Risk Mitigation - Action Plan - Blade - Uptime Engineering · Perform risk mitigation activities in parallel with product development cyclic icing de-icing test on ... Failure statistics

1. Reliability: The other dimension of quality, W.Q. Meeker, L.A. Escobar, Qual. Tech. & Quant. Management., 1, 1,pp. 1-25, 2004

2. Method for Testing the reliability of complex systems, Ch. Gray, N. Haselgruber, F. Langmayr, Patent application EP12180254.0,

2012

3. Physics of failure approach to wind turbine condition based maintenance, Chr. S. Gray, S.J. Watson, Wind Energy online, DOI:

10.10002/we.360, 2009

4. Reliability of wind turbine blades: An overview of materials testing, J.W. Holmes, B.F. Sörensen, P. Bronsdsted, Wind Power

Shanghai 2007, proceedings

Perform risk mitigation activities in parallel with product development

Combine contributions from OEM and suppliers in a joint process

Start component durability testing as soon as possible to prepare system validation

Start validation activities with component maturity demonstration

Turbine reliability is key to lifetime profitability of wind farms. Standards give a guideline for proper selection of components with

respect to expected wind conditions, i.e. primarily to cope with different levels of fatigue load. Failure statistics show a wide range of

failure modes in the field, not all of them being well reflected by wind classification.

The contribution of turbine test operation to lifetime demonstration is limited due to lack of acceleration potential. However, component

testing can play a major role in maturity demonstration if durability tests are performed. Moreover, there is further potential for risk

reduction by dedicated material tests. Detailed understanding of potential failure mechanisms is necessary to identify useful tests and

quantify their contribution to reliability demonstration.

A reliability improvement program for wind turbines is proposed. It starts with the investigation of risks, including technical, quality and

organizational aspects. According to the identified risks for each failure mode the corresponding risk mitigation tasks are derived: load

case simulation, failure mode investigation, quality system review, supplier assessment, etc. Input data quality is critical for adequate

test design: time logs of wind and climate conditions, grid quality, site location, failure statistics, technical specifications of turbine

candidates are necessary. Lack of knowledge or low quality data can turn out as the major risk during early project phases.

Proper component testing requires the understanding of component failure modes. Therefore, in a consecutive step the potential

failure mechanisms of turbine components have to be analyzed. If this bottom-up analysis is done strictly failure mode related, it

delivers damaging operation conditions and boundary conditions. These correlations can be used for describing damage kinetics with

physics of failure models, based on observable operation and climate data logs. Such models have been successfully used for test

development, for adaptation of test procedures to field conditions, for evaluation of test acceleration with respect to certain failure

modes. These models are used to evaluate the overall demonstration potential of a turbine validation program. Such an assessment

delivers weak-points as well as over-testing. It identifies particularly aggressive conditions for a given location with respect to certain

failure modes and checks whether complementary measures have to be taken for risk mitigation.

During recent years the process described above has been applied successfully to various industries such as automotive (pass cars,

heavy duty trucks, railway) or industrial equipment (e.g., hydraulics). The potential for wind turbines is illustrated by showing results of

a particular analysis, with details given for the turbine blades. It shows clearly the potential of dedicated test rigs to cover real lifetime

fatigue load while further tests are required for various other failure modes. A corresponding component maturity demonstration plan is

presented.

Component maturity demonstration is a powerful initial step of turbine reliability validation

Front loading of reliability and lifetime demonstration with component tests:

accelerated / dedicated to certain failure modes / cost effective / parallel

Elimination of risk is possible for certain failure modes by component testing

Physics of failure has to be understood for quantitative test acceleration

Duty cycle load histories – e.g. from SCADA - are essential for test parameterisation

Suppliers are able to perform a high level of component maturity demonstration

Subsequent turbine durability tests are necessary

Representative turbine operation addresses a-priori unknown failure modes, interactions and interfaces

As turbine tests are generally not accelerated reliability growth is a realistic system validation target

SCADA systems bear a high potential for detection of failure mode precursors

Adaptation of data processing and classification is necessary for monitoring of failure mode evolution

Feed-back from service staff and detailed failure analyses are essential

Abstract

Maturity Check

for Superior Component Reliability Franz Langmayr, Christopher Gray, Nikolaus Haselgruber

Uptime Engineering GmbH, Graz, Austria, [email protected]

PO. ID

141

Component Validation Potential Reliability Improvement Program

Conclusions Durability & Reliability Failure Potential

References

Investigate correlation between failure modes and operation conditions

Derive action plan for failure mode related risk reduction

Combine simulation and measurement to eliminate component risks

Action plan for failure mode investigation Set-up test hierarchy

for each failure mode

Example: Blade

Step-by-step validation

Parallel testing

Supplier contribution

Quantify load conditions – clarify failure physics - measure endurance and load capacity –

define test hierarchy – demonstrate component maturity – perform turbine tests

Promote understanding of failure modes, develop adequate tests

Collect data to characterize duty cycles and durability tests

Evaluate Test efficiency for all relevant failure modes

Develop program for homogeneous high level of validation

Component Maturity Demonstration

Subsystem Component Failure mode Failure location Load Case Simulation Load Case Measurement Load Capacity Assessment

