EN 62364:2013

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Wasserturbinen - Leitfaden für den Umgang mit hydroabrasiver Erosion in Kaplan-, Francis und Pelton-Turbinen/Hydraulic machines - Guide for dealing with hydro-abrasive erosion in Kaplan, Francis and Pelton turbines23.100.01Fluid power systems in generalICS:Ta slovenski standard je istoveten z:EN 62364:2013SIST EN 62364:2014en01-januar-2014SIST EN 62364:2014SLOVENSKI
STANDARD
EUROPEAN STANDARD EN 62364 NORME EUROPÉENNE
EUROPÄISCHE NORM August 2013
CENELEC European Committee for Electrotechnical Standardization Comité Européen de Normalisation Electrotechnique Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Avenue Marnix 17, B - 1000 Brussels
© 2013 CENELEC -
All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 62364:2013 E
ICS 23.100.10; 27.140
English version
Hydraulic machines -
Guide for dealing with hydro-abrasive erosion in Kaplan,
Francis, and Pelton turbines (IEC 62364:2013)
Machines hydrauliques -
Guide relatif au traitement de l'érosion hydro-abrasive des turbines Kaplan, Francis et Pelton (CEI 62364:2013)
Wasserturbinen -
Leitfaden für den Umgang mit hydroabrasiver Erosion in Kaplan-, Francis- und Pelton-Turbinen (IEC 62364:2013)
This European Standard was approved by CENELEC on 2013-08-01. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CENELEC member.
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Foreword The text of document 4/279/FDIS, future edition 1 of IEC 62364, prepared by IEC TC 4 "Hydraulic turbines" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as EN 62364:2013. The following dates are fixed: – latest date by which the document has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 2014-05-01 – latest date by which the national standards conflicting with the document have to be withdrawn (dow) 2016-08-01
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CENELEC [and/or CEN] shall not be held responsible for identifying any or all such patent rights. Endorsement notice The text of the International Standard IEC 62364:2013 was approved by CENELEC as a European Standard without any modification. In the official version, for Bibliography, the following note has to be added for the standard indicated : IEC 60193:1999 NOTE Harmonised as EN 60193:1999 (not modified).

IEC 62364 Edition 1.0 2013-06 INTERNATIONAL STANDARD NORME INTERNATIONALE Hydraulic machines – Guide for dealing with hydro-abrasive erosion in Kaplan, Francis, and Pelton turbines
Machines hydrauliques – Guide relatif au traitement de l'érosion hydro-abrasive des turbines Kaplan, Francis et Pelton
INTERNATIONAL ELECTROTECHNICAL COMMISSION COMMISSION ELECTROTECHNIQUE INTERNATIONALE XC ICS 23.100.10; 27.140 PRICE CODE CODE PRIX ISBN 978-2-83220-829-8
colourinside
– 2 – 62364 © IEC:2013 CONTENTS FOREWORD . 5 INTRODUCTION . 7 1 Scope . 8 2 Terms, definitions and symbols . 8
Units . 8 2.1 Terms, definitions and symbols . 9 2.23 Abrasion rate . 11
Theoretical model . 11 3.1 Introduction to the PL variable . 13 3.2 Survey results . 15 3.3 Reference model . 16 3.44 Design . 17
General . 17 4.1 Water conveyance system . 17 4.2 Valve . 18 4.3 General . 18 4.3.1 Selection of abrasion resistant materials and coating . 18 4.3.2 Stainless steel overlays . 19 4.3.3 Protection (closing) of the gap between housing and trunnion . 19 4.3.4 Stops located outside the valve . 19 4.3.5 Proper capacity of inlet valve operator . 19 4.3.6 Increase bypass size to allow higher guide vane leakage . 19 4.3.7 Bypass system design . 20 4.3.8 Turbine . 20 4.4 General . 20 4.4.1 Hydraulic design . 20 4.4.2 Mechanical design . 22 4.4.3 Operation . 28 4.4.4 Spares and regular inspections . 29 4.4.5 Particle sampling and monitoring . 29 4.4.65 Abrasion resistant materials . 30
Guidelines concerning relative abrasion resistance of materials including 5.1abrasion resistant coatings . 30
General . 30 5.1.1 Discussion and conclusions . 31 5.1.2 Guidelines concerning maintainability of abrasion resistant coating materials . 32 5.2 Definition of terms used in this sublcause . 32 5.2.1 Time between overhaul for protective coatings . 32 5.2.2 Maintenance of protective coatings . 33 5.2.36 Guidelines on insertions into specifications . 34
General . 34 6.1 Properties of particles going through the turbine. 35 6.2 Size distribution of particles . 35 6.3 Mineral composition of particles for each of the above mentioned periods . 36 6.4Annex A (informative)
PL calculation example . 37 Annex B (informative)
Measuring and recording abrasion damages . 39

