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SXH™ COATINGS :

Successfully combating hydro-abrasive erosion on hydraulic turbineparts since 1986

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Dr. Kirsten Winkler

- graduated in Material Science in 1992 at the University RWTH Aachen (Germany)

- research scientist for 5 years in the material science department at the University Bremen

- in 1997: PhD in material science

- senior scientist for 5 years for DeBeers Industrial Diamonds in South Africa and England

- since 2003 into the hydro industry, working on the field of material science and coating

- since 2009 in ANDRITZ HYDRO, Switzerland, RD coating

- since Feb 2011 Head of Centre of Competence for Coating (CoC Coating) in ANDRITZ HYDRO

R&D on hydro-abrasive erosion

development and evaluation of suitable materials & processes for coating.

ANDRITZ HYDRO corporate mandate for technical support and supervision of all workshops worldwide,

coating for ANDRITZ HYDRO

Responsible for design adaptations due to erosion and coating

Project support when erosion is occuring

2 WIK / Sales B_ver 00

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Contents

Hydro-abrasive Erosion

SXH-Coating

Advantages

Experiences

Design


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The source of the problemExample: Aletsch-Mörel

intake

water passing theturbine with highconcentration ofparticles (high Mohshardness)

river water

WIK / Sales B_ver 004

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Damages due to hydro-abrasive erosionExample: Nathpa Jhakri

Guide vanes

Runner

• more damages

• efficiency loss• decreased TBO (time between overhaul),• longer overhaul duration


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Influences on hydro-abrasive erosion

Hydro-abrasiveerosion

Relativeparticlevelocity

Particle sizedistribution

Particleconcentration

Particlehardness

Particleshape

Other factors?

Materialproperties(turbine)

Flow pattern/Cavitation


Cannot be influenced bythe turbine manfacturerHighly varying with timeTo be measured for aguarantee

Design dependant

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Damages due to hydro-abrasive erosionEffect on energy production – minimising the damage

The goal of hydropower plants is a continued energy production at low costs and thereby minimisation of

down time and repair costs.

Two possibilities:

1. Decrease of the particle concentration with same turbinedue to plant design (Desander/Desilter/sand trap)

2. Reduction of costs due to erosion by turbine changes:Changes of hydraulic designChanges in the mechanic design

Mechanical protection of the components


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Examples of optimisation possibilities

Optimisation of:

1. HPP layout

2. the hydraulic layout

3. the mechanic design

4. coatingbetter overhaul possibilities

better coating suitability (access)

more stable design/construction

turbine type and number of units

geometry of intake

rotational speed (erosion rate ~ relative velocity 3)

minimization of cavitation

desander

high quality coating

full robotic in most cases

design to minimise damages due to h.-a. erosion


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SXH TM : Coating at ANDRITZ HYDRO

SXH™70/80 and SXH™7X/8X -Type: WC-CoCr

Micro hardness: > 900 HV0.3 (Vickers hardness, DPH 0.3 kg Load)

Bonding strength: > 70 MPa (in tensile test, perpendicular to the surface)

Surface roughness:

as sprayed: R a = 4 - 8 m

after operation in particle loaded water: R a = 1 - 3 m

Since 1986: Coating of Runners and other components at Andritz Hydro

1986- 1996: SXH™48 (Cr -oxid basis // Plasmaspray) & different coating developments

since 1996: SXH™70

since 2009: SXH™7X (for Pelton runner) From 2013: SXH TM80/8X

Base material

Surface

Coating


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SXH TM : Coating at ANDRITZ HYDROHVOF Coating (HVOF = High Velocity Oxygen Fuel)


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ANDRITZ HYDRO SXH TM - CoatingStandard Parts: Pelton & Francis

Pelton

Francis


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SXH TM70/80 + 7X/8X: Coating at ANDRITZ HYDRO

Advantages

Very good resistance against erosion

Tight tolerances

High material strength

High adhesive strength

Limitations

Geometrical limitations due to geometry of gun andnecessary spray parameters (distance, angle)

