reliability analysis and prediction of wind turbine gearboxes

European Wind Energy Conference 2010, Poland European Wind Energy Conference 2010, Poland

Reliability Analysis and Prediction Reliability Analysis and Prediction

of Wind Turbine Gearboxesof Wind Turbine Gearboxes

K. Smolders, K. Smolders, Hansen Transmissions International

H. Long H. Long (speaker), Durham University

Y. Feng, Y. Feng, Durham University

P. Tavner, P. Tavner, Durham University

European Wind Energy Conference 2010, European Wind Energy Conference 2010, Poland Poland

Outline of the PresentationOutline of the Presentation

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• Field reliability data from public sources;

• Objectives of this study;

• Generic WT gearbox configurations and modular structure;

• Estimation of failure rates of critical components;

• Reliability prediction of generic WT gearboxes.


Field Reliability and Downtime DataField Reliability and Downtime Data

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Recent Reports on Gearbox FailuresRecent Reports on Gearbox Failures• E.ON UK report on the first year of operation of an

offshore wind farm in the UK (2005, 30 turbines):o There were 43 incidences of major unplanned work;o 39 were caused by failures within in the gearbox;

All of these were failures of the bearings; 27 were in the intermediate speed shaft; The remaining 12 were in the high speed shaft.

• Gear tooth failures were reported in 2.5 MW turbines:o 50 turbines were in need of repair and refit in August

2007.

• Design for Reliability to eliminate design faults and to improve operational performance.

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Objectives of this StudyObjectives of this Study

• To develop generic WT gearbox configurations;

• To develop generic and flexible gearbox modular structure;

• To develop reliability block diagrams;

• To estimate failure rates of the critical components;

• To provide quantitative reliability prediction of WT gearboxes at modular level, for different designs;

• To identify reliability critical components in a WT gearbox.

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Gearbox Generic ConfigurationsGearbox Generic Configurations• Two WT configurations are considered: R80 and R100

• Three gearbox designs: GB-R80, GB-R100-S, and GB-R100-A

Characteristics R80 R100

Nominal Power (MW) 1.5~2.0 3.0~5.0

Rotor Diameter (m) 80~90 120~130

Hub Height (m) 60~100 100~120

Rotational Speed (rpm) 10~20 14~15

• GB-R80:GB-R80: 1 planetary stage + 2 parallel stages =Ratio 100Ratio 100

• GB-R100-S: GB-R100-S: 1 planetary (spur) + 1 planetary (helical)=Ratio 35Ratio 35

• GB-R100-A:GB-R100-A: 2 planetary stages + 1 parallel stage =Ratio 126 Ratio 126

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Gearbox Modular StructureGearbox Modular StructureGearbox

Planetary Stage Parallel Stage Housing Lubrication Accessories

Gear (ring, planet, sun)

Spline (sun)

Bearing (planet, planet carrier)

Shaft (planet carrier, planet, sun)

Gear (wheel, pinion)

Bearing (left, right)

Shaft (parallel)

Keyway (wheel, generator)

Torque arm

Joint (bolts, pins)

Oil

Pump

Sealing

Piping

Filter

Cooler

Sensor (oil, temp, particulate)

Sensor

Breather

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Gearbox ConfigurationsGearbox Configurations

LS-SUN

LSS PS

PS

LS-IS

HS-IS

HSS

HSS

HS-ISIS-SUN

IS-PS

IS-PS

LS-SUN

LS-PS

LS-PSLSS

GB-R80GB-R80 GB-R100-AGB-R100-A

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Reliability Block DiagramsReliability Block Diagrams

LS-I parallel HS parallel

Housing Lubrication Accessories

HS-I parallelLS planetary A

A

GB-R80GB-R80

IS planetary HS-I parallel Housing

Lubrication Accessories

LS planetary B

B

GB-R100-SGB-R100-S

C

C

IS planetary HS-I parallel

Housing Lubrication Accessories

HS parallelLS planetary

GB-R100-AGB-R100-A

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Estimation of Failure RatesEstimation of Failure Rates