62364 © IEC:2013 – 3 – Annex C (informative)
Water sampling procedure . 52 Annex D (informative)
Procedures for analysis of particle concentration, size, hardness and shape . 53 Annex E (informative)
Tests of abrasion resistant materials . 56 Annex F (informative)
Typical criteria to determine overhaul time due to abrasion erosion . 67 Annex G (informative)
Example to calculate the amount of erosion in the full model . 68 Annex H (informative)
Examples to calculate the TBO in the reference model . 70 Bibliography . 73
Figure 1 – Estimation of the characteristic velocities in guide vanes, Wgv, and runner, Wrun, as a function of turbine specific speed . 13 Figure 2 – Example of flow pattern in a Pelton injector at different load . 14 Figure 3 – Example of protection of transition area . 19 Figure 4 – Runner blade overhang in refurbishment project . 21 Figure 5 – Example of “mouse-ear” cavitation on runner band . 22 Figure 6 – Detailed design of guide vane trunnion seals . 23 Figure 7 – Example of fixing of facing plates from the dry side . 25 Figure 8 – Head cover balancing pipes with bends . 26 Figure 9 – Step labyrinth with optimized shape for hard coating . 28 Figure 10 – Development of spiral pressure over time . 33 Figure D.1 – Typical examples of particle geometry . 55 Figure E.1 – Schematic of test rig used for test 1 . 56 Figure E.2 – ASTM test apparatus . 58 Figure E.3 – Test coupon . 59 Figure E.4 – Slurry pot test facility . 60 Figure E.5 – High velocity test rig . 61 Figure E.6 – Samples are located on the rotating disk . 62 Figure E.7 – Comparison of two samples after testing . 62 Figure E.8 – Whole test system of rotating disk . 62 Figure E.9 – Schematic of test rig used for test 8 . 64 Figure E.10 – Testing of samples on hydro abrasive stand . 65 Figure E.11 – Cover of disc . 65 Figure E.12 – Curve of unit abrasion rate with circumference velocity for 3 kinds of materials . 66
Table 1 – Data analysis of the supplied questionnaire . 16 Table 2 – Overview over the feasibility for repair C . 33 Table 3 – Form for properties of particles going through the turbine . 35 Table 4 – Form for size distribution of particles . 36 Table 5 – Form for mineral composition of particles for each of the above mentioned periods . 36 Table A.1 – Example of documenting sample tests . 37 Table A.2 – Example of documenting sample results . 38 Table B.1 – Inspection record, runner blade inlet form . 44

– 4 – 62364 © IEC:2013 Table B.2 – Inspection record, runner blade outlet form . 45 Table B.3 – Inspection record, runner band form. 46 Table B.4 – Inspection record, guide vanes form. 47 Table B.5 – Inspection record, facing plates and covers form . 48 Table B.6 – Inspection record, upper stationary seal form . 49 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 E.1 – Relative wear resistance in laboratory test 1 . 57 Table E.2 – Relative wear resistance in laboratory test 2 . 57 Table E.3 – Relative wear resistance in laboratory test 3 . 58 Table E.4 – Relative wear resistance in test 4 . 59 Table E.5 – Results of test . 60 Table E.6 – Results of test . 61 Table E.7 – Results from test . 63 Table E.8 – Relative wear resistance in laboratory test 8 . 64 Table E.9 – Results of relative wear resistance for some materials (U = 40m/s) . 66 Table G.1 – Calculations . 69 Table H.1 – Pelton turbine calculation example . 70 Table H.2 – Francis turbine calculation example . 71

