )
max size shape hardness
particle median diameter of abrasive particles in a sample, i.e.
2.2.18 dP mm
median such diameter that the particles with size smaller than
diameter the value under consideration represent 50 % of the
total mass of particles in the sample
o
impingement angle between the particle trajectory and the surface of
2.2.19
angle the substrate
Sub- Term Definition Symbol Unit
clause
characteristic flow through unit divided by the minimum flow area at
2.2.20 W m/s
gv
velocity in the guide vane apparatus at best efficiency point
Francis guide
vanes
Q
characteristic
W =
gv
velocity in
a × Z × B
0 0
Kaplan guide
vanes
characteristic speed of the water flow at injector location
2.2.21 W m/s
inj
velocity in
Pelton injector
W = 2× E
inj
characteristic relative velocity between the water and the runner blade
2.2.22 W m/s
run
velocity in estimated with below formulas at best efficiency point
turbine runner
2 2
W = u + c
run 2 2
u = n ×π × D
Q × 4
c = (Francis)
π × D
Q × 4
c = (Kaplan)
π × (D − D )
h
characteristic relative velocity between the water and the runner
2.2.23 W m/s
run
velocity in bucket
Pelton runner
W = 0,5 × 2 × E
run
discharge volume of water per unit time passing through any
2.2.24 Q m /s
section in the system
guide vane average shortest distance between adjacent guide
2.2.25 a m
opening vanes (at a specified section if necessary)
Note 1 to entry: For further information, see
IEC 60193.
number of total number of guide vanes in a turbine
2.2.26 z
guide vanes
distributor height of the distributor in a turbine
2.2.27 B m
height
rotational number of revolutions per unit time
2.2.28 n 1/s
speed
specific speed commonly used specific speed of a hydraulic machine
2.2.29 n rpm
s
60 × n × P
n =
s
5 / 4
H
P and H are taken in the rated operating point and given
in kW and m respectively
output output of the turbine in the rated operating point
2.2.30 P kW
hydro-abrasive estimated actual depth of metal that will be removed S

2.2.31 target mm
erosion depth from a component of the target turbine due to particle
of target unit hydro-abrasive erosion
Note 1 to entry: For use with the reference model.
hydro-abrasive hydro-abrasive erosion depth of metal that has been S

2.2.32 ref mm
erosion depth removed from a component of the reference turbine due
of reference to hydro-abrasive erosion
unit
Note 1 to entry: For use with the reference model.

– 12 – IEC 62364:2019  IEC 2019
Sub- Term Definition Symbol Unit
clause
number of number of nozzles in a Pelton turbine z
2.2.33 jet
nozzles
bucket width bucket width in a Pelton runner B
2.2.34 2 mm
number of number of buckets in a Pelton runner z
2.2.35 2
buckets
time between time between overhaul for target unit TBO
2.2.36 target h
overhaul for
target unit
Note 1 to entry: For use with the reference model.
time between time between overhaul for reference unit TBO
2.2.37 ref h
overhaul for
reference unit
Note 1 to entry: For use with the reference model.
turbine reference size for calculation curvature dependent RS
2.2.38 m
reference size effects of hydro-abrasive erosion
Note 1 to entry: For Francis turbines, it is the
reference diameter, D (see 2.2.4).
Note 2 to entry: For Pelton turbines it is the inner
bucket width, B .
Note 3 to entry: For further information in the inner
bucket width, B , see IEC 60609-2.
size exponent exponent that describes the size dependant effects of p
2.2.39
hydro-abrasive erosion in evaluating RS
exponent numerical value of 0,4-p that balances units for K α
2.2.40 f
3 Prediction of hydro-abrasive erosion rate
3.1 Model for hydro-abrasive erosion depth
The following formula can be used to estimate the hydro-abrasive erosion depth in a Francis
turbine:
3,4 p
S = W × PL × K × K / RS
m f
• The characteristic velocity, W, is defined in 2.2.20 to 2.2.23. If detailed data to calculate W
is not available it can be estimated based on Figure 1,
• PL, K and RS are defined in 2.2.9, 2.2.13 and 2.2.38 respectively,
m
• For uncoated components of Francis turbines K and p are taken from Table 1 below.
f
For additional information of the background for this formula please refer to Annex I. A sample
calculation is found in Annex G.

