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
eigenmode analysis to identify
critical areas
strain measurement for FEA
calibration
HCF testing of blade section -
lifetime curve (Wöhler)
internal laminates fatigue main spar laminateseigenmode analysis to identify
critical areas
strain measurement for FEA
calibration
effect of aging (thermal, UV, ozone) on fatigue
endurance of laminates
internal laminates fatiguemain spar - pressure
side
eigenmode analysis to identify
critical areas
strain measurement for FEA
calibration
HCF testing of blade section -
lifetime curve (Wöhler)
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
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
electric power of lightning stroke,
temperature
variation of wear rate with current, temperature
and humidity, investigation of failure mode
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
eigenmode analysis to identify
critical areas
strain measurement for FEA
calibration
HCF testing of blade section -
lifetime curve (Wöhler)
fatigue
leading and trailing edge
adhesive layer, joining
the pressure and the
suction side
eigenmode analysis to identify
critical areas
strain measurement for FEA
calibration
HCF testing of blade section -
lifetime curve (Wöhler)
fatigueskin 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)
pollution leading edgeCFD momentum transfer and flow
re-direction, deposition
particle freight in air (season,
location)wind tunnel, polluted air, deposition
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
T-bolt/root inserts
fatiguethreat ground, stud basis
- pressure side
FEA of stress under critical load
superposition
strain measurement for FEA
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