62364 © IEC:2013 – 5 – INTERNATIONAL ELECTROTECHNICAL COMMISSION ____________
HYDRAULIC MACHINES –
GUIDE FOR DEALING WITH HYDRO-ABRASIVE EROSION
IN KAPLAN, FRANCIS, AND PELTON TURBINES
FOREWORD 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with may participate in this preparatory work. International, governmental and non-governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for Standardization (ISO) in accordance with conditions determined by agreement between the two organizations. 2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international consensus of opinion on the relevant subjects since each technical committee has representation from all interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any misinterpretation by any end user. 4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications transparently to the maximum extent possible in their national and regional publications. Any divergence between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter. 5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any services carried out by independent certification bodies. 6) All users should ensure that they have the latest edition of this publication. 7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and members of its technical committees and IEC National Committees for any personal injury, property damage or other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is indispensable for the correct application of this publication. 9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent rights. IEC shall not be held responsible for identifying any or all such patent rights. International Standard IEC 62364 has been prepared by IEC technical committee 4: Hydraulic turbines. The text of this standard is based on the following documents: FDIS Report on voting 4/279/FDIS 4/283/RVD
Full information on the voting for the approval of this standard can be found in the report on voting indicated in the above table. This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

– 6 – 62364 © IEC:2013 The committee has decided that the contents of this publication will remain unchanged until the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data related to the specific publication. At this date, the publication will be
• reconfirmed, • withdrawn, • replaced by a revised edition, or • amended.
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62364 © IEC:2013 – 7 – 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.
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 service. This has led some owners to write into their specifications, conditions which cannot be met with known methods and materials.

– 8 – 62364 © IEC:2013 HYDRAULIC MACHINES –
GUIDE FOR DEALING WITH HYDRO-ABRASIVE EROSION
IN KAPLAN, FRANCIS, AND PELTON TURBINES
1 Scope This Guide serves to: a) present data on particle abrasion rates on several combinations of water quality, operating conditions, component materials, and component properties collected from a variety of hydro sites; b) develop guidelines for the methods of minimizing particle abrasion by modifications to hydraulic design for clean water. These guidelines do not include details such as hydraulic profile shapes which should be determined by the hydraulic design experts for a given site; c) develop guidelines based on “experience data” concerning the relative resistance of materials faced with particle abrasion problems; d) develop guidelines concerning the maintainability of abrasion resistant materials and hard facing coatings; e) develop 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) develop guidelines concerning operation mode of the hydro turbines in water with particle materials to increase the operation life; It is assumed in this Guide 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 Guide to address these issues.
It is assumed in this Guide that cavitation is not present in the turbine. Cavitation and abrasion may reinforce each other so that the resulting erosion is larger than the sum of cavitation erosion plus abrasion erosion. The quantitative relationship of the resulting abrasion is not known and it is beyond the scope of this guide to assess it, except to recommend 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 impact turbine components and produce damage. This damage may in turn increase the flow turbulence thereby accelerating wear by both cavitation and abrasion. Abrasion resistant coatings can also be damaged locally by impact of large solids. It is beyond the scope of this Guide to address these issues. This guide focuses mainly on hydroelectric powerplant equipment. Certain portions may also be applicable to other hydraulic machines. 2 Terms, definitions and symbols
Units
2.1The International System of Units (S.I.) is adopted throughout this guide but other systems are allowed.