2,5
0,5
W = (0,25 + 0,003 × n ) × (2 × g × H)
run s
1,5
0,5
W = 0,55 × (2 × g × H)
gv
0,5
0 100 200 300 400 500 600 700 800
Turbine specific speed, n (using m, kW)
s
IEC
NOTE Values of n and H in this figure refer to the rated operating point while the characteristic velocities are
s
given for the points noted in Clause 2.
Figure 1 – Estimation of the characteristic velocities in guide vanes, W ,
gv
and runner, W , as a function of turbine specific speed
run
Table 1 – Values of K and p for various components
f
Component K Exponent p
f
(for RS)
-6
Francis guide vanes 0,25
1,06 × 10
-6
Francis facing plates 0,86 × 10 0,25
-6
Francis labyrinth seals 0,38 × 10 0,75
-6
Francis runner inlet 0,25
0,90 × 10
-6
Francis runner outlet 0,75
0,54 × 10
3.2 Reference model
In the reference model presented in this document the TBO of two turbines are compared to
each other. To do this the TBO of one turbine (here called reference turbine) and the
differences in the influencing parameters to another turbine (here called target turbine) have
to be known to calculate the TBO of the target turbine. Note that the same overhaul criteria
have to be applied for both the target and reference turbines.
The aim of the reference model is not to calculate the hydro-abrasive erosion depth (S).
Therefore a calibrated model for the depth is not necessary. The criteria for the TBO can be
the relative amount of damage, the efficiency loss or some other criteria but has to be the
same for both turbines.
Characteristic velocity coefficient W , W
gv run
– 14 – IEC 62364:2019  IEC 2019
There are a few differences in the way the formula is built up between the reference model
and the absolute model as follows:
• since the reference model does not calculate the hydro-abrasive erosion depth of
individual components, constants valid for the whole turbine are used instead of different
constants for different components;
• a larger turbine can normally withstand more hydro-abrasive erosion depth than a small
turbine before it needs overhaul. For this reason the exponent for turbine reference size,
p, is chosen as 1 in the reference model;
• for Pelton turbines, it is assumed that the critical component for overhaul is the runner. In
addition to the factors described above, the K for Pelton runners is assumed to be
f
proportional to the number of nozzles and the speed and inversely proportional to the
number of buckets;
The TBO for the target turbine can be calculated as follows:
3,4 3,4
TBO / TBO = W / W × PL / Pl × K / K × K / K ×
target ref ref target ref target m,ref m,target f,ref f,target
p p
RS / RS
target ref
In this equation, we use the following values for the relationships:
Pelton turbines: K / K = z × z / (z × z )
f, ref f, target jet,ref 2,target jet,target 2,ref
Francis and Kaplan turbines: K / K = 1
f,ref f,target
Size exponent: p = 1
The accuracy of the reference model might decrease when the differences between the
reference and target turbines become large.
The sensitivity of the calculated TBO value to variances in the input variables can also be
studied with the same formula. A sample calculation is found in Annex H.
3.3 Simplified hydro-abrasive erosion evaluation
In addition to the formulas in 3.1 and 3.2 other methods to estimate hydro-abrasive erosion
have been proposed, such as in [15] and [22] . Each method may have its advantages and
disadvantages.
As a quick and easy rule of thumb to make a first assessment of the severity at a particular
site it is recommended to evaluate the following expression, which is shown graphically in
Figure 2.
1,5
If C × H ≤ 150 then the hydro-abrasive erosion may not be significant.
1,5
If 150 < C × H < 1
...