Internal structure

internal laminates debonding

adhesive layer joining

skin and main spar at

pressure side

eigenmode analysis to identify

critical areas

strain measurement for FEA

calibration

HCF testing of blade section -

lifetime curve (Wöhler)

internal laminates debondingsandwich panels - face

to core: main spar web


critical areas


calibration



internal laminates fatigue main spar laminateseigenmode analysis to identify

critical areas


calibration

effect of aging (thermal, UV, ozone) on fatigue

endurance of laminates

internal laminates fatiguemain spar - pressure

side


critical areas


calibration



Lightning protection

tip cables arc formation around receptorheat transfer from conductor to

surroundingselectric power of lightning stroke number/energy of lightning strokes to failure

slip-rings at bearings wear running surfacethermal condition during lightning

stroke

electric power of lightning stroke,

temperature

variation of wear rate with current, temperature

and humidity, investigation of failure mode

C-brushes wear running surfacethermal condition during lightning

stroke


temperature



C-brushes wear running surfacethermal condition during lightning

stroke


temperature



Paint and coatings

gel-coatcracking,

debonding-

blade surface temperature (rotating,

stationary)

UV intensity, blade surface

temperature (rotating, stationary)

exposure to UV, temperature,

Arrhenius lifetime tests

paint aging -blade surface temperature (rotating,

stationary)

UV intensity, blade surface

temperature (rotating, stationary)

exposure to UV, temperature,

Arrhenius lifetime tests

paint erosion leading edgeCFD momentum transfer of particle

stream

particle freight in air (season,

location)

CFD assessment of erosion on uplift,

measurement of erosion effect on power curve

Skins - laminates

fatigue

Skin - sandwich panels -

face to core; skin

laminates


critical areas


calibration



fatigue

leading and trailing edge

adhesive layer, joining

the pressure and the

suction side


critical areas


calibration



fatigueskin and main spar at

pressure side


critical areas


calibration



pollution leading edgeCFD momentum transfer and flow

re-direction, deposition


location)wind tunnel, polluted air, deposition

erosion leading edgeCFD momentum transfer of particle

stream


location)

CFD assessment of erosion on uplift,

measurement of erosion effect on power curve

T-bolt/root inserts

fatiguethreat ground, stud basis

- pressure side

FEA of stress under critical load

superposition


calibrationHCF testing of mounting zone and stud

De-icing system

local overheatingsurrounding of heating

wires / hot air channels

heat transfer from conductor via

surroundings to ice layerheating rate cyclic freezing-de-icing lifetime test

Risk Mitigation - Action Plan - Blade

Preview

IEC I, High Wind;

v = 10 m/s, winter IEC II, Medium Wind;

v = 8,5 m/s, winter Fatigue test

pulsating bending

Failure Mode Fatigue Test IEC II IEC II IEC I Complementary Test

Duration [h] 50 58400 58400 58400

Debonding of

sandwich panels (HCF)18230,0 1,0 1,7 21,2 -

erosion and

deposition of paint

and coating

0,0 1,0 1,0 1,3

wind tunnel test with

deposing and abrasive

materials on blade segments

Debonding of

laminates, shear

forces (HCF)

28,4 1,0 1,8 28,5 -

HCF at suction side 1563292,6 1,0 1,7 1936,8 -

Local overheating

around de-icing

system

0,0 1,0 1,0 1,1cyclic icing de-icing test on

blade segments

Thermal aging of

coating0,0 1,0 1,0 1,1

UV and thermal aging of

blade segments

Thermal aging of

laminate0,0 1,0 1,1 1,1

UV and thermal aging of

laminates

Equivalent Lifetime (normalized)

Certain fatigue failure modes are well

represented by a pulsating bending test.

Complementary durability tests have to be

performed for several other failure modes.

Maturity demonstration can be achieved via

component testing to a high degree.

Full system validation requires subsequent

complementary turbine testing.

Detailed test design is based on duty cycle

data for all future sites and conditions.

Lifetime limiting failure mechanisms are reflected in damage driving operation

modes and boundaries

Physics of failure models quantify the damage effect of load cases and tests

Component testing is specified for fast and cost effective risk reduction

EWEA 2013, Vienna, Austria: Europe’s Premier Wind Energy Event

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Risk Mitigation - Action Plan - Blade - Uptime Engineering · Perform risk mitigation activities in parallel with product development cyclic icing de-icing test on ... Failure statistics