62364 © IEC:2013 – 9 –
Terms, definitions and symbols
2.2For the purposes of this document, the following terms, definitions and symbols apply. NOTE They are also based, where relevant, on IEC/TR 61364. Sub-clause Term Definition Symbol Unit 2.2.1 specific hydraulic energy of a machine specific energy of water available between the high and low pressure reference sections 1 and 2 of the machine Note 1 to entry: For full information, see IEC 60193. E J/kg 2.2.2 acceleration due to gravity
local value of gravitational acceleration at the place of testing Note 1 to entry: For full information, see IEC 60193.
g m/s2 2.2.3 turbine head
pump head available head at hydraulic machine terminal
H = E/g H m 2.2.4 reference diameter reference diameter of the hydraulic machine 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. D m 2.2.5 abrasion depth depth of metal layer that has been removed from a component due to particle abrasion S mm 2.2.6 characteristic velocity characteristic velocity defined for each machine component and used to quantify particle abrasion damage Note 1 to entry: See also 2.2.20 to 2.2.24. W m/s 2.2.7 particle concentration the mass of all solid particles per m3 of water solution Note 1 to entry: In case the particle concentration is expressed in ppm it is recommended to use the mass of particles per mass of water, so that 1 000 ppm approximately corresponds to 1 kg/m3. C kg/m3 2.2.8 particle load the particle concentration integrated over the time, T, that is under consideration
∫×××=TdttKtKtKtCPL0hardnessshapesize)()()()( ××××≈∑=NnnsnnnnTKKKC1hardnessshapesize,,,, 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. PL kg × h/m3 2.2.9 size factor factor that characterizes how the abrasion relates to the size of the abrasive particles Ksize
2.2.10 shape factor factor that characterizes how the abrasion relates to the shape of the abrasive particles Kshape
2.2.11 hardness factor factor that characterizes how the abrasion relates to the hardness of the abrasive particles Khardness

– 10 – 62364 © IEC:2013 Sub-clause Term Definition Symbol Unit 2.2.12 material factor factor that characterizes how the abrasion relates to the material properties of the base material Km
2.2.13 flow coefficient coefficient that characterizes how the abrasion relates to the water flow around each component Kf mm × s3,4 kg × h × m. 2.2.14 sampling interval the time interval between two water samples taken to determine the concentration of abrasive particles in the water Ts h 2.2.15 yearly particle load the total PL for 1 year of operation, i.e. PL for T = 8 760 h calculated in accordance with 2.2.8 PLyear kg × h/m3 2.2.16 maximum concentration the maximum concentration of abrasive particles over a specified time interval Cmax kg/m3 2.2.17 particle median diameter the median diameter of abrasive particles in a sample, i.e. such diameter that the particles with size smaller than the value under consideration represent 50 % of the total mass of particles in the sample dP50 mm 2.2.18 wear resistance index abrasion depth or volume of a reference material (generally some version stainless steel) divided by the abrasion depth or volume of the material in question, tested under the same conditions WRI - 2.2.19 impingement angle the angle between the particle trajectory and the surface of the substrate
o 2.2.20 characteristic velocity in Francis guide vanes
characteristic velocity in Kaplan guide vanes flow through unit divided by the minimum flow area at the guide vane apparatus estimated at best efficiency point
00gvBZaQW××=
Wgv
m/s 2.2.21 characteristic velocity in guide vanes of Kaplan, Francis or tubular turbines speed of the water flow at guide vane location
EW××=250gv,
Wgv
m/s 2.2.22 characteristic velocity in Pelton injector speed of the water flow at injector location
EW×=2inj
Winj
m/s 2.2.23 characteristic velocity in Kaplan or Francis tubular turbine runner the relative velocity between the water and the runner blade estimated with below formulas at best efficiency point
2222222run4DQcDnucuW××=××=+=ππ Note 1 to entry: In calculation of c2 for Kaplan turbines, the hub diameter has been neglected in the interest of simplicity. Wrun m/s 2.2.24 characteristic velocity in Pelton runner speed of the water flow at a Pelton runner
EW××=250run,
Wrun
m/s 2.2.25 discharge (volume flow rate) volume of water per unit time passing through any section in the system Q m3/s 2.2.26 guide vane opening average shortest distance between adjacent guide vanes (at a specified section if necessary) A m