Components of R80 LS Planetary Module

Failure Rate(failures/year)

Quantity

LSS 0.0025 1

LSS Bearing RS 0.00009 1

LSS Bearing GS 0.00009 1

LS-PS 0.0025 3

LS-PS Bearing 0.00022 3

LS-PS Wheel 0.00017 3

LS Ring Wheel 0.00017 1

LS Sun Pinion 0.00017 1

LS Sun Shaft 0.0025 1

LS Sun Shaft Spline 0.00025 1

Total: 0.01444

• Require data of individual components of each module• Consider R80 LS Planetary Module:

• “Handbook of Reliability Prediction Procedures for Mechanical Equipment”;

• Published by the US Naval Surface Warfare Centre (NSWC07);

• Provided prediction formulae and data sheets for gears, bearings, splines, shafts, ...

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Formulae for Gears and BearingsFormulae for Gears and Bearings

Gears:Gears: GVGTGLGAGPGSBGG CCCCCC,

Considering the base failure rate and multiplication factors (operating speed, loading, misalignment, viscosity of lubricant, temperature, AGMA service factor).

tCWnyBBEBE CCCC, Bearings:Bearings:

Where λBE is the failure rate of the bearing under specific

operation conditions, calculated by using the base failure rate of the bearing λBE,B and the multiplication factors by

considering the applied load Cy, lubricant Cn, water

contamination CCW, and the operating temperature Ct.10


Failure Rates of R80 LS Planetary ModuleFailure Rates of R80 LS Planetary Module

Components of R80 Components of R80

LS Planetary ModuleLS Planetary ModuleFailure RateFailure Rate

(failures/year)(failures/year)QuantityQuantity

LSS 0.0025 1

LSS Bearing RS 0.00009 1

LSS Bearing GS 0.00009 1

LS-PS 0.0025 3

LS-PS Bearing 0.00022 3

LS-PS Wheel 0.00017 3

LS Ring Wheel 0.00017 1

LS Sun Pinion 0.00017 1

LS Sun Shaft 0.0025 1

LS Sun Shaft Spline 0.00025 1

Total: 0.01444

Assumptions: Assumptions: • Constant failure rates

• Base failure rates

• For shafts, keyways, structural components, joints, oils, pumps, sealings, piping, filters, coolers, heaters, sensors and breather:

yearfailuresBG /0025.0, yearfailuresBGS /00025.0,

valueLonbasedBBE 10, 4

yearfailuresothers /0025.0

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Prediction of Failure RatesPrediction of Failure Rates

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Observations of the Predicted ResultsObservations of the Predicted Results• The high speed parallel stage is found to be the most

unreliable module;

• A planetary intermediate speed stage is less reliable than a parallel intermediate speed stage;

• The planetary intermediate speed stage seems less reliable than the planetary low speed stage;

• The lubrication subsystem has an important effect on reliability;

• The housing and the accessories are the least reliability critical components.

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ConclusionsConclusions

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• A reliability prediction method has been developed, based on Reliability Block Diagram and Gearbox Modular Structure;

• Predicted results show that the high speed stage and planetary intermediate speed stage are less reliable;

• Estimation of failure rates at component level is in need of improvement;

• Field failure data through Life Data analysis or Weibull analysis can improve reliability prediction;

• This requires collaborations between end-users, WT manufacturers, gearbox and bearing manufacturers.


AcknowledgementAcknowledgement• Financial support of the EC through the EU FP7

Reliawind, Project No. 212966;

• Reliawind project partners:– SKF;

– Gamesa;

– Alstom Ecotecnia;

– Relex Italy;

– Garrad Hassan;

– ABB OY;

– LM Glasfiber;

– SZTAKI.

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reliability analysis and prediction of wind turbine gearboxes

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