Low resistance against impact

Low resistance against cavitation


Repair

On-site repair by hard coating possible for certain parts

Possibility to repair damages with polymer SXH P 10 are evaluated (in test rig successful)

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Influences on a turbine due to the coating- Efficiency / TRE -

Change in efficiency of a turbine, coated and uncoated (schematic)

Amount of particles having passed through the turbine

E f f i c i e n c y

Uncoated: fastloss of originalgeometry

SXH-coated: Geometry isretained for a long time

Increase in TRE by factor 2 to 7

Influence ofthe surfaceroughness atthe beginningof operations.


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Amount of particles

Loss in revenue(Loss in production +

repairs)

Investment

Profit

with SXH70 without SXH70

overhaul

overhaul with coating

Customer benefits due to coating in power plants with erosion


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Data as per unit:Output 103 MWHead 702 m

Discharge 16.31 m 3/sPitch diameter 2860 mmNozzles 4Max. Sand load app. 1.7 kg/m 3

Hard Particles app. 83 %Repair after app.187’000 t

uncoated3600 h

runner R1

runner S2

Damages in coated runner:

Classical damage of splitter and cut-outDamage in the bucket-bottom due to jet-beamdistortion

Experience: Baspa II (India): 3 vertical Pelton units

TBO increase: 3x

SXH TM70-coated3800 h


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Experience: ALFALFAL (Chile): 2 vertical 6-nozzle Pelton turbines


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Experience: Pradella (Switzerland) : 4 Francis units, partially coated runners

Uncoated

with SXH70Coating

85

86

87

88

89

90

91

92

0 5000 10000 15000 20000 25000 30000

Operation time, h

E f f i c i e n c y , % Efficiency

Gain

The break-even point dependson the energy price and thetype and size of the runner

(amount of coating).


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Experience: Nathpa Jhakri (India) : 6 Francis units, fully coated runners

Nathpa Jhakri, India

Head: 428 - 487 mRunner diameter: 4238 mmPower: 255 – 336 MWMax. particle concentration: 12 kg/m 3

Second Runner (15).jpg

Some damage at inlet (left) and at outlet(right) after one year in operation (afterreaching end of guarantee) First Runner (5).jpg

Full coating by robot


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uncoatedlarge erosion after 1 monsoon season

SXH TM70 coatedvery small damages on two guide vanesafter 1 monsoon season

Experience: Nathpa Jhakri (India) : 6 Francis units, fully coated runners

TBO increase: >2x


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SXH TM7X/8X : Development for a better stability of the splitter on Pelton

SXH TM7X: 20% higher TBO

IMG_2465a.JPG

IMG_2331a.JPG

SXH TM70: worldwide standard

TBO: time between overhaul


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Benefits from SXH TM coatings :

extended lifetime (protection of hydraulic profile)higher power output and higher productivityless repair work and maintenance costsignificantly higher availability of the turbine

high return on investment

Limitations:

Small loss of initial efficiencyno NDT testing possible on coatingsensitive to cavitation

Advantages Coating


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Coating Design

If a coating is needed then this has to be known from the start of the project so that the

following optimisations can/have to be done:

- a coating friendly design (e.g. corners, accessibility in Francis runners)

- a design more resistant to erosion (e.g. better flow conditions)

- a design which is service & rehab friendly (e.g. replaceable facing plates)

In addition:

- Adaptations for bolted runners (e.g. adjustment of band thickness for the feet of blades)


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Measurement of particle parameters

- Laser measurement online LISST system (concentration & grain size distribution

- Filtration (concentration)

- Laser measurement lab (grain size distribution)

- XRD (mineral composition)

Important is

- to analyse water, which is representative for the water going through the turbine

- To analyse often enough that also fluctuations will be seen (higher concentrations during rains, changingmineralogical composition)


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01/2010

Documents

COATING 05-2013