62364 © IEC:2013 – 11 – Sub-clause Term Definition Symbol Unit Note 1 to entry: For further information, see IEC 60193. 2.2.27 number of guide vanes total number of guide vanes in a turbine z0
2.2.28 distributor height height of the distributor in a turbine B0 m 2.2.29 rotational speed number of revolutions per unit time n 1/s 2.2.30 specific speed commonly used specific speed to of an hydraulic machine
45s60/HPnn××= P and H are taken in the rated operating point and given in kW and m respectively ns
2.2.31 output output of the turbine in the rated operating point P kW 2.2.32 actual abrasion depth of target unit the estimated depth of metal that will be removed from a component of the target turbine due to particle abrasion Note 1 to entry: For use with the Reference model. Starget, actual mm 2.2.33 actual abrasion depth of reference unit the actual depth of metal that has been removed from a component of the reference turbine due to particle abrasion Note 1 to entry: For use with the Reference model. Sref, actual mm 2.2.34 number of nozzles number of nozzles in a Pelton turbine z0
2.2.35 bucket width bucket width in a Pelton runner B2 mm 2.2.36 number of buckets number of buckets in a Pelton runner z2
2.2.37 time between overhaul for target unit time between overhaul for target unit Note 1 to entry: For use with the reference model. TBOtarget h 2.2.38 time between overhaul for reference unit time between overhaul for reference unit Note 1 to entry: For use with the reference model. TBOref h 2.2.39 turbine reference size the reference size for calculation curvature dependent effects of 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. RS m 2.2.40 size exponent exponent that describes the size dependant effects of erosion in evaluating RS p
2.2.41 exponent numerical value of 0,4-p that balances units for Kf
.
3 Abrasion rate
Theoretical model 3.1In order to demonstrate how different critical aspects impact the particle abrasion rate in the turbine, the following formula is considered:

– 12 – 62364 © IEC:2013 dS/dt = f(particle velocity, particle concentration, particle physical properties, flow pattern, turbine material properties, other factors) However, this formula being of little practical use, several simplifications are introduced. The first simplification is to consider the several variables as independent as follows: dS/dt = f(particle velocity) × f(particle concentration) × f(particle physical properties, turbine material properties) × f(particle physical properties) × f(flow pattern) × f(turbine material properties) × f(other factors) This simplification is not proven. In fact, many examples can be found where this simplification was not strictly valid. Nevertheless, based on literature studies and experience, this simplification is considered to be justified for hydraulic machines.
The next simplification consists in assigning values to the functions. In the following equations the numerical values for the parameters, without units, have to be used. The units in which the values should be based are given below: • f(particle velocity) = (particle velocity)n. In the literature abrasion is often considered proportional to the velocity raised to an exponent, n. Most references give values of n between 2 and 4. In this guide we suggest to use n = 3,4. Particle velocity in m/s, • f(particle concentration) = particle concentration in kg/m3, • f(particle physical properties, turbine material properties) = Khardness = function of how hard the particles are in relation to the material at the surface. At the present stage we suggest to use Khardness = fraction of particles harder than the material at the surface, • f(flow pattern) = Kf/RSp (Kf = constant for each turbine component, RS = turbine reference size in m, p = exponent for each turbine component). Kf considers impingement angle and flow turbulence. RSp considers part curvature radius, • f(particle physical properties) = f(particle size, particle shape, particle hardness) = f(particle size) × f(particle shape) = Ksize × Kshape. Note that in this simplification it as assumed that there is no influence from the particle hardness for this function. The particle hardness is considered in the Khardness factor,
• Ksize = median diameter of particles in mm, • Kshape = f(particle angularity). It is believed that Kshape will increase with the degree of irregularity of the particles. Specific data is not available at present but several literature references indicate that Kshape varies from 1 to 2 from round to sharp, • f(turbine material properties) = Km. In this guide we consider Km = 1 for martensitic stainless steel with 13 % Cr and 4 % Ni
and Km = 2 for carbon steel. For coated components Km should be smaller than 1, • f(other factors) = 1. Again, these functions are engineering approximations in order to obtain useful results for hydraulic machines. We then have the following formula dS/dt = (particle velocity)3,4 × C × Khardness × Ksize × Kshape × Kf /RSp × Km The final step is to integrate this formula with respect to time. When we do this we find three distinct different types of variables with respect to their variations in time: 1) particle velocity and Kf: these variables vary with the water flow relative to the individual component, which in turn may vary with the head and flow; 2) C, Khardness, Ksize and Kshape: these variables vary with the particle properties. Integrated
over time these variables become particle load, PL (see 2.2.8 for definition of PL and Annex A for a sample calculation); 3) RS, p and Km: these variables are constant in time.

62364 © IEC:2013 – 13 – To find a simple and reasonably accurate estimate of the time integral, the PL variable (see 2.2.8) is introduced. PL integrates C, Khardness, Ksize and Kshape over time. When using PL, the particle velocity and Kf can be considered approximately constant over a limited variation of head and flow (see 3.2). Since these variables are considered constant, Kf and p were used as calibration factors to obtain good agreement between actual test data and the formula. The particle velocity can be replaced with the characteristic velocity, W, defined in 2.2.20 to 2.2.24. W may be calculated for a specific turbine based on main data and dimensions. Since the effect of velocity on abrasion is proportional to the velocity raised to a power of 3,4 it is very important to estimate it accurately. For new turbines during design and bid stage, W for different components should be provided by the turbine manufacturer. When this is not possible, W can be estimated approximately from the diagram in Figure 1.
NOTE Values of ns and H in this figure refer to the rated operating point while the characteristic velocities are given for the points noted in 2.2. Figure 1 – Estimation of the characteristic velocities in guide vanes, Wgv, and runner, Wrun, as a function of turbine specific speed So the final, time integrated formula becomes: S = W3,4 × PL × Km × Kf / RSp S is the numerical value of the abrasion depth in mm.
Introduction to the PL variable 3.2In this code the PL variable has been introduced, which has not been widely used before. One common way to integrate abrasion over time has been to consider the total weight of particles 0.00.51.01.52.02.50100200300400500600700800Characteristic velocity coefficient
Wgv, Wrun Turbine specific speed (using m, kW) Wrun = (0,25 + 0,003 × ns) × (2 × g × H)0,5 Wgv = 0,55 × (2 × g × H)0,5

– 14 – 62364 © IEC:2013 that pass the turbine. However, this approach has usually not considered the effects from variation in flow or head in the turbine and could therefore lead to erroneous conclusions. To illustrate this consider the following example. A Pelton injector (see Figure 2) operates for one day. Assume the head is 800 m and the abrasive particle concentration is 0,1 kg/m3. Case 1:
At full opening (top half of Figure 2) the water with particles flows over the seat ring with a velocity of (2×g×H)0,5 = 125 m/s. In one day the amount of particles that pass the injector is 2 m3/s × 3 600 s/h × 24 h/day × 0,1 kg/m3 × 1 day = 17 tons. Case 2:
At 10 % opening (bottom half of Figure 2) the water with particles flows over the seat ring with the same velocity as in case 1 (125 m/s). In one day the amount of particles that pass the injector is 0,2 × 3 600 × 24 × 0,1 × 1 = 1,7 tons. In both cases the seat ring has been subject to abrasion with the same particle concentration, the same water velocity and the same amount of time. Therefore, the expected abrasion damage is the same. The PL variable also gives the same value in both cases. However, the total weight of particles that has passed the unit is 10 times higher in case 1 compared to case 2. So, PL is expected to correlate better with abrasion damage than the total weight of particles that has passed the seat ring.
Full opening Q = 2 m3/s 10 % opening Q = 0,2 m3/s
Figure 2 – Example of flow pattern in a Pelton injector at different load The same type of reasoning can also be applied to other components subject to abrasion. In the following is a condensed summary of such analysis. • Pelton needle tip Very good correlation between PL and abrasion damage with minor influence of turbine discharge or head is expected. Some influence from the turbine flow since the water velocity is lower further inside the injector, where the needle is located at high flows. Some influence from turbine head since the water velocity is proportional to the square root of the head. With head and flow variations that are normal in Pelton projects this influence is disregarded in the interest of simplicity. • Pelton runner Good correlation between PL and abrasion damage with minor influence of turbine discharge or head is expected. Some influence from the turbine flow since the water film is thicker at higher flows and therefore more particles may be pressed towards the outside surface due to centrifugal forces. Some influence from turbine head since the relative water velocity in the

62364 © IEC:2013 – 15 – runner depends on the head. With head and flow variations that are normal in Pelton projects, this influence is disregarded in the interest of simplicity. • Francis and Kaplan guide vanes and covers / facing plates Good correlation between PL and abrasion damage with minor influence of turbine discharge or head is expected. Some influence from the turbine flow since the water velocity is higher at low discharge and the pressure difference between the two sides of the guide vane varies with flow. In particular, if the unit is at standstill with pressurized spiral case the leakage flow through the guide vanes has high velocity. Some influence from the turbine head since the relative water velocity in the guide vanes depends on the head. With head and flow variations that are normal in Francis and Kaplan projects, this influence is disregarded in the interest of simplicity.
• Francis runner seals / labyrinths Very good correlation between PL and abrasion damage with minor influence of turbine discharge or head is expected. Some influence is expected from the turbine flow and head since they influence the pressure before and after the seal and thus the leakage flow through the seal. With head and flow variations that are normal in Francis projects, this influence is disregarded in the interest of simplicity.
• Francis runner blade inlet Good correlation between PL and abrasion damage with minor influence of turbine discharge or head is expected. Some influence from the turbine discharge is expected since the water velocity is higher at low discharge. Moreover, the pressure difference between the two sides of the guide vanes varies with opening, resulting in more leakage between the guide vanes and the covers which in turn results in more unfavourable flow conditions at the runner inlet. Also discharge and head variations from the optimum operating point, will result in more unfavourable flow conditions at the runner inlet. With head and flow variations that are normal in Francis projects this influence is disregarded, as long as inlet cavitation is not present, in the interest of simplicity. • Francis runner blade outlet Reasonable correlation between PL and abrasion damage with minor influence of turbine discharge or head is expected. At part load there are two main phenomena that influence the wear. One is that the average velocity (defined as the total flow divided by the flow passage area) will decrease with decreasing discharge. The other is that the degree of turbulence will increase and the flow distribution will lose uniformity at low discharge (typically below 50 % to 80 % of maximum discharge). These two phenomena influence the wear in opposite ways, but it is expected that the turbulence effect will dominate and thus that the wear will increase at partial load. However, due to lack of supporting data this influence is disregarded in the interest of simplicity. • Kaplan runner blade Very good correlation between PL and abrasion damage with minor influence of turbine discharge or head is expected. With head and flow variations that are normal in Kaplan projects this influence is disregarded in the interest of simplicity.
• Kaplan runner chamber Good correlation between PL and abrasion damage with minor influence of turbine discharge or head is expected. With head and flow variations that are normal in Kaplan projects this influence is disregarded in the interest of simplicity.
Survey results 3.3A questionnaire was sent to plant operators at sites known for their exposure to particle abrasion problems. The purpose of this questionnaire was to collect and analyse data on

– 16 – 62364 © IEC:2013 particle abrasion rates on as many combinations of water quality, operating conditions, component materials, and component properties as possible.
This data was analyzed and the factor Kf and the exponent p determined for each component to get the best possible correspondence between the calculated and observed amount of erosion. The average Kf was then determined for all observations with components of the same type. Table 1 below shows the resulting Kf and p for various components as well as the number of observations. The ratio between the measured and calculated values of the abrasion depth was determined and the standard deviation calculated. Table 1 – Data analysis of the supplied questionnaire Component Kf Exponent p (for RS) Number of observations Standard deviation
% Francis guide vanes 1,06 × 10-6 0,25 7 42 Francis facing plates 0,86 × 10-6 0,25 7 38 Francis labyrinth seals 0,38 × 10-6 0,75 7 30 Francis runner inlet 0,90 × 10-6 0,25 6 26 Francis runner outlet 0,54 × 10-6 0,75 